Do calves in tropical areas behave differently when artificially milk-fed than when nursed restrictively? :

Sammanfattning: In tropical areas Zebu cattle (Bos indicus) and crossbreeds between Zebu and humpless cattle (Bos taurus) are most common due to their better capability to produce milk in hot and humid climate. It is generally believed, that these cows need to have their calves next to them during milking in order to stimulate milk let-down. After milking, the calf is usually allowed to suck the residual milk from its mother. The dairy breeds used in Europe and North America let the milk down during milking without having the calf by their side. The European and North American calves are often artificially milk-fed with whole milk or milk substitute from buckets or bottles. The artificially milk-fed calves do not have the possibility to perform non-nutritive sucking on a teat. There is a risk that internal factors (underlying motivation) stimulate the calves to perform some substitute (vacuum) behaviour. The aim of this study was to find out if artificially milk-fed crossbred calves performed more abnormal behaviours, had a lower weight gain or reduced health, compared to restrictively suckling calves. The study was performed on the research institute “El Clarin” outside Martinez de la Torre in the state of Veracruz, which is located in the tropical region of eastern Mexico. The animals used were calves of mixed breed of 25% Holstein, 25% Zebu and 50% Simmental. The dairy cows were F1-crossings, 50% Holstein and 50% Zebu. At five days of age the calves were randomly assigned to one of two treatments: R) restrictively suckling calves (n = 11) or A) artificially milk-fed calves (n = 11). The behavioural observations of the calves started at the age of seven days and were repeated once a week (day 7, 14, 21, 28, 35, 42, 49, 56), to an age of two months. The behavioural observations were performed twice a day. In the morning (7-13 h), the observations were performed during the milking and suckling/drinking milk, 30 minutes for each calf. In the afternoon (17-19 h), the observations were performed on the pasture during one hour for each calf. All behaviours were recorded with 0-1 sampling at one minute intervals. Statistical analyses were made with Wilcoxon Rank Sum test and Chi²-test (SAS 8.2). The results from the observations during milking revealed that the A-calves showed significantly more of the behaviours “sniff and lick interior” (p<0.01) and “cross-suck” (p<0.05), and a tendency for more “lick other calves” (p<0.1) than the R-calves. The relationship between the R-cows and their calves during milking included more “cow sniffing calf” (p< 0.05) and “cow licking calf” (p<0.1) compared to the A-cows. After milking the A-calves showed significantly more of the behaviours “sniff and lick interior” (p<0.01), “calf sniff other calf” (p<0.01), “calf lick other calf” (p<0.05) and “cross-suck” (p<0.0001) than the R-calves. The R-calves were sniffed, licked and rubbed by their dams, but also sniffed, licked and rubbed their dams during the restrictively suckling. During the afternoon observations the A-calves showed significantly more of the behaviours “eat concentrate” (p<0.05) and “cross-sucking” (p<0.01) than the R-calves. The R-calves showed significantly more “walk” (p<0.01) and “sniff ground” (p<0.05), and a tendency of more “play” (p<0.01) than the A-calves. There were no significant differences between the treatments regarding the following behaviours; “lie”, “stand”, “graze”, “ruminate”, “drink water”, “lick self”, “lick other calves” and “social interactions”. The R-calves tended to have a higher weight gain than the A-calves (p<0.1), but the lowest weight gain was found in those A-calves that got milk substitute during more than half of the observation time. The A-calves were more often diagnosed with diarrhoea than the R-calves (p<0.05). The coat condition of the A-calves was more often recorded to have un-licked and not so shiny coat compared to the R-calves. The conclusion is that the artificially milk fed calves had more abnormal behaviours and reduced health, compared to the restrictively suckling calves. Therefore, I suggest that the welfare of the restrictively suckling calves was better.