Submitted to: Proceeding of Plains Nutrition Council Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 3/18/2014
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: Data from 3 serial harvest trials were utilized to calculate phosphorus and calcium retention in cattle. Trial 1 evaluated three rates of gain during a growing period followed by a common finishing diet utilizing British crossbred steers. Four steers were harvested from each treatment following the growing period (120 d) and an additional six steers per treatment were harvested following the finishing period (89-163 d). Mineral retention was determined for the finishing period. Trial 2 evaluated four feeding programs utilizing British crossbred steers. Four steers were harvested prior to the growing phase at d 0, six steers were harvested from each of 3 growing treatments at d 112, and 6 steers were harvested from all 4 treatments at the end of the finishing period (104-196 d). Mineral retention was determined for the growing and finishing periods. Trial 3 evaluated Zilmax inclusion in a finishing cattle diet utilizing calf-fed Holstein steers. Five steers were harvested after 226 d on feed (average 371 d of age); this was prior to treatments being imposed and was considered d 0. After d 0, five steers per treatment were harvested every 28 d through 308 d for 11 additional harvest points. At harvest carcasses were broken down into lean, bone, internal cavity, hide, and fat tissues. In all trials mineral retention within the body was calculated as the difference between mineral composition at slaughter and predicted mineral composition at d 0. Mineral composition at d 0 was predicted from body composition of steers harvested at d 0 multiplied by live weight of individual animals at d 0. Due to the short interval between harvest points in Trial 3 (28 d) and no differences in P and Ca composition of the bone portion of the body over time (P > 0.89), initial P and Ca composition of the bone fraction was predicted using individual steer mineral composition instead of d 0 harvested cattle. Mineral retention was then expressed as grams per d, grams per kg of EBW gain, and grams per 100 g of protein gain. There were no differences due to treatment for P retention in Trial 1 (P > 0.15). There were no differences due to treatment and no differences between the growing and finishing periods for P retention (P > 0.36) in Trial 2. Total EBW P retention did not differ by treatment (P > 0.12) and decreased linearly over time (P < 0.01) in Trial 3. Averaged over all treatments, total EBW P retention was 4.14, 4.27, and 7.45 g P/100 g protein gain in Trials 1, 2, and 3, respectively. There were no differences due to treatment for Ca retention in Trial 1 (P > 0.09). There were no differences due to treatment and no differences between the growing and finishing periods for Ca retention (P > 0.23) in Trial 2. Total EBW Ca retention did not differ by treatment (P > 0.11) and decreased linearly over time (P < 0.01) in Trial 3. Averaged over all treatments, total EBW Ca retention was 13.41, 8.24, and 14.44 g Ca/100 g protein gain in Trials 1, 2, and 3, respectively.