Abstract
This research is used to evaluate the influence of phosphorus depletion in the feed of the dam during the last five weeks of pregnancy. The research evaluated the influence of this depletion on the cortisol level of the dam and its calf. Also, the behaviour of the calves was evaluated.
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A group of 14 dams and their calves were used. The calves were born during the research period. There were 15 calves born in total, because one dam had twins. Seven of these dams were allocated to the treatment group and the seven others to the control group. Dams in the treatment group received a phosphorus reduction in their feed five weeks prior to parturition while the control group received recommended levels as proposed by the NATIONAL Research Council. The only difference between the feed of the treatment group and control group was that there was 35% less phosphorus in the feed of the treatment group. A few days before the feed change a sample patch of hair was shaven from the flank of all the dams. These hairs were analyzed for their cortisol content value. There was no significant difference found between the treatment group (n=7) and the control group (n=7). At 12-13 days after parturition hairs were again shaven from the same sample patches. These hairs were also analyzed and they were found to contain no significant difference in cortisol level between the two groups. On the same day that the dams were shaved for the second time the calves were shaved for the first time, i.e. 12-13 days postpartum. These calf hairs were also analyzed and there was no significant difference found between the two groups of calves. The calves were shaved again 102-103 days postpartum. In these hairs there was no significant difference found. There was also no correlation found between the cortisol levels of the dams in comparison to their calves. At 93-109 days postpartum the behaviour of the calves was observed for three times, for one hour each time, in groups. During this observation period, the behaviour was noted every 50 seconds of each calf. The different observed behaviours were allocated to two behavioural groups; active and not active. There was no significant difference found between the two groups with respect to their behaviour. According this research it can be concluded that the depletion of phosphorus (a reduction by 35% from the recommended levels) during the five last weeks of pregnancy, has no influence on the cortisol level of the dam or her calf. Also, the depletion of phosphorus has no influence on the behaviour of the calf in the research period.
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