Use of an electronic rumination-monitoring system in pre-weaned calves.

The onset of rumination in calves starts approximately at 1-2 wks of age and increases up to 5 h/d at 4-6 wks. Nevertheless, the rumination behavior during the overall preweaning period and the daily rumination pattern is difficult to be investigated. The recent introduction of the Hi-Tag rumination-monitoring system (SCR Engineers Ltd., Netanya, Israel) in adult cows allows the automatic quantification of rumination time (RT) and opens new perspectives in the study of other physiological periods. This study was intended to evaluate the Hi-Tag system for monitoring rumination (RT and daily pattern) in pre-weaned calves and to assess the relationship of RT with inflammo-metabolic conditions. Nine Simmental calves were kept in individual pens from birth to 6 wk of age. At d 2 ± 1, calves were fitted with Hi-Tag loggers, which record the sounds of regurgitation and rumination. RT data were calculated in 2-h intervals. Calves were fed whole milk twice daily and also calf starter was provided. Blood samples were collected at d 0, 1, and then weekly. Data were analyzed using PROC MIXED and PROC CORR of SAS (SAS Institute Inc., Cary, NC). The average of daily RT was 91, 210, 313, 362, 373 and 377 min/d for wk 1, 2, 3, 4, 5 and 6, respectively. The daily RT observed at wk 6 represents the 63% of the mean daily RT value recorded in adult cows in mid lactation. Moreover, the daily rumination pattern observed in calves over weeks is similar to that reported in adult cows. At wk 6, the Hi-Tag loggers recorded values of RT at nighttime greater than those registered at daytime (61% vs 39%; p<.001) as already observed in adult cows. In all calves, RT was not influenced by milk suckling. Indeed, the RT in the 2-h interval recorded at milk feeding was markedly lower (especially in the morning) compared to RT in the 2-h interval before. Relevant correlations between daily RT and a number of plasma parameters (albumin: r¼0.50, p¼.001; paraoxonase: r¼0.59, p<.001; cholesterol: r¼0.36, p<.01; GGT: r¼-0.55, p<.001) were observed. These associations demonstrate that RT in pre-weaned calves is well related with markers of liver functionality. These results represent a first attempt to use an automatic system to obtain a reasonable quantification of RT in calves at the pre-weaning stage. Despite this technology remains not validated for calves, the outcome of the present study seems promising to identify animals with poor post-birth adaptation or poor health status.