Calf performance in a cow-driven cow-calf contact system: Effect of 2 methods to gradually reduce cows' access to...

Knowledge is lacking on separation strategies that can best prepare calves to final separation from the dam in cow-calf contact (CCC) systems. This controlled trial compared the effects of 2 different methods to gradually reduce cows' access to their calf termed "debonding" on calf growth in a cow-driven CCC system. Initially, cows (Norwegian Red breed) had 24 h/d computer-controlled access to their calves. In the long debonding (LDB) treatment (n = 16), a gradual reduction of cows' access to their calves was initiated 28 d after calving over a total duration of 28 d; first to 12 h/d (14 d), and then to 6 h/d (14 d). In the short debonding (SDB) treatment (n = 14), reduction was initiated 45 d after calving over a total duration of 10 d; first to 12 h/d (5 d), and then to 6 h/d (5 d). From 6 h/d, access was finally reduced to 0 h/d for 4 d for both treatments, resulting in a study period of 60 d in total. Calves had ad libitum access to concentrate, hay and water throughout the study. Independent of treatment, ad libitum access to whole milk from an automatic feeder was granted once cow access was reduced. Cows and calves had the possibility for fence line contact at all times. The primary outcome variable calf weight gain was registered biweekly. Calf ADG was analyzed with a linear mixed model. The ADG was similar across treatments during 24 h/d access (1.04 ± 0.07 kg). Debonding treatment affected calf growth differently with each gradual reduction in cow access (12 h/d, 6 h/d and 0 h/d); however, no main effect of treatment was detected. The SDB calves had a pattern of increased ADG with the first reduction in access (+0.39 ± 0.18kg), followed by significant growth checks as access was reduced further to 6 h/d and 0 h/d (-0.41 ± 0.20 kg and -1.15 ± 0.31 kg, respectively). The LDB calves only showed significant weight checks at the final reduction in access (0 h/d access), yet at a lower degree (-0.46 ± 0.21 kg) than SDB calves. As expected, ADG was negatively associated with health events but positively associated with intake of concentrate and supplemental milk. Collectively, the results from the present study might point toward a long adaptation to separation which is initiated at a younger age being more favorable for calf performance.