The study of interaction effects of feed bunk space and forage particle size on feeding behaviors in female Holstein calves

The aim of this study was to investigate the interaction effects between feed bunk spaces and forage particle size on feeding behaviors of female Holstein calves. This study was done on 40 Holstein heifers aged 8-12 months and average mean weight 295.62±32.86 kg in a factorial change over design 2×2 (four periods with a length of each period of 25 days). The sole differences between treatments was related to forage (alfalfa hay and wheat straw length) as these forage were cut off by cutter with 3 cm pore size sieve (fine diet) and 6 cm pore size sieve (coarse diet) before adding to feeder mixer wagon. Treatments in this experiment included: 1) treatment with 24 cm of feed bunk space and forage with fine particle size (24/fin), 2) treatment with 24 cm of feed bunk space and forage with coarse particle size (24/coarse), 3) treatment with 48 cm of feed bunk space and forage with fine particle size (48/fin), 4) treatment with 48 cm of feed bunk space and forage with coarse particle size (48/coarse). The results showed that the feed intake time was higher during 24 hours for treatments with free bunk space (48 cm) compared to treatments with a limited bunk space (24 cm) (p<0.05). The results showed that in case of access of calves to free bunk space, the feed particle size did not affect the intensity of competition, while in the case of a limited bunk space, the intensity of competition for coarse particle size was greater than that of fine particle size (p<0.05).