Relationships between calf birth weight, prepartum concentrations of plasma energy metabolites and resumption of ovulation postpartum in limousine suckled beef cows

The aim of this study was to determine the relationship between energy stat us before calving and calf birth weight and their potential effects on inte rval between calving and first ovulation. Sixty-nine Limousine, suckled bee f cows were sampled weekly over a 3-yr period during the last 2 mo of pregn ancy to determine the concentrations of nonesterified fatty acids (NEFA), b eta-3-hydroxybutyrate (beta-OHB), glucose and glycerol. After parturition, progesterone concentrations were measured weekly to determine time of resum ption of ovulation. Cows were allotted to 3 groups according to calf birth weight (Heavy: > 44 kg, n = 37; Medium: 39 to 43 kg, n = 56; and Light: < 3 8 kg, n = 45) and to postpartum ovarian resumption of cyclicity (Late: > 11 wk, n = 41; Mid: 7 to 10 wk, n=57; and Early: < 6 wk, n = 40). Puerperium glycaemia of the darns was steady state (0.66 +/- 0.03 g/L) and was not rel ated to calf birth weight. Plasma NEFA, beta-OHB and glycerol values were h igher (P<0.05) in Heavy than in Medium and Light group darns during the las t 4 wk of pregnancy. Interval between calving and first ovulation was signi ficantly longer for primiparous than for multiparous cows (respectively, 9. 9 +/- 2.0 and 7.7 +/- 1.4 wk; P<0.05). Calf birth weight was not related to time of first ovulation. Late primiparous cows had higher NEFA plasma conc entrations than Mid and Early group primiparous cows during the last 4 wk o f pregnancy, whereas NEFA plasma concentrations were not related to interva l between calving and first ovulation in multiparous cows. Thus, lipomobili zation increased with calf birth weight during the last 4 wk of pregnancy. High level of body reserves mobilization was associated with delayed first ovulation in primiparous but not in multiparous cows. (C) 1999 by Elsevier Science Inc.