Browsing by Author "Rhind, S.M."
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- Efeito da infusão de GnRh nos perfis de LH e na população de folículos ováricos às 7 semanas pósparto em vacas de carne em diferente condição corporalPublication . Andrade, L.P.; Rhind, S.M.; Wright, I.; McMillen, S.R.Foi realizada uma experiência com o objectivo de testar a hipótese do anestro pósparto ser superior em vacas de carne em baixa condição corporal (CC) devida a uma reduzida libertação de LH. Vacas Blue—grey (Shorthorn x Galloway) parindo quer em baixa CC (grupo B constituído por 24 animais, CC média de 2,07 (s.e.±0,05) quer em alta CC (grupo A constituído por 12 animais, CC média de 2,81 (s.e. ±0.08)) foram alimentadas de modo a manterem a CC após o parto. Das 5 às 7 semanas pósparto, metade das vacas do grupo B foram submetidas a uma infusão com 2 µg de GnRH em 2 ml de uma solução salina (G) cada 2 horas, tendo-se conseguido induzir ovulação em 10 das 12 vacas. Todas as outras vacas foram submetidas a uma infusão só com uma solução salina (S) durante o mesmo período e a ovulação foi induzida somente em 1 das 12 vacas em alta CC e em uma das 11 vacas em baixa CC. Os perfis de libertação de gonadotrofinas, a frequência e a amplitude da libertação de LH, não foram afectados, quer pela infusão com GnRH, quer pela CC. O número de folículos pequenos (3-7,9 mm de diâmetro) e grandes (> 8mm de diâmetro) presentes à 7.ª semana pósparto, o número de receptores para a LH na teca e na granulosa e de FSH na granulosa, bem como o número de células da granulosa presentes nos folículos grandes à 7.ª semana pósparto, não evidenciam diferenças significativas (P>0,05). As concentrações intrafoliculares de estradiol, testosterona e de IGF-I nos folículos grandes, à 7.ª semana pósparto, não foram significativamente afectados, nem pela infusão de GnRH, nem pela CC. Contudo, observou-se uma tendência para elevadas concentrações de estradiol em vacas em alta CC quando comparada com vacas em baixa CC. Os resultados sugerem que a infusão de GnRH acelerou o processo de desenvolvimento folicular nas vacas em baixa CC ; outros factores além da CC poderão estar envolvidos do desenvolvimento folicular.
- Effect of bovine somatotropin (growth hormone) treatment on gonadotropin profiles and ovarian follicle populations during the postpartum period in beef cows in low body conditionPublication . Andrade, L.P.; Rhind, S.M.; Wright, I.A.; McMillen, S.R.; Whyte, T.K.The effect of growth hormone on ovarian follicle development and on associated gonadotropin profiles was investigated.
- Effect of GnRH pulse infusion on LH profiles and ovarian follicle populations at 7 weeks post partum in beef cows in different body conditionsPublication . Andrade, L.P.; Rhind, S.M.; Wright, I.A.; McMillen, S.R.; Whyte, T.K.An experimente was conducted to test the hypothesis that post partum anoestrus in beef cows is prolonged in low condition cows because of a reduced LH pulse frequency.
- Effect of GnRH pulse infusion on LH profiles and ovarian follicle populations at 7 weeks post-partum in beef cows in different body conditionPublication . Andrade, L.P.; Rhind, S.M.; Wright, I.A.; McMillen, S.R.; Whyte, T.K.Effect og GnRH pulse infusion on LH profiles and ovarian follicle populations at 7 weeks post-partum in beef cows in different body condition.
- Effects of body condition and GnRH pulse infusion on LH profiles, ovarian follicle populations and ovulation in postpartum beef cowsPublication . Andrade, L.P.; Rhind, S.M.; Wright, I.A.; McMillen, S.R.; Whyte, T.K.An experiment was designde to determine: a) whether or not the normal process of follicular development can be accelerated in LBC cows by infusion of pulses of GnRH, so that their postpartum anoestrous period is as short as that of cows in high body condition (HBC) and b) the effect of GnRH pulse infusions on associated gonadotrophin profiles.
- 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 bovine somatotropin (Growth hormone) treatment on gonadotropin profiles and ovarian follicle populations during the postpartum period in beef cows in low body conditionPublication . Andrade, L.P.; Rhind, S.M.; Wright, I.A.; McMillen, S.R.; Whyte, T.K.Effects of bovine somatotropin (Growth hormone) treatment on gonadotropin profiles and ovarian follicle populations during the postpartum period in beef cows in low body condition.
- 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.
- Effects of maternal undernutrition during early pregnancy on apoptosis regulators in the ovine fetal ovaryPublication . Lea, R.G.; Andrade, L.P.; Ray, M.T.; Hannah, L.T.; Kyle, C.E.; Murray, J.F.; Rhind, S.M.; Miller, D.W.This study aimed to determine whether reduced fetal ovary folliculogenesis in ewes undernourished during early/midpregnancy is associated with altered ovarian cell proliferation and/or the expression of apoptosis-regulating genes. Groups of ewes (n 5 11–19) were fed either 100% (high; H) or 50% (low; L) of metabolisable energy requirements for live-weight maintenance during selected windows of gestation. All animals were killed at days 50, 65 or 110 of gestation. Between mating and slaughter, control animals were fed the H ration, while animals of other subgroups were fed the L ration from (a) mating to slaughter at 50, 65 or 110 days; (b) 0 to 30 days; (c) 31 to 50 or 65 days; or (d), in the day 110 slaughter group only, from 66 to 110 days. Bouin’s-fixed fetal ovaries were examined for (a) Ki67 immunoexpression (proliferation) and (b) Bax and Mcl-1 (apoptosis-regulating genes) expression by in situ hybridisation (day 110) and immunohistochemistry (days 50, 65 and 110). At day 50, maternal nutrition had no effect on Ki67, predominant in germ cells, or Bax and Mcl-1, predominant in the oocytes. Restricted maternal food intake from 0 to 30 days significantly reduced staining for Ki67 in germ cells at day 65 (P < 0.05) but increased staining in granulosa cells at day 110 (P < 0.05). In animals fed the L ration for 110 days, primordial follicle Bax and Mcl-1 were significantly increased (Bax: P < 0.01; Mcl-1: P < 0.05). Granulosa cell Bax was also increased (P < 0.05). When the L ration was fed from 66 to 110 days, granulosa cell Bax (P < 0.05) and primordial follicle Mcl-1 (P < 0.01) were also significantly increased. In the fetal ovarian vasculature, animals underfed for 0–110 days had significantly elevated perivascular Mcl-1 (P < 0.001) and endothelial Bax expression (P < 0.05). Moreover, at day 110, endothelial Mcl-1 was increased by underfeeding from 0 to 30 days (P < 0.05). These data indicate that maternal undernutrition alters proliferation and the expression of apoptosis-regulating genes in the developing fetal ovary. The precise mechanism depends on the window of maternal food restriction.
- 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. (…)