Biochemistry and hematology reference intervals for neonatal dairy calves aged 5-12 days.

BACKGROUND: Comprehensive hematology and biochemistry RIs are currently lacking in the literature for young dairy calves based on sample sizes more than 120. Young dairy calves are at a relatively high risk of poor health and welfare outcomes. They have a high risk of morbidity and mortality in the first 2 weeks of life, and many are transported and fasted during this time. For example, non-replacement calves in Australia and New Zealand are usually 5-12 days old when transported to abattoirs, meaning that calves of this age group are potentially at risk of both health and welfare compromise. Given these factors, sound, comprehensive, age-specific biochemical and hematologic RIs are needed for both veterinary clinical practice and to inform research on calf health and welfare. OBJECTIVES: The aim of this study was to generate age-specific hematology and biochemistry RIs for dairy calves aged 5-12 days. METHODS: We collected blood samples from 141 fasted, healthy dairy calves on 10 Australian farms. Reference Value Advisor software was used to calculate nonparametric RIs for multiple biochemistry and hematology variables. RESULTS: RIs for a panel of hematology and biochemistry variables in dairy calves aged 5-12 days old were derived. CONCLUSIONS: These RIs will be useful for clinical veterinary practice, as well as for research on dairy calf health and welfare.

Spatial Cognition and Range Use in Free-Range Laying Hens.

Radio-frequency identification tracking shows individual free-range laying hens vary in range use, with some never going outdoors. The range is typically more environmentally complex, requiring navigation to return to the indoor resources. Outdoor-preferring hens may have improved spatial abilities compared to indoor-preferring hens. Experiment 1 tested 32 adult ISA Brown hens in a T-maze learning task that showed exclusively-indoor birds were slowest to reach the learning success criterion (p < 0.05). Experiment 2 tested 117 pullets from enriched or non-enriched early rearing treatments (1 pen replicate per treatment) in the same maze at 15-16 or 17-18 weeks. Enriched birds reached learning success criterion faster at 15-16 weeks (p < 0.05) but not at 17-18 weeks (p > 0.05), the age that coincided with the onset of lay. Enriched birds that were faster to learn the maze task showed more range visits in the first 4 weeks of range access. Enriched and non-enriched birds showed no differences in telencephalon or hippocampal volume (p > 0.05). Fear may reduce spatial abilities but further testing with more pen replicates per early rearing treatments would improve our understanding of the relationship between spatial cognitive abilities and range use.