Effects of Bovine Somatotropin on Milk Yield and Composition, Body Weight, and Condition Score of Holstein and Jersey Cows J. W. WEST,1 K. 8ONDARI,2 and J. C. JOHNSON, JR.1 University of Georgia Coastal Plain Station Tifton 31793 ABSTRACT
extracts increased milk yield in dairy cows, stimulating interest in somatotropin. However, Fony cows (20 Holstein, 20 Jersey) limited quantities of native pituitary somatotrowere administered 0, 5, 10, 15, or 20 mg pin made field application impractical. Shortof recombinantly derived bST daily to tenn studies with pituitary-derived bovine sodetennine the effect on milk yield, milk matotropin (pbST) demonstrated that pbST composition, body weight, and body constimulated greater milk yield (17, 22), that the dition score. Administration of bST was effect was dose-responsive (11), the response from 75 ± 7 d through 305 d postpartum. occurred with different means of administration A total mixed diet of 45% com silage and (13, 14), and that improved milk yield occurred 55% of a concentrate mixture (dry basis) in both early or late lactation (19). The advent was provided for ad libitum intake. Milk of recombinant DNA technology (15) allowed yield of Holstein and Jersey cows adminproduction of relatively large quantities of synistered 20 mg of bST increased 25.3 and thetic bovine somatotropin (bST). In long-term 22.8%, respectively, over controls. Fatstudies with bST, greater milk yield (3, 9, 24) corrected milk from Holsteins and Jerseys has been observed. Although significant, feed that were administered 20 mg of somatoand energy intake did not increase to the extent tropin increased 32.2 and 18.7% over of milk yield, resulting in improved gross efficontrols, but Jersey response was greatest ciency of production (3, 9, 24). Although gross when 15 mg of bST were administered efficiency of milk production was improved by (27.1 % over controls). Dry matter intake bST, the increase in milk energy yield was not of the 20 mg bST group was 13.5% the result of improved partial efficiency of metgreater than DM intake of controls. Apparent efficiency of production increased abolic processes (25) or increased digestibility linearly with increasing somatotropin. of the diet (17, 20). These results indicate that a There was no significant change in body redirection of nuO'ients from tissues must occur weight, but body condition score declined to support greater milk yield. Final body weight linearly with increasing somatotropin. and rate of gain was not changed by bST Most milk composition measures were administration (3, 9, 20); however, body condiunaffected by somatotropin. Jersey and tion score declined with bST administration Holstein milk yield increased quadrati(20, 24). Empty body fat and body condition cally and linearly, respectively, with soscore in one study (24) declined with increasing matotropin dose. bST dose, but body weight was unchanged, (Key words: bovine somatotropin, lactaindicating that body weight change may be a tion, dairy cows) poor indicator of body energy status. Tyrrell et al. (25) reported that administration of bST to INTRODUCTION lactating cows resulted in greater negative tisEarly studies by Asimov and Krouze (1) sue nitrogen and energy balance. Objectives of this study were: 1) to deterdemonsO'ated that injections of crude pituitary mine the effect of bST on milk yield, milk composition, and DM intake, 2) to detennine if changes in body weight and body condition Received March 22, 1989. score were dose related, and 3) to determine if Accepted Oclober 12.1989. treatment response was different among Hol1Depanmenl of Animal Science. stein and Jersey cows. 2S t atistical and Computer Services. 1990 J Dairy Sci 73:1062-1068
1062
1063
SOMATOTROPIN USE IN HOLSTEIN AND JERSEY COWS
MATERIALS AND METHODS
Twenty lactating Holstein cows (5 primiparous, 15 multiparous) and 20 lactating Jersey cows (10 primiparous, 10 multiparous) were ranked by milk production during a 14-
extracts increased milk yield in dairy cows, stimulating interest in somatotropin. However, Fony cows (20 Holstein, 20 Jersey) limited quantities of native pituitary somatotrowere administered 0, 5, 10, 15, or 20 mg pin made field application impractical. Shortof recombinantly derived bST daily to tenn studies with pituitary-derived bovine sodetennine the effect on milk yield, milk matotropin (pbST) demonstrated that pbST composition, body weight, and body constimulated greater milk yield (17, 22), that the dition score. Administration of bST was effect was dose-responsive (11), the response from 75 ± 7 d through 305 d postpartum. occurred with different means of administration A total mixed diet of 45% com silage and (13, 14), and that improved milk yield occurred 55% of a concentrate mixture (dry basis) in both early or late lactation (19). The advent was provided for ad libitum intake. Milk of recombinant DNA technology (15) allowed yield of Holstein and Jersey cows adminproduction of relatively large quantities of synistered 20 mg of bST increased 25.3 and thetic bovine somatotropin (bST). In long-term 22.8%, respectively, over controls. Fatstudies with bST, greater milk yield (3, 9, 24) corrected milk from Holsteins and Jerseys has been observed. Although significant, feed that were administered 20 mg of somatoand energy intake did not increase to the extent tropin increased 32.2 and 18.7% over of milk yield, resulting in improved gross efficontrols, but Jersey response was greatest ciency of production (3, 9, 24). Although gross when 15 mg of bST were administered efficiency of milk production was improved by (27.1 % over controls). Dry matter intake bST, the increase in milk energy yield was not of the 20 mg bST group was 13.5% the result of improved partial efficiency of metgreater than DM intake of controls. Apparent efficiency of production increased abolic processes (25) or increased digestibility linearly with increasing somatotropin. of the diet (17, 20). These results indicate that a There was no significant change in body redirection of nuO'ients from tissues must occur weight, but body condition score declined to support greater milk yield. Final body weight linearly with increasing somatotropin. and rate of gain was not changed by bST Most milk composition measures were administration (3, 9, 20); however, body condiunaffected by somatotropin. Jersey and tion score declined with bST administration Holstein milk yield increased quadrati(20, 24). Empty body fat and body condition cally and linearly, respectively, with soscore in one study (24) declined with increasing matotropin dose. bST dose, but body weight was unchanged, (Key words: bovine somatotropin, lactaindicating that body weight change may be a tion, dairy cows) poor indicator of body energy status. Tyrrell et al. (25) reported that administration of bST to INTRODUCTION lactating cows resulted in greater negative tisEarly studies by Asimov and Krouze (1) sue nitrogen and energy balance. Objectives of this study were: 1) to deterdemonsO'ated that injections of crude pituitary mine the effect of bST on milk yield, milk composition, and DM intake, 2) to detennine if changes in body weight and body condition Received March 22, 1989. score were dose related, and 3) to determine if Accepted Oclober 12.1989. treatment response was different among Hol1Depanmenl of Animal Science. stein and Jersey cows. 2S t atistical and Computer Services. 1990 J Dairy Sci 73:1062-1068
1062
1063
SOMATOTROPIN USE IN HOLSTEIN AND JERSEY COWS
MATERIALS AND METHODS
Twenty lactating Holstein cows (5 primiparous, 15 multiparous) and 20 lactating Jersey cows (10 primiparous, 10 multiparous) were ranked by milk production during a 14-
