E. T. Kornegay

Response of broilers to graded levels of microbial phytase added to maize–soyabean-meal-based diets containing three levels of non-phytate phosphorus

Male 1-d-old broilers (n 920) were given 0, 200, 400, 600, 800, 1000 and 1200 U microbial phytase/kg diet in combination with 2.0, 2.7 or 3.4 g non-phytate P (nP)/kg or 4.0, 5.1 or 5.8 g total P (tP)/kg in a 21 d trial to assess the effectiveness of phytase in a maize-soyabean-meal diet. In addition to the above twenty-one diets, a positive control P diet supplied 4.5 g nP/kg, 6.9 g tP/kg and 10 g Ca/kg. The basal diet contained 230 g crude protein/kg, 8.8 g Ca/kg, 4.4 g tP/kg and 2.0 g nP/kg. Defluorinated phosphate and limestone were used to supply P and Ca. A Ca:tP ratio of 2:1 was maintained except in the positive control diet which had a ratio of 1.45:1. Phytase additions linearly increased (P < 0.01) body-weight (BW) gain, feed intake, toe ash percentage, and apparent retention (% of intake) or total amount (g/bird) of retained Ca and P, and linearly decreased (P < 0.01) P excretion (g/kg of DM intake) at each level of nP with the magnitude of the response inversely related to the level of nP. Above-normal mortality was only observed in the group receiving 2.0 g nP/kg diet without phytase. Adding nP linearly increased (P < 0.01) BW gain, feed intake, toe ash percentage, Ca retention, total amount (g/bird) of P retained, and P excretion, and linearly decreased (P < 0.01) apparent retention (%) of P. Derived linear and non-linear equations for BW gain and toe ash percentage at the two lower nP levels, 2.0 and 2.7 g/kg, were used to calculate P equivalency values of microbial phytase. The results show that 939 U microbial phytase is equivalent to 1 g P from defluorinated phosphate in broilers fed on maize-soyabean-meal diets. The amount of P released per 100 U phytase decreased as the total amount of phytase increased.

Sites of phytase activity in the gastrointestinal tract of young pigs

The sites of supplemental phytase activity in the gastrointestinal tracts (GIT) of young pigs fed added microbial phytase were determined in two tests. In Test 1, samples of diets and GIT (stomach, upper and lower small intestine) contents were taken from pigs (BW = 20.3 kg) that had been fed a soybean meal-based semi-purified diet containing two levels of available P (0.5 and 1.6 g kg−1 aP), without or with added microbial phytase (1050 U kg−1 diet) for 5 weeks. There was no detectable phytase activity in the diets and GIT contents of pigs fed the basal diets without added phytase, and phytase activity did not differ for diets or GIT contents between the two dietary P levels. For pigs fed diets with added phytase, phytase activity in the digesta from stomach was higher (P < 0.001) than that from upper small intestine (51 or 31% of diet activity). No phytase activity was detectable in the digesta of the lower small intestine. In Test 2, samples of diets and GIT contents were taken from young pigs (BW = 16.7 kg) that had been fed a corn and soybean meal diet with added microbial phytase (750 U kg−1 of diet) containing one of three levels of citric acid (0, 15, and 30 g kg−1) for 4 weeks. Adding 30 g kg−1 citric acid decreased (P < 0.06) phytase activity in the stomach digesta; but there was no difference between the 15 and 30 g kg−1 added citric acid. About 40% of the added phytase activity remained in the digesta of the stomach from pigs fed the diet without added citric acid; whereas, only 27% of the phytase activity remained in the stomach digesta from pigs fed the diet with added citric acid. Again, phytase activity in the digesta from stomach was higher (P < 0.05) than that in digesta from upper small intestine (16 and 10% of added activity, respectively for diets without and with citric acid). As in Test 1, no phytase activity was detectable in lower small intestine digesta. In summary, the stomach is the site of highest added microbial phytase activity most likely because of a more favorable pH and lower protease activity.

Replacement of inorganic phosphorus by microbial phytase for young pigs fed on a maize-soyabean-meal diet

Ninety-six crossbred young pigs (body weight 7.8 kg) were used in a 5-week trial to determine the effectiveness of microbial phytase (EC 3.1.3 26) in improving the bioavailabilities of P and other nutrients in maize-soyabean-meal diets and, thus, replacing inorganic P with phytase. A 2 x 5 factorial arrangement of treatments was employed with two available P (aP) levels (0.7 and 1.6 g/kg) and five phytase levels (0, 350, 700, 1050, 1400 U (the quantity of enzyme that liberates 1 mumol inorganic phosphate/min from 5.1 mm-sodium phytate at pH 5.5 and 37 degrees)/kg diet). In addition, two extra diets were formulated to supply the National Research Council (1988) recommended level of aP (3.2 g/kg) with 0 or 1400 U phytase. The addition of graded levels of phytase resulted in linear increases in average daily weight gain, average daily feed intake and weight gain:feed intake for pigs fed on diets containing 0.7 or 1.6 g aP/kg (P < 0.04). Also, the addition of phytase linearly increased apparent digestibilities of P and Ca (P < 0.01), whereas faecal P excretion was linearly decreased (P < 0.01). Linear increases in shear force, shear energy and ash content of both the metacarpal and tenth rib, and shear stress of the metacarpal were found to respond to added phytase (P < 0.01). These improvements in performance, apparent P absorption and bone measurements by phytase were also observed by increasing dietary aP levels for most measurements. Adding 1400 U phytase to the 3.2 g aP/kg diet further increased average daily weight gain, average daily feed intake, apparent absorption of P, Ca and N and metatarsal shear force and ash content (P < 0.01 to 0.05). Generally, maximum responses occurred at a phytase level of 1050 U/kg diet for the 0.7 g aP/kg diets and 700 U for the 1.6 g aP/kg diets. Based on non-linear and linear response equations generated for the phytase and aP levels, the average function of the equivalency of P (Y, g/kg) v. microbial phytase (X, U/kg) was developed across aP levels of 0.7 and 1.6 g/kg for average daily weight gain and apparent digestibility of P: Y = 2.622-2.559e 0.00185X. The replacement of 1 g inorganic P as defluorinated phosphate would require about 246 U microbial phytase. This represents 41% of released P from phytate.

Effects of organic acids with and without a microbial culture on performance and gastrointestinal tract measurements of weanling pigs

In Study 1, 25-day-old crossbred weanling pigs (n = 144) were fed a 20% crude protein maize-soyabean meal basal diet. Supplementation with 1.5% citric acid tended to improve gain and the efficiency of feed utilization (F:G) during the first 4 weeks with no effect during week 5; 1.5% fumaric acid caused smaller and non-significant improvements in gain and F:G. Feed intake was unaffected by organic acids. The pH, chloride ion and volatile fatty acid concentration of intestinal contents from the stomach, jejunum, cecum and lower colon of 27 pigs killed at the end of Study 1 were not significantly affected by dietary organic acids. With the exception of fumarate, the concentration of non-volatile acids was not affected by diet. The stomach and jejunum of pigs given fumaric acid had a greater concentration (P < 0.05) of fumarate than those of pigs given the control and citric acid diets. In Study 2 (n = 192), no interactive effect of dietary fumaric or citric acid with a live microbial culture (Lactobacillus acidophilus) was observed. Fumaric acid supplementation increased (P < 0.03) gain and the microbial culture improved gain (P < 0.08) and F:G (P < 0.02) during the 5 week test; 1.5% citric acid had no effect. In conclusion, the addition of citric or fumaric acid and/or a microbial culture produced inconsistent improvements in gain and F:G, with little effect on intestinal digesta measurements.

Influence of processing methods and storage time on the cyanide potential of cassava leaf meal

Ravindran, V., Kornegay, E.T. and Rajaguru, A.S.B., 1987. Influence of processing methods and storage time on the cyanide potential of cassava leaf meal. Anim. Feed. Sci. Technol., 17:227-234 The effect of three processing methods (drying, chopping and wilting ), their combinations and the storage time on the hydrocyanide potential (HCNp) and the crude protein (CP) content of cassava (Manihot esculenta Crantz. ) leaf meal (CLM) were evaluated. Limited observations on the effects of processing treatments on the tannin content of CLM were also made. Fresh cassava leaves contained an average of 1436 mg HCNJkg dry matter and simple drying (sun- or oven-) eliminated almost 90% of the HCNp. A combination of chopping and 3-day wilting before drying proved most effective, lowering the cyanide potential of the final product to about 55 mg/kg dry matter. The processing treatments had little effect on the CP and tannin contents of CLM. The HCNp and CP content of CLM declined by 58.2 and 10.6%, respectively, during an 8-month postprocessing storage. The results demonstrate that low-cyanide CLM, which is safer for use as an animal feed, could be produced using simple processing methods.

Efficacy of virginiamycin and a commercially-available lactobacillus probiotic in swine diets

Eight feeding trials using 708 cross-bred pigs were conducted to evaluate the addition of virginiamycin and a commercially-available lactobacillus fermention product (probiotic) to starter, grower and finisher diets based on maize and soya bean meal. Virginiamycin was added at a level of 11 mg/kg of diet, and lactobacillus probiotic at 1 g/kg in starter diets and 500 mg/kg in grower and finisher diets. In the combined analysis of four starter trials, pigs fed on diets containing virginiamycin tended to eat more and grow faster than pigs fed on the control diet, but feed efficiency was not different. Furthermore, daily gain, daily feed intake and feed efficiency were not improved by the addition of lactobacillus probiotic to starter diets. In the combined analysis of a starter—grower—finisher and a grower—finisher trial, virginiamycin supplementation did not alter overall pig performance compared with control. Pigs fed on a positive control diet containing chlortetracycline, penicillin and sulfamethazine had a nonsignificantly greater daily gain and feed intake. Daily gain for the lactobacillus probiotic-fed pigs was lower (P < 0.05) than that of the negative controls, but daily feed intake and feed efficiency were not significantly different. In three growing—finishing trials in which virginiamycin and lactobacillus probiotic were compared in a 2 × 2 factorial arrangement of treatments, daily gain and feed intakes were greater (P < 0.01) for pigs given virginiamycin. The lactobacillus probiotic did not improve daily gain, feed intake or feed efficiency. Overall, no interaction between virginiamycin and lactobacillus probiotic occurred.

Effects of supplemental phytase and phosphorus on histological, mechanical and chemical traits of tibia and performance of turkeys fed on soyabean-meal-based semi-purified diets high in phytate phosphorus

Tibial traits were investigated for turkey poults fed on soyabean-meal-based semi-purified diets high in phytate P (2.2 g/kg) with added phytase and inorganic P. Dietary treatments were: (1) 2.7 g non-phytate P (nP)/kg; (2) diet 1 + 1000 U phytase/kg diet; (3) 3.6 g nP/kg; (4) diet 3 + 800 U phytase; (5) 4.5 g nP/kg; (6) diet 5 + 600 U phytase; (7) 6.0 g nP/kg. Added phytase and nP increased (P < 0.006) tibial dry matter, ash weight and content, body-weight gain, feed intake and gain:feed. The Mg and Zn concentrations in the tibial ash were also increased (P < 0.001 and P < 0.09 respectively) by added phytase or nP; tibial P and Ca concentrations tended to be increased. Hypertrophy zone width of the tibial proximal end decreased (P < 0.001), while proliferating zone width, tibial length, and widths at the long and short axes increased (P < 0.003) as phytase and nP were added. The addition of phytase also tended to enlarge the cartilaginous zone width, which was linearly increased (P < 0.05) by added nP. Disorganization scores of the hypertrophy zone and trabecular bone were low, approaching normal (P < 0.05), for turkey poults fed on diets with phytase supplementation, and tibial abnormality scores were linearly decreased (P < 0.001) as nP levels increased (zero score is considered normal). Adding phytase and nP improved the orderliness of development, mineralization and arrangement of cartilage and bone cells, and alleviated the effects of P deficiency on the histological and gross structure of the tibias. Tibial shear stress increased (P < 0.04) as phytase and nP were added. In summary, similar improvements in bone characteristics were achieved for turkey poults fed on a P-deficient diet supplemented with either phytase or nP.

Variance of body weights and daily weight gains of weaner pigs housed at various stocking densities in confinement

Body weight and gain data from eight studies conducted with weaner pigs to determine the relationship between stocking density and performance were used to evaluate the effect of various stocking densities on several factors which measure variation within pens. The initial weight of the pigs ranged from 5·7 to 8·3 kg and final weight ranged from 17·7 to 32·1 kg. There were 244 pens of pigs with floor space ranging from 0·11 to 0·28 m 2 per pig. Average daily gain and body weight were depressed as stocking density increased. Natural logarithms of variance, coefficients of variation and ranges of average daily gains and body weights were not increased by stocking density. Body weights and daily gains appeared equally effective in measuring variance of weaner pigs housed at various densities. These results indicate that increasing stocking density within the range of densities tested does not cause a greater variation in body-weight gains.

Effect of chlortetracycline supplementation during prebreeding and early gestation on age at puberty, ovulation rate, embryo survival and fetal development in gilts

A total of 166 crossbred gilts weighing approximately 87 +/- 1 kg was limit-fed (2.5 kg/d) a corn-soybean meal gestation diet containing either 0 or 220 ppm of chlortetracycline (CTC) from 157 +/- 1 d of age until 15 d after breeding. These gilts were slaughtered at 31 +/- 1 or 71 d +/- 1 d of gestation for evaluation of reproductive performance. Age (190 +/- 3 d vs 195 +/- 3 d) and body weights (106 +/- 2 kg vs 106 +/- 2 kg) at puberty were similar for control and CTC-fed gilts, respectively. Although not significant (P > 0.05), ovulation rate was higher in CTC-fed than in control gilts as assessed at both 31 d (14.2 +/- 0.7 vs 12.9 +/- 0.9, P = 0.31) and 71 d (13.9 +/- 0.6 vs 12.4 +/- 0.5, P = 0.10) of gestation. There was an increase (P = 0.04) in the number of live embryos for CTC-fed gilts at 31 d (12.1 +/- 0.7 vs 9.7 +/- 0.7) but not at 71 d (10.0 +/- 1.1 vs 9.6 +/- 1.0) of gestation. The mean uterine length, placental length, placental weight, fetal length, fetal weight, and allantoic fluid volumes were similar between the control and CTC-fed gilts. Results indicated that feeding CTC during prebreeding and early gestation did not influence the proportion or age of gilts at puberty. However, CTC feeding may have influenced a trend to-ward an increased ovulation rate and increased number of live embryos in gilts.