אסיף מאגר המחקר החקלאי

Effect of bovine somatotropin and rumen-undegradable protein on mammary growth of prepubertal dairy heifers and subsequent milk production

Year:

2004

Source of publication :

Authors :

Volume :

87

Co-Authors:

Capuco, A.V., Bovine Funct. Genomics Laboratory, Anim. and Nat. Resources Institute, USDA-ARS, Beltsville, MD 20705, United States
Dahl, G.E., Dept. of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, United States, Department of Animal Sciences, University of Illinois, Urbana, IL 61801-4734, United States
Wood, D.L., Bovine Funct. Genomics Laboratory, Anim. and Nat. Resources Institute, USDA-ARS, Beltsville, MD 20705, United States
Moallem, U., Dept. of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, United States, Department of Dairy Cattle, Institute of Animal Science, Volcani Center, Bet-Dagan, 50250, Israel
Erdman, R.E., Dept. of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, United States

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Abstract:

Rapid body growth during the prepubertal period may be associated with reductions in mammary parenchymal growth and subsequent milk yield. The objective of this study was to test effects of dietary rumen-undegradable protein (RUP) and administration of recombinant bovine somatotropin (bST) during the prepubertal period on mammary growth and milk yield of dairy heifers. Seventy-two Holstein heifers were used in the experiment. At 90 d of age, 8 heifers were slaughtered before initiation of treatment. Remaining heifers were assigned randomly to 1 of 4 treatments. Treatments consisted of a control diet (5.9% RUP, 14.9% CP, DM basis) or RUP-supplemented diet (control diet plus 2% added RUP) with or without 0.1 mg of bST/kg of BW per day applied in a 2 x 2 factorial design. A total of 6 heifers per treatment (3 each at 5 and 10 mo of age) were slaughtered for mammary tissue analysis. Remaining heifers were bred to evaluate impact of treatment on subsequent milk yield and composition. Mammary parenchymal growth was not affected by RUP or bST treatment. Total parenchymal mass increased from 16 to 364 g, and parenchymal DNA from 58 to 1022 mg from 3 to 10 mo of age, respectively. Furthermore, number of mammary epithelial cells likely was not affected by diet or bST because the epithelial cell proliferation index, assessed by Ki-67 labeling, was not affected by treatment, nor was total parenchymal DNA and lipid content. Neither deleterious effects of increased rates of gain nor positive effects of bST were evident in prepubertal mammary growth. Subsequent milk production and composition was not different among treatments.

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