Medicine and Health Sciences Commons^™

Artificial Insemination And Fetal Programming In Beef Production Systems, Dempster Christenson

Department of Animal Science: Dissertations, Theses, and Student Research

Pregnancy to artificial insemination and late gestation fetal programming of the next calf crop are central to genetic development, reproductive longevity, calf crop productivity, and efficiency of cow/calf ranching. The purposes of this research are to find methods to improve pregnancy rate to artificial insemination, the growth and reproductive health of pregnant heifers, and the productivity of their offspring. In the first of four studies we found that extending the period of progesterone administration in an estrus synchronization protocol did not significantly hasten estrus response or increase pregnancy rate to artificial insemination, but timing of estrus within the melengestrol acetate …

Beef Cattle Management Systems For Estrus Synchronization And Heifer Development, Hazy Rae Nielson

Department of Animal Science: Dissertations, Theses, and Student Research

Four experiments were conducted to evaluate estrus synchronization and heifer development systems. In the first experiment delaying AI 19 h following GnRH administration in a hybrid estrus detection and time AI protocol was evaluated. Final pregnancy rate was not different among heifers detected in estrus, AI at the time GnRH administration, or delayed AI. The second study compared the effect of melengestrol acetate (MGA) -PG and 14-d controlled internal drug release (CIDR) -PG estrus synchronization protocols on estrus response and pregnancy rates of 311 d old heifers. Final pregnancy rate was similar between CIDR and MGA treatment groups. The objective …

Genetic Parameter Estimates And Breed Effects For Calving Difficulty And Birth Weight In A Multi-Breed Population, Cashley Ahlberg

Department of Animal Science: Dissertations, Theses, and Student Research

There are multiple breeds of beef cattle available to utilize in breeding systems to maximize production and economics. Calving difficulty (dystocia) is a significant cost to beef production and is more prevalent in first-calf heifers. The objectives of this study were to estimate genetic parameters and breed differences for calving difficulty and birth weight as a first step towards the development of across-breed adjustment factors for calving difficulty.

Two models were employed to analyze birth weight (BWT) and calving difficulty (CD) recorded on 4,579 first parity females from the Germplasm Evaluation program at the U.S. Meat Animal Research Center (USMARC). …