Currently, there are no accepted methods for conducting herd tests on farms using fully automated milking systems in New Zealand. This study used data from the DairyNZ Greenfield pasture-based automatic milking research farm to evaluate six milksampling protocols to estimate daily milk, fat and protein yield and somatic cell count (SCC). Total milk, fat and protein yield, and SCC were estimated using all samples collected within 12, 16, 18, 24 and 36 hours from the start of the herd test and for a single test-day sample and compared with values calculated from a 48-hour gold standard herd test day. The correlation coefficient for milk and protein yields were relatively consistent when the sampling interval was shortened to 12 hours (r = 0.95, r = 0.94 for 12 hour milk yield and 12 hour protein yield). However, for fat yield it reduced from 0.96 for a 36 hour sampling interval to 0.88 for a 12 hour interval. The number of cows without a milking increased from 6.7% to 27.8% when the sampling interval decreased from 36 to 12 hour. A 24 hour sampling interval provided high correlations for milk, fat and protein yields, and SCC, with a 48 hour gold standard and minimised the number of missed cows.
Proceedings of the New Zealand Society of Animal Production, Volume 73, Hamilton, 29-32, 2013
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