IMPROVING ON-FARM MARGINS THROUGH BETTER RUMEN FUNCTION FOR MORE MILK SOLIDS


With forage stocks tight, and additional bought-in feeds to make up the shortfall adding significantly to costs for most herds this winter, on-farm margins are undoubtedly under pressure. The opportunity to lift milk income by improving rumen function to drive feed efficiency and milk solids production is therefore something few dairy herds can afford to ignore. “We all know that rumen fermentation is the foundation on which


dairy cow feeding is built,” explains Dr Derek McIlmoyle, AB Vista’s EMEA Ruminant Technical Director. “The threat when forage is in short supply is that rations end up less well balanced and rumen function less well supported as a result, with knock-on effects for production and cow body condition.”


Supporting milk production One of the growing challenges facing milk producers is that modern Holstein Friesians are genetically programmed to produce large volumes of milk regardless of whether adequate rations are provided. Any failure to provide a properly formulated diet will both reduce milk output and force the cow to draw on valuable body reserves in an effort to maintain production. “With herds bred for higher yields over the last decade or two, it’s


no longer a case of cutting back the feed if forage is tight and cows then happily producing less milk,” Dr McIlmoyle continues. “These cows are driven to produce milk, and the impact of not fully supporting their nutrient requirements will not only be a short term reduction in yields and milk quality, but also long term negative effects on lactation performance, fertility and longevity.” Ensuring the ration is correctly balanced to optimise the rumen –


and so maximise the nutrients extracted from both home-grown and bought-in feeds – is therefore critical. For example, issues such as sub-acute ruminal acidosis (SARA) can lead to significant losses in terms of both milk yield (up to 2.7 kg/cow/day) and quality.


Stabilising rumen pH According to Dr McIlmoyle, what’s needed is a feeding strategy that balances energy release in the rumen, and so limits the dramatic rumen pH drop associated with high intakes of starchy concentrates. It also needs to promote the production of milk fat pre-cursors to ensure the cow is supplied with the energy and raw materials needed to support butterfat production in the udder. “The aim is to provide as stable a rumen pH as possible, optimising


fibre breakdown in the rumen by minimising the time spent below pH 5.8, when microbial activity and fibre digestion are compromised,” he


PAGE 28 JANUARY/FEBRUARY 2019 FEED COMPOUNDER


explains. “This maximises production of the volatile fatty acid (VFA) acetate, which is an important pre-cursor for milk fat production.” The overall diet must also balance both the amount and rate


of energy and protein release in the rumen, correctly matching the nutrient supply of bought-in concentrates to the nutrients contained within home-grown feeds. “The inclusion of rapidly fermentable energy in particular – primarily


sugars and starch – is important in balancing the rumen degradable protein in grass silage, for example. Rumen-protected or rumen-bypass fats are also worth considering to help increase the energy density of rations without negatively impacting rumen conditions and fermentation efficiency.”


Promoting acetate production The diet should also include a good supply of energy from digestible fibre, using feeds such as sugar beet feed and soya hulls. This will have an additional buffering effect on rumen pH by promoting production of acetate and butyrate. “Even those relying on compound feed in the parlour to supplement


grass silage can switch to a concentrate based more heavily on digestible fibre, rather than starch,” Dr McIlmoyle continues. “However, in all cases the concentrate must be of high quality, with good palatability to encourage full intake of the nutrients needed to balance forage in the rumen. “The addition of a slow-release rumen conditioner or a metabolically


active yeast may also be worthwhile. This can help reduce the rate and extent of any rumen pH drop, and so minimise the negative impact on rumen fermentation efficiency.” According to research into optimising rumen function in lactating


dairy cows, including a rumen conditioner in addition to a yeast produced gains that exceeded those of the yeast alone. The result was a substantial improvement in rumen pH, volatile fatty acid (VFA) production and butterfat yield, and a 3% advantage in fat-corrected milk (FCM) production per kg of dry matter intake (DMI).


Research proven benefits The detailed study, which was carried out at Schothorst Feed Research (SFR) in the Netherlands, used a small group of fistulated Holstein Friesians fed a 65:35 forage-to-concentrate ratio of a partial total mixed ration (TMR) consisting of grass silage, maize silage and a wheat- based concentrate being fed in the parlour. This diet was fed either unsupplemented (control), with the addition of a metabolically active live yeast (Vistacell at 4g/cow/day) or a combination product (Vistacell


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