There is an opportunity with increasing dairy prices to maximise returns by maintaining milk yields as high as economically possible after peak, with diets based around home grown feeds (pasture, other forages, crops). Maintaining intakes of feeds with high Metabolisable Energy (ME) levels are key to sustaining milk yields and body condition, which may be difficult with declines in pasture growth and quality during summer. Therefore, supplementary feeding may need to be considered.
Palm kernel expeller meal (PKE) has tended to be the supplement of choice, due to its historically low price relative to other supplements. The Metabolisable Energy (ME) in PKE is derived from its fibre and fat contents.
Balance is a key aspect of nutrition, with the best production responses associated with a balanced supply of dietary nutrients (sugars, starches, fibre, fats, nitrogen/protein, minerals, vitamins) to cows and their rumen microbes. Rumen microbes convert carbohydrates (sugar, starch, fibre) to volatile fatty acids (acetate, propionate, butyrate), which in turn influence milk yield and composition. Supplementing with high sugar and starch supplements tends to increase milk protein levels in milk, whereas high fibre feeds tend to promote milk fat levels.
Declining milk protein levels in early to mid-lactation may indicate a shortage of energy, and would correspond with rapid loss of body condition. It may not be possible to recover either milk or protein yields if energy intakes are limited over several weeks.
Some starch, e.g. in maize grain, may not be digested post ruminally, and drive milk yield directly. Specific types of protected fats promote milk yield as well as helping maintain body condition by sparing mobilisation of fat reserves. Increasing Metabolisable Protein (MP) supply in early lactation can increase feed intakes and milk yields.
Major (calcium, phosphorous, potassium, sodium, chlorine, sulphur) and trace (cobalt, copper, iodine, iron, manganese, selenium, zinc) minerals are important in all metabolic functions, so sub-clinical shortages or imbalances may result in lower milk yields, health and fertility. Shortages can be due to low levels in feeds, or due to reduced availability due to interactions with other minerals. Organically bound trace minerals have been shown to be more available in the presence of such antagonists.
Anti-nutritional factors such as mycotoxins may reduce feed intakes and nutrient availability. Avoiding feeding mouldy feeds, and in some cases feeding combination product mycotoxin binders may be necessary.
As featured in NZ Dairy Farmer