Journal Articles
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Item Stronger Antipredatory Vigilance of Prey to Olfactory Cues From Injured Vulnerable Conspecifics(British Ecological Society and John Wiley and Sons Ltd, 2025-10-06) Simkhada R; Kundun J; Sofkova-Bobcheva S; He XZPredation risk is a key evolutionary force shaping prey behaviors and life-history strategies across taxa. Predators often target vulnerable life stages of prey, but how prey females adjust their reproductive strategies in response to cues from injured conspecifics of these stages remains unclear, particularly in haplodiploid species, where mothers can adjust offspring sex ratios in response to social environments. Using the predatory mite Phytoseiulus persimilis and its prey, the spider mite Tetranychus ludeni, we first investigated the stage-specific vulnerability by exposing T. ludeni eggs, deutonymphs, and female adults to P. persimilis for choice. We then tested whether ovipositing T. ludeni females adjusted reproductive performances and survival when exposed to potential predatory cues from those injured conspecifics. Results show that P. persimilis significantly preferred T. ludeni eggs for feeding, indicating their higher vulnerability to predators. T. ludeni females responded most strongly to potential predatory cues from injured eggs, reducing fecundity and producing smaller eggs, but without trading off their longevity. Additionally, when exposed to injured adult cues, T. ludeni females adjusted offspring sex ratios, producing more dispersing daughters by fertilizing more smaller eggs, an evolved strategy to escape from the risky environments. In contrast, egg hatching and immature survival were unaffected by conspecific cues. Our results demonstrate that T. ludeni females may discriminate among cues from injured conspecifics of different life stages, with the strongest vigilance elicited by cues from the most vulnerable stage (i.e., eggs). This study highlights the role of indirect, life stage-specific cues in shaping antipredator strategies and reveals that non-consumptive effects of predation risk could influence prey population dynamics in ways beyond direct predation. Our findings provide a mechanistic understanding of reproductive plasticity in haplodiploid systems, offering new insights into how prey balance current and future reproductive investments under predation pressure.Item Use of hormones on New Zealand dairy farms: an analysis of the results from a survey of farmers and a survey of veterinarians(Taylor and Francis Group on behalf of the New Zealand Veterinary Association, 2025-07-09) Laven RA; Cuttance EL; Chambers GAims: To survey New Zealand dairy farmers and veterinarians on their attitude and use of reproductive hormones in treating cows identified as non-cyclers. Whilst hormones have been identified as effective tools in assisting reproduction in dairy cattle, there is widespread but anecdotal concern about their cost-effectiveness and a lack of high-quality information on the attitude and practices around hormone use on New Zealand dairy farms. Methods: Electronic links to separate farmer and veterinary survey forms were sent to all dairy clients and all veterinary employees of five, convenience-selected veterinary practices across New Zealand. Using closed, open, and Likert-style questions, the surveys covered cost-effectiveness of hormonal interventions, value judgements on their use, and impact on the public perception of dairy farming. Results: Usable surveys were returned by 424 farmers and 70 veterinarians. Response rates are not known as denominator data were not sought. Of the farmers, 253/424 (60%) reported using hormone treatments, with 153 (36%) primarily using them before mating started. However, only 163 (38%) thought treatment was cost-effective, compared to 65/70 (93%) veterinarians. Beliefs around cost-effectiveness affected use: 8/171 (5%) farmers who never used hormones believed they were cost-effective, compared to 38/94 (40%) who used hormones occasionally and 117/159 (74%) who used them routinely. Other reasons put forward by farmers for not using hormones included “breeding infertility”, “not natural”, and “not treating the cause”. Farmer and veterinary opinion also varied around the trajectory of hormone use. Amongst veterinarians, 12/70 (17%) thought use should decrease compared to 271/424 (64%) farmers, while 19/70 (27%) veterinarians thought use should increase compared to 21/424 (5%) of farmers. Conclusions: The results suggest a disconnect around hormone use between the participating veterinarians and farmers. Many farmers did not believe hormone use was cost-effective, despite strong evidence to the contrary. As other reasons for not using hormones were also cited, and as most farmers believed hormone use should decrease, it seems unlikely that further education on cost-effectiveness will change practice. Rather, it could increase the proportion who think veterinarians benefit financially more from hormone use. Clinical relevance: Veterinary focus on maximising synchronisation use and efficacy is bypassing a significant proportion of dairy farmers. There is an opportunity for veterinarians to focus on what their clients want and work with them to improve herd fertility without relying on hormones to fix management problems.Item Where do all the ewes go? Ewe culling and mortality in 34 sheep flocks in New Zealand.(Taylor and Francis Group, 2024-10-17) Ridler AL; Corner-Thomas RA; Mote S; Morgan S; Kenyon PR; Flay KJAims To describe rates of and reasons for culling and mortality of ewes between breeding and mid-lactation on New Zealand sheep farms; to investigate associations of these variables with farm demographic variables; and to describe rates of and reasons for culling of ewes at weaning. Methods Participants were a convenience sample of 34 farms from across New Zealand. Demographic data were initially collected for each farm via a questionnaire administered in-person to the flock owner or manager. During approximately 8 months from breeding to mid-lactation, ewe tally, culling and mortality data were collected and used to calculate various parameters related to flock performance and to investigate associations. During the main ewe-culling event at weaning, ewe-culling data were collected from 29/34 flocks participating in the study. Results There was considerable variation between flocks, but the between-flock mean replacement percentage was 29.2 (SD 5.0)%. Overall, a between-flock mean of 10.5 (SD 4.6)% of ewes presented for breeding were culled or dead/missing by mid-lactation and thus did not rear any lambs. Additionally, from 27 flocks that reported data on ewes’ success at rearing lambs, a between-flock mean of 3.9 (SD 2.5)% of ewes that remained alive at mid-lactation failed to rear any lambs, resulting in an overall between-flock mean loss of 23.1 (SD 6.3) potential lambs per 100 ewes. Two-thirds of ewe mortalities between breeding and mid-lactation occurred during the lambing period. Model results showed flocks with higher pregnancy scanning percentages had lower rates of culling and mortality between breeding and mid-lactation. However, apart from farm contour, from breeding to mid-lactation there were no associations for culling and mortality with farm size, flock size, number of ewes per labour unit, whether ewe hoggets (7–9 months of age) were presented for breeding, or duration of the breeding period. A between-flock mean of 16.5 (SD 8.3)% of ewes present at weaning were culled, and among mixed-age ewes, the most common reasons for culling at this time were age, incisor teeth defects and udder defects. Conclusions To reduce unnecessary ewe culling and mortality, attention should be focused on maximising conception rates, ensuring judicious culling decisions, optimising body condition score, and identifying farm-specific causes of death over the lambing period to facilitate targeted intervention strategies. Clinical relevance Identifying why and when ewes exit flocks, and comparing it with the data presented here, will facilitate the development of flock-specific interventions to reduce ewe culling and mortality.Item Genetic and phenotypic relationships between ewe reproductive performance and wool and growth traits in Uruguayan Ultrafine Merino sheep.(Oxford University Press on behalf of the American Society of Animal Science, 2023-03-07) Ramos Z; Garrick DJ; Blair HT; De Barbieri I; Ciappesoni G; Montossi F; Kenyon PRThis study reports genetic parameters for yearling and adult wool and growth traits, and ewe reproductive performance. Data were sourced from an Uruguayan Merino flock involved in a long-term selection program focused on reduced fiber diameter (FD), and increased clean fleece weight (CFW) and live weight (LW). Pedigree and performance data from approximately 5,700 mixed-sex yearling lambs and 2,000 mixed-age ewes born between 1999 and 2019 were analyzed. The number of records ranged from 1,267 to 5,738 for yearling traits, and from 1,931 to 7,079 for ewe productive and reproductive performance. Data on yearling and adult wool traits, LW and body condition score (BCS), yearling eye muscle area (Y_EMA), and fat thickness (Y_FAT), and several reproduction traits were analyzed. The genetic relationships between FD and reproduction traits were not different from zero. Moderate unfavorable genetic correlations were found between adult CFW and ewe lifetime reproduction traits (-0.34 ± 0.08 and -0.33 ± 0.09 for the total number of lambs weaned and total lamb LW at weaning, respectively). There were moderate to strong positive genetic correlations between yearling LW and all reproduction traits other than ewe-rearing ability (-0.08 ± 0.11) and pregnancy rate (0.18 ± 0.08). The genetic correlations between Y_EMA and reproduction traits were positive and ranged from 0.15 to 0.49. Moderate unfavorable genetic correlations were observed between yearling FD and Y_FAT and between adult FD and BCS at mating (0.31 ± 0.12 and 0.23 ± 0.07, respectively). The genetic correlations between adult fleece weight and ewe BCS at different stages of the cycle were negative, but generally not different from zero. This study shows that selection for reduced FD is unlikely to have any effect on reproduction traits. Selection for increased yearling LW and Y_EMA will improve ewe reproductive performance. On the other hand, selection for increased adult CFW will reduce ewe reproductive performance, whereas selection for reduced FD will negatively impact body fat levels. Although unfavorable genetic relationships between wool traits and both FAT and ewe reproductive performance existed, simultaneous improvements in the traits would occur using appropriately designed indexes.Item Commercial equine production in New Zealand 4: welfare implications of the New Zealand production systems(CSIRO Publishing, 2023-07-10) Rogers CW; Legg K; Gibson M; Gee EK; Bryden WFrom racehorses to family pets, equine production and management is primarily pasture-based in New Zealand. Pasture-based equine production systems largely reflect the horse’s ecological niche and have a unique set of management and welfare challenges. This review examines the potential welfare issues related to the management of horses in New Zealand. The economic value of horses varies greatly depending on their usage, which covers a wide spectrum from pest species (e.g. feral horses) to production (e.g. racehorses) and companion animals (e.g. leisure and sport horses). The view of where the horse is positioned on this spectrum may cause differing welfare threats to horses, due to the economic considerations, which drive the majority of welfare and managemental decisions. The organisation, management, racing and wastage metrics of the Thoroughbred racehorse industry are well documented, and the benefits of the pasture-based system have become evident through less stressful weaning practices and opportunity for early exercise (which has been associated with longer careers and fewer musculoskeletal injuries). Identification of equine-welfare research priorities in New Zealand remains challenging, given the lack of vertical integration of many sectors of the equine industry resulting in fragmented and limited availability of data.Item Genetic Parameters for Maternal Performance Traits in Commercially Farmed New Zealand Beef Cattle(MDPI (Basel, Switzerland), 2021-08-26) Weik F; Hickson RE; Morris ST; Garrick DJ; Archer JA; Michael E DMaternal performance is a major driver of profitability in cow-calf beef cattle enterprises. The aim of this research was to evaluate the inheritance of maternal performance traits and examine the intercorrelation among reproduction, live weight, hip height, body condition and maternal contribution to calf weaning weight in 15-month-old heifers, 2-year-old cows and mature cows in New Zealand beef herds. Data were collected on a total of 14,241 cows and their progeny on five commercial New Zealand hill country farms. Heritabilities were low for reproductive traits in heifers and mature cows (0-0.06) but were greater in 2-year-old cows (0.12-0.21). Body condition scores were lowly (0.15-0.26) and live weights (0.42-0.48) and hip heights (0.47-0.65) highly heritable in heifers, 2-year-old cows and mature cows. Results indicate that 2-year-old cows with higher genetic potential for rebreeding ability may have greater genetic merit for live weight, hip height and body condition as heifers (rg = 0.19-0.54) but are unlikely to be larger cows at maturity (rg = -0.27--0.10). The maternal genetic effect on weaning weight had a heritability of 0.20 and was negatively genetically correlated with body condition score in lactating cows (rg = -0.55--0.40) but positively genetically correlated with rebreeding performance (rg = 0.48).Item Ewe Wastage in New Zealand Commercial Flocks: Extent, Timing, Association with Hogget Reproductive Outcomes and BCS(MDPI (Basel, Switzerland), 2021-03-11) Flay KJ; Ridler AL; Compton CWR; Kenyon PREwe wastage is the combination of on-farm mortality and premature culling. Internationally, there is limited research on actual wastage incidence and causes in commercial sheep flocks. To the authors' knowledge, this is the first study that reports both lifetime wastage and detailed annual wastage in a sample of commercial New Zealand flocks. This study utilized data collected from 13,142 ewes from four cohorts on three commercial New Zealand farms (Farm A 2010-born, Farm A 2011-born, Farm B, Farm C), during the period 2011-2017, as they aged from replacement hoggets to 6-year-old ewes (Farm A and Farm B) or 3-year-old ewes (Farm C). Data collection visits occurred at three or four key management times each year, namely pre-mating, pregnancy diagnosis, pre-lambing and weaning. At each visit, body condition score (BCS) was assessed and any ewes that were culled or had died on farm were recorded. As this was a lifetime study, each ewe was assigned an outcome and corresponding 'exit age'. By the end of the study, all ewes that had exited their respective flocks, were classified as either prematurely culled, or dead/missing, or if still in the flock, as censored, and either the exact date or interval in which they exited the flock was recorded. Semi-parametric competing risk (premature culling vs. dead/missing), interval-censored survival models were developed to: 1. describe the association between hogget reproductive outcomes and risk of subsequent wastage, and 2. assess pre-mating BCS as a predictor of wastage in that production year. Of the 13,142 enrolled ewes, 50.4% exited their respective flocks due to premature culling and 40.0% due to on-farm dead/missing, giving a total of 90.4% that exited due to wastage. Annual mortality incidence ranged from 3.5 to 40.2%. As a hogget, wastage incidence ranged from 7.6 to 45.4%. Pregnancy or rearing a lamb as a hogget did not increase risk of subsequent wastage. In all years, pre-mating BCS was a predictor of ewe wastage, with odds of wastage lower with increasing BCS. Therefore, farmers should focus on improving pre-mating BCS to 3.5/5.0 by assessing ewe BCS at weaning, allowing poorer-BCS ewes to be managed to gain BCS before re-breeding.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 Breeding Ewe Lambs: An Australasian Perspective(MDPI (Basel, Switzerland), 2022-11-19) Kenyon PR; Corner-Thomas RAA number of potential advantages have been identified for breeding ewe lambs at 7 to 9 months of age, including increased lifetime productivity and profitability. However, breeding at this young age in extensive pastoral systems, such as in Australasia, can be associated with a number of disadvantages resulting in uptake of this management procedure being relatively low. This review highlights the known differences between ewe lamb and mature ewe reproductive performance, thus differing in their management. The review then summaries the scientific literature of factors that affect ewe lamb reproductive success, with a focus on recent studies conducted under extensive pasture-based conditions in Australasia. In particular, this review outlines the importance of ewe lamb live weight and body condition score on their productivity. The potential long-term consequences of breeding a ewe lamb at a young age in terms of her future success and that of her offspring to weaning are briefly outlined. In addition, the potential impacts of selecting progeny born to ewe lambs as future replacement ewes are discussed. Throughout this review, optimal management guidelines from prior to breeding the ewe lambs until rebreeding at 2 years of age are provided. Lastly, areas requiring future research are identified and discussed.Item Genomic Regions Associated with Wool, Growth and Reproduction Traits in Uruguayan Merino Sheep(MDPI (Basel, Switzerland), 2023-01-07) Ramos Z; Garrick DJ; Blair HT; Vera B; Ciappesoni G; Kenyon PRThe aim of this study was to identify genomic regions and genes associated with the fiber diameter (FD), clean fleece weight (CFW), live weight (LW), body condition score (BCS), pregnancy rate (PR) and lambing potential (LP) of Uruguayan Merino sheep. Phenotypic records of approximately 2000 mixed-age ewes were obtained from a Merino nucleus flock. Genome-wide association studies were performed utilizing single-step Bayesian analysis. For wool traits, a total of 35 genomic windows surpassed the significance threshold (PVE ≥ 0.25%). The proportion of the total additive genetic variance explained by those windows was 4.85 and 9.06% for FD and CFW, respectively. There were 42 windows significantly associated with LWM, which collectively explained 43.2% of the additive genetic variance. For BCS, 22 relevant windows accounted for more than 40% of the additive genetic variance, whereas for the reproduction traits, 53 genomic windows (24 and 29 for PR and LP, respectively) reached the suggestive threshold of 0.25% of the PVE. Within the top 10 windows for each trait, we identified several genes showing potential associations with the wool (e.g., IGF-1, TGFB2R, PRKCA), live weight (e.g., CAST, LAP3, MED28, HERC6), body condition score (e.g., CDH10, TMC2, SIRPA, CPXM1) or reproduction traits (e.g., ADCY1, LEPR, GHR, LPAR2) of the mixed-age ewes.