Published January 23, 2015
Effects of dietary true digestible calcium to phosphorus ratio on growth performance and efficiency of calcium and phosphorus use in growing pigs fed corn and soybean meal-based diets1,2 M. Z. Fan2 and T. Archbold Center for Nutrition Modeling, Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada N1G 2W1
ABSTRACT: Objectives of this study were to determine effects of dietary true fecal digestible Ca to true digestible P ratio on growth performance and efficiency of Ca and P use in growing pigs fed corn (Triticum aestivum)–soybean (Glycine max) meal (SBM)-based diets. Experiment 1 was carried out to measure true fecal digestibility of Ca and P as well as the fecal endogenous outputs of these nutrients associated with a corn and SBM-based diet in 12 Yorkshire growing pigs with an average initial BW of 23.2 ± 0.6 kg by the substitution method. True fecal digestibility values (%; n = 6) of Ca (53.6 ± 12.7) and P (43.8 ± 16.7) as well as the fecal endogenous outputs (g/kg DMI; n = 12) of Ca (0.91 ± 0.20) and P (1.31 ± 0.15) associated with the diets were determined. Experiment 2 was conducted with 36 Yorkshire barrows of an average initial BW of 24.2 ± 0.6 kg and the pigs were fed 6 diets according to a completely randomized block design. The 6 diets were corn and SBM based with diet 1 containing 0.2% true digestible Ca and 0.3% true digestible P and were
formulated to contain 6 total Ca to total P ratios based on analyzed dietary Ca and P contents (diet 1, 0.6:1; diet 2, 0.7:1; diet 3, 0.8:1; diet 4, 1.3:1; diet 5, 1.0:1; and diet 6, 1.3:1) by supplementing gradient levels of limestone with a constant dietary P content for meeting the recommended requirement. Changes in the dietary Ca to P ratio had no effects (P > 0.05) on ADG. No differences (P > 0.05) in ADFI were observed between the other diets except the lower ADFI (P < 0.05) in diet 3 compared with diet 2. However, G:F was higher (P < 0.05) in diet 2 compared with diets 5 and 6. Changes in the dietary Ca to P ratio had consistent effects on true fecal P digestibility and retention with much lower values (P < 0.05) observed in diet 5 in comparison with the other diets. In summary, true fecal digestible Ca to P ratios of 0.9:1 to 1.0:1 were associated with optimal responses in both G:F as well as true fecal P digestibility and retention in growing pigs fed corn and SBM-based diets.
Key words: calcium to phosphorus ratio, endogenous Ca and P losses, growing pigs © 2012 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2012.90:254–256 doi:10.2527/jas54005 INTRODUCTION Bioavailability of Ca and P in feed ingredients and inorganic P supplements are classically determined by using the apparent fecal digestibility studies and the slope-ratio assay in pigs (Jongbloed et al., 1991). True P digestibility and the fecal endogenous P outputs have 1 Related research activities have been supported by grants (to M.Z.F.) from Ontario Pork Producers’ Marketing Board (OPPMB – Ontario Pork), and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)-the University of Guelph Partnership Research Program. 2 Ntinya Johnson participated in the animal study and sample collection activities. 2 Corresponding author:
[email protected]
been determined in a number of feed ingredients and inorganic P supplements for pigs by using the regression analysis, the P-free feeding, and the substitution method in the past decade (Fan et al., 2008). These studies have shown that apparent fecal P digestibility and P availability values are much variable and considerably underestimate true P bioavailability in feed ingredients and inorganic P supplements for pigs (Fan et al., 2008). Diet formulation for swine should be based on true fecal Ca and P digestibility values measured in feed ingredients. Therefore, objectives of this study were to examine effects of changes in dietary true digestible Ca to true digestible P ratio on growth performance and efficiency of Ca and P use in growing pigs fed corn and
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Table 1. Dietary composition of Exp. 1 for examining the effect of dietary Ca to P ratios on growth performance and efficiency of Ca and P use in growing pigs fed corn and soybean meal-based diets (%, as-fed basis) Item
Diet 1
Diet 2
Diet 3
Diet 4
Diet 5
Diet 6
Soybean meal 27.07 27.07 27.07 27.07 27.07 27.07 Corn 66.00 66.00 66.00 66.00 66.00 66.00 Cornstarch 3.87 3.29 2.71 2.13 1.55 0.97 78% l-Lys HCl 0.17 0.17 0.17 0.17 0.17 0.17 l-Thr 0.05 0.05 0.05 0.05 0.05 0.05 Animal fat 0.50 0.80 1.10 1.40 1.70 2.00 Iodized salt 0.40 0.40 0.40 0.40 0.40 0.40 Limestone 0.28 0.56 0.84 1.12 1.40 1.68 Dicalcium phosphate 0.86 0.86 0.86 0.86 0.86 0.86 Vitamin–mineral premix1 0.50 0.50 0.50 0.50 0.50 0.50 Titanium oxide2 0.30 0.30 0.30 0.30 0.30 0.30 Total, kg 100.00 100.00 100.00 100.00 100.00 100.00 Nutritive values (on as-fed basis) DM,3 % 87.55 87.65 87.84 87.80 88.13 88.08 DE,4 MJ/kg 14.54 14.56 14.57 14.58 14.59 14.61 CP,4 % 17.33 17.33 17.33 17.33 17.33 17.33 Total Ca,3 % 0.40 0.43 0.51 0.67 0.59 0.73 Total P,3 % 0.67 0.58 0.63 0.53 0.59 0.55 From Roche Vitamins Canada Inc., Cambridge, ON, Canada, for supplying the required trace minerals and vitamins according to NRC (1998). Titanium oxide used as a digestibility marker; Fisher Scientific, Fair Lawn, NJ. 3 Analyzed values. 4 Calculated according to NRC (1998). 1 2
soybean meal (SBM)-based diets. MATERIALS AND METHODS Twelve Yorkshire barrows with average initial and final BW of 23.2 ± 0.6 and 31.1 ± 0.6 kg in Exp. 1 and 36 Yorkshire barrows with average initial and final BW of 24.2 ± 0.3 kg and 33.8 ± 0.5 kg in Exp. 2 were acquired from the University of Guelph Arkell Swine Research Station and were managed according to previous studies (Rideout et al., 2008). In Exp. 1, a normal-nutrient diet (diet 1) was corn and SBM based (Table 1) and a lownutrient diet was formulated by replacing corn and SBM in diet 1 with 25.52% corn starch. Thus, the 2 diets were formulated to contain 2 levels (on as-fed basis) of CP
(17.33 and 12.13%), Ca (0.54 and 0.29%), and P (0.54 and 0.39%). In Exp. 2, 6 corn and SBM-based diets were formulated to contain 6 levels of total Ca to total P ratios by supplementing graded levels of limestone with dietary P and other nutrients meeting the NRC (1998) requirements (Table 1). Titanium oxide was used as a digestibility marker in both experiments. Experiment 1 was conducted according to a completely randomized design. Experiment 2 was conducted according to a completely randomized block design for 6 experimental blocks. Each experimental block lasted for 15 d with 10 d of adaptation and 5 d of sample collection. Initial and final BW and ADFI were recorded. Representative fresh fecal samples were collected at 2-h intervals in the daytime between days 11 and 15. Samples
Table 2. The effect of dietary Ca to P ratios on growth performance and efficiency of Ca and P use in growing pigs fed corn and soybean meal-based diets Item
Diet 1
Diet 2
Diet 3
Diet 4
Diet 5
Diet 6
SEM1
Total Ca to P ratio True digestible Ca to P ratio ADFI, kg/(pig∙d) ADG, kg/(pig∙d) Gain to feed ratio, kg/kg Total Ca intake, g/(pig∙d) Total P intake, g/(pig∙d) True Ca retention, g/(pig∙d) True P retention, g/(pig∙d) True Ca digestibility, % True P digestibility, % True Ca retention, % True P retention, %
0.6:1 0.7:1 1.24a 0.69 0.56ac 4.91a 7.26a 1.78a 2.69a 53.44a 43.06a 37.61ab 37.37a
0.7:1 0.9:1 1.18ab 0.76 0.65ab 5.11a 6.52b 1.70a 2.57ab 39.55ab 42.17a 33.33ab 39.59a
0.8:1 1.0:1 1.15b 0.71 0.63abc 5.79b 6.34bc 2.15a 2.44ab 45.17ab 40.23a 37.13ab 38.16a
1.3:1 1.6:1 1.22ab 0.70 0.58abc 8.09c 5.98cde 3.66b 1.91bc 37.87ab 37.23a 21.09ab 35.96a
1.0:1 1.2:1 1.18ab 0.64 0.54c 6.95d 6.66b 1.40a 2.39ab 52.99a 33.67a 45.62a 32.02a
1.3:1 1.6:1 1.18ab 0.64 0.54c 8.54e 6.33bc 1.94a 1.31c 36.82b 22.41b 22.90b 20.90b
0.04 0.04 0.03 0.20 0.21 0.51 0.24 5.28 3.46 6.30 3.52
Means diets with different superscript letters differ (P < 0.05) from each other as analyzed by the Tukey-Kramer’s tests. Pooled standard error of means (n = 6).
a,b,c,d,e 1
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were processed according to Fan et al. (2008). Analyses of DM and P in samples were carried out according to Rideout et al. (2008). Total Ca contents in samples were analyzed by the inductively coupled plasma-mass spectrometry. Titanium oxide in samples was analyzed according to Leone (1973). Fecal endogenous Ca and P outputs and the true fecal Ca and P digestibility values associated with the corn and SBM-based diets were measured from Exp. 1 by the substitution method (Fan et al., 2008). True fecal Ca and P digestibility and efficiency of dietary Ca and P retention were calculated according to Rideout et al. (2008). Unless specified, data reported in the text were means ± SE. The Tukey-Kramer’s tests were conducted by using the mixed models of SAS (SAS Institute Inc., Cary, NC). RESULTS AND DISCUSSION True fecal Ca digestibility (53.6%) in the corn and SBM-based diets determined from Exp. 1 was surprisingly low and was associated with a large variability (SE = 12.7%) giving the fact that limestone and CaHPO4 were supplemented. The fecal endogenous Ca loss (0.91 g/kg DMI) measured from this study was also associated with a large variability (SE = 0.20 g/kg DMI). Very little information is available in the literature regarding estimation of both true fecal Ca digestibility and the fecal endogenous Ca loss in growing pigs. True fecal P digestibility (43.8 ± 16.7%) in the corn and SBMbased diet determined from Exp. 1 was close to the average true P digestibility values reported in corn and SBM for growing pigs (Fan et al., 2008). However, the fecal endogenous P loss (1.31 ± 0.15 g/kg DMI) measured from this study was much higher than the range of values reported in the literature for corn and SBM (Fan et al., 2008). It should be pointed out that the analyzed dietary Ca content in diet 5 was lower than expected in comparison with the other diets likely due to a diet mixing error, as repeated Ca analyses in the diet sample gave the much
lower than expected Ca content (Table 1). Based on the fecal endogenous Ca and P losses measured from Exp. 1, true fecal Ca and P digestibility values were calculated for the diets used in Exp. 2 and dietary true digestible Ca to true digestible P ratio were also calculated (Table 2). Changes in the dietary Ca to P ratio had no effects (P > 0.05) on ADG. No differences (P > 0.05) in ADFI were observed between the other diets except the lower ADFI (P < 0.05) in diet 3 compared with diet 2. However, G:F was higher (P < 0.05) in diet 2 compared with diets 5 and 6. Changes in the dietary Ca to P ratio had consistent effects on true fecal P digestibility and retention with much lower values (P < 0.05) observed in diet 5 in comparison with the other diets. Responses in true fecal Ca digestibility and Ca retention were not consistent and were associated with a much large variability. In summary, true fecal digestible Ca to P ratio of 0.9:1 to 1.0:1 were associated with optimal responses in both G:F as well as true fecal P digestibility and retention in growing pigs fed corn and SBM-based diets. Literature Cited Fan, M. Z., Y. Shen, Y. L. Yin, Z. R. Wang, Z. Y. Wang, T. J. Li, T. C. Rideout, R. L. Huang, T. Archbold, C. B. Yang, and J. Wang. 2008. Methodological considerations for measuring phosphorus utilization in pigs. Page 370 in Mathematical Modelling in Animal Nutrition. J. France, and E. Kebreab, eds. CAB Int., Wallingford, Oxon, UK. Jongbloed, A. W., H. Everts, and P. A. Kemme. 1991. Phosphorous availability and requirements in pigs. Pages 65–80 in Recent Advances in Animal Nutrition. E. R. Heinemann, ed. Butterworth, London, UK. Leone, J. L. 1973. Collaborative study of the quantitative determination of titanium dioxide in cheese. J. Assoc. Off. Anal. Chem. 56:535–537. NRC. 1998. Nutrient Requirements of Swine. 10th ed. National Academy Press, Washington, DC. Rideout, T. C., Q. Liu, P. Wood, and M. Z. Fan. 2008. Nutrient utilization and intestinal fermentation are differentially affected by the consumption of resistant starch varieties and conventional fibers in pigs. Br. J. Nutr. 99:984–992.
