Influence of breed and diet on growth, nutrient digestibility, body composition and plasma hormones of Brangus and Angus steers.
Two split-plot designed experiments were conducted to determine the effects of breed (Angus, A, or Brangus, B) and diet (fescue hay, FH; corn silage, CS; or concentrate) on composition and rate of growth, diet digestibility and plasma hormones of steers. In Exp. 1, 10 steers (five of each breed) were fed a CS-based diet followed by a FH-based diet for two consecutive 60-d periods. Both breeds had lower (P less than .01) DM intake and digestibility when fed FH than when fed CS diets. The B steers had higher (P less than .01) plasma insulin concentrations than A steers when fed the CS diet. In Exp. 2, during two consecutive years, 10 steers previously fed CS- and FH-based diets were finished with a corn silage-whole shelled corn-based diet. During yr 1, A steers had higher (P less than .01) DM intake and plasma triiodothyronine (T3) and thyroxine (T4) concentrations (P less than .05) than B steers did. Although final weights were similar (P greater than .10), A steers had heavier (P less than .05) carcass weights than B steers did. During yr 2, A steers had higher (P less than .07) DM and starch digestibilities and higher (P less than .01) plasma T4 concentrations than B steers did. The greater (P less than .01) energetic efficiency of A steers was attributed to the greater rates of fat deposition during yr 2. Regardless of type of diet fed, A steers were more efficient at depositing energy. Higher circulating T4 concentrations of A than B steers may explain some of the physiological differences between these breeds.
Beaver
E E
EE
University of Missouri, Columbia 65211.
Williams
J E
JE
Miller
S J
SJ
Hancock
D L
DL
Hannah
S M
SM
O'Connor
D L
DL
D000821:Animal Feed; D000818:Animals; D001835:Body Weight; D001947:Breeding; D002417:Cattle / Q000097:blood / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D004032:Diet; D004063:Digestion; D004435:Eating; D007328:Insulin / Q000097:blood; D008297:Male; D006109:Poaceae; D012820:Silage; D013213:Starch / Q000378:metabolism; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D003313:Zea mays
D007328:Insulin; D014284:Triiodothyronine; D013213:Starch; D013974:Thyroxine