Three trials were conducted to evaluate high levels of Zn addition from various Zn sources on growth performance and plasma Zn responses of 8-kg pigs. Zinc supplements were added to 20% CP starting diets (125 mg of Zn/kg) containing antibiotics. Trial 1 was done to evaluate plasma Zn responses of pigs fed three different feed-grade Zn sources: ZnO where supplemental Zn levels were 0, 250, 500, 1,000, 3,000, and 5,000 mg/kg; ZnSO4 at 1,500 or 2,500 mg of Zn/kg; and a zinc-lysine complex (Zn-Lys) at 1,500 or 2,500 mg of Zn/kg. Plasma Zn concentration as a function of supplemental Zn intake was fitted to a broken-line for ZnO data and to simple linear models for ZnSO4 and Zn-Lys data. For ZnO, plasma Zn did not increase until concentrations > 1,000 mg Zn/kg were fed. Above this level, plasma Zn increased linearly (P < .01) for all three sources of Zn, although slopes of the ZnO and Zn-Lys response curves were 56% (P < .05) and 110%, respectively, of the ZnSO4 slopes. In Trial 2, five diets were fed: basal, 3,000 and 5,000 mg of Zn/kg from ZnO, and 3,000 and 5,000 mg of Zn/kg from ZnSO4. Daily gain and daily feed intake were increased (P < .05) by ZnO addition, regardless of level, whereas ZnSO4 addition increased these performance indices only at the 3,000 mg of Zn/kg level of supplementation. Plasma Zn responses to ZnSO4 addition were almost double those of ZnO addition.(ABSTRACT TRUNCATED AT 250 WORDS)

Two hundred sixteen crossbred (PIC line 26 x Camborough 15) pigs were used in three trials to determine optimal digestible lysine levels during early (EF = 50 to 95 kg) and late (LF = 90 to 110 kg) finishing periods. Pigs were self-fed in sex groups of two in all trials. The assay diets for EF and LF periods were 11 and 10% CP corn-soybean meal diets, respectively, supplemented with threonine, methionine, tryptophan, valine, and isoleucine. Corn-soybean meal positive-control diets were included in each trial (14.5% CP for EF and 13.5% CP for LF). This dietary CP regimen was shown to give the same performance and carcass quality as a 17% CP corn-soybean meal diet fed during both EF and LF. Plateau portions of the lysine response curves resulted in performance levels that were equal to or greater than those achieved with pigs fed the 14.5/13.5% CP positive-control diets. Early-finishing pigs responded (P < .05) to graded doses of digestible lysine (.41 to .71%) for daily weight gain, gain:feed, longissimus muscle area, 10th-rib fat depth, lean gain, and plasma urea N. Digestible lysine requirement estimates based on average plateau points were .58% for EF barrows and .64% for EF gilts. Late-finishing pigs responded (P < .05) to digestible lysine doses (.35 to .65%) for daily weight gain, gain:feed, lean gain, and plasma urea N. Digestible lysine requirement estimates based on average plateau points were .49% for LF barrows and .52% for LF gilts.

Forty-eight crossbred (PIC line 26 x Camborough 15) pigs were used in two finishing trials to compare the ideal ratios of threonine (Thr), tryptophan (Trp), and sulfur amino acids (SAA) to lysine (Lys) determined for young pigs to a proposed ratio of these amino acids for finishing pigs. Trial 1 involved 20 barrows and 20 gilts that were self-fed in sex groups of two. Trial 2 was a Latin square design that used four barrows and four gilts that were individually fed in metabolism cages. Separate diets were used for the early (EF = 56 to 90 kg) and late (LF = 90 to 112 kg) finishing periods. Diets were formulated from a corn-soybean meal mixture and contained 11% CP and .55% digestible lysine for EF pigs and 10% CP and .50% digestible lysine for LF pigs. Negative-control diets in both the EF and LF periods were designed to be slightly deficient in lysine and to contain digestible Thr (65%), Trp (18%), and SAA (60%) at the ideal ratio to digestible Lys determined for 10- to 20-kg pigs. The experimental diet in both the EF and LF periods was formulated to contain digestible Thr (70%), Trp (20%), and SAA (65%) at the proposed ideal ratio to digestible Lys for finishing pigs. In Trial 1, increased ratios of Thr, Trp, and SAA improved gain:feed ratio, whole-body and carcass protein concentration, and whole-body and carcass protein accretion. In Trial 2, LF pigs responded to the increased ratios of Thr, Trp, and SAA with decreased urinary nitrogen excretion and increased N retention.(ABSTRACT TRUNCATED AT 250 WORDS)

Oat flour, the by-product resulting from commercial production of oat bran, was analyzed to contain 7.7% moisture, 11% CP, 6% crude fat, 8.8% NDF, 1.56% ash (.10% Ca, .23% P), 4,265 kcal/kg GE, .41% lysine, .36% threonine, .17% tryptophan, .21% methionine and .34% cystine. Chick bioassays revealed that lysine and threonine were the first- and second-limiting amino acids in oat flour. Slope-ratio protein quality assessment indicated that the protein quality of oat flour was similar to that of dehulled soybean meal. True ME (corrected for N retention, i.e., TMEn) of oat flour for adult cockerels was 3,726 kcal/kg. A P bioavailability assay with chicks indicated that the P in oat flour was 59.7% bioavailable relative to a KH2PO4 standard. Oat bran was analyzed to contain 9.7% moisture, 15% CP, 6.2% crude fat, 19.2% NDF, 2.33% ash (.12% Ca, .41% P), 4,316 kcal/kg GE, .59% lysine, .47% threonine, .18% tryptophan, .24% methionine and .44% cystine. Protein quality assessment in chicks indicated that the protein quality of oat bran was similar to that of dehulled soybean meal. True MEn of oat bran was found to be 3,449 kcal/kg. Of the .41% total phosphorus in oat bran, 42.2% was bioavailable, relative to the KH2PO4 standard.