Voluntary selection of starter feed ingredients offered separately to nursing calves

摘要

The objective of this study was to evaluate whether calves exposed to different ingredients would consume solid feed in a similar manner than those offered the same ingredients mixed in a starter concentrate. Thirty-eight Holstein calves (initial live weight 41.0 kg and 7 days of age) were randomly assigned to a control (CTR) treatment consisting of a starter feed composed of ground corn (47.2%), soybean meal (20%), oats meal (11%), barley meal (10.1%), soybean hulls (8%), and full fat soybean (1.2%), or to a choice (CH) treatment consisting of 6 ingredients, that composed the starter of CTR calves, offered in separated buckets to each animal. Intake was recorded daily, and calves were weighed twice a week. Samples of fresh feed were taken every week and pooled for subsequent determination of nutrient composition. No differences were observed between treatments on total dry matter intake (DMI), solid feed intake, average daily gain (ADG), and gain to feed ratio. However, animals in the CH group consumed more crude protein (CP; P<0.01) and fat (P<0.01) than CTR calves. On the other hand, CH calves ingested less non-fibrous carbohydrates (NFC; P<0.01) than those in the CTR group. Despite these differences in nutrient intake, there were no differences in total metabolizable energy (ME) intake between CH and CTR animals. However, the CP to ME ratio was greater (P<0.01) in CH (81 g of CP/Mcal of ME) than in CTR calves (53 g of CP/Mcal of ME). Calves in CH group consumed less (P<0.01) corn and oats meal, and more (P<0.01) full fat soybean than CTR animals. Within the CH group of calves, soybean meal was most (P<0.01) preferred (32.8% of solid feed intake), whereas oats meal (3.5% of solid feed intake) was the least preferred (P<0.01). In terms of total amount consumed, no differences were observed among corn meal, full fat soybean, and barley meal. In conclusion, compared with calves fed a single starter feed, calves that were offered a choice of ingredients selected a diet with greater levels of CP and fat, and lower in NFC. Despite differences in nutrient consumption of the final diet consumed, no differences were observed in total DMI, solid feed intake, ADG, and gain to feed ratio. It is concluded that young calves are unable to select ingredients based on their nutrient requirements.