Massey Documents by Type

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

Browse

Search Results

Now showing 1 - 10 of 22

Investigation of palpable udder defects in non-dairy ewes : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science, Massey University, Palmerston North, New Zealand
(Massey University, 2023) Zeleke, Mandefrot Meaza
Udder defects have been associated with low survival rates and reduced live weight gains in pre-weaned lambs and increased pre-mature culling of ewes. However, there are gaps in our understanding of the pathology of udder defects and changes that may occur over time. To address these issues three studies were undertaken. Chapter 4 describes the effect of palpable udder defects (hard or lump) on milk production and composition, while Chapter 5 assesses changes in udder half defects over time. In chapter 6, aerobic bacterial species were identified, and in Chapter 7 the gross and histological lesions associated with palpable udder defects were described. Milk yield was reduced by more than 50% in defective udder halves; however, the whole udder milk yield depended on the persistence and type of the defect and contralateral udder half compensatory increase. Udder half defects changed over time in lactation and during the non-lactating period. Udder halves categorised as hard or lump at pre-mating were more likely (Relative risk ratio (RRR= 6.8-1440) to be defective at some time in the future, within the same year or in the following season, compared to the udder halves categorised as normal. Mannheimia haemolytica and Streptococcus uberis were identified as dominant bacteria from defective udder halves while S. aureus was isolated from both defective and normal udder halves in similar proportions. Among several bacterial species identified during lactation, Mannheimia haemolytica, Staphylococcus xylosus, and Streptococcus pluranimalium were more stable over time. Udder halves categorised as hard was described as moderately enlarged and contained a single large abscess on dissection while typical histology showed the presence of pyogranuloma with extensive chronic inflammation and granulation tissue. The pathological changes in udder halves categorised as lump varied from normal appearance to severe chronic inflammation with a purulent exudate. In conclusion, due to an increased risk of future recurrence and long-term damage to the mammary tissue associated with udder halves categorised as hard, ewes with such defects should be culled. In contrast, udder halves categorised as lump showed marked pathological variation; therefore, additional studies are needed to determine more accurately, by sub-categorising and/or use of methods other than udder palpation (e.g., ultrasonography). Keywords: Bacteria, Change Over Time, Gross pathology and Histology, Milk Composition, Milk Yield, Palpable Udder Defect, Somatic Cell Counts.
Effect of heavier live weight of ewe lambs at breeding on reproductive performance, mammary gland development and subsequent live weight : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science, Massey University, Palmerston North, New Zealand
(Massey University, 2021) Haslin, Emmanuelle
Breeding ewe lambs at seven to eight months of age can increase farm profitability and ewe lifetime performance. In New Zealand, 30 to 40% of ewe lambs are bred each year with a minimum recommended pre-breeding live weight of 40 kg. Ewe lamb reproductive performance increases with breeding live weight, therefore, some farmers aim to breed ewe lambs heavier than 40 kg. Increasing ewe-lamb growth rates prior to puberty, to achieve a heavier breeding live weight could, however, impair ewe lamb mammary gland development and lactational performance. Currently, little is known about the impact of breeding heavier ewe lambs on their subsequent performance, live weight, and efficiency. The aim of this thesis was to investigate the effect of breeding heavier ewe lambs on their reproductive performance, mammary gland development and live weight over their first three breeding seasons. Ewe lambs were managed from weaning to breeding and achieved an average live weight of 47.9 ± 0.38 or 44.9 ± 0.49 kg at breeding. A growth rate of 150 g/d prior to the first breeding did not affect ewe lamb mammary gland development to the weaning of their second litter, as measured using ultrasonography. Positive relationships were found between ewe lamb mammary ultrasound measures at one year of age and the growth of their progeny to weaning. The associations between ultrasound measurements and growth of the progeny indicate that ultrasound scanning has the potential to be used as a selection technique for heavier lamb live weight at weaning. Although the live weight difference between treatments was limited to three kilograms, compared with lighter ewes, heavier ewe lambs at their first breeding showed greater fertility rate, litter size and lambing percentage but did not differ in the second and third breeding seasons. Over the first three breeding seasons, heavier ewe lambs had greater lamb production than their lighter counterparts. Ewe lamb live weight treatment had no effect on progeny performance to weaning, nor ewe efficiency over the three-year period. A positive association was found between ewe lamb breeding live weight and their mature live weight at 39 months of age. Farmers should aim to breed their ewe lambs at heavier live weights to maximise their reproductive performance as a ewe lamb and, if well managed, they can achieve increased ewe performance over the first three breeding seasons, although there would be no impact on efficiency. Before firm recommendations can be made to farmers, lifetime performance and longevity of the heavier ewe lambs at breeding needs to be examined.
Genetic parameters of body condition score (BCS) and effects of BCS and BCS change on ewe performance : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science, Massey University, Palmerston North, New Zealand
(Massey University, 2020) Vialoux, Isabel
Body condition score (BCS) is an important management technique that can be easily learnt and implemented on farm to determine the body condition of ewes. The industry recommended BCS is 3.0 to 3.5 at mating to ensure optimal production. Currently the average industry BCS is less than 3.0 and recent research suggests that the change in BCS may be more important for determining the subsequent production of the ewe. The objectives of this thesis were to examine the relationships between BCS and production through exploring the effects of genetic and phenotypic BCS and BCS change on productive performance. Records of BCS were obtained from Focus Genetics and New Zealand Merino flocks to determine the effect of BCS change on phenotypic production and estimate the genetic parameters of BCS. There was no increase in production for ewes above a BCS of 3.5, therefore, BCS of 3.0 to 3.5 should remain the target BCS for phenotypic production. Ewes that decreased phenotypic BCS between lambing and weaning were associated with greater production indicating these ewes had utilised their stored body fat to achieve high milk yields. The estimated heritabilities of BCS change were low indicating limitations in the ability to alter the shape of BCS profiles by selection. Heritability, genetic and phenotypic parameter estimations of BCS and production traits were performed on 9,585 dual-purpose ewes and 2,007 Merino ewes. The heritability of BCS in New Zealand dual-purpose sheep was found to be moderately heritable (0.16-0.30) and had a high genetic correlation between BCS measurements across the production year. The best time to record BCS for genetic selection was confirmed to be mating. Live weight and BCS are highly genetically correlated, therefore, it may be relevant to explore the inclusion of BCS in the selection criterion to ensure that BCS does not exceed the optimal range of 3.0 to 3.5. The results of this thesis indicate that observing BCS is a valuable tool and it would be possible to change the genetic potential for BCS with genetic selection. This information can be used to develop selection criteria for BCS.
The effect of birth rank and age of dam on the reproductive performance of ewe replacements managed under New Zealand pastoral conditions : 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, 2020) Pettigrew, Emma
Selecting replacement ewes that are born to ewe lambs is an uncommon practice in New Zealand; however, there is the opportunity to increase ewe efficiency and increase the rate of genetic gain if the practice is adopted. Lambs born to ewe lambs may be lighter until up to four years of age, compared with lambs born to mature ewes, however there are few unbiased comparisons of performance. The objective of this study was to compare the reproductive performance of replacements born to either mature ewes or ewe lambs. A study with 115 singletons or twins born to mature ewes or ewe lambs, found that singletons born to mature ewes were heaviest, twins born to mature ewes and singletons born to ewe lambs were intermediate, and twins born to ewe lambs were lightest for their lifetime to eight years of age. There was no difference in lifetime lamb production among these four groups, and there was no difference in the efficiency among the ewe groups, however the power of that study may have been limited by relatively low numbers of animals. A second study utilised 1082 mature ewes and 1026 ewe lambs, bred to the same rams at the same time, producing 2701 lambs, of which, 358 lambs were selected as replacements. Lambs born to ewe lambs were lighter than lambs of the same birth rank born to mature ewes from birth until weaning and had lower rates of survival at tagging and from tagging to weaning. The relationship between the probability of survival to weaning and birth weight was quadratic, and differed for each birth-rank-by-age-of-dam cohort. Lambs born to ewe lambs, and as triplets to mature ewes have lower rates of lamb survival and growth to weaning, so farmers need to prioritise time and resources to improve these. In the third study investigating reproductive performance of replacements born to either ewe lambs or mature ewes, 135 twins born to mature ewes, 135 singletons born to ewe lambs, and 88 twins born to ewe lambs were bred (if heavier than 39 kg at breeding) as ewe lambs. Of the ewe lambs that were heavy enough to be bred, there was no difference in the number or weight of lambs produced at weaning from the three groups, but twins born to ewe lambs were less likely to reach breeding weight targets. During their second breeding (at approximately 18 months), all ewes were bred, and there were no differences in the number or weight of lambs produced at weaning. This indicates that the offspring of ewe lambs could be selected as replacements, but that farmers need to consider selecting based on weight at weaning if they intend to breed the ewe lambs at eight months of age. Further work, including an economic analysis, and continued investigation into the lifetime production and efficiency of ewes born to ewe lambs is needed. Genomic technologies are currently being used by scientists to increase the accuracy of selection of replacement animals for traits that are difficult to measure in the adolescent at the time of selection. Reproductive performance as a ewe lamb has an impact on the lifetime production of a ewe, and live weight at the time of breeding can heavily influence the likelihood of the ewe lamb becoming pregnant during her first breeding. Using ewe lambs from the second and third studies, and additional ewe lambs, five gene regions were found to be associated with live weight at eight months of age in ewe lambs, and two gene regions were found to be associated with the occurrence of pregnancy during their first breeding at eight months of age. Further investigation into these, and other, gene regions associated with reproductive traits in ewe lambs could allow the use of marker assisted selection to identify genetically superior animals. In conclusion, farmers should prioritise their time and resources to improve lamb survival and lamb growth for lambs born as triplets to mature ewes, or as any birth rank to ewe lambs. Lambs born to ewe lambs could be selected as replacement ewes, if they are heavy enough to be bred themselves at eight months of age. Lambs born to ewe lambs may be lighter than lambs born to mature ewes for their entire lifetimes, but have similar reproductive performance. There is genomic control of traits such as live weight and pregnancy occurrence in ewe lambs that needs further investigation, before genomics can be considered a practical tool for farmers when selecting their replacement ewes.
A search for biomarkers of ovine pre-partum vaginal prolapse : a thesis presented to Massey University in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Biochemistry, Massey University, New Zealand
(Massey University, 2019) Brown, Stuart
Ovine pre-partum vaginal prolapse (known as bearings in sheep) occurs within a few weeks prior to lambing and unless treated both ewes and unborn lambs will die. Rates of prolapse in New Zealand vary from 0.1 to 5% per annum, varying between season and farms and is a worldwide problem. Much research has been undertaken over many years to determine the cause of this condition but no clear etiology has emerged. In this study plasma samples were collected prior to prolapse occurring in order to determine physiological changes leading to prolapse. 650 ewes were ear tagged and blood sampled on one day prior to lambing, 28 of these ewes subsequently prolapsed. The date of occurrence and tag number of prolapsing ewes was recorded to enable a comparison of the plasma profile of prolapsing ewes and non-prolapsing ewes. An improved method for running sheep plasma on 2D gels was developed resulting in improved protein spot resolution along with a lower coefficient of variation for spot volume. Using this improved method samples were subjected to 2D DIGE (two dimensional differential in gel electrophoresis) to determine if there were differences between the two groups of ewes. One of the differences was in haptoglobin, a major acute phase protein in ruminants, in which some isoforms were upregulated approximately 3 fold prior to prolapse occurring. This may indicate an inflammatory response due to either infection or injury. A good correlation was found between total haptoglobin spot volume data and quantitative haptoglobin assay data from the same samples (r² = 0.91) validating the haptoglobin gel spot data. Another finding was that alpha-1B-glycoprotein was down regulated close to prolapse, however the biological significance of this is unknown. It was also found that there was a negative correlation between cortisol and days to prolapse from sampling (r² = 0.36) i.e. ewes closest to prolapse had higher plasma cortisol concentrations than controls. These findings in conjunction with a literature search, field observations and an argument from logic lead the author to propose that chronic stress or anxiety may raise intra-abdominal pressure and contribute to the development of prolapse.
Effect of immunization against androstenedione on the reproductive performance of ewe lambs : assessment of dosing regimes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science, School of Agriclture and Environment, Palmerston North, New Zealand
(Massey University, 2019) Lipholo, Mapali Agnes
In New Zealand, there are a number of impediments to the adoption of ewe lamb breeding, for example, their poor reproductive performance compared to mature ewes. This low reproductive performance is primarily due to a lower ovulation rate. A series of studies such as improving nutrition pre-breeding and live weight at breeding have been conducted in New Zealand to improve the reproductive performance of ewe lambs, but they have not resulted in significant increases in the ewe lamb ovulation rate. In mature ewes, immunization against androstenedione can increase ovulation rate. Immunized mature ewes release three or more ova in each estrous cycle. To date, little data has been generated for the response to immunization against androstenedione of ewe lambs. One of the most commonly used androstenedione vaccines in New Zealand is Androvax®. A study conducted in Ireland using Fecundin® reported that control ewe lambs showed estrous behaviors at an earlier date than immunized ewes. This thesis, therefore, examines the effect of immunization against androstenedione using Androvax® on the reproductive performance of ewe lambs at two different dosing regimens. The present study was conducted between February 2017 and January 2018 using 300 Romney ewe lambs. Ewe lambs were immunized with Androvax® using two dosing regimens, 1) ten and six (A10 – 6) weeks and, eight and four (A8 – 4) weeks prior to the introduction of the entire ram. Teaser rams fitted with mating harnesses were introduced to the ewe lamb flock at a ratio of 1:100 and remained with the flock until the start of breeding. During this time, ewe lambs were checked for teaser harness crayon marks as an indicator of the onset of behavioral oestrus. After the removal of the teaser rams, entire rams fitted with mating harnesses were introduced at the ratio of 1: 50 and remained with the flock for two oestrous cycles (34 days). Ewe lambs were also checked for ram harness crayon marks after every 17 days from the introduction of the entire ram to identify the cycle in which they were bred. Pregnancy diagnosis was carried out 90 days after the start of the breeding period. Ewe lambs bearing triplet fetuses were removed from the study. Lambing began in October and ended in November. Lambs were weaned in January at the average of 102 days of age. The majority of ewe lambs in A10 – 6 and those in a control treatment were marked by the teaser ram prior to the introduction of the entire ram compared with those in A8 – 4 treatment (62 % vs 56 vs 44% respectively, p<0.05). Ewe lambs that show signs of behavioral oestrus prior to the introduction of the entire ram have higher ovulation rates leading to a high fecundity rate, however, in this study, ewe lambs in A8 - 4 treatment had greater (p<0.05) fecundity rates even though they showed later onset of behavioral oestrus. Ewe lambs in A8 – 4 treatment had higher (p<0.05) fecundity rates at pregnancy diagnosis than the control treatment while those in A10 – 6 treatment did not differ from either group (1.66 vs 1.30 vs 1.49 respectively; p>0.05). Ewe lambs in A8 – 4 treatment had a greater (p<0.05) percentage of twin and triplet fetuses and fewer singles compared with the control and A10 – 6 treatment. At lambing, the number of lambs born did not differ between the three treatments, however, treated groups (A10 – 6 and A8 – 4), had more twins than the control treatment. Generally, immunization against androstenedione increased the fecundity rates but not the itter size and number of lambs weaned and the recommended dosing regimen is eight and four weeks before breeding (A8 – 4). It is, therefore, important for farmers to work on minimizing pregnancy losses and lamb mortality when they used androvax in ewe lambs in order to increase both litter size and number of lambs weaned.
An epidemiologic investigation of wastage and productivity of ewes in a sample of New Zealand commercial flocks : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Palmerston North, New Zealand
(Massey University, 2020) Griffiths, Kate Jade
Until recently, little was known about ewe wastage in commercial New Zealand ewe flocks, or indeed, internationally. This PhD was undertaken with the broad objective of establishing the extent, timing and cause (premature culling or mortality) of ewe wastage in New Zealand ewe flocks, while also identifying factors associated with increased ewe wastage including pre-mating body condition score (BCS), failure to rear a lamb and, linked with the latter, impact of ewe udder defects on productivity. To the authors’ knowledge, this is the first study that reports both lifetime wastage and detailed annual wastage in a sample of New Zealand commercial flocks. Of the 13,142 enrolled ewes, 50.4% exited their respective flocks due to premature culling (where a ewe is culled from the flock prior to the potential end of her productive lifespan) and 40.0% due to on-farm dead/missing, giving a total of 90.4% that exited due to wastage. In all years, pre-mating BCS could be used as a predictor of ewe wastage with odds of wastage lower with increasing BCS. In Year 1, wastage for each cohort ranged from 7.6% - 45.4% of ewe lambs enrolled, while wastage due to dead/missing accounted for 26.8% - 100.0% of ewe lamb wastage across cohorts, and premature culling was primarily due to poor reproductive performance (dry at pregnancy diagnosis or dry at docking when 3-6-week-old lambs are yarded for ear marking, tail removal and castration of males). Hence, other than the cull sale-value for those that were prematurely culled, the farmer received no productive or economic benefit from these wasted ewe lambs. Ewe lambs with heavier conceptus adjusted liveweight (CALW) and those that gained greater CALW between pregnancy diagnosis and pre-lambing were less likely to be dry at docking. Similarly, for two-tooth ewes (18-months of age at breeding), heavier ewes and those that gained CALW were less likely to be dry at docking than lighter ewes or those that lost CALW. Pre-mating udder palpation scores of hard or lump were associated with increased odds of lambs not surviving to weaning compared with normal scores. Additionally, surviving offspring of ewes with pre-mating udder palpation scores of hard had lower growth to weaning. Commercial farmers can use the information presented in this thesis to identify ewes within their flocks that have increased risk of wastage or poor productivity. They can then alter management of these at-risk ewes to both improve ewe productivity and reduce likelihood of wastage.
An investigation into the effects of different housing and feeding systems on behaviour and milk production of dairy ewes in mid and late stages of lactation : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Manawatu, New Zealand
(Massey University, 2018) Bliss, April Elizabeth
Comparisons of different New Zealand dairy sheep farm systems are currently lacking. The aim of this study was to evaluate the effects of different management systems on the behaviour and milk production of East Friesian cross-bred sheep at different stages of lactation. Two study groups were evaluated. In study group 1, a mob of 479 mixed-age, mid-lactation ewes were housed 24 h/day, and a separate mob of 473 mixed-age, mid-lactation ewes were managed in a hybrid system (housed between morning and afternoon milkings; grazed lucerne overnight). Both received a total mixed ration (TMR) indoors. In study group 2, a mob of 604 mixed-age, late-lactation ewes grazed pasture 24 h/day, and a separate mob of 452 mixed-age late-lactation ewes were in a hybrid system, grazing pasture overnight. For both study groups, individual milk yield, walking distance, lying time, ambient temperature, live weight, and body condition score (BCS) were recorded.--Shortened abstract
A study of the effects of post-mating progesterone supplementation on the reproductive performance in the ewe : 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, 1989) Walsh, Peter Allan
The aim of this study was to investigate the effects of post-mating progesterone supplementation, in the form of CIDRs, on the reproductive performance in recently mated ewes. The effect of two nutrition treatments were also examined by feeding two different pasture allwances to these ewes during a two week period immediately folliwing a synchronized mating. Two hundred and thirty four Border Leicester X Romney first cross ewes, compresed of 130 mixed-age ewes (3-8 years) and 104 two-tooth (maiden) ewes were flushed on increasing pasture allowance prior to joining. These ewes were naturally mated at a synchronized oestrus following a 13 day CIDR treatment period. During the three days following CIDR withdrawal, 88.0% of the ewes were mated. The mixed-age ewes came into oestrus significantly earlier that the two-tooth ewes (P < 0.001). There was a significant linear relationship between liveweight and onset of oestrus (P < 0.05), with the heavier two-tooth ewes coming on oestrus earlier than the lighter two-tooth ewes. This was not apparent in the mixed-age ewes. On Day 2 following mating, ewes were randoaly divided into either the high or low pasture allowance levels. Pasture allowance levels were monitored using an Ellinbank Pasture Meter (EPM). Levels of feed intake were estimated for a random sample of 20 ewes both before and after mating through the use of intraruminal chromium releasing devices (CRDs). Sward heights (representing quantity), botanical composition and in vitro digestibilities (representing quality) were recorded for both the flushing and the post-mating period. This information led to the estimation of voluntary herbage intakes during the flushing period (Period I) of 1.2 M, while the intake levels of the ewes following the mating (Period II) were calculated to be approximately 1.6 M and 1.0 M for the high and low pasture allowance levels, respectively.
Cervical mucus arborization : a preliminary study of its use in assessing ovarian hormone levels in the ewe : a thesis presented at Massey Agricultural College in part fulfilment of the requirements for the degree of Master of Agricultural Science in the University of New Zealand
(Massey Agricultural College, 1957) McDonald, Maurice Frank
Many of the gross physiologicial processes affecting reproduction in animals have been elucidated. The availability of the ovarian hormones in relatively pure form has further allowed the confirmation of their role. It is apparent that there is general agreement and confidence in the findings of much of this work, as is shown by the increasing application of steroids to animal production. However, in the main the investigations so far reported have been of a qualitative nature only. It is thus apparent that for a thorough understanding of the basic mechanisms controlling reproduction it will be necessary also to study in detail the quantitative changes in hormone levels and their associated effects [From Introduction]

Massey Documents by Type

Browse

Filters

Settings

Sort By

Results per page

Search Results