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Biomedical subjects

V Ravindran

Publications and source records attributed to V Ravindran.

At least 19 recordsLinked to original sources
PubMed1998

Influence of guanidination on apparent ileal amino acid digestibility in some protein sources for broilers.

High pH employed during the guanidination process (conversion of lysine residues to homoarginine) and its possible effects on racemization of amino acid residues to D-forms and on amino acid digestibility are concerns often raised with the use of guanidinated proteins to estimate endogenous amino acid losses in monogastric animals. The objective of the present study was to investigate the influence of guanidination on apparent ileal amino acid digestibility of casein, soybean meal, cottonseed meal, and canola meal for broiler chickens. Apparent ileal digestibility of amino acids in guanidinated and unreacted proteins, with few exceptions, were found to be remarkably similar. These results suggest that the guanidination process has no influence on the susceptibility of proteins to proteolysis and that racemization is not a practical problem when the proteins are guanidinated at low temperatures.

Amino Acids↗
PubMed1997

Secretion of homoarginine into the gut of chickens.

A technique, based on the homoarginine present in guanidinated proteins, has been used to distinguish between endogenous secretions and exogenous dietary amino acids in the ileal digesta of monogastric animals. This technique assumes that the ingested homoarginine is not recycled into the small intestine after absorption, but this assumption is yet to be experimentally validated in chickens. The secretion of homoarginine into the gut of broilers that were intravenously infused with 20 and 40 mmol/L homoarginine solutions was assessed. The plasma concentrations of homoarginine increased with increasing concentrations of homoarginine infused. However, only negligible levels of homoarginine (7.0 to 45.2 micrograms/g dry matter) were found in the digesta. Less than 0.01% of the intravenously infused homoarginine was recovered in the intestinal digesta, indicating that the secretion of homoarginine into the gut of chickens was insignificant.

Amino Acids↗
PubMed1997

Influence of caecectomy and dietary protein concentration on apparent excreta amino acid digestibility in adult cockerels.

1. The influence of caecectomy and dietary crude protein content (50, 100, 150, 200 and 250 g/kg diet) on the apparent excreta amino acid digestibilities in adult cockerels fed on semi-purified diets containing soyabean meal (SBM) or cottonseed meal (CSM) as the sole source of protein was investigated. 2. Caecectomy had no influence on the apparent digestibilities of most amino acids in SBM, the exceptions being histidine, arginine and lysine, but lowered the apparent digestibility of amino acids in CSM. 3. The protein content in assay diets has a strong influence on the apparent amino acid digestibility values for poultry. Apparent values are lower when the dietary protein content is low. 4. The use of a single endogenous amino acid output value, generated by regression analysis or protein-free diets, for true digestibility adjustments across a wide range of protein intakes is questioned. In particular, such an application will penalise estimates of apparent digestibility when the dietary protein content is high.

Amino Acids↗
PubMed1997

Evaluation of homoarginine as a marker for the determination of endogenous amino acid concentrations in poultry excreta.

1. Endogenous amino acid losses in ileal digesta and excreta of adults cockerels fed on diets containing guanidinated forms of casein, soyabean meal and cottonseed meal were determined using homoarginine as a marker. 2. The ileal endogenous amino acid losses were markedly higher (P < 0.001) in birds given the cottonseed meal diet compared to those given the other two diets. The ileal endogenous protein was rich in aspartic acid, serine and glutamic acid. 3. Negative values were obtained for endogenous amino acid output in excreta. These aberrant values were caused by high concentrations of homoarginine in the excreta. A subsequent study with broiler chickens showed that the homoarginine in excreta was of urinary origin. 4. These results indicate that the homoarginine technique is not suitable for determining endogenous amino acid losses in excreta, but applicable when determinations are made in the terminal ileum.

Amino Acids↗
PubMed1997

Homoarginine influences voluntary feed intake, tissue basic amino acid concentrations and arginase activity in chickens.

Two experiments were conducted to investigate the factors responsible for the adverse effects of guanidinated proteins on feed intake in chickens. In Experiment 1, male broiler chicks were fed one of five purified diets containing casein or guanidinated casein (G-casein) as the sole source of protein (230 g crude protein/kg diet) from d 6 to 13 post-hatching. A casein-based diet containing 17.2 g lysine/kg, served as the control. In the experimental diets, casein was substituted by G-casein and lysine was added at 0, 5.6, 11.4 and 17.0 g/kg diet, respectively. Feed intake and weight gains of chicks fed the G-casein diet without added lysine were markedly depressed (P < 0.05), but this depression was largely overcome by additional lysine. The intake and gains of chicks fed the G-casein diet plus 17.0 g lysine/kg were lower (P < 0.05) than those fed the G-casein diet plus 11.4 g lysine/kg and this was associated with a higher plasma lysine:arginine ratio. Tissue analysis showed that homoarginine is distributed throughout body tissues following absorption. Brain lysine concentrations were lower (P < 0.05) in chicks fed diets containing G-casein without added lysine, but increased (P < 0.05) with supplemental lysine. In Experiment 2, the effect of homoarginine per se on feed intake was investigated in two short-term intake studies using 5-wk-old broiler chickens. Significant (P < 0.05) depressions in feed intake were observed within the first hour after oral administration of 400 mg homoarginine-HCl. The results suggest that both lysine deficiency and homoarginine per se were responsible for the adverse effects of guanidinated proteins on feed intake in chickens.

Amino Acids, Essential↗
PubMed1996

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.

6-Phytase↗
PubMed1996

Replacement of maize with sweet potato (Ipomoea batatas L.) tuber meal in broiler diets.

1. The nutrient composition of sweet potato tuber meal (SPM) was similar to that of maize, with the exceptions of crude protein and calcium. The crude protein content was lower (62 v 91 g/kg) and the calcium content was higher (l.9 v 0.l g/kg) in SPM. The amino acid composition, in general, favoured SPM. 2. Trypsin inhibitor activity, and the contents of oxalate and phytate-phosphorus in SPM were too low to be of any nutritional concern. 3. The apparent metabolisable energy content of SPM was determined to be similar to that of maize (14.5l V 14.45 MJ/kg). 4. The results of feeding trials showed that SPM can replace up to 400 g/kg maize in broiler diets without adverse effects in performance. The depression in weight gains observed in birds fed on a diet containing 600 g SPM/kg was related largely to lowered food intake arising from the powdery texture of SPM.

Animal Feed↗
PubMed1996

Effectiveness of Natuphos phytase in improving the bioavailabilities of phosphorus and other nutrients in soybean meal-based semipurified diets for young pigs.

Crossbred pigs (n = 96, BW = 7.5 kg) were used in a 5-wk trial to determine the effectiveness of supplemental Natuphos phytase in improving the bioavailabilities of P and other nutrients in a semipurified diet with soybean meal as the only P source in the basal diet. Two available P (aP) levels (.05 and .16%) and five phytase levels (0, 350, 700, 1,050, and 1,400 units/kg of diet) were used in a 2 x 5 factorial arrangement of treatments. In addition to the 10 diets, two extra diets were formulated to supply the recommended level of aP (.32%) with 0 and 1,400 units (U) of phytase/kg of diet. Graded levels of phytase resulted in linear increases in ADG (P < .02), ADFI (P < .01 at .16% aP only), and gain:feed ratio (P < .03). Effects of adding phytase to the diet with .32% aP were observed only in the first 14 d of the study with increases in ADG (P < .06) and gain:feed (P < .02) for added phytase. Apparent digestibility (or absorption) coefficients (ADC) of DM, P, Ca, and N were estimated using chromic oxide as an indicator during wk 4 and 5. When phytase and P were added to the low P diet, the ADC of P was increased (P < .01), but only small and variable changes in the ADC of DM, Ca, and N were observed. Fecal P excretion (grams per day) decreased as microbial phytase was added (P < .01) and increased with added P (P < .01). In comparison to the results with the .32% aP diet, fecal P excretion decreased 25 to 50% by the addition of phytase. The addition of phytase to the diet with .32% aP further improved (P < .01) the ADC of P (54.5 vs 61.8%) and decreased (P < .01) fecal P excretion (1.62 vs 1.38 g/d). Characteristics of 4th metacarpals and 10th ribs were consistently improved by increasing dietary levels of both phytase and P. On the basis of an assessment of R2 values from secondorder translog equations, ADG, ADFI, P apparent absorption, bone ash percentage, and bone shear force were sensitive indicators to evaluate phytase efficacy of P availability in diets. Phosphorus equivalency of microbial phytase was calculated by using response equations for ADG and apparent P absorption. The average function of the release of P (Y, grams per kilograms) by microbial phytase (X, units per kilogram of diet) was developed with aP levels of .05 and .16%: Y = 1.546-1.504e-.0015X. The replacement of 1 g of inorganic P would require about 676 U of microbial phytase. This represents 77% of released P from phytate.

6-Phytase↗
PubMed1996

Improving phytate phosphorus availability in corn and soybean meal for broilers using microbial phytase and calculation of phosphorus equivalency values for phytase.

Two experiments were conducted to determine the effectiveness of Natuphos phytase for improving P availability of soybean meal-based semipurified diets (SP, Experiments 1 and 2) and corn-soybean meal-based diets (CS, Experiment 2) fed to broilers (1 to 21 d). There were 360 and 288 birds fed the SP diets in Experiments 1 and 2, respectively, and 288 birds were fed the CS diets in Experiment 2. Phosphorus equivalency values for phytase were calculated. The basal diets were formulated to contain 0.27% nonphytate P (nP); the SP basal diet contained 0.45% total P (tP) that included 0.17% P as defluorinated phosphate; the CS basal diet contained 0.51% tP that contained 0.12% P as defluorinated phosphate. Both basal diets were supplemented with defluorinated phosphate to provide 0.36, 0.45, of 0.54% nP or with 350, 700, or 1,050 U of phytase/kg diets. Supplementing defluorinated phosphate and phytase linearly increased BW gain (P < 0.001), feed intake (P < 0.001), and percentage ash of dried toes (P < 0.01). Phytase addition increased apparent retention of P (P < 0.02), Ca (P < 0.005 in Experiment 2), and N (P <0.06 in Experiment 2 for CS), increased apparent digestibility of DM (P < 0.04), and linearly decreased (P <0.005) P excretion. In comparison to the 0.45% np diet, P excretion was reduced 42 to 51% by addition of phytase. The addition of defluorinated phosphate linearly decreased apparent retention of P (P < 0.02) and Ca (P < 0.005 in Experiment 2), and increased P excretion (P < 0.007). The average of released P by phytase calculated by solving nonlinear or linear response equations of P and phytase levels for SP diets in Experiments 1 and 2 gave a P equivalency value 1 g P = 1,146 U of phytase. The P equivalency value for CS diets fed only in Experiment 2 was 785 U of phytase = 1 g P as defluorinated phosphate. These studies show that microbial phytase is effective for improving P availability and for decreasing P excretion. Added phytase can also increase Ca and N retention.

6-Phytase↗
PubMed1996

Effects of supplemental phytase and phosphorus on histological and other tibial bone characteristics and performances of broilers fed semi-purified diets.

Two trials with day-old chicks were conducted to investigate the effects of supplemental phytase (Natuphos) on histological, mechanical, and chemical properties of tibia, and performances of broilers fed semi-purified diets containing soybean meal as the only organic P source [0.11% nonphytate P (nP)]. Dietary treatments in Trial 1 were: 1) 0.20% nP, 2) Diet 1 + 800 U of phytase/kg of diet, 3) 0.27% nP, 4) Diet 3 + 600 U of phytase, 5) 0.34% nP, 6) Diet 5 + 400 U of phytase. Supplemental phytase and inorganic P increased tibial length (P < 0.01), shear force (P < 0.001), shear stress (P < 0.05), ash content (P < 0.001), and BW gain and feed intake (P < 0.001) during Trial 1. The hypertrophic zone width at the proximal end of the tibia was decreased (P < 0.05), and the tibial width (P < 0.05) of the long axis of the tibia was increased by the phytase and P supplementation. Supplemental phytase enlarged the cartilaginous and proliferative zones of the tibial proximal end (P < 0.05), and an increase in nP levels produced similar effects. Supplementation of phytase and P also tended to improve the orderliness of development and arrangement of cartilage and bone cells. Dietary treatments in Trial 2 were: 1) 0.27% nP, 2) Diet 1 + 350 U of phytase, 3) Diet 1 + 1,050 U of phytase, 4) 0.45% nP, 5) 0.54% nP, 6) Diet 5 + 1,050 U of phytase. Broilers fed diets containing relatively high levels of nP and phytase supplementation in Trial 2 gave results similar to those observed in Trial 1. Marked improvements (P < 0.05) in the ash content, shear force, shear stress, length of tibia, BW gain, and feed intake, and reduced hypertrophic zone width were achieved for broilers fed the P-deficient diet supplemented with phytase. Also, supplemental phytase tended to increase the width of cartilaginous and proliferative zones, to increase trabecular bone density, and to improve the orderliness of development and mineralization of cartilage and bone cells. In summary, supplementing a low-nP diet with inorganic P or phytase resulted in similar beneficial effects on bone development.

6-Phytase↗
PubMed1996

Additivity of apparent and true ileal amino acid digestibilities in soybean meal, sunflower meal, and meat and bone meal for broilers.

An experiment was conducted to determine the additivity of apparent and true ileal amino acid digestibility values in soybean meal (SBM), sunflower meal (SFM), and meat and bone meal (MBM). A total of 63 individually caged 5-wk-old broilers were assigned to seven groups and given semi-purified diets containing SBM, SFM, MBM, and their combinations. True digestibilities were estimated by using the homoarginine in guanidinated proteins as the marker. Additivity was tested by comparing the differences between the observed digestibilities of ingredient combinations and the predicted values from measurements with individual ingredients. In general, for both apparent and true digestibilities, there were no significant differences (P > 0.05) between the observed and predicted values in ingredient combinations. The only exception was SBM + MBM combination, in which the observed values for apparent digestibilities of aspartic acid, serine, glutamic acid, isoleucine, and tyrosine were significantly higher (P < 0.05) than the predicted values. Overall, the present results indicate that amino acid digestibility values are additive and that digestible amino acid supply in a complete diet can be predicted from amino acid digestibilities of individual ingredients.

Amino Acids↗
PubMed1995

Evaluation of a layer diet formulated from non-conventional feedingstuffs.

1. A layer diet, the formulation of which was based on several non-conventional feedingstuffs, was evaluated at the research station and under small farm conditions in Sri Lanka. The new feedingstuffs included finger millet, rice polishings, rubber seed meal, cassava leaf meal, ipil ipil leaf meal and dried poultry manure. A commercial mash, that is normally used on the farm, served as the control. 2. The performance and egg quality characteristics were similar between the test and control diets, the only exception being the egg yolk colour which was improved (P < 0.05) by feeding the test diet. Food cost per dozen eggs was lowered by feeding the test diet. 3. It is possible to formulate layer diets using non-conventional feedingstuffs, achieve acceptable production and lower the food costs under small farm conditions in tropical developing countries.

Animal Feed↗
PubMed1995

Bioavailability of phosphorus in various phosphate sources using body weight and toe ash as response criteria.

The relative bioavailability values of P from seven sources were determined using male chickens fed a basal corn-soybean meal diet (.40% total P and 1.10% Ca) with varying levels of test and standard phosphates from 0 to 3 wk of age. Each of seven test phosphates was added to the basal diet at .05, .08, .12, .17, .23, and .32% levels. In addition, standard diets were formulated by adding the same levels of P plus .44 and .60% levels from dicalcium phosphate dihydrate (CaHPO4.2H2O) to the same basal diet. Each of the 42 test diets was fed to two pens of 10 chicks each, and each of the standard diets was fed to six pens of 10 chicks each. Three-week body weight gain and percentage ash of dried toe data were fitted with nonlinear (asymptotic and sigmoidal) regression equations, and the ratios of regression coefficients were used to determine the bioavailability of various test phosphates relative to the reference standard. Based on the asymptotic regression equation of body weight gain and on the sigmoidal regression equation of toe ash on the percentage of P added to the diets from the seven phosphate sources, the average relative bioavailability of the P (compared with the standard given a value of 100%) was as follows: Lucaphos-48, 88.4%; Lucaphos-40, 95.1%; Rukana, 83.7%; Cefkaphos-N, 104.8%; phosphoric acid, 93.0%; monocalcium phosphate monohydrate [Ca(H2PO4)2.H2O], 111.8%; and Biophos, 92.0%. A difference of 7.7% units for the average bioavailability of the P was required for significance (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1995

An evaluation of various response criteria in assessing biological availability of phosphorus for broilers.

The relative bioavailability of P from seven sources was determined in relation to a standard dicalcium phosphate dihydrate (CaHPO4.2H2O) in a 21-d assay involving 1,320 broiler male chicks using several response criteria. The seven sources (Lucaphos-48, Lucaphos-40, Rukana, Cefkaphos-N, phosphoric acid, monocalcium phosphate monohydrate, or Biophos) were added to the basal diet (.40% total P and 1.10% Ca) at levels to supply .05, .08, .12, .17, .23, and .32% P. Two additional levels (.44 and .66%) of P from dicalcium phosphate dihydrate were included for the standards. The criteria selected to evaluate included tibia ash, tibia specific gravity, tibia shear force, toe shear force, and metatarsal shear force. Other criteria: weight, length, diameter, and volume of tibia; weight, volume, and specific gravity of metatarsus; and weight, volume, and specific gravity of toe were not selected because their response to increasing P levels were inconsistent and quite variable. Nonlinear (asymptotic and sigmoidal) regression equations were fitted to the data than linear equations. The ratios of regression coefficients were used to determine the bioavailability of various test phosphates relative to the reference standard. The results indicated that the response criteria used for the determination will considerably influence the relative bioavailability estimates of a P source. Body weight gain and toe ash percentage were found to be an equally or a more sensitive criteria for assessment of P availability than tibia ash. Tibia specific gravity, tibia shear force, toe shear force, and metatarsal shear force were of limited value as response criteria in P bioavailability assays based on standard error and difference required for significance.

Animals↗
PubMed1995

Improving phosphorus availability in soybean meal for broilers by supplemental phytase.

A 21-d experiment was conducted with day-old male broilers (n=840) to evaluate the effectiveness of supplemental phytase for improving the availability of phytate P in soybean meal when varying levels of P were fed. The semi-purified basal diet (.18% phytate P) contained soybean meal as the only protein source. Seven levels of phytase (0, 200, 400, 600, 800, 1,000, and 1,200 U/kg diet) were added to diets formulated to contain .20, .27, or .34% nonphytate P (nP; or .38, .45, and .52% total P, respectively). The desired levels of nP in the three basal P diets were achieved by adding varying amounts of defluorinated phosphate. A 2:1 Ca:total P ratio was maintained in all diets. Body weight gains and feed intake were improved (P < .001) by phytase at all nP levels, but the magnitude of response was greatest at low nP levels, resulting in an nP by phytase interaction (P < .01). Gain:feed was unaffected by phytase addition. A high mortality (35 to 45%) was observed for the .20 and .27% nP diets without added phytase, but this declined to normal levels with the addition of 200 to 400 U phytase/kg diet. Ash percentage of toes and tibia and shear force and stress of tibia increased with added phytase. These responses clearly show that the phytate-bound P in soybean meal was made more available to broilers by microbial phytase, and the total response was related to the phytase and nP/total P levels. Based on the high R2 values for the second order translog equations, BW gain, feed intake, and toe ash percentage were the most sensitive indicators to assess P availability, followed by tibia force and ash percentage. Derived nonlinear and linear equations for BW gain and toe ash percentage at the two lower nP levels were used to calculate P equivalency values of phytase for inorganic P. Using the average function of P released ( gamma ) by microbial phytase ( chi ) derived with nP levels of .20 and .27% for BW gain and toe ash percentage, gamma = 1.120 - 1.102e-.0027chi, 1 g of P could be released with 821 U of phytase. The amount of P released increased with increasing levels of phytase, but the amount of P released per 100 U of phytase decreased. Released P ranged from 31 to 58% of phytate P for 250 to 1,000 U of phytase/kg of diet.

6-Phytase↗
PubMed1995

Response of turkey poults to tiered levels of Natuphos phytase added to soybean meal-based semi-purified diets containing three levels of nonphytate phosphorus.

A 3-wk feeding trial using 920 day-old turkey poults was conducted to evaluate the addition of seven levels of phytase (Natuphos; 0, 200, 400, 600, 800, 1,000, and 1,200 U/kg of diet) to diets containing three levels of nonphytate P (nP) (.27, .36, and .45%). A positive control diet contained .60% nP. Semi-purified basal diets contained soybean meal as the only protein source. The increase in BW gain from added phytase was greatest for the lowest nP diet (nP by phytase interaction, P < .001). At .27% nP, gains improved (P < .001) to 800 U of phytase/kg of diet and then reached a plateau. At .36 and .45% nP, increases in gains were observed only for 200 U of phytase/kg of diet. The highest phytase addition to.36 and .45% nP diets produced gains equal to those of the positive control diet. Feed intake increases paralleled those of BW gains. Gain:feed was lowest for the .27% nP diets without phytase, but improved (P < .001) to 800 U of phytase/kg of diet and then reached a plateau. The high incidence of leg disorders and high mortality (40%) observed for the poults fed the .27% nP diet without added phytase declined with the addition of 200 to 400 U of phytase/kg of diet. Ash percentage of toes and tibias increased as the levels of nP (P < .001) and phytase (P < .01) increased; the magnitude of the response to phytase decreased as nP in the diet increased, resulting in an nP by phytase interaction (P < .001). Tibial shear force and stress responded in a similar manner to increasing levels of nP and added phytase. Results show that 652 U of microbial phytase is equivalent to 1 g of P from defluorinated phosphate in turkey starter diets using soybean meal as the only source of phytate P. The response per 100 U of phytase decreased as the total amount of phytase added was increased.

6-Phytase↗
PubMed1994

Effects of diet acidity and protein level or source of calcium on the performance, gastrointestinal content measurements, bone measurements, and carcass composition of gilt and barrow weanling pigs.

A total of 228 crossbred weanling pigs (average age of 25 d and BW of 6.44 kg) were used in two trials to evaluate the responses to sex, diet acidity, protein level, and source of calcium on the performance, gastrointestinal digesta measurements, bone measurements, and carcass composition. Diet acidity was manipulated by varying the sources of supplemental phosphorus in the diets. Trial 1 (5 wk) was conducted as a 2 x 3 x 2 factorial to evaluate sex (gilts and barrows), diet acidity (pH 5.9 and .90% P, pH 6.1 and .63% P, and pH 6.9 and .63% P), and level of protein (16 and 22% CP). In Trial 2 (6 wk), diet acidity (pH 5.5, 5.9, and 6.8, all with .7% P) and Ca sources (CaCO3 and CaSO4) were used with gilts and barrows. The sex x diet acidity interactions were significant for ADG in both trials. Barrows seemed to respond to both the more acidic diets and the buffered phosphate diets even though the pH was less acidic than that of the unbuffered diets. Gilts responded only to the more acidic diets. In Trial 1, gilts ate more and grew faster (P < .05) than barrows, but no sex effects on performance were observed in Trial 2. Pigs fed 22% CP diets grew faster (P < .001) and more efficiently (P < .001) than did pigs fed 16% CP diets, but protein level x diet acidity and protein level x sex interactions were not significant. Stomach digesta DM, pH, and titration value were not consistently influenced by sex and diet acidity in Trials 1 and 2, by protein level in Trial 1, and by calcium source in Trial 2. Only the sex x diet acidity interaction for stomach DM tended to be significant in both trials; gilts fed the less acidic diets had the lowest DM, whereas barrows fed the more acidic diets had the lowest DM values. Although not significant in every case in both trials, bone (average of metacarpal and metatarsal) volume was lower and specific gravity and shear stress values were higher for gilts than for barrows. Pigs fed 16% CP diets had higher specific gravity (P < .05) and stress (P < .06) values than pigs fed 22% CP diets. A protein level x diet acidity interaction (P < .03) for stress suggested that pigs fed 22% CP diets were unaffected by diet acidity, whereas pigs fed 16% CP had the highest stress values when fed the more acidic diet and the lower P level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗