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    The effect of scrotal circumference on pregnancy rates in Mpwapwa breed cattle during September – November 2020 breeding season at Taliri Mpwapwa farm in Tanzania
    (Nexus Academic Publishers (NAP), 2021-09-15) Kabuni KT; Laven R
    The goal of this study was to assess the effect of scrotal circumference (SC) on conception rates in Mpwapwa breed cattle during the Sept – Nov 2020 breeding season. Eight Mpwapwa bulls aged ≥3 years were selected from 23 bulls which had passed a structural soundness and movement tests based on having the largest SC and used to mate 324 non-pregnant Mpwapwa cows. Mating was conducted in eight groups with each group randomly assigned a single bull. For each bull, data were collected on age, pre-breeding body condition score (BCS) and body weight, SC and total number of cows bred. Based on p<0.25 value in a univariable model with pregnancy rate as the outcome variable, all of the variables except bodyweight were included in a multivariable logistic regression model with pregnancy rate as the outcome variable. Of those variables only pre-breeding BCS was clearly associated with odds of pregnancy. Compared to a bull with a BCS of 3.5, a bull with a BCS of 3.0 had only 0.29 times the odds (95% confidence interval (CI) 0.15 to 0.57) of getting a cow pregnant during the breeding season. For SC, the data were compatible with a small decrease and a moderate increase in the odds of pregnancy (odds ratio for a 1 cm increase in SC was 1.05 (95%CI 0.84 to 1.3)). Further research on the association between SC and pregnancy rate in Mpwapwa bulls is needed, including identifying whether there is an interaction between BCS and SC and their effect on subsequent fertility.
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    Comparative study between fixed-time artificial insemination and natural mating on reproductive performance (conception and pregnancy rates) of Mpwapwa breed cows in Tanzania : a thesis presented in partial fulfillment of the requirement for the degree of Master of Science in Animal Science, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
    (Massey University, 2017) Kabuni, Kabuni Thomas
    The aim of this project was to assess whether using a PGF2α synchronization protocol in Mpwapwa cattle would improve reproductive performance. A standard 14-day PGF2α synchronization protocol with a single FTAI was compared to NM over a 12-weeks breeding season. At the end of the study, 39/100 cows were pregnant in the FTAI group and 49/100 cows were pregnant in the NM group. This difference was not statistically significant (P=0.21), although the odds ratio of pregnancy was lower in the FTAI group than the NM group (unadjusted RR=0.8; 95% - CI 0.58-1.09). However, cattle in the PGF2α-treated group were only inseminated once, whereas the NM group could be naturally mated on multiple occasions during the breeding season; In addition, the use of PGF2α allowed the use of AI, which is not feasible under most Tanzanian systems when cattle come into oestrus naturally. Thus, the results of this study suggest that PGF2α -based synchronization and FTAI, particularly if used alongside natural mating, can improve the reproductive performance of Mpwapwa breed cattle as well as allowing for greater genetic gain than occurs with naturally mated cattle. The proportion of cows that came into heat and displayed behavioural signs after administration of the first PGF2α injection was very low (only 10/100 cattle). The reason for this poor response is unclear. It could be that oestrus detection was not very effective, or that a higher than expected proportion of cattle did not have a responsive CL. The most likely cause of the latter is a higher proportion of cattle in anoestrus. Further investigation of the reproductive state of Mpwapwa cattle at the start of the breeding season would identify how important anoestrus is as a cause of poor reproductive performance. If anoestrus is common, identifying cattle in anoestrus at the start of the season could be useful, as they could be treated using progesterone-based programmes and cattle with a CL could be treated with PGF2α. Key words: Mpwapwa breed cattle, PGF2α synchronization protocol, FTAI, NM, Reproductive performance.
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    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.
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    Reproductive performance and the transition period of thoroughbred mares in New Zealand : evidence and implications for future alternative management strategies : 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, 2012) Hanlon, David William
    The aims of this research were to investigate the reproductive performance of Thoroughbred mares in New Zealand, to examine the use of intravaginal progesterone to manage transitional mares and to develop a potential model for haemorrhagic anovulatory follicle (HAF) development in the mare. Firstly, a prospective cohort study was performed involving five stud farms in the Waikato region of New Zealand during three consecutive breeding seasons (2006-2008). A total of 1482 individual mares contributed 2007 mare years and 3402 oestrous cycles over the three breeding seasons. The mean first-cycle pregnancy rate was 53.6%, the end-of-season pregnancy rate was 85.3% and the foaling rate was 80.2%. The length of the breeding season was relatively short with 87% of services occurring in the 91 day period between 1st September and 30th November. Multivariable analyses revealed that reproductive performance was influenced by two main mare-related factors; the age of the mare and her reproductive status (dry or foaling). Increasing mare age significantly reduced the first-cycle pregnancy rate, reduced the end-of-season pregnancy rate and increased the interval from the start of the breeding season to conception. In terms of reproductive status, dry mares had a significantly higher first-cycle pregnancy rate and end-of-season pregnancy rate compared with foaling mares. The majority of variation in reproductive performance was associated with mare-level factors and the contribution of the stallion and stud farm was relatively minor. Transitional mares treated with intravaginal progesterone at the start of the breeding season were served two weeks earlier than untreated control mares. In the first 21 days of the season, 95% of treated mares were served compared with 43% of control mares. Treated mares also conceived earlier and had a higher end-of-season pregnancy rate than control mares. Follicle development in response to intravaginal progesterone treatment iii appeared to be mediated through a close temporal association between progesterone, FSH and LH during treatment. In the last study, transplantation of chorionic girdle into non-pregnant mares resulted in elevated eCG concentrations in all mares and the development of multiple HAFs in the treated mares over a prolonged time-span. In conclusion, this research has, i) identified the most important factors associated with the reproductive performance of New Zealand Thoroughbred mares, ii) determined that intravaginal progesterone treatment is a suitable management tool for transitional mares and iii) created a model for HAF development in the mare.
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    In vitro and in vivo studies on treatment and prevention of bovine mastitis : a thesis presented in partial fulfilment of the requirements for the degree of Philosophy Doctor in Veterinary Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2011) Petrovski, Kiro R.
    Mastitis prevalence on dairy farms depends on the number of infected cows and the duration of each intramammary infection. Strategies aiming to influence these factors are the subject of research presented in this thesis. Decreasing the duration of infection can be achieved by successfully treating infected quarters. Treatment of mastitis can occur during lactation or in the dry period. Treatment success is influenced by the concentration of antimicrobial achieved at the site of infection and the length of time it is present. The concentration of antimicrobial should exceed the relevant minimal inhibitory concentration. The susceptibility of mastitis-causing organisms varies among geographical areas and over time. New Zealand’s susceptibility data demonstrated a high susceptibility to penicillin. A formulation containing this antimicrobial was administered to healthy lactating cows milked once or twice daily. The concentrations of penicillin in milk were above the minimal inhibitory concentrations for the entire inter-dosing interval. Doubling the number of treatments or milking once-a-day resulted in a significantly increased time above the minimal inhibitory concentrations. The number of new infections is greatest during the early dry period in mature cows and in the pre-calving period in both heifers and mature cows. Pre-partum administration of delayed release antimicrobial formulations in heifers decreased the incidence of clinical mastitis and resulted in better reproductive performance, but not in increased milk production, when compared to control heifers. More effective prevention of new infections within the dry period was achieved by administering a novel teat sealant to mature cows when compared to a commercial teat sealant and untreated controls. Strategies for shortening the duration of intramammary infections and decreasing the number of affected cows at the start of lactation investigated in this thesis should reduce the prevalence of mastitis on dairy farms in New Zealand.