Overall efficacy of chronically administered recombinant bovine somatotropin to lactating dairy cows.
Recombinant bST at daily dosages of 0, 10.3, 20.6, and 41.2 mg/d were injected for 266 d into 8, 10, 9, and 9 Holstein cows, respectively. Treatment effects of recombinant bST were assessed for milk production traits, BW, blood components, and health and reproductive variables. Data reported compare controls to all bST-treated cows. There was an average increase of 18% in 3.5% FCM for bST versus control cows. This increase resulted in enhanced feed efficiency for bST cows, as their DM intakes were not elevated above those of the control cows. Recovery of BW was similar between control and bST groups. Milk composition was unaffected except for a slight decrease in protein percentage during the first 9 wk of treatment, and an elevated SCC between wk 19 and 28. Blood parameters were not different between control and bST cows, except for hematocrit, which decreased with bST treatment. The only health and reproductive parameters affected by bST were mastitis and days open, which were increased in the highest dosage groups.
Burton
J H
JH
Department of Animal and Poultry Science, University of Guelph, Ontario, Canada.
MacLeod
G K
GK
McBride
B W
BW
Burton
J L
JL
Bateman
K
K
McMillan
I
I
Eggert
R G
RG
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002417:Cattle / Q000502:physiology*; D002418:Cattle Diseases / Q000139:chemically induced; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D005260:Female; D013006:Growth Hormone / Q000009:adverse effects / Q000494:pharmacology*; D007774:Lactation / Q000187:drug effects*; D008414:Mastitis, Bovine / Q000139:chemically induced; D008892:Milk / Q000737:chemistry / Q000187:drug effects; D008894:Milk Proteins / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D012098:Reproduction / Q000187:drug effects
D008894:Milk Proteins; D011994:Recombinant Proteins; D013006:Growth Hormone