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KMID : 1025520030450050725
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Journal of Animal Science and Technology
2003 Volume.45 No. 5 p.725 ~ p.730
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Bias and Accuracy of Single Milking Testing Schemes to Estimate Daily Milk Yield
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Abstract
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This study was conducted to evaluate the adequacy of an alternative ㏂-㏘ testing scheme for milk yield in comparison with the official test method based on weighing two milkings within 24 h. A total of 8,309 ㏘ milking weights and 6,767 ㏂ milking weights from 72 Holstein cows raised at N.L.R.I. were collected between October 2000 and November 2001. Ratios were computes for daily milk yield to ㏂ and ㏘ milking weights(direct yield ratios) and ratios of ㏂ and ㏘ milking weights to daily milk yield (inverse yield ratios). Analysis of variance indicated that the milking interval is the most important source of variation for yield ratios. Adjustment factors for estimating daily milk yield from single milking weights were derived through regression analysis of direct and inverse yield ratios on the length of the milking interval. Daily milk yield was estimated more precisely and accurately when adjustment factors were used than when single milking weights were doubled. In conclusion, alternative recording of ㏂ and ㏘ milking weights led to reliable estimates of milk yields.
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