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Outbreaks of humeral fractures in dairy cows have been reported in New Zealand for several years. Gross, histologic, and histomorphometric findings in the humerus from primiparous cows with spontaneous humeral fracture were compared to age-matched control cows. Affected cows had a complete nonarticular spiral fracture of the humerus. Histologically affected humeri had a thicker growth plate with abnormal architecture, thinner cortex with increased abnormal resorption, increased resorption in the distal humerus, decreased trabecular density, abnormal trabecular architecture, presence of growth arrest lines and woven bone formation. Histomorphometry showed reduction in bone volume, trabecular perimeter, and trabecular width. Cows grazed on fodder beet had thicker growth plates with an abnormal appearance compared with cows grazed on pasture, and cows with low/marginal liver copper concentration had more resorption cavities in the distal humerus and thinner cortical bone compared with cows with adequate liver copper concentration. Decreased trabecular density (OR = 249.5), abnormal cortical resorption (OR = 54.2), presence of woven bone formation in the proximal metaphysis (OR = 37.2), and the number of resorption cavities in the distal humerus were significantly associated with a high probability of fracture. Ribs had enlargement of the costochondral junction with fractures in different stages of healing. Histology of the ribs revealed abnormal growth plate appearance, presence of fracture lines, callus tissue, fibrosis, and microfractures. Cows with humeral fracture have osteoporosis due to decreased bone formation and increased bone resorption, likely associated with inadequate feed quality and perhaps copper deficiency leading to a reduction in bone strength and fracture. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare conformation, age at puberty and subsequent milk production of Holstein–Friesian–Jersey crossbred heifers grown in a linear trajectory (Target; n = 55) between 6- and 15-month target liveweights (LWT), with heifers grown in a seasonal manner (Seasonal; n = 55) of slow over first winter and fast over spring. Heifers that grew to Target attained puberty 38 days earlier than heifers that grew in a seasonal manner; however, no difference between treatments in the date of first calving occurred. Heifers in the seasonal treatment were 1 cm (P =.032) taller than those in the target treatment, but similar in girth and length. There was no effect of treatment on first lactation milk production. These results suggest that provided heifers reached their pre-mating target LWT, the growth trajectory between target LWT at 6 and 15 months of age did not negatively impact frame size or first lactation milk production. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare breed proportions, genetic merit, milk production and survival of carryover and non-carryover dairy cows in New Zealand. Calving interval was used as a tool to identify cows that had an extended non-lactating period and then returned to a milking herd. A greater proportion of Holstein-Friesian was observed in the breed composition of the carryover cows. Estimated breeding values (EBVs) for milk traits were greater, but the EBVs for fertility were lower for carryover cows, than those for non-carryover cows. Carryover cow genetic merit values were greater than those for non-carryover cows in the year prior to their carryover period. Carryover cow milk production was significantly greater than that of non-carryover cows. The average survival days and probability of survival for second-lactation carryover cows was lower than that for first-lactation and lactation-matched non-carryover cows. These results are important for culling decisions made by pastoral dairy farmers. [ABSTRACT FROM AUTHOR]

Liveweight targets in the New Zealand dairy industry aim to increase subsequent productionof heifers. The aim of this experiment was to determine the effect of the percentage of individual liveweight target achieved at 6, 9, 12 and 15 months of age, on heifers' reproductive performance and on milk production in first lactation, using retrospective analysis of a cohort of replacement heifers within a New Zealand dairy herd Heifers that reached liveweight targets at 12 and 15 months of age had longer lactations and produced more milksolids than heifers that were behind target. The increase in production from increasing percentage of liveweight target was greater for heifers that were further below their target live weight. This experiment supported the need to have heifers close to liveweight target at 12 and 15 months, but there were only limited advantages of greater percentage of liveweight target achieved at 6 and 9 months of age. [ABSTRACT FROM AUTHOR]

Fodder beet and kale are commonly used winter crops in New Zealand dairy and dairy support farm systems. Fodder beet (FB) is known to have lower crude protein, phosphorus and calcium content compared to kale. The intrauterine effects of feeding FB during late pregnancy on bone growth and development in calves requires attention. This study aimed to examine the intrauterine effects of a maternal diet of either kale or FB on measures of calf stature and bone morphology at birth. In winters 2019 and 2020, two herds of pregnant Friesian × Jersey cows were fed either kale (2019, 2020 n = 20) or FB (2019, 2020 n = 20) supplemented with pasture baleage. Calves born from these mobs were euthanised within ten days of birth and a forelimb and section of rib including the costochondral junction were harvested for peripheral quantitative computed tomography and histological analysis. Calves from the FB treatment had reduced bone density and strength compared to calves from the kale treatment (p < .05). The effect of a nutritional deficit on bone morphology at birth emphasises the importance of sufficient nutrition in pre-calving diets. Future research is required to examine the long-term impact of dam undernutrition on calf growth and production. [ABSTRACT FROM AUTHOR]

The objective of this study was to model the growth of dairy heifers to estimate the effects of breed and heterosis on live weight (LWT) and growth from three to 22 months of age. Data comprised of 1,653,214 LWT records obtained from 189,936 dairy heifers in 1547 herds. At all ages Holstein-Friesian (F) heifers were heavier than Holstein-Friesian-Jersey crossbred (F × J) which were heavier than Jersey (J) heifers. Heterosis effects for LWT were greatest at nine months of age (3.6%) and least at 22 months of age (2.0%). The growth pattern differed, as evidenced by the regression coefficients of the Legendre polynomial. Growth was non-linear and heterosis effects were different throughout the growth period. Friesian, J and F × J heifers exhibited different growth patterns. These differences in growth pattern should be considered when formulating target LWTs and growth rates for a pasture-based system. [ABSTRACT FROM AUTHOR]

To adjust for potential overestimations in the nitrogen excretion by horses within Overseer®, a revised stock unit system has been proposed (equineRSU). These equineRSU were generated and validated using a medium-sized equine farm as a model farm. The aim of this study was to test the application of the equineRSU and seasonal stock number adjustment on a more complex farming model. Livestock numbers and management data were captured prospectively for the base property (128.8 ha) of a large multi-property commercial breeding stud (3 support properties, 556 ha total area) between June 2022 and May 2023. The monthly on-farm metabolisable energy (ME) requirement and pasture demand were deterministically modelled with both a customised feed budget using livestock class and weight or using the equineRSU and monthly adjusted stock numbers. There were multiple complex movements of horses on and off the property in the different stock classes across the year, with stock management reflecting seasonal periods of high stocking density. There was good agreement (6% variance) between actual ME demand (complex feed budget) and estimated feed demand (simplistic equineRSU model) of 4,387,187 MJ vs 4,102,770 MJ. This suggests that the equineRSU could be used on complex equine farm systems within Overseer®. [ABSTRACT FROM AUTHOR]