Beef Cattle Weaning Research Articles

Evaluation of Alternate Weaning Techniques with Fecal Cortisol Metabolites

Weaning in beef cattle is defined as the physical separation of the cow-calf pair and is normally associated with dietary, social, environmental, and immunological changes in the calf. Abrupt weaning leads to behavioral changes, decreased weight gain, and increased levels of stress-associated hormones.
 Alternative weaning methods are utilized to decrease stress on calves. Fenceline weaning is moving the calf into an adjacent paddock which ends suckling, but allows the calf to maintain social contact with its dam. Fenceline weaning reduces the time calves spend walking and vocalizing, and increases the time calves spend eating and lying down. Measurement of blood cortisol can be problematic due to the acute nature of cortisol release which may reflect handling and response to blood collection in addition to baseline cortisol status. The utilization of fecal cortisol metabolites allows determination of cortisol status hours prior to sampling. The objective of this study was to compare fecal cortisol metabolite concentrations in beef calves weaned abruptly and by alternate techniques.

Bayesian analysis of selection for greater weaning weight while maintaining birth weight in beef cattle

An experimental Hereford herd established in 1960 was used from 1986 to 2006 to select for increased weaning weight (W) without increasing birth weight (B). Data were B and W collected over the 47 yr from 2,124 calves. Including ancestors, the pedigree file had 2,369 animals. Selection was practiced only in males. In the first stage (1986 to 1993), mass-selected bulls were chosen with the index I = B + 9374.76 RDG (relative daily gain). From 1994 to 2006, the selection criterion for bull i was I(i) = BLUP(i)(WD) - 2.33 BLUP(i)(BD), where the BLUP were for the direct BV of B (BD) and W (WD), respectively. Predictions were obtained from a 2-trait animal model with B having only BD, and W with WD and WM (maternal additive effects). Selection response was estimated using a Bayesian approach by means of the Gibbs sampler for a 2-trait animal model including BD, BM (maternal BV for B), WD, and WM. Estimated heritabilities for BD, BM, WD, and WM were 0.40, 0.23, 0.05, and 0.23, respectively. The correlation between BD and BM was close to zero (0.01), and between WD and WM was positive (0.37). The correlation between BD and WD was 0.07, and between BM and WM was 0.58. The 2 methods used to estimate selection response gave similar results. In both periods BD decreased, whereas BM increased. The reduction of BD due to selection was slightly larger in the second period than in the first one. The regression of BV for W increased due to selection in both stages, but selection response was 21.6% larger from 1986 to 1992 than from 1993 to 2006. The maternal effect, WM increased more than 3 times compared with WD in the first period, but ended up being almost the same value as WD in period 2. The Bulmer effect was manifested by the decrease in magnitude of all (co)variance components during selection. It is concluded that selection to increase BW at weaning in beef cattle, although not increasing BW at birth, was moderately effective.

Dystocia-Related Risk Factors

Dystocia is one of the leading causes of calf mortality between birth and weaning in beef cattle. An understanding of the effects of parturition and dystocia on perinatal calf viability is paramount for the development of breeding and calving programs that will minimize calf losses. This article discusses the factors affecting birth weight and replacement heifer development and redefines dystocia as any birth that reduces calf viability, causes maternal injury, or reduces maternal reproduction.