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    Prevalence and Sequence Analysis of Equine Rhinitis Viruses among Horses in Poland.
    (MDPI (Basel, Switzerland), 2024-07-26) Stasiak K; Dunowska M; Rola J; Troyer R
    Equine rhinitis A (ERAV) and B (ERBV) viruses are respiratory pathogens with worldwide distribution. The current study aimed to determine the frequency of infection of ERAV and ERBV among horses and foals at Polish national studs, and to determine genetic variability within the viruses obtained. Virus-specific quantitative RT-PCR assays targeting a 5' untranslated region were used to screen nasal swabs collected from 621 horses at 16 national horse studs from throughout Poland, including 553 healthy horses and 68 horses with respiratory disease. A partial DNA polymerase gene was amplified and sequenced from the qRT-PCR-positive samples. The obtained sequences were analysed using phylogeny and genetic network analysis. None of the nasal swabs were positive for ERAV, whereas ERBV was found in 11/621 (1.78%) samples collected from 10 healthy horses and one foal affected by respiratory disease. Partial DNA polymerase gene sequence variability was correlated with individual horses and studs from which samples were collected when only Polish sequences were analysed, but there was no correlation between country of origin and ERBV sequence when Polish and international sequences were included in the network. The report presents the first detection of ERBV in Poland.
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    Quantification of relative stock units for horses to permit correct application within pasture-based production systems
    (CSIRO Publishing, 2023-05-29) Chin YY; Back PJ; Gee EK; Horne DJ; Rogers CW; Bryden W
    Context. Overseer® is the primary software tool used to estimate farm-level nutrient cycle and management for regulatory purposes in New Zealand. The model compares feed demand among different livestock by using ‘revised stock units’ (RSUs, the annual energy requirement of a mature ewe to raise a single lamb to weaning; 6000 MJ metabolisable energy). The RSUs for several common equine stock classes are not yet available, while those currently available within the model are based on the linear scaling of feed demand to liveweight, which does not consider allometric scaling of metabolism to liveweight or the differences in digestive physiology and nutrient metabolism between ruminants and monogastric hindgut fermenters (horses). Aim. To compare the current RSU values used in Overseer® for different equine stock classes, with the equineRSU values calculated using equine-specific models. Methods. Weighted average estimates of the bodyweight for the different equine livestock classes were calculated from the published literature. These weighted average estimates of bodyweight were used to estimate the energy requirements on the basis of data published by National Research Council. The resulting dry-matter intake and N intake from the equineRSU values and the current RSU values in use within Overseer® were modelled using published data on diet composition, crude protein content and the digestibility of the different feeds offered. Results. The current RSUs in Overseer were 2.5–6.8 units higher than the equineRSU values obtained from the equine-specific models. This overestimation in feed demand resulted in N-intake estimates at an animal level being 52–108% higher than values derived using the equine-specific estimates. Conclusion. The use of RSUs based on linear scaling of feed demand from ruminants on the basis of liveweight overestimates feed demand and N intake in horses. If horses are to be included within nutrient management models, feed demand must be based on published equine data for energy requirements to avoid over-inflation of N excretion. The equineRSUs calculated in this study reduce the risk of over-inflation of N intake and excretion, and subsequently the N leaching estimations. Implication. Failure to accurately model feed demand of horses within nutrient management software would unfairly compromise stocking density and horse management on large commercial breeding farms. The implication for these errors on economic impact and restricted livestock number is greatest for the Thoroughbred breeding industry due to the scale of the operations.
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    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 W
    From 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.
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    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 EZ
    Context: 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.
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    The pattern of breeding and management within the New Zealand Thoroughbred breeding industry 2005-2015. 1. the stallion population
    (CSIRO Publishing, 2024-01) Chin YY; Rogers CW; Gee EK; Stafford KJ; Cameron EZ; Bryden W
    Context: There has been a contraction within the New Zealand Thoroughbred racing industry and there are limited data demonstrating how this has affected, or been reflected, within the breeding industry that supplies horses for the racing industry. A reduction in the breeding industry, to a greater extent in the sector servicing domestic rather than export market has been speculated. Aim: To describe the demographics, breeding pattern, reproductive career and workload of New Zealand Thoroughbred stallions between 2005 and 2015. Methods: The breeding records of all Thoroughbred stallions covering >10 mares during 2005/2006-2015/2016 breeding seasons and the lifetime breeding records of all the mares covered by these stallions were extracted from the New Zealand Thoroughbred Racing website. The demographics, population numbers, career pattern, and 10-year trend in market share of stallions in different stud fee categories were examined using descriptive analysis. The stallion's reproductive workload was modelled deterministically. Results: The breeding population reduced over the 10 years examined (mares by 20%, sires by 32%). This industry consolidation was almost entirely due to the 50% reduction in the number of mares mated to the low-priced stallions, which generated horses for the domestic market. The relative proportion of mares sent to medium- and high-priced stallions (breed to sell and export sector) doubled. The commercial breeding career of low- and medium-priced stallions and shuttle stallions was short (4-5 years). The number of mares covered by a stallion increased with stud fee category. Stallions covered a greater number of mares in October and November than in September and December because of the restricted opportunity to cover foaled mares early in the season, caused by the long gestation length of mares and the need to cover mares before December. Conclusions: Findings in this study support that the contraction in the New Zealand Thoroughbred breeding industry was due to a reduction in the industry sector that focuses primarily on supplying horses for domestic racing. Commercial pressure and biological constraints heavily influenced the reproductive management of the breeding industry. The breeding management of stallions during the season is heavily influenced by stallion service fee category, which reflects his book size and the commercial appeal of the resultant progeny. Implications: The contraction within the domestic sector of the breeding industry was reflected in the concurrent contraction within New Zealands domestic racing population and fewer colts and geldings entering racing. Industry breeding trends demonstrate that economic viability and optimisation of revenue depend on the breeding industry focusing on the export rather than domestic market.