Reaction of foster cows to prevention of suckling from and separation from four calves simultaneously or in two steps

¹ Department of Animal Environment and Health, Swedish University of Agricultural Science, Skara, Sweden
² Department of Biometry and Engineering, Swedish University of Agricultural Sciences, Uppsala, Sweden
³ Department of Animal Health, Welfare and Nutrition, Research Centre Foulum, Tjele, Denmark
⁴ Swedish Animal Welfare Agency, Skara, Sweden

^* To whom correspondence should be addressed. E-mail: jenny.loberg{at}hmh.slu.se.

	Abstract

The aim of this study was to investigate if a two-step method of preventing suckling and cow-calf separation reduces the stress reaction in foster cows as compared with a simultaneous separation method. Seven Swedish Holstein and 5 Swedish Red dairy cows were used as foster cows, each having a group of 4 calves. The foster cow-calf group was formed when calves were 1 wk-old and the calves were prevented from suckling at 10 wk-of-age. In 6 of the groups, calves were prevented from suckling by simultaneous separation from the cow (control). In the other 6 groups, calves were fitted with a nose-flap, which prevented them from suckling, while kept together with the cow for another 2 wk before they were separated (two-step). The behavior of the foster cows was observed at 4 different observation periods, 0 to 2, 8.5 to 9.5, 24 to 26, and 72 to 74 h after calves were prevented from suckling (two-step), after separation (two-step), and after calves were prevented from suckling by simultaneous separation (control). For both treatments, saliva cortisol was sampled once daily for 5 d at wk 10. This was repeated at wk 12 for the two-step treatment. Heart rate was measured with the behavioral observations. The relationship between separation strategy and cow behavior, cortisol, and heart rate was examined using a generalized log-linear model using PROC GENMOD (SAS). Because heart rates were measured as potentially auto-correlated time series, they were AR-filtered before statistical analysis. Control foster cows vocalized more (P < 0.001) and walked more (P = 0.005) than the two-step foster cows both after prevention of suckling and after separation from the calves. When control cows were separated from their calves, they more frequently (P < 0.001) held their head out of the pen than was the case with two-step cows when separated 2 wk after prevention of suckling. The variation in heart rate was larger in the control group compared with two-step cows 0 to 2 h after separation/prevention of suckling (P = 0.002). No effect of treatment on cortisol concentration was found. Our conclusion is that separating the 2 events "prevention of suckling" and "separation" reduces the stress experienced by foster cow at weaning.

Key Words: behavior, cortisol, foster cows, heart rate, stress, weaning