Wp. Hansen et al., MULTI-FARM USE OF BOVINE SOMATOTROPIN FOR 2 CONSECUTIVE LACTATIONS AND ITS EFFECTS ON LACTATIONAL PERFORMANCE, HEALTH, AND REPRODUCTION, Journal of dairy science, 77(1), 1994, pp. 94-110
In a two-lactation study, 352 Holstein cows (124 primiparous) from six
commercial dairy herds were assigned to daily injections of bST. Dosa
ges were 0 (control), 5.15, 10.3, or 16.5 mg/d of bST; injections bega
n 28 to 35 d postpartum. During yr 1, FCM production increased linearl
y as bST dose increased for primiparous and multiparous cows. However,
FCM production for primiparous cows that were retained for yr 2 was n
ot increased by bST, and the increase in FCM for multiparous cows was
only 67% of that observed during yr 1 for doses of 10.3 and 16.5 mg/d.
Milk SCC were not increased with the use of bST during either lactati
on. Days to conception of multiparous cows during yr 1 tended to incre
ase linearly with increasing dose. Multiparous cows administered bST d
uring yr 2 tended to have a lower conception rate than control cows (7
1 vs. 87%, respectively). Body condition was decreased linearly by bST
dose at the end of yr 1 and 2. Prior to receiving bST during yr 2, bS
T-treated cows regained less body condition than control cows. Number
of health disorders at parturition and assisted births of cows that re
ceived bST during yr 1 were unaffected by previous treatment. General
health, ratio of single to multiple births, and BW gain of calves was
similar among treatments.