Cargill’s ruminant specialist in the north of England and Scotland, Donald Macleod, is warning farmers that new grass following recent rainfall could impact milk fat.
“The long dry spell has resulted in a low average grass cover for the time of year, and when the rain comes and the grass starts to grow, cows are likely to hoover it up while it is in a very immature stage,” he said. “These lower covers with immature grass in its first leave stage have 20% more oil content than mature grasses and this can be the cause of milk fat depression.”
Young grass, which is more typical of spring and early summer, has a high oil content that is 50% richer in unsaturated fats. Its structural fibre is also low, with sugar and digestible fibre high. This can reduce the rumen pH, creating acidic conditions.
“The combination of the acidic conditions and the high oil content in fresh grass creates a ‘perfect storm’ in the cow’s rumen and disrupts the normal pathways used by the cow to produce milk fat,” explained Mr Macleod.
Half of the milk fat is imported into the udder from dietary oil and cow’s body reserves, with the other half manufactured from the acids produced from forage and concentrate fermentation. Under these conditions, where cows are eating young grass, dietary oil is converted to conjugated linoleic acid (CLA), which disputes fat production.
“Ideally, we should avoid grazing these pastures and wait for the grass to mature to its third leaf stage. But under current conditions where grass growth has been stalled this may not be possible.”
Practical solutions include altering the nutrient content of the buffer and concentrate feeds, including a ramen buffer to target milk fat depression.
“Equaliser Cream is a good example,” he added. “It has a two-pronged approach, by working as a buffer in maintaining rumen pH. Equaliser has a buffering capacity that’s more than double that of sodium bicarbonate and it also reduces CLA production by normalising the oil conversion pathways. This treats the problem before it happens and is more effective, both in terms of performance and cost, compared to using C16 fats that treated the problem after it happened.”
Results from ten farms showed an uplift in milk fat of 0.31% in seven days, and 0.52% in a month. The financial benefit to the farmer was seen within a month.
“With most payment schemes based on milk solids, a drop in milk fat represents a significant reduction in milk income, and more so as some contracts move towards higher prices for milk fat,” concluded Mr Macleod. “Adjusting the ration and including a bespoke rumen buffer that is proven to help promote milk fat in challenging situations will give a good return on investment.”