Effect of age and genetic group on the development of calves weaned at 63 days until one year of age

Abstract

The development of beef calves born of Charolais (CH), Nellore (N), and Charolais × Nellore crossbred cows with Charolais (CHP) and Nellore (NP) predominance, was evaluated from birth to 12 months of age. The cows were grouped into three age classes: primiparous, young and adult. The net energy requirements for maintenance and gain of the calves were also evaluated, as were the production and availability of energy in the milk of the evaluated cows. We used 93 pairs of contemporary cows and calves maintained in natural pasture. From birth to 21 days of age and from 21 to 42 days of age, the calves of adult cows presented the highest average daily weight gain (ADG), while the calves of young and primiparous cows had similar ADG. The highest net energy requirements for maintenance (NEm) and gain (NEg) were for crossbred and Charolais calves, the latter being similar to Nellore calves. The energy available in the milk of the adult cows was 33% higher than that of primiparous cows. The weight gain of calves was influenced by the age of the cow until weaning. The pre-weaning and post-weaning weights of calves were affected by the genetic group, and adult and young cows produced heavier calves in the pre-weaning period than primiparous cows.

Body size in beef cows and its influence on calf production

“…This determines greater development and greater body weight at the various stages of their lives, where, during the post-weaning period, development is dependent on individual potential and on the influence exerted by the environment and management (D. D. Silveira et al, 2019a). When feeding via maternal milk is lost, calves basically need to obtain their food from the available pasture, and as such, their performance is a reflection of the quality of the food and their ability to transform it into weight gain (M. F. Silveira et al, 2019b). When feeding conditions are adequate, large animals suffer no restrictions on feeding (Beck et al, 2016).…”

“…The level of nutrition and the use of early weaning technology (Tao et al, 2018) favoured the reproductive performance of the cows, achieving mean values greater than 80% pregnancy, which is consistent with advanced beef farming. Early weaning favours the reproductive parts of the cow, which are inhibited by the presence of the calf and by milk production, the latter being very costly for the animal (M. F. Silveira et al, 2019b). After weaning, all the nutrients that were previously directed to milk production are used for weight recovery and the body condition score; for the nervous system, this indicates an improvement in the nutritional level, activating the reproductive parts previously inhibited due to the nutritional deficiency (Tao et al, 2018;M.…”

“…The production efficiency of the cows at calving and weaning was calculated by dividing the weight of the calves at weaning by the body weight of cows at calving and weaning respectively, and multiplying by 100, with the result in kilograms of calf for every 100 kilograms of cow in the herd (M. F. Silveira et al, 2019b). The calf production index was determined by multiplying the pregnancy rate of the cows by the weight of the calves at weaning, expressed in kilograms of calf weaned per cow in the herd (M. F. Silveira et al, 2019b).…”

“…Milking was performed on two milk let down of the udder, one frontal and one rear. The resulting production was multiplied by two to obtain the total milk production of the udder, and later adjusted for 24h00 hours (M. F. Silveira et al, 2019b). Total milk production was estimated from the sum of the measurements from days 21, 42, and 63 postpartum, individually multiplied by 21.…”

Body mass index at calving on performance and efficiency of Zebu cow herds

“…The production efficiency of the cows at calving and at weaning was calculated by dividing the weight of the calves at weaning by the body weight of cows at calving and weaning, respectively, and multiplying the result by 100. Results were expressed in kilograms of calf per 100 kilograms of cow in the herd (Silveira et al, 2019). The calf production index was determined by multiplying the pregnancy rate of the cows by the weight of the calves at weaning, and expressed in kilograms of calf weaned per cow in the herd (Silveira et al, 2019).…”