Abstract
We investigated differences between effects of natural- and bucket-suckling methods on basal serum oxytocin (OT) and cortisol concentrations, and the effect of OT concentration on affiliative and investigative behavior of calves to a novel object. Ten Japanese Black calves, balanced with birth order, were allocated evenly to natural-suckling (NS) and bucket suckling (BS) groups. Blood samples were collected at the ages of 1 and 2 months (1 week after weaning) calves, and serum OT and cortisol concentrations were measured using enzyme-linked immunosorbent assay and enzymeimmunoassay tests, respectively. Each calf at the age of 2 months (2 weeks after weaning) was released into an open-field with a calf decoy, and its investigative and affiliative behaviors were recorded for 20 minutes. In 1-month-old calves, the basal serum OT concentration (25.5±4.9 [mean±standard deviation, pg/mL]) of NS was significantly higher than that of BS (16.9±6.7) (p<0.05), whereas the basal cortisol concentration (5.8±2.5 [mean±standard deviation, ng/mL]) of NS was significantly lower than that in BS (10.0±2.8) (p<0.05). Additionally, a negative correlation was noted between serum OT and cortisol concentrations in 1-month-old calves (p = 0.06). Further, the higher serum OT concentration the calves had at 1 month old, the more investigative the calves were at 2 months old but not affiliative in the open-field with a calf decoy. Thus, we concluded that the natural suckling method from a dam elevates the basal serum OT concentration in calves, and high serum OT concentrations induce investigative behavior and attenuate cortisol concentrations.
Highlights
In intensive cattle production systems, calves are separated from their dams immediately, or a few hours, after birth
It was reported that serum OT concentrations were instantaneously higher in calves during suckling that lasted only for 1 minute (Lupoli et al, 2001), the suckling effect on basal OT concentration was unclear
We revealed that the natural suckling system elevated the baseline of serum OT in 1-month-old calves
Summary
In intensive cattle production systems, calves are separated from their dams immediately, or a few hours, after birth. Hernández et al (2006) reported that artificially reared calves had a significantly higher level of serum cortisol concentration than in those suckling from their mothers. In Krohn’s (2001) review, he concluded that more than artificial rearing systems, natural suckling systems where calves are nursed by their dams and have social contact with other calves and cows are more beneficial to calf welfare such as a positive effect on the daily gain and vitality of the calf. The aim of the present study was to investigate the differences between the long-term effect of natural and bucket suckling systems on basal OT and cortisol concentrations in serum, and the effect of OT concentrations on affiliative and investigative behaviors to a novel object in calves
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