Sulfur-containing amino acid requirement of rapidly growing steers.
Eight ruminally cannulated steers (294 kg, ADG = 1.3 kg/d) were used in a N retention study (8 x 8 latin-square design) to evaluate sulfur-containing (S) amino acid (AA) requirements for growth. Treatments were abomasal infusions of seven levels of L-methionine (0, 3, 6, 9, 12, 15 and 18 g/d) and one level of DL-methionine (6 g/d). All steers were fed a semipurified diet based on ammoniated corn cobs (DMI = 6.56 kg/d) and were abomasally infused with 400 g/d dextrose and 296.4 g/d of crystalline AA that simulated the non-S-AA pattern of casein. Infusion of 3 g/d supplemental L-methionine maximized N retention in steers. Intestinal flows of absorbable S-AA were determined to be 1.89 g/kg DMI. Breakpoint analysis of retained N as a function of total absorbable S-AA yielded a total S-AA requirement of 14.7 g/d. Nitrogen retention for DL-methionine (36.4 g/d) was not different (P greater than .05) from that for 6 g/d L-methionine (38.8 g/d), but because this value was not in the linear response range, the efficacy of DL-methionine in meeting S-AA needs could not be evaluated. Plasma methionine concentrations increased linearly (P less than .05) in response to L-methionine infusion and were greater (P less than .05) for steers infused with 6 g/d DL-methionine (45.3 microM) than for steers receiving 6 g/d L-methionine (30.5 microM). Plasma cystine increased when up to 9 g/d L-methionine was infused.(ABSTRACT TRUNCATED AT 250 WORDS)
Titgemeyer
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EC
Dept. of Anim. Sci., University of Illinois, Urbana 61801.
Merchen
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NR
D000596:Amino Acids / Q000097:blood; D000603:Amino Acids, Sulfur / Q000378:metabolism*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000254:growth & development / Q000378:metabolism*; D004063:Digestion; D008297:Male; D008715:Methionine / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D015430:Weight Gain
D000596:Amino Acids; D000603:Amino Acids, Sulfur; D008715:Methionine; D009584:Nitrogen