Four experiments involving 225 pigs were conducted to assess the efficacy of a microbial phytase (FINASE, Alko Ltd. Biotechnology, Rajamäki, Finland) produced by Aspergillus niger in corn-soybean meal or dextrose-cornstarch-soybean meal-based diets. In two experiments with growing-finishing pigs, fortified corn-soybean meal diets were formulated to be adequate (.50%) or inadequate (.40 or .30%) in P during the growing phase followed by adequate (.40%) or inadequate (.30%) P in the finishing phase. Mono-dicalcium phosphate was the source of supplemental P. Half the diets were supplemented with phytase (500 phytase units/g). Rate and efficiency of gain and bone breaking strength were decreased when P-deficient diets were fed. Phytase supplementation of the low-P diets restored growth rate and feed:gain to levels that approached those of pigs fed the adequate-P control diet. Bone strength was partially restored to that of the controls. In two additional experiments, pigs were fed low-P basal diets in which all the dietary P came from soybean meal or a corn-soybean meal blend. Both diets contained .05% available P. Graded levels of monosodium phosphate were added to these diets, up to .15% added P, to establish a standard curve. Phytase was added to the basal diet at 250, 500, or 1,000 units/g. Growth rate and bone strength improved linearly (P < .01) with added monosodium phosphate and with increasing levels of supplemental phytase. Based on estimates of total and available P intakes, the highest level of phytase (1,000 units/g) increased the bioavailability of the P from 25% in the soybean meal diet to 57% in the phytase-supplemented diet, and from 15% in the corn-soybean diet to 43% in the phytase-supplemented diet. Expressed on the basis of the improvement in phytate P availability, this level of phytase converted approximately one-third of the unavailable P to an available form. The results indicate that the phytase was efficacious in improving the bioavailability of phytate P for pigs.

Five 28- to 33-d experiments involving 460 crossbred pigs weaned at 28 +/- 2 d of age (initial weight, 6.7 to 8.1 kg) were conducted to determine the effects of feeding high dietary levels of Cu sulfate (CuSO4) or Cu oxide (CuO) on rate and efficiency of gain and liver Cu stores of weanling pigs. The pigs were housed in groups of five to six/pen and fed a fortified, unmedicated, corn-soybean meal-dried whey basal diet (1.1% lysine, 30 ppm Cu). In Exp. 1 and 2, pigs (eight replicates) were fed the basal or the basal plus 125 or 250 ppm Cu from CuSO4 or CuO for 28 d. In Exp. 3 and 4, four replications were fed the same diets as in Exp. 1 and 2 plus two additional diets (500 ppm Cu from CuSO4 or CuO). In Exp. 5, dietary levels of 0, 125, 250, 375 or 500 ppm Cu from CuSO4 were evaluated using four replications. At the end of each experiment, the liver from one pig in each pen was collected for Cu analysis. Overall, rate and efficiency of gain were improved (P less than .01) by feeding 125 or 250 ppm Cu as CuSO4, with the 125 ppm dietary level being about 75% as effective in stimulating growth as 250 ppm. Performance of pigs was not different from controls when the highest (500 ppm) level of Cu (from CuSO4) was fed. Liver Cu increased 10- to 70-fold when 250 to 550 ppm Cu from CuSO4 was included in the feed.(ABSTRACT TRUNCATED AT 250 WORDS)

Three experiments involving 162 pigs were conducted to assess the efficacy of phytase (Natuphos; BASF, Mount Olive, NJ) in low-P, corn-soybean meal-based diets. The phytase was produced by a recombinant Aspergillus niger. The phytase supplement contained 5,000 phytase units (PTU)/g. In Exp. 1 (66 pigs) and 2 (60 pigs), growing-finishing pigs were fed fortified corn-soybean meal diets formulated to be adequate (.50%), marginal (.425%), or inadequate (.35%) in P during the growing phase (23 to 60 kg BW) followed by adequate (.40%), marginal (.35%), or inadequate (.30%) P, respectively, during the finishing phase (to 104 kg BW). Dicalcium phosphate was the source of supplemental P. In addition, the low-P sequence (.35/.30% P) was supplemented with phytase at 250, 500, or 1,000 PTU/kg. Rate and efficiency of gain decreased linearly (P < .01) and bone breaking strength decreased quadratically (P < .01) as the concentration of P was decreased in the diets. Responses in growth and bone traits to increasing levels of phytase activity in the low-P diet were linear (P < .01). The highest level of phytase in the low-P diet restored growth rate and bone breaking strength to levels that approached or met those of pigs fed the adequate P diet.(ABSTRACT TRUNCATED AT 250 WORDS)

We conducted three 28-d experiments involving a total of 915 pigs to assess the relative efficacy of tribasic Cu chloride (Cu2[OH]3Cl) and Cu sulfate pentahydrate (CuSO4.5H20) in diets for weanling pigs. Experiments 1 and 2 were conducted at an experiment station (University of Kentucky), and Exp. 3 was conducted at a commercial feed company's swine research facilities (United Feeds, Inc.). The basal diet was a fortified corn-soybean meal-dried whey diet (1.25% lysine) with no antimicrobials in Exp. 1 or with carbadox (55 mg/kg) in Exp. 2 and 3. In Exp. 1, 135 pigs were weaned at 27 to 31 d and fed the basal diet without or with 100 or 200 ppm Cu from Cu chloride, or 100 or 200 ppm Cu from Cu sulfate from 7.9 to 17.7 kg BW. The 200 ppm level of Cu from Cu sulfate improved ADG (P < .10), and both levels of Cu from Cu chloride tended to improve feed:gain. In Exp. 2, 150 pigs were weaned at 27 to 31 d and fed the basal diet without or with 100, 150, or 200 ppm Cu from Cu chloride, or 200 ppm Cu from Cu sulfate from 8.9 to 20.8 kg BW. Addition of 200 ppm Cu improved ADG (P < .08) and ADFI (P < .01), but not feed:gain. Source of Cu did not affect performance. In Exp. 3, 630 pigs were weaned at 16 to 20 d and fed a common diet for 10 to 12 d until the start of the experimental period. The same experimental diets as used in Exp. 2 were fed from 9.1 to 25.5 kg BW. Both Cu sources improved ADG (P < .01), and sources and levels of Cu did not differ. Liver Cu increased in pigs fed 200 ppm Cu, and Cu sulfate tended to increase liver Cu more than did Cu chloride in one experiment, but not in another experiment. The results indicate that tribasic Cu chloride is as effective as Cu sulfate in improving growth in weanling pigs.

Five trials involving 518 pigs were conducted to determine the effects of the dietary addition of copper (0 or 250 ppm as copper sulfate) with and without antibiotics (55 ppm chlortetracycline, CTC, or 27.5 ppm virginiamycin VIR) on the rate and efficiency of gain and survival of early-weaned pigs. The experimental animals consisted of all pigs weaned from each of 67 litters at 28 +/- 2 days of age, regardless of weight or condition. In trials 1 through 4, single additions of copper, CTC or VIR to the corn-soybean meal-based diet improved (P less than .05) daily gains by 22, 22 and 17%, respectively, and feed to gain ratios by 5.1, 8.9 and 8.2% compared with those of pigs fed the unsupplemented diet during the 28-day trials. However, only the addition of copper to the diet increased (P less than .05) postweaning pig survival. Dietary inclusion of both copper and an antibiotic (CTC or VIR) further improved daily gains (P less than .05) by 10 to 11% and feed to gain ratios by 2 to 5% compared with the single addition of each antimicrobial agent. In trial 5, 125 ppm of copper were found to optimize daily gain and feed intake, whereas 250 ppm were required to maximize pig survival. These data demonstrate that high levels (125 to 250 ppm) of dietary copper increase the growth rate and reduce the incidence of mortality among weanling pigs. The data also indicate that the growth-promoting effects of copper and CTC, a broad spectrum antibiotic, or VIR, a gram-positive antibiotic, are additive in nature.