The proportion of anoestrous ewes ovulating after exposure to a sexually active ram is variable m... more The proportion of anoestrous ewes ovulating after exposure to a sexually active ram is variable mainly due to whether an LH surge is induced. The aim of this study was to determine the role of oestradiol (E2) in the ram-induced LH surge. In one study, we measured the plasma concentrations of E2 in ewes of different breeds before and after the 'ram effect' and related these patterns to the presence and latency of the LH surge, while another compared ovarian responses with the 'ram effect' following exposure to rams for 2 or 12 h. In all ewes, the concentration of E2 increased 2-4 h after rams were introduced and remained elevated for 14.5±0.86 h. The quantity of E2 secreted before the LH surge varied among breeds as did the mean concentration of E2. The granulosa cells of IF ewes collected after 12 h exposure to rams secreted more E2 and progesterone and had higher levels of StAR than the 2 h group but in MV ewes there was no differences between these groups for any o...
This paper discusses the phenomenon of nutritional flushing in ewes whereby increased nutrition s... more This paper discusses the phenomenon of nutritional flushing in ewes whereby increased nutrition stimulates folliculogenesis and ovulation rate. In addition the paper reviews recent findings on the effects of increased levels of nutrition on the blood concentrations of reproductive and metabolic hormones in the ewe and some of the intraovarian changes that take place in response to nutritional stimulation. Finally, in the paper, we propose a model of the physiological mechanism for the nutritional stimulation of folliculogenesis and we review how closely the model fits recent published and unpublished evidence examining the mechanism of flushing. Nutritional stimulation alters the blood concentrations of some metabolic hormones. By using short-term models of nutritional flushing, we have shown that as the blood concentrations of insulin and leptin increase that of growth hormone decreases while that of IGF-I appears unaffected by the nutritional flushing. Nutritional flushing also al...
Two experiments in parous Welsh Mountain ewes determined the pattern of natural cervical relaxati... more Two experiments in parous Welsh Mountain ewes determined the pattern of natural cervical relaxation over the peri-ovulatory period and investigated FSH and Misoprostol as cervical relaxants to facilitate transcervical passage of an insemination pipette into the uterine cavity. Following synchronisation of oestrus using progestagen sponges and PMSG (500 IU) the depth of cervical penetration was determined using a modified cattle insemination pipette as a measuring device. Penetration of the cervix was least at the time of sponge removal and increased to a maximum at 72 h after sponge removal and then declined. Intra-cervical administrations of either ovine FSH (Ovagen; 2mg) or Misoprostol (1mg; a Prostaglandin E(1) analogue) facilitated cervical penetration. Ovagen given 24h after sponge removal allowed transcervical intrauterine penetration in 100% of ewes at 54 and 60 h after sponge removal while Misoprostol given 48 h after sponge removal allowed trans-cervical penetration in 100%...
In dairy cows inseminated during the hot months of the year, there is a decrease in fertility. Di... more In dairy cows inseminated during the hot months of the year, there is a decrease in fertility. Different factors contribute to this situation; the most important are a consequence of increased temperature and humidity that result in a decreased expression of overt estrus and a reduction in appetite and dry matter intake. Heat stress reduces the degree of dominance of the selected follicle and this can be seen as reduced steroidogenic capacity of its theca and granulosa cells and a fall in blood estradiol concentrations. Plasma progesterone levels can be increased or decreased depending on whether the heat stress is acute or chronic, and on the metabolic state of the animal. These endocrine changes reduce follicular activity and alter the ovulatory mechanism, leading to a decrease in oocyte and embryo quality. The uterine environment is also modified, reducing the likelihood of embryo implantation. Appetite and dry matter intake are both reduced by heat stress thus prolonging the pos...
This experiment was conducted to determine if feed supplementation before exposure of anoestrous ... more This experiment was conducted to determine if feed supplementation before exposure of anoestrous does to males increases ovulation rate. Does (n=50) grazing natural vegetation were divided into two groups (n=25). One group received no feed supplementation, while the other was supplemented daily, with a mixture of 950 g of alfalfa hay, 290 g of rolled corn and 140 g of soy bean per animal for 7 days before exposure to bucks. On April 7, all females were exposed to four adult sexually active bucks (two per group) for 15 days. The ovulation rate at the ovulation detected within 5 days of exposure to males, assessed by transrectal ultrasonography, was greater (P<0.05) in supplemented (1.6+/-0.2) than in non-supplemented females (1.0+/-0.2). In contrast, ovulation rate at the subsequent ovulation, detected between days 6 and 15 of contact with males, was not different (P>0.05) between supplemented (1.3+/-0.1) and non-supplemented females (1.3+/-0.2). Feed supplementation 7 days before exposure to sexually active bucks of females managed under grazing conditions increased their ovulation rate at the first male-induced ovulation but the stimulatory effect of supplementation did not persist and was not observed at the subsequent ovulation.
Elevated non-esterified fatty acids (NEFA) concentrations in non-pregnant animals have been repor... more Elevated non-esterified fatty acids (NEFA) concentrations in non-pregnant animals have been reported to decrease pancreatic responsiveness. As ovine gestation advances, maternal insulin concentrations fall and NEFA concentrations increase. Experiments were designed to ...
The proportion of anoestrous ewes ovulating after exposure to a sexually active ram is variable m... more The proportion of anoestrous ewes ovulating after exposure to a sexually active ram is variable mainly due to whether an LH surge is induced. The aim of this study was to determine the role of oestradiol (E2) in the ram-induced LH surge. In one study, we measured the plasma concentrations of E2 in ewes of different breeds before and after the 'ram effect' and related these patterns to the presence and latency of the LH surge, while another compared ovarian responses with the 'ram effect' following exposure to rams for 2 or 12 h. In all ewes, the concentration of E2 increased 2-4 h after rams were introduced and remained elevated for 14.5±0.86 h. The quantity of E2 secreted before the LH surge varied among breeds as did the mean concentration of E2. The granulosa cells of IF ewes collected after 12 h exposure to rams secreted more E2 and progesterone and had higher levels of StAR than the 2 h group but in MV ewes there was no differences between these groups for any o...
This paper discusses the phenomenon of nutritional flushing in ewes whereby increased nutrition s... more This paper discusses the phenomenon of nutritional flushing in ewes whereby increased nutrition stimulates folliculogenesis and ovulation rate. In addition the paper reviews recent findings on the effects of increased levels of nutrition on the blood concentrations of reproductive and metabolic hormones in the ewe and some of the intraovarian changes that take place in response to nutritional stimulation. Finally, in the paper, we propose a model of the physiological mechanism for the nutritional stimulation of folliculogenesis and we review how closely the model fits recent published and unpublished evidence examining the mechanism of flushing. Nutritional stimulation alters the blood concentrations of some metabolic hormones. By using short-term models of nutritional flushing, we have shown that as the blood concentrations of insulin and leptin increase that of growth hormone decreases while that of IGF-I appears unaffected by the nutritional flushing. Nutritional flushing also al...
Two experiments in parous Welsh Mountain ewes determined the pattern of natural cervical relaxati... more Two experiments in parous Welsh Mountain ewes determined the pattern of natural cervical relaxation over the peri-ovulatory period and investigated FSH and Misoprostol as cervical relaxants to facilitate transcervical passage of an insemination pipette into the uterine cavity. Following synchronisation of oestrus using progestagen sponges and PMSG (500 IU) the depth of cervical penetration was determined using a modified cattle insemination pipette as a measuring device. Penetration of the cervix was least at the time of sponge removal and increased to a maximum at 72 h after sponge removal and then declined. Intra-cervical administrations of either ovine FSH (Ovagen; 2mg) or Misoprostol (1mg; a Prostaglandin E(1) analogue) facilitated cervical penetration. Ovagen given 24h after sponge removal allowed transcervical intrauterine penetration in 100% of ewes at 54 and 60 h after sponge removal while Misoprostol given 48 h after sponge removal allowed trans-cervical penetration in 100%...
In dairy cows inseminated during the hot months of the year, there is a decrease in fertility. Di... more In dairy cows inseminated during the hot months of the year, there is a decrease in fertility. Different factors contribute to this situation; the most important are a consequence of increased temperature and humidity that result in a decreased expression of overt estrus and a reduction in appetite and dry matter intake. Heat stress reduces the degree of dominance of the selected follicle and this can be seen as reduced steroidogenic capacity of its theca and granulosa cells and a fall in blood estradiol concentrations. Plasma progesterone levels can be increased or decreased depending on whether the heat stress is acute or chronic, and on the metabolic state of the animal. These endocrine changes reduce follicular activity and alter the ovulatory mechanism, leading to a decrease in oocyte and embryo quality. The uterine environment is also modified, reducing the likelihood of embryo implantation. Appetite and dry matter intake are both reduced by heat stress thus prolonging the pos...
This experiment was conducted to determine if feed supplementation before exposure of anoestrous ... more This experiment was conducted to determine if feed supplementation before exposure of anoestrous does to males increases ovulation rate. Does (n=50) grazing natural vegetation were divided into two groups (n=25). One group received no feed supplementation, while the other was supplemented daily, with a mixture of 950 g of alfalfa hay, 290 g of rolled corn and 140 g of soy bean per animal for 7 days before exposure to bucks. On April 7, all females were exposed to four adult sexually active bucks (two per group) for 15 days. The ovulation rate at the ovulation detected within 5 days of exposure to males, assessed by transrectal ultrasonography, was greater (P<0.05) in supplemented (1.6+/-0.2) than in non-supplemented females (1.0+/-0.2). In contrast, ovulation rate at the subsequent ovulation, detected between days 6 and 15 of contact with males, was not different (P>0.05) between supplemented (1.3+/-0.1) and non-supplemented females (1.3+/-0.2). Feed supplementation 7 days before exposure to sexually active bucks of females managed under grazing conditions increased their ovulation rate at the first male-induced ovulation but the stimulatory effect of supplementation did not persist and was not observed at the subsequent ovulation.
Elevated non-esterified fatty acids (NEFA) concentrations in non-pregnant animals have been repor... more Elevated non-esterified fatty acids (NEFA) concentrations in non-pregnant animals have been reported to decrease pancreatic responsiveness. As ovine gestation advances, maternal insulin concentrations fall and NEFA concentrations increase. Experiments were designed to ...
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