Effect of stocking density at the feeding rack and social rank on the behaviour of Icelandic heifers
Overstocking of Icelandic dairy heifers with regard to the animal feeding place ratio has become more common during the last years. Rather little is known about the behavioural consequences for heifers of this management procedure, which imposes a competitive situation on the animals. The aim of this study was to investigate the effects of stocking density at the feeding rack on both the social and maintenance behaviour of heifers. Furthermore, it was the aim to study possible interactions of stocking density with the social status of the animals. Two groups of nine Icelandic dairy heifers each were used in a cross over design applying competition levels of four (competitive situation) and nine (control situation) feeding places for nine heifers respectively. For the evaluation of the time budgets, i.e. lying, feeding and standing, two video recording periods of three days each were performed. Agonistic behaviours for determination of the social order and feed intake related behaviours such as manipulating or smelling in the feed were observed directly. Regarding agonistic behaviours at the feeding rack, displacements occurred on average five times more often with increased competition at the feed rack than during the control situation. With increased competition heifers of both ranks tended to spend less time eating (3.8 hours during competition vs. 4.2 hours during control, p = 0.061). When comparing high and low ranking heifers, it turned out that low ranking heifers spent significantly more time lying, both during control and competition (13.2 hours low ranking heifers vs. 10.8 hours high ranking heifers during control and 13.5 hours low ranking heifers vs. 11.0 hours high ranking heifers during competition, p = 0.002). There were no significant differences in the feed intake related behaviour neither between high and low ranking heifers nor between control and competitive situation In conclusion, the time budgets of the heifers or their behaviour in the course of the day did not change substantially, but agonistic interactions increased markedly during the competition. Because of the increased agonistic interactions it would not be advisable to have a restricted feeding area and expose animals by that to competition during feeding.
Ísland, Kvígur, Atferli, Samkeppni, Virðingarröð
Networked Digital Library of Theses and Dissertations