Pre-puberal plasma luteinizing hormone concentrations and progesterone concentrations during the oestrous cycle and early pregnancy in Galway and Fingalway female lambs

Abstract

Twenty-four young female sheep, 12 Galways and 12 Fingalways, were used to study the effects of breed and level of nutrition on prepuberal plasma luteinizing hormone and progesterone concentrations throughout the oestrous cycle and during the first 35 days of pregnancy. The sheep were spring-born and were housed at the end of July when they weighed approx. 34 kg. Equal numbers of animals from each breed were fed on a concentrate diet either ad libitum or at a restricted level that was slightly above their estimated maintenance requirements. The Fingalways reached puberty 1 month earlier than the Galways (11 October ±4 days v. 10 November ±5 days). The restricted animals tended (P<0-10) to reach puberty later than those fed ad libitum (1 November ±5 days v. 20 October ±4 days). Breed differences in the mean level of plasma progesterone on any day of the oestrous cycle were not significant. The mean daily plasma progesterone concentration was similar for the animals on the two planes of nutrition throughout the cycle, with the exception of day 11 when those fed ad libitum had a significantly higher level (F<0-01). Plasma progesterone levels in the pregnant females between 5 and 35 days post mating were generally higher in Fingalways than in Galways and were not influenced by plane of nutrition. Plasma luteinizing hormone levels tended to be higher, during the 7 weeks before puberty, in Fingalways than in Galways and in animals fed ad libitum than in those on the restricted level of feeding.

The effect of age and diet on the reproductive performance of Sudan Nilotic ewes

“…The higher mortality of lambs born to P ewes may be in part due to the observed poor mothering ability of their dams. In addition, Quirke & Gosling (1979) and Quirke (1981) reported that ewe lambs usually produce weak progeny that will not survive the postnatal life. As for diet, the sorghum groups were found to have slightly lower lamb mortality proportion and this may be attributed to the higher body weight of dams and lambs.…”

Nutrition in the Reproduction of Farm Animals

“…In the sheep the major long-term nutritional influences on ovulation rate are seen in the adult rather than at the pubertal oestrus (Quirke & Gosling, 1979;Hamra & Bryant, 1982), but the opposite is true in pigs. For example, in the major European pig breeds daily ME intakes of 34 MJ as opposed to 21 MJ during the rearing phase enhanced average ovulation rate by 1.5 with a further response of 1.8 when intake during the oestrous cycle was increased to 41 MJ (for review, see Aherne & Kirkwood, 1985).…”

The effects of level of feeding during rearing and early pregnancy upon reproduction in young female sheep

“…These sheep were particularly prone to long cycle-lengths, both prior to and following mating with the fertile rams. The observations of Quirke and Gosling (1979) on plasma progesterone concentrations support both possibilities. A delay in the onset of oestrus in response to 'environmental stressors' has been reported elsewhere (Doney, Gunn and Griffiths, 1973;Doney, Gunn, Smith and Carr, 1976).…”