Body size in beef cows and its influence on calf production

Abstract

Cattle farming becomes more intensive when the productive efficiency of the cows is increased, and nutrition is adjusted to the animal biotype. Eighty purebred Charolais and Nellore cows and their crosses between 3 and 7 years of age, were grouped for body weight at calving into Light (332.6 kg), Moderate (385.3 kg) and Heavy (444.6 kg). Cows and their calves were weighed at calving, at 63 days (early weaning) and at 210 days. The estimated milk production of the cows was evaluated by manual milking at 21, 42 and 63 days postpartum. The difference in the weight of the cows at calving was maintained during lactation and at 210 days postpartum. The body size of the cow did not influence milk production. Heavier cows produce heavier calves up to 365 days of age compared to lighter cows. The reproductive performance of the cows is not affected by their weight. The production of kilograms of calf for every 100 kilograms of cow at calving and weaning is higher in Light cows. The production of kilograms of calf adjusted for the pregnancy rate of the cows is higher in Heavy cows. Production efficiency in kilograms of calf per area is lower in Heavy cows.

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

“…Additionally, it can be an excellent evaluation criterion, as it associates the energy expenditure for maintenance and production, whose response is the kilograms of calf produced. The higher efficiency of the 'small' cows in this study shows that although they produced lighter calves, their calf production in kilograms is more economical due to a probable lower feed intake resulting from their lower maintenance and production requirements (Vara et al, 2020), or even lesser use of areas for the maintenance of the calfcow pair (Farias et al, 2018a,b). The literature does not comprise studies on the calf production index associating calf weaning weight with cow pregnancy as a function of the cow's BMI.…”

“…When postpartum nutrition is compromised, heavier cows may have their reproductive performance impaired (Vaz et al, 2020a). On the other hand, when the nutritional level is adequate, body weight at calving does not influence the reproductive performance of adult beef cows (Moura et al, 2014;Vara et al, 2020). Beef cows must have adequate body reserves to ensure basic reproductive vital functions and milk production postpartum (Lemes et al, 2017;Marques et al, 2016).…”

“…Up until weaning, besides the genetic factor, calves are highly dependent on the maternal environment, which is almost exclusively determined by the milk yield of their mothers. Vara et al (2020) worked with the same weaning age, but body size classes at calving, and found that calves from large cows were heavier at birth and at weaning than those born to small cows.…”

“…Daily and total milk yields differed between the BMI classes, with the small cows having lower daily and total values than the moderate and large cows. Smaller cows produce less milk due to their smaller size and lower synthesis efficiency (Fonseca et al, 2012), which results in lighter calves at weaning (Dervishi et al, 2017;Vara et al, 2020). However, pre-and postpartum nutrition (Lemes et al, 2017;Marques et al, 2016) and the calving season (Bitencourt et al, 2020) can influence the amount of milk produced.…”

“…In this regard, the primiparous condition is a determining factor even in good nutritional conditions (Castilho et al, 2018). On the contrary, with the use of postpartum supplementation (Farias et al, 2018a,b) or calcium salt supplementation in the pre-and postpartum periods in adult cows (Vara et al, 2020), pregnancy rates are influenced by cow body size. The probability of pregnancy is directly related to the nutritional status of the cow as well as to its current energy balance, and its prolongation is harmful to the subsequent reproductive performance (Pacheco et al, 2020a;Torres, Tineo, & Raidan, 2015).…”