Effect of dried distiller's grains plus solubles in postpartum diets of beef cows on reproductive performance of dam and heifer progeny.

Forty-eight primiparous and multiparous cows were fed a silage-based total mixed ration (TMR; CON), a TMR with 2.5 kg/d DM dried distiller's grains plus solubles (DDGS; MID), or a TMR with 4.7 kg/d DM DDGS (HIGH) from 8.5 +/- 4 to 116 +/- 4 d postpartum (DPP). All diets were formulated to be isocaloric for a postpartum ADG targeted at 0.22 kg, whereas CP exceeded requirements in both diets containing DDGS. Blood samples were collected from dams at 7- and 21-d intervals for progesterone concentration (resumption of cyclicity) and plasma urea nitrogen, respectively. A weigh-suckle-weigh procedure was used to measure milk production, and samples were collected for milk composition and fatty acid profile. A 5-d Co-Synch + controlled internal drug release (CIDR) protocol was used, and cows were bred (97 +/- 4 DPP) by timed AI (TAI). Ultrasonography was used for measurement of the largest antral follicle at TAI and pregnancy diagnosis. Nineteen days after TAI, cow and calf pairs were managed as a single group until weaning and exposed to natural mating for a total of a 60-d breeding season. Starting at weaning, blood samples were collected from heifer offspring at 7-d intervals for progesterone concentration used as an indicator of puberty. A 5-d Co-Synch + CIDR protocol was used, and heifers were bred by TAI. Transrectal ultrasonography was used for measurement of the largest antral follicle at TAI and antral follicle count (AFC) at CIDR device insertion as well as pregnancy diagnosis. There were no differences in dam ADG (P = 0.364); however, DMI decreased with increasing DDGS (P < 0.0001), resulting in an increased feed efficiency (P = 0.042). Milk fat and lactose tended to increase with the addition of DDGS in the diet (P = 0.055), and milk urea nitrogen increased (P < 0.001). There were no differences in resumption of cyclicity (P = 1.00) or diameter of the largest antral follicle (P = 0.372). Timed AI pregnancy rates were not different with the addition of DDGS in the diet (P = 0.174). Heifer ADG was reduced with DDGS during late lactation (P = 0.031). Heifer AFC had a tendency to increase with increasing DDGS (P = 0.081), with no impacts on dominant follicle diameter at TAI (P = 0.161). Heifer TAI pregnancy rate also was not different among treatments (P = 0.508). Overall, feeding 4.7 kg/d DM of DDGS to dams during early lactation increases feed efficiency of the dam, with minor statistically significant effects on dam or heifer offspring reproduction.