PSXII-23 Effect of dietary straw withdrawal in high-concentrate diets on animal behavior in dairy beef crossbred bulls housed with straw bedding

Abstract The aim of this study was to evaluate the effect of dietary straw withdrawal in high-concentrate diets on animal behavior in dairy beef crossbred bulls housed with straw bedding. Bulls [n = 93; body weight (BW) = 335 ± 9.0 kg, and 218 ± 4.0 d of age) were group-housed in a partially opened barn with 6 pens straw-bedded cleaned every 2 wk. Animals were assigned to one of 3 different feed programs: 1) CTR (n = 32), concentrate (13.1% crude protein (CP), 5.9% fat content, 16.1% neutral detergent fiber (NDF), 40.8% starch content) and straw ad libitum fed in two separate feeders; 2) TSW (n = 32), like CTR; however, dietary straw withdrawal took place the first 84 study days; and 3) NSS (n = 29), concentrate with a lower starch content (12.2% CP, 4.6% fat content, 22.0% NDF, 39.6% starch content) without a dietary straw for the whole study. The study lasted 155 d divided into eleven 14-d periods. General activities and postures were recorded through scan sampling every 5 min, and social behavior was recorded during 5 min of continuous sampling in two rounds of 15 min. Social behaviors were transformed to a log scale to achieve a normal distribution. Data were analyzed with a mixed-effects model. The first period was an adaptation where a dietary straw bale per pen was offered in all treatments; thereafter, only in CTR, and in TSW after period 6. Percentage of bulls eating at the concentrate feeder was greater (P = 0.05) in NSS than in CTR and TRW (5.87 vs. 4.64 and 4.82 ± 0.038 %, respectively). The percentages of bulls ruminating at the beginning of the study were greater (P < 0.01) in CTR compared with TSW and NSS, but after dietary straw was offered in TSW, the percentages of bulls ruminating increased in TSW and were greater in CTR and TSW than in NSS. At the beginning of the study, during the dietary straw withdrawal in TSW bulls, the number of oral behaviors and stereotypies were greater (P < 0.01) in TSW than in CTR, but after straw offer in TSW oral behaviors and stereotypies were only greater in NSS than in CTR and TSW. In conclusion, short- and long-term dietary straw withdrawal increased behaviors indicative of poor animal welfare regardless of the starch content in the concentrate in dairy beef crossbred bulls fed high-concentrate diet housed with straw bedding.