University of Guilan Animal Production Research 2252-0872 8 4 2020 02 20 Effect of corn silage and its supplementation time in starter diet on the performance and rumen parameters of suckling Holstein calves Effect of corn silage and its supplementation time in starter diet on the performance and rumen parameters of suckling Holstein calves 29 38 3532 10.22124/ar.2019.12403.1380 FA M. Hosseinabadi Ph.D Student, Department of Animal Science, University College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran K. Rezayazdi Associate Professor, Department of Animal Science, University College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran M. Dehghan-Banadaky Professor, Department of Animal Science, University College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran Journal Article 1970 01 01 The objective of this study was to evaluate the effect of corn silage as source forage and its supplementation time in starter on feed intake, growth performance and rumen parameters in suckling Holstein calves. Thirty-two Holstein calves (16 males and 16 females) from 5 d to 70 d of old were used in a complete randomized design with a 2 × 2 factorial arrangement of treatments. Dietary treatments were as follows: starter with 10% alfalfa at 5 d old calves, starter with 10% alfalfa at 30 d old calves, starter with 10% corn silage at 5 d old calves and starter with 10% corn silage at 30 d old calves. The effect of forage source and time of using forage in the starter on average daily gain (ADG), feed intake and some rumen parameters was significant (<em>p < /em><0.05). Effect of treatments on glucose, blood urea nitrogen concentration and fecal score was not significant. However, the effect of treatments on beta hydroxyl butyric acid concentration in calves was significant (<em>p < /em><0.01). Results showed that calves consumed corn silage at five d of old had the highest average daily gain, feed intake, total volatile fatty acids (VFA), propionate and acetate. According to the results of this experiment, the best time of supplementing forage in the starter diet of suckling calves is five day of old.</em></em> The objective of this study was to evaluate the effect of corn silage as source forage and its supplementation time in starter on feed intake, growth performance and rumen parameters in suckling Holstein calves. Thirty-two Holstein calves (16 males and 16 females) from 5 d to 70 d of old were used in a complete randomized design with a 2 × 2 factorial arrangement of treatments. Dietary treatments were as follows: starter with 10% alfalfa at 5 d old calves, starter with 10% alfalfa at 30 d old calves, starter with 10% corn silage at 5 d old calves and starter with 10% corn silage at 30 d old calves. The effect of forage source and time of using forage in the starter on average daily gain (ADG), feed intake and some rumen parameters was significant (<em>p < /em><0.05). Effect of treatments on glucose, blood urea nitrogen concentration and fecal score was not significant. However, the effect of treatments on beta hydroxyl butyric acid concentration in calves was significant (<em>p < /em><0.01). Results showed that calves consumed corn silage at five d of old had the highest average daily gain, feed intake, total volatile fatty acids (VFA), propionate and acetate. According to the results of this experiment, the best time of supplementing forage in the starter diet of suckling calves is five day of old.</em></em> https://ar.guilan.ac.ir/article_3532_b14f353460982edd41a8ebc443a1d103.pdf