A 2 x 2 x 2 factorial experiment was conducted with 64 pigs (4 wk old, 8.04 +/- .50 kg BW) to determine the effect of various dietary concentrations of Ca, vitamin D, and microbial phytase (Aspergillus niger) on phytate-P utilization. A low-P, corn-soybean meal diet was supplemented with two levels of phytase (unit/gram), 750 (suboptimal) and 1,200 (optimal); of vitamin D (international unit/kilogram), 660 (normal) and 6,660 (high); and of Ca (percentage), .4 (low) and .8 (normal). Pen feed consumption and individual pig weights, plasma inorganic P and Ca concentrations, and plasma alkaline phosphatase (AP) activity were measured at d 10, 20, and 30. The normal dietary Ca concentration had an adverse effect (P < .05) on all the response measures. The depressive effect of the normal dietary Ca on performance was greater (P < .05) at the normal vitamin D level or at the optimal phytase level than at the other levels of these two factors. The elevation in plasma AP activity in pigs fed the normal dietary Ca was greater (P < .05) at the suboptimal than at the optimal phytase level. The decreases in plasma inorganic P concentration and increases in plasma Ca concentration associated with the normal dietary Ca were substantial. In conclusion, the normal level of Ca in the diet greatly reduced the efficacy of supplemental phytase. Raising vitamin D in the diet partially offset this adverse effect but did not produce further improvement when the Ca level was low.

Three different methods for determining nonheme iron content of meat extracts which differed in final pH and either in heating or not heating of the samples, were compared. The final pH of meat extracts had little effect on the level of nonheme iron but heating gave higher values. Both final temperature and rate of heating influenced release of nonheme iron from meat pigment extracts, with the optimum temperature being 63-70°C. Slow heating resulted in release of more noneheme iron than fast heating. Nitrite was shown to prevent release of heme iron, apparently through stabilizing the porphyrin ring. Sources of nonheme iron and their relationship to oxidation in cooked meat are discussed.

Two studies were conducted to assess the effect of dietary protein reduction on N utilization, N excretion, and AA digestibility in growing pigs. The objective was to determine whether pigs fed diets with a reduced CP concentration could maintain the same N retention as pigs fed an adequate diet. The second objective was to test whether reducing dietary CP concentration decreases AA digestibility. In each study, six barrows were allotted to one of six dietary treatments in a Latin square design. Treatments consisted of four corn-soybean meal-based diets containing 15, 12, 9, and 6% CP, a casein-based diet containing 15% CP, and a protein-free diet. Crystalline AA were included in the 12, 9, and 6% CP diets. The indispensable:dispensable AA ratio was maintained at 45:55 with the addition of L-glutamic acid to the 9 and 6% CP diets. The casein-based and protein-free diets were used to determine endogenous total tract N and ileal AA losses. In the first study, total N losses and N absorbed decreased linearly (P < 0.001) as dietary CP concentration decreased from 15 to 6%. Both a linear (P < 0.001) and a quadratic (P < 0.05) decrease in N retention were found with decreasing dietary CP concentration. Nitrogen retained as a percentage of intake and absorbed increased (P < 0.001) as dietary CP concentration was reduced from 15 to 6%. In the second study, six barrows were surgically fitted with a T-cannula at the terminal ileum to determine ileal AA digestibility. For all dispensable and most indispensable AA, apparent and standardized ileal digestibility increased linearly (P 0.01, and for arginine, P < 0.05) as dietary CP concentration decreased. These results indicate that dietary CP concentration can be decreased from 15 to 12% with crystalline AA supplementation to meet an ideal AA profile without adversely affecting N retention, and that decreasing dietary CP concentration from 15 to 6% increases both dispensable and indispensable AA ileal digestibility.

Two experiments were conducted with weanling pigs to determine the effectiveness of a dietary supplement of Aspergillus niger phytase in improving the availability of phytate-P in corn-soybean meal diets without supplemental inorganic P. Experiment 1 consisted of two P and Ca balance trials and two feeding trials. Twelve pigs (8.18 +/- .44 kg BW) were housed individually in stainless steel metabolism cages. Six pigs received 750 phytase units (PU)/g of basal diet and the other six pigs received the basal diet without supplemental phytase as control. In Exp. 2, 96 pigs (8.81 +/- .75 kg BW) were allotted to 16 partially slotted floor pens and their basal diets were supplemented with either 0, 250, 500, or 750 PU/g for 4 wk. Individual pig weights and pen feed consumption were measured weekly. Blood samples were taken from all pigs at the end of each trial in Exp. 1 and from three pigs per pen weekly in Exp. 2 to measure serum (plasma) inorganic P (P) and Ca concentrations and alkaline phosphatase (AP) activities. The results of Exp. 1 indicated that dietary phytase increased P retention by 50% (P < .0001) and decreased fecal P excretion by 42% (P < .0001). Pigs that received dietary phytase had serum P and Ca concentrations and serum AP activities that were nearly normal, whereas control pigs had values indicative of a moderate P deficiency. Favorable effects of phytase disappeared when the phytase was removed from the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

ABSTRACT

This experiment was conducted to measure the nutritional and metabolic responses of pigs fed diets with continuous supplementation of microbial and cereal phytase from weaning to finishing, and to determine the feasibility of complete replacement of inorganic P addition by supplemental phytase in swine diets. Forty-eight Landrace x Hampshire x Meishan pigs were divided into four groups. In phase 1 (10 to 50 kg BW), pigs in Groups 1, 2, 3, and 4 were fed a low-P, corn-soybean meal basal diet (BD), the BD plus microbial phytase (A. ficuum) at 1,200 units/kg, the BD plus 10% wheat bran (230 units of cereal phytase/kg), and the BD + .24% inorganic P (calcium phosphate), respectively. In phase 2 (51 to 90 kg BW), these pigs were fed a similar BD or the BD plus 1,000 microbial phytase units/kg, 20% wheat bran, or .20% inorganic P, respectively. Repeated measures included growth performance, P, Ca, and N balance, metatarsal and metacarpal bone strength, serum concentration of inorganic P, Ca, and 1,25-dihydroxycholecalciferol, and serum alkaline phosphatase activity. Pigs fed the BD supplemented with microbial phytase and pigs fed the BD supplemented with inorganic P showed almost identical responses for all variables. Pigs fed the BD supplemented with cereal phytase also had responses for various measures that were similar to those of pigs fed microbial phytase or inorganic P, except for some differences in serum inorganic P concentrations and bone strength in phase 1. Because of improvements in apparent digestibility of dietary P and N, fecal excretion of these two nutrients was reduced by 31 to 62% (P < .05) in pigs fed the BD supplemented with phytase compared with pigs fed inorganic P. It is physiologically feasible and environmentally advantageous to replace inorganic P with microbial or cereal phytase in corn-soybean meal diets for this type of pig through the entire growing-finishing period.

Ten germ-free pigs and 10 conventionally reared pigs were fed one of two nutritionally balanced diets containing either 16 ppm Cu (basal) or 283 ppm Cu (high-Cu) to evaluate the physiological relationships between Cu and microbiological environment. Germ-free pigs tended to have higher ADG and average daily feed intake (ADFI) than conventionally reared pigs. Feeding the high-Cu diet tended to reduce ADG and ADFI in germ-free pigs but it increased ADG and ADFI in conventionally reared pigs. Hemoglobin and hematocrit were higher in germ-free pigs than in conventionally reared pigs (P less than .001), and hematocrit (P less than .01) and erythrocyte count (P less than .06) were reduced by feeding the high-Cu diet. Germ-free pigs had lower total leukocyte count (P less than .01) and the relative percentages of differentiated leukocytes were altered compared with conventionally reared pigs. Feeding the high-Cu diet increased the percentage of band neutrophils and monocytes in germ-free pigs but reduced the percentage of these cells in conventionally reared pigs (P less than .04). Germ-free pigs had higher concentrations of Cu and Zn in liver and plasma (P less than .001) and greater plasma ceruloplasmin oxidase activity (P less than .001) than conventionally reared pigs did. The high-Cu diet increased liver Cu and Zn (P less than .001) and plasma Cu (P less than .001) and reduced liver and plasma Fe (P less than .05). Organ weights (g/kg BW) differed between germ-free and conventionally reared pigs, and feeding the high-Cu diet reduced thymus weights (P less than .002). Intestinal weight and thickness were reduced in germ-free pigs, and feeding the high-Cu diet generally reduced villus height and width and crypt depth in germ-free pigs, whereas it increased these measurements in conventionally reared pigs.

Growth, nutrient balance, plasma ammonia levels and urinary p-cresol excretion were evaluated in growing pigs fed diets containing various levels of zeolite A or clinoptilolite. In one growth trial, crossbred pigs averaging 25 kg initial body weight were assigned to diets containing no zeolite, .3% zeolite A or .5% clinoptilolite for a 6-wk growing phase trial. Average daily gain (ADG), average daily feed intake (ADF) and feed/gain (F/G) were unaffected by supplementation of either zeolite in the diet, but metabolizable energy (ME) utilization was improved by feeding diets containing either zeolite. A second growth trial utilized the same crossbred pigs, which averaged 65 kg initial body weight, and were assigned to diets containing no zeolite, 1% zeolite A or 5% clinoptilolite for an 8-wk finishing phase trial. Average daily gain, ADF, and ME utilization were unaffected by feeding either zeolite diet, while F/G was increased in pigs fed the diet containing 5% clinoptilolite. In two nutrient balance trials, 16 crossbred pigs averaging 7.5 kg in initial body weight were fed diets containing 0, 1, 2 or 3% zeolite A in one trial and 16 crossbred pigs averaging 7.0 kg initial body weight were fed diets containing 0, 2.5, 5.0 or 7.5% clinoptilolite in a second trial. In both trials, digestible energy, ME, N-corrected ME and ME corrected for N balance and zeolite levels were linearly reduced as increasing amounts of either zeolite were fed. Daily fecal N increased and apparent digestibility of N was linearly reduced by feeding increasing amounts of zeolite A or clinoptilolite. Biological value of protein was improved linearly as higher levels of zeolite A were fed, indicating that there may be some ammonia binding to zeolite A in the gastrointestinal tract. Net protein utilization was reduced by feeding increasing levels of clinoptilolite in the diet. Calcium, P, Mg, Na, K and Fe retentions were linearly reduced by feeding increasing amounts of zeolite A in the diet, while increasing levels of clinoptilolite caused only P retention to be linearly reduced. Both free and conjugated forms of urinary p-cresol were linearly reduced by feeding increasing levels of clinoptilolite. Plasma ammonia levels were reduced at subsequent bleedings after a meal and by increasing levels of clinoptilolite.