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Effect of supplementing gestating and lactating beef cows with supranutritional concentrations of vitamin D on feedlot performance and carcass characteristics of the progeny
The last 100 d of gestation (Nov-Mar) in spring-calving cows coincides with the lowest sunlight and lowest potential to synthesize vitamin D (VD), potentially causing VD deficiency. Low maternal VD has a significant influence on offspring growth potential, as the VD status of neonatal calves is primarily dependent on the VD status of the dam. Furthermore, VD status of progeny could ultimately impact carcass quality. Thus, we hypothesized that supranutrtional VD provided to cows would improve growth and carcass characteristics of male progeny. Crossbred cows were allotted by BW, BCS, and breed to 4 treatments to determine the effect of supranutritional VD during gestation and/or lactation on feedlot performance of male progeny. At 173 d in gestation, cows were allotted to treatments and fed a molasses block that provided 6300 (LD) or 100,000 (HD) IU VD daily. At the mid-point of the calving season, cows were placed on lactation treatments (LD or HD). Treatments were arranged as a 2x2 factorial: LD in gestation, followed by LD (LDLD) or HD (LDHD) in lactation, or HD in gestation followed by LD (HDLD) or HD (HDHD) in lactation. Treatments concluded at 79 d postpartum and cattle were commingled and managed as one group until feedlot entry, which occurred at 236 d of age. Steers (n = 65, BW = 312 ± 19.5 kg) were allotted to feedlot pens (4 or 5 steers/pen) based on maternal diet and were fed a common diet containing 300 IU of VD/kg until slaughter. Statistical analyses were conducted using the MIXED procedures of SAS. BW did not differ among treatments, however, progeny from cows fed HD during lactation tended (P = 0.10) to gain faster and had greater gain:feed (P = 0.04) the first 78 d than progeny from cows fed LD during lactation. ADG and gain:feed from d 79 to slaughter and from feedlot entry to slaughter did not differ (P ≥ 0.22) and DMI did not differ (P ≥ 0.15) among treatments. Progeny from cows fed HD during gestation produced carcasses with less backfat (P = 0.04) that tended (P = 0.08) to have lower yield grades compared with progeny from cows fed LD during gestation. No other carcass trait differed among treatments (P ≥ 0.12). In conclusion, adding supranutritional VD to gestating and lactating cow diets may alter the pattern and composition of growth of the progeny.
Keywords: beef, vitamin D, developmental programming