Mm. Mialon et al., Genetic variability of the length of postpartum anoestrus in Charolais cows and its relationship with age at puberty, GEN SEL EVO, 32(4), 2000, pp. 403-414
Fertility records (n = 1802) were collected from 615 Charolais primiparous
and multiparous cows managed in an experimental herd over an Ii-year period
. The objectives of the study were to describe the genetic variability of t
he re-establishment of postpartum reproductive activity and the relationshi
p with body weight (BW) and body condition score (BCS) at calving and age a
t puberty. The length of postpartum anoestrus was estimated based on weekly
blood progesterone assays and on twice daily detection of oestrus behaviou
r. The first oestrus behaviour was observed 69 days (+/-25 days s.d.) post-
calving and the first positive progesterone measurement ( > 1 ng . mL(-1))
was observed at 66 days (+/-22 days s.d.) for the group of easy-calving mul
tiparous suckling cows. Estimates of heritability and repeatability were h(
2) = 0.12 and r = 0.38 respectively, for the interval from calving to first
oestrus (ICO). Corresponding values were h(2) = 0.35 and r = 0.60 for the
interval from calving to the first positive progesterone test (ICP). The ge
netic correlation between both criteria was high (r(g) = 0.98). The genetic
relationships between postpartum intervals and BW and BCS of the female at
calving were negative: the genetic aptitude to be heavier at calving and t
o have high body reserves was related to shorter postpartum intervals. A fa
vourable genetic correlation between age at puberty and postpartum interval
s was found (r(g) between 0.45 and 0.70). The heifers which were geneticall
y younger at puberty also had shorter postpartum intervals.