This review covers scientific and technical publications from 1982 to
1996 on the influence of mastitis, both clinical and subclinical, on r
aw milk yield and composition and dairy product yield and quality. In
some cases, earlier references are provided for clarification. It prov
ides an update for the reviews of Kitchen (1981) and Munro et al. (198
4). The review examines somatic cell count (SCC) as a measure of masti
tis; the effect of SCC on the yield and quality of raw milk and dairy
products; the SCC threshold affecting milk products; seasonality and l
ate-lactation milk; milk quality incentive schemes for SCC; and mastit
is control practices and SCC. The literature reviewed confirms the del
eterious effects of mastitis on milk composition and the yield and qua
lity of dairy products. Other factors that alter milk composition (e.g
. season, stage of lactation, nutrition) sometimes confound the precis
e effects of SCC. A SCC standard of 400,000 cells/mL for bulk milk is
being adopted in milk quality schemes around the world as a result of
the European Union requirements which apply from January 1998. This le
vel will minimise the effects of mastitis on product quality, although
negative effects on product quality have been reported for milk with
a SCC as low as 100,000 cells/mL. Further, a bulk milk somatic cell co
unt of 400,000 cells/mL indicates that around 40% of cows in a herd ar
e infected.