Somatic cell count (SCC) and immunoglobulin G1 (IgG1) content were determined in mammary secretions of 15 Friesian x Jersey cows and 5 heifers at each milking for 10 d following natural calving. Milk yields for cows on d 1 were 20.2 l/d, declined sharply on d 2 to 14.4 l/d, then increased slightly, reaching 17.9 l/d by d 10. In contrast, heifer milk yields were low on d 1 (6.6 l/d) but increased steadily to 11.9 l/d by d 10. The SCC and IgG1 levels were extremely high on d 1 (1.50 x106 cells/ml and 24.0 g/l IgG1) but declined rapidly within 48 h of calving. Average SCC and IgG1 reduced below the penalty levels by d 4 for cows, and d 5 for heifers, confirming that milk should be withheld from the bulk tank for 4 d and 5 d after calving for cows and heifers respectively. Individual cows may exceed these levels for short periods.
Proceedings of the New Zealand Society of Animal Production, Volume 56, , 263-265, 1996
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