title: Biological efficacy and absorption of DL-methionine hydroxy analogue free acid compared to DL-methionine in chickens as affected by heat stress.
abstract: 1. The net absorption and the biological efficacy of DL-methionine and of DL-methionine hydroxy analogue free acid (MHA-FA) were evaluated in chickens under heat stress. 2. In a growth assay, finishing broilers 21 to 42 d of age were fed on diets containing graded amounts of the two supplements; the basal diet was composed of practical ingredients. 3. From slope-ratio analysis, equimolar efficacy of MHA-FA relative to DL-methionine was determined to be 83% (confidence limits 61 to 115%) from weight gain responses, and 67% (47 to 91%) from food conversion responses. This indicates that the relative efficacy of MHA-FA is close to previous estimates of about 75% obtained under thermoneutral conditions. 4. In a balance study with caecectomised cockerels, net absorption (intake - excretion in faeces and urine) of DL-methionine and of MHA-FA, respectively, were determined to be 97.2 and 90.8%. The net absorption of MHA-FA was significantly lower than that of DL-methionine.
authors.affiliation: Universidade Federal de Vicosa, Departamento de Zootecnia, Minas Gerais, Brazil.
authors.forename: H S
authors.initials: HS
authors.lastname: Rostagno
authors.forename: W A
authors.initials: WA
authors.lastname: Barbosa
mesh_terms: D000818:Animals; D002645:Chickens / Q000502:physiology*; D016001:Confidence Intervals; D006128:Growth; D006358:Hot Temperature; D007408:Intestinal Absorption; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives / Q000378:metabolism*; D013237:Stereoisomerism; D013312:Stress, Physiological
chemical_list: D008715:Methionine