TY - JOUR
T1 - Effects of Altering the Energy and Protein Supply to Dairy Cows During the Dry Period. 2
T2 - Metabolic and Hormonal Responses
AU - Moorby, Jon
AU - Dewhurst, Richard J.
AU - Tweed, John
AU - Dhanoa, M. S.
AU - Beck, Neil
N1 - Funding Information:
This work was funded by the Ministry of Agriculture, Fisheries and Food. The authors gratefully acknowledge the help of R. T. Evans and his staff for the care of animals, J. E. Cockburn, and the staff of the Ruminant Nutrition laboratory for the analysis of samples, and B. Davies at the University of Wales, Aberystwyth, for the hormone analyses.
PY - 2000/8
Y1 - 2000/8
N2 - We offered 48 multiparous Holstein-Friesian cows one of three different dry-period diets for 6 wk before predicted calving: A) a grass silage and barley straw mix (60:40 on a dry-matter basis), with a low protein content; B) grass silage only (medium protein); or C) grass silage plus 0.5 kg of high protein corn gluten meal (high protein)/d. A standard grass silage-based diet was offered to all cows following calving. All animals were blood sampled at weekly intervals during the dry period, and at wk 1, 3, 5, 7, 13, 17, and 21 of lactation. Nitrogen balance was measured in a subset of 12 cows (four per treatment) at 3 wk before calving, and at wk 8 and 18 of lactation. Nitrogen balance in the dry period increased significantly as dietary protein supply increased [9, 34, and 50 g of N/d (SED 8.8) for the three diets, respectively]. We measured no residual effects of dry-period treatment on N balance during lactation. Plasma concentrations of growth hormone became significantly higher in the late dry period in cows offered the silage and straw diet, although treatment differences disappeared after calving. Insulin concentrations were significantly affected by treatment throughout the dry period and indicated inadequate nutrient supplies from the low protein diet, leading to losses in body reserves of energy and protein. The results indicate that animals offered the low protein diet accumulated less N per day than is required for fetal development, suggesting that protein must have been repartitioned from maternal tissues.
AB - We offered 48 multiparous Holstein-Friesian cows one of three different dry-period diets for 6 wk before predicted calving: A) a grass silage and barley straw mix (60:40 on a dry-matter basis), with a low protein content; B) grass silage only (medium protein); or C) grass silage plus 0.5 kg of high protein corn gluten meal (high protein)/d. A standard grass silage-based diet was offered to all cows following calving. All animals were blood sampled at weekly intervals during the dry period, and at wk 1, 3, 5, 7, 13, 17, and 21 of lactation. Nitrogen balance was measured in a subset of 12 cows (four per treatment) at 3 wk before calving, and at wk 8 and 18 of lactation. Nitrogen balance in the dry period increased significantly as dietary protein supply increased [9, 34, and 50 g of N/d (SED 8.8) for the three diets, respectively]. We measured no residual effects of dry-period treatment on N balance during lactation. Plasma concentrations of growth hormone became significantly higher in the late dry period in cows offered the silage and straw diet, although treatment differences disappeared after calving. Insulin concentrations were significantly affected by treatment throughout the dry period and indicated inadequate nutrient supplies from the low protein diet, leading to losses in body reserves of energy and protein. The results indicate that animals offered the low protein diet accumulated less N per day than is required for fetal development, suggesting that protein must have been repartitioned from maternal tissues.
KW - Dairy cows
KW - Dry period
KW - Nitrogen balance
UR - http://www.scopus.com/inward/record.url?scp=0034243418&partnerID=8YFLogxK
U2 - 10.3168/jds.S0022-0302(00)75050-8
DO - 10.3168/jds.S0022-0302(00)75050-8
M3 - Article
SN - 0022-0302
VL - 83
SP - 1795
EP - 1805
JO - Journal of Dairy Science
JF - Journal of Dairy Science
IS - 8
ER -