REPRODUCTIVE-PERFORMANCE OF SYNCHRONIZED BEEF-COWS AS AFFECTED BY INHIBITION OF SUCKLING WITH NOSE TAGS OR TEMPORARY CALF REMOVAL

A study was conducted to determine whether presence of the calf during suckling inhibition influences the response to estrus synchronization in beef cows. Angus or Hereford cows (n = 89) were administered Syncr o-Mate-B(R) (SMB), which consisted of a 6-mg norgestomet ear implant ( in situ 9 d) in conjunction with 5 mg of estradiol valerate and 3 mg ( im) of norgestomet. Cows were allotted by breed, body condition, stage of the estrous cycle, parity and date of parturition to 1 of 3 treatm ents: 48-h calf removal; ad libitum suckling; or inhibition of sucklin g with a nose tag for 48 h. Calves were weighed at time of SMB implant removal, 48 h later and at weaning. Cows were mated via AI approximat ely 12 h after detection of estrus during a 30-d period after implant removal followed by a natural service period of 35 d. At 48 h after im plant removal, calf removal and nose tag calves had lost an average of 3.6 and 0.9 kg, respectively, while the suckled calves gained 1.8 kg (P<0.01). Mean calf weight at weaning did not differ among treatments. Synchronized estrous response (within 5 d of implant removal) was not different among treatments. Pregnancy rate for cows exhibiting a sync hronized estrus (5 d AI) for calf removal, nose tag and suckled cows w as 76, 48 and 48%, respectively (P>0.10). Treatment did not affect the 30-d AI or overall 65-d pregnancy rate. In this study, there were no differences observed in the percentage of synchronized or pregnant cow s following suckling inhibition by either a nose tag or calf removal. Transient reductions of calf body weight during the 48-h calf removal period did occur in both the nose tag and calf removal groups.