Dairy calves' preference for rearing substrate

Traditional substrate types for dairy calves, such as sawdust, are becoming difficult and/or expensive for farmers to obtain in New Zealand. Therefore, there is a need to evaluate alternative rearing substrates that provide an acceptable level of animal welfare. The preference of dairy calves for four different rearing substrates was evaluated (traditional and novel). At 1 wk of age, 24 calves were housed in groups of four, in pens which were evenly divided into four rearing substrates: sawdust, rubber, sand and stones. During the first 3 d calves were given free access to all four substrates. Calves were then restricted to each substrate type for 48 h. In order to rank preference, calves were subsequently exposed to two surfaces simultaneously in a pairwise manner for 48 h until all animals had experienced all six treatment combinations. Finally, calves were again given free access to all four substrates simultaneously for 48 h. Lying behaviour and location in the pen was recorded for the final 24 h during the free-choice and pairwise periods using video recorders and accelerometers. During the restriction period, lying behaviour was recorded for the final 24 h using accelerometers and play behaviour was recorded over 12 h using video recorders. Calves were blood sampled during the restriction period to measure cortisol, glucose and lactate concentrations, and white blood cell numbers. Preference was determined based on time spent lying on each substrate. During the initial free-choice period, calves spent more time lying on sawdust (76.6%, S.E.M.: 0.90%) than all other substrates (rubber: 1.6%, sand: 0.9% and stones: 0.5%, S.E.M.: 0.90%). When restricted to each substrate, calves spent more time running on sawdust (2.5 min/12 h, S.E.M.: 0.37 min), rubber (2.1 min/12 h, S.E.M.: 0.37 min) and sand (1.7 min/12 h, S.E.M.: 0.37 min) than on stones (0.9 min/12 h, S.E.M.: 0.37 min). In addition, calves spent more time lying on sawdust (17.8 h/24h, S.E.M.: 0.38 h) and rubber (17.2 h/24 h, S.E.M.: 0.38 h) in comparison to sand (16.0 h/24 h, S.E.M.: 0.38 h) and stones (16.3 h/24 h, S.E.M.: 0.38 h). The order of preference of the rearing surfaces was sawdust > rubber > sand > stones. At the end of the study, when given free access to all rearing substrates again, calves spent a higher proportion of time lying on sawdust than all other substrates. Blood chemistry and haematology measures of calves were similar when restricted to each substrate type. In conclusion, dairy calves showed a clear preference for sawdust over rubber, sand and stones. The calves' preference for sawdust may be associated with the physical and thermal properties in comparison to the alternative substrates. (C) 2015 Elsevier B.V. All rights reserved.