子牛をペアでハッチに入れた方が増体も良いし、異物を吸う行動が大幅に減ったという報告が出てきている。この行動はよく哺乳量が足りないからだ、と説明されてきたように思うが、ストレスにより起こる行動なのかなぁ。原著を読んでみよう。
Pempek JA, Eastridge ML, Swartzwelder SS, Daniels KM, Yohe TT
J. Dairy Sci. 2015 Nov;
PMID: 26585485
Abstract
Social pressure is increasing to adopt alternative housing and management practices that allow farm animals more opportunity to exercise and demonstrate social behavior. The present study investigated the effect of pair housing on the behavior and growth performance of Jersey heifer calves. Forty female Jersey calves were allocated to individual or pair housing at birth and monitored for 9 wk. Calves were provided with a single hutch, and those allocated to the pair housing treatment were provided a pen enclosure twice the size of individually housed calves and only one hutch was provided per pair. All calves were fed milk replacer via bucket twice per day (1.89 L/feeding first 7 d; 2.27 L/feeding until weaned) and had ad libitum access to grain and water. Gradual weaning commenced on d 49 by reducing the calves’ milk allowance to one feeding per day, and weaning occurred on d 56. Grain consumption was monitored daily and calves were weighed weekly. Direct behavioral observations were conducted twice per week. Calves housed in pairs tended to have greater average daily gain compared with calves housed individually (0.63 vs. 0.59 ± 0.02 kg/d, respectively). Pair housing also increased final body weight compared with individual housing (64.9 vs. 61.7 ± 0.59 kg, respectively). During observation periods, calves housed individually spent more time engaging in nonnutritive sucking than calves housed in pairs (21.5 vs. 8.15 ± 0.03% of total observations). Calves housed in pairs were observed cross sucking 13.5% of the time during observational periods. Although housing Jersey calves in pairs may increase measures of growth performance, future research should aim to reduce cross-sucking behavior within the Jersey breed through alternative feeding systems or environmental enrichment.