Abstract Maternal nutrition during gestation may influence offspring’s microbiome, potentially programming long-term differences in growth and metabolic efficiency in finishing steers. Microbial development in utero could affect how offspring adapt to diets during the finishing phase. This study evaluates the impact of feeding high-forage vs. high-concentrate diets to pregnant heifers on offspring growth performance, dry matter intake, nutrient digestibility, and gas exchange during the finishing phase. Heifers (n = 41) predominately of Angus breed were blocked by initial BW and randomly assigned individually to either feeding a high-forage (85% forage) or high-concentrate (85% concentrate) diet using an Insentec feeding system. Diets were formulated to target 0.45 kg/day from 15 days before breeding until two-thirds of gestation and 0.79 kg/day during the last third of gestation. Heifers were bred using artificial insemination with male-sexed semen from the same sire. Following calving, all cows and calves were managed similarly and after weaning steers were fed backgrounding diets for approximately 3 months before entering the finishing phase. Steers (initial BW ± standard deviation = 293 + 21 kg) were blocked by BW, fed individually using Calan gates, and adapted to a high concentrate diet for two weeks before being placed on a finishing diet for 77 ± 7 days. A subset of steers (n = 22) was selected for a nutrient and energy balance experiment. Feed intake, fecal and urinary excretion were collected over a 5-day period and composite gas samples entering and exiting each headbox were analyzed for O2, CO2, and CH4 concentration over a 24-hour period utilizing headboxes. Digestibility of DM, OM, NDF, ADF, starch, and CP was measured. Data were analyzed as a completely randomized block design with treatment (n = 2) and BW block effects using the MIXED procedure of SAS. Treatment had no effect on slaughter weight, ADG, or DMI, nor were there differences in O2 (P = 0.28), CO2 (P = 0.31), CH4 (P = 0.71), or respiratory quotient (P = 0.75). However, steers from heifers fed the high-forage diet were heavier (P = 0.007; 522 vs 496 kg) at the time of the nutrient and energy balance experiment. Digestibility of DM, OM, NDF, ADF, starch, and CP did not differ between treatments. Overall, the greater BW in steers from the heifers fed high-forage diets and the lack of difference in dry matter intake, gas exchange measurements, and digestibility suggest potentially a metabolic difference between treatment groups. Analysis of energy digestibility and balance should provide further insight on how maternal diet (forage:concentrate) influences efficiency of nutrient and energy utilization in steers fed finishing diets.
Finck et al. (Wed,) studied this question.