J.C. Whittier

OVARIAN AND ESTROUS RESPONSE OF SUCKLED BEEF COWS TO SELECT SYNCH ESTROUS SYNCHRONIZATION PROTOCOL

Abstract This study evaluated ovarian and estrous responses as affected by day of the estrous cycle at initiation of treatment among cows synchronized with the Select Synch protocol. Fifty-six suckled Hereford x Red Angus multiparous cows were fitted with HeatWatch® electronic estrous detection monitors 22 d before initiation of treatment. Thirty-two percent of cows were not detected in estrus during this 22-d period, and were classified as anestrus. Treatment included an injection of Gonadotropin releasing hormone (GnRH; 100 μg) on d 7, followed by an injection of Prostaglandin F 2 α (PGF 2 α ; 25 mg) on d 0. Ovaries of cows were scanned daily via ultrasound from d 12 until the time of insemination to evaluate follicular and luteal response to the GnRH and PGF 2 α injections. Cows were visually observed for signs of estrus twice daily from d 0 to d 5 for approximately 2xa0h to compare visual detection of estrus with electronic detection. There was no difference (P>0.5) in the percentage of cows detected in estrus between visual (85%) and electronic (88%) observation. Ovarian and estrous responses to the GnRH and PGF 2 α injections were dependent on day of the estrous cycle when the protocol was initiated. Ovulation resulting in formation of a new corpus luteum (CL) and follicular turnover occurred following the injection of GnRH in 66 and 70% of cows, respectively. Only 14% of cows that were between d 15 and 17 of their estrous cycle responded to either GnRH or PGF 2 α administration. Additionally, these cows exhibited estrus 11 ± 19xa0h (mean ± SD) before injection of PGF 2 α . Anestrous cows exhibited estrus earlier (P 2 α injection is important.

Effects of a Timed Insemination Following Synchronization of Ovulation Using the Ovsynch or CO-Synch Protocol in Beef Cows

Abstract This study compared pregnancy rates of suckled beef cows that were time inseminated following synchronization of ovulation using the Ovsynch protocol. Multiparous beef cows (n=771) within each of three locations were stratified by breed type, age, postpartum interval, and AI sire, and randomly allotted to receive either the Ovsynch or CO-Synch protocol. The Ovsynch protocol consisted of an injection of GnRH (100 μg) on d 0, an injection of PGF 2α on d 7, another injection of GnRH (100 μg) on d 9, and timed insemination on d 10. The CO-Synch protocol consisted of the same hormone injection schedule as the Ovsynch protocol, but cows were time inseminated on d 9, when the second GnRH injection was administered. Pregnancy rates did not differ between treatments at each location ( P >0.1). However, when data were pooled across location, pregnancy rate was higher ( P =0.02) for cows that received the Ovsynch protocol (57%) than for cows that received the CO-Synch protocol (49%). No difference ( P >0.1) in pregnancy rate due to cow age, postpartum interval, body condition score, age by treatment, or postpartum interval by treatment was detected among pooled data. Among cows with a body condition score of 6.0 or greater, pregnancy rates were higher ( P =0.04) for Ovsynch treated cows (72%) than for CO-Synch treated cows (53%). These data demonstrate that the Ovsynch and CO-Synch protocols result in acceptable pregnancy rates to a timed insemination in beef cows. Whether the increase in pregnancy rates obtained using the Ovsynch protocol will warrant handling cows a fourth time for insemination will likely vary by management intensity.

Feeder Cattle Health Management: Effects on Morbidity Rates, Feedlot Performance, Carcass Characteristics, and Beef Palatability1,2

Abstract The effects of morbidity, defined as hospital visits per calf during the feeding period, on feedlot performance, carcass characteristics, and beef palatability traits were determined using 273 steer calves originating from one of two preconditioning programs or auction barns. Cattle treated more than once at the feedyard had a 12% lower ADG through reimplant (67 d; P 0.05) were noted in the effects of hospital visits or preconditioning treatments on beef tenderness and palatability measures. Overall, morbidity resulted in economic losses as a result of mortality and increased costs associated with hospital treatment. Morbidity also decreased (P

Effects of Trace Mineral Supplementation on Cow-Calf Performance, Reproduction, and Immune Function

Abstract Three-hundred Angus cows were used in a randomized design to evaluate trace mineral supplementation over a 209-d trial on cow and calf performance, liver trace mineral content, and immune function. Treatments included the following supplemental trace minerals: 1) inorganic trace minerals—low level; 2) inorganic trace minerals—high level; and 3) organic trace minerals—high level. Cows fed the high level of inorganic trace minerals lost more weight (P

Estimation of Net Present Value of Beef Females of Various Ages and the Economic Sensitivity of Net Present Value to Changes in Production

Abstract The objective of this study was to economically evaluate the value of future production and the economic sensitivity to changes in production throughout the life of the beef female in a cow-calf production system. Production and cost data were obtained from an existing ranching operation during the 1996 production year. A Net Present Value (NPV) analysis was used to determine the value of future production. Present values for 1-, 2-, 3-, 4-, 5-, 6-, and 7-yr-old beef cows were

Fibrous and Nonfibrous Carbohydrate Supplementation to Ruminants Grazing Forage from Small Grain Crops

786,

Impact of oral meloxicam administration before and after band castration on feedlot performance and behavioral response in weanling beef bulls

1027,

Effects of Copper, Zinc, and Manganese Source on Mineral Status, Reproduction, Immunity, and Calf Performance in Young Beef Females over a Two-Year Period123

1146,

Evaluation of Gonadotropin-Releasing Hormone and Insemination Time Using the CO-Synch Protocol in Beef Cows

1210,

Reducing Annual Cow Cost by Grazing Windrowed Millet

1171,