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Predicting Daily Milk Yield, Fat Percent, and Protein Percent from Morning or Afternoon Tests¹

Animal Research Centre, Agriculture Canada, Ottawa, Ontario K1A OC6

J. Wardrop

Animal Production Division, Agriculture Canada, Hull, Quebec K1A OC6

ABSTRACT

Factors for predicting daily milk yield, fat percent, and protein percent from either morning or afternoon tests at various milking intervals were estimated and evaluated for 12,800 individual cow-test-day records in 49 Ontario Record of Performance herds. Effects of herd and test month were small. Daily protein percent was predicted accurately from unadjusted morning or afternoon protein percent. Interaction of half-hour classes of milking intervals with monthly stages of lactation was large for milk yield. Hence, factors for predicting daily milk yield from morning or afternoon milk yield adjusted for milking interval were estimated separately for stages of lactation in which effects of milking intervals differed. For fat percent, interaction of milking interval by stage of lactation was small, permitting prediction factors across stages of lactation. When the factors were applied to the data from which they were derived, 75 to 80% of predictions of daily milk yield differed from observed by less than 2 kg. Only 50% of the predictions for daily fat percent deviated from observed by less than .2%, and 20% deviated by more than .4%.

¹ Contribution No. 1125 of the Animal Research Centre.