Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Preferences in traits and management characteristics for dairy-beef animals from a survey of New Zealand farmers(Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2025-05-19) Sneddon NW; Corner-Thomas RA; Kenyon PR; Brier DThere are three parties involved in the expansion of dairy-beef or beef-on-dairy within New Zealand, they are namely, beef breeders, dairy farmers and beef finishers. Within these three groups, there are different requirements for an animal within each those industries. In 2022, Beef + Lamb New Zealand conducted a survey to collect responses from 121 respondents across these 3 parties, to gauge farmer preferences. The survey contained questions relating to the management of young cattle from birth through to weaning or sale (depending on management practice), and then from weaning or purchase through to finishing. All farmers were asked what traits they selected for in bulls, and what they based purchasing decisions on. The results showed a series of trends, related to breed choice, price and perceived benefit to their farming system. Calves from dairy cattle that had some Jersey genetics were seen as a finishing risk and were less attractive to finishing operations. There appeared to be a disconnect between the preferences of dairy and beef finishing operations, with sire selection having opposite selection criteria. The results of this survey indicate that work needs to be taken to align the goals of both beef finishers and dairy farmers.Item The genetic parameters of racing success and longevity in the New Zealand Thoroughbred racing industry(Taylor and Francis Group on behalf of the Royal Society Te Apārangi, New Zealand, 2025-04-23) Chin YY; Sneddon NW; Gibson MJ; Legg KA; Gee EK; Rogers CW; Handcock RWithin the Thoroughbred industry, individual success can be measured with races and prize money won. At an industry level, there is a requirement for horses to be able to race from a young age and have a sustained injury-free career. Therefore, the variance components of such traits were investigated within ASReml for 26,920 New Zealand Thoroughbred racehorses. Age at first competitive high-speed event (trial or race start) had high heritability (h2= 0.52 ± 0.02), and an inverse genetic correlation with career earnings (−0.40 ± 0.05) and number of wins (−0.35 ± 0.06). Career earnings (h2 = 0.24 ± 0.02) had positive genetic and phenotypic correlations (0.59 ± 0.004) with career length, implying that racing success could be a useful selection proxy for career length. Horses that started earlier had longer career length (−0.21 ± 0.07,–0.18 ± 0.01). The low heritability of career length (0.11 ± 0.01) reflects considerable environmental influence on this trait, reinforcing the importance of early training and exercise in increasing career length. Therefore, the optimal strategy is a selection programme focusing on racing success, which improves commercial appeal and is genetically correlated with longevity. A training and racing programme that encourage an early competitive high-speed event would optimise the phenotypic development of the musculoskeletal system and reduce injury risk.Item Estimating Heritabilities and Breeding Values From Censored Phenotypes Using a Data Augmentation Approach.(Frontiers Media S.A., 2022-07-25) Stephen MA; Cheng H; Pryce JE; Burke CR; Steele NM; Phyn CVC; Garrick DJ; Cánovas ATime-dependent traits are often subject to censorship, where instead of precise phenotypes, only a lower and/or upper bound can be established for some of the individuals. Censorship reduces the precision of phenotypes but can represent compromise between measurement cost and animal ethics considerations. This compromise is particularly relevant for genetic evaluation because phenotyping initiatives often involve thousands of individuals. This research aimed to: 1) demonstrate a data augmentation approach for analysing censored phenotypes, and 2) quantify the implications of phenotype censorship on estimation of heritabilities and predictions of breeding values. First, we simulated uncensored phenotypes, representing fine-scale "age at puberty" for each individual in a population of some 5,000 animals across 50 herds. Analysis of these uncensored phenotypes provided a gold-standard control. We then produced seven "test" phenotypes by superimposing varying degrees of left, interval, and/or right censorship, as if herds were measured on only one, two or three occasions, with a binary measure categorized for animals at each visit (either pre or post pubertal). We demonstrated that our estimates of heritabilities and predictions of breeding values obtained using a data augmentation approach were remarkably robust to phenotype censorship. Our results have important practical implications for measuring time-dependent traits for genetic evaluation. More specifically, we suggest that data collection can be designed with relatively infrequent repeated measures, thereby reducing costs and increasing feasibility across large numbers of animals.Item The pattern of breeding and management within the New Zealand Thoroughbred breeding industry 2005-2015. (II) The mare population(CSIRO Publishing, 2024-01) Chin YY; Rogers CW; Gee EK; Stafford KJ; Cameron EZContext: The New Zealand Thoroughbred breeding industry is heavily focused on producing horses for the export market and there has been a reduction in the number of horses racing in the past 20 years. The impact of these production constraints, and changes in production focus, have not been described at a national herd level. Aim: To describe the breeding management, reproductive performance, and careers of the New Zealand Thoroughbred broodmare herd during the 2005/06-2015/16 breeding seasons. Methods: The demographics, population structure, reproductive efficiency, breeding management and career descriptors of Thoroughbred mares were examined using descriptive analysis. Gestation length was modelled using a linear mixed effects model. The impact of different variables on breeding career were quantified by calculating odds ratio. Results: There was a consistent reduction in the size of the national broodmare herd over the 10 years investigated. Half of the mares not retained for breeding were mares that were breed to low-cost stallions. Despite a short (∼100 days) commercial breeding season few (20%) mares were mated early in the season (September), with most mating (70%) occurring between October and November. The 27 days mean foaling to conception interval (FCI) suggests that FCI was artificially shortened and most pregnancy was achieved within first oestrus cycle post-partum. Mare career length and lifetime productivity was positively associated with the stud fee of the first stallion that the mare was mated to and number of foals registered for racing. Conclusion: Mare replacement and loss within the national herd was disproportionately associated with mares that were producing foals for a contracting domestic racing market. There was a constricted breeding season with most mares being mated within the first oestrous cycle post-partum. Mare retention and breeding success were positively associated with the service fee of the sire and progeny that had raced, reflecting the commercial pressure of the industry on mare management. Implication: The changes in the broodmare herd and management reflects the increasing proportion of the industry focusing on breeding foals that will appeal to the export market. The economic drivers for early born foals provide management challenges as these are not aligned with the optimal reproductive season of the horse.Item Long-term changes in the breeding biology of a New Zealand bellbird population suggest plasticity in life-history responses to ecological restoration(2021-01-19) Roper MM; Aaron MTH; Brunton DHEcological restoration projects provide excellent opportunities to study how animals adapt their life-history strategies in response to changeable environments. A fundamental way animals can optimise reproductive success in changing conditions is trading-off aspects of their breeding system. The New Zealand bellbird ( Anthornis melanura ) has had a long-term presence on the small restoration island, Tiritiri Matangi Island (Tiri), spanning the island’s degraded agricultural past to its current extensively restored state. We studied the breeding biology of this bellbird population to assess how their reproductive life-history strategies have responded over time to the restoration on Tiri. We compared the current breeding data (2012–2016) of the bellbirds with data from between 2001–2010 (including Baillie, 2011, Cope, 2007), and from 1977–1978 (Anderson and Craig, 2003), prior to the island’s restoration. We also explored associations between abiotic/biotic factors and bellbird reproductive success for the most recent period (2012–2016). Our main finding was that clutch size significantly declined over time from a mean of 3.6 to 2.4 eggs per nest and this decline correlated with increasing population density. This is consistent with a density dependent effect, although further data are required to empirically test this conclusion. Overall, the earliest spring laying dates were in late August and the latest extended to January, with all chicks fledged by the end of February. Nest success was 47% (range 40 – 54%) across 2012–2016, falling within a similar range as previous studies. We found little effect of year, weather, parental age or morphometrics on reproductive success. We observed directional change in patterns of parental investment between 1977–1978 and 2012–2016; in 2012–2016, parents persisted with raising single broods rather than abandoning and re-nesting to raise larger broods. These results suggest that the bellbirds’ life-history traits are plastic in response to local conditions which provides an advantage when repopulating a regenerating or changing habitat.Item The Effect of Age of Dam and Birth Rank on the Reproductive Performance of Ewes as One- and Two-Year-Olds.(10/03/2021) Pettigrew E; Hickson R; Morris S; Kenyon P; Corner-Thomas R; Haslin E; Blair HCurrently, 30-43% of New Zealand sheep farmers breed their ewe lambs, but few retain the offspring as replacements for their flock. No difference in lamb production as a yearling among singletons and twins born to ewe lambs and twins born to mature ewes has been reported, provided the ewe lambs had reached the 60-65% of their likely mature weight prior to breeding at seven to eight months of age. The aim of this experiment was to determine the lamb production from singletons and twins born to ewe lambs and twins born to mature ewes during their first two years of lambing. The experiment included 8-month-old ewes born as twins to mature ewes (M2, n = 135), singletons born to ewe lambs (L1, n = 135), and twins born to ewe lambs (L2, n = 88), bred during the same period to the same rams, over two years. The efficiency of lamb production (total litter weight at weaning divided by the pre-breeding weight of the ewe, for all ewes presented for breeding) after two years of production was not significantly different (p > 0.05) among the groups (0.40 ± 0.02, 0.39 ± 0.02, and 0.39 ± 0.03, for M2, L1, and L2, respectively).