- Supplementation of two graded levels of DL-Met or liquid MHA-FA to a Met-deficient diet significantly improved pig performance during phase 1 and 2 of the study. Compared with MHA-FA, the inclusions of DL-Met seemed to produce a more homogeneous weight gain.
- The overall growth performance during the 37-day study was not different among the two corresponding Met-supplemented groups, indicating that 100 parts of liquid MHA-FA can be replaced with 65 parts of DL-Met without affecting growth performance under these commercial conditions.
Introduction and Objectives
In swine diets based on cereal grains and oilseed meals, Met is usually the 3rd limiting AA. The DL-Met (99% pure) and liquid methionine hydroxy analogue (MHA-FA, 88%) are the commonly used sources of supplemental Met but there has been considerable debate about the bioefficacy value of MHA-FA relative to DL-Met. Based on the results of growth and N-balance studies, Kim et al. (2006) recently determined a mean bioefficacy of MHA-FA relative to DL-Met to be 64% on a product basis. The bioefficacy values of MHA-FA derived from research trials should be tested under commercial conditions to be more applicable for the local pig producers. Therefore, the objective of this study was to test if 65 parts of DL-Met can replace 100 parts of MHA-FA added to a Met-deficient diet for supporting pig performance during 3 starter phases (6-25 kg BW) under commercial conditions. The experiment was conducted at a 3000-sow commercial farm located in the state of Jalisco, Mexico by O. Santos and colleagues from the National University of Mexico UNAM.
A total of 150 crossbred (Landrace x Yorkshire) mixed-sex pigs, with average initial BW of 6.5 ± 0.5 kg (21 ± 1 d of age), were used in this study. Three Met-deficient basal diets for 3 corresponding phases, containing adequate ME and other essential nutrients except Met + Cys (NRC, 1998), were supplemented with two graded levels DL-Met or MHA-FA on a weight basis at DL-Met to MHA-FA ratio of 65:100 (Tables 1-3).
Pigs were blocked by initial BW and randomly allotted to 5 treatments (Table 1) with 6 replicate pens per treatment during a 37-day experimental period. Pigs were housed in groups of 5 pigs per pen with slatted plastic flooring in a temperature controlled (25 to 28 ºC) facility. Pigs had free access to feed and water. A phase feeding program was applied which consisted of 3 phases: Phase 1 (6-8 kg; d 1-8), Phase 2 (8-12 kg; d 9-17), and Phase 3 (12-25 kg; d 18-37). Individual BW and feed disappearance were recorded at the initiation and termination of each phase to calculate weight gain (ADG), feed intake (ADFI), and feed conversion ratio (FCR). All data were statistically analyzed as a completely randomized design using GLM procedures of SAS. Differences were considered significant if p<0.05 and described as tendencies if 0.05<p<0.10. The pen was used as the experimental unit.
The performance results of pigs during phase 1, 2 and 3 are summarized in Table 4 and illustrated in Figure 1, 2 and 3. The average initial and final BW of the pigs was 6.3 and 24.1 kg, respectively.
Phase 1: The final BW and ADFI were not different among the experimental treatments. Graded levels of Met addition, regardless of Met sources, significantly improved (p<0.05) ADG and FCR, indicating that the basal diet was clearly Met-deficient, and dose response was tested within the sensitive level. No differences were observed among Met-supplemented groups.
Phase 2: The final BW tended to increase (p<0.10) only by DL-Met addition at 0.042% inclusion level. A significant improvement (p<0.05) in FCR and a tendency to increase (p<0.10) ADG of pigs fed diets supplemented with DL-Met additions at both 0.042 and 0.084% and with MHA-FA only at higher level (0.129%) was observed.
Phase 3: The ADG was not significantly different among the basal and the Met-supplemented diets but the final BW of pigs at the end of phase 3 was 1.4 kg heavier (p<0.10) for DL-Met addition at 0.022% inclusion level. The lower level of DL-Met or MHA-FA addition increased (p<0.05) the ADFI which consequently tended to make the FCR less efficient (p<0.10). Only addition of DL-Met at higher level (0.044%) was able to maintain the FCR at the same level of the control pigs during phase 3.
The results of this study indicate that Met addition was essential to maintain optimal pig performance. Overall, no significant differences occurred between DL-Met and MHA-FA within the two graded levels for any of the performance parameters measured at DL-Met to MHA-FA ratio of 65:100. Under these commercial conditions, inclusions of MHA-FA seemed to produce a less homogeneous body weight gain of pigs, e.g. ADG was increased in phase 2, but was decreased in phase 1 and phase 3 by the higher level of MHA-FA supplementation.