Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 18, 1998
Publication Date: N/A
Interpretive Summary: Feeding during pregnancy has been identified as a principle cost in the production of lamb and beef. Female ruminants require specific nutrients to optimize feed efficiency during pregnancy; however, little is known about the nutrients that are required and how much of each is needed. In this study the effect of pregnancy on the transport of nutrients across the estomach-intestinal complex was measured. Nutrients required for the growt of the fetus are not readily available from the nutrients absorbed from the stomach and intestines of the female. In order to supply the nutrients required for fetal growth, the maternal liver converts metabolites not used in fetal growth to nutrients available for fetal growth. In the this study the role of the liver in the conversion of nutrients during the different stages of pregnancy were measured. This study has identified some of the metabolic events that result in the increase in nutrient requirements of the ewe during pregnancy.
Technical Abstract: It was the objective of this study to determine the pattern of nutrient flux across the portal-drained viscera (PDV) and liver during pregnancy. Catheters were placed in the hepatic portal vein, a branch of the hepatic vein, a mesenteric vein, and the abdominal aorta of ewes. Blood flow and net nutrient release across the PDV and liver were determined prior to exposure to rams. Ewes were subsequently bred resulting in two ewes not being pregnant, six ewes having singles, and 11 ewes having twins. Additional measurements were taken 103, 82, 61, 39, 19, and 6 d before parturition. Net PDV glucose release did not differ from zero. Net hepatic glucose release tended to be higher in pregnant ewes than in nonpregnant ewes (P = .08). Net PDV lactate release did not differ with litter size (P = .58) or days from parturition. Net lactate uptake by the liver increased in pregnant ewes as the pregnancy progressed (P < .001). The hepatic extraction ratio for lactate increased in late pregnancy (P = .02). Net PDV and hepatic release of acetate, propionate, 2-methyl- propionate, and valerate were not different with litter size or days from parturition. Hepatic extraction ratios of volatile-fatty acids did not differ with litter size or day from parturition. The patterns of change in hepatic metabolite fluxes are similar to the patterns of change in gravid uterus metabolite uptake. Hepatic lactate uptake appears to be regulated during pregnancy.