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    A study of the acceptability of Holcus spp. to Perendale sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University
    (Massey University, 1979) Cameron, Nicholas Evan
    Various characters are reputed to reduce the acceptability of Yorkshire fog grass (Holcus lanatus) to sheep. The relative importance of these characters in determining the acceptability of Yorkshire fog to sheep was investigated in summer, autumn, and early-winter of 1978, using standardised regression, and based upon a phenotypically diverse collection of spaced plants from fifty-three seed populations. A clump defoliation score was used to assess sheep preference. Cluster analysis of ratios of the standardised partial regression coefficients from individual genotype populations generally confirmed the results obtained from the standardised partial regression coefficient ratios of pooled genotype populations. Sheep rejected plants exhibiting a high proportion of inflorescences, dead leaf and sheath material and crown rust infection. The presence of inflorescences and crown rust were respectively 1.5 and 0.86 times as important as clump greenness over all genotype populations, in the summer period. Leaf pubescence was only 0.13 times as important as clump greenness and was therefore considered relatively unimportant in determining sheep preference. Leaf tensile strength, leaf width, clump height and diameter, clump erectness, leaf flavanol level and soluble sugar level, were also considered unimportant in this study, and ranged from 0.57 to 0.019 times as important as clump greenness in determining sheep preference. However only 20-25% of the variation in sheep preference was explained by the characters examined in the three seasons of this study. The unexplained variation may have been due to a high level of amongst sheep preference variance or to unassessed plant characters. The phenotypic variation of each character was partitioned using a split-plot-in-time model. Broad-sense heritability estimates for all characters examined were low and ranged from 34% to 0.4%. It was suggested from these results that the acceptability of Yorkshire fog grass to sheep, by reduction of inflorescences and crown rust infection, and by removal of excessive dead leaf and sheath material, was largely under the control of grazing management (i.e. an aspect of the environment). However, some progress might be achieved by selection and breeding for genotypes with reduced levels of inflorescences (h2= 34%) and crown rust infection (h2= 29%).
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    Studies of the flock mating performance of Booroola merino crossbred ram lambs, and the foot "conditions" in Booroola merino crossbreds and Perendale sheep grazed on hill country : 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, 1983) Alwan, Mohammed Taha
    Two studies using the Booroola Merino crossbred animals were conducted. In the first, the flock mating performance of Booroola Merino-Romney crossbred ram lambs mated to Perendale ewes was examined. The second study comprised observations on the incidence of foot "conditions" in young Booroola Merino crossbreds and Perendale sheep grazed on hill country. MATING PERFORMANCE Eighteen Booroola Merino x Romney ram lam's (6 control, 12 mating group) were selected according to weaning weight, fleece characteristics and general body condition. Nine ram lambs were exposed to ewes prior to mating for two weeks (trained) and nine kept separate from any ewes (untrained). The ram lambs of the mating group (6 trained, 6 untrained) were allocated to six groups of ewes which were "single-sire" mated. Groups 1, 2, 3, 4 comprised 140 ewes each and Groups 5 and 6 comprised 100 e'\.;res each. The ram lambs were changed after eight, eight, seven and seven days of mating, Periods P1, P2, P3 and P4 respectively, and a total of 12 "single-sire" mating groups generated. All ram lambs produced a satisfactory semen sample before joining with the flocks. Mating commenced on 30 March 1981. The flock mating performance of each ram lamb was assessed by recording the percentage of ewes raddled, percentage of ewes returning to service, percentage of pregnant ewes, percentage of ewes lambing, docking rate and weaning rate. Differences among each of these parameters were attributed to various factors. Trained and untrained ram lambs were similar in most of the observed parameters of flock mating performance. There were no differences between individual ram lambs within each sire-group (trained or untrained) in mating performance. There were differences in the percentage of ewes raddled between first and second oestrous cycle of mating. Live weights of the ram lambs were measured from weaning (December 1980) until the end of the trial (December 1981), at weekly intervals during the mating periods and at monthly intervals during the post-mating and post-shearing periods. There was little loss in the mean live weight of the mating group ram lambs after P1. Overall the live weights of both groups increased consistently throughout the trial. Semen samples (collected by electro-ejaculation) from the ram lambs of the mating group were microscopically examined for general motility after each mating period at least for three days. Recovery from mating exhaustion occurred four and six days after P1 and Pz respectively, while three and two days were required after P3 and P4 respectively. Semen samples were also collected on two occasions from the rams (only 15) as two-tooths and examined for general motility, sperm concentration and percentage of live sperm. There were no differences in semen characteristics between rams of the mated and control groups. The two-tooth rams were also subjected individually and randomly on three occasions to pen-libido tests, each with two oestrous ewes. Mating ability was assessed by recording the number of mounts attempted on the oestrous ewes, the number of services, the reaction time to mount (in seconds) and the reaction time to service. There were no differences between the mating and control groups in the number of mounts and number of services performed on each occasion of the libido test. Significant differences were found between both groups in reaction time to mount and in reaction time to service but only at the first libido test. It was concluded that the Booroola Merino x Romney ram lambs had achieved satisfactory levels of flock mating performance under the conditions of the trial. No adverse effects of mating on the post-mating body development of the ram lamb could be detected. Semen quality from the ram lambs deteriorated during mating but recovered shortly after mating. The use of ram lambs as sires had no adverse effects on their semen characteristics and libido performance at the two-tooth age. FOOT "CONDITIONS" The incidence of abnormal foot shape, foot scald and footrot was observed in Perendale and Booroola Merino crossbreds. The animals were generated in 1980 and 1981. Observations on foot "conditions" were made at the lamb, hogget and two-tooth ages for animals born in 1980, and at the lamb and hogget ages for those born in 1981. A scoring system was used to rank the various foot "conditions" (shape; scald; footrot) which were assessed separately. Booroola Merino crossbreds showed significantly a higher incidence of abnormal foot shape, foot scald and footrot than did Perendale sheep. Significant differences in foot "conditions" were also found between (Booroola x Romney) x Perendale and Booroola x Romney sheep. Sires of the progeny generated in 1980 and 1981 provided a major source for the variation in the incidence of these foot "conditions". Estimates of heritability of each of the observed foot "conditions" were calculated at different ages (lamb, hogget and two-tooth). Sex of the lamb caused significant effects on the incidence of abnormal foot shape and foot scald between ram lambs and ewe lambs, but not on the incidence of footrot. Differences in the incidence of abnormal foot shape and foot scald occurred between 1980- and 1981-born sheep. These differences were attributed partly to the particular climatic conditions in each year (notably the annual rainfall). It was concluded that under environmental conditions similar to that of the present trial, long-term selection programmes could be applied to enhance the natural resistance of sheep against foot diseases.
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    A study of the inheritance of some productive traits in Perendale sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
    (Massey University, 1975) Elliott, Kenneth Hamilton
    Genetic parameters were estimated using 3,313 half-sib records from 62 sires and .1720 daughter-dam pairs. The data used were obtained over the period 1957 to 1972. The estimates of heritability by paternal half-sib and daughter-dam regression analysis were respectively:- weaning weight (0.20 and 0.16); hogget body weight (0.27 and 0.44); fleece weight (0.32 and 0.30); quality number (0.26 and O.31); fibre diameter (0.54 and 0.47); staple length (0.49 and 0.35); character (0.23 and 0.23). An estimate of 0.03 was obtained for lambs weaned/ewe lambing (Lw/EL) by the daughter-dam regression analysis from 665 daughter-dam pairs. Estimates of genetic correlations were in the following ranges;- Medium negative (-0.4 to -0.6) Low negative (-02. to -0.4) Low positive (0.2 to 0.4) Medium positive (0.4 to 0.6) High positive (0.6 and over) Hogget body weight with character. Quality number with staple length. Weaning weight with quality number, fibre diameter and character. Quality number with fleece weight and fibre diameter. Hogget body weight with weaning weight and quality number. Staple length with character. Fleece weight with fibre diameter and character. Fleece weight with staple length. Phenotypic and environmental correlations were also estimated. Phenotypic correlations generally agreed with the genetic correlations. Important exceptions were hogget body weight with fleece weight, staple length and fibre diameter. Among the environmental factors studied, age of dam and rearing rank effects for the wool traits were generally small. These effects had a marked influence on weaning weight and hogget body weight. At weaning, singles were 4.2 kg heavier than twins, while at 14 months, this difference had been reduced to 2.1 kg. When comparing a two-year-old and mature age of dam effects, a 1.44 kg difference at weaning in favour of the mature age of dam reared animals, was reduced to a 1.11 kg difference at 14 months. The estimated parameters and environmental effects were discussed with reference to their implications in selection programmes. Relationships between hogget traits and the ewes lifetime production (four consecutive years) were analysed. Records from 458 sheep were used. Correlation coefficients indicated that hogget fleece weight, quality number, fibre diameter and staple length were good indicators of lifetime ewe performance for these traits. The results indicated that a poor relation exists between hogget body weight and number of lambs weaned by the ewe over four lambings. A regression analysis of hogget traits on life-time economic value of the ewe indicated that fleece weight and hogget body weight were the most important variables influencing life-time economic value. Implications of the results were discussed with reference to selection and culling programmes at the hogget age in ram breeding and non-ram breeding flocks.
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    A study of genetic and environmental variation and covariation in productive traits of a flock of Perendale sheep : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1978) Lewer, Roger Paul
    Performance records on 1724 two-year, 1160 three-year, 726 four-year and 449 five-year Perendale sheep from the Massey University flock were analysed. These records were collected between birth-years 1961 and 1974 inclusive, and therefore different numbers of years were involved at each age. The data comprised 97, 82, 65 and 56 sire groups for the respective ages. There were 403 ewes in 56 sire groups which had four consecutive records between two- and five-years of age. There were 922 two-year, 584 three-year, 296 four-year and 125 five-year dam-daughter pairs, but the last age group of records was considered too few to justify analysis. The dependent variables examined were quality number (QN), wool character (WC), staple length (SL), greasy fleece weight (GFW), fibre diameter (FD), and number of lambs weaned per ewe joined and present at lambing (NLW). Fibre diameter had been recorded in fewer years than the other traits and there were consequently less [i.e. fewer] observations available. The effects of the environmental factors of year, age of the dam of the ewe, rearing rank, NLW (wool traits only), and all interactions among them were assessed by computing the percentage of the total variance contributed by each factor for each variable. Quadratic components for these fixed effects were temporarily considered to be variance components for this purpose. Year effects were the most important source of enviromental variation in wool characteristics, but were less important for NLW. None of the other main effects were consistently important (i.e. contributed greater than two percent of the total variation) in explaining the observed variability. Year x NLW was the only interaction which contributed more than two percent of the total variance in any wool trait. The affected characteristics were two- and three-year QN, three-year FD and five-year SL. NLW (five-year-old ewes only) was affected by dam age x rearing rank and year x rearing rank interaction. Heritability estimates calculated by paternal half-sib method (daughter-dam regression estimates in brackets) were in the range of 0.22 - 0.28 (0.39 - 0.66), 0.16 - 0.39 (0.12 - 0.25), 0.32 - 0.71 (0.25 - 0.36), 0.24 - 0.53 (0.43 - 0.62), 0.38 - 0.68 (0.45 - 0.50) and 0.02 - 0.24 (-0.02 - 0.03) for QN, WC, SL, GFW, FD and NLW respectively. Differences between ages were seldom significant and the relevance of such a comparison was discussed. Paternal half-sib heritability estimates for the average of four mature (two- to five-years) production records were 0.50, 0.61, 0.84, 0.44, 0.49 and -0.01 for the same respective characteristics. Binomial analysis methods resulted in heritability estimates for fertility (twinning in brackets) of 0.06 (0.12), 0.02 (0.15), -0.01 (0.13), and -0.15 (0.01 for two-, three-, four- and five-year-old ewes respectively. Repeatability was estimated by averaging the regression of later on earlier record for all pairs of ages for wool traits and mature ages for reproductive characteristics and resulted in values of 0.46 (QN), 0.18 (WC), 0.50 (SL), 0.62 (GFW), 0.71 (FD), and 0.09 (NLW). Similar methods gave computed values for the repeatability of the difference between zero and one lamb weaned of 0.01, and between one and two lambs weaned of 0.13. Genetic and phenotypic correlations between all variables were calculated separately at each age by paternal half-sib and daughter-dam methods. The correlations were positive for GFW - FD, GFW - SL, GFW - WC, QN - WC and FD - SL, negative for GFW - QN, QN - FD and QN - SL, and mixed for FD - WC and SL - WC although the last of these were mostly positive. The phenotypic correlations between wool traits and reproduction were negative for NLW - GFW and NLW - SL and approximately zero for the remainder. Genetic correlations were negative for NLW - GFW, NLW - FD and NLW - SL, positive for NLW - QN and mainly positive for NLW - WC. Many of the genetic correlations involving NLW had large standard errors. Application of the results was discussed in terms of the selection indices which were constructed.