The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform

David T. Baird - One of the best experts on this subject based on the ideXlab platform.

  • Corpora lutea induced by gonadotrophin-releasing hormone treatment of anoestrous Welsh Mountain ewes: reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro
    Reproduction, 2020
    Co-Authors: T. A. Bramley, D. Stirling, G. S. Menzies, David T. Baird
    Abstract:

    Seasonally anoestrous Welsh Mountain ewes received 250 ng gonadotrophin-releasing hormone (GnRH) every 2 h, with (Group 1; n = 13) or without (Group 2; n = 14) progesterone priming for 48 h. Fourteen control ewes (Group 3) were studied during the luteal phase in the breeding season. Animals in Group 4 (n = 12) received progesterone priming followed by 250 ng GnRH at increasing frequency for 72 h, while ewes in Group 5 (n = 13) were given three bolus injections of 30 [micro]g GnRH at 90-min intervals. All treatment regimens induced ovulation. However, only corpora lutea (CL) from ewes in Group 3 (breeding season) or Group 4 exhibited normal luteal function. Luteal luteinizing hormone (LH) receptor levels were significantly higher on day 12 than day 4, and CL from groups with adequate CL (3 and 4) had significantly higher ¹²⁵I-human chorionic gonadotrophin (hCG)-binding levels than the three groups with inadequate CL on day 12. LH-binding affinity was unchanged. Exogenous ovine LH (10 [micro]g) in vivo on days 3 or 11 after ovulation induced a pulse of progesterone in ewes with adequate CL: however, ewes in Groups 1, 2 and 5 showed no significant response. Basal progesterone secretion in vitro was significantly greater on day 4 than on day 12. Maximal steroidogenic responses of adequate and inadequate CL to hCG and to dibutyryl cyclic-3',5'-AMP were similar at both stages of the luteal phase. However, the EC₅₀ for hCG on days 4 and 12 was 10-fold lower for groups with an adequate CL (0.1 IU hCG/ml) than for inadequate-CL groups (1 IU hCG/ml; P

  • corpora lutea induced by gonadotrophin releasing hormone treatment of anoestrous Welsh Mountain ewes reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro
    Reproduction, 2005
    Co-Authors: T. A. Bramley, D. Stirling, G. S. Menzies, David T. Baird
    Abstract:

    Seasonally anoestrous Welsh Mountain ewes received 250 ng gonadotrophin-releasing hormone (GnRH) every 2 h, with (Group 1; n = 13) or without (Group 2; n = 14) progesterone priming for 48 h. Fourteen control ewes (Group 3) were studied during the luteal phase in the breeding season. Animals in Group 4 (n = 12) received progesterone priming followed by 250 ng GnRH at increasing frequency for 72 h, while ewes in Group 5 (n = 13) were given three bolus injections of 30 [micro]g GnRH at 90-min intervals. All treatment regimens induced ovulation. However, only corpora lutea (CL) from ewes in Group 3 (breeding season) or Group 4 exhibited normal luteal function. Luteal luteinizing hormone (LH) receptor levels were significantly higher on day 12 than day 4, and CL from groups with adequate CL (3 and 4) had significantly higher ¹²⁵I-human chorionic gonadotrophin (hCG)-binding levels than the three groups with inadequate CL on day 12. LH-binding affinity was unchanged. Exogenous ovine LH (10 [micro]g) in vivo on days 3 or 11 after ovulation induced a pulse of progesterone in ewes with adequate CL: however, ewes in Groups 1, 2 and 5 showed no significant response. Basal progesterone secretion in vitro was significantly greater on day 4 than on day 12. Maximal steroidogenic responses of adequate and inadequate CL to hCG and to dibutyryl cyclic-3',5'-AMP were similar at both stages of the luteal phase. However, the EC₅₀ for hCG on days 4 and 12 was 10-fold lower for groups with an adequate CL (0.1 IU hCG/ml) than for inadequate-CL groups (1 IU hCG/ml; P <0.05). Thus, in addition to the well-characterized premature sensitivity of GnRH-induced inadequate CL to endometrial luteolysin, we have shown (1) a marked decrease in total number of cells in the CL, a profound reduction in vascular surface area, and a decrease in mean large luteal cell volume (with no change in large luteal cell numbers), (2) decreased luteal LH receptor and progesterone content compared with adequate CL and (3) that CL that were becoming, or were destined to become, inadequate failed to respond to ovine LH in vivo and were 10-fold less sensitive to hCG in terms of luteal progesterone secretion in vitro.

Julian Skidmore - One of the best experts on this subject based on the ideXlab platform.

  • the effect of alternating months of long days and short days on plasma luteinising hormone and testosterone concentrations in Welsh Mountain pony stallions
    Animal Reproduction Science, 1991
    Co-Authors: Julian Skidmore
    Abstract:

    Abstract The hypothesis to be tested was whether the highly seasonal Welsh Mountain Pony stallion can be transformed into an animal potentially able to reproduce all the year round by exposing it to alternating months of “long days” (16L:8D) and “short days” (8L:16D). Two Welsh Mountain Pony stallions were kept under natural daylight from January (8L:16D) until 4 July (16L:8D) and thereafter on alternating four-week periods of short days and long days. Plasma samples were collected hourly over 12-hour periods in February, May and June, and again at the end of every four-week artificial photoperiod. Luteinising hormone (LH) and testosterone concentrations were determined by radio-immunoassay. Plasma LH and testosterone concentrations rose from 0.34 ng ml −1 and 2.52 nmol l −1 respectively in February to maximum values of 2.66 ng ml −1 and 4.97 nmol l −1 in June (all values expressed as geometric means). Each subsequent period of short days suppressed both LH and testosterone concentrations (greatest mean = 1.03 ng ml −1 and 3.16 nmol l −1 ) whereas each period of long days stimulated them (smallest mean = 1.49 ng ml −1 and 3.64 nmol l −1 ). It was concluded that alternating months of long and short days did not transform the highly seasonal Welsh Mountain Pony into an animal capable of reproducing all the year round.

  • The effect of alternating months of “long days” and “short days” on plasma luteinising hormone and testosterone concentrations in Welsh Mountain Pony stallions
    Animal Reproduction Science, 1991
    Co-Authors: Julian Skidmore
    Abstract:

    Abstract The hypothesis to be tested was whether the highly seasonal Welsh Mountain Pony stallion can be transformed into an animal potentially able to reproduce all the year round by exposing it to alternating months of “long days” (16L:8D) and “short days” (8L:16D). Two Welsh Mountain Pony stallions were kept under natural daylight from January (8L:16D) until 4 July (16L:8D) and thereafter on alternating four-week periods of short days and long days. Plasma samples were collected hourly over 12-hour periods in February, May and June, and again at the end of every four-week artificial photoperiod. Luteinising hormone (LH) and testosterone concentrations were determined by radio-immunoassay. Plasma LH and testosterone concentrations rose from 0.34 ng ml −1 and 2.52 nmol l −1 respectively in February to maximum values of 2.66 ng ml −1 and 4.97 nmol l −1 in June (all values expressed as geometric means). Each subsequent period of short days suppressed both LH and testosterone concentrations (greatest mean = 1.03 ng ml −1 and 3.16 nmol l −1 ) whereas each period of long days stimulated them (smallest mean = 1.49 ng ml −1 and 3.64 nmol l −1 ). It was concluded that alternating months of long and short days did not transform the highly seasonal Welsh Mountain Pony into an animal capable of reproducing all the year round.

T. A. Bramley - One of the best experts on this subject based on the ideXlab platform.

  • Corpora lutea induced by gonadotrophin-releasing hormone treatment of anoestrous Welsh Mountain ewes: reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro
    Reproduction, 2020
    Co-Authors: T. A. Bramley, D. Stirling, G. S. Menzies, David T. Baird
    Abstract:

    Seasonally anoestrous Welsh Mountain ewes received 250 ng gonadotrophin-releasing hormone (GnRH) every 2 h, with (Group 1; n = 13) or without (Group 2; n = 14) progesterone priming for 48 h. Fourteen control ewes (Group 3) were studied during the luteal phase in the breeding season. Animals in Group 4 (n = 12) received progesterone priming followed by 250 ng GnRH at increasing frequency for 72 h, while ewes in Group 5 (n = 13) were given three bolus injections of 30 [micro]g GnRH at 90-min intervals. All treatment regimens induced ovulation. However, only corpora lutea (CL) from ewes in Group 3 (breeding season) or Group 4 exhibited normal luteal function. Luteal luteinizing hormone (LH) receptor levels were significantly higher on day 12 than day 4, and CL from groups with adequate CL (3 and 4) had significantly higher ¹²⁵I-human chorionic gonadotrophin (hCG)-binding levels than the three groups with inadequate CL on day 12. LH-binding affinity was unchanged. Exogenous ovine LH (10 [micro]g) in vivo on days 3 or 11 after ovulation induced a pulse of progesterone in ewes with adequate CL: however, ewes in Groups 1, 2 and 5 showed no significant response. Basal progesterone secretion in vitro was significantly greater on day 4 than on day 12. Maximal steroidogenic responses of adequate and inadequate CL to hCG and to dibutyryl cyclic-3',5'-AMP were similar at both stages of the luteal phase. However, the EC₅₀ for hCG on days 4 and 12 was 10-fold lower for groups with an adequate CL (0.1 IU hCG/ml) than for inadequate-CL groups (1 IU hCG/ml; P

  • corpora lutea induced by gonadotrophin releasing hormone treatment of anoestrous Welsh Mountain ewes reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro
    Reproduction, 2005
    Co-Authors: T. A. Bramley, D. Stirling, G. S. Menzies, David T. Baird
    Abstract:

    Seasonally anoestrous Welsh Mountain ewes received 250 ng gonadotrophin-releasing hormone (GnRH) every 2 h, with (Group 1; n = 13) or without (Group 2; n = 14) progesterone priming for 48 h. Fourteen control ewes (Group 3) were studied during the luteal phase in the breeding season. Animals in Group 4 (n = 12) received progesterone priming followed by 250 ng GnRH at increasing frequency for 72 h, while ewes in Group 5 (n = 13) were given three bolus injections of 30 [micro]g GnRH at 90-min intervals. All treatment regimens induced ovulation. However, only corpora lutea (CL) from ewes in Group 3 (breeding season) or Group 4 exhibited normal luteal function. Luteal luteinizing hormone (LH) receptor levels were significantly higher on day 12 than day 4, and CL from groups with adequate CL (3 and 4) had significantly higher ¹²⁵I-human chorionic gonadotrophin (hCG)-binding levels than the three groups with inadequate CL on day 12. LH-binding affinity was unchanged. Exogenous ovine LH (10 [micro]g) in vivo on days 3 or 11 after ovulation induced a pulse of progesterone in ewes with adequate CL: however, ewes in Groups 1, 2 and 5 showed no significant response. Basal progesterone secretion in vitro was significantly greater on day 4 than on day 12. Maximal steroidogenic responses of adequate and inadequate CL to hCG and to dibutyryl cyclic-3',5'-AMP were similar at both stages of the luteal phase. However, the EC₅₀ for hCG on days 4 and 12 was 10-fold lower for groups with an adequate CL (0.1 IU hCG/ml) than for inadequate-CL groups (1 IU hCG/ml; P <0.05). Thus, in addition to the well-characterized premature sensitivity of GnRH-induced inadequate CL to endometrial luteolysin, we have shown (1) a marked decrease in total number of cells in the CL, a profound reduction in vascular surface area, and a decrease in mean large luteal cell volume (with no change in large luteal cell numbers), (2) decreased luteal LH receptor and progesterone content compared with adequate CL and (3) that CL that were becoming, or were destined to become, inadequate failed to respond to ovine LH in vivo and were 10-fold less sensitive to hCG in terms of luteal progesterone secretion in vitro.

W Haresign - One of the best experts on this subject based on the ideXlab platform.

  • evaluating the effects of the c 1232g a mutation and tm qtl in texel Welsh Mountain lambs using ultrasound and video image analyses
    Small Ruminant Research, 2011
    Co-Authors: A Masri, N R Lambe, J M Macfarlane, S Brotherstone, W Haresign, L Bunger
    Abstract:

    Abstract The c.*1232G > A (MM) mutation in the myostatin gene and TM-QTL are two muscle-enhancing polymorphisms found on Chr 2 and Chr 18, respectively, in Texel sheep. Previous studies on purebred lambs and crossbred lambs out of Mule ewes showed that MM was associated with increased muscle mass and decreased fat content whereas heterozygous TM-QTL lambs had increased loin muscle ( M. longissimus lumborum , MLL) depth as measured by ultrasound and increased MLL weight. Welsh Mountain ewes, like Mule ewes, contribute significantly to UK slaughter lamb production from the UK sheep industry's stratified structure. Therefore, this study aimed to evaluate the direct effects of MM and TM-QTL in the genetic background of Texel × Welsh Mountain lambs. Four Texel sires, all MM carriers and two TM-QTL carriers, were used to inseminate Welsh Mountain ewes. Of the 175 lambs born, 130 could be classified for TM-QTL genotype [107 non-carriers (+/+), 23 heterozygous carriers (TM/+)] and 172 for MM genotype [15 non-carriers (+/+), 129 heterozygous carriers (MM/+), 28 homozygous carriers (MM/MM)]. All lambs were weighed at 8 and ∼23 weeks of age and were ultrasound scanned before being slaughtered at ∼24 weeks of age. All carcasses were graded for conformation and fat class, based on Meat and Livestock Commission (MLC) classification scores, and then scanned using a video image analysis (VIA) system to predict weight of carcass primal cuts and trimmed primal cuts, muscularity traits and carcass shape traits. Carrying two copies of MM was associated with a significant positive effect on 8 weeks weight, a negative effect on ultrasound fat depth and a substantial decrease in MLC-fat score. Two copies of MM also had a strong positive impact on VIA-estimated weight of the hind leg, chump and loin primal cuts, as well as the muscularity of the hind leg and loin regions with greater loin muscle width, depth and area. Homozygous MM carrier lambs had significantly wider carcasses across the shoulders, breast and hind legs and greater areas of the back view of the carcass when measured by VIA. Leg and carcass compactness were also significantly associated with the presence of two copies of MM. However, lambs carrying a single copy of MM were not significantly different to non-carriers in any of the traits measured. TM-QTL significantly increased ultrasound muscle depth and TM-QTL carriers had significantly greater loin muscle width and area measurements. Carcass weight did not differ significantly between genotypic classes for MM or TM-QTL. These results agree in general with other reports of the effects of MM and TM-QTL, in both direction and magnitude, on carcass traits.

  • Evaluating the effects of the c.*1232G > A mutation and TM-QTL in Texel × Welsh Mountain lambs using ultrasound and video image analyses
    Small Ruminant Research, 2011
    Co-Authors: A Masri, N R Lambe, J M Macfarlane, S Brotherstone, W Haresign, L Bunger
    Abstract:

    Abstract The c.*1232G > A (MM) mutation in the myostatin gene and TM-QTL are two muscle-enhancing polymorphisms found on Chr 2 and Chr 18, respectively, in Texel sheep. Previous studies on purebred lambs and crossbred lambs out of Mule ewes showed that MM was associated with increased muscle mass and decreased fat content whereas heterozygous TM-QTL lambs had increased loin muscle ( M. longissimus lumborum , MLL) depth as measured by ultrasound and increased MLL weight. Welsh Mountain ewes, like Mule ewes, contribute significantly to UK slaughter lamb production from the UK sheep industry's stratified structure. Therefore, this study aimed to evaluate the direct effects of MM and TM-QTL in the genetic background of Texel × Welsh Mountain lambs. Four Texel sires, all MM carriers and two TM-QTL carriers, were used to inseminate Welsh Mountain ewes. Of the 175 lambs born, 130 could be classified for TM-QTL genotype [107 non-carriers (+/+), 23 heterozygous carriers (TM/+)] and 172 for MM genotype [15 non-carriers (+/+), 129 heterozygous carriers (MM/+), 28 homozygous carriers (MM/MM)]. All lambs were weighed at 8 and ∼23 weeks of age and were ultrasound scanned before being slaughtered at ∼24 weeks of age. All carcasses were graded for conformation and fat class, based on Meat and Livestock Commission (MLC) classification scores, and then scanned using a video image analysis (VIA) system to predict weight of carcass primal cuts and trimmed primal cuts, muscularity traits and carcass shape traits. Carrying two copies of MM was associated with a significant positive effect on 8 weeks weight, a negative effect on ultrasound fat depth and a substantial decrease in MLC-fat score. Two copies of MM also had a strong positive impact on VIA-estimated weight of the hind leg, chump and loin primal cuts, as well as the muscularity of the hind leg and loin regions with greater loin muscle width, depth and area. Homozygous MM carrier lambs had significantly wider carcasses across the shoulders, breast and hind legs and greater areas of the back view of the carcass when measured by VIA. Leg and carcass compactness were also significantly associated with the presence of two copies of MM. However, lambs carrying a single copy of MM were not significantly different to non-carriers in any of the traits measured. TM-QTL significantly increased ultrasound muscle depth and TM-QTL carriers had significantly greater loin muscle width and area measurements. Carcass weight did not differ significantly between genotypic classes for MM or TM-QTL. These results agree in general with other reports of the effects of MM and TM-QTL, in both direction and magnitude, on carcass traits.

  • Multiple Ovulation and Embryo Transfer in Hill Ewes
    Proceedings of the British Society of Animal Production (1972), 1994
    Co-Authors: W Haresign, B. Merrell, R.i.w.a. Richards
    Abstract:

    A breed improvement programme has been initiated at both ADAS Redesdale (Scottish Blackface) and ADAS Pwllpeiran (Welsh Mountain) to improve carcass conformation of hill ewes. From a base population of 1100 Welsh Mountain and 1600 Scottish Blackface ewes, nucleus flocks of 60 ewes have been established. Selection of ewes into the nucleus flock at each site has been based on their ability to consistently produce wether lambs crops with good conformation and above average carcass weights when selected for slaughter at a fat class 2/3L. The next objective is to replicate these ewes through multiple ovulation and embryo transfer (MOET) since theoretical studies (Smith, 1986) indicate that this can substantially increase the rates of genetic improvement through the female line. However, to date little work has been conducted to determine whether this technology can be successfully applied to hill sheep maintained in harsh hill environments in the UK, and this formed the basis of the current study.

  • Multiple Ovulation and Embryo Transfer in Hill Ewes: Effects of Mating System on Embryo Quality, and its Relationship With Pregnancy Rates
    Proceedings of the British Society of Animal Production (1972), 1994
    Co-Authors: W Haresign, B. Merrell, R.i.w.a. Richards
    Abstract:

    A breed improvement programme has been initiated at both ADAS Redesdale (Scottish Blackface) and ADAS Pwllpeiran (Welsh Mountain) to improve carcass conformation of hill ewes. At each site a nucleus flock of 60 ewes has been established and this is being replicated using multiple ovulation and embryo transfer (MOET). The project provides an opportunity to investigate factors affecting the success of MOET under field conditions with an unusually large population of animals maintained under a common management and environment at each site. The current results relate to the effect of mating system on embryo quality, and the relationships between embryo quality and embryo survival.

D. Stirling - One of the best experts on this subject based on the ideXlab platform.

  • Corpora lutea induced by gonadotrophin-releasing hormone treatment of anoestrous Welsh Mountain ewes: reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro
    Reproduction, 2020
    Co-Authors: T. A. Bramley, D. Stirling, G. S. Menzies, David T. Baird
    Abstract:

    Seasonally anoestrous Welsh Mountain ewes received 250 ng gonadotrophin-releasing hormone (GnRH) every 2 h, with (Group 1; n = 13) or without (Group 2; n = 14) progesterone priming for 48 h. Fourteen control ewes (Group 3) were studied during the luteal phase in the breeding season. Animals in Group 4 (n = 12) received progesterone priming followed by 250 ng GnRH at increasing frequency for 72 h, while ewes in Group 5 (n = 13) were given three bolus injections of 30 [micro]g GnRH at 90-min intervals. All treatment regimens induced ovulation. However, only corpora lutea (CL) from ewes in Group 3 (breeding season) or Group 4 exhibited normal luteal function. Luteal luteinizing hormone (LH) receptor levels were significantly higher on day 12 than day 4, and CL from groups with adequate CL (3 and 4) had significantly higher ¹²⁵I-human chorionic gonadotrophin (hCG)-binding levels than the three groups with inadequate CL on day 12. LH-binding affinity was unchanged. Exogenous ovine LH (10 [micro]g) in vivo on days 3 or 11 after ovulation induced a pulse of progesterone in ewes with adequate CL: however, ewes in Groups 1, 2 and 5 showed no significant response. Basal progesterone secretion in vitro was significantly greater on day 4 than on day 12. Maximal steroidogenic responses of adequate and inadequate CL to hCG and to dibutyryl cyclic-3',5'-AMP were similar at both stages of the luteal phase. However, the EC₅₀ for hCG on days 4 and 12 was 10-fold lower for groups with an adequate CL (0.1 IU hCG/ml) than for inadequate-CL groups (1 IU hCG/ml; P

  • corpora lutea induced by gonadotrophin releasing hormone treatment of anoestrous Welsh Mountain ewes reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro
    Reproduction, 2005
    Co-Authors: T. A. Bramley, D. Stirling, G. S. Menzies, David T. Baird
    Abstract:

    Seasonally anoestrous Welsh Mountain ewes received 250 ng gonadotrophin-releasing hormone (GnRH) every 2 h, with (Group 1; n = 13) or without (Group 2; n = 14) progesterone priming for 48 h. Fourteen control ewes (Group 3) were studied during the luteal phase in the breeding season. Animals in Group 4 (n = 12) received progesterone priming followed by 250 ng GnRH at increasing frequency for 72 h, while ewes in Group 5 (n = 13) were given three bolus injections of 30 [micro]g GnRH at 90-min intervals. All treatment regimens induced ovulation. However, only corpora lutea (CL) from ewes in Group 3 (breeding season) or Group 4 exhibited normal luteal function. Luteal luteinizing hormone (LH) receptor levels were significantly higher on day 12 than day 4, and CL from groups with adequate CL (3 and 4) had significantly higher ¹²⁵I-human chorionic gonadotrophin (hCG)-binding levels than the three groups with inadequate CL on day 12. LH-binding affinity was unchanged. Exogenous ovine LH (10 [micro]g) in vivo on days 3 or 11 after ovulation induced a pulse of progesterone in ewes with adequate CL: however, ewes in Groups 1, 2 and 5 showed no significant response. Basal progesterone secretion in vitro was significantly greater on day 4 than on day 12. Maximal steroidogenic responses of adequate and inadequate CL to hCG and to dibutyryl cyclic-3',5'-AMP were similar at both stages of the luteal phase. However, the EC₅₀ for hCG on days 4 and 12 was 10-fold lower for groups with an adequate CL (0.1 IU hCG/ml) than for inadequate-CL groups (1 IU hCG/ml; P <0.05). Thus, in addition to the well-characterized premature sensitivity of GnRH-induced inadequate CL to endometrial luteolysin, we have shown (1) a marked decrease in total number of cells in the CL, a profound reduction in vascular surface area, and a decrease in mean large luteal cell volume (with no change in large luteal cell numbers), (2) decreased luteal LH receptor and progesterone content compared with adequate CL and (3) that CL that were becoming, or were destined to become, inadequate failed to respond to ovine LH in vivo and were 10-fold less sensitive to hCG in terms of luteal progesterone secretion in vitro.