Abstract

Somatic Cell Counts (SCC) are commonly used as an indirect measure of prevalence of bacterial infection and of milk quality in dairy cattle. However, interpretation of SCC in dairy goats is more complex due to a higher basal SCC and the fact that SCC appear to be influenced by a number of factors other than bacterial infection. Increased SCC is associated with bacterial infection of the udder in goats (Dulin et al., 1983; Ryan et al., 1993; Poutrel et al., 1997). However, SCC in goats also increases with age (Dulin et al., 1983), increases as lactation progresses (Dulin et al., 1983; Kalogridou-Vassiliadou et al., 1992; Wilson et al., 1995), varies among breeds (Sung et al., 1999) and increases as milk production declines (Zeng & Escobar, 1994; Pizzillo et al., 1994). Stressors such as change in nutrition, kidding, oestrus and vaccination have also been suggested as causes of increased SCC in goats (Lerondelle et al., 1992; Aleandri et al., 1994; Pizzillo et al., 1994; Zeng et al., 1997). The stress response includes both corticosteroid release from the adrenal cortex in response to adrenocorticotrophic hormone (ACTH) and adrenal medulla release of the catecholamines adrenaline and noradrenaline (Tyrrell et al., 1991). Injection of dairy cattle with exogenous ACTH results in an elevation in circulating leukocyte counts but no change in the SCC (Paape et al., 1973, 1975). However, transportation is likely to release both corticosteroids and catecholamines and has been used to examine various physiological responses in goats (Sanhouri et al., 1989; Greenwood & Shutt, 1992) …

S, McDougall, FM Anniss, and AA Cullum

Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 16-18, 2002