On a recent trip to Canada visiting dairy farms the first thing that struck me was the quantity of milk solids produced by their high yielding herds. I thought this warranted further investigation. As you are all aware the Canadian dairy industry operates a quota system based on butterfat production, but in addition there is a stipulation that a minimum differential between fat and protein must be maintained. Diets are based on corn silage and high levels of starch which means that proteins are high (3.3-3.45). This then necessitates having a butterfat consistently over 4%. At lower levels of production these levels of solid are quite mediocre but at yields of over 10500kg/cow it takes some doing. So what is so different and how do they achieve it?
My hypothesis revolves around the types of forage, the varieties and how they are preserved.
Firstly, there is very little perennial rye grasses grown or fed in Canada. Perennial rye grasses are bred for high yields of energy per hectare and disease resistance. This has led to the production of varieties high in oil. The oil boosts energy levels and disease resistance is improved by having very waxy leaves. Unsaturated fatty acids (UFA) present in perennial rye-grass and silage will reduce butterfat levels in dairy cows. Canadian cows are fed on grasses with lower oil contents such as fescues and orchard grass. Although these grasses are lower in energy than perennial rye-grass they are of higher feeding value than untreated straw. They offer both structure and a form of fermentable fibre which produces the acetic acid required for fat synthesis.
High lactic acid silage is another feed that you do not see in Canada. Corn silages are dryer, grasses are made into hay and Lucerne does not produce a very high lactic acid fermentation. Forage fermentation produces a lot of 4 carbon VFA’s such as Lactic acid which drives milk volume. On high starch diets, there are also an abundance of C4 VFA’s produced in the form of propionate. What we really need for fat synthesis is acetate, a 2 carbon VFA, and a reduction in the levels of UFA in the diet.
How do we go about achieving this type of diet?
- Make dryer silages with a less extensive lactic acid fermentation.
- Do we need to consider returning to acid treatment of grass silage?
- Use hay or NIS as a source of fermentable fibre
- Reduce the levels of feeds high in UFA
- Long term select grass species or varieties lower in oil
With the UK moving towards continental European type milk contracts, the requirement to achieve high milk components is going to be more important in the future.