| 2014-08-13 |    |
Exploiting Milk Contracts this Coming Season
“Are your cows receiving the most appropriate energy source to fully exploit your milk contract” asks Volac nutritionist, Dr Richard Kirkland, from Dungannon.
At this stage of the season, grass growth rates in some regions of the UK have declined to 60 kg DM/ha/day or below, limiting energy availability from grazing. At the same time, milk composition is under scrutiny as some processors alter their payment schemes to put further emphasis on milk components, in particular milk fat. The challenge for farmers is to ensure the energy and nutritional requirements of the animals are met while producing milk of desired compositional quality to exploit specific milk contracts.
Dr Richard Kirkland
Late season pasture is characterised by increasing fibre content, falling sugars and a reduction in energy concentration, indicating that both amount of concentrate offered and composition are key factors to consider. Studies at the Agri-Food and Biosciences Institute (AFBI), Hillsborough evaluated the effect of offering high starch or high fibre concentrates, at two feeding levels, to spring calving cows in mid-late season - Table 1. Milk fat % was lowest when starchy concentrates were offered, while milk protein showed the opposite response.
Table 1
Effect of high fibre and high starch supplements
on dry matter (DM) intake and milk production
Concentrate feed level (kg DM/day) |
||||
5 |
10 |
|||
Concentrate type |
Fibre |
Starch |
Fibre |
Starch |
Grazing intake (kg DM/day) |
11.4 |
11.9 |
9.4 |
9.3 |
Total DM intake (kg DM/day) |
16.4 |
16.9 |
19.3 |
19.3 |
Milk yield (kg) |
30.2 |
28.8 |
31.9 |
33.6 |
Milk fat (%) |
4.10 |
3.93 |
3.50 |
3.09 |
Milk protein (%) |
3.29 |
3.43 |
3.29 |
3.51 |
Sayers et al. (2003); AFBI, Hillsborough
The Hillsborough results demonstrate the ability to modify milk components by nutrition, though changing either the diet’s ingredients or its physical form can induce marked changes in milk fat % - Table 2.
Table 2
Dietary factors affecting milk fat %
Increase milk fat % |
Decrease milk fat % |
Increase fibre |
Reduce fibre |
Low grain / low starch |
High grain / high starch |
Long fibre |
Finely-chopped forages |
Cracked or coarse-rolled grains |
Ground cereals |
Small frequent concentrate feeding e.g. TMR or out of parlour feeders |
Large, infrequent concentrate feeds e.g. twice a day in parlour |
Megalac rumen protected fat or ‘high-C16’ fats. |
Rumen-active fat supplements - vegetable oil, fish oil, high-oil by-product feeds e.g. brewers grains |
With limited energy supply from grass and cereal prices well down on recent years, it may be tempting to feed additional starchy cereals to make up the energy shortfall. It is important to consider how this may affect milk fat % if this is an important factor in the milk contract, as well as the increased risk of acidosis associated with ‘fizzy’ high starch diets.
Energy supply can be increased using rumen-protected fats and 59% of farmers surveyed at the Livestock Event stated this was their primary reason for using a fat supplement. In contrast, only 35% associated feeding a fat with increasing milk fat production. Milk fat comes from three sources:
-
Diet fat - supplies approx. 50% of milk fat
-
Fat synthesised from products of rumen fermentation
-
Mobilised body fat
Research indicates a requirement of 6-8% fat in the diet DM for high yielding cows, though type of fat offered must also be considered. Adding vegetable or fish oils, or high oil ingredients such as brewers grains, can lead to a sharp fall in milk fat %, so it’s important to ensure that fat supplements used are rumen-protected – in other words they pass through the rumen for digestion in the lower digestive tract, avoiding any negative effects on fibre digestion – though only around half of farmers surveyed were aware of the benefits of rumen-protected fats. The ‘high-C16’ fats have been particularly associated with increased milk fat %, but use should consider cost-benefits and energy supply implications on herd performance. Volac’s Megafat is a unique product designed to specifically increase milk fat % while also stimulating milk yield and fertility.
With the pressures of seasonal and milk contract changes it’s important to review what dietary and management options are available to ensure individual herds are performing at their optimal level.
