Stage of Lactation Effects, Repeatabilities and Influences on Weaning Weights of Yield and Composition of Milk in Beef Cattle

Abstract

MoNonecor, I., WrlroN, J. W., Ar-r-eN, O. B. eNo SoNc, H. 1983. Stage of lactation effects, repeatabilities and influences on weaning weights of yield and composition of milk in beef cattle. Can. J. Anim. Sci. 63: 751-761. Yield and composition of milk was measured on 270 cows with up to three parities each. Several combinations of breeds were included with all first parity females nursing Angus-sired calves and second and third parity females nursing Simmental-sired calves. Milk yields and compositions were obtained at 6, 14 and 22 wk postcalving. Yields were measured by both calf-nursing and machine-milking techniques. Milk yields were similar throughout lactation in first parity but declined over stages of lactation in parities two and three. No interactions between breed group of cow and stage of lactation were found. Milk fat percentages were found to be highest in early lactation, while protein percentages increased during lactation and lactose percentages remained constant. Milk yields increased from first to second parity, but were similar for second and third parities. Composition of milk was similar in all parities. Cows classified as being of dairy breeding had the highest milk yields, Jersey crosses were intermediate, while Charolais, British breeds and their crosses were lower and similar in milk yield. Jersey crosses were highest in milk fat percentage. Milk yield estimates were higher for the calf-nursing method than for the machine-milking method. Estimated repearabilities of total milk yield, milk fat percent, milk protein percent and milk lactose percent were 0.40,0.36,0.58 and 0.52, respectively. Milk yields had a significant positive effect on weaning weights of calves. The inclusion of either milk fat percent or milk protein percent as covariates did not increase the percent of variation explained in weaning weights. [Effets sur le stade de lactation, r6p6tabilit6 et effets sur le poids au sevrage du rendement laitier et de la composition du lait chez des bovins de boucherie.l Titre abr6g6: Rendement laitier et composition du lait de bovins de boucherre. Nous avons mesur6 le rendement laitier et la composition du lait de 270 vaches ayant connu chacune jusqu'ir 3 v6lages. Diverses combinaisons d'espbces ont 6t6 6tudi6es, les femelles n'ayant v6l6 qu'une fois nourrissant des veaux de pbre Angus, et les autres nourrissant des veaux de pbre Simmental. Le rendement et la composition ont 6t6 mesur6s 6, 14 et 22 semaines aprds le v0lage. Le rendement a pour sa part 6td 6valu6 bL partir du gain de poids des veaux d lat€t1,e ou d l'aide de machines de traite. Les rendements 6taient comparables pendant toute la p6riode de lactation chez les vaches ir un vOlage, mais il avait tendance d diminuer chez les vaches h deux et ir trois v€lages. Il n'y avait pas d'interaction entre la race et le stade de lactation. La teneur en matidre grasse 6tait plus 61ev6e en d6but de lactation. La teneur en prot6ines augmentait pour sa part avec le temps tandis que la teneur en lactose demeurait stable. Le rendement augm...

Milk Yield and Composition in Beef Cows and Their Effect on Cow and Calf Performance in Two Environments

“…The Brandon results were consistent with the findings of Mondragon et al (1983), where they reported that cow weight had no effect on milk yield, while fatter cows produced less milk. The Manyberries results are in agreement for the relationship of cow fat and milk yield but not for cow weight and milk yield.…”

“…Robison et al (1978), Lawson (1981), Mondragon et al (1983), and Butson and Berg (1984a,b) reported that milk protein percentage increased over periods. Lawson (1981) and Butson and Berg (1984a,b) PT and SNF by periods.…”

Supplementation with a mixture of whole rice bran and crude glycerin on metabolic responses and performance of primiparous beef cows

“…Milk production was recorded on days 0, 14, 21, and 35 from the beginning of supplementation, using a portable milking machine according to the method described by Mondragon et al (1983). In the morning, after cows received their meal, calves were separated and the udder was emptied using 20 IU of oxytocin i/m (Neurofisin, Lab Fatro, Uruguay).…”

Produção de leite e comportamento de amamentação em cinco sistemas de produção de gado de corte

“…Aparentemente, existe um padrão geral de declínio na produção de leite durante a lactação que seria dependente do regime alimentar (MONDRAGON et al, 1983). Nas raças Canchim e Nelore, ALENCAR et al (1988) observaram queda linear da produção de leite com a progressão da lactação.…”