Two studies were performed to determine the effect of the selection of a diet from different feed ingredients offered on a free-choice basis and to determine the effect of the feeding method on the feeding behaviour and growth performance of calves in the pre-weaning period during different seasons. One-week-old Holstein Friesian calves were assigned to two experimental groups (choice feeding vs single feed). The diet was composed of, %: barley 42.56, maize 12, soyabean meal- SBM, 5.92, maize gluten meal 9.6, wheat bran 6.96, and 20 lucerne hay (ground, 1.5-2 cm). The feed ingredients used in the single feed were offered on a free-choice basis to the choice-fed calves. All calves were fed ad libitum, and water was freely available. The daily eating patterns were recorded with a real-time data-collection system, including six electronic scale feeders. The studies were conducted for 10 weeks, including an 8-week pre-weaning period and a 2-week post-weaning period. The results showed that the calves had a higher rectal temperature, respiration and pulse rate during the summer than during the winter (P<0.05). The meal number and total meal time were higher during the summer than during the winter. Feed intake, daily gain, and feed-to-gain ratio did not change according to season, however. Choice feeding increased the number of meals and the rate of feed intake but decreased meal duration and the intermeal interval compared with single feed (P<0.05). The choice-fed calves selected totally different (P<0.01) diets than the single-fed calves (SBM: 5.9 vs 64.7%, barley: 42.6 vs 8.4%, lucerne hay: 20 vs 5.8%). The calves did not change their diet preferences after weaning, compared with the pre-weaning period. Choice feeding increased nutrient intake due to increases in feed intake and diet preferences (P<0.05) but did not affect daily gain or the feed-to-gain ratio (P >0.05). The choice-fed calves had a higher meal number and eating rate and a lower meal duration and intermeal interval (P<0.01) than the single-fed calves. In conclusion, the results showed that calves had meal criteria of approximately 5 to 8 min, 11-18 meals per day, a 66- to 82-g meal size, and a 6- to 11-min meal duration. The results also showed that pre-weaning calves selected a diet containing a higher crude protein content (31-35%) than the standard starter crude protein content (18%).
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