USE OF MILK RECORDS IN ONE HERD TO PREDICT A COW’S PRODUCTION IN A SECOND HERD

Abstract

The objective was to relate the average herdmate milk deviation of cows which completed one or more records in each of two Canadian dairy herds. Record of Performance records of Canadian Holstein cows transferred at least once during their productive life were studied to evaluate the use of milk records in one herd to predict a cow’s production in a second herd. Each record was adjusted for days open and age-at-calving and then expressed as a deviation from first lactation or second and later lactation herdmate averages. Weighted regression of the cow’s average herdmate deviation in the second herd on her real producing ability estimated in the first herd was 0.87 ±.07 Breed Class Average (BCA). Weighted regression of the cow’s average BCA in the second herd on her real producing ability estimated from absolute BCA’s was much lower (0.30 ±.05). Approximately 80% of the cows ranked similarly on deviations in the second herd as they did in the first herd. A study of cows transferred from low to high producing herds revealed that real producing ability estimates based on herdmate deviations were excellent indicators of future production (b = 0.98 ±.15). The regression for cows transferred from high to low producing herds was lower (b = 0.44 ±.17).