A Selection Index for Fat Production in Dairy Cattle Utilizing the Fat Yields of the Cow and Her Close Relatives

Open Access
Publisher Website
Google Scholar
Abstract
An index was derived for selecting cows in the same herd, to find those with the highest breeding value for fat production. The index included the fat yields of the cow and of her dam, daughters, maternal sisters, and paternal sisters. Data came from all herds which were on Herd Improvement Registry Test of the American Jersey Cattle Club for at least 4 of the 5 yrs. during 1943-1947. These 293 herds were scattered among 42 states and the data included 23,330 lactation records for 12,405 cows. Differences between herds accounted for 39% of the total variance. Yearly avgs. for the whole group of data varied only a little but environment varied enough from yr. to yr. in the individual herds, each considered by itself, to account for 8% of the intra-herd individual variance. The pertinent intra-herd statistics were repeatability, + 0.412; correlation between maternal half sisters, + 0.073; correlation between paternal half sisters, + 0.120; and heritability,+ 0.201. The selection index derived would generally make progress about 1.10 to 1.15 times faster than if selections were made solely on the cow''s own performance. The exact ratio in an individual case would depend on the number of records on each cow, on the number of her relatives of each kind, and on the amt. of information available about these relatives.