Browsing by Author "Goddard, P.J."
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- Effects of bovine somatotrophin (bST) on ovarian function in post-partum beef cowsPublication . Andrade, L.P.; Rhind, S.M.; Wright, I.A.; McMillen, S.R.; Goddard, P.J.; Bramley, T.A.The effects of bovine somatotrophin (bST) on ovarian follicle development and function and associated gonadotrophin profiles during the first nine weeks post partum were investigated in beef cows. Thirty-two cows (Shorthorn x Galloway) in moderately low body condition (BC) at calving were fed to maintain BC thereafter. At Weeks 2, 4, 6 and 8 post partum, animals were injected with 320 mg bovine somatotrophin (bST) (T, treated; n = 17) or with the carrier oil only (C, control; n = 15). Ovulation occurred in 4 of 17 T cows and 0 of 15 C cows (P = 0.10) by nine week post partum. Treatment with bST did not affect the numbers of small (3-8 mm in diameter) or large (> 8 mm in diameter) follicles or the granulosa cell populations but enhanced the oestradiol (P < 0.05) and insulin-like growth factor-I (IGF-I) content (P < 0.01) of large follicles by nine weeks post partum. It did not significantly affect the testosterone concentrations of large follicles. Circulating concentrations of growth hormone (GH) and IGF-I were higher in T cows than in C cows (P < 0.001) but were unrelated to gonadotrophin profiles or gonadotrophin receptor concentrations in the follicles. At Week 8, plasma insulin concentrations were higher in T cows than in C cows both before (P < 0.05) and after (P < 0.05) glucose injection. It is concluded that GH may play an important role in mediating the effects of nutritional state on ovarian function during the post-partum period, possibly through alteration of intrafollicular IGF-I concentrations.
- Effects of infusion of GnRH pulses and level of body condition on ovarian function in postpartum beef cowsPublication . Andrade, L.P.; Rhind, S.M.; Wright, I.A.; McMillen, S.R.; Goddard, P.J.; Bramley, T.A.An experiment was conducted to test the hypothesis that postpartum anoestrus in beef cows is prolonged in cows in low condition (BC) because they have a reduced LH pulse frequency compared with cows in high BC.
- Infusion of GnRH pulses and level of body condition on ovarian function in postpartum beef cowsPublication . Andrade, L.P.; Rhind, S.M.; Wright, I.A.; McMillen, S.R.; Goddard, P.J.; Bramley, T.A.An experiment was conducted to test the hypothesis that postpartum anoestrus in beef cows is prolonged in cows in low body condition (BC) because they have a reduced LH pulse frequency compared with cows in high BC. Thirty-six multiparous Blue-Grey (White Shorthorn x Galloway) cows were fed so that they calved in either low (L) (BC score 2.07; SE 0.05; n = 24) or high (H) (BC score 2.81; SE 0.08; n = 12) body condition. (…)