An experiment was conducted to determine the effect of high dietary intakes of Zn and Cu and their combination on growth performance of weanling pigs with diverse health status and management strategies. Twelve experiment stations cooperated and used a total of 1,356 pigs that averaged 6.55 kg BW and 22.2 d age at weaning. The four dietary treatments, all of which met or exceeded NRC requirements, were 1) control, 2) 3,000 ppm Zn (from Zn oxide), 3) 250 Cu ppm (from Cu sulfate), or 4) 3,000 ppm Zn and 250 ppm Cu. The diets were fed as a complex Phase I diet (1.4% lysine) for 7 d followed by a Phase II diet (1.2% lysine) for 21 d. Chlortetracycline (220 ppm) was added to all diets. Fecal color (1 = yellow to 5 = black) and consistency (1 = very firm to 5 = very watery) were scored daily for 3 wk. At the end of the 28-d study, 412 pigs were bled at five stations, and plasma Cu, Zn, and Fe concentrations were determined at one station with atomic absorption spectrophotometry. Average daily gain (375, 422, 409, 415 g/d), feed intake (637, 690, 671, 681 g/d), and gain/feed (586, 611, 611, 612 g/kg) were improved (P < .01) by the addition of Zn and(or) Cu. Significant Cu x Zn interactions imply that the responses to Zn and Cu were independent and not additive. There were significant (P < .01) Zn and Cu effects and a Zn x Cu interaction on fecal color (3.17, 3.24, 4.32, 3.57) and consistency (2.39, 2.14, 2.14, 2.13). Dietary additions of Cu and Zn resulted in elevated plasma concentrations of Cu and Zn, respectively. These data indicate that pharmacological additions of 3,000 ppm Zn (oxide) or 250 ppm Cu (sulfate) stimulate growth beyond that derived from intakes of Zn and Cu that meet nutrient requirements. However, the combination of Zn and Cu did not result in an additive growth response.

Twelve organic Mn sources and MnSO4 were evaluated by polarographic analysis and via solubility in buffers (pH 5 and 2) and deionized water. Fractions from solubility tests were evaluated by gel filtration chromatography for structural integrity. Organic Mn sources included five Mn methionine complexes (Mn Met A to Mn Met E), two Mn proteinates (Mn Pro A and Mn Pro B), and five Mn amino acids (Mn AA A to Mn AA E). Sources varied considerably in chemical characteristics. Chelation strength (Qf) ranged from weak (1.9 Qf-values) to strong complexes (115.4 Qf-values). No complexed Mn was found in filtrates at pH 2.0 or 5.0. A 42-d bioassay was used to estimate relative bioavailability of Mn sources for chicks fed diets supplemented with 60, 120, or 180 mg Mn/kg. Bone Mn, heart Mn, heart manganese-superoxide dismutase activity (MnSOD), and heart MnSOD mRNA increased (P < 0.001) as dietary Mn increased. Only heart MnSOD mRNA tended (P < 0.10) to differ among dietary Mn sources. For bioassays of Mn, the MnSOD mRNA level in heart was more sensitive than the MnSOD activity in heart or other indices. Relative to MnSO4 (assigned 100%), slope ratios of MnSOD mRNA levels in heart gave bioavailabilities of 99, 132, and 113% for Mn Met E, Mn AA B, and Mn AA C sources with weak, moderate, and strong chelation strength, respectively. The bioavailability of Mn was more closely related to chelation strength as measured by polarography than to chemical traits assessed by solubility or structural integrity.

A cooperative research study involving three experiments and 2,318 pigs was conducted at 12 research stations to evaluate the protein (lysine) requirements of barrows and gilts. The two sexes were penned separately and fed fortified corn-soybean meal diets containing protein levels ranging from 12.0 to 17.2%. Lysine levels in these diets ranged from .52 to .90%. Protein levels in Exp. 1 were 12, 14, and 16%; in Exp. 2, protein levels were 13, 14, 15, and 16%; and in Exp. 3, they were 13.2 15.2, and 17.2%. Fat (5%) was added to one-half of the diets in Exp. 3. Each station that participated contributed a minimum of two replicate pens of pigs per diet-sex combination in a given experiment. Average initial and final weights were 35 and 99 kg in Exp. 1 and 51 and 105 kg in Exp. 2 and 3, respectively. At the end of the test period, pigs were slaughtered and hot carcass weight, 10th rib fat depth, and longissimus muscle area were measured. Percentage of carcass muscle was estimated from these data. Overall, barrows gained weight faster than gilts (P < .01), but gilts required less feed per unit of gain (P < .05) and had less backfat, larger longissimus muscle areas, and a greater percentage of carcass muscle (P < .01) than did barrows. Lean growth rate was similar for barrows and gilts (332 vs 329 g/d). Increasing the dietary protein or lysine level resulted in improved rate and efficiency of gain and increased carcass leanness and lean growth rate in gilts, but the increase was less pronounced or did not occur in barrows, resulting in protein level x sex interactions. Feeding low-protein (12 or 13%) diets decreased performance and carcass leanness to a greater extent in gilts than in barrows. The pooled data from the three experiments indicated that most traits tended to reach a plateau at 13% CP (.60% lysine) in barrows, whereas in gilts, weight gains, feed/gain, carcass muscle, and lean growth rate continued to improve, but at a decreasing rate, with up to 17.2% CP (.90% lysine). The results indicate that gilts require higher concentrations of dietary amino acids to maximize lean growth rate than do barrows.

No abstract

Two 28-d randomized complete block design experiments were conducted to evaluate the effects of concentrations and sources of Zn on growth performance of nursery pigs. Seven stations participated in Exp. 1, which evaluated the efficacy of replacing 2,500 ppm of Zn from ZnO with 125, 250, or 500 ppm of Zn from Zn methionine. A control diet with 125 ppm of supplemental Zn was included at all stations. A total of 615 pigs were used in 26 replicates. Average weaning age was 20.6 d and the average initial BW was 6.3 kg. There were no differences in any growth response among the three supplemental Zn methionine levels fed in Exp. 1. Zinc supplementation from Zn methionine improved ADG compared with the control during all phases (P < 0.05), due primarily to an increase in ADFI. Pigs fed 2,500 ppm of Zn from ZnO gained faster (P < 0.01) than those fed the control diet during all phases, and faster (P < 0.05) than those fed supplemental Zn from Zn methionine for the 28-d experiment. Differences in gain were again due mainly to differences in feed intake. A second experiment compared five sources of supplemental organic Zn (500 ppm of Zn) with 500 and 2,000 ppm supplemental Zn from ZnO and a control (140 ppm total Zn). Six stations used a total of 624 pigs, with an average weaning age of 20.4 d and averaging 6.2 kg BW in 15 replicates. Pigs fed 2,000 ppm of Zn from ZnO gained faster (P < 0.05) than pigs fed the control or any of the 500 ppm of Zn treatments (ZnO or organic Zn). Pigs fed the 2,000 ppm of Zn from ZnO also consumed more feed than those receiving 500 ppm of Zn from ZnO or from any of the organic Zn sources (P < 0.05). Organic sources of Zn did not improve gain, feed intake, or feed efficiency beyond that achieved with the control diet. Supplemental Zn at a concentration of 500 ppm, whether in the form of the oxide or in an organic form, was not as efficacious for improved ADG as 2,000 to 2,500 ppm of Zn from ZnO.