Abstract
Estimating the energy expenditure of farm animals at pasture is important for efficient animal management. In recent years, an alternative technique for estimating energy expenditure by measuring body acceleration has been widely performed in wildlife and human studies, but the availability of the technique in farm animals has not yet been examined. In the present study, we tested the potential use of an acceleration index, overall dynamic body acceleration (ODBA), as a new proxy for estimating the energy expenditure of grazing farm animals (cattle, goats and sheep) at pasture with the simultaneous evaluation of a conventional proxy, heart rate. Body accelerations in three axes and heart rate for cows (n = 8, two breeds), goats (n = 6) and sheep (n = 5) were recorded, and the effect of ODBA calculated from the body accelerations on heart rate was analyzed. In addition, the effects of the two other activity indices, the number of steps and vectorial dynamic body acceleration (VeDBA), on heart rate were also investigated. The results of the comparison among three activity indices indicated that ODBA was the best predictor for heart rate. Although the relationship between ODBA and heart rate was different between the groups of species and breeds and between individuals (P<0.01), the difference could be explained by different body weights; a common equation could be established by correcting the body weights (M: kg): heart rate (beats/min) = 147.263∙M -0.141 + 889.640∙M -0.179∙ODBA (g). Combining this equation with the previously reported energy expenditure per heartbeat, we estimated the energy expenditure of the tested animals, and the results indicated that ODBA is a good proxy for estimating the energy expenditure of grazing farm animals across species and breeds. The utility and simplicity of the procedure with acceleration loggers could make the accelerometry technique a worthwhile option in field research and commercial farm use.
Highlights
The efficient utilization of available resources has been of great importance in animal production systems all over the world
Where HRijk is heart rate, μ is the overall mean, Gi is the random effect of the group of species and breeds (Japanese Black cattle: JBL, Japanese Brown cattle: JBR, Saanen goat: SA, and Corriedale sheep: CO), Aj is the random effect of individual animals nested within the group, β1(ODBA)ijk is the covariate of overall dynamic body acceleration (ODBA) (g), βi(ODBA)ijk is the interaction between ODBA and the group of species and breeds (β1 is the overall regression coefficient and βi is the effect of the ith group to the regression coefficient) and eijk is the residual error
Where HRij is heart rate, μ is the overall mean, Ai is the random effect of the individual, β1(ODBA)ij is the covariate of ODBA (g), βi(ODBA)ij is the interaction between ODBA and the individual (β1 is the overall regression coefficient and βi is the effect of the ith group to the regression coefficient), and eij is the residual error
Summary
The efficient utilization of available resources has been of great importance in animal production systems all over the world. Grassland-ruminant ecosystems are efficient and sustainable methods for converting non-edible resources (grass) into high-protein human foods (i.e., milk and meat). In these ecosystems, grazing animals consume plants growing on grassland, and plant growth is increased by the feces and urine excreted by the animals and deposited and recycled in the field [2]. It is necessary to obtain information about the balance between the grassland production and the energy requirements of grazing animals to realize efficient animal management in grazing systems In this context, the evaluation of the energy expenditures of farm animals is one of the most important issues in efficient grazing management
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