The purpose of this study was to estimate the effect of increased SCC on production in New Zealand dairy farms. Herd test data from lactations one through six were used in the study. Herd test milk, fat and protein yields were modelled as a function of days in milk at the time of the herd test and the logarithm (base 2) of SCC. The model estimates were used to obtain the predicted value for each observation using the actual log SCC and again where the log SCC was increased by one (i.e. doubling the SCC level). For first-lactation cows, the reduction in a 270-day lactation yield from a doubling of the SCC was estimated to be 78 litres, 2.39 kilograms and 2.04 kilograms for milk, fat and protein yield, respectively. Herd SCC level also influenced the extent to which a doubling of SCC decreased production. For first-lactation cows every doubling of SCC was predicted to result in an average loss of 67 and 90 litres in the lowest and highest quartiles, respectively.

AM, Winkelman, WA Montgomerie, and DL Johnson

Proceedings of the New Zealand Society of Animal Production, Volume 67, Wanaka, 293-296, 2007
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