Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Filters

1991 - 19973

Settings

Subject: search.filters.subject.Embryo transfer

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    A study of the results of an embryo transfer programme conducted during two seasonal periods using five imported breeds of sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University
    (Massey University, 1991) Greaney, Kenneth Barry
    The overall objective of this trial was to compare embryo transfer results from two seasonal periods (out-of-season vs in-season) in order to determine the effect of the season on the different parameters of reproductive performance such as; theincidence of oestrus, ovarian response to exogenous gonadotrophins, fertilisation rates and the number of lambs born per donor ewe programmed and flushed. Five breeds of imported sheep (Danish Texel {DT}, Finnish Texel {FT}, Gotland Pelt {GOT), Oxford Down {OXD}, and the White Headed Marsh {WHM}) consisting of two age groups (14-16 month-old and 26-28 month-old) in a commercial embryo transfer programme (LambXL, Manawatu) were used. A total of 553 ewes out-of-season and 234 ewes in-season were studied. Two data sets were selected from these seasonal groups; (1) The random data set. (2) The repeat data set, which consisted of the same donor ewes in each seasonal group. Oestrous synchronisation was attempted with a double CIDR-G regime and a super-ovulatory treatment consisting of an initial PMSG injection (200-300IU) and a series of six descending doses of FSH-P (total dose 24-36mg). The ewes were inseminated intra-uterine with fresh diluted semen from a ram of the same breed on the basis of oestrous detection. Embryo recovery was attempted on day 6.5-7 after oestrous detection using a laparoscope-aided uterine flush technique. Two embryos were transferred to each synchronised recipient ewe within two hours of recovery. The incidence of oestrus for the out-of-season and in-season groups was 93.3% and 100%, for the random data set compared to 93.9% and 100% for the repeat data set, respectively. The ovulatory response to the super-ovulatory treatments was significantly affected by the interaction of the breed and age of the donor in the random data set, but the repeat data set ovulation rate was not significantly affected by any of the variables recorded in this study. This interaction was attributable to the GOT breed having a higher ovulation rate in the older age group relative to the younger age group which was the reverse trend exhibited by the remaining breeds. However, there was an overall tendency for the out-of-season ovulation rate to be higher than that in-season, 7.64CL vs 6.60CL for the random data set and a difference (out-of-season - in-season) of +2.86CL was recorded for the repeat data set. The embryo recovery rates were 53.4% out-of-season and 53.5% in-season for the random data set and a difference of -0.7 percentage points was recorded for the repeat data set. The fertilisation rate was not significantly atfected by the season with 75.5% out-of-season and 65.7% in-season from the random data set and a difference of -4.5 percentage points was recorded for the repeat data set. The yield of good quality transferable embryos was significantly affected by the season with 78.2% out-of-season and 83.7% in-season from the random data set but the repeat data set was not significantly affected by the season with a difference of -11.0 percentage points. The embryo survival rate to birth was not significantly different for the two seasonal periods with 66.3% out-of-season and 52.4% in-season of the embryos surviving to birth for the random data set and a difference of +9.7 percentage points was recorded for the repeat data set. This resulted in an average of 1.66 lambs born per donor ewe programmed out-of-season, which was not significantly different from 1.00 lambs born in-season for the random data set compared to a ditference of +0.1 1 lambs born per donor ewe programmed in the repeat data set. This work clearly demonstrates the inter-dependence of several factors affecting the number of lambs born per donor ewe in an embryo transfer programme. However it is concluded that out-of-season embryo transfer is as effective as that conducted in-season, under these embryo transfer conditions.
  • Thumbnail Image
    Item
    A study of commercial embryo transfer programmes conducted with Texel and Awassi sheep : a thesis presented in partial fulfilment of the degree of Master of Agricultural Science in Animal Science at Massey University
    (Massey University, 1997) Pavitt, Andrew Edward Drummond
    The results of two commercial embryo transfer (ET) programmes conducted in Central Huwkes Bay, comprising 93 Texel and 78 Awassi donor ewes, were analysed to identify variables that affect the success of commercial ET programmes. The production of high quality embryos for export was the primary objective in the Texel programme, while the rapid multiplication of the Awassi was the sole purpose of the Awassi programme. Reproductive parameters such as; ovarian response to exogenous gonadotrophins, recovery and fertilisation rate of ova, yield of good quality embryos and embryo survival rate to scanning and birth were evaluated. The influence of age, ovulatory response, repeated flushing, the number of corpora lutea in recipient ewes and donor surgeon, on the reproductive parameters, were assessed. The Texel ewes were all purebred consisting of two-tooth and four-tooth animals. The Awassi ewes were either three-quarter or purebred, and included both ewe hoggets and mixed age ewes. Synchronisation of oestrus was attempted using a double CIDR-GTM regime. The super ovulatory programme differed in each breed but consisted of a series of FSHp injections in combination with PMSG. The ewes were inseminated intra-uterine with fresh diluted semen from a ram of the same breed after detection of oestrus. Embryo recovery was attempted 6-6.5 days after insemination using a standard flushing technique in which the oviducts and uterus were exposed by mid-ventral laparotomy. Two or three embryos were transferred into each recipient ewe within 1.5 hours (Texel) and 4 hours (Awassi) of recovery. Ovarian response to superovulatory treatment was not significantly affected by any of the variables recorded in this study, although the Texel programme provided a higher ovulatory response than the Awassi programme (8.89 CL vs 7.08 CL). The embryo recovery rates were 71.8% for the Texel and 78.1% for the Awassi sheep. Age of the donor ewes significantly affected (p=0.006) recovery rate of ova in the Awassi sheep, adult ewes and ewe hoggets recorded recovery rates of 90.7% and 65.2%. Fertilisation rate was not affected by any of the factors studied with 94.6% and 77.6%, of ihe Texel and Awassi ova, being fertilised. The overall yield of good quality embryos was 91.6% for the Texel and 80.1% for the Awassi. The yield of good quality embryos was significantly affected (p=0.03) by age in the Awassi, 87.5% of adult embryos and 64.4% of ewe hogget embryos were of good quality. Survival rates in the Awassi data set were significantly affected by the lower scanning and birth rates of the Awassi ewe hoggets than Awassi ewes (43.8% vs 65.9%: p=0.02) and (39.3% vs 59.4%: p=0.03) respectively. Each Texel donor ewe produced, on average, 3.89 embryos that were of sufficient quality to be preserved and therefore not transferred, resulting in 0.70 lambs being born per donor ewe in the Texel programme. The Awassi programme produced 2.10 lambs donor per ewe, however, this was significantly affected (p=0.03) by the age of the donor ewes, with adult ewes produced an average of 2.7 lambs per donor, and ewe hoggets, 1.2 lambs per donor. This work demonstrated the variable nature of embryo transfer programmes as well as the difficulty in achieving acceptable results from ewe hoggets. The Texel and adult Awassi results compared favourably to the other published reports and illustrate that on-farm commercial embryo transfer can provide acceptable results.
  • Thumbnail Image
    Item
    Investigations into procedures for the implementation of a multiple ovulation and embryo transfer scheme using ewe lambs: a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1991) Rangel-Santos, Raymundo
    Three trials using 6-7 month-old Romney ewe lambs and adult ewes were conducted to evaluate the feasibility of implementing a juvenile MOET scheme. Older lambs were used to evaluate ways of improving the ovulation rates in 3 additional trials, one of them involved Booroola-cross lambs. Studies were also carried out to develop and evaluate a technique for splitting sheep embryos, and these were transferred to recipient ewes. In the three trials involving superovulation and transfer a range of gonadotrophin treatments were used. The more highly purified preparations (FSH-P, Ovagen) gave lower responses compared with PMSG (1.78, 1.06 vs 4.18 respectively in Trial 3, P<0.01). Ovulation rate of ewe lambs relative to adult ewes in the 3 trials were respectively 1.20 vs 2.00 (P<0.01), 4.18 vs 6.35 and 1.61 vs 3.15. Overall, administration of GnRH did not significantly increase the ovulation rates, although lambs treated with PMSG + GnRH tended to give higher responses. Egg recovery was higher in most cases in adults than in lambs (91% vs 55%, P<0.01; 72% vs 47%. P<0.01; 34% vs 43%, for trials 1, 2 and 3 respectively). Fertilization rate in trial 1 was lower in lambs than in adults (50% vs 82%, P<0.05) but not different in trials 3 and 5, probably due to the use of intrauterine insemination. Ovulation rate was not improved by treating lambs at 8-9 months of age or by administering PMSG 2 or 4 days before sponge removal. Ovulation rates following gonadotrophin stimulation were higher in androstenedione-immunized ewe lambs than in non-immunized ewe lambs (2.22 vs 1.59. P<0.05). Booroola-cross lambs treated at 6-7 months of age gave considerably higher ovulation rates compared to those recorded in Romney lambs from another experiment conducted at the same time (3.79 vs 1.61). Lower embryo survival and incidence of twins were found for demi-embryos generated from 9-10 month-old lambs compared to those obtained from 24 months or older animals. Higher pregnancy rate and demi-embryo survival were found when bisecting blastocysts rather than morulae harvested in the same flush. A deterministic model incorporating parameters provided by the study showed that the limited number of lambs generated from lamb donors restricted the improvement in genetic progress.