Depending on farming region and subsequent climatic conditions crop choices will vary. It is important to seek professional assistance if you are looking to put in a seasonal crop to ensure that the variety and timing is suited to your specific area.
Forage brassicas and fodder beet are both sown as supplementary feed for animals. The two are different species although often treated similarly by farmers. In cooler regions the key requirement is for high yielding crops such as swedes and kale, or fodder beet, that provide maintenance feed from small areas of the farm. This enables pasture covers to recover over winter and respond in spring to provide the high quality forage required.
These crops are commonly sown to provide high quality feed during periods when pasture growth or quality is poor, such as winter and mid-summer. One advantage, when done well, is the ability to produce a high DM yield off a small area of the farm. Brassicas are also grown in summer in some areas to avoid potential health risks associated with pasture such as facial eczema and ryegrass staggers.
These forage crops encompass a wide range of different plant forms including bulb (turnips and swedes); leafy (rape); swollen stem (marrow stem kale); and long stem (kale). These all have different fits within the farm system.
Deer are fed all types of brassica crops depending which fit best into the farm system, however very little research has been reported from these forages. The different brassica species are introduced briefly below.
Fodder beet (FB) is a forage crop that has been used in Europe for stock feed since the Middle Ages. However, only recently were NZ farmers the first to begin using the crop as a grazed primary feed, as internationally it was always considered toxic above a very low intake level.
Deer farmers have been the earliest adopters of grazing fodder beet (FB) since it was reintroduced to the NZ market in the last fifteen years. Wintering hinds and stags on FB has been common in Southland, Otago and South Canterbury. In recent years there has also been a renewed interest in using FB to maximise weaner growth rates across the short day period. However, unlike the dairy and beef/sheep sectors, there has been very little formal research into optimal use of FB in deer systems, and much of the available information has been acquired by industry trial and error. This is a fact sheet on the current best practice use of FB in the deer industry of NZ.
The use of fodder beet has been increasingly adopted in the dairy industry due to the ability to grow a high yielding crop on a small area. Increasingly deer farmers are also utilising fodder beet with varied success.
Fodder beet is not related to the winter brassicas but to sugar beet and beetroot. The agronomic requirements to ensure a high yield include correct soil fertility, ground preparation, an early sowing date and intensive weed control in the early life of the crop.
Although farmers report very high yields, commonly yields range between 18-20 t DM/ha. Approximately 75-80% of the DM yield is bulb. This is important when estimating yield and allocating feed. In addition, fodder beet has low crude protein levels (6-7%), lower fibre and high soluble sugar levels. To balance the diet of ruminants including deer a high quality supplement (baleage or lucerne silage) should be used to provide fibre and some of the protein that may be required.
The transition to a fodder beet diet is longer (14-21 days) that that required for brassicas or lucerne (7-10 days) and more care is required. As the leaf is a small proportion of the yield it is not feasible to rely on this to help balance the diet. The recommendation for dairy cows is that fodder beet supplies less than 2/3 of the diet with the rest as supplement. The recommendations for deer have yet to be fully tested but should be similar to dairy cows in the first instance. Anecdotally farmers have found that after 60 days the performance of deer wintered on fodder beet can drop off and may be due to low protein or calcium in the diet. More on Fodder Beet here
The crop is a spring sown bi-annual that produces a large bulb of approximately 75-80% of the total dry matter (DM) mass of the plant. The bulb is a DM of 6-30% depending on the cultivar, has low protein content (6-10%), low fibre content (<20%), very low mineral content and a high sugar content (40-70%). The leaf material is typically 11-14% DM, with a protein content of approximately 15-20%, a fibre content of 30-40% and holds most of the calcium and phosphorus of the plant. The calcium content of the total plant (bulb + leaf) is usually always adequate (>0.45% of the DM mass), but the phosphorus content is always low (<0.24%), and in certain regions (eg Canterbury) it is often very low (0.06-0.1%). Inadequate phosphorus eventually results in reduced intake rates and reduced weight gains.
Fodder beet is very digestible (>80%) so provides a high metabolisable energy content (12 MJ/ kg DM) to ruminants, higher than any other crop. In general terms, it has a high utilisation (>90%) because it is very palatable, does not reduce in palatability after being removed from the ground, and encourages a different intake pattern where stock tend to stay on a single plant until finished and then move on, rather than walking through the crop.
The crop can be grazed from March until it concludes at seeding (400d - October-December), without any problems. Best practice agronomy will typically produce dryland crops of 20t DM/ ha or above, and irrigated crops are usually above 25t DM/ ha. Yields are critically dependent on agronomic expertise, which is not always present for FB, and there is plenty of poor advice available. Note there is a robust relationship between yields achieved and the cost per ha - better agronomy is associated with lower per ha costs and higher yields. In 2014, best practice FB agronomy resulted in per ha costs of $1700-2100/ ha for 22-30t DM and above, which is a cost per kg DM produced starting at 6c. Poor agronomy can grow you 17t/ ha at $2300/ ha and that is 13.5c/ kg DM – you have just doubled your feed bill. If your agronomist is telling you that 20t/ ha is unrealistic, and $2300+ / ha is normal, contact us and we will get you a new, capable FB agronomist. Their contribution to profitability cannot be overstated.
The crop can also be harvested in autumn or in spring and kept for use as a silage replacer. Stacked in uncovered windrows, it can be kept for 4-5 months, and fed out through a conventional silage wagon on pasture. It does not need to be chopped - a left over European convention that costs money and contributes nothing to deer eating it. Currently the cost of best practice harvesting and transport is 5c/ kg DM.
Most deer wintering operations start stock on FB in May, and conclude with the spring grass arrival. Breaks of several days to a week are most common, and supplement inputs besides FB are typically low (<1kg/d), though some operations preferentially feed palatable silages such as lucerne to increase this proportion to 1/3 of the diet. Deer can be run without supplements, however production on this system is usually poor as the stock will reduce intakes in the absence of a fibre source.
While utilisation of many FB cultivars with deer is high (>90%), it is lower than cattle achieve as the bulb is routinely eaten without removal from the ground, leaving a stump, except for the upright mangel types such as ‘Brigadier’. There are clear preferences for certain cultivars, and this is not a function of the DM% (ie. hardness) of the bulb, but of the palatability of the plant, and this changes utilisation, as well as upper intake levels. The mangel types are routinely found to be more palatable, as are the very hard sugar beet types (harvested), while some mid DM cultivars are known to be ‘sour’ and take longer to adapt to.
Unlike cattle, deer rarely suffer rumen acidosis from overeating FB at introduction to the crop. As a result, transition to the crop is rapid, and often practically is simply running them on and off the crop for a few hours on a few days, then locking them on. It does take approximately a week for deer to achieve full FB intakes, and once adapted will almost always eat it readily. There are no issues with teeth on FB crops for deer, and even the hardest bulbs available in NZ (‘Suga’: 30% DM) can be readily eaten without disadvantage. The only exception to this is in older stags, where broken mouths can limit FB intakes on harder varieties. However, in general deer will take more readily and quickly to softer, palatable FB cultivars that have greater leaf mass, and the mangel type cultivar ‘Brigadier’ has the dominant market share in these systems.
Accelerated finishing using FB in young stock has been found successful, but some operators who have used FB for some years report a clear 60d winter window of profitable daily gain, then a slump in intakes. It is difficult to assess if this is a standard winter feeding response in weaners at present as there is no research on the use of FB in weaners to give baseline liveweight gains. Also, some weaners in the reports have been started on FB in May, others in late June, so any short day intake effects are hard to tease out with the information available to date. As low phosphorus does reduce intakes in other ruminants, it may be a cause in some areas, given the known inadequacy of FB phosphorus in some regions, and the low supplement inputs sometimes used. If low phosphorus intakes are involved, mitigation is straightforward with the use of dusted DCP on feed several times a week, or increased silage intakes.
Weaners typically are given weekly or twice weekly breaks of FB with good quality grass or lucerne silage at levels between 10 and 30% of the diet. The transition to FB is identical to that for older stock described above. They can be slower than older stock to take to the bulbs, so opening up an area (eg. tractor wheel) can speed this up in the initial stages. While there is no firm research on the requirement for supplemental protein in weaners growing at high (>100g/ day) rates on FB, it is likely that in common with other ruminants the protein content of the supplement used for young stock is required to be at or above that of the FB itself (average 10-13%). Weaners are routinely supplemented with trace elements while on FB, but as FB does not hold nematode larvae they are typically drenched before transition and no further treatment is required until returning to pasture.
Acidosis is not a feature of deer in FB systems, and is rarely seen. Unlike cattle, there is a minimal requirement for fibre, even at transition, for normal animal health. Nil supplement systems will, however, have lower intakes and therefore lower liveweight gains.
Wintering and weaner stocking rates are high (50-100/ha), so faecal borne bacterial diseases like Yersiniosis, Salmonellosis and Johnes should be expected to have increased transmission opportunity in the wet conditions, but to date this has not been reported. Typically, the high plane of nutrition made possible with FB mitigates this increased challenge.
There is no evidence to suggest that trace element (copper, selenium, iodine, zinc) deficiencies are induced by winter FB feeding in adult deer, compared with any alternative feeds. In cattle, there is a typical decrease in selenium, but not the other trace elements, across a 60 day winter, suggesting that deer may also benefit from pre-winter selenium supplementation. Soil ingestion in FB systems is high, but in no species has there been any evidence that this reduces trace element status, and it is unlikely to do so in deer.
Fodder beet grazing systems for ruminants are a genuine Kiwi innovation developed here in the South Island, and nowhere else in the world uses the crop in this manner. The crop is a high energy feed of high yield potential that makes it the cheapest source of ME supply in NZ after pasture, and is available for grazing from March to November. It is readily eaten by all stock classes of deer, and so has developed a role in both wintering adult stock and accelerating finishing of young stock which can only grow with greater industry familiarity with the crop. Unlike cattle, transition to FB is straightforward and without the risk of overfeeding. There are no significant animal health concerns specific to FB with deer. At present there is a lack of specific deer research on basic nutrition, production and operation of FB systems in NZ, and it is likely that further uses of the crop will be opened up for the deer industry when this work is undertaken.
These are the most common winter brassica crops, potentially yielding 10-20 T DM/ha. Swedes are sown between November to early December, either ridged in cool areas, or conventionally drilled to provide specialist winter feed. Higher sowing rates lead to thinner and more palatable stems.
Kales are winter active and mainly used as a "winter feed". Kale can provide high dry matter/ hectare yields however for best results kale requires high soil fertility and good soil moisture.
Kale is suitable for cattle, sheep, and deer but the taller or giant types are best used for only cattle grazing, while the shorter, leafier cultivars are more suited to sheep and deer.
Ruminant animals take some time to attain maximum voluntary intake when presented with a change of diet, an effect dictated by the population of microflora within the rumen. When the diet of a ruminant changes dramatically, from high to low fibre, or low to high feed quality and vice versa, rumen microbes must likewise adapt to the new conditions. The time this takes will vary depending on what type of brassica is being introduced, the cultivar and the stock type grazing the crop.
To limit the effects of diet change stock should be gradually adapted to the new crop by using a runoff paddock of pasture for 7 days or more, ensuring that the diet is only partly brassica based. Ensuring animals are relatively full when first introduced to the crop will reduce issue of over eating causing problems.