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.
