Butterfats Maximise butterfats to boost milk value and income
Maintaining butterfat levels during the grazing season is one of the main challenges facing milk producers. It is a particular issue for spring calving herds, where cows are also hitting peak yield and need to retain sufficient condition for good fertility.
The positive impact of stabilising rumen pH Good rumen function is also critical, with fibre digestion in the rumen impaired whenever rumen pH drops below 5.8. This not only further cuts acetate and butterfat production, but can reduce feed intakes, overall nutrient supply and milk yield, as well as increasing the incidence of health problems such as laminitis. The high levels of rapidly fermentable carbohydrates and sugars in spring grass, combined with low levels of structural fibre, can result in extended periods of low rumen pH. If the rumen drops below pH 5.8 – the threshold for sub-acute ruminal acidosis or SARA – the impact is even greater. Low butterfats are an indicator for SARA at any time of the year, but in the spring, when butterfats are already depressed, it can be harder to spot. Farmers should aim to keep rumen pH as stable as possible and to minimise the time spent below pH 5.8 when fibre digestion is compromised. This can be done by ensuring an adequate forage- to-concentrate ratio in the overall diet, and make sure any buffer feed contains sufficient long fibre to stimulate cudding – to release acid neutralising saliva – and good rumen function.
The main component in milk fat production is the volatile fatty acid acetate, which is produced when dietary fibre is fermented in the rumen. The problem is that although young spring grass provides a great source of both energy – in the form of rapidly fermentable carbohydrates or sugars – and protein, it’s structurally immature. As a result, fibre levels are extremely low compared with older, more mature grass. This limits the amount of acetate produced in the rumen, which in turn reduces butterfat levels. Balancing energy supply Supplying the right amount and type of energy to the cow, irrespective of breed or type is therefore critical if butterfat production is to be supported without adversely affecting milk yields, body condition or fertility. While grazed grass can be low in fibre with high sugar and oil contents, for modern ryegrass swards this can persist right through until late summer, not just during spring when most expect it. Unless properly balanced in the rumen, the rapidly fermentable carbohydrates, together with the higher oil content, can have a negative impact on rumen function and fibre digestion, resulting in depressed butterfat production.
32 | Moist Feed and Forage Specialists
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