Genetic and non-genetic effects on calf vigor at birth and preweaning mortality in Nellore calves

Abstract

-The objective of the present study was to evaluate the genetic and non-genetic effects that influence vigor at birth and preweaning mortality in Nellore calves. A total of 11,727 records of births that occurred between 1978 and 2006, offspring of 363 sires, were analyzed. Poor calf vigor at birth (VB) and preweaning mortality divided into stillbirth (SB), early mortality (EM) and total mortality (TM) were analyzed as binary variables. Generalized linear models were used for the evaluation of non-genetic effects and generalized linear mixed models for genetic effects (sire and animal models). The incidences were 4.75% for VB, 2.66% for SB, 5.28% for EM, and 7.99% for TM. Birth weight was the effect that most influenced the traits studied. Calves weighing less than 22 kg (females) and less than 24 kg (males) were at a higher risk of low vigor and preweaning mortality. Preweaning mortality was higher among calves born from cows aged ≤3 and ≥11 years at calving compared with cows aged 7 to 10 years. Male calves presented less vigor and higher preweaning mortality than female calves. Selection for postweaning weight did not influence preweaning mortality. The heritability estimates ranged between 0.01 and 0.09 for VB, 0.00 and 0.27 for SB, 0.03 and 0.17 for EM and 0.02 and 0.10 for TM. Stillbirth should be included as a selection criterion in breeding programs of Nellore cattle, alone or as part of a selection index, aiming to reduce preweaning mortality.

Dehydration as a risk factor for calf mortality in northern Australia

“…This is consistent with a study where in a dry-tropical environment, Brahman calves that died during neonatal life were on average 6.1 kg lighter than those that survived (Muller, 2007 Schmidek et al, 2013). Therefore, the association between decreased birth vigour and increased calf mortality may be at least partly explained by low birth weight.…”

“…Kim et al (1988)'s report is consistent with calf autopsies where hairballs have been found in the calf abomasum, derived from hair around the udder or from the calf licking itself (Bellows et al, 1987). In studies on Bos indicus calves (n > 3000), frequency of low vigour has been reported at 4.75% in Brazilian Nellore (Schmidek et al, 2013) and 10.6% in a mixed herd of Brahman and Brahman-influenced calves (Riley et al, 2004), with other studies reporting relative frequencies of weak Brahman calves (n > 3000) within this range of values (Riley et al, 2004, Wythe, 1970. As birth vigour heritability values ranged from 0.01 to 0.09 in Nellore calves (Schmidek et al, 2013) and was 0.09 in Brahmans, management interventions may provide greater improvements in calf vigour than selection (Riley et al, 2004).…”

“…In studies on Bos indicus calves (n > 3000), frequency of low vigour has been reported at 4.75% in Brazilian Nellore (Schmidek et al, 2013) and 10.6% in a mixed herd of Brahman and Brahman-influenced calves (Riley et al, 2004), with other studies reporting relative frequencies of weak Brahman calves (n > 3000) within this range of values (Riley et al, 2004, Wythe, 1970. As birth vigour heritability values ranged from 0.01 to 0.09 in Nellore calves (Schmidek et al, 2013) and was 0.09 in Brahmans, management interventions may provide greater improvements in calf vigour than selection (Riley et al, 2004). A delay from birth to first suckling has been reported to vary with season of calving (Edwards, 1982), which is likely a function of nutritional and environmental conditions experienced by the dams.…”

“…The association between low-birth weight and low birth-vigour (Schmidek et al, 2013) is suggestive that poor overall foetal growth may be associated with a reduced capacity of organ systems in the newborn calf. In humans, maternal diet plays an important role in the epigenetic programming of the foetus, which persists through the life of the offspring (Barker, 2004).…”

Preweaning Calf Survival of a Nellore Beef Cattle Population

“…In Brazil, mortality rate averages of 8 and 4% were already reported for preweaning and post-weaning periods respectively (Euclides Filho, 2000). Specifically for Nellore cattle, the most important and populous zebu cattle in Brazil, losses of 6% (Corrêa et al, 2000) and 7.99% (Schmidek et al, 2013) until weaning were reported for calves in extensive breeding. Nevertheless, few quantitative studies considering preweaning mortality rate have been conducted in such breed populations.…”