Massey Documents by Type

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

Browse

Has files: YesSubject: search.filters.subject.Lamb growth

Search Results

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    The effect of shearing ewes at mid-gestation on reproduction and performance : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Zoology at Massey University
    (Massey University, 2000) Hanna, Julie Elizabeth
    This study tested the hypothesis that shearing ewes in mid-gestation causes an increase in lamb birth weight. Growth rates of lambs were calculated to test for any additional trade-off between investment at gestation limiting investment at lactation. Liveweights and growth rates of lambs were analysed for a difference between the sexes with the expectation that sheep may put extra investment into male lambs, compared to female lambs. Experiments were conducted with mixed-sex twin pairs to determine if the male lamb was able to receive more milk than the female lamb. Sixty ewes were selected after synchronised mating and pregnancy diagnosis: 30 were twin-bearing and 30 were single-bearing. Half of each group (twin- and single-bearing) were shorn at mid-gestation (approximately 77 days before lambing) and observations of their behaviour and estimations of their food intake were made. Shorn ewes adjusted rapidly to shearing, exhibiting no apparent difference in behaviour one week after shearing. Shearing led to an increase in ewe weight and lamb birth weight. Rearing twins was costly for the twin-bearing ewes: they were lighter, had lower condition scores and less wool growth than ewes with singletons during late-gestation and lactation. Twin lambs were born lighter and grew slower than single lambs. There was no evidence of sex-biased investment in this study. A slight trade-off between gestation and lactation was apparent for shorn, single-bearing ewes. There was no difference between twin lambs born to shorn or full fleece dams. Shearing ewes at mid-gestation appears to be a useful tool for increasing the birth weight of lambs which could lead to an increase in survival of newborn lambs.
  • Thumbnail Image
    Item
    Effect of herb-clover mixes on weaned lamb growth : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palerston North, New Zealand
    (Massey University, 2014) Somasiri, Sharini Carol
    The quality and production of ryegrass (Lolium perenne L.) /white clover (Trifolium repens) pastures are seasonal in New Zealand. Earlier research showed that a sward mix of plantain (Plantago lanceolata), chicory (Cichorium intybus L.), white- and red-clover (Trifolium pratense) resulted in greater lamb live weight gains in the late summer early autumn period. However, this has not been tested across all the seasons in New Zealand. Therefore, research was undertaken for two consecutive years (2011/2012 and 2012/2013) on three sward mixes; Pasture mix, Plantain mix and Chicory mix in early spring, late spring and early summer (late spring), summer and autumn. The Pasture mix consisted of perennial ryegrass and white clover. The Plantain mix consisted of plantain, white- and red-clover. The Chicory mix consisted of plantain, chicory, white- and red-clover. It was hypothesised that lamb performance (live weight, live weight gain (LWG) and carcass weight) and apparent carcass weight production per ha would be greatest in the Plantain and Chicory mixes in all four periods. Secondly it was hypothesised that Plantain and Chicory mixes would have lower feed conversion ratios (FCR) with higher herbage utilization efficiencies (EHU%) than the Pasture mix. In each period weaned lambs were reared in the three herbage treatments for a maximum of two months. Lambs were weighed fortnightly and they were slaughtered within 12 hours of being off the pasture at the end of the experiment. Carcass weights were obtained from the abattoir. The Plantain and Chicory mixes had a higher feeding value than the Pasture mix during early spring to autumn. Both Plantain and Chicory mixes produced heavier (P<0.05) lambs, higher (P<0.05) live weight gains (LWG) and carcass weights compared to the Pasture mix in all periods. Total apparent carcass weight production per ha were 407, 748 and 709 kg/ha in year one and 474, 607 and 642 kg/ha in year two in the Pasture mix, Plantain mix and Chicory mix, respectively. Both Plantain and Chicory mixes had lower (P<0.05) feed conversion ratios (FCR) and higher (P<0.05) herbage utilization efficiencies (EHU%) compared to the Pasture mix. This research has shown that sheep farmers in New Zealand can finish lambs at a faster rate for heavier carcasses using herb-clover mixes from spring to autumn than on ryegrass/white clover pastures.
  • Thumbnail Image
    Item
    Estimation and identifiability for a dynamic model of maternal nutrition and fetal growth in sheep : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Statistics at Massey University, Albany, New Zealand
    (Massey University, 2012) Wang, Leiyan
    The optimal maternal nutrition intake is extremely important in the second half of pregnancy for fetal development in mammals. It affects the health and wellbeing of the offspring. The purpose of this study was to determine the optimal daily nutrition intake for sheep during the second half of their pregnancy, to achieve a pre-determined desirable birth weight for lambs. By achieving the optimal birth weight, the postnatal development of the animals is likely to be improved. In this study, pregnant sheep carrying singletons or twins were considered. There were two levels of nutrition, low and high. Various dynamic mathematical models were proposed to obtain the optimal daily nutrition intake. The model parameters were estimated by weighted least-squares. Bootstrap simulations were used to check the reliability of each estimated parameter. Finally, the optimal daily nutrition intake was obtained by solving the boundary value problems, with pre-determined parameter values. The results suggested that the optimal daily nutrition intake for sheep in the second half of their pregnancy was a constant. For the particular breed of sheep, with target weight 6.5 kg for singletons, the optimal nutrition intake was 1.36 kg of dry matter per day. For twins, with a target weight of 12 kg, the optimal nutrition intake was 1.93 kg of dry matter per day. In addition, a comprehensive and generic ‘black-box’ algorithm was produced using the software MATLAB. It could return the optimal daily nutrition intake for any type of mammals given a time series of fetal weight and maternal nutrition.
  • Thumbnail Image
    Item
    Measurement, mathematics, and mechanisms of mammalian growth : a thesis presented in partial fulment of the requirements for the degree of Doctor of Philosophy at Massey University
    (Massey University, 1978) Clark, Ross Graham
    Longitudinal growth experiments using rats, lambs, and heifers were analysed by establishing linear relationships between ages, live weights and body lengths in individual animals. Various analytical methods were investigated. Statistical and biological reasons forced the logarithmic transformation of weights and lengths, a three parameter logarithmic metameter was used if means and standard deviations were correlated on a two parameter logarithmic metameter. Age was transformed to give linear relationships. Changes to the experimental design and analysis of growth experiments were suggested. Effects were demonstrated in individual animals that were previously only shown for grouped data and the techniques' sensitivity produced novel findings. Rats were ovariectomised at three ages and/or treated with oestrogen and slaughtered at four ages. The rat ovary inhibited growth pre-pubertally, and the response to ovariectomy or oestrogen was negatively related to the pre-treatment growth rate. Compensatory growth occurred following weaning in rats and following birth in ruminants. Estimated initial weights explained more of the variation in subsequent growth rates than did observed weights. In rats pre-weaning growth lines diverged (compensation being negligible), birth and weaning weights being positively correlated, post-weaning growth rate was strongly negatively correlated with weaning weight. Estimated birth and final weights, and weaning and final weights, were unrelated; compensation being nearly complete. Two sets of pre-weaning lamb live weights (collected by others) were, for individual animals, linearised. Pre-weaning compensation occurred, as it did in two independent sets of weighings from monozygotic twin heifers (also collected by others). Compensatory growth, between and within sets of twin, occurred rapidly to weaning, then slowed. The efficiency of identical twins for experimentation, using these methods, was shown, as were the disadvantages of using average daily gains. The linear relationships did not explain all the systematic variation, short- and long-term oscillations in growth rate occurred. Long-term oscillations were related to live weight rather than to age. Neo-natal testosterone treatment of female rats transposed and advanced the pattern of growth. Both Sex and Strain affected the pattern of growth. The possible use of these techniques in animal breeding was discussed. The logarithms of lengths and weights, assumed by many biologists to be linearly related (allometry), showed curvilinear relationships. A technique of carcass analysis was developed and applied. Ovariectomy increased rat body weight and length but did not produce obesity (assayed by percentage composition and by allometry). Oestrogen stimulated fat deposition but inhibited linear growth. Body weight's response to oestrogen was adaptive,bone growth's non-adaptive. Similarly there was a large pre-pubertal sex difference in body length but a small difference in body weight. This separation of the mechanisms controlling bone growth and body weight increase was discussed. Part of the increased size of ovariectomised rats was attributed to increased skin size (and altered composition) and decreased tail length, giving decreased heat loss, and improved energy utilisation for growth. Body growth occurs in two overlapping phases, of cell hypertrophy and cell hyperplasia, represented by different growth equations, and controlled by different mechanisms. A possible mechanism controlling cell hypertrophy, and directing compensatory growth, based on cartilage growth, would explain some of the effects described. The endocrinology of the mechanism, and oestrogen's interaction with it, were discussed.
  • Thumbnail Image
    Item
    Ovine placental lactogen and insulin-like growth factor-I : a study of their biological actions and potential to enhance animal production : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
    (Massey University, 1996) Min, Seok-Hong; Min, Seok-Hong
    Ovine placental lactogen (oPL) has been considered to be important in the regulation of fetal lamb growth. Recent sequence studies have also shown that oPL has considerable structural similarity to ovine prolactin (oPRL) and ovine growth hormone (oGH), raising the possibility that oPL may have potential as a stimulator of milk yield and postnatal growth. Evidence from laboratory animals indicates that the biological actions of GH and perhaps PL are mediated largely by IGF-I, acting in both a paracrine/autocrine and an endocrine manner. However, the potential of IGF-I therapy has not been fully explored in domestic animals. Therefore, the overall aim of this study was to examine the biological actions of recombinant oPL and IGF-I and to evaluate their potential use to stimulate performance of farm animals. In the first three experiments, the biological actions of recombinant oPL were examined in pregnant and lactating ewes, and in young growing lambs, and compared with those of bovine growth hormone (bGH). bGH treatment for 7 days from day 101 of pregnancy increased total uterus weights, but administration of an identical dose of oPL had no effect. Similarly, exogenous bGH over 5 days increased milk yields in lactating ewes, whereas such an effect was not apparent with oPL treatment. However, the reverse situation occurred in young growing lambs in which oPL, not bGH, treatment for 21 days from day 3 of life stimulated growth rate and voluntary feed intake. Different biological actions of bGH and oPL in pregnant and lactating ewes were associated with a situation in which bGH, but not oPL, treatment increased circulating concentrations of IGF-I. Conversely, in young growing lambs, the growth-promoting effect of oPL appeared to be mediated primarily via a change in voluntary feed intake since both oPL and bGH treatment had only small effects on plasma IGF-I concentrations. The inability of bGH to stimulate plasma IGF-I concentrations in young lambs, accompanied by the lack of a growth-promoting effect of bGH, suggested that hepatic GH receptors (GHR) may not be fully functional at this stage. This hypothesis was examined in an experiment in which the ontogeny of hepatic GHR was assessed by measuring IGF-I responsiveness to a GH stimulus, as well as hepatic GH binding, in lambs of different ages (days 6/7, 20/21, 34/35, and 62/63 of life, and yearlings). Results showed that the plasma IGF-I response to exogenous bGH in young lambs was much lower than that in yearling sheep. Consistent with this, measurement of hepatic GHR at day 7 and 63 of life, and in yearling sheep, showed that bGH treatment failed to alter GHR number in young lambs, while up-regulating it in yearling sheep. In contrast, non-stimulated GHR numbers were similar across ages. These data suggest that hepatic GHR in young lambs are not fully functional, which may explain the lack of a growth-promoting effect of bGH in newborn animals. The importance of the GH-IGF-I axis in the regulation of post-natal growth was further demonstrated in an experiment, in which anabolic effects of recombinant IGF-I over a prolonged period (8 or 12 weeks) were measured in energy-restricted sheep. IGF-I treatment elevated circulating concentrations of IGF-I, but depressed plasma GH concentrations. The reduction in circulating GH levels was accompanied by a down-regulation of hepatic GHR. As a result, recombinant IGF-I had little growth-promoting effect although it improved other parameters such as nitrogen digestibility and components of the immune system. In conclusion, the present study suggests that recombinant oPL, like GH, has potential in improving farm animal production. However, the biological actions of oPL seem to be mediated in a different manner from those of GH. This could have practical implications in situations where GH has no biological actions. For example, in very young lambs in which hepatic GHR are not fully functional, oPL could provide an alternative means to stimulate growth. This could be also true for IGF-I because, in young animals, the negative-feedback regulation of both plasma GH and hepatic GHR concentrations by IGF-I treatment may be less likely to limit a growth response than is the case in older animals.
  • Thumbnail Image
    Item
    The development and growth of skeletal muscle in fetal and neonatal 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, 1998) McCoard, Susan Anne; McCoard, Susan Anne
    The objective of these studies was to identify and investigate factors involved in the regulation/control of fetal growth and development in the sheep, with particular emphasis on cellular development of skeletal muscle. Two models with the potential to impose growth-restriction on the developing fetus without invasive manipulation of the fetal environment were used in this series of studies. First, ewes mated out-of-season generally give birth to offspring with lower body weight than comparable offspring born to ewes mated in their natural breeding season. Fetal growth restriction in this situation is associated with impaired placental development in the out-of-season ewes which is evident by 84 days of gestation. Despite impaired placental growth, ewes mated out-of-season did not, in this study, consistently give birth to low-birth-weight offspring. Although differential effects on myofibre morphology were observed between fetuses from each group, the lack of differences in muscle weights and inconsistent effects on body weight indicated that this comparison proved an unreliable model with which to study fetal muscle growth and development. The second model involved the comparison of twins versus singles. Twin lambs are consistently lighter than single lambs as a result of maternal constraint characterized by restricted placental size per fetus. Coupled with low birth weights, the growth-restricted twin lamb also had smaller hindlimb muscles compared to singles. Maternal constraint in this situation not only had a negative influence on body and muscle weight, but myofibre hypertrophy was also retarded as indicated by smaller myofibre cross-sectional area. The adductor muscle DNA content, and total nuclei number in selected hindlimb muscles, were lower in twins than in singles. Myofibre number did not differ between ranks. An immunohistochemical technique involving the muscle-specific regulatory factor MyoD allowed the identification of myogenic precursor cell nuclei, which are likely to be satellite cell nuclei in muscles from fetuses in late gestation or early postnatal lambs. Bromodeoxyuridine proved to be unsatisfactory as a marker of actively dividing cells because it did not cross the fetoplacental barrier in sheep. However, MyoD was a useful marker of active satellite cells. MyoD-positive nuclei were less abundant in hindlimb muscles of twins than in singles suggesting differential effects of growth restriction on cell cycle activity. The pattern of expression of this factor during development suggests that MyoD may also have an important role in late fetal and postnatal muscle growth. These results illustrate that growth restriction during late gestation can have important consequences for birth size and skeletal muscle hypertrophy. The observation that myofibre number is not affected suggests that the full complement of fibres has been reached prior to any major nutritional impact which results in growth restriction. The delayed myofibre hypertrophy observed in twin lambs as compared to singles, coupled with lower total DNA content and fewer myogenic precursor nuclei, suggest that the late fetal developmental period is important for muscle growth and the attainment of an adequate birth weight. This result also shows that this period of development has important implications for postnatal muscle growth and may be important in determining ultimate mature muscle mass and postnatal growth potential.