Date of this Version
Harms, J. D. 2013. Effects of Maternal Nutrition and Post-Weaning Management in a Late Spring Calving System and Synchronization of Estrus using Fixed Time AI Protocols. MS Thesis. University of Nebraska-Lincoln.
Three experiments were conducted to determine the impact of development systems, maternal protein supplementation, and estrus synchronization systems on beef cattle. Experiment 1 evaluated the effects of winter supplementation on cow performance and the effects of post-weaning management on progeny. Late spring calving cows grazed dormant range or meadow over winter and received either supplementation or no supplementation. Steer and heifer progeny were weaned and placed on dormant meadow or fed hay ad libitum. One half of the steers were placed in the feedlot at the end of treatment and the other half grazed range over summer. Cow winter treatment did not affect cow performance. Steers and heifers fed hay had increased ADG during winter trt compared to calves on meadow. Feedlot system did not have a significant effect on carcass data. In experiment 2, cows were synchronized for fixed-time AI (TAI) utilizing the CO-Synch and the CO-Synch + CIDR protocols. Cows synchronized with the CO-Synch + CIDR protocol had increased AI pregnancy rates compared to CO-Synch synchronized cows. In experiment 3, heifers were synchronized for TAI using the MGA + PGF2α protocol or CO-Synch + CIDR protocol. Half of the CO-Synch + CIDR heifers received PGF2α at the time of CIDR insertion. Heifers were time stamped at the time of final PGF2α administration and at the TAI. Pregnancy rates were not affected due to PGF2α administration at the time of CIDR insertion or time interval between final PGF2α administration and TAI. In summary, these experiments provide evidence to support the following findings: (1) there are minimal effects of winter supplementation on late spring calving cows and progeny performance; (2) post-weaning treatment had minimal effects on heifer and steer productivity; (3) cows utilizing CO-Synch + CIDR AI protocol have higher pregnancy rates; (4) fluctuations in time interval from time of PG administration to breeding had no effects on pregnancy rates.
Advisors: Richard N. Funston and Brett R. White