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Item Identification of risk factors for ewe mortality during the pregnancy and lambing period in extensively managed flocks(BioMed Central Ltd, 2023-12-06) Flay KJ; Chen AS; Yang DA; Kenyon PR; Ridler ALBACKGROUND: Ewe mortality during pregnancy and lambing is an issue for sheep producers globally, resulting in reduced productivity and profitability, compromised ewe welfare, and poor consumer perception. Despite these negative consequences, there was little investigation into factors associated with ewe death during this time. Therefore, this study aimed to assess associations between ewe body condition score (BCS), weight, reproductive parameters, and risk of mortality during pregnancy and lambing. METHODS: Four cohorts from three commercial New Zealand farms participated, with 13,142 ewe lambs enrolled and followed over time. Data were collected for five consecutive lambings. Visits aligned with key on-farm management times, specifically: prior to breeding, at pregnancy diagnosis (PD), prior to lambing (set-stocking), and, at weaning of their lambs. At each visit, ewes were weighed, BCS assessed and reproductive status was recorded when relevant (litter size at PD and lactation status after lambing). Ewes that died or were culled were recorded, and any ewes that were absent from consecutive visits were presumed dead. Logistic regressions were developed to assess the relationship between weight and BCS at each visit, PD result (single or multiple-bearing) and lactation status (wet or dry) in each year, and, risk of mortality during the pregnancy and lambing period in each year. RESULTS: In the PD to weaning period, mortality incidence ranged from 6.3 to 6.9% for two-tooth (18-months-old at breeding) to mixed-age (54-months-old at breeding) ewes. For ewe lambs (7 to 8-months-old at breeding), mortality was 7.3% from set-stocking to weaning. Heavier ewe lambs at PD were less likely to die during lambing (OR: 0.978, p = 0.013), as were those with greater set-stocking BCS. In subsequent years, BCS was a predictor of ewe death, with odds of mortality greatest for ewes < BCS 2.5. Additionally, for poorer BCS ewes, increasing weight reduced risk of mortality, but there was no impact of increasing weight in greater BCS ewes. CONCLUSIONS: This study identified risk factors associated with ewe mortality during the pregnancy and lambing period. Flock owners can use these to either cull at-risk ewes or proactively intervene to reduce likelihood of mortality, thereby improving flock productivity, profitability and welfare.Item Reproductive consequences of genetic improvement in clean fleece production in ultrafine Merino ewes : 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, 2023) Ramos, ZullyTo date, genetic improvement of Uruguayan Merino sheep has focused on selection for reduced fibre diameter (FD) and increased clean fleece weight (CFW) and live weight (LW). The effects of selection for these traits on ewe productive and reproductive performance have not been studied in Uruguay. The aim of this thesis was to evaluate the impact of a long-term selection program applied in an Uruguayan Merino flock between 1999 and 2018. Phenotypic responses of yearling lambs and adult ewes across 20 years of selection demonstrated that selection strategies applied in the flock resulted in heavier animals that produced heavier and finer fleeces. These phenotypic responses were accompanied by a decrease in body condition score (BCS) at mating, with a small positive change in ewe reproductive performance. Strong positive genetic correlations were found between yearling and adult expressions of FD, CFW, and LW. The genetic relationships between FD and reproduction traits were negligible. There were generally favorable genetic correlations between LW and reproduction traits. The genetic relationships between adult CFW and ewe reproductive performance were unfavorable. Genetic trends indicated that the breeding strategies applied during the study period were effective in improving genetic merit in the traits under selection (FD, CFW, and LW) and caused only marginal genetic changes in BCS at mating and ewe reproductive performance. A total of 13, 22, 42, 22, 24 and 29 genomic regions were significantly associated with FD, CFW, LW at mating, BCS at mating, pregnancy rate, and lambing potential, respectively. The results obtained in this thesis will be used to refine the breeding programmes for Merino sheep in Uruguay in the future.Item 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, EmmanuelleBreeding 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.Item Broken shoulders in dairy heifers in New Zealand : investigating the relationship between live weight and bone morphology in the bovine forelimb : 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, 2021) Gibson, MichaelaSpontaneous humeral fractures in first lactation dairy heifers are a significant economic and welfare issue in the New Zealand dairy industry. With approximately 4% of dairy farms being affected and, within farm, up to 25% of replacement heifers lost, the cost to the dairy industry is estimated to be over $10 million. Preliminary observations from Dittmer et al. (2016), showed the presence of growth arrest lines in bones from affected heifers, indicating a period of malnutrition in the heifer’s life. However, with little known about how heifer’s bones grow within the New Zealand pastoral system, it is difficult to identify developmental time periods that have the greatest impact on long bone growth and, therefore, greatest potential to affect the risk of fracture. Therefore, the aim of this thesis was to investigate the relationship between live weight and bone morphology in the bovine forelimb to identify potential risk periods for spontaneous humeral fractures in first-lactation dairy heifers. In this thesis, the metacarpus and humerus were opportunistically collected from cattle from a variety of experiments carried out at Massey University and from samples submitted from farms throughout New Zealand. Measures of bone morphology in the metacarpus were highly correlated with the same measure in the humerus (R²=0.89-0.98). Measures of the humerus and metacarpus were also highly correlated with live weight at all ages. However, the relationship between bone and live weight changed over time demonstrating differences in bone maturity. Distal regions of the forelimb such as the metacarpus matured by one year of age as indicated by a different relationship between live weight and pQCT measures of the humerus at 24 months compared with 8-12 months of age. However, proximal regions of the forelimb such as the humerus continued to grow after a year of age. Differences in proximal and distal bone growth were reflected in the pattern of stature growth. A cohort of dairy heifers (Holstein Friesian, Jersey, and Holstein-Friesian cross Jersey) were measured for live weight, height, wither-rump length, girth, and distal and proximal forelimb length (stature) from birth to 15 months of age. As live weight increased, the contribution of the distal limb to increases in height decreased, which is consistent with knowledge that physeal closure in cattle occurs earlier in distal limb bones, such as the metacarpus, than in proximal limb bones, such as the humerus. Finally, bones collected from heifers affected and unaffected by spontaneous humeral fractures were compared and the effect of copper status on bone measures was examined. The mid diaphysis of the humerus of the affected group had reduced cortical bone mineral density (p<0.05) and a trend for reduced cortical content and total bone content which contributed to a reduced stress-strain index. A trend for reduced bone length in affected humeri provides additional support for the hypothesis of inhibited humeral growth. Heifers with low liver copper concentration had reduced humeral length and reduced cortical bone mineral density (p<0.05). Growth and fracture data presented in this thesis support the hypothesis that the most likely developmental period in which inadequate bone growth occurs in heifers subsequently affected by humeral fracture is in the months leading up to the event, which coincides with the animal’s second winter.Item Improving the measurement of live weight and body condition score in sheep : a thesis presented in fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science, Massey University, Turitea, Palmerston North, New Zealand(Massey University, 2021) Semakula, JimmyLiveweight (LW) and body condition score (BCS) are important performance indicators in sheep management, providing a basis for decision making. Therefore, accurate measurement of these traits is imperative. The overall aims of this thesis were to 1) Determine the factors affecting the rate of LW loss of fasting sheep, 2) derive equations to predict LW and LW change over a short time period (1 to 8 hours), 3) evaluate the factors affecting the relationship between ewe LW and BCS, and 4) derive equations for predicting ewe BCS. In the LW studies, lambs were offered three herbage availability levels (Low, Medium and High) in autumn or winter. Similarly, mixed-aged ewes at different physiological states were offered two herbage levels (Low or High). These studies were conducted in two stages: A) calibration stage and B) validation stage. Equations to predict without delay LW were developed at the calibration stage and validated on data collected from independent ewes from different farms. The rate of ewe LW loss was influenced by herbage type and availability, and season. Further, in pregnant ewes, liveweight loss was influenced by the stage of pregnancy, but not pregnancy-rank. Applying correction equations improved the prediction accuracy of without delay LW estimates up to 55% and 69% in ewe lambs and mixed aged ewes compared with using the delayed weights, respectively. For the BCS studies, LW and BCS data of ewes were collected at regular times of the annual production cycle until they were six years of age. Using a ewe’s LW and BCS records to predict their current BCS using a linear model gave moderately accurate estimates. A different dataset, which included foetal- and fleece weight-adjusted LW and height at withers was then used. It was found that equations combining LW, LW change and previous BCS explained more variability in current BCS and were more accurate than LW-alone based models but the addition of adjusted LW and height at withers gave no further benefit to the BCS prediction models. Applying machine learning classification algorithms such as extreme gradient boosted trees and Random forest on a 3-point BCS scale achieved very good BCS prediction accuracies (> 85%). These combined findings provide useful prediction equations that could be incorporated into weighing systems, which along with EID would improve sheep production by aiding management decision making.Item Determining the utility of adolescent live weight data to predict two-year-old live weight in New Zealand dairy cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science, Master of Science in Animal Breeding and Genetics at Massey University, A L Rae Centre for Animal Breeding and Genetics, Waikato, New Zealand(Massey University, 2019) Stephen, Melissa AnneThe purpose of this research was to establish the utility of adolescent live weight data measured across cohorts of growing animals for predicting live weight in first lactation. Live weight is associated with the growth and maintenance feed requirements of a cow. Selection that simultaneously takes account of milk income and feed requirements of dairy cattle can increase future farm profitability. Estimated breeding values (EBVs) for mature cow live weight are currently predicted using Live weight phenotypes measured during actation. Breeding companies in NZ actively measure the first lactation live weight of a small proportion of the nation’s dairy cows—the daughters of their bulls—to improve their ability to identify superior bulls. Accurate EBVs obtained at an earlier age can allow reliable selection of superior young bulls which would shorten the generation interval, increasing the rate of genetic progress. The purpose of this research was to determine the utility of adolescent live weight (i.e. live weight prior to first lactation) for predicting variation in live weight measured in first lactation. We completed two studies. In the first study (Section 4), we produced the (co)variance parameters for live weights measured at four ages, from six months old through to first lactation. Our hypothesis for this study was that live weight measured through adolescence would share a strong positive genetic relationship with live weight measured during lactation. Our results support this hypothesis, as estimates of genetic correlations between weights at different ages ranged from 0.79 to 0.97. In the second study (Section 5), we produced live weight EBVs using live weight measured though adolescence. For comparison, we produced EBVs using just live weight measured during first lactation. Our hypothesis was that the accuracy of the live weight EBVs would be improved by including adolescent live weight. Our results showed that including adolescent live weight phenotypes improved the accuracy of the live weight EBVs for animals with adolescent live weights, and their progeny. We concluded that adolescent live weights are a useful predictor of live weight later in life, and should be incorporated as a predictor trait for the national live weight EBV in NZ.Item Early weaning of twin-born lambs onto a herb-clover mix containing plantain (Plantago lanceolata), chicory (Cichorium intybus), red clover (Trifolium pratense) and white clover (Trifolium repens) : 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) Ekanayake, LukshmanEarly weaning of lambs may be a useful management tool when either herbage quality, or quantity, limits lamb growth. Herb-clover mixes containing chicory, plantain, red clover and white clover have been shown to improve the growth of suckling lambs and those weaned at a traditional age compared to ryegrass-clover based pastures. The objectives of this thesis were to examine; 1) the effect of lamb live weight at early weaning on their subsequent growth on a herb-clover mix; 2) the response of early weaning of lambs onto a herb-clover mix when ryegrass-clover based pasture herbage masses were restricted rather than ad-libitum; 3) the effect of weaning lambs at different minimum live weights (16 kg then 14 kg); 4) the impact of early exposure of lambs to a herb-clover mix prior to early weaning on their growth post weaning, and 5) to characterise the nutritional composition of the herb-clover mix during the late spring to autumn period. Lambs weaned early onto a herb-clover mix, at a minimum weight of 16 kg at approximately 50 days of age, had the potential to grow at a similar rate to unweaned lambs on a ryegrass clover based pasture. This was more apparent when herb-clover mix had a high chicory (57%) and clover content (14%) or there was a low (< 5%) clover content in the ryegrass-clover based pasture. In first year of the study light lambs (< 18 kg) grew 50 g/day slower than heavy lambs (18-23 kg), however, in the second year they grew at a similar rate . Weaning lambs less than 16 kg onto a herb-clover mix, therefore, should be undertaken with caution. Further, the advantages of early weaning were enhanced when the supply ryegrass-clover based pasture resulted in restricted intake of ewes and lambs (< 1200 kg DM/ha). Lambs weaned at a minimum weight of 14 kg at approximately 40 days of age, were found to grow at a similar rate to unweaned lambs on a ryegrass-clover based pasture. Early exposure to a herb-clover mix prior to early weaning had no impact on subsequent growth of early-weaned lambs.Item Phenotypic relationship between milk fatty acid profile and live weight change in early lactation in New Zealand dairy cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science, Institute of Veterinary, Animal and Biomedical Sciences, Palmerstone North, New Zealand(Massey University, 2016) Mkunda, VedastusThe phenotypic relationship between milk fatty acid (FA) profile and live weight (LW) change in early lactation in grazing Friesian x Jersey (FxJ) cows was investigated in this study. Data used in this study compromised of 73,040 daily milk yields, 5,936 fortnightly herd-tests for fat, protein and lactose, 41,981 daily live weights, and 882 determinations of FA profiles from 300 second-lactation FxJ crossbred cows recorded during the production season 2003-04. Cows were classified based on the magnitude of LW change from calving to peak lactation into three groups: cows with low live weight loss (L; below -0.012kg), medium live weight loss (M; below -0.174kg and high live weight loss (H; below -0.340kg). LW change was considered as a proxy for energy balance. Correlations between LW change and individual FAs or group of FAs were estimated at the three stages of lactation (early, mid and late). Stage of lactation affected significantly (P>0.05) the concentration of all FAs considered in this study, except the concentration of C20:0. Higher concentration of C18:0 and C18:1 cis-9 was observed in early lactation relative to other lactation stages. Compared to the L and M cows, the H cows had higher concentration of C18:1 cis-9 in early lactation. Live weight loss in early lactation was significantly associated with higher concentrations of unsaturated (r = -0.19), long-chain FA (r = -0.17), C17:0 (r = -0.14), C18:1 cis-9 (r = -0.20) and C18:3 cis-9, cis-12, cis-15 (r = -0.21), but live weight loss was significantly associated with lower concentrations of saturated FA (r = 0.18), medium-chain FA (r = 0.16), C12:0 (r = 0.24), C14:0 (r = 0.17) and C15:0 (r = 0.22). The association between LW changes in early lactation and most of the FAs were not significant in mid and late lactation. If determination of FA can be implemented using mid-infrared spectroscopy, a conclusion from this study is that concentration C18:1 cis-9 in early lactation can be used as indicator of live weight change (energy balance). Further studies are required to evaluate the inclusion of concentrations of FAs in breeding programs to improve fertility in seasonal grazing dairy cattle.Item Does meeting physical activity guidelines in normal weight females influence body fatness? : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand(Massey University, 2014) Swift, RichardPurpose: To investigate the associations among objectively measured physical activity and markers of body composition in normal weight, New Zealand European women. Methods: Anthropometric measures were performed in 107 women aged 16-45 years with a BMI between 18.5 to 25 kg/m2. Accelerometers were worn over 7 days to assess sedentary time (<100 counts per minute), light (100 - 2019), moderate (2200 - 5998) and vigorous (>5999) physical activity. Independent t-tests were used to compare associations between participants with normal (<30%) and high (=30%) body fat. Partial correlations examined the independent associations of physical activity behaviours on body fat. Results: Participants with normal body fat completed significantly more moderate to vigorous physical activity (MVPA) minutes per week (P = .002) and MVPA% (P =.021). Achieving current physical activity recommendations of = 150 mins/week of MVPA, resulted in lower body fat (P =.038). Achieving =300 mins/week of moderate physical activity showed a trend towards significance for lower body fat (P = .076), while achieving =150 mins/week of vigorous activity showed significantly lower body fat% (P = .022). Partial correlations determined the significance of MVPA on body fat% independent of sedentary (r [104] = -.258 P = 0.008) and light activity (r [104] = -.273 P = 0.005). Conclusion: Achieving current exercise recommendations was associated with lower body fat % in normal weight women. Our data suggest this association is stronger for vigorous activity, and is independent of the amount of sedentary activity achieved. Increasing vigorous physical activity may be important for improving body composition in this group.Item A study of the relationships between growth, carcass and meat characteristics of Angus steers : 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, 1982) Msechu, James Kundael KileghuaGrowth, defined as change in weight, may be considered the most important single characteristic of slaughter cattle. Fast-growing cattle may have better food conversion and reach slaughter early. The end-products in a beef production business, namely, carcass and meat, have properties which determine consumer acceptability. This study focussed attention on growth, carcass and meat characteristics in cattle. Literature was reviewed on factors that influence variability in these traits and relationships reported in the literature between some of the traits were summarised. Records on 117 Angus steers born in 1975 and 1976 (years 1 and 2) were analysed by the least squares method of fitting constants. Data included birth weight, calf milk consumption pre-weaning average daily gain (ADG), weaning weight, post-weaning ADG, yearling weight, 2-year weight, finish (30-month) weight, carcass weight, kidney and channel fat weight, eye muscle width, depth, and area, fat depth, fat trim percentage, intra-muscular fat percentage, sarcomere length, meat tenderness, muscle pH, and colour, lean percentage and bone percentage. Fixed-effects constants fitted to growth data were: herd, age of dam and peri-natal treatment (calving on pasture or sawdust pad). Covariance analysis was adopted with 3 covariates: dam autumn liveweight, calf birth weight, and milk consumption. Factors fitted to post-slaughter data were: maturity, slaughter lot and pre-slaughter fasting, with 3 covariates, carcass weight, pre-weaning ADG, and post-weaning ADG. Results were inconsistent between years. Therefore, few factors were conclusively judged to be important sources of variation in the traits studied. Herd influenced milk consumption (P<0.05) and pre-weaning ADG in year 1, and weaning and yearling weight (P<0.01) in year 2. Age of dam did not affect growth traits (P<0.10). Treatment was unimportant to pre-weaning growth in both years, but year 1 analyses suggested that it affected post-weaning ADG (P<0.01) and finish weight (P<0.05). This result may be attributed to chance. Regression on dam weight was non-significant for all growth traits. Calf birth weight was found to be an important factor as far as various growth traits in year 2 were concerned, namely, weaning weight (P<0.01), and milk consumption, pre-weaning ADG and yearling weight (P<0.05). Regression of weaning weight on birth weight approached significance (P<0.10), but birth weight was otherwise unimportant in year 1. Milk consumption influenced weaning weight (P<0.05) in year 1; approached significance for its effect on pre-weaning ADG and yearling weight in year 1, and weaning and 2-year weight in year 2 (P<0.10). Maturity did not affect post-slaughter characteristics other than eye muscle depth (P<0.05) in year 2. Slaughter lot was responsible for variation in eye muscle width (P<0.001) and dressing-out percentage (P<0.01) in year 1; dressing-out percentage and bone percentage (P<0.001) in year 2. Four-day pre-slaughter fasting affected few carcass or meat traits adjusted for carcass weight by covariance analysis. The results were inconsistent between years. In year 1, fasting affected dressing-out percentage (P<0.001) only, while in year 2 such effect was not apparent (P<0.10), but it was appreciable on other traits: eye muscle width and meat tenderness (P<0.05) and sarcomere length (P<0.001). Regression of various traits on carcass weight was significant: dressing out percentage, kidney and channel fat, fat depth, intramuscular fat percentage, fat trim percentage, eye muscle depth, eye muscle area, sarcomere length, and bone percentage in year 2; it was significant for dressing-out percentage and kidney and channel fat in year 1. Pre- and post-weaning ADG were less important covariates: the former was significant to eye muscle depth, dressing-out percentage, intra-muscular fat percentage and bone percentage in year 2, but non-significant in year 1. The latter approached significance in eye muscle area, dressing-out percentage, fat trim percentage and bone percentage in year 2 (P<0.10). Residual sums of squares were used to estimate phenotypic correlations between traits studied. Correlation coefficients between growth traits were positive and medium to high except those between early growth (pre-weaning ADG, and birth, and weaning weights) and post-weaning ADG, which were negligible. Pre-weaning ADG and weaning weight had a perfect correlation coefficient (r = 1.0) in both years. Estimates between growth and carcass traits varied widely; notable were those for post-weaning ADG, 2-year weight, and finish weight with carcass weight, which were high in both years (r = 0.86, 0.80; r = 0.80, 0.85; and r = 0.92, 0.92, respectively). Carcass traits were mostly positively correlated, with low to medium coefficients between them. Lean percentage had a strong negative correlation with fat trim percentage (r = -0.71), but bore little relationship with other traits. Correlation coefficients between carcass and meat traits were mostly positive, but low and inconsistent between years. Carcass weight was related to most fatness attributes of the carcass and meat. Most meat traits were positively correlated with each other with low and medium correlation coefficients.