Accuracy of alternative methods of estimating weekly yields of milk fat and protein
1984
Clarke, T. | McGowan, A. (Victorian Dept. of Agriculture, Ellinbank (Australia). Dairy Research Inst.)
Thirty-four procedures were used to estimate the weekly yields of milk, milk fat and milk protein of 19 grazing cows on five occasions between the third and eighth months of lactation. The standard deviation of daily milk yield, fat and protein percentage of individual cows averaged 1.3 litres, 0.58 percent fat and 0.10 percent protein, respectively. There were no substantial interactions between the 34 procedures and stage of lactation. The average difference between the estimate of weekly milk yield from any one days' yield and the true weekly milk yield (accuracy) was 7.2 litres per week. The equivalent values for fat and protein yields were 0.59 and 0.22 kg per week. If total weekly milk yield was used to estimate fat yield, instead of using milk yield on days of testing only, there were small improvements in accuracy. As the day to day variation in level of protein in the milk was low, frequency and method of sampling for protein analysis was not important but the accuracy of estimating milk yield had a large effect on estimated weekly protein yield.
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