Genetic aspects of advanced reproductive biotechnologies in dairy cattle

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Authors

Fatehi, Jalal

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University of Guelph

Abstract

A six year (1990-1995) embryo transfer program (ET) in a large dairy herd was investigated to explain the genetic and environmental effects on embryo yield, pregnancy rate, and genetic trends of milk, fat and protein yields of animals produced by ET or artificial insemination. Number of recovered and viable embryos per flush were collected from 563 recoveries and were 7.53 and 4.59, respectively. Pregnancy rates in lactating cows and heifers were 44.9% and 54.6% respectively. Donor, service sire, superovulatory regimen, season and interactions between donor and the three effects of technician, drug and season on viable embryo yield were significant (P < 0.05). Estimated repeatability and heritability of recovered embryo yield were 0.33 and 0.21, respectively. Morphological embryo quality and stage, season, recipient's lactation number, quadratic effect of days in milk, and fresh or frozen embryo on pregnancy rate were significant (P < 0.05). Genetic trends were calculated using estimated breeding values (EBVs) obtained from predicted transmitting ability (PTA) nationally estimated by USDA, and from within-herd EBVs. Higher annual genetic trends were observed in the ET group compared to the AI group using both evaluation methods, particularly using national genetic evaluation. Along with the genetic trends, estimated heritabilties for milk, fat and protein yields were 0.27, 0.19 and 0.24 respectively. On the basis of information on a large, single-herd MOET program and discounted expression terms in the following 10 years, computed revenue for a female calf from an average donor was approximately $150 (U.S.) higher than a female calf from an average recipient. After deducting the costs of extra feed consumption and ET, an expected additional profit of +$5 (U.S.) was obtained for a female ET calf relative to a female calf from a recipient.

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Keywords

embryo transfer, dairy cow, genetics, environmental effects, embryo yield, pregnancy rate, genetic trends, milk yield, fat yield, protein yields, artificial insemination

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