|ROSENKRANS, JR, C|
Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/3/2003
Publication Date: 2/14/2004
Citation: FLORES, R., LOOPER, M.L., KREIDER, D.L., ROSENKRANS, JR, C.F. 2004. INFLUENCE OF PROGESTERONE ON ESTROUS CHARACTERISTICS AND PREGNANCY RATE OF GRAZING BEEF COWS. AMERICAN SOCIETY OF ANIMAL SCIENCE SOUTHERN SECTION MEETING. 82(Suppl. 2):20.
Technical Abstract: Eighty-four multiparous, cross-bred cattle (1/4 to 3/8 Brahman) were utilized to evaluate the effects of progesterone on estrous characteristics and pregnancy rates. Prior to the breeding season, 3 wk blood samples were collected and progesterone (P4) was quantified to determine luteal activity. Cows grazed common bermudagrass paddocks throughout the breeding season, and cows received P4 via an intravaginal insert (CIDR) or no P4 on Day 1 of the breeding season. On Day 7, CIDRs were removed and cows receiving CIDRs were administered prostaglandin F2' (PGF2'). All cows were exposed to bulls and fitted with a HeatWatch transmitter to record estrous activity during the first 30 d of the breeding season. At initiation of the breeding season, body weight and body condition score averaged 557 ± 65 kg and 6.3 ± 0.8, respectively, for all cows. Thirty-seven percent of cows were anestrus at breeding. Duration of estrus and quiescence between mounts were similar (P > 0.10) between cows with and without a CIDR. Mean duration of estrus and quiescence between mounts averaged 7.3 ± 0.8 h and 2.3 ± 0.3 h, respectively. However, cows with a CIDR had an increased (P < 0.05) number of mounts (25.4 ± 2.3) compared with cows without a CIDR (17.0 ± 2.9). Sixty-seven percent of cows administered a CIDR and PGF2' exhibited estrus within 72 h after CIDR removal. More anestrous cows administered a CIDR for 7 d tended (P = 0.12) to exhibit estrus during the first 30 d of the breeding season than anestrous cows without a CIDR. Pregnancy rates were similar between CIDR treatments. Exposure to P4 for 7 d via a CIDR increased the number of mounts during estrus and tended to initiate estrus in anestrous Brahman-influenced cows.