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Using Brassica crops as livestock feeds

Using Brassica crops as livestock feeds

Crops from the Brassica family have been used in feeding livestock, especially in the cooler regions of Kenya, which experience surplus in their production. They have also been utilized in seasons when perennial livestock feeds are low, because of their high production of high digestible forage. Some of the brassica crop family includes kales, cabbages, cauliflower, rape and radish. The livestock species mainly fed on brassica forage are dairy cattle, rabbits and sheep. Well, they are of high quality nutrients and are easily digestible but they come along with challenges when used as livestock feed; thus the need to know how best they can be utilized.

Brassica family forage can be utilized in three ways; can be grazed on, harvest and carry for green chops in zero grazed animals or can be ensiled if in surplus amounts.

In grazing, a plan is necessary if animals are to best utilize the forage material. Introduce animals to brassica pastures slowly rumen microbes to adjust effectively and allow them to graze for only short periods of time. At this time of grazing, monitor the animals for any adverse reactions to prevent health issues that may arise. Avoid immediate change of grazing from dry pastures to lush brassica fields. At this point, the animals are ‘hungry’ for fresh pastures and what you think is feeding animals on greener pastures may turn out sour. In harvest and carry system of feeding, you have control to amounts and time to feed. Provide reasonable amounts at a time so that animals maintain an intake level. Providing in excess makes the animals reduce intake due to high moisture content. This method of utilizing brassicas is the best because ensiling is not very effective while grazing is associated with high wastage resulting from animal trampling on them. In excess production, some farmers have tried to ensile brassica forage to use in future feeding. However, brassica crop family is difficult to ensile because of their high water content. If ensiling is a must for you, then mix with chopped hay or forage straws. In spite of this, seepage problems may still occur.

Nutrient composition of brassicas

Brassicas are utilized by animals depending on the level of maturity at harvest. They are highly digestible but have low fibre content. It is because of this reason that brassica crops should not be fed much. In ideal situations, brassica crops should not make up more than 75 percent of the total animal feed. Limit lactating dairy cows to about 30 percent of the total brassica forage fed to them to minimize chances of rumen acidosis occurring. The forage is also very high in calcium composition, due to this; regulate the amount of brassica forage you feed to in calf cows’ nearing calving and shortly after calving. When calcium levels are in excess before calving, it makes it difficult for the cow to mobilize calcium stored. During this period, supplement brassica forage with feed low in calcium like grass hay and straws. Before maturity, brassicas have high moisture content, enough to cause challenges when fed. As the crops increase maturity, their dry matter digestibility also increases. Ruminants like dairy cows, need enough dry matter and fibre for proper rumen activity. In fact, brassicas should be fed as concentrates rather than forage since they provide high quality forage with highly digestible energy, considerable protein amounts and are low in fibre content. Due to their high moisture content and low fibre content, supplement brassicas with dry hay for a more balanced diet in order to balance the total dry matter intake while availing some fibre. This will increase saliva production, reduce nutritional disorders, stabilize gut function and improve animal performance in general.

Feeding disorders

Feeding animals on brassicas should be dependent on proper planning. Brassicas are known for digestive upsets, poisoning among other disorders if not managed well. Some disorders include bloat, pneumonia, nitrate poisoning. Bloat can be prevented by ensuring that the dairy animal is full before supplementing them with brassica forage. Bloat has also been known to contribute to high deaths in rabbits, to reduce this, wilt the forage material in the sun before bringing feeding them. Brassica forage is high in sugars by nature, and can lead to rumen acidosis. They also have an amino acid compound that accumulate in them and cause haemolytic anaemia and goiter in livestock. If the two are to be prevented, feed brassicas and supplement with iodine, iron and copper to meet the dietary requirements of dairy cattle. Grazing on brassica crops too early before maturity can also cause photosensitization especially in young sheep. These are costly to treat or may cause deaths in acute cases. A component of brassica crops called glucosinolates also cause milk taint in dairy animals.

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