Responses of prolactin and hair growth to selection for age at puberty in Angus cattle

Abstract

A trial was carried out over a 7-year period (1999 to 2005 calf crops) to compare indicators of seasonality in Angus cattle, which were part of a long-term genetic selection experiment. Divergent selection was applied for early ('AGE2') or late ('AGE1') age at puberty (AP) in heifers, and selection lines differed over the 7-year period by 62 days (15% of the mean). The primary measures of seasonality studied in 629 heifer progeny (59 sire groups) were serum concentration of prolactin (PRL), and winter and summer hair growth. Serial samples were obtained for PRL from 11 to 18 months of age, and data were analysed with adjustment for cortisol concentration. Using restricted maximum likelihood procedures with an animal model, heritability estimates were: AP, 0.26 6 0.03; log e PRL concentration, 0.23 6 0.07; log e cortisol concentration, 0.22 6 0.07; hair weight, 0.21 6 0.04; and hair length, 0.09 6 0.05. Corresponding repeatability estimates for the last four traits were 0.49 6 0.03, 0.38 6 0.03, 0.21 6 0.04, and 0.64 6 0.02, respectively. The genetic correlation between AP and log e PRL concentration was estimated at 20.29 6 0.13 (P , 0.05). PRL concentration in the AGE2 line after passing through puberty was 11 6 5% lower than in the AGE1 line (P , 0.05). Line effects were not significant for hair weight or hair length. It was concluded that divergent selection for AP changed PRL concentration, which may partly reflect sensitivity to changing day length.

Genetic and environmental factors that affect tick infestation in Nelore x Angus crossbreed cattle

“…BaRIcHEllo et al (2010) for canchim breed (0.52). However, the heritability estimated in our study was higher than that mentioned by MoRRIS et al (2011) for hair length, according to REIMann et al ( 2018) hair length is the measure that most closely resembles the evaluation of hair coat scores. This indicated that the estimate is according to the estimates already reported in the literature.…”

Genetic assessment of rectal temperature and coat score in Brahman, Angus, and Romosinuano crossbred and straightbred cows and calves under subtropical summer conditions

“…An estimate for heritability for the condition of the coat (subjectively scored as shiny, dull, or very dull) in dairy cows was 0.05 (Jørgensen et al, 2010). Estimates of heritability for hair weight and length in Angus cattle were 0.21 and 0.09, respectively (Morris et al, 2011). Maia et al (2009) reported an estimate of heritability for the effective thermal conductivity of the coat as 0.18.…”

Heifers with positive genetic merit for fertility traits reach puberty earlier and have a greater pregnancy rate than heifers with negative genetic merit for fertility traits

“…Traits of interest could include the age at puberty and heifer pregnancy rate. These candidate traits are measured before calving-related trait and have a greater heritability than traditional reproductive traits captured after calving (Morris et al, 2000(Morris et al, , 2011. Additionally, phenotypic and genetic correlations between heifer traits and subsequent fertility suggest that heifers that calve early have better fertility as cows (Pryce et al, 2007;Tiezzi et al, 2012), indicating that selection for heifer fertility traits could result in better cow fertility.…”

“…The difference in the onset of puberty reported here is comparable with changes in the onset of puberty reported previously when undertaking single trait section. For example, in a long-term study focused on direct genetic selection for earlier puberty, over 7-yr of single selection puberty was shifted by 62 d (Morris and Amyes, 2005;Morris et al, 2011). This large shift SCR system heat refer to the automated monitoring of estrus events using the SCR Heatime HR system (SCR Engineers Ltd., Netanya, Israel), which included the collar-mounted Heatime sensor.…”