Abstract: The objective of this study was to compare the biological effectiveness of liquid methionine hydroxy analog free acid (MHA-FA) relative to DL-methionine for growing pigs. Two N-balance trials were conducted using a total of 42 barrows (Large White x Landrace). The initial body weight was 11.73�1.05 kg in the first trial and 13.69�À1.48 kg in the second. In each trial, 21 pigs were randomly assigned to one of seven dietary treatments with three observations per treatment. The diets included a methionine-deficient basal diet with all other essential nutrients meeting the pig�s requirements and six diets formulated with graded levels of DL-methionine (0.03, 0.06 and 0.09%) or MHA-FA (0.034, 0.068 and 0.102%) added on an equimolar basis. Each trial lasted 12 days, consisting of an adaptation period of 7 days followed by a 5-day total collection of urine and feces. During the collection period, pigs were fed (630 g d 1 for the first trial and 669 g/d for the second) three times (0800, 1500, and 2200 h) daily. Pigs had ad libitum access to water after feeding. Pigs receiving the experimental diets achieved higher daily gain and lower feed conversion than those receiving the basal diet. At each inclusion level, the treatment with added DL-methionine was superior to the corresponding treatment with added MHA-FA. The concentration of plasma urea nitrogen for pigs receiving the supplemental methionine sources, regardless of form, was lower than that for pigs receiving the basal diet. For each treatment, N retention and percentage of N retained were higher and urinary N production was lower than that of the basal diet. N retention in the experimental diets increased as the level of methionine equivalents increased. Additionally, at each inclusion rate, all treatments with DL-methionine supplementation showed a higher N retention but a lower plasma urea nitrogen concentration than the corresponding treatments with MHA-FA. An exponential model was used to determine the bioefficacy of MHA-FA relative to DL-methionine, and this model was a good fit for the responses. MHA-FA was estimated to be 73.2% as effective as DL-methionine for N retention and 45.6% for plasma urea nitrogen on an equimolar basis.
Zhanyu Feng , Shiyan Qiao , Yongxi Ma , Xu Wang , Xiaojie Li and P.A. Thacker , 2006. Efficacy of Methionine Hydroxy Analog and Dl-methionine as Methionine Sources for Growing Pigs. Journal of Animal and Veterinary Advances, 5: 135-142.