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Summary: Background: Recent studies have described techniques to acquire ultrasound measurements of the cross‐sectional area of the multifidus muscle to investigate back pain in horses and monitor the response to rehabilitation. These techniques have been extrapolated from human research but have not been clinically validated in the horse. Objective: The objective of the study was to investigate whether measuring the cross‐sectional area of the multifidus muscle in horses using ultrasound is a repeatable technique. Study design: Cross‐sectional. Methods: Ultrasound images of the articular process view and interspinous view of the multifidus muscle were acquired at T15, T18, L2 and L5 on the left and right sides. Three images were acquired at each location and each image was measured three times to give an average cross‐sectional area. Study 1 investigated the repeatability of acquiring images in a single session, and then on two separate days. Study 2 compared measurements of images acquired with a console (Philips EpiQ) and a portable (MyLab™Alpha) ultrasound machine. Study 3 investigated the repeatability of measuring the cross‐sectional area using external software, OsiriX. Intraclass correlation coefficients (ICC) were calculated for each study. Results: Repeatability varied from good to excellent for images taken in a single session. The repeatability for measuring the images using external software was good to excellent. There was poor‐to‐moderate repeatability for images taken on two different days and poor‐to‐good repeatability when using the two different machines. Main limitations: Population size, study population limited to a single breed, only one operator. Conclusions: The measurement of the multifidus muscle in horses has poor repeatability and may have limited application. [ABSTRACT FROM AUTHOR]

Context: Annual liveweight production of a cow is the sum of the weight of its calf at weaning and its own annual liveweight change. Along with value per kg, annual liveweight production constitutes the business income contributed by the animal; however, it is not well described for north Australian beef herds. Aims: This study aimed to quantify cow liveweight production and to measure impacts of reproduction and other risk factors. Methods: Liveweight production data from 2122 Brahman and tropically adapted composite cows aged 2.5–8.5 years and grazing the four primary country types in northern Australia were analysed as a function of current and previous mating outcomes, mating age, breed, hip height, and body condition or liveweight. Key results: Cow liveweight production was highly variable (coefficient of variation 40%) among and within years. Liveweight production of cows averaged 154 kg/year from their first mating, 168 kg/year from their second, and 190 kg/year from subsequent matings; however, production efficiency remained constant, with a liveweight production ratio of 0.31–0.32 kg produced annually per kg of grazing animal. Within environment, average weaner production (kg/cow) approximated the estimated average annual weight gain of yearling cattle. Weight of calves weaned contributed ~87% of annual liveweight production. Liveweight production averaged 103–143 kg higher for cows that weaned a calf than those that lost a calf, with the effect greater in older cows (P < 0.001). Liveweight production averaged 39–43 kg higher for non-pregnant cows than those that lost a calf (P < 0.001). These effects were attenuated by ~20% over a lifetime. Cows weaning a calf from a previous mating had liveweight production 57–85 kg higher (P < 0.001) than those not weaning a calf, having begun the year in poorer condition because of lactation. Calf weaning weight was 25 kg higher in mature cows than in first- and second-lactation cows. Liveweight production advantages of tropical composites over Brahmans appeared primarily associated with consistently higher calf weaning weights, and higher cow growth during their first reproductive year. Conclusions: This research successfully demonstrated the concept of liveweight production in breeding beef cows, showing it to be primarily governed by available nutrition and mating outcome. Implications: These findings provide a previously unavailable reference point for beef-systems management in northern Australia; for example, liveweight production could be used to determine the potential achievable increases in cow performance for a specific nutritional environment. Annual liveweight production of cows in north Australian beef-breeding businesses, which along with value per kg constitutes business income, has not been well defined. Liveweight production over the life of 2122 tropically adapted cows grazing four primary country types was highly variable, being limited by available nutrition, and increased to maturity, whereas efficiency remained constant. Relative to cows weaning calves, the loss of a conceptus or weaner had a larger negative impact on liveweight production than failure to conceive. [ABSTRACT FROM AUTHOR]

We used epidemiologic evaluation, molecular epidemiology, and a case-control study to identify possible risk factors for the spread of highly pathogenic avian influenza A virus (subtype H5N1) in chicken farms [...]

Intra‐articular (IA) hyaluronic acid (HA) is commonly used to treat equine arthritis. Inflammatory response or "joint flare" is a recognized potential side effect. However, the incidence and severity of inflammation following IA HA injection in horses is not well documented. This study compared the effects of two IA HA formulations of different molecular weight (MW) and a saline control on clinical signs and synovial fluid markers of inflammation in normal equine joints. Eight adult horses each had three healthy fetlock joints randomly assigned to treatment with either 1.4 mega Dalton HA, 0.8 mega Dalton HA or saline control once weekly for three weeks. Clinical evaluation and synovial fluid analysis were performed by blinded assessors. Outcomes of interest were lameness score, joint effusion score and synovial fluid white cell count and differential, total protein, viscosity and serum amyloid A. Joints injected with HA developed significant mild‐to‐moderate inflammatory responses often associated with lameness and joint effusion compared with saline control joints. The higher MW HA formulation elicited a significantly greater inflammatory response than the lower MW HA after the first injection. In HA injected joints, viscosity remained poor for the entire study. Both IA HA formulations in this study induced an inflammatory response in healthy equine joints. This may have implications for the use of HA in equine joints. The findings in this study are limited to the two HA formulations used. Further investigation of different HA formulations and the use of HA in normal and arthritic equine joints is warranted. [ABSTRACT FROM AUTHOR]