Multi-farm use of bovine somatotropin for two consecutive lactations and its effects on lactational performance, health, and reproduction.
In a two-lactation study, 352 Holstein cows (124 primiparous) from six commercial dairy herds were assigned to daily injections of bST. Dosages were 0 (control), 5.15, 10.3, or 16.5 mg/d of bST; injections began 28 to 35 d postpartum. During yr 1, FCM production increased linearly as bST dose increased for primiparous and multiparous cows. However, FCM production for primiparous cows that were retained for yr 2 was not 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 lactation. Days to conception of multiparous cows during yr 1 tended to increase linearly with increasing dose. Multiparous cows administered bST during yr 2 tended to have a lower conception rate than control cows (71 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, bST-treated cows regained less body condition than control cows. Number of health disorders at parturition and assisted births of cows that received 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.
Hansen
W P
WP
Department of Animal Science, University of Minnesota, St. Paul 55108.
Otterby
D E
DE
Linn
J G
JG
Anderson
J F
JF
Eggert
R G
RG
D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D002418:Cattle Diseases / Q000453:epidemiology; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology*; D006304:Health Status; D007774:Lactation / Q000187:drug effects*; D008414:Mastitis, Bovine / Q000453:epidemiology; D008892:Milk / Q000737:chemistry; D010298:Parity; D012098:Reproduction / Q000187:drug effects*
D013006:Growth Hormone