Performance of crosses among Hereford, Angus and Simmental cattle with different levels of Simmental breeding: V. Calf production, milk production and reproduction of three- to eight-year-old dams.

Abstract

Measures of maternal productivity and reproduction of Hereford (HH), Angus-Hereford (AH), 25% Simmental-75% Hereford (1S3H), 50% Simmental-50% Hereford (1S1H) and 75% Simmental-25% Hereford (3S1H) dams were studied. Half of each dam breed group was bred to Tartentaise and half to Charolais sires to produce 706 calves at weaning from 930 exposures to breeding in a Montana range environment. Data were analyzed according to a model that included the fixed effects of year, dam breed group, dam age, calf sex, calf sire breed, plus appropriate two-way interactions, linear partial regression on calf birth date and random effects of sire within dam breed group (maternal grandsire of the calf) and sire within calf sire breed. Calf sex interacted with calf sire breed for several traits, but interactions were due to changes of magnitude of differences between sexes. There were no significant interactions of dam breed group with other main effects for calf growth traits, except for the interaction with calf sire breed for some calf growth traits. This interaction was due to a change in magnitude; it suggested that larger sire breeds should be matched to larger dam breeds with greater potential for milk production. The only significant interaction for traits that included reproduction of the dam was dam breed group X age of dam. Ranking of dam breed groups depended on age at measurement. Differences among dam breed groups were significant for most traits. Calf weaning weights for HH, AH, 1S3H, 1S1H and 3S1H dams were 211, 223, 227, 237 and 243 kg, respectively; calf weaning weights per cow exposed were 157, 163, 179, 189 and 169 kg; calf weaning weights per unit of dam weight were .40, .41, .43, .44 and .42, respectively. Thus, dam breed groups that weaned the largest calves were not necessarily the most productive under Montana range conditions.

Pesos e relações de peso de bezerros filhos de vacas nelore e cruzadas canchim x nelore

“…DAVIS et al (1983) obtiveram correlações negativas entre peso da vaca ao parto e eficiência de produção. KRESS et al (1990) verificaram que vacas com maior potencial leiteiro desmamaram bezerros mais pesados, entretanto, as vacas maiores não foram as mais produtivas em termos de peso de bezerro/peso de vaca.…”

Suplementação em sistema de creep-feeding de bezerros de corte lactentes e avaliação nutricional de matrizes de corte

“…The number of daily breastfeedings influences the milk production and physical wear of the mother (KRESS et al, 1990), such that a larger number of breastfeedings over a day could cause the cow to produce more milk as a response to the greater stimulus and consequently greater physical exhaustion. However, similarly to the results found in this study, Barros et al (2014), Lopes et al (2014), and Valente et al (2012) did not find differences in milk production among the cows that had their offspring supplemented or did not receive multiple supplementations.…”

Eficiência biológica de vacas de dois grupos genéticos amamentando bezerros puros ou F1, mantidas em diferentes condições de alimentação

“…Isto porque a produção de leite exerce efeito negativo nos índices reprodutivos do rebanho (Euclides Filho et al, 1983;Kress et al, 1990;Senna, 1996;Lobato et al, 1998), além de aumentar os requerimentos nutricionais das vacas que compõem o rebanho de cria (Ferrel & Jenkins, 1984;Montaño Bermudez et al, 1990;Freking & Marshall, 1992;Ribeiro et al, 2001).…”

“…Resultados de trabalhos comparando a eficiência produtiva de vacas de diferentes genótipos demonstraram que as mais pesadas, que produzem mais leite e desmamam bezerros mais pesados, podem ser menos produtivas (Kress et al, 1990;Ribeiro et al, 2001) ou mais produtivas (Montaño Bermudez et al, 1990;Barcellos et al, 1996) em relação às vacas mais leves.…”