How to optimise the cow’s full potential

24 February 2011

All cows require optimal feeding and management if they are to express their potential efficiently, says Volac’s ruminant nutritionist, Dr Richard Kirkland. What’s more, high yielding animals need Formula 1 standard attention – high quality inputs together with continual monitoring for signs of malfunction. Acidosis, lameness, ketosis, fatty liver and displaced abomasum are among the most common disorders, but the incidence and extent of these conditions can be reduced by adopting the following action points.

Acidosis

For optimal rumen function, rumen pH must be maintained well above 6.0. However, feeding high levels of rapidly fermented cereals at the expense of fibre, as typically occurs during early lactation to achieve higher energy intakes, causes rumen pH to plummet. As pH falls - the rumen becomes more acidic – the population of fibre-digesting bacteria falls while that of lactic acid bacteria increases, leading to further reductions in rumen pH. These conditions reduce rumen activity, leading to a depression in fibre digestion, appetite and performance.  

Key actions : Ensure the diet contains adequate fibre - the coarse roughage essential to illicit the ‘scratch’ factor in the rumen to stimulate salivation and neutralise acid. Target a minimum neutral detergent fibre (NDF) of 28 to 30% in the ration dry matter (DM) with 20% of the DM as forage NDF. The proportion of ‘fizzy’ energy sources should be reduced and replaced with less fermentable ingredients; Megalac rumen-protected fat contains 2.5 times the energy concentration of typical cereals and is not fermented in the rumen, so can be used to help reduce the rumen acid load while maintaining or increasing energy density.

Lameness

Up to 25% of the herd can be lame at any one time. The average cost of a case of lameness in dairy cows is £172 and is accompanied by a reduction in milk yield of 390 litres through the lactation. Findings from the University of Liverpool have also demonstrated a major reduction in herd fertility due to lameness, with lame cows taking over 40 extra days to get back in calf compared to healthy herd mates.

Recent data from the Agri-Food and Biosciences Institute, Hillsborough, Northern Ireland, have highlighted housing factors related to increased lameness – overstocking, uncomfortable cubicles and dirty passageways; contaminated slurry is one of the major risk factors for digital dermatitis. Nutritionally, there is a well-established link between lameness and diet; rapidly fermentable, starch-rich rations lead to production of acid in the rumen and these acidic conditions increase susceptibility to laminitis.

Key actions : Ensure adequate feed space, good house layout and comfortable cubicles. Passageways should be cleaned regularly to avoid cows standing in depths of slurry. The Hillsborough data also demonstrated the benefits of regular footbathing with a 2 to 5% copper sulphate solution in controlling digital dermatitis. In nutritional terms, diet composition can be altered to reduce the incidence of acidosis; replace a portion of the fermentable material with protected fat to improve rumen conditions without sacrificing energy supply. Other dietary supplements may also be considered, such as use of specific rumen buffers to ‘mop-up’ excess acid.

Ketosis and fatty liver

These two conditions are commonly found around calving; they reflect inadequate energy supply and/or the lack of particular energy sources. In simple terms, the huge demand for energy post-calving as milk yield increases, coupled with limited feed intake, results in mobilisation of body fat for use as an energy source. This fat circulates to the liver, over-whelming its ability to process the fat, and leads to the production of ‘ketone bodies’ (ketosis) and/or a build-up of fat in the liver (fatty liver). Over-fat cows at calving have lower feed intakes and will mobilise large quantities of body fat after calving.

Key actions : Monitor cow condition closely prior to drying off and during the dry period to ensure cows are not calving down over-fat. Feed high energy diets post-calving to minimise the need for mobilisation of body fat as an energy source and reduce the risks of ‘flooding’ the liver with fat. Glucose or glucose precursors, and adequate methionine, can help the cow to process the additional fat and avoid liver problems.

Displaced abomasum (DA)

DAs are caused by a number of issues including the additional space left in the abdominal cavity following calving. Nutritionally, high-concentrate, low-fibre diets lead to a high rate of transfer of feed from the rumen to the abomasum, resulting in accumulation of gas and reduced movement of the abomasum. Low levels of calcium in the diet are also a culprit due to the role of calcium in muscle contraction.

Key actions: Feeding a balanced diet with adequate fibre will help limit DAs.

Cow health is of increasing importance in modern dairy herds as cow genetics drive increased production. Nevertheless, careful attention to nutrition and management of these high-performance animals can help minimise the incidence or extent of health problems and improve the bottom line.

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