Using corn gluten feed in post-partum diets of young beef cows to optimize reproductive performance

Forty-eight primiparous and diparous Angus-Simmental cows were fed 1 of 3 diets; 1) total mixed ration (TMR) based of corn silage and corn stalks (CON), 2) TMR with 3.3 kg/d DM of corn gluten feed (CGF; MID), or 3) TMR with 6.7 kg/d DM of CGF (HIGH). From 11 ± 5 days post-partum (DPP) to 105 ± 5 DPP, all diets were formulated to be isocaloric for a post-partum ADG targeted at 0.22 kg, but CP exceeded requirements in both CGF diets. Blood samples were collected from cows starting at trial initiation until estrous synchronization for determination of plasma progesterone concentration (7 d intervals), as an indicator of resumption of cyclicity, as well as for plasma urea nitrogen (PUN; 21 d intervals). Milk production was assessed at 62 ± 5 DPP via a weigh-suckle-weigh procedure, and milk samples were collected at 64 ± 5 DPP for composition analysis. A 5 d Co-Synch + Control Internal Drug Release (CIDR) protocol was used and cows were bred by timed artificial insemination (TAI). Trans-rectal ultrasonography was used for the evaluation of the dominant follicle at TAI, as well as pregnancy diagnosis. Nineteen days post-TAI, cow and calf pairs were managed as a single group until weaning (205 ± 5 DPP) and exposed to natural mating for a total of a 60 d breeding season. Dam ADG was not significantly different among treatments (P = 0.849), but, DMI decreased with increasing CGF in the diet (P = 0.049). There were no differences in final BW (P = 0.779), however, final BCS was lower in the HIGH treatment when compared to the MID (P = 0.042). Milk production (P = 0.457), as well as, milk components (P ≥ 0.188) were not different, with the exception of milk fat, which tended to be greater in the HIGH treatment (P = 0.059) when compared to the MID. A treatment by week interaction (P < 0.0001) was found for PUN concentrations. Concentrations were greater in the HIGH treatment compared to the MID treatment at 63, 84, and 105 d, and greater than the CON treatment at all time points except d-42. There were no differences in resumption of cyclicity (P = 0.419), dominant follicle (P = 0.648), or TAI conception rates (P = 0.761). However, season long pregnancy rates were significantly greater in the CGF treatments when compared to the CON (P = 0.009). In summary, feeding high or intermediate amounts of CGF neither has a positive nor negative effect on TAI conception rates of beef cows, however, it positively affected season long pregnancy.