Effect of forage feeding time and physical form of starter feed on dry matter intake, average daily gain, and body structural growth of Holstein dairy calves

Background and objective: The importance of calf breeding in the economic sustainability of dairy herds is clear. Apart from the milk feeding program, the physical form of the starter feed as well as the forage intake are effective factors in the growth of dairy calves. So far, no research has investigated the interaction effect of the physical form of the starter feed and the feeding time of forage on the performance of Holstein dairy calves. The purpose of this experiment is to investigate the effect of forage feeding time and the physical form of the starter feed on feed intake, average daily gain and body structural growth of Holstein dairy calves.
Materials and methods: This experiment was conducted in the form of a completely randomized design and with a 2 x 2 factorial method and for 85 days. For this purpose, 40 calves were used and the calves were divided between 4 experimental treatments (each treatment included 10 calves). Experimental diets include 1- ground starter feed with forage (10% alfalfa hay) from the first day of the experiment 2- ground starter feed with forage from the 21st day of the experiment 3- pelleted starter feed with forage from the first day of the experiment 4- pelleted starter feed with forage from the 21st day of the experiment. Statistical analyzes were performed using the MIXED method by SAS software with the effect of time as repeated measurements.
Results: According to the results of this research, the interaction effect of forage feeding time × physical form of the starter feed was significant for starter feed intake, dry matter intake, body weight, and average daily gain in the entire period, as well as the final height of the withers and hips, so that eating pelleted diet along with forage from one day of age improved these traits compared to the group fed with ground diet along with forage from 21 days of age (P<0.05). Also, feeding pelleted feed increased starter feed intake, dry matter intake, body weight, average daily gain, and feed efficiency compared to ground starter feed (P<0.05). Also, the calves consuming the pelleted feed had a higher withers and hip height than the calves consuming the ground diet. On the other hand, the effect of the feeding time of forage on the body weight of calves was significant in the whole period, so that feeding forage from one-day old caused an increase in body weight compared to 21 days old (P=0.021). Also, the average daily gains in the post-weaning period in calves consuming forage from the first day tended to increase compared to 21 days old (P=0.084). In addition, forage feeding from one-day old compared to 21 days old improved feed efficiency and increased the height of the withers (P=0.001) and hip (P=0.025).
Conclusion: Based on the results of this experiment, it can be stated that feeding 10% of alfalfa from one-day old compared to 21 days' old improved the performance (greater body weight and withers and hip height) of dairy calves. Also, pelleted compared to ground starter feed resulted in improved performance, including improved starter intake, average daily gain, and skeletal growth. The interaction effects showed that the use of forage in both the starter feed (ground and pelleted) from of the one day to 21 days leads to improved performance, but this improvement is more in the ground starter feed.