Several bioassays were conducted with young chicks and pigs fed phosphorus (P)-deficient corn-soybean meal diets. With diets for chicks containing .62% Ca and .42% P (.10% available P), graded doses of a citric acid + sodium citrate (1:1, wt:wt) mixture (0, 1, 2, 4, or 6% of diet) resulted in linear (P < .01) increases in both weight gain and tibia ash. Relative to chicks fed no citric acid, tibia ash (%) and weight gain (g/d) were increased by 43 and 22%, respectively, in chicks fed 6% citric acid. Additional chick trials showed that 6% citric acid alone or sodium citrate alone was as efficacious as the citric acid + sodium citrate mixture and that 1,450 U/kg of phytase produced a positive response in bone ash and weight gain in chicks fed a diet containing 6% citrate. Varying the Ca:available P ratio with and without citrate supplementation indicated that citric acid primarily affected phytate-P utilization, not Ca, in chicks. Moreover, chicks did not respond to citrate supplementation when fed a P-deficient (.13% available P), phytate-free casein-dextrose diet. Young pigs averaging 10 to 11 kg also were used to evaluate citric acid efficacy in two experiments. A P-deficient corn-soybean meal basal diet was used to construct five treatment diets that contained 1) no additive, 2) 3% citric acid, 3) 6% citric acid, 4) 1,450 U/kg phytase, and 5) 6% citric acid + 1,450 U/kg phytase. Phytase supplementation increased (P < .01) weight gain, gain:feed, and metatarsal ash, whereas citric acid addition increased only gain:feed (P < .05) and metatarsal ash (P < .08). A subsequent 22-d pig experiment was conducted to evaluate the effect of lower levels of citric acid (0, 1, 2, or 3%) or 1,450 U/kg phytase addition to a P-deficient corn-soybean meal diet. Phytase supplementation improved (P < .01) all criteria measured. Weight gain and gain:feed data suggested a response to citric acid addition, but this was not supported by fibula ash results (P > .10). The positive responses to phytase were much greater than those to citric acid in both pig experiments. Thus, dietary citric acid effectively improved phytate P utilization in chicks but had a much smaller effect in pigs.

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Three experiments were conducted to determine the effects of enzyme supplementation and particle size of wheat-based diets on growth performance and nutrient digestibility in nursery and finishing pigs. In Exp. 1, 180 weaned pigs (5.7 kg and 21 d of age) were fed diets in a 35-d growth assay without or with a Trichoderma longibrachiatium enzyme product (4,000 units of xylanase activity per gram of product) and with wheat ground to mean particle sizes of 1,300, 600, or 400 microm. Enzyme supplementation had no effect on ADG or gain/feed (P > 0.32), but there was a trend (P < 0.10) for greater digestibility of DM (d 6) in enzyme-supplemented diets. A particle size of 600 microm supported the greatest overall gain/feed (quadratic effect, P < 0.01). An interaction of enzyme supplementation with particle size occurred; gain/feed was improved (P < 0.01) with enzyme supplementation at the coarse (1,300 microm) particle size but not when the wheat was ground to 600 or 400 microm. In Exp. 2, 160 finishing pigs (67 kg) were fed a diet without or with the same enzyme used in Exp. 1 and wheat ground to 1,300 or 600 microm. No interactions occurred between enzyme supplementation and particle size of the wheat (P > 0.15). However, there were trends for greater gain/feed (P < 0.10) during the 67- to 93-kg phase of the experiment and for greater digestibility of DM (P < 0.10) and N (P < 0.07) with enzyme supplementation. When particle size was reduced from 1,300 to 600 microm, gain/feed was improved (P < 0.03) for the 93- to 114-kg phase of the growth assay, and digestibilities of DM (P < 0.02) and N (P < 0.04) were greater. In Exp. 3, 160 finishing pigs (63 kg) were given diets without or with the enzyme product and wheat ground to 600 or 400 microm. Enzyme supplementation improved ADG (P < 0.04) in the 90- to 115-kg phase but otherwise did not affect growth performance, carcass measurements, or stomach lesions. A particle size of 400 microm increased overall gain/feed (P < 0.04), digestibilities of DM and N (P < 0.01), and development of stomach lesions (P < 0.01). In conclusion, pigs did not benefit consistently from enzyme supplementation. However, wheat particle sizes of 600 and 400 microm supported the best overall performance in nursery and finishing pigs, respectively.

Commercial sources of zinc oxide (ZnO) differ widely in Zn relative bioavailability (RBV), but it is unknown whether growth-promoting efficacy in young pigs is influenced by RBV of the ZnO sources used. We compared a low-RBV (39%) ZnO manufactured by the Waelz process (W) to a high-RBV (93%) ZnO manufactured by the hydrosulfide process (HS). Antibacterial agents were included in the diet in only one of the four trials (Exp. 4). In Exp. 1, pigs (n = 36, 6.5 kg, 28 d of age) were randomly assigned in three replicates to receive 0, 1,500, or 3,000 mg Zn/kg from HS Zn in a 21-d growth assay. Growth rates and feed intake responded linearly (P < 0.01) to incremental doses of Zn. In Exp. 2, pigs (n = 60, 6.1 kg, 28 d of age) were randomly assigned in five replicates to receive either 0 or 1,500 mg W or HS Zn/kg during a 21-d feeding period. Growth performance was improved (P < 0.01) by the addition of ZnO. During wk 1, however, pigs receiving HS Zn grew faster (P < 0.03) than those receiving W Zn, but the difference diminished to a trend (P < 0.08) during wk 2. Morphology of duodenal, jejunal, and ileal intestinal sections was examined at d 21 of the assay, but neither source of ZnO had an effect on crypt depth or on villus height or width. In Exp. 3, weaned pigs (n = 48, 5.4 kg, 21 d of age) were randomly assigned in four replicates to the same dietary treatments as in Exp. 2 for a 17-d growth assay. Growth performance was improved (P < 0.05) by the addition of ZnO, but no difference was detected between the two sources. In Exp. 4, pigs (n = 60, 6.2 kg, 28 d of age) were randomly assigned in five replicates to receive either 0 or 1,500 mg/kg W or HS Zn in an 11-d growth assay wherein antimicrobial agents were included in the basal diet. Growth rates during the first 6-d were improved (P < 0.06) by the addition of ZnO, with a trend (P < 0.10) for greater weight gain in pigs receiving HS than in those fed W Zn. During the entire 11-d, however, there was no difference in growth rates between pigs fed the two sources of ZnO. In conclusion, RBV of Zn in ZnO did not substantially affect the growth-promoting efficacy of ZnO in young pigs fed diets with or without antimicrobial agents.

The results of the present study show that migraine prevalence was 6.2% (95% confidence interval [CI], 5.4 to 7.0). The estimated prevalences of migraine with and without aura were 2.8% (95% CI, 2.3 to 3.4) and 3.4% (CI, 2.8 to 4.0), respectively. The prevalence of migraine increased with age and it was found to be almost equal in boys and girls aged 7 to 9 years or younger, but in older age groups the prevalence was higher in girls than in boys. The data showed no evidence that connected migraine with social class. It also showed that except for the aura, the headache (e.g., frequency, duration, location, quality, and severity) and nonheadache (e.g., nausea, vomiting, phonophobia, and photophobia) characteristics were no different between children with migraine, with and without aura. In conclusion, our findings indicate that migraine is a common underdiagnosed cause of severe recurrent headache in children. The findings show that childhood migraine is not connected with social class and varies with age and gender, and that except for the aura, both migraine with and without aura are so similar in their headache and nonheadache clinical characteristics that a common pathogenesis is plausible.