Somatic cell count (SCC) is used as a proxy for intra-mammary infection, at both individual cow and herd level. It is therefore desirable to maintain a low SCC, of 100-150,000 cells/ml. (This acknowledges that when SCC drops below 100-150,000 cells/ml, there is an increased risk in both incidence and severity of clinical mastitis.) It is also known that the rate of new mammary gland infections has two peaks, one after drying off and the second around calving. Although there are several risk factors relating to mastitis, mammary gland infection and SCC, a recognised contributing factor to the peak of new infections around calving is the inevitable negative energy balance (NEB) that all cows suffer (Bradley et al., 2012).
Increasingly, it is realised that NEB after calving is associated with ‘dysfunctional inflammation’, which leads to increased risk of a range of metabolic and infectious conditions, including mastitis (Sordillo and Raphael, 2013). This is due to both increased fat mobilisation, leading to a change in the fatty acid composition of cell membranes, and the cow’s increased metabolic state associated with increased milk production, leading to oxidative stress (Sordillo, 2018). These two effects result in an inappropriate response to infection, for instance mastitis. In some situations, this can be seen as the immune response being less effective and mastitis pathogens being more able to establish infections, eg Staph. aureus and Strep. uberis, and in others, an over-enthusiastic inflammatory reaction can result in more severe signs, eg coliform or E. coli mastitis.
The effect of Glycal Forte® on SCC post-calving was demonstrated in a trial carried out on 90 cows in a high-yielding (>10,000 litres) UK dairy herd:
Cows in the Glycal Forte® group had a significantly lower average SCC in the 120 days after calving than the control group (P = 0.019). The likely explanation of this finding is the beneficial effect of Glycal Forte® on the energy balance of transition cows. (see ‘Reduce weight-loss post-calving).