Experiments were conducted to determine the relative bioavailability (RBV) of the calcium salt of the hydroxy analog of DL-methionine (MHA-Ca, 84%) to DL-methionine (DL-Met, 99%) as Met sources fed to pigs. In Exp. 1, 42 crossbred barrows (initial BW of 15.0 ± 0.7 kg) were allotted to 7 treatments in a N-balance study. The basal diet (BD) was formulated to contain 15.4% CP and 0.22% Met (70% of requirement). Diets included 1) BD, 2) BD + 0.025% DL-Met, 3) BD + 0.050% DL-Met, 4) BD + 0.075% DL-Met, 5) BD + 0.038% MHA-Ca, 6) BD + 0.077% MHA-Ca, and 7) BD + 0.115% MHA-Ca. An increase in dietary inclusion rates of both Met sources linearly increased (P < 0.01) N retained (g/d) and N retention (% of intake). Using linear slope-ratio regression, the RBV value of MHA-Ca to DL-Met for N retained (g/d) was 63.0% on a product-to-product basis (75.0% on an equimolar basis). In Exp. 2, 40 crossbred barrows (initial BW of 15.5 ± 1.5 kg) were allotted to 5 treatments in another N-balance study. The BD was formulated to contain 17.0% CP and 0.22% Met (70% of requirement). Diets included 1) BD, 2) BD + 0.030% DL-Met, 3) BD + 0.060% DL-Met, 4) BD + 0.046% MHA-Ca, and 5) BD + 0.092% MHA-Ca. Increasing levels of DL-Met or MHA-Ca increased N retained (g/d) and N retention (% of intake) linearly (P < 0.001) and quadratically (P < 0.05). Using linear slope-ratio regression, a product-to-product RBV value of MHA-Ca to DL-Met was 68.4% (81.4% on an equimolar basis) for N retained (g/d). In Exp. 3, 276 pigs (12 barrow and 11 gilt replicates; initial BW of 7.09 ± 1.1 kg) were used in 3 diet preference studies. Pigs were randomly allotted to 1 of 3 treatment comparisons of feed choice: 1) BD (0.23% Met) or BD + 0.07% DL-Met; 2) BD or BD + 0.0825% MHA-Ca, and 3) BD + 0.07% DL-Met or BD + 0.0825% MHA-Ca. Pigs consumed a higher percentage (55 vs. 45%; P = 0.008) of their total feed intake from the diet supplemented with 0.07% DL-Met in Comparison 1, but a lower percentage (45 vs. 55%; P = 0.003) of their total feed intake from the diet supplemented with 0.0825% MHA-Ca in Comparison 2. There was no diet preference for DL-Met or MHA-Ca in Comparison 3. The observed Met source preference differences occurred in the barrow replicates but not in the gilt replicates. These results demonstrated the mean RBV of MHA-Ca to DL-Met of 65.7% on a product-to-product (wt/wt) basis or 78.2% on an equimolar basis and that a preference for Met sources was observed in barrows but not in gilts.

This study aimed to optimize the ratios of standardized ileal digestible (SID) methionine (Met) plus cystine (Cys), and threonine (Thr) to SID lysine (Lys) in low-protein diets for working boars. Forty-eight working Duroc boars were randomly allocated to one of 12 dietary treatments in a 3x4 factorial experimental design in which factor 1 was the ratios of SID Met plus Cys to SID Lys (50, 60, 70%), factor 2 was the ratios of SID Thr to SID Lys (40, 50, 60, 70%). Semen was collected at a 4 days interval for 6 weeks for 10 ejaculates. Semen volume (V), percentage of sperm with progressive motility (A), sperm concentration (C), and the total number of motile sperm per ejaculate (VAC) were measured. The results of the study revealed that the ratios of SID Met plus Cys to SID Lys in the diets affected the C and VAC. Values of C and VAC were highest at the ratios of SID Met plus Cys to SID Lys of 70% and lowest at 50% (P<0.05). Similarly, the ratios of SID Thr to SID Lys affected the C and VAC. Further, the values of C and VAC were highest at the ratio of SID Thr to SID Lys of 60% and lowest at 40% (P<0.05). There was no interaction effect between the two factors. In conclusion, the ratios of SID Met plus Cys to SID Lys of 70% and SID Thr to SID Lys of 60% in a 13.5% CP diet are optimal for working boars.

The effects of oxidized β-carotene (OxBC) were determined upon the growth performance of swine through their full growth cycle under commercial production conditions in Vietnam. Five hundred 28-day-old-weaned barrows and gilts were used in a 140-day complete wean-to-finish feeding trial. Animals were randomized by weight, and each pen contained 20 pigs with the same ratio of barrows to gilts. There were five dietary treatment groups with five replicate pens per treatment: Control basal diet, no antibiotics or OxBC; Basal diet with antibiotics; no OxBC; Basal diet supplemented with 2, 4, or 8 mg OxBC/kg of diet, no antibiotics. Growth performance parameters were calculated for each production stage (Starter: Days 1–28, Grower: Days 29–84, Finisher: Days 85–140) and for the overall study (Days 1–140). OxBC and antibiotics each improved growth rate, feed efficiency, and body weight compared to the unsupplemented control (p < 0.001). Animals receiving 4 and 8 mg/kg OxBC performed better than animals on antibiotics (p < 0.001). In Starter pigs, OxBC reduced the occurrence of diarrhea dose-dependently (2, 4, and 8 mg/kg) and more so than did antibiotics (p < 0.001). These findings support the concept that oxidized β-carotene can facilitate swine growth and health in the absence of in-feed antibiotics.

The discovery of naturally occurring, biologically active β-carotene-oxygen copolymer compounds in spontaneously oxidized β-carotene has stimulated interest in their potential health benefits. The copolymers, formed in Nature or synthetically by the air-oxidation of β-carotene, possess beneficial immune modulating activities that previously had been attributed to β-carotene itself. Support for these benefits is provided by previous studies showing that supplementation in feed with low parts-per-million levels of copolymer-rich, fully oxidized β-carotene (OxBC) helped reduce the negative impact of subclinical necrotic enteritis in broilers and improved growth in weaned piglets. To further assess these potential benefits, two trials were conducted in swine raised under commercial conditions in Vietnam. Trial 1, a 140-day full-grow, post-wean study with 500 28-day-old pigs, compared 2, 4 or 8 ppm OxBC against both an unsupplemented and an antibiotic control group. OxBC and antibiotics each improved growth rate, feed efficiency, and body weight compared to the control. Animals receiving 4 and 8 ppm OxBC performed better than did animals on antibiotics. In starter pigs, OxBC reduced the occurrence of diarrhea dose-dependently (4 and 8 ppm) and to a greater extent than did antibiotics. Trial 2, a 49-day study with 420 piglets, was conducted in two-stages. In Stage 1 (pre-wean), OxBC in the transition (creep) feed produced a dose-dependent trend toward increased body weight over 21 days, reaching significance at the highest inclusion level (16 ppm). In Stage 2 (post-wean), body weight gain showed a dose-dependent trend and was significant for both 8 ppm OxBC and the antibiotics at 28 days post-wean. Feed conversion was better at 8 ppm OxBC and for the antibiotic group. These findings support the concept that β-carotene-oxygen copolymers help optimize immune function, and provide validation for the effectiveness of this strategy in enhancing animal performance in the absence of in-feed antibiotics.