Influence of Maternal Corn Supplementation of Beef Cattle on Muscle Fiber Type and Meat Quality of their Offspring

ObjectivesTo determine the influence of corn supplementation of beef cows during winter and their impact on offspring beef quality attributes.Materials and MethodsForty-seven multiparous Angus beef cows carrying male calves were assigned randomly to two dietary treatments: corn supplementation at 0.2% BW (SUP; n = 24) vs. non-supplementation (NSUP; n = 23) at d 110 d of gestation for 22 wks. Ad-libitum access to low-quality forage was provided to both groups. At 7 d post-calving, a muscle biopsy was collected from the longissimus dorsi muscle (LD) of each calf for muscle fiber typing. Offspring were managed as a single group from nursing through to the backgrounding phase. Thereafter, the steers were placed in the feedlot and assigned to 4 pens (blocks) based on BW and offered ad-libitum access to a 100% corn silage-based ration (76.97% TDN, 11.07% CP), salt and minerals. When the steers reached a final BW of 615 kg (∼16 mo of age), they were slaughtered in a commercial abattoir. A second LD muscle biopsy sample was obtained at 45 min postmortem (PM) for muscle fiber typing. At 96 h PM, striploins (n = 42) were collected, aged for 14 d and samples obtained for Warner Bratzler shear force (WBSF), proximal composition, myofibril fragmentation index (MFI), collagen analysis and objective color evaluation. Data were analyzed as a randomized block design.ResultsImmunofluorescent analysis for the myosin heavy chain (MHC) isoform on the proportion of the fiber type or fiber dimensions was not influenced by maternal dietary treatment at both ages (P > 0.05). However, regardless of maternal dietary treatment, the proportion of fiber type IIA decreased while type IIAX increased in samples from steers at 16 mo of age compared with samples from steers at 7 d of age. No differences were observed between dietary treatment groups in proximate composition (P = 0.8), MFI (P = 0.29), or collagen content (P 0.98); however, WBSF values tended to be higher in steers from SUP cows than steers from NSUP dams (P = 0.07). Maternal dietary treatment had no influence on objective color evaluation at the retail display (P > 0.05). Objectives traits were not affected by dietary treatment × display time interaction (P = 0.92).ConclusionOur findings indicate that corn supplementation of cows during mid to late gestation has minimal effects on muscle fiber type and beef quality of their offspring. Thus, corn supplementation of low-quality forage offered during mid to late gestation did not have detrimental effects on muscle fibers and meat quality of offspring.

Effect of increasing proportion of supplemental N from urea in prepartum supplements on range beef cow performance and on forage intake and digestibility by steers fed low-quality forage

Four experiments were conducted to evaluate the influence of changing the proportion of supplemental degradable intake protein (DIP) from urea on forage intake, digestion, and performance by beef cattle consuming either low-quality, tallgrass prairie forage (Exp. 1, 2, and 4) or forage sorghum hay (Exp. 3). Experiments 1, 2, and 3 were intended to have four levels of supplemental DIP from urea: 0, 20, 40, and 60%. However, refusal to consume the 60% supplement by cows grazing tallgrass prairie resulted in elimination of this treatment from Exp. 1 and 2. Levels of supplemental DIP from urea in Exp. 4 were 0, 15, 30, and 45%. Supplements contained approximately 30% CP, provided sufficient DIP to maximize digestible OM intake (DOMI) of low-quality forage diets, and were fed to cows during the prepartum period. In Exp. 1, 12 Angus x Hereford steers (average initial BW = 379) were assigned to the 0, 20, and 40% treatments. Forage OM intake, DOMI, OM, and NDF digestion were not affected by urea level. In Exp. 2, 90 pregnant, Angus x Hereford cows (average initial BW = 504 kg and body condition [BC] = 5.0) were assigned to the 0, 20, and 40% treatments. Treatment had little effect on cow BW and BC changes and calf birth weight, ADG, or weaning weight. However, pregnancy rate tended to be lowest (P = 0.13) for the greatest level of urea. In Exp. 3, 120 pregnant, crossbred beef cows (average initial BW = 498 kg and BC = 4.6) were assigned to the 0, 20, 40, and 60% treatments. Prepartum BC change tended (P = 0.08) to be quadratic (least increase for 60% treatment), although BW change was not statistically significant. Treatment effect on calf birth weight was inconsistent (cubic; P = 0.03), but calf ADG and weaning weight were not affected by treatment. Pregnancy rate was not affected by prepartum treatment. In Exp. 4, 132 pregnant, Angus x Hereford cows (average initial BW = 533 and BC = 5.3) were assigned to the 0, 15, 30, and 45% treatments. Prepartum BC loss was greatest (quadratic; P = 0.04) for the high-urea (45%) treatment, although BW loss during this period declined linearly (P < 0.01). Prepartum treatment did not affect pregnancy rate, calf birth weight, or ADG. In conclusion, when sufficient DIP was offered to prepartum cows to maximize low-quality forage DOMI, urea could replace between 20 and 40% of the DIP in a high-protein (30%) supplement without significantly altering supplement palatability or cow and calf performance.