Using Non-Invasive Monitoring Technologies to Capture Behavioural, Physiological and Health Responses of Dairy Calves to Different Nutritional Regimes during the First Ten Weeks of Life

SIMPLE SUMMARY: Recent research has debated the effects of milk and forage feeding regimes in the first weeks of life on the future performance of dairy calves. However, little is known about how feeding regime can affect behavioural and physiological responses, which have the potential to impact on calf health and well-being. Traditional methods of assessing calf health and welfare such as behavioural observations and blood sampling can be time consuming and impractical for producers and invasive for animals involved. Developments in technology have increased the availability of on-farm non-invasive devices which allow automatic and remote collection of behavioural and physiological data linked to animal health and welfare. This study aimed to use devices to measure lying behaviour, heart rate, heart rate variability and infrared temperature of calves offered high or low levels of milk replacer and different types of forage throughout the first ten weeks of life. Calves displayed changes in lying behaviour and heart rate variability as a result of changes in milk replacer feeding frequency. Additionally, infrared temperature changes were detected during periods of vaccination which corresponded with a rise in core body temperature. Results have highlighted that these sensors can provide important and useable data regarding overall calf well-being on commercial farms. ABSTRACT: This study aimed to examine the use of non-invasive monitoring technologies as a means of capturing behavioural, physiological and health responses of calves allocated to different nutritional regimes. Seventy-four Holstein Friesian calves were individually penned and allocated to receive either high (HML) or conventional (CML) milk replacer (MR) levels between 5–70 days of age. Additionally calves were allocated to one of four forage treatments: (i) chopped straw offered between 14–70 days of age (CS14), (ii) chopped straw offered between 56–70 days of age (CS56), (iii) grass silage offered between 56–70 days of age (GS56), and (iv) no forage in the pre-wean period (NF). A representative sample of calves from each treatment were fitted with activity sensors and heart rate monitors throughout the experimental period to examine lying behaviour and heart rate variability, respectively. Thermal images of the eye and rectal area of each calf were taken 5 days/week between 5–77 days of age. Faecal and respiratory scoring of each individual calf was carried out on a daily basis throughout the experimental period. Milk replacer feeding level had limited effects on measures of calf health, although HML calves tended to have an increased likelihood for receiving treatment for scour than CML calves. Daily lying time (min/d) was lower in HML calves following reduction in MR feeding frequency at 43 days of age and weaning at 71 days of age when compared with CML calves. Additionally, HML calves displayed a lower heart rate variability following weaning, this suggestive of increased stress load. There were limited effects of forage treatment, however, CS14 calves displayed a greater daily lying time following MR step-down at 68 days of age, this potentially indicating increased rumination. Results of the present study highlight the benefits of using remote monitoring technologies as a means of detecting behavioural and physiological changes as a result of nutritional management strategy in individually housed dairy calves.