Ruminal acidosis and other metabolic disorders in cows grazing fodder beet crops: what do we know so far?

It is important to gradually transition cows onto fodder beet to allow the adaptation of rumen microbes to the high soluble sugar content of the crop to prevent ruminal acidosis and other non-acidosis related disease (e.g., liver dysfunction, chronic inflammation, deferred ketosis). While there is limited information available on the effects of fodder beet on the incidence of ruminal acidosis and other diseases there is increasing farmer interest regarding the health implications of feeding the crop. It is well known that in lactating animals, sub-acute ruminal acidosis (SARA) has production implications and can affect a significant of the herd. While the use of fodder beet during late lactation is increasing, the main period of time that cows are fed fodder beet is during the dry period prior to calving and there is minimal published information about this period.

Feeding fodder beet to non-lactating cows

While the implications of SARA on non-lactating cow performance are not well researched, it has been suggested that the body condition score gain could be affected by SARA. Cows with SARA may have reduced intake and a reduction in nutrient digestion which would affect the available nutrients are body condition gain. It was mentioned in the article by Dalley (2016) that detecting SARA in non-lactating cows is challenging because the best diagnostics appear to be VFA, lactic acid and ammonia concentrations, and rumen pH, all of which are difficult to measure as mentioned in artefact 7. There has been little research on the cause and nature of acidosis induced by fodder beet feeding, however, at DairyNZ in 2015 there were significant differences in the diurnal pattern of rumen pH in cattle offered fodder beet either during lactation or the dry period. As shown in Figure 1, in eight non-lactating cows where rumen pH was being monitored, the pH of three remained in the safe zone, on fell into the risk zone and four dropped into the danger zone.

Figure 1: Diurnal variation in rumen pH in eight non-lactating dairy cows offered a diet of 80% fodder beet and 20% cereal straw (Dalley, 2016).

It was suggested that the cause of the decline in rumen pH when fodder beet is fed is due to the production of lactic acid in the rumen, production of large amounts of weak volatile fatty acids and a failure to produce enough buffering in the rumen through saliva.

Feeding fodder beet to lactating cows

Research conducted at DairyNZ in cows fed fodder beet during late-lactation, offering above 30% of the diet (5.4 kg DM/cow/day) as fodder beet resulted in an increased incidence of acidosis in lactating cows fully transitioned to fodder beet. In the same study, a significant reduction in two amino acids (AA;arginine and citrulline) was observed (Pacheco et al., 2016) when fodder beet was included at higher levels. Recent reviews have proposed that some of the ‘non-essential’ AA play a major role as regulators of metabolism and studies in pregnant sheep have shown that arginine supplementation is associated with increases in birth weight of ewe lambs and foetal fat reserves. Therefore, research assessing the effects of feeding fodder beet to pregnant cows on the development and survival of their calves is needed. The long-term implications of the reduced arginine and other minerals require further study to ensure it is not having negative effects on metabolic processes. It is recommended that for this reason, farmers should err on the side of caution when allocating fodder beet to lactating cows. The impact of fodder beet allocation on calcium, phosphorus, and protein and fibre intake, relative to requirements could also have negative implications that we don’t know about. As shown in Table 2 when feeding fodder beet at greater than 40% of the diet this results in CP content, magnesium and phosphorus levels in the diet being lower than required for the lactating cow.

Table 1: Dry matter (DM), crude protein (CP), neutral detergent fibre (NDF), calcium (Ca), magnesium (Mg) and phosphorus (P) intake of lactating dairy cattle offered increasing proportions of fodder beet in late lactation (Dalley, 2016).

Fodder beet	DMI	Pasture DMI	Fodder beet DMI	CP	NDF		Ca		Mg	P
% of diet	Kg/cow			% DM
0	18	18	0	19.1		45	0.79	0.25		0.34
20	18	14.4	3.6	17.0		39	0.76	0.29		0.30
30	18	12.6	5.4	15.9		36	0.75	0.31		0.28
40	18	10.8	7.2	14.9		33	0.73	0.33		0.26
Lactating cow requirements				16-18		>30	0.6-0.8	0.28		0.3-0.35

Fodder beet has become a really important crop in Southern farming systems and the lack of information available regarding risks associated with feeding fodder beet is a concern for dairy farmers relying on the crop. Therefore, dairy farmers are relying on research organisations such as DairyNZ to fill in research holes about the crop.

REFERENCES

Dalley, D. (2016). The foibles of fodder beet and other forage crops – animal and environmental considerations for successfully feeding forage crops. Proceedings of the SIDE Conference.

Pacheco, D., Waghorn, G. and Dalley, D. (2016). BRIEF COMMUNICATION: Plasma amino acid profiles of lactating dairy cows fed fodder beet and ryegrass diets. Proceedings of the New Zealand Society of Animal Production 76, 62-64.

A review: Physiological parameters to diagnose sub-acute ruminal acidosis in dairy cows

Ruminal acidosis is a bovine disease that occurs when there is a build-up of lactic acid in the rumen resulting in a decrease in rumen pH (Underwood, 1992). A build-up of lactic acid occurs when dietary carbohydrates are rapidly fermented in the rumen. This is typically a result of a diet with readily soluble carbohydrate content such as concentrates typically fed in housed cows overseas (Palizier et al., 2008) however; anecdotal evidence indicates that the recent uptake of grazing fodder beet in New Zealand has resulted in cows experiencing ruminal acidosis. Ruminal acidosis can be prevented by gradually transitioning cows onto the feed which allows the rumen microflora to adjust (Kleen et al., 2003) as well as feeding an adequate level of fibre in the diet to encourage rumination (Nocek, 1997). While appropriate management of cows grazing feed high in readily soluble carbohydrates is the best defence against rumen acidosis (Kleen et al., 2003), sub-acute acidosis is difficult to detect and clinical acidosis can be life-threatening. Due to the diet causing a decrease in ruminal pH it has been suggested that it may be possible to diagnose SARA by randomly sub-sampling the herd and measuring ruminal pH (Morgante et al., 2009). Sub-acute ruminal acidosis is indicated by a ruminal pH of 5.0-5.5 (Nocek, 1997; Kleen et al., 2003). The symptoms include decreased dry matter intake, reduced milk fat, diarrhoea, and loss of body condition (Nocek, 1997; Kleen et al., 2003; Palizier et al., 2008). Many cases of SARA may not be detected, as the current field diagnosis of SARA is not clearly defined and depend on ruminal pH measurements which are invasive, costly and are primarily suited for research purposes (Palizier et al., 2008). Therefore, measuring ruminal pH is not a practical tool for farmers to diagnose SARA related illness (Danscher et al., 2015). Various physiological parameters have been investigated to diagnose SARA however; the results have been conflicting (Enemark et al., 2004; Palizier et al., 2008; Morgante et al., 2009; Li et al., 2012; Danscher et al., 2015). The purpose of this review is to identify the physiological parameters that have been investigated to date and which of these are likely to be most accurate and practical for use on farm.

Faecal pH

Danscher et al. (2015) investigated the effects of SARA on the physiological parameters, blood, faeces and urine. In the study by Danscher et al. (2015) faecal pH was lower in cows with SARA. This is in agreement with the study by Morgante et al., (2009) however, conflicts with the results by Li et al. (2012) and Enemark et al. (2004) who showed no effect of SARA on faecal pH. Danscher et al. (2015) suggested that high soluble carbohydrate content in the diet could result in carbohydrates bypassing rumen fermentation, with subsequent increased fermentation and volatile fatty acid production in the hindgut explaining the reduction in faecal pH (Morgante et al., 2009; Danscher et al., 2015). Therefore, the discrepancy between studies in the relationship between SARA and faecal pH could be explained by differences in diet composition and therefore, faecal pH may not be an accurate predictor of SARA (Li et al., 2012).

Urine pH

In agreement with Gianesella et al. (2010), Danscher et al. (2015) also found that cows with SARA had lower urine pH than control cows. However, this is in disagreement with the study by Morgante et al. (2009) and Rouche et al. (2005) who reported no change in urine pH associated with SARA. Biologically, the effect of SARA on urine pH shown by Gianesella et al. (2010) and Danscher et al. 2015 can be explained as a response to decreased dietary cation-anion difference in cows with SARA which results in high blood acidity stimulating acid secretion by the kidneys and a subsequent decrease in urine pH (Danscher et al., 2015). As supported by Enemark et al. (2004), Morgante et al. (2009) described this as a difference in dietary composition and therefore, concluded that urinary pH was not suitable for predicting low ruminal pH due to the lack of a consistent relationship between the two.

Although there was an association between SARA and decreased faecal and urinary pH in the study by Danscher et al. (2015), the decreases were small and it is doubtful whether these decreases were large enough to be of diagnostic value. The conflicting results from previous studies also emphasises the issues associated with using these physiological parameters as indicators of SARA under field conditions (Enermark et al., 2004; Rouche et al., 2005; Morgante et al., 2009; Gianesella et al., 2010; Li et al., 2012; Danscher et al., 2015). More research is needed to determine if physiological parameters could be suitable indicators of SARA. However, it could be argued that the feeding situation influences the physiological parameters and therefore, the usefulness of physiological parameters to detect SARA would need to be tested under conditions similar to those experienced when grazing fodder beet, if these indicators were to have a practical application.

REFERENCES

Danscher, A. M., Shucon, L. Andersen, P. H., Khafipour, E. Kristense, N. B. and Plaizier, J. C. (2015). Indicators of induced subacute ruminal acidosis (SARA) in Danish Holstein cows. Acta Veterinari Scandinavica 57, 39-53.

Enemark, J., Jorgensen, R. and Kristensen, N. (2004). An evaluation of parameters for the detection of subclinical rumen acidosis in dairy herds. Veterinary Research Communications 28, 687-709.

Gianesella, M., Morgante, M. Cannizzo, C. Stefani, A. Dalvit, P. and Messina, V. (2010). Subacute ruminal acidosis and evaluation of blood gas analysis in dairy cow. Veterinary Medicine International, 1-4.

Kleen, J. L., Hooije, G. A., and Rehage, J. (2003). Subacute ruminal acidosis (SARA): a review. Journal of Veterinary Medicine, A, Physiology, pathology, clinical medicine, 50, 406-414.

Li, S., Gozho, G. N., Gakhar, N., Khafipour, E., Krause, D. O. and Plaizier, J. C. (2012). Evaluation of diagnostic measure for subacute ruminal acidosis in dairy cows. Canadian Journal of Animal Science 92, 353-364.

Morgante, M., Gianesella, M., Casella, S., Ravarotto, L., Stelletta, C. and Giudice, E. (2009). Blood gas analyses, ruminal and blood pH, urine and faecal pH in dairy cows during subacute ruminal acidosis. Comparative Clinical Pathology 18, 229-232.

Nocek, J. E. (1997). Bovine acidosis: implications of laminitis. Journal of Dairy Science 80, 1005-1028.

Plaizier, J., Keunen, D. O., Gozho, G. N. and McBride, B. W. (2008). Subacute ruminal acidosis in dairy cows: the physiological causes, incidence and consequences. Veterinary Journal 176, 21-31.

Underwood, W. J. (1992) Rumen lactic acidosis. Part I. Epidemiology and pathophysiology. Compendium on continuing education for the practising veterinarians 14, 1127-1133.

Interview with Kevin Lawrence

Following on from the last blog summary where I identified that some farmers have had great success with feeding fodder beet and others had faced large fatalities I wanted to talk to some industry experts about whether they considered the deaths to have been completely avoidable or that misleading information is available regarding the management of the crop.

On the 17^th July 2016 I met with Kevin Lawrence. Kevin Lawrence is a Senior Lecturer in Pastoral Livestock Health at Massey University. I spoke with Kevin Lawrence about his experience with feeding Fodder Beet following issues in the 2014 season. Dairy cows from Massey University’s No. 1 Dairy farm were winter grazed on fodder beet at Keebles. During the wintering period there were several fatalities on the crop. Kevin Lawrence identified poor management to have been the cause of death on the crop and said “the deaths were completely avoidable”. Firstly, Kevin identified that there was an issue with crop allocation. Because there was not enough room on the crop for all cows to graze simultaneously this resulted in some cows eating more than their allocated amount while others missed out. He identified this as a management issue that caused cows to gorge themselves on the crop and rumen acidosis resulting followed by death of the cow. He suggested that cows should never be fed hungry and supplementary feed should be fed before the fodder beet allocation. He also suggested the use of a headland to reduce competition and allow all cows to graze at once, reducing the potential for cows to over-eat. An additional recommendation which was carried out at Keebles was to allocate the crop perpendicular to the direction of the rows that the crop is sown as shown in Figure 1.

Figure 1: Recommended fodder beet break fencing alignment. Perpendicular to the rows of sown fodder beet as indicated by the two red lines.

Secondly, the biggest loss of animals was as a result of flooding where the cows were taken off the crop for a period of several days and then placed straight back onto the crop. He suggested that under these circumstances the cows should be “re-introduced” back on the crop, rather than allocating the same amount as when they were removed from the crop. Additionally, for these circumstances as well as transitioning cows onto the crop Kevin suggested developing a method for farms to detect when cows have transitioned using something that can be easily tested such as faeces, urine or milk.

Summary of the blogs to date

The purpose of this blog is to summarise some key findings to date and discuss the findings from a farmer survey I conducted. The survey involved three case study farms that had positive results from fodder beet grazing. The purpose of this was to compare the management of these case study farms with published information. Based on the information available I have made the assumption that misleading information would be a major cause of cow deaths associated with grazing fodder beet so finding out how farmers are managing fodder beet successfully was a good starting point to help explain where some confusion has arisen.

DairyNZ recommends a 14-21 day transition period where animals start on 2 kg DM/cow/day alongside pasture, silage and/or straw whereas Gibbs recommends a transition period of 10-14 days. Interestingly, none of the case study farms used the transition periods recommended. All three case study farms began transitioning during late lactation and transition periods were between 24 – 30 days with starting intakes between 1-1.5 kg DM/cow/day with an increase in crop allocation of no more than 0.5 kg DM/cow/day. All farms were supplementing with straw and silage. None of the farms had suffered fatalities during the transition period. Based on farmer experience and financially speaking, if the transition period can be increased it is better to have a slightly slower transition than a faster one. It has been emphasised that the cows vary in the rate that they adapt to a new feed type and the amount they can eat. Therefore, moving too quickly can result in cow deaths. Assuming an average herd size of 419 cows where 2 kg DM/cow/day of maize silage at 25 c/kg DM is supplemented during an additional 7 days of transition. This would cost approx. $1500 and taking into consideration the cost of a mature aged cow, it is not difficult to see the advantage of transitioning for a slightly longer period of time if it reduces the incidence of acidosis. Based on this information I would recommend that cows should be transitioned for a minimum of 24 days with a maximum starting intake of 2 kg DM/cow/day and increasing at no more than 0.5 kg DM/cow/day. Transitioning cows during the late lactation period also seems to prevent the desire to transition cows too quickly and results in cows being already partially adapted to the crop at drying off.

All three farms analysed their crops before feeding and again halfway through the season to determine dry matter yields and nutritive values. They then used this information and calculated areas required for allocation of the crop. Farmers have reported issues with allocation of the crop due to inaccurate predictions of yields and nutritive values. This is due to a limited number of credible animal feedings studies and is therefore, an area that requires further investigation. One case study farmer also mentioned that higher yielding crops were more difficult to feed due to the large dry matter yield or a small area. He said that a long face is critical which is in agreement with recommendations from DairyNZ however, still struggled to manage the crop for this reason. I could only recommend that using some under the wire feeding might be a way to help combat the issue of over-allocation in a high yielding crop.

DairyNZ recommended offering additional supplementary feed prior to allocation of the crop during the transition period to ensure the gut is full to minimise health risks. Two of the case study farms continued this management practice throughout the wintering period. If it is not too impractical, it would be sensible to continue this management practice outside of the transition period to encourage cows to eat the supplementary feed and prevent cows from missing out.

All three case study farms reported mild cases of acidosis however, were able to manage this by taking the cows that didn’t adapt to the crop off the crop and wintering those animals on pasture. One farm suffered fatalities however; this was due to a staff member feeding more than recommended and was completely avoidable. No farms reported an increased incidence in milk fever however, all farms supplemented with mineral licks or dicalcium phosphate over silage to account for mineral imbalances in fodder beet. It is worth noting that these farms also fed silage which would provide some minerals in addition, and by feeding the silage prior to the crop this would also help ensure that the cows are accessing the dicalcium phosphate supplement. I would therefore, support the management practice of feeding silage before allocating the crop throughout the entire transition and wintering period.

So in conclusion, the recommendations in addition to those published in literature are:

-         Begin transitioning cows during late lactation to prevent the desire to transition cows too quickly if possible. This can be achieved using a cut and carry method where cows are fed fodder beet in addition to pasture.

-          Transition for a minimum of 24 days with a starting intake of a maximum of 2 kg DM/cow/day and increasing at no more than 0.5 kg DM/cow/day. A slightly longer transition will allow all cows to sufficiently adapt to the new feed and may save money long term.

-          Feed supplements prior to allocating fodder beet throughout the entire transition and wintering period to minimise the possibility of animals overeating, lack of fibre in the diet and mineral imbalances.

-          Use under the wire feeding where there are large crop yields to avoid over-allocation.

-          Winter cows on pasture if they don’t adapt to the crop.

These recommendations are based on information in literature and from farmer experience that have been successful with the crop to date. I’m hoping to this follow up with experiences from farmers that have had large numbers of fatalities, to try and narrow down the reasons these fatalities have occurred. I’m interested to see whether the deaths were completely avoidable or the farmers have been received misleading information in regards to the management of the crop.

Velvetleaf Outbreak in New Zealand

Velvetleaf has been found in fodder beet crops across 60 farms nationwide with Southland, Otago and Canterbury the worst affected regions according to MPI (April 2016). The outbreak of velvetleaf has been linked to the imported fodder beet seed varieties, kyros and bangor (NZFarmer, 1 April 2016a). This has sparked a nationwide investigation from MPI and this blog will address what farmers should be aware of in relation to velvetleaf.

What is velvetleaf?

Common names: Velvetleaf, China jute, Butter print, Indian mallow

Scientific name: Abutilon theophrasti

Velvetleaf is an annual broad-leaved herb that grows between 1 and 2.5m tall. It has yellow flowers about 3cm in diameter and these flowers are present from spring through autumn (MPI, April 2016). The leaves are large and heart-shaped and velvety to the touch. The plant has distinctive seedpods with 12-15 segments in a cup-like ring. The seeds can survive for up to 50 years in soil and can germinate in large number in cultivated areas such as field crops (MPI, March 2016). Velvet leaf is native to south Asia and has become a weed in parts of North America, Europe and Australia. Velvet leaf has been in New Zealand since 1948 however, until recently the prevalence of velvet leaf has been minimal (MPI, March 2016). In February 2016, velvetleaf was found on a small number of farms in the South Island and since then, it has been found on several other properties throughout the North and South Island.

Why is velvetleaf a threat to New Zealand agriculture?

Velvetleaf was made an unwanted organism in December 2012 (MPI, March 2016). It is a potential threat to agriculture and is one of the worst broadleaf weeds of maize and soya bean crops in the USA. The worst case scenario for New Zealand farmers would be if it found its way into maize crops (NZFarmer, 1 April 2016a). It has the ponteitlay to remove up to 70% of a crop’s yield (FarmerNZ, 29 March 2016).

What to do if you find velvetleaf on your property?

All farmers who have planted fodder beet seed should check their crops carefully  and regularly for signs of velvetleaf with particular concern for farmers that have planted Kyros and Bangor varieites.

If you find velvetleaf on your property, contact MPI on 0800 80 99 66

Do not pull the plant out. MPI will arrange the removal of the plants.

The fact sheet below provides a guide to biosecurity management of velvetleaf to help control the spread of this pest. Farmers should not remove any plants or allow stock to graze infeted crops. This could spread the seed DairyNZ (2016).

What action is being taken?

Ministry for Primary Industries is working with partner organisations to manage velvetleaf. Their aim is to find it, contain it, and safely remove any plants found. Therefore, it is important that farmers report the weed if it is found on their property.

Velvetleaf in the media

• In 2015 New Zealand imported just under 300 tonnes of fodder beet seed from a range of countries, including Australia, Italy, Denmark, France and other European countries (NZFarmer, 1 April 2016b).
• As of 29 March 2016 velvetleaf has been found in 125 hectares of farmland in Manawatu-Whanganui (NZFarmer, 29 March 2016). The Horizons Regional Council staff have found 252 plants so far across Whanganui, Ruapehu and Horowhenua districts.
•  The government have banned lines of fodder beet seeds grown in Italy and pelleted in Denmark in response to the velvetleaf infestation (NZFarmer, 20 April 2016). Imported consignments will now also required a sign-off by one of the Ministry’s two chief technical officers before they can be released, and all pelleted seed imports will be lab-tested for contaminants.
• More than 105 properties in Canterbury have been found to have velvetleaf as of 20 April 2016.
• Environment Southland and MPI committed to a search and destroy activity in Southland resulting in an investigation of 270 farms as of the 26 April 2016. The search found 189 velvetleaf plants on about 40 farms (NZFarmer, 26 April 2016).

      Velvetleaf Management

REFERENCES

DairyNZ (2016). Velvetleaf. DairyNZ Ltd. Retrieved from http://www.dairynz.co.nz/feed/pasture-management/pests-and-weeds/velvetleaf/

MPI (March 2016). Velvetleaf. Ministry for Primary Industries. Retrieved from http://www.biosecurity.govt.nz/pests/velvet-leaf

MPI (18 April 2016). Velvetleaf. Ministry for Primary Industries. Retrieved from http://www.mpi.govt.nz/protection-and-response/responding/alerts/velvetleaf/

NZFarmer (29 March 2016). Velvetleaf found in 125 hectares of Manawatu-Whanganui farmland. NZFarmer. Retrieved from http://www.stuff.co.nz/business/farming/78352847/velvetleaf-found-in-125-hectares-of-manawatuwhanganui-farmland

NZFarmer (1 April 2016a). Environment Southland describe velvetleaf outbreak as region’s ‘fruit fly’. NZFarmer. Retrieved from http://www.stuff.co.nz/business/farming/78449520/Environment-Southland-describe-velvetleaf-outbreak-as-regions-fruit-fly

NZFarmer (1 April 2016b). Velvetleaf, one of world’s worst weeds, confirmed on three Waikato farms. NZFarmer. Retrieved from http://www.stuff.co.nz/business/farming/agribusiness/78135127/velvetleaf-one-of-worlds-worst-weeds-confirmed-on-three-waikato-farms

NZFarmer (20 April 2016). New Zealand bolstering biosecurity in response to Southland velvetleaf outbreak. NZFarmer. Retrieved from http://www.stuff.co.nz/business/farming/79120571/new-zealand-bolstering-biosecurity-in-response-to-southland-velvetleaf-outbreak

NZFarmer (26 April, 2016). Velvetleaf search to end at the end of this week. NZFarmer. Retrieved from http://www.stuff.co.nz/business/farming/cropping/79315105/velvetleaf-search-to-end-at-the-end-of-this-week.html

Farmer Survey: Wintering on Fodder Beet

While there is little known about grazing fodder beet in New Zealand based on scientific literature, there appears to be some information based on farmer experience. However, accessing this information is difficult because as far as I know a survey has never been undertaken in New Zealand to collect anecdotal evidence and information from farmers in regards to the management of fodder beet. If we can identify how farmers are currently managing fodder beet and link that to any issues they have had with the crop, this could help us to identify the areas that require more research and need more information to help understand what may be causing particular problems.

I have created a survey that can be found here. If you are a New Zealand farmer feeding fodder beet and would like to contribute to this survey, please fill out the form and either post or email the form to me as outlined in the document. I will have a summary of my findings available towards the end of April.

"More fodder beet safer than less"

The publication from the Rural News Group "more fodder beet safer than less" outlines the benefits and some risks associated with grazing fodder beet. This gives an idea of the some of the issues known from research and anecdotal evidence regarding the grazing of fodder beet. It also outlines some conflicting information published in Dairy NZ News, (June, 2015) that requires further investigation. The publication from the Farmers Weekly "can't beet it" also conflicts with some of the information outlined in the Rural New Group (2015, July 10) publication.

Credit: Country Wide (2014).

The article states that 'Dairy NZ advice to limit dairy cows to 8 kg DM/head/day of fodder beet is right in the the danger zone' (Jim Gibbs, Lincoln University). Jim Gibbs says limiting intake at that level is highly dangerous because if cows gain access to much more than that, they will eat enough to 'crash' the rumen through acidosis. He stated that a safer approach is to transition cows to a point where they are at or close to ad-lib intakes of fodder beet. Then, should a breakout or serious mis-allocation of feed occur the cows won't eat more than they have been adapted to. "If cows are fed 8 kg DM/day, if they get out they'll easily eat 12 kg but if they're already eating 12 kg/day it's not a problem," he explains. However, according to the farmfact published by Dairy NZ Ltd (2013), the Dairy NZ example suggests cows should be fed 8 kg DM fodder beet to achieve an increase in body condition score (BCS) during the winter of 0.5 BCS units, in addition to feeding 4-5 kg DM other feed (s). The information explained by Jim Gibbs, if cows are fed at or close to ad-lib intakes of fodder beet this will prevent cows from overeating fodder beet if a breakout or misallocation of feed should occur, is actually in agreement with the Dairy NZ example where cows are consuming a total intake of 12.0 kg DM/cow however, it is simply offered in the form of two or more feeds rather than feeding fodder beet alone and therefore, it also a suitable recommendation that shouldn't result in acidosis. More information regarding the management of fodder beet and prevention of acidosis can be found here. The article released from Dairy NZ urging farmers to take care when feeding fodder beet to their dairy herds can be found here. Alternatively, a summary of this article can be found in the blog post here.

Gibbs explained that DairyNZ's June 2 advisory warning against ad-lib fodder beet feeding and to limit intake to 8 kg DM/ha/day plus 4-5 kg DM/day of other feed was unnecessary. However, in the article published from the Farmer's Weekly (Country Wide, 2014) documents Gibbs stated that feeding fodder beet with supplements during the transition period is critical to slowly introduce cows to the fodder beet which is in agreement with the transitioning recommendation published by Dairy NZ Ltd (June, 2015). Gibbs continued on to state "by feeding too much fodder beet too soon puts cows at risk of developing rumen acidosis but once they are over this transition period they can be fed as much as they can eat without any health concern".

While Dairy NZ's senior scientist, Dawn Dalley, acknowledged that there are many experienced fodder beet users succeeding with ad-lib regimes she defended Gibbs recommendation, arguing that where cows are only on beet for 50-60 days over winter during the dry period, the 30 days required to safely transition cows to an ad-lib regime is too long and therefore, cows should remain on a diet of no more than 70% fodder beet and the rest supplementary feed. But Gibbs says the need for such long transitions and high supplement rates is not supported by the experimental data or hundreds of farm experience which shows a 14-day transition is adequate. 

Both scientists have drawn valid conclusions however, the different management strategies may be dependent on the farm system e.g. beef finishing (long-term grazing) vs. dairy winter grazing (short-term grazing, 50-60 days). Both articles agree that patience over the transition period is critical because transitioning cows too quickly can be fatal. Therefore, the recommendations made by Gibbs although valid may not be suitable for wintering dairy cows due to the short grazing period which may encourage farmers to 'rush' the transition. As a result, Dairy NZ recommends to feed fodder beet alongside a fibrous supplementary feed rather than increasing the incidence of acidosis if cows are transitioned too quickly. 

The article continued to explain the findings of the paper presented by Gibbs at the New Zealand Society of Animal Production conference which can be found here. Alternatively, a summary of this paper can be found in the blog post here.

REFERENCES

Country Wide (2014). Can't beet it. Country Wide 2. Retrieved from https://farmersweekly.co.nz/article/cant-beet-it?p=71

Dairy NZ Ltd. (May, 2013). Fodder beet - feeding to dairy cows (1-73). Dairy NZ Farmfacts. Retrived from http://www.dairynz.co.nz/media/253800/1-73_Fodder-beet_feeding_to_dairy_cows.pdf

Dairy NZ Ltd. (June, 2015). Caution urged over fodder beet intake. Dairy NZ News. Retrieved from http://www.dairynz.co.nz/news/latest-news/caution-urged-over-fodder-beet-intake/

Prendergast, S. L. and Gibbs, S. J. (2015). A comparison of microbial protein synthesis in beef steers fed ab libitum winter ryegrass or fodder beet. Proceedings of the New Zealand Society of Animal Production 75, 251-256.

Rural News Group (2015, July 10). More fodder beet safer than less. Dairy News. Retrieved from http://www.ruralnewsgroup.co.nz/dairy-news/dairy-general-news/more-fodder-beet-safer-than-less

"Caution Urged Over Fodder Beet Intake"

An article published by Dairy NZ News urged farmers to take care when feeding fodder beet. This pre-caution was released in response to increased anecdotal evidence that dairy cows were becoming ill or dying when being fed fodder beet. Scientist Jim Gibbs was not in agreement with this advisory warning and advised that farmers can feed fodder beet at quantities larger than 8 kg DM/cow/day in his paper Gibbs, (2011).

The article published by Dairy NZ explains that while fodder beet is an excellent source of metabolisable energy, there is a concern that some cows are being over-allocated fodder beet. Dr Jane Kay reported that farmers have been offering cows unlimited access to fodder beet however, due to the high concentration of water soluble carbohydrates, fodder beet should not be fed ad-lib. "The high sugar content can result in an increase in lactic acid production in the cows rumen which can cause acidosis," says Dr Waghorn. More information regarding acidosis in cows fed fodder beet can be found in here.

The article states that a transitioning stage for introducing cows to fodder beet is critical to ensure that cow health and nutritional value of fodder beet are optimised. This is in agreement with the article published by Rural News Group, (2015, July 10) however, while Gibbs recommended a transition period of 10-14 days the article published by Dairy NZ Ltd, (June, 2015) recommended transitioning over 14-21 days. Dairy NZ's recommendations for transitioning cows onto fodder beet can be found here. It was also recommended by Dairy NZ Ltd, that cows should not be fed high levels of fodder beet in the diet (> 70%). Dr Waghorn stated that "cows vary in the rate that they adapt to a new feed type and in the amount that they can eat. Move too quickly or feed them too much and you will kill some of them". In agreement with this statement, ancedotal evidence from farmers John and Rachel suggests that not all cows transition well to the diet and therefore, animals that aren't coping with the crops are dropped out and wintered on grass (Country Wide, 2014).

In addition to transitioning cows properly Dr Waghon said that it was critical to ensure that cows were also offered a long fibre source in the diet in the form of silage, hay or straw before feeding the fodder beet, to slow down their intake of fodder beet and thereby prevent acidosis. This is about 8 kg DM/cow/day in fodder beet, and 4-5 kg DM/cow/day of other feed(s). To prevent over-allocation of the fodder beet it is recommended that the farmer accurately measures crop yield so that feed allocation is accurate within each break.

REFERENCES

Country Wide (2014). Can't beet it. Country Wide 2. Retrieved from https://farmersweekly.co.nz/article/cant-beet-it?p=71

Dairy NZ Ltd. (June, 2015). Caution urged over fodder beet intake. Dairy NZ News. Retrieved from http://www.dairynz.co.nz/news/latest-news/caution-urged-over-fodder-beet-intake/

Gibbs, S. J. (2011). Wintering dairy cows on fodder beet. Conference Proceedings of the South Island Dairy Event. Lincoln, E.d. Lincoln University.

Rural News Group (2015, July 10). More fodder beet safer than less. Dairy News. Retrieved from http://www.ruralnewsgroup.co.nz/dairy-news/dairy-general-news/more-fodder-beet-safer-than-less

Management guidelines for wintering on fodder beet

Several journal articles and conference proceedings are available that document studies and provide anecdotal evidence regarding the management of fodder beet in beef and dairy cattle. The findings of these articles are summarised below. Alternatively the DairyNZ, (2013) has released a farmfact for fodder beet management that summarises the fodder beet management guidelines that can be found here.

INTRODUCTION

Fodder beet has been grown in New Zealand for over 100 years, however, before agronomical advances fodder beet was a high maintenance crop that was difficult to manage and susceptible to weed invasion (Gibbs and Saldias, 2014). In the last 10 years the area sown with fodder beet in New Zealand has rapidly increased for use as a winter feed for dairy cows (Gibbs and Saldias, 2014). This increased use is a result of improvements in agronomy as well as advances in feeding the crop (Gibbs and Saldias, 2014). The current system commonly used in New Zealand where animals graze fodder beet while supplementing the diet with a fibre source, in comparison to the cut and carry method used in Europe, has been developed in the last five years at Lincoln University by Gibbs and Saldias, 2014. Because New Zealand is almost the only country to graze fodder beet as a sole feed including the leaves and bulbs, there is limited information regarding expected nutritive values, crop management and potential animal health risks associated with grazing the crop (Gibbs, 2011; Gibbs and Saldias, 2014).

NUTRITIVE VALUE

Dairy NZ commissioned a specific research project to establish the information needed regarding nutritive values of grazed fodder beet. Results demonstrated that within cultivars large differences (e.g. > 50%) in bulb dry matter existed between large and small bulbs, at different times in the winter. This has implications when it comes to allocation of the crop (Gibbs, 2011). As a result of this, it is recommended that fodder beet crop yields are estimated for individual paddocks at least twice during the season to account for the high variability (Gibbs, 2011). A trial was conducted using dry cattle fed fresh fodder beet and a fibre supplement for 21 days, with total faecal and urine collections undertaken to determine the digestibility of the feed. The digestibility values demonstrated that the fodder beet cultivars were of a similar digestibility to high quality ryegrass, suggesting ME values within the range of 12-13 MJ ME/kg DM (Gibbs, 2011). When considering ME values it is important to consider how these values are derived. Note that metabolisable energy of a feed is calculated by subtracting the energy lost in faeces (feed not digested), the energy lost in urine and the energy lost as methane during digestion from the gross (total) energy of the feed as shown in Figure 1. 

Figure 1: Partitioning of dietary energy

Therefore, to determine the metabolisable energy of a feed, the digestibility value of the feed is required. Digestibility can be measured using the method explained above by collecting and weighing the inputs and outputs from an animal when fed a particular feed (Gibbs, 2011). Digestibility of a feed can be measured in a laboratory environment however, these results must be compared to known digestibility values measured in animal experiments to determine an accurate estimation of metabolisable energy for a particular feed. The accuracy of a metabolisable energy estimation will determined by the numbers of animal studies that the laboratory digestibility values can be compared with (Gibbs, 2011). Therefore, because the feeding trial and reference samples available for fodder beet, fed as a leaf to bulb ratio of 1:4, were non-existent at the time, DairyNZ established the feeding trial mentioned above to establish the feeding value of fodder beet and develop reference standards to measure digestibility and subsequently metabolisable energy. The accuracy of predicting fodder meet feeding values will only improve if a credible number and range of background samples for fodder beet are tested in animal feeding studies (Gibbs, 2011). In summary, the established reference values for composition and energy content of fodder beet on New Zealand dairy farms by large scale sampling across regions, seasons and cultivars are summarised in the table below alongside other commonly fed winter crops.

Table 1: Nutrient concentrations of fodder beet (adapted from Dairy NZ, 2013).

	DM %	CP %	NDF %	WSC g/kg DM	MJ ME/kg DM	Phosphorus %	Calcium %
Fodder beet (average)	14-20	9-14	11-16	500-700	12-12.5	-	-
Beet leaves (tops)	12-13	19-23	30	100-120	11.0	0.2-0.3	0.8-1.3
Beet roots (Low DM)	10-13	9-11	13-15	650	11.8-131	0.1-0.2	0.1-0.2
Beet roots (High DM)	15-20	10	11	700	12.2-131	0.1-0.2	0.1-0.2

SUPPLEMENTING THE CROP

Fodder beet is a feed high in metabolisable energy with a high water soluble carbohydrate concentration resulting in a large quantity of rapidly digested sugar and a low fibre content (Table 1). This energy source is rapidly converted to volatile fatty acids in the rumen resulting in a decrease in rumen pH (increases acidity). In addition, the lack of fibre reduces the rumination time of the feed due to a faster passage rate through the rumen. This subsequently reduces chewing and decreases the saliva (bicarbonate) production, which normally buffers rumen acidity (Nagaraja and Titgemeyer, 2007). This can lead to clinical acidosis and is an issue commonly observed in other brassica crops such as kale. It is well established in feeding kale that this risk can be managed by adding 25-40% roughage to the crop diet and gradually adapting the cows to the crop (Nichol et al., 2003). However, this had not been established for feeding fodder beet and therefore, a trial was undertaken to investigate what level of supplement was required for good cow health and rumen function. The study indicated that fodder beet consistently and significantly reduced the rumen pH however, when a fibrous supplement was maintained above about 35% of the diet, this effect on rumen pH was reduced and appeared to have no impact on intake or cow health (Gibbs, 2011). The study by Gibbs, (2011) indicated that during the early winter period, supplement inputs were necessary for stable rumen function. However, as the period of time grazing fodder beet was extended past 100 days, the supplement inputs could be reduced to <20% of the total diet without impacting dry matter intake, rumen function or animal health (Gibbs, 2011).

Fodder beet crops on average are typically low in crude protein however, the leaf material has a moderate crude protein content (19-23% CP) in comparison to the low crude content of the bulb (10-12% CP) (DairyNZ, 2013). If the roots and crop are grazed together this can help overcome the crude protein deficiency in the roots (DairyNZ, 2013). For a wintering cow, a minimum crude protein content of approximately 12% DM is required. If the total crude protein concentration of fodder beet is lower than 12%, this can restrict microbial growth in the rumen resulting in marginal rumen function (Gibbs, 2011). Therefore, should the fodder beet crude protein concentration be too low, it is important that the supplement fed also provides dietary crude protein (e.g. grass silage). In addition to low crude protein contents, fodder beet has notably low concentrations of the minerals phosphorus and calcium as presented in Table 1 (Gibbs, 2011). A value of below 0.24% for phosphorus and 0.27% for calcium is considered deficient for a dairy cow in late gestation (Gibbs, 2011). A typical fodder beet crop of 1:4 leaf to bulb ratio, fed at 8 kg DM/day would provide 18 g/day for phosphorus and 29 g/day for calcium (calculations presented below).

Calculations:

6.4 kg DM bulbs x 2 g P/kg DM = 12.8 g

1.6 kg DM leaf x 3 g P/kg DM = 4.8 g

6.4 kg DM bulbs x 2 g Ca/kg DM = 12.8 g

1.6 kg DM leaf x 10 g Ca/kg DM = 16.0 g

The phosphorus intake is below recommended levels and the calcium intake is marginal. The feeding standards (ARC, 1980) recommended for a dairy cow in late gestation, a minimum phosphorus intake of 20 g/day is required with calcium provided at a ratio of 1.5:1 with phosphorus. This gives a recommended calcium intake of 30 g/kg DM. To provide adequate levels of phosphorus and calcium the fodder beet diet can be supplemented an additional feed. For example, a typical fodder beet crop of 1:4 leaf to bulb ratio, fed at 8 kg DM/day with a supplement of 4 kg DM/day grass silage (P = 0.30 % DM, Ca = 0.80 % DM), this is a maximum P intake of 30 g/day and Ca intake of 61 g/day (calculations presented below). 

4 kg DM grass silage x 3 g P/kg DM = 12 g

4 kg DM grass silage x 8 g Ca/kg DM = 32 g

It is important to know the mineral concentrations of the individual crop and take into account the leaf to bulb ratio when grazing fodder beet and managing potential mineral deficiencies. There is limited information available regarding potential P deficiency issues associated with grazing fodder beet. However, it is also important to be aware that excessive phosphorus concentrations can contribute to milk fever because phosphorus is a mineral that interferes with the hormones required for calcium absorption in the small intestine. It is unknown how the relationship between a phosphorus deficiency and adequate calcium in some fodder beet crops may contribute to milk fever in early lactation. However, there is anecdotal evidence that suggests there is a correlation between the incidence of milk fever and feeding fodder beet. It has been suggested from farmer experience that this can be overcome by supplementing dicalcium phosphate (50 g/cow/day) as a slurry on the supplement to prevent milk fever, particularly when straw is fed as a supplement (low phosphorus).

FEEDING THE CROP

Fodder beet is a 'careful' winter feed (Gibbs, 2011). Fodder beet is a high energy feed and as a result crop allocation and transitioning on to the crop is more challenging compared with other brassica crops (Gibbs, 2011). Lincoln University in conjunction with Dairy NZ have developed successful and practical transition guidelines for fodder beet (Gibbs and Saldias, 2014). The transition period is the most important period of feeding fodder beet and must be managed appropriately to minimise the incidence of rumen acidosis (Gibbs and Saldias, 2014). The first 14 days of transition onto the fodder beet crop set up the animal for the winter and allow the rumen microbes to adapt to the change in diet (Gibbs and Saldias, 2014). Cows must be transitioned on to fodder beet in the same manner as other brassica crops by feeding 2 kg DM per cow per day alongside pasture and/or silage and gradually increasing the allocation, allowing a transition period of 10-14 days (DairyNZ, 2013). It is recommended that cows are offered 1-2 kg DM of crop on the first day (1-2 hours grazing) after being well fed on a forage such as silage, baleage, hay and/or pasture. Ensure sufficient silage and/or pasture and straw is available during the transition period to meet cow energy requirements in addition to the fodder beet fed (DairyNZ, 2013). There are various NZ opinions insisting on a requirement for high (40%) supplement inputs to fodder beet crop use after transition however, these views are not draw from research with fodder beet and do no represent the current industry approach (Gibbs and Saldias, 2014). After transition, supplement inputs of between 25-30% are adequate to provide dietary fibre and in some cases protein and/or minerals however, more is not required and not recommended as this will immediately increase winter feed costs and may result in substitution of supplement for crop (Gibbs and Saldias, 2014).

In addition to correctly transitioning cows onto fodder beet, the allocation of fodder beet can be challenging. It is recommended that a headland of 6 m is left in the front of the paddock to allow space for the first breaks and to prevent soil damage (Gibbs and Saldias, 2014). This can be achieved by planting the front of the paddock with an annual grass or by harvesting the front part of the paddock. Fodder beet is a high yielding crop and as a result a 30 t DM/ha crop has 3 kg DM every square metre, which is the day 1 allocation for three cows during the transition period (Gibbs and Saldias, 2014). Therefore, the daily break allocated to the cows will not more far each day. It is recommended that a crop yield assessment is undertaken within the area to be grazed during the transition period and for the whole crop to avoid over-allocating the crop. It is recommended that long narrow breaks are offered twice daily with some feeding under the wire to optimise crop allocation (DairyNZ, 2013). This promotes steady mixed consumption of roots and tops whilst maximising simultaneous access by cows and minimising crop wastage. It is important that the herd can access the crop simultaneously to avoid cows receiving more or less than the allocated amount. There are no specific requirements for the transitioning of cows off the crop

CONCLUSIONS

Fodder beet has clear advantages as a wintering feed in the New Zealand dairy industry. It can provide a large quantity of high quality feed at a low cost. However, due to its challenging management it is important that farmers take caution when feeding the crop. Provided that the crop is managed appropriately, fodder beet is a valuable crop that could be incorporated into the pasture renewal programme and has major advantages over commonly used brassicas such as swedes and kale. It is important to note that there is no other national that has developed grazing fodder beet and therefore, the growth of fodder beet use is being driven by farmer interest (Gibbs and Saldias, 2014). There is still a lot of information regarding the grazing of fodder beet that is unknown. In particular, it is unknown how the relationship between a phosphorus deficiency and adequate calcium in some fodder beet crops may contribute to milk fever in early lactation (Gibbs and Saldias, 2014).  Further research is required regarding how the physiological systems involved in calcium absorption, deposition and release from bones, are affected when phosphorus is deficient and calcium is adequate in the diet.

ACRONYMS

CP = Crude protein
DMI = Dry matter intake
MJ ME = Megajoules of metabolisable energy
N = Nitrogen
NDF = Neutral detergent fibre
WSC = Water soluble carbohydrates

REFERENCES

Agricultural Research Council, (1980). The Nutrient Requirements of Ruminant Livestock. Commonwealth Agricultural Bureaux, Farnham Royal.

Dairy NZ Ltd. (May, 2013). Fodder beet - feeding to dairy cows (1-73). Dairy NZ Farmfacts. Retrieved from http://www.dairynz.co.nz/media/253800/1-73_Fodder-beet_feeding_to_dairy_cows.pdf

Gibbs, S. J. (2011). Wintering dairy cows on fodder beet. Conference Proceedings of the South Island Dairy Event. Lincoln, E.d. Lincoln University.

Gibbs, S. J. and Saldias, B. (2014). Fodder beet in the New Zealand dairy industry. Conference Proceedings of the South Island Dairy Event. Invercargill, Ed. Lincoln University.

Nagaraja, T. G. and Titgemeyer, E. C. (2007). Ruminal Acidosis in Beef Cattle: The Current Microbiological and Nutritional Outlook. Journal of Dairy Science 90, E17-E38.

Nichol, W., Westwood, C., Dumbleton, A. and Amyes, J. (2003). Brassica wintering for dairy cows: overcoming the challenges. Proceedings of the South Island Dairy Event (SIDE), 154-172.