|Moallem, U - UNIVERSITY OF MARYLAND|
|Dahl, G - UNIVERSITY OF MARYLAND|
|Erdman, R - UNIVERSITY OF MARYLAND|
Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: March 8, 2001
Publication Date: July 15, 2001
Citation: MOALLEM, U., DAHL, G.E., CAPUCO, A.V., BALDWIN, R.L., ERDMAN, R.A. EFFECTS OF ADDED RUMEN UNDEGRADED PROTEIN AND BOVINE SOMATOTROPIN ADMINISTRATION ON ORGAN AND TISSUE WEIGHTS IN PREPUBRTAL DIARY HEIFERS. JOINT ABSTRACTS OF THE AMERICAN DAIRY SCIENCE AND SOCIETY OF ANIMAL SCIENCE. 2001. Technical Abstract: Twenty-four dairy heifers were used to determine effects of added rumen undegraded protein (RUP) and bST administration from 3 to 10 mo of age on organ and tissue weights. Heifers (90 d of age) were blocked randomly into 2X2 factorial trial, consisting of added dietary RUP (+2%, DM basis) and 0.1mg/kg BW per day of bST. Twelve heifers, 3 per group, were slaughtered at 5 mo of age and twelve at 10 mo of age. Weights were obtained for rumen and intestinal tract components, liver, heart, lungs, spleen and other organs at the time of slaughter. Body weight at 90 d of age was used as a covariate in the statistical analysis. At 5 mo, bST increased average liver weight by 28.4% compared to Controls and when expressed as a fraction of empty body weight (EBW) by 10% (P < 0.05). Rumen undegraded protein increased the empty rumen + reticulum and abomasum weights by 24.4% and 11.5%, and as a fraction of EBW by 16% (P < 0.01) and 6% (P < 0.10) compared with controls. Rumen digesta fill was increased by 27.3% by added RUP (P < 0.05). Enlargement of the anterior digestive tract is consistent with the 10% increased DMI observed in the RUP group. At 10 mo of age, bST increased weights of heart (28%, P < 0.01), kidney (22.3%, P < 0.01) and liver (17%, NS), and as the relative part of EBW by 15% (P < 0.05), 10% (NS), and 5% (NS). In addition, at 10 mo, omasum, small and large intestine were increased by 22.3%, 22.1% and 22.3%, respectively, by bST. Administration of bST to growing heifers altered relative organ growth, in a manner that supports increased metabolic activity associated with partitioning of nutrients toward increased protein deposition. By comparison, RUP effects were shown only through increased mass of the digestive tract and digesta fill.