Prediction of Heifer Transmitting Ability from Genetic Evaluations of Sire, Dam, and Maternal Grandsire

Abstract

Estimated transmitting abilities for milk of 258,201 Holstein heifers from first lactations were regressed on sire's milk proof, maternal grandsire's milk proof, and either dam's estimated transmitting ability from milk in first lactation or dams's estimated transmitting ability from milk of all lactations. Effects of year of birth of dam, dam's estimated transmitting ability for milk from first lactation, for milk from all lactations, estimated transmitting ability for fat from first lactation or for fat from all lactations were determined by sorting data into deciles by each of these criteria and calculating partial regression coefficients within each decile. For data in deciles on dams's estimated transmitting ability for milk in first lactation, no further information was gained from all lactations. Partial regression coefficients from regression of heifer's estimated transmitting ability from first lactation on dam's estimated transmitting ability from first lactation, maternal grandsire's proof, and sire's proof were similar to approximate theoretical upper limits. The partial regression coefficient for dam's estimated transmitting ability from all lactations was much smaller than expected. Because regression on dam's estimated transmitting ability from first lactation resulted in weights more closely approximating theoretical upper limits than weights from regression on dam's estimated transmitting ability from all lactations, the use of the former is preferred to predict heifer's estimated transmitting ability from first lactation.

Prediction of Transmitting Ability of Heifers from Genetic Evaluations of Dams When Dams and Herdmates Are Required to Have a First Record

“…Use of more than a first lactation record of the dam in estimation of her ETA decreases the size of the partial regression coefficient for the dam's ETA. For example, the partial regression coefficient for the dam's ETA decreased from .76 to .39 when all available records of the dam were used in calculation of the dam's ETA (10). In the current study, the partial regression coefficient for the dam's ETA was .72 when the dam's ETA was calculated from only first lactation records of the dam and her herdmates and was only .17 when the dam's ETA was calculated from all available lactation records of the dam and her herdmates when both the dam and her herdmates were required to have first lactation records.…”

“…14 for the maternal grandsire. These regression coefficients vary only slightly depending on the number of records in the sire and maternal grandsire proofs (10).…”

“…Records of 222,576 Holstein heifers had ETA based only on milk records of first lactation when each dam had an ETA based only on records of first lactation and an ETA based on milk records of all iactations (calculated from a data set in which all cows had a first record), the Northeast Artificial Insemination Sire Comparison (NEAISC) of her sire, and the NEAISC of her maternal grandsire (MGS). Partial regression coefficients for the regression of heifer's first lactation ETA on sire's NEAISC, NEAISC of MGS, and either dam's first lactation ETA or dam's all lactation ETA were calculated according to procedures in (10), which included sorting the data into deciles based on dam's milk ETA for first lactation, milk ETA for all lactations, birth date, fat ETA of first lactation, and fat ETA of all lactations. Partial regression coefficients were compared to approximate theoretical partial regression coefficients.…”

“…Partial regression coefficients for estimated transmitting ability (ETA) of the dam calculated from all lactation records for prediction of breeding values of progeny have been smaller than approximate theoretical regression coefficients, although partial regression coefficients for the ETA of the dam calculated from first lactation records alone are similar to theoretical approximations (5,10). In (10), dams were required to have first lactation records prior to calculation of their ETA from Received May 21, 1984.…”

“…In (10), dams were required to have first lactation records prior to calculation of their ETA from Received May 21, 1984.…”