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Author: search.filters.author.Hickson RESubject: search.filters.subject.heritability

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    Genetic Parameters for Growth, Ultrasound and Carcass Traits in New Zealand Beef Cattle and Their Correlations with Maternal Performance
    (MDPI, (Basel, Switzerland), 2021-12-23) Weik F; Hickson RE; Morris ST; Garrick DJ; Archer JA
    Research has shown that enhancing finishing performance in beef cows is feasible; however, any adverse impact of selection strategies for finishing performance on the performance of the maternal herd should be taken into account. The aim of this research was to examine the inheritance of growth, ultrasound and carcass traits in finishing beef cattle and to evaluate their correlations with maternal performance traits. Data were collected from a nationwide progeny test on commercial New Zealand hill country farms comprising a total of 4473 beef cows and their progeny. Most finishing traits were moderately to highly heritable (0.28-0.58) with the exception of meat or fat colour and ossification (0.00-0.12). Ultrasound scan traits had high genetic correlations with corresponding traits measured at slaughter (rg = 0.53-0.95) and may be used as a selection tool for improved genetic merit of the beef carcass. Fat content determined via ultrasound scanning in the live animal or at slaughter in finishing cattle is positively genetically correlated with rebreeding performance (rg = 0.22-0.39) in female herd replacements and negatively correlated with mature cow live weight (rg = -0.40 to -0.19). Low-magnitude associations were observed between the genetic merit for carcass fat traits with body condition in mature cows.
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    Estimation of genetic parameters and individual and maternal breed, heterosis, and recombination loss effects for production and fertility traits of spring-calved cows milked once daily or twice daily in New Zealand
    (Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association, 2023-01) Jayawardana JMDR; Lopez-Villalobos N; Hickson RE; McNaughton LR
    The objectives of this study were to estimate genetic parameters and individual and maternal breed, heterosis, and recombination loss effects for milk production and fertility traits of Holstein Friesian (F), Jersey (J), and crossbred Holstein Friesian and Jersey (F × J) cows milked once daily (OAD) or twice daily (TAD) in New Zealand. Data on 278,776 lactations from 30,217 OAD and 170,680 TAD milking cows across 644 spring-calving herds were available. Genetic parameters and individual and maternal breed, heterosis, and recombination loss estimates were obtained from univariate animal models. Heritability and repeatability estimates for milk production, milk composition, and fertility traits were consistent across the milking frequencies. Heritability estimates for yields of milk, fat, protein, and lactose varied between 0.21 and 0.29 in OAD and TAD. Heritability estimates for fertility traits ranged from 0.01 to 0.08 in both populations, and estimates were slightly greater in TAD than OAD milking cows. In both milking populations, individual breed effects for yields were in favor of F cows; however, maternal breed effects for yields were in favor of J dams. Jersey cows were more fertile than the F cows in both milking populations, but maternal breed effects for fertility traits were in favor of F dams. Individual heterosis effects were favorable for all traits and were consistent across milking regimens. Crossbred F × J cows had significantly shorter intervals from start of mating to first service and from start of mating to conception, and a higher proportion of 3-wk submission, 3-wk in calf, and 3-wk calving relative to the average of purebred F and J cows. Recombination loss effects were not always unfavorable for production and fertility traits, but most estimates were small with larger standard errors. Favorable maternal heterosis effects were associated with production traits in both milking systems, but maternal heterosis effects were less likely to influence reproductive performance.