PSII-30 - Effect of dietary alpha-amylase enzyme supplementation on growth performance and carcass quality of crossbred dairy beef bulls fed pellet or mash high-concentrate diets

Abstract: The aim of this study was to evaluate the effect of dietary alpha-amylase supplementation on growth performance and carcass quality in crossbred dairy beef bulls fed either pellet or mash high-concentrate diets. Two parallel studies were conducted in two barns: in the first barn, one hundred thirty eight bulls (170 ± 2.3 kg of BW, and 148 ± 0.7 days of age) were grouped in 8 pens of 16-19 animals/pen and fed pelleted concentrate (PELLET study); and in the second barn, one hundred forty eight bulls (180 ± 1.6 kg of BW, and 150 ± 0.7 days of age) were grouped in 8 pens of 17-19 animals/pen and fed mash concentrate (MASH study). All bulls were fed concentrate (Table 1), straw, and water ad libitum. In each study, pens were assigned to one of 2 treatments: 1) CTR, no amylase supplementation; 2) RUM, RumiStar600 CT^TM concentrate inclusion (630 mg/kg DM, based on 600 kilo novo units (KNU) of alpha-amylase activity). After 196 days, divided in 7 28-days periods, where daily concentrate intake per pen, and BW per animal every 28 days was recorded animals were transported to slaughterhouse at different days within a month. Also, on days 0, 42, 84 and 168 concentrate samples were collected for enzyme activity and nutrient content analyses. Carcass quality was recorded at the slaughterhouse, bulls of PELLET study were slaughtered on average at 236 days of study and bulls of MASH study were slaughtered on average at 226 days of study. Data of each study were analyzed using a mixed model. In PELLET study, growth performance and carcass quality were not affected by treatments, however conformation grade (SEUROP) was improved (P = 0.03) in RUM bulls compared with CTR bulls (score R: 18 vs. 5 %; score O: 54 vs. 56 %; score P: 28 vs. 39 %; RUM vs. CTR, respectively). Moreover, feed conversion ratio (FCR) was numerically (P = 0.11) improved in RUM fed bulls compared with CTR fed bulls (4.65 vs. 4.99 kg DM/kg, RUM vs. CTR, respectively;). In the MASH study, only an interaction between treatment by time in BW (P = 0.04) was observed; RUM bulls tended to be heavier than CTR bulls in the period 7 (476 vs. 470 ± 3.2 kg, RUM vs. CTR, respectively; P = 0.10). In conclusion, in crossbred dairy beef bulls fed high-concentrate diets with alpha-amylase supplementation (600 KNU of alpha-amylase activity/kg DM of concentrate) for at least 196 days improved FCR and carcass conformation grade when concentrate presentation form was pellet.