531 - Awardee Talk: Maternal Gestational Nutrition Alters the Postnatal Growth, Immunity, and Carcass Quality of Bos Indicus-Influenced Beef Calves in Tropical/Subtropical Environments

Few studies focused on the role of maternal nutrition during gestation on postnatal development of B. indicus-influenced beef offspring. Hence, three 2-yr studies investigated the effects of timing of prepartum supplementation (Study 1), supplement type (Study 2) and methionine fortification of maternal diets (Study 3) on offspring performance. In Study 1, 84 Brangus multiparous cows/yr were stratified by body weight (BW; 482 ± 75 kg) and body condition score (BCS; 5.3 ± 0.8) and randomly assigned to bahiagrass pastures (14 cows/pasture; 2 pasture/treatment/yr). Treatments were randomly assigned to pastures at approximately 84 d prepartum (d 0) and consisted of no prepartum supplementation (CON), 2 kg/d of dried distillers grains (DDG) from d 0 to 42 (S42), or 1 kg/d of DDG from d 0 to 84 (S84). At weaning (d 347), 38 steers/yr were vaccinated against bovine respiratory disease (BRD) pathogens and transported for 1,193 km to the feedlot and fed the same corn silage based-diet until slaughter. Cows fed S84 and S42 supplements had greater (P ≤ 0.05) BCS at calving vs. CON cows, but only S42 cows had greater (P ≤ 0.05) percentage of calves born from wk 2 to 6 of calving season vs. CON and S84 cows. Calves born from S84 cows were 8 and 14 kg heavier (P ≤ 0.05) at weaning than S42 and CON steers, respectively (269, 261, and 255 kg, respectively). Also, S42 steers had greater (P ≤ 0.05) seroconversion against parainfluenza-3 at weaning vs. CON steers, whereas S84 steers were intermediate. Steer feedlot BW, average daily gain and hot carcass weight (HCW) did not differ (P ≥ 0.36) among treatments, but marbling scores (P = 0.07) and percentage of steers grading choice (P = 0.10) tended to be greater for S42 vs. CON steers, with S84 steers being intermediate. Thus, altering the timing of prepartum DDG supplementation (first 42 d vs. all 84 d of late gestation) in Bos indicus-influenced cows enhanced calf weaning weights, humoral immunity, and carcass quality at different magnitudes compared to those born from non-supplemented cows. In Study 2, 82-84 cows/yr were stratified by BW and BCS (475 ± 67 kg; 4.85 ± 0.73) and randomly assigned to bahiagrass pastures (2 pastures/treatment/yr). Pastures were randomly assigned to treatments (d 0) and consisted of winter supplementation with molasses/urea (WMOL), or year-round supplementation of molasses/urea (YMOL) or range cubes (YCUB). Total yearly supplement DM amount was 272 kg/cow for all treatments and supplements were isocaloric and isonitrogenous (75% TDN, 20% CP; DM basis). At weaning (d 421), 33-35 steers/yr were vaccinated against BRD and transported for 1,193 km to the feedlot, and then fed the same corn silage based-diet until slaughter. Cow BCS at calving was greater (P < 0.01) for YMOL and YCUB vs. CON cows. Calving rate, calving date, calf birth weights, calf pre-weaning BW and ADG did not differ (P ≥ 0.22) among treatments. Steer feedlot BW did not differ (P ≥ 0.36) at feedlot entry but was greater (P ≤ 0.05) for YMOL and WMOL vs. YCUB steers at feedlot exit. Plasma concentrations of cortisol at feedlot entry were greater (P ≤ 0.05) for YCUB vs. WMOL and YMOL steers. Marbling scores and HCW did not differ (P ≥ 0.14) among treatments. Hence, year-round supplementation of range cubes or molasses/urea increased cow BCS at calving but led to minor differences in postnatal offspring growth and immunity compared to maternal supplementation during winter only. Study 3 employed RNA-sequencing on Longissimus dorsi muscle of Bos indicus-influenced beef calves born from heifers offered different diets during pre- and post-partum periods. At 57 days prepartum, 36 Brangus heifers/yr were stratified by BW and BCS and assigned to bahiagrass pastures (3 heifers/pasture). Treatments were randomly assigned to pastures (4 pastures/treatment/yr) and consisted of no pre- and post-partum supplementation (CON), or pre- and postpartum supplementation of molasses and urea (7.2 kg of DM/heifer/d) with (MOL+) or without (MOL-) methionine fortification (105 g/heifer/wk) from 57 ± 5 d prepartum until 17 ± 5 d postpartum. Calves were weaned on d 147 (3-4 months of age) and limit-fed a high-concentrate diet DM at 3.5% of BW until d 201. Muscle biopsies were collected on d 154 and 201. Molasses supplementation (MOL- and MOL+) down-regulated genes associated with muscle cell differentiation and development along with intracellular signaling pathways compared to no maternal supplementation. Methionine fortification of maternal supplements altered functional gene-sets involved in muscle one-carbon cycling and amino acid transport and metabolism. Together, our studies demonstrated that maternal supplementation of Bos indicus-influenced cows led to variable long-term effects to offspring growth, carcass quality, humoral immunity, and muscle gene expression, and also offered practical nutritional strategies to enhance beef cattle production in challenging tropical/subtropical environments.