title: Abomasal nitrogen flow affects the relationship between dietary nitrogen and insulin-like growth factor-I in growing lambs.
abstract: Twelve abomasally cannulated wether lambs were fed isocaloric diets containing 9, 12 or 15% crude protein to determine insulin-like growth factor-I (IGF-I) responses to altered abomasal nitrogen flow and nitrogen status. Lambs were offered 1100 g/d of their respective diets. Voluntary feed consumption was not affected by nitrogen intake. Ruminal and total tract digestibilities of dry matter, organic matter and nitrogen increased linearly (P < 0.05) with increased dietary nitrogen. Abomasal flows of total, bacterial and rumen escape nitrogen increased (linear, P < 0.01), whereas dry matter and organic matter flows decreased (linear, P < 0.01). Total amino acid flow was greater (linear, P < 0.01) in lambs fed additional nitrogen due to increased (linear, P < 0.01) flows of essential and nonessential amino acids. Nitrogen retention and blood urea nitrogen increased linearly (P < 0.01). Serum IGF-I concentrations and relative hybridization intensity of hepatic IGF-I mRNA increased (linear, P < 0.05) as lambs consumed more nitrogen. Serum IGF-I and hepatic IGF-I mRNA were correlated positively (P < 0.05) with nitrogen intake and abomasal flows of nitrogen and various amino acids. These data provide evidence of a relationship between abomasal amino acid flow, as influenced by nitrogen intake, and hepatic gene expression and serum concentrations of IGF-I in growing lambs.
authors.affiliation: Department of Animal and Dairy Sciences, Auburn University, AL 36849, USA.
authors.forename: G M
authors.initials: GM
authors.lastname: Davenport
authors.forename: K A
authors.initials: KA
authors.lastname: Cummins
authors.forename: D R
authors.initials: DR
authors.lastname: Mulvaney
mesh_terms: D000018:Abomasum / Q000378:metabolism*; D000818:Animals; D001806:Blood Urea Nitrogen; D005527:Food, Fortified; D005786:Gene Expression Regulation; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008297:Male; D009584:Nitrogen / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D011897:Random Allocation; D012756:Sheep / Q000254:growth & development* / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D009584:Nitrogen