Nutritional evaluation of low phytate and high protein corns.

Three chick experiments and two cecectomized rooster experiments were conducted to determine P bioavailability and amino acid (AA) digestibility in two low phytate corns (LP), a high protein corn (HP), and a corn containing both low phytate and high protein content (HP/LP) compared with conventional corn (CONV). From 8 to 20 or 21 d of age, 1-wk-old New Hampshire x Columbian chicks were fed a cornstarch-dextrose-soybean meal (SBM) basal diet containing 0.10% available P or the basal diet supplemented with two concentrations of P (0.05 or 0.06% and 0.10 or 0.12%) from KH2PO4 or two concentrations of the corns (20 or 21% and 40 or 42%). Bioavailability of P based on tibia bone ash was much higher for LP than for CONV; values ranged from 21 to 40% for CONV and from 59 to 95% for LP. Digestibility of AA in cecectomized roosters indicated no significant differences (P > 0.05) between CONV and HP in the first rooster experiment. Digestibilities of eight AA, including lysine, methionine, and arginine, in LP and HP/LP were higher (P < 0.05) than those in CONV in the second rooster experiment. The results of this study indicated that the P in LP was two to three times more bioavailable than the P in CONV and that the digestibilities of AA in HP/LP were equal to or higher than those in CONV.

Citric acid does not improve phosphorus utilization in laying hens fed a corn-soybean meal diet.

Data previously obtained from our laboratory have indicated that citric acid was very effective at improving phytate-P utilization in chicks fed a P-deficient corn-soybean meal (SBM) diet. The objective of the current study was to determine if citric acid would have similar effects in a commercial strain of Single Comb White Leghorn laying hens (n = 432) fed a corn-SBM diet containing 0.10% available P (AP). Dietary treatments were a corn-SBM basal diet (0.10% AP, 3.8% Ca, and 17% CP) supplemented with 0, 1, 2, 3, or 4% citric acid and a positive control diet containing 0.45% AP. Each of the six dietary treatments were fed to six replicate groups of 12 hens from 22 to 40 wk of age. No significant differences in performance were observed among treatments during the first 4 wk of the experiment. Hen-day egg production, feed consumption, feed efficiency, and egg yield were subsequently depressed in hens fed 0, 1, 2, 3, or 4% citric acid compared with hens fed 0.45% AP. The results of this study indicate that citric acid does not improve the utilization of dietary P in laying hens fed a corn-SBM diet containing 3.8% Ca.

The effects of various dietary levels of phytase and available phosphorus on performance of laying hens.

Data previously obtained from our laboratory indicated that addition of 300 U of phytase/kg diet supported optimal long-term performance of laying hens (20 to 70 wk) fed a corn-soybean meal (SBM) diet containing 0.10% available phosphorus (AP). Our primary objective was to determine if a phytase level lower than 300 units/kg is adequate for a commercial strain of Single Comb White Leghorn laying hens (n = 504) fed a corn-SBM diet containing no supplemental P (0.10% AP). Dietary treatments consisted of the corn-SBM basal diet (0.10% AP, 3.8% Ca, and 17% CP) supplemented with 0, 100, 200, 250, or 300 U of phytase/kg, 0.05% inorganic P (0.15% AP), and a positive control diet containing 0.45% AP. Each of the seven dietary treatments was fed to six replicate groups of 12 hens from 20 to 60 wk of age. No significant differences in performance were observed among treatments during the first 8 wk of the experiment. By 28 wk of age, the 0.10% AP diet, with no supplemental phytase or P, resulted in significantly lower (P < 0.05) egg production and body weight compared with all other dietary treatments. Feed consumption, feed efficiency, and egg yield were subsequently depressed by 32 wk of age in hens fed the 0.10% AP diet. No other significant differences among treatments were observed for performance averaged over the entire 40-wk experimental period. The mean daily AP intake of hens fed the 0.15% AP, 0.45% AP, and 0.10% AP + phytase diets was 155, 474, and 103 mg, respectively. The results of this study indicate that phytase improves the utilization of P in corn-SBM diets for laying hens and that corn-SBM diets containing 0.10% AP + 100 units of phytase/kg diet or 0.15% AP supported egg production performance that was not significantly different (P > 0.05) from that of hens fed a corn-SBM diet containing 0.45% AP.

The effects of citric acid on phytate-phosphorus utilization in young chicks and pigs.

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.

The effects of dietary available phosphorus levels and phytase on performance of young and older laying hens.

In the first of two experiments (20 to 70 wk of age), eight treatments consisted of corn-soybean meal diets (0.34% total P, 3.8% Ca, 17% CP, 2,758 kcal ME/kg) containing 0.10, 0.15, 0.20, 0.25, or 0.45% available P (AP), with the three lowest AP diets supplemented with 300 units of phytase/kg of diet. A second experiment evaluated the effect of feeding the 0.10% AP diet with and without phytase on performance and time required for onset of P deficiency in older hens (70 to 76 wk of age). In Experiment 1, the 0.10% AP diet with no supplemental phytase depressed performance by 28 wk of age. No other significant differences in performance were observed among treatments for the entire 20- to 70-wk period except that the 0.15% AP diet with no phytase resulted in body weights and tibia ash that were lower (P < 0.05) than those of hens fed the 0.45% AP diet during the last 30 wk. The mean daily AP intake of hens fed the 0.10% AP, 0.15% AP, 0.45% AP, or 0.10% AP + phytase diets was 94,159, 499, or 108 mg, respectively. Excreta P concentration was decreased by approximately 50% in birds consuming 0.10% AP + 300 U/kg phytase compared with those consuming 0.45% AP. In the second experiment, P deficiency signs occurred within 3 wk of consuming the unsupplemented corn-soybean meal diet (0.10% AP) compared with 8 wk in Experiment 1. The results of this study indicate that phytase improves P utilization in corn-soybean meal diets for laying hens and that a corn-soybean meal diet containing 0.15% AP (159 mg AP/d) or containing 0.10% AP + 300 units of phytase/kg (108 mg AP/d) supported optimal egg production from 20 to 70 wk of age. Additionally, results suggested that older hens may exhibit P deficiency symptoms sooner than younger hens.

Bioavailability of lysine from a liquid lysine source in chicks.

Two experiments were conducted to assess the bioavailability of lysine from a liquid lysine product (LLP; 60% lysine) relative to crystalline L-lysine.HCl. In the first experiment, four groups of five chicks were fed a lysine-deficient basal diet containing corn, soybean meal, and feather meal or the basal diet supplemented with 0.1 or 0.2% lysine from L-lysine.HCl or LLP from Day 8 to 22 posthatching. Weight gain and feed efficiency responded linearly (P < 0.01) to increasing levels of lysine from either lysine source, and multiple linear regression analysis of weight gain regressed on supplemental lysine intake indicated no difference (P > 0.05) in the response to lysine from L-lysine.HCl or LLP. Experiment 2 was conducted using a lysine-deficient basal diet containing corn, peanut meal, and feather meal, and all diets were fed to five groups of five chicks from Day 8 to 21 posthatching. Treatment additions again consisted of 0.1 or 0.2% lysine from L-lysine.HCl or LLP. Weight gain and feed efficiency responded linearly (P < 0.01) to increasing levels of lysine from L-lysine-HCl and LLP, and multiple linear regression analysis of weight gain regressed on supplemental lysine intake indicated no difference (P > 0.05) in the response to lysine from L-lysine.HCl or LLP. These data indicate that lysine from LLP is fully bioavailable relative to lysine from crystalline L-lysine.HCl, and could therefore be used as a source of lysine in practical poultry diets.

Bioavailability of zinc in two zinc sulfate by-products of the galvanizing industry.

Two Zn depletion/repletion assays were conducted with chicks to determine the relative bioavailability (RBV) of Zn from two new by-products of the galvanizing industry. Using a soy concentrate-dextrose diet, slope-ratio methodology was employed to evaluate two different products: Fe-ZnSO4 x H2O with 20.2% Fe and 13.0% Zn, and Zn-FeSO4 x H2O with 14.2% Fe and 20.2% Zn. Feed-grade ZnSO4 x H2O was used as a standard. Weight gain, tibia Zn concentration, and total tibia Zn responded linearly (P < 0.01) to Zn supplementation from all three sources. Slope-ratio calculations based on weight gain established average Zn RBV values of 98% for Fe-ZnSO4 x H2O and 102% for Zn-FeSO4 x H2O, and these values were not different (P > 0.10) from the ZnSO4 standard (100%). Slope-ratio calculations based on total tibia Zn established average Zn RBV values of 126% for Fe-ZnSO4 x H2O and 127% for Zn-FeSO4 x H2O, and these values were greater (P < 0.01) than those of the ZnSO4 standard (100%). It is apparent that both mixed sulfate products of Fe and Zn are excellent sources of bioavailable Zn.

Bioavailability of iron in cottonseed meal, ferric sulfate, and two ferrous sulfate by-products of the galvanizing industry.

Iron depletion-repletion assays were carried out with young chicks to establish Fe bioavailability values for Fe2(SO4)3.7H2O (22.7% Fe), Fe-ZnSO4.H2O (20.2% Fe, 13.0% Zn), Zn-FeSO4.H2O (20.2% Zn, 14.2% Fe), and cottonseed meal (200 mg Fe/kg). Standard hemoglobin response curves were established using feed-grade FeSO4.H2O (28.8% Fe) or reagent-grade FeSO4.7H2O (20.1% Fe) as standards such that relative bioavailability (RBV) could be assessed for the experimental sources of Fe. Weight gain, hemoglobin, and hematocrit responded linearly (P < 0.05) to Fe supplementation in all assays. Using hemoglobin as the response criterion, slope-ratio calculations established Fe RBV values of 126% for Fe-ZnSO4.H2O and 93% for Zn-FeSO4.H2O. The 126% value for Fe-ZnSO4.H2O was greater (P < 0.05) than the FeSO4.H2O standard (100%), but the 93% value for Zn-FeSO4.H2O was not different (P > 0.10) from the standard. However, evaluation of all criteria of response (hemoglobin, hematocrit, weight gain) suggested that neither Fe-ZnSO4.H2O nor Zn-FeSO4.H2O had different Fe RBV values than FeSO4.H2O. Standard-curve calculations were used for assessment of Fe RBV in Fe2(SO4)3.7H2O and cottonseed meal, as only a single level of Fe addition was studied for each of these products. Iron RBV in Fe2(SO4)3.7H2O was estimated to be 37%, whereas Fe RBV in cottonseed meal was found to be 56%. Both of these values were lower (P < 0.05) than the FeSO4 standard. The data suggest that the two new products, representing combinations of FeSO4.H2O and ZnSO4.H2O by-products of the galvanizing industry, are excellent sources of bioavailable Fe, whereas ferric sulfate and cottonseed meal are relatively poor sources of usable Fe.

Digestible lysine requirement of female turkeys during the starter period.

Three experiments were conducted to determine the digestible lysine requirement of female turkey poults during the starter period. Birds were fed a standard corn-soybean meal diet until the onset of each trial and were then randomly assigned to treatments that were fed for 2 wk. Dietary treatments included titrated levels of digestible lysine (1.18 to 1.72%) added to a basal corn-soybean meal diet with an intact crude protein content of either 21% (Experiment 1) or 18.4% (Experiments 2 and 3). All diets contained 3,100 to 3,200 kcal MEn/kg. True digestible lysine contents of the basal diets were 1.42% (Experiment 1) and 1.18% (Experiments 2 and 3), based on digestibility assays of corn and soybean meal with cecectomized turkeys. A positive control diet (28% CP, 3,175 kcal MEn/kg) was also included in the treatments for comparison. Other amino acids were maintained at levels in relation to lysine based on previous research and the Illinois Ideal Chick Protein. Broken-line analysis suggests that the digestible lysine requirement is 1.32% for optimum body weight gain and 1.34% for optimal feed:gain at the energy levels used in these studies.

Lysine: Ideal protein in turkeys.

This paper will review current and previous research related to our work on ideal proteins for turkeys. The concept of ideal protein is not new, but has not been researched in turkeys to any extent. Ideal proteins may be defined as the exact balance of amino acids needed for maximal growth. Ideal proteins are based on digestible amino acids. Several pieces of information need to be in place before one can actually run an experiment on the digestible amino acid requirements and ideal protein. The first of these is data on digestible amino acid content of feedstuffs for turkeys. The second necessity is a low protein diet that can be used to titrate the amino acids on a digestible basis. These requirements led us to formulate a very low protein starter diet (approximately 18% intact crude protein + amino acids) with corn and soybean meal that would support maximal growth. To formulate a diet at this crude protein level, it was necessary to use the ideal protein research from other species and previous research with turkeys. We now have an estimate of the ideal protein for turkeys. The future of this work and amino acid nutrition of turkeys will be reviewed.

A low-protein diet for turkey poults.

A series of studies was conducted to determine whether a low-protein corn-soybean meal diet would support growth of turkeys similar to that supported by a standard diet. Three treatments administered in a series of experiments included: basal diet with essential amino acids (EAA), NaHCO3, and glutamic acid added at the expense of sucrose to bring the total protein up to 28% (+GLU); basal diet with EAA, NaHCO3, and sucrose added to bring the total protein content to 22% (+SUC); and a 28% crude protein standard diet that meets or exceeds NRC recommendations using intact protein sources (ST). Essential amino acid levels used in the experimental diets were based on an estimated ideal protein ratio for turkeys. The basal diet contained 18.4% intact CP from corn and soybean meal. All treatments were isocaloric with 3,172 to 3,192 kcal/kg. In all trials, the birds receiving +GLU and +SUC had adequate growth and feed:gain responses compared to birds receiving ST. The low protein basal diet with appropriate amino acid supplementation will allow for amino acid titrations to determine digestible amino acid requirements.

Digestible sulfur amino acid requirement of starting turkeys.

Three experiments (a total of 1,020 poults) were conducted to determine the digestible sulfur amino acid (SAA) requirement for female turkey poults during the starter period. Poults were fed a standard corn-soybean meal diet (PC) that met or exceeded NRC recommendations (28% CP, 3,172 kcal MEn/kg) for 1 wk and were then randomly assigned to treatments until 22 d (Experiment 2 and 3) or 23 d (Experiment 1) of age. Dietary treatments included the PC diet and seven or nine titrated levels of methionine added to a basal corn-soybean meal diet, for a total of 0.50 to 1.33% total digestible SAA. The basal diet contained 18.4% intact crude protein. All diets contained 3,171 kcal MEn/kg. The true digestible SAA content of the basal diet without methionine additions was 0.50% based on digestibility assays of the corn and soybeans with cecectomized turkeys. Diets were formulated to contain 1.40% digestible lysine. Other amino acids were maintained at levels in relation to lysine based on previous research with turkeys and the Illinois Ideal Chick Protein. Broken-line analysis suggests that the digestible SAA requirement for female turkeys during the starter period is 0.76% for optimum body weight gain and 0.75% for optimal feed:gain at the energy levels used in these studies.