effects of replacing corn silage with varying levels of ammonia gassed wheat straw on performance, fermentation parameters and blood metabolites in holstein heifers

the replacement of corn silage with varying levels of ammonia gassed wheat straw on performance, digestibility, fermentation parameters, chewing activities, blood metabolites and profitability of holstein heifers have been evaluated. fifteen holstein heifer with 9-10 months of age were assigned in a completely randomized design with 3 treatment as 1) 36% corn silage, 2) 18% corn silage and 18% wheat straw and 3) 36% treated wheat straw and 5 replicates for 2 months. straw presses treated with 4% ammonia gas for 30 days. the results showed that the difference in dry matter intake and average daily weight gain and wither sheight among treatments is not significant. digestibility of dm, cp, adf and ndf in treatment 1 was significantly higher than other treatments. ruminal ph and ammonia nitrogen in treatment 3 as were significantly higher than other treatments. eating time, rumination time and total chewing time in treatment 3 was significantly higher than the other two treatments. blood urea nitrogen in treatment 3 than the other two treatments and blood albumin in treatment2 were significantly higher than the other two treatments. glucose, cholesterol, tg and ast and alt had no significant difference among treatments. in general, for every kilogram of weight gain, in treatment 3 and treatment 2 as compared to treatment 1, 3860 and 3935 rials were saved respectively the results showed that the treated straw with 4% ammonia gas can be completely replaced corn silage in the diet of holstein heifers without negative impact on their performance.