Massey Documents by Type

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

Browse

Has files: YesSubject: search.filters.subject.Border Leicester sheep

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    A study of the reproductive performance of two year-old Romney and Border Leicester X Romney ewes after differential feeding and gonadotrophin treatment : 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, 1975) Eastwood, Kenneth Charles
    The reproductive performance of 207 first-cross Border-Leicester x Romney (Border-Romney) and Romney 2 year-old ewes was compared after they grazed in the autumn for 2 months at 2 levels of feeding and treatment with 0, 600 or 1200 i.u. Pregnant Mare's Serum Gonadotrophin (PMSG). To induce and synchronise oestrus at the start of the breeding season, intravaginal progestagen sponges were inserted for 14 days. PMSG was injected on day 12 or 13 after first heat and ewes were then run with entire Southdown rams. Each ewe was laparotomised within a week of PMSG injection to record the ovarian activity. Peripheral blood was collected from a sample of ewes at intervals throughout pregnancy and progesterone concentration determined. The number and weight of lambs at birth and at weaning were recorded. High-plane ewes gained 1.39 kg and low-plane ewes lost 1.51 kg over the 2-month period of differential feeding. Following sponge withdrawal and at the next cycle 80% and 90% of all ewes were in oestrus and of these 77% and 80% were mated over 2 and 3 consecutive days, respectively. PMSG did not affect the degree of synchronisation of oestrus but treatment with the drug, improved feeding and injection on day 12 rather than 13, each reduced the mean cycle length. Border-Romney ewes had higher natural ovulation rate, lambing performance and response to PMSG than Romney ewes. PMSG reduced (16%) the conception rate at first service, proportionately more ewes returned to service at prolonged intervals (>20 days), and this "carry-over" effect reduced the incidence of ewes that later became pregnant. There was marked variation in ovarian response to PMSG. However, litter size increased with up to 5 ovulations per ewe despite an increasing percentage of potential lambs lost. Uterine capacity in terms of both number and weight of lambs born was greatest in Border-Romney ewes but exceeded natural ovulation rate in both breeds. Potential reproductive performance is, therefore, limited by the number of eggs released and in practice management factors before and at mating and selection of ewes with a propensity for higher ovulation rates should be emphasised. Lambs born to Border-Romney ewes were heavier at birth and grew more rapidly to weaning. It is likely that part of this superiority of growth rate was related to a greater milk production by these crossbred ewes and this possibility should be investigated further. Diagnosis of ewes with either single- or multiple-bearing pregnancies on the basis of blood progesterone levels (measured either early or late in pregnancy) was found to be no more accurate than other methods (rectal-abdominal palpation, ultrasonics and radiography) currently available. Variation in lamb birthweight within birth rank appeared to limit the accuracy of diagnosis of single- or multiple-bearing ewes late in pregnancy. Liveweight of the ewe and weight of lamb born were antagonistic in their effects on blood progesterone concentration.
  • Thumbnail Image
    Item
    A study of some factors affecting reproduction in one- and two-year-old ewes : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1981) McMillan, William Henry
    Experiment I: Reproductive performance was investigated in 176 one-year-old Romney and Border Leicester x Romney (F1) ewes following joinings with entire or vasectomized rams in 1977. Two-year-old performance of these ewes was investigated in 1978. First service conception rate was 74.6% in 1977 and the regression on liveweight gain over joining was negative (P < 0.01). Overall, 81.4% of marked ewe lambs conceived with 80.3% of the lambs born surviving to weaning. Delaying weaning from 8 to 11 weeks of age resulted in small improvements in lamb growth but penalized ewe growth. Suckled ewe lambs were lighter at the two-year-old mating but weaned more lambs per ewe joined due to a large improvement in lamb survival. Fleece production was temporarily reduced. Commercial applications of early joining are discussed. Experiment II: One hundred and nine 7 - 8 month old Romney ewe lambs and 108 adult Romney ewes were included in an ova transfer study to investigate age of ewe effects on ovum viability. Each of 48 owe lambs received two 8 - 16 cell ova, one from a ewe lamb (homologous transfers) and one from an adult ewe. The source of ova were identifiable by birth coat colour markings of the lambs born. Ovum recovery and fertilization rates were high and similar in both ages of ewe. However, only 25% of ewe lamb ova were represented by lambs at term compared to 52.1% of adult ewe ova (P < 0.01). Possible causes of this difference are discussed.