Performance of crosses among Hereford, Angus, and Simmental cattle with different levels of Simmental breeding: VI. Maternal heterosis of 3- to 8-year-old dams and the dominance model2

Abstract

Data from Hereford, 25% Simmental-75% Hereford, 50% Simmental-50% Hereford, and 75% Simmental-25% Hereford dams were used to estimate maternal heterosis and level of agreement with the dominance model. Cows were located at the Northern Agricultural Research Center near Havre, MT and were managed consistent with practices for western range environments. Sample halves of dam breed groups were bred to Charolais and Tarentaise sires to produce calves at 3 to 8 yr of age. There were 766 exposures to breeding that resulted in 581 calves. Breed group means for most traits supported the dominance model. Maternal heterosis was estimated by regression techniques for 22 cow and calf traits. Maternal heterosis was not significant for day of conception, number of services, gestation length, or calving difficulty. Estimates of maternal heterosis for calf growth traits ranged from .7% for weaning height to 5.2% for weaning weight and 7.5% for weaning condition score. Calf weight per unit of cow weight at weaning showed significant maternal heterosis (7.1%). Higher levels of maternal heterosis were exhibited for milk production (8.2 to 11.1%) and the negative, but nonsignificant, estimate of maternal heterosis for early minus late milk production suggested more persistent lactation for crossbred cows. Maternal heterosis was 11.5% for proportion of dams that calved and 10.4% for proportion of dams that weaned calves. Calf weaning weight per cow exposed to breeding, a characteristic combining calf growth and dam reproduction, exhibited 17.9% maternal heterosis.

Genetic relationships among direct and maternal components of milk yield and maternal weaning gain in a multibreed beef herd.

“…Similar to findings of Kress et al (1992), estimated heterosis was higher for Cow MY than that for Cow WG . The estimate of 5.5% observed in this study was within the range of 2.76 to 14.5% reported for beef cattle by Marshall et al (1976), Gregory et al (1992), and Kress et al (1992). Johnston et al (1995) reported an average 32% heterosis for Cow MY (Butson and Berg, 1984;Mezzadra et al, 1989;McCarter et al, 1991).…”

“…Heterosis for Calf WG (8.0%) was higher than reported in the literature; Dillard et al (1980), Cundiff et al (1992), , and Kress et al (1995) noted estimates ranging from 3 to 5.8%. Heterosis for Cow WG , conversely, was to the low end of the range of 3 to 5.8% reported by Dillard et al (1980, and Kress et al (1992).…”

Evaluation of the Criollo breed Romosinuano as purebred and crossbred cows with Brahman and Angus in Florida: I. Reproduction and parturition1,2,3

“…Corva et al (1995) reported a large estimate of weaning rate heterosis (0.1) for Criollo-Angus; no heterosis was detected for Romosinuano-Angus in the present study. Low estimates of heterosis for weaning rate in Bos taurus crosses were −0.03 (Gregory et al, 1978;Newman et al, 1993), but most were in the range from 0.03 to 0.07 (Cundiff et al, 1974;Peacock and Koger, 1980;Kress et al, 1992). Studies involving breeds with perhaps a greater milk role in their history (Brown Swiss, Milking Shorthorn) in combination with British breeds had a slightly higher range of estimates (0.09 to 0.13; Spelbring et al, 1977;Gregory et al, 1978;Olson et al, 1985).…”

Effects of inbreeding and heterozygosity on preweaning traits in a closed population of Herefords under selection.

“…Much as expected, the regression coefficients associated with direct and maternal heterozygosity did not differ significantly from zero (Table 4a,b). Under the hypothesis of dominance, which seems to be the case for growth traits in beef cattle (Kress et al, 1992;Gregory et al, 1994), heterozygosity has an effect opposite to that of inbreeding. Thus, the theoretical expectation is for heterosis to recover effects of inbreeding depression.…”