Carry-over effects of dietary crude protein and triiodothyronine (T3) in broiler chickens.
Indian River male broiler chickens growing from 7 to 30 d of age were fed on diets containing crude protein levels ranging from 120 to 300 g/kg plus 0 or 1 mg triiodothyronine (T3)/kg diet. The purpose of this study was to examine the effects of these treatments on lipogenesis after a common diet was fed (180 g crude protein/kg diet from 30 to 56 d of age). Dietary treatment groups were sampled at 30 and 56 d. In vitro lipogenesis was determined by incubating liver explants for 2 h at 37 degrees in Hanks' salts containing 25 mM-HEPES and 10 mM-[2-14C]acetate and then measuring acetate incorporation into total lipid. Growth and feed consumption from 7 to 30 d increased (P < 0.01) as dietary protein increased from 120 to 210 g/kg diet. Both measurements decreased as crude protein increased from 210 to 300 g/kg diet. T3 decreased (P < 0.01) growth and feed intake during this period. Low-protein (< 180 g/kg) diets increased (P < 0.05) and T3 decreased lipogenesis in 30-d-old chickens. Although birds given T3 from 7 to 30 d grew at the greatest rate from 30 to 56 d of age, the final body weight was still less than controls. In vitro lipogenesis at 56 d of age was not affected by either of the two dietary treatments. In contrast, the relative size of the abdominal fat pad (g/kg body weight) at 56 d was decreased by feeding T3 from 7 to 30 d. Any changes in metabolism elicited by either dietary protein levels or hormone treatments may be specific to the particular dosing interval and are not sustained when a common diet is fed during a repletion period.
Rosebrough
R W
RW
United States Department of Agriculture-Agricultural Research Service, Beltsville, MD 20705, USA.
Mitchell
A D
AD
McMurtry
J P
JP
D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001823:Body Composition; D001835:Body Weight / Q000187:drug effects; D002645:Chickens / Q000254:growth & development / Q000378:metabolism*; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008055:Lipids / Q000096:biosynthesis*; D008071:Lipoprotein Lipase / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood / Q000494:pharmacology*
D004044:Dietary Proteins; D008055:Lipids; D014284:Triiodothyronine; D007334:Insulin-Like Growth Factor I; D008071:Lipoprotein Lipase; D013974:Thyroxine