Genetic parameter estimates for prenatal and postnatal mortality in Nellore cattle

Abstract

The aim of this study was to estimate genetic parameters for prenatal (PRE) and postnatal (POS) mortality in Nellore cattle. A total of 13 141 (PRE) and 17 818 (POS) records from Nellore females were used. PRE and POS were recorded using binary scale scores: a score of '1' was given to calves that were born alive (PRE) and those that were alive at weaning (POS), and a score of '0' was given to calves that were not alive at or around birth (PRE), as well as to those weighed at birth but not at weaning (POS). The relationship matrix included 698 sires, 107 paternal grandsires and 69 maternal grandsires. Data were analysed using Bayesian inference and a sire-maternal grandsire threshold model, including contemporary groups as random effects, and the classes of dam age at the beginning of mating season (for PRE), and dam age at calving and birthweight (linear covariable) (for POS), as fixed effects. For both traits, the covariance between direct and maternal effects (r ) was estimated (r ≠ 0) or fixed at zero (r = 0). PRE and POS rates were 3.00 and 4.04%, respectively. Estimates of direct and maternal heritability were 0.07 and 0.17, respectively, for PRE, and 0.02 and 0.07, respectively, for POS, assuming r = 0. For r ≠ 0, these estimates were 0.07 and 0.12, respectively, for PRE, and 0.03 and 0.07, respectively, for POS. The correlation estimates between direct and maternal effects were -0.71 (PRE) and -0.33 (POS). PRE and POS show low genetic variability, indicating that these traits probably suffer major environmental influences. Additionally, our study shows that the maternal genetic component affects preweaning calf mortality twice as much (or more) as the direct genetic component. A large number of offspring per sire is necessary in progeny tests to genetically decrease calf mortality.

Maternal-offspring behavior of Guzerat beef cattle

“…The calf mortality rate until weaning was 13.7% (Table 1), which corroborates those described in previous studies, from 3 to 15% until weaning (Bunter et al, 2014;Magalhães Silva et al, 2017;Ring et al, 2018). The need for human assistance and the vigor absence imply problems for calf development, as they indicate increasing chances of pre-weaning mortality.…”

“…The mortality rate in Brazilian beef herds is about from 8 to 10% (Corrêa et al, 2001;Azevedo Júnior et al, 2017;Magalhães Silva et al, 2017). These authors reported that the highest percentage of calf mortality occurs in the first weeks of life.…”

“…These authors reported that the highest percentage of calf mortality occurs in the first weeks of life. Perinatal mortality is associated with difficulties in the parturition, extreme weights at birth (Bunter et al, 2014), and maternal ability (Riley et al, 2004;Schmidek et al, 2013), including nursing and protection after birth (Magalhães Silva et al, 2017).…”

“…Studies evaluating the maternal care in Zebu breeds, discussed the effects on the preconception period caused by the environmental conditions (Grewal et al, 2019), calving difficulty, growth rate (Cortés-Lacruz et al, 2017;Rainforth, 2019), genetic traits (Magalhães Silva et al, 2017), and diet (Miguel-Pacheco et al, 2019;Noya et al, 2019). Nevertheless, studies on the behavioral traits in the relation of calf and cow in postparturition, and the behavior effects associated with the efficiency in herds are scarcely studied.…”

Behavioral and Morphological Traits of Nellore Cattle That Can Influence Calf Survival and Performance from Birth to Weaning

“…The mortality rate observed the present study (4%) was the same as was reported by Magalhães Silva et al, [33] and lower than the values reported by Bunter et al [2] and Nascimento et al [34] for a similar beef cattle production system (9.5% and 8%, respectively). Given the low mortality rate observed and the high proportion of calves evaluated with the highest score for vigor (96.2%), no association was found between these variables in the present study.…”