Age-Season Adjustment Factors for Alphine, LaMancha, Nubian, Saanen, and Toggenburg Dairy Goats

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Abstract
Multiplicative age-season adjustment factors for milk and fat yields of 5 breeds of dairy goats.sbd.Alpine, LaMancha, Nubian, Saanen and Toggenburg.sbd.were estimated from 1965-1976. This was done by fitting a 3-way mixed classification model containing random effects for does with fixed effects for herd-yr season and age-season for 7544, 1994, 7456, 3307 and 4599 lactation records from dairy goats in the USA. These factors reflect changes in milk and fat yields associated with age and season of freshening. As with dairy cattle, these factors indicated that milk records of goats are affected differently in different seasons for a particular age. Season of freshening affected younger does more than older herdmates. Does freshening in Jan.-March produced larger milk yields than herdmates that freshened at later mo. of the yr. Does reached peak production at 34-38 mo. and declined after 50 mo. of age. Repeatabilities for milk yield were 0.33, 0.29, 0.35, 0.27 and 0.35 for Alpine, LaMancha, Nubian, Saanen and Toggenburg breeds. The adjustment factors indicate that age factors for dairy cows currently being used for adjusting goat records should be replaced by separate factors developed for specific breeds of dairy goats.