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    Genomic selection for traits of economic importance in sheep : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Breeding and Genetics at Massey University, Manawatū, New Zealand
    (Massey University, 2014) Lepori Honeyman, Alfredo Andres
    The main objective of this thesis was to analyse the inclusion of genomic information of production traits into a multitrait sheep breeding programme evaluated for 20 years using deterministic and stochastic simulation models. The breeding objective was to reduce faecal egg score (FES), decrease yearling weight (YW) and increase 160 days lamb carcass weight (CW). The selection criteria included 160 days live weight (instead of CW) plus YW and FES. The first study developed a stochastic model selecting animals based on their individual breeding values estimated using best linear unbiased predictor (BLUP) procedure with a multitrait animal model. The model was validated using a deterministic multitrait selection index; obtaining similar prediction responses for breeding objective and selection criteria traits. The second study deterministically evaluated the inclusion of genomic information explaining different proportions of CW and YW genetic variances into a selection index. Under the same selection scheme a selection index having only genomic information obtained lower accuracies and genetic gains compared to a selection index considering phenotypic information. If shorter generation intervals are implemented, a selection index including phenotypic and genomic information explaining low proportions of the trait's genetic variance could achieve higher genetic and economic gains. The third study evaluated genetic responses of a stochastically modelled breeding flock selecting ewes based on BLUP estimated breeding values and selecting rams based on genomic breeding values (GBV) for CW. The fourth study evaluated accuracy of prediction of CW GBV using the same simulated model. Carcass weight GBVs were calculated in a validation population using single nucleotide polymorphism (SNP) effects from a training population. The further apart the genetic relationship between these two populations, lower the GBV accuracy. Resultant accuracies depended on the proportion of total genetic variance explained by genomic information and also the variance accounted by each SNP, therefore an appropriate GBV estimating method has to be chosen to achieve accuracies as high as possible. Stochastic models proved to be more versatile for managing data, also showing variation of the genetic responses. In contrast, deterministic models were faster regarding computer processing times. The study proved that a breeding programme combining GBV and BLUP estimated breeding values can increase genetic responses by selecting animals at early stages of life.
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    A study of ovulation and early prenatal mortality in the New Zealand Romney ewe : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science, Massey University
    (Massey University, 1965) Cumming, Ian A
    The production of a lamb is the end result of a series of events the formation of fertile ova and spermatozoa to the independent existence of the lamb. The main essentials for high rates of reproduction in sheep are a high proportion of multiple ovulations, successful fertilization and gestation,and and a high rate of survival of new born lambs. Fertility is a qualitative term denoting ability to produce young, the quantitative equivalent being fecundity which denotes the number of young produced per individual (Asdell,1946). The expression prenatal mortality is used to cover all loss between ovulation and parturition being the discrepancy between the number of ova and the number of young born alive. The subject of prenatal mortality has been reviewed with reference to farm animals by Laing (1952), Casida (1953,1956), Robinson ( 1957), and Hanly (1961). [From the introduction]
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    A study of some factors affecting reproductive performance in New Zealand Romney and Border Leicester X Romney two-tooth ewes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University
    (Massey University, 1971) Larsen, Warren Arthur
    The reproductive performance of tho ewe is a key factor determining flock productivity and also the rate of genetic improvement possible within flocks. The lambing percentage of Romney sheep in New Zealand is variable but generally unsatisfactory. Crossbreeding with Border Leicesters may provide a method of rapidly improving lamb production. Extensive comparisons of Romney and Border Leicester X Romney (BLX) sheep have been conducted at Whatawhata Hill Country Research Sation (1954 - 1967) and Lincoln College (1952 - 1958). Results were in close agreement. On a per ewe basis, the crossbred was superior to the Romney in growth rate as a lamb and hogget, and in mature bodyweight. In addition, the lambing performance of the crossbred was at least 20 higher, and the growth rate of its lambs about 5% better, than the Romney.
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    A study on the breeding performance of Romney and Border Leicester cross Romney ewe lambs after CIDR treatment : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University, Palmerston North, New Zealand
    (Massey University, 1987) Chun, Bae Seok
    The reproductive performance of 117 Border-Leicester X Romney (BLX) and 91 Romney ewe hoggets in 1984 and 108 BLX and 101 Romney in 1985, was studied after treatment with controlled internal drug releasers (CIDRs) containing progesterone or with polyurethane sponges containing medroxyprogesterone acetate (MAP). To induce and synchronise oestrus at the beginning of the breeding season, progestagens were administered for 11-12 days. The animals were joined with teaser rams or with entire rams and data collected on the occurrence and synchronization of oestrus, conception and lambing performance. In 1986, 36 lambs of each of the Romney or BLX genotypes were used in a study to determine the time of ovulation after treatment with CIDRs either with or without 200 i.u. PMSG injected at CIDR withdrawal. Laparoscopics were carried out one or more times at 54,60,66,72 hours and one week after CIDR withdrawal to determine the occurrence of ovulation. The release of progesterone from the CIDR was monitored in blood samples from entire animals and from ovariectomised animals during treatment and after withdrawal of the CIDRs. Following progestagen withdrawal, 69% and 42% of sponge- treated hoggets and 45% and 40% of CIDR-treated animals were in oestrus over 5 days in the two years,respectively. In 1986, following progestagen withdrawal, 61% and 83% of animals came into oestrus within 3 days in CIDR- and CIDR + PMSG- treated ewe lambs. The mean time of ovulation vas 67 h and 65 h in CIDR and CIDR + PMSG treated animals, respectively. The incidence of multiple ovulation was similar in CIDR- (15%) and Sponge-treated (20%) ewe lambs. Although the injection of a small amount of PMSG caused a higher incidence of multiple ovulation than in CIDR-treated ewe lambs, the difference was not significant. The conception rate was higher in animals treated in 1984 than in the next year (69% v 49%). Treatment or breed differences in conception were not significant but in 1985 the BLX animals had a reduced conception rate of only 38%; the Breed X Year interaction was significant (P< 0.05). There were only a few multiple births recorded and the gestation length was not affected by treatment. Significant birth weight effects due to year and breed were apparent, but only a difference due to year occurred in the weaning weights. The fleece weights recorded at one year age were not influenced by the treatments, but year effects were important. Progesterone levels in blood plasma of ovariectomised ewe lambs reached a maximum by 24 h after CIDR insertion, then declined gradually and an abrupt fall resulted soon after CIDR withdrawal. In the entire lambs with CIDRs the levels of progesterone remained high until withdrawal and then fell to basal levels consistent with ovulation. After this the levels rose and were similar to that in animals with a corpus luteum of a natural oestrous cycle. It was concluded that CIDR treatment can induce earlier breeding among ewe lambs and that the induced ovulation resulted in a normal corpus luteum. The pregnancy rate after CIDR treatment was influenced by year effects and this was probably associated with differences in liveweight among the ewe lambs.
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    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.
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    A study of the ovarian response of New Zealand Romney ewes sequentially superovulated with pregnant mare's serum gonadotrophin : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University
    (Massey University, 1973) Clarke, Iain James
    A series of experiments investigated the nature and causes of ovarian refractoriness in ewes sequentially treated with Pregnant Mare's Serum Gonadotrophin (P.M.S.G.). 70 ewes were subjected to the following treatments over 3 oestrous cycles of the 1972 breeding season:- 1. Injectcd with P.M.S.G. at each of 3 cycles (cycles 1,2 and 3); 2. Two injections of P.M.S.G. (at cycles 1 and 3) separated by a nornal oestrous cycle; 3. Injected with P.M.S.G. at two successive cycles (cycles 2 and 3); 4. Injected at 1 cycle only (cycle 3). These treatments were replicated at 1000 i.u. and 1500 i.u. P.M.S.G. and 9 ewes acted as an uninjected control group. The ewes were blood sampled and slaughtered at the end of these treatments and ovulation data were obtained by recovery of the reproductive tracts. The terminal ovulation rates showed that ewes were refractory to a second injection of P.M.S.G. and this condition persisted. The refractoriness was to some extent alleviated by the spacing of injections (Treatment 2 above). Biological Inhibition Tests (using mice) analysed the plasma of the above ewes for evidence of anti-gonadotrophins. Although such factors were not detected in the blood of these ewes, the test did reveal antibody production against P.M.S.G. in the plasma of a further group of ewes which had been chronically treated with the hormone for 6 weeks. It was concluded that ovarian refractoriness, which is rapidly attained in sequentially treated ewes, is not due to the development of serological antibodies against the exogenous gonadotrophin. Another experiment, carried out early in the 1973 breeding season, investigated ovarian follicle development in 30 owes whlch were sequentially treated with P.M.S.G. for up to 3 oestrous cycles. Ewes were laparotomised or killed on Day 10 of the oestrous cycles following treatment and measurements on follicle development were taken. A group of control ewes were observed at a similar time to the treated ewes. Counts on ovarian surface follicles dlffered litt1e between treated and control ewes, at each of the observations. However, the ovaries of slaughtered ewes were sectioned to allow estimation of total ovarian follicular populations and to make some assessment of follicular atresia. Ewes slaughtered after 1 injection of P.M.S.G. had lower numbers of normal antral follicles per ovary than did control ewes or ewes observed at similar times after 2 or 3 injections. It was suggested that exhaustion of ovarian follicular populations may precipitate a refractory condition but that this condition persists because of an endogenous hormonal imbalance. Further work should be done to investigate this latter possibility.
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    The estimation of genetic and phenotypic parameters for a synthetic lean meat and wool sheep breed : a thesis presented in partial fufilment [i.e. fulfilment] of the requirements for a degree of Master of Agricultural Science at Massey University
    (Massey University, 1989) Southey, Bruce Robert
    A study of the inheritance and interrelationships between wool, growth and carcass traits was carried out as part of the development of a large lean white-faced sire breed. Cross-bred progeny, from three sire breeds (Romney, Dorset, and Border Leicester) mated to Romney ewes, provided information on carcass fatness and composition, liveweight, ultra-sonic backfat depth, fleeceweight and objective measures of fleece characteristics. An overall total a total of 28 sires and 765 progeny were used to collect this information. The analysis of half-sib records was carried out under an assumption of positive assortive mating on ultra-sonic backfat depth. It was considered that any bias, relative to random mating, was minimal due to incomplete assortment, dominance, epistasis and crossbreeding influences. It was assumed that the progeny were only half-sibs in relation to breed, and thus the between-breed component only estimated one-quarter of the between-breed variance. Further, the sires were nested within their respective breeds. The data corrected for the significant non-genetic effects before the variance and covariance components were estimated. In general, the estimates of the Within-breed heritability for the wool and growth traits ranged from 0.1 to 0.6 and were similar to literature values. The carcass estimates were higher than literature values in most cases. The incorporation of the between-breed component resulted in the between-breed heritability being larger in magnitude. This was may of been due to non-additive genetic effects, such as heterosis, in the between-breed component. The ratio of the between-breed genetic variance to the total genetic variance indicated that there was large between-breed variation in liveweight and wool traits and sma1l variation in the carcass traits. The total genetic and total phenotypic correlations presented here suggest that selection for lean growth and wool production can be accomplished by the joint selection of liveweight and greasy fleeceweight. Expected correlated responses in the other traits would include: a)increase liveweight and fleeceweight at all ages, increase ultra-sonic fat depth, GR measurerment, lean content, clean fleeceweight, staple length, mean fibre diameter, clean scoured yield, and b)decrease the carcass C measurement, decrease bone and fat contents, and loose wool bulk. Selection against ultra-sonic backfat depth would result in leaner animals at a constant weight. But the moderately positive correlations with liveweight and fleeceweight would appear to negate the associated advantage of a reduction in carcass fatness.
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    Studies on the in vivo cleavage and the in vitro culture of New Zealand romney sheep ova : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
    (Massey University, 1967) Tervit, Harry Robin
    The purpose of this present study was to observe the cleavage of fertilised Romney ewe ova in vivo and to compare this with cleavage of ova cultured in vitro. A method of long term in vitro culture of ova was developed and the technique of ovum transplantation used to test ovum viability.
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    A study of some aspects of sexual behaviour in the sheep (Ovis aries) : a thesis in partial fulfilment of the requirements for the degree of Master of Science in Zoology at Massey University
    (Massey University, 1973) Ross, Kenneth Richard
    Studies of sheep mating behaviour have, in the past tended to concentrate on the statistical parameters associated with mating behaviour and the oopulatory act (Bermant et al., 1969,a,b,c; Haughey, 1959; Hulet et al., 1962,a,b,c; Inkster,1957; Lambourne,1956; Lindsay and Ellsmore, 1972; Lindsay and Robinson,196l; Pepelko and Clegg,l965) and have all but ignored a close analysis of the motor acts of the ram and the ewe and their relationship to one another. The result is a body of knowledge having immediate application, especially in efficiency studies, but lacking a firm foundation so that studies could still be found as recently as 1967 on sheep mating behaviour, that gave brief descriptions of some motor acts that were, and remained, unnamed (Mattner et al.,1967). Banks (1964) drew attention to this situation and although his study did much to rectify this, it was by no means complete. The acoount of Hafez et al. (1969) can be viewed in much the same light - though providing more descriptive information than many other investigations (Bourke, 1967; Lindsay,1966; Lindsay and Fletcher, 1972) including several of his own (Hafez,1951; Hafez, 1952), certain basic inadequacies were still apparent. The inadequacies of previous descriptive studies became especially evident during the preliminary stages of the present study, when it became obvious that the sexual behaviour of sheep was much more complex than the earlier studies had indicated.
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    A study of regional differences in within-flock sources of variation in Sheeplan records of production traits for Coopworth sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
    (Massey University, 1985) Rendel, John Martin
    Perforrnance records on 219, 000 ewes and 231,000 lambs from 48 Coopworth flocks were obtained from Sheeplan files. The flocks were divided into 5 climatologically similar regions: Northland; north of Taupo excluding Northland; reminder of the North Island; the South Island north of Palmerston, excluding the West Coast; the South Island south of Palmerston. Flock records were edited in an effort to remove recording errors. Within-flock environmental estimates were obtained using ordinary least squares procedures for continuous characters or iterative weighted least squares for binomial characters. The within-flock estimetes were weighted by the inverse of their standard errorr's and weighted means of the regional and national fixed effects were obtained. Paternal half-sib heritability estimates were obtained for each flock. There were few significant differences in the environmental estimates between regions. The traits examined (with the average of the heritability estimates) were: weaning weight (0.17); ram autumn liveweight (0.24); ewe autumn liveweight (0.26); ram winter liveweight (0.26); ewe winter liveweight (0.31); ram spring liveweight (0.29); ewe spring liveweight (0.34); ram hogget fleece weight (0.29); ewe hogget fleece weight (0.33); survival of all lambs (0.04); single lamb survival (0.05) and multiple lamb survival (0.05); proportion of a ewe's lambs surviving (0.04); number of lambs born to a ewe present at mating (0.12); number of lambs weaned per ewe lambing (0.07); given a ewe lambed, did she bear multiples (0.14); weight of lamb weaned per ewe rearing lambs (0.10). Selection and non-random mating may have biased the estimates.