Published January 23, 2015
Effect of dietary fiber and crude protein content in feed on nitrogen retention in pigs1 P. Patráš,2 S. Nitrayová, M. Brestenský, and J. Heger Animal Production Research Centre, Institute of Nutrition, Nitra, 94941 Slovakia
ABSTRACT: Eight gilts (29.9 ± 1.7 kg initial BW) were used to evaluate effects of dietary (crude) fiber on N excretion via feces and urine at 2 levels of dietary CP. Pigs were fed 4 dietary treatments according to a double 4 × 4 Latin square. Treatments were low (14%) CP and low (3.25%) (crude) fiber (LPAA), low CP and high (4.46%) fiber (LPAABP), high (18.8%) CP and low fiber (HP), and high CP and high fiber (HPBP). Diets were based on soybean (Glycine max) meal, wheat (Triticum aestivum), and maize (Zea mays) and were supplemented with crystalline AA. High fiber diets contained 15% dried beet (Beta vulgaris) pulp. Pigs were housed in metabolic cages and fed 2 equal meals at 0700 and 1700 h at a daily rate of 90 g/kg BW0.75. Water was offered ad libitum. Each experimental period consisted of a 6-d adaptation followed by a 4-d collection of feces and urine (bladder catheters). Data were
analyzed using ANOVA. Differences between means (P < 0.05) were assessed using Fisher’s LSD procedure. The N intake, fecal N excretion and absorption, and N retention increased (P < 0.05) in pigs fed high-CP diets with added fiber (HP vs. HPBR). With added fiber, urinary N excretion (g/d) was reduced (P < 0.02) only for the low-CP diet. Urinary N as a percentage of N intake was reduced (P < 0.01) in both groups fed highfiber diets irrespective of dietary CP content. Dietary fiber level did not affect DMI. Fecal DM excretion (g/d) was higher (P < 0.02) in pigs fed diets with high CP and high fiber content than in pigs fed diets with high CP and low fiber content. In conclusion, beet pulp fiber added to diets increased fecal N and reduced urinary N and in diets with higher CP content increased overall N retention.
Key words: crude protein, excretion, fiber, pig © 2012 American Society of Animal Science. All rights reserved. INTRODUCTION Diets with added by-products rich in fiber may increase animal health and reduce environmental impact of pig production. Inclusion of beet pulp into a pig diet increased growth performance immediately after weaning and carcass composition at slaughter (Lizardo and Aumaître, 2001). Fiber supports bacterial fermentation that shifts N excretion from urine to feces (Nahm, 2003; Aarnink and Verstegen, 2007). Fiber may reduce NH3 emission and increase pig intestinal health and welfare (Basset-Mens and van der Werf, 2005). The relationships between feeding and N excretion has been investigated (Le Goff et al., 2003; Galassi et al., 2007) with particular reference to NH3 emissions. The objective of the present study was to verify the effect of 1 This article was written during project BELNUZ 26220120052 supported by the Operational Programme Research and Development funded from the European Regional Development Fund. 2 Corresponding author:
[email protected]
J. Anim. Sci. 2012.90:158–160 doi:10.2527/jas53837
fiber on N excretion via feces and urine at 2 levels of dietary N. MATERIAL AND METHODS Eight crossbred gilts, progeny of Large White sows and Landrace boars (29.9 ± 1.7 kg initial BW), were housed individually in metabolic cages. Dietary treatments included diet 1, with lower CP content (14%) and supplemented with Ile, Lys, Met, Thr, Trp, and Val (LPAA); diet 2, which was similar to diet 1 with 150 g/kg dried beet pulp (LPAABP); diet 3,with high CP content (18.8% CP) and supplemented with Lys and Thr (HP); and diet 4, which was similar to diet 3 with 15% dried beet pulp (HPBP). Diets were based on wheat, maize, and soybean meal and were formulated to a constant ME content (13.3 MJ/kg) using supplementation with rapeseed oil (Table 1). Pigs were randomized to diets in a double 4 × 4 Latin square. Pigs were fed 2 equal meals at 0700 and 1700 h at a daily rate of 90 g/kg BW0.75. After a 5-d adaptation to cages and environment, 4
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Table 1. Composition of diets and analyzed content of nutrients Diet1 Item
LPAA LPAABP
Ingredient , g/kg diet Maize Wheat Soybean meal Beet pulp Rapeseed oil Monocalcium phosphate Limestone Salt Premix2 L-Lys HCl L-Thr DL-Met L-Val L-Ile L-Trp Analyzed nutrient contents (g/kg air dry) DM CP Crude fiber
HP
HPBP
552.0 300.0 86.9 – 8.3 14.1 11.0 3.9 3.0 5.8 2.2 0.9 0.9 0.9 0.4
388.0 300.0 88.8 150.0 22.6 14.1 7.9 3.5 3.0 5.7 2.4 1.2 1.1 1.0 0.5
426.0 300.0 223.0 – 9.6 12.0 10.7 3.8 3.0 1.0 0.3 – – – –
276.0 280.0 231.0 150.0 23.9 12.7 7.6 3.4 3.0 1.4 0.4 – – – –
883.5 139.2 30.4
887.5 140.8 45.6
886.3 183.8 34.6
890.1 192.9 43.6
1 LPAA = low CP, AA-supplemented diet; LPAABP = low CP, AAsupplemented diet + 15% dried beet pulp; HP = high CP; HPBP = high CP + 15% dried beet pulp. 2 Premix was added to meet vitamin and mineral requirements of pigs.
consecutive 10-d experimental periods followed. Each period consisted of a 6-d adaptation to experimental diet and a 4-d separate collection of feces, urine, and refused feed. Samples of diets, urine, and feces were stored at –20°C until analysis for DM, N, and fiber using standard methods (AOAC, 1998). Data were analyzed by 1-way ANOVA using Statgraphic Plus package (version 3.1; Statistical Graphics Corp., Rockville, MD). Differences between means were assessed using Fisher’s LSD procedure; P < 0.05 was considered significant.
RESULTS AND DISCUSSION Because dietary CP content affected N balance, only diets with similar CP level were compared for most variables (Table 2). Dry matter excretion was higher (P = 0.014) for pigs fed HPBP than HP. Nitrogen intake increased (P = 0.015) with dietary inclusion of beet pulp for high dietary CP but not for low CP. Adding beet pulp shifted N excretion from urine to feces for both dietary CP levels. Specifically, adding beet pulp increased (P < 0.003) fecal N excretion 40% for high dietary CP but not for low CP. Adding beet pulp reduced (P = 0.02) urinary N for low dietary CP but not for high CP, similar to Galassi et al. (2007). At 150 kg BW, typical for some Italian pigs, changing from a diet containing 13.5% CP and 3.2% crude fiber to a diet with 14.0% CP and 4.1% crude fiber increased fecal N excretion from 10 to 12.3% of N intake and feeding diet with 14.6% CP and 5.4% crude fiber increased fecal N excretion to 16.3%. In the present study, added fiber increased (P < 0.05) absorbed N (calculated as N intake minus N in feces) and N retention in high CP but not low CP diets, similar to Zervas and Zijlstra (2002). Nitrogen retention as percentage of absorbed N was greater (P < 0.01) for high than low fiber diets for both CP groups. The greatest change was for N in urine as percentage of N intake that was lower for high than low fiber diets for both CP groups. Effects of fiber from beet pulp on growth performance after weaning, ileal and fecal nutrient digestibility, and intestinal enzymes of piglets were studied in a series of experiments (Ramonet et al., 2000; Högberg and Lindberg, 2004). Six to twelve percent of beet pulp in piglet diets did not affect total tract digestibility of energy and N (Lizardo and Aumaître, 2001). These and our data indicate that fiber from beet pulp has a greater effect for high than low CP diets, although its fiber for a range of dietary protein content
Table 2. Effects of crude fiber and dietary protein level on DM and N balance Diet1 Item DMI, kg/d DM excretion, g/d Crude fiber, g/d N balance, g/d Intake Fecal excretion Urinary excretion Absorbed N Retained N Retained N, % of absorbed N balance, % of intake Fecal N excretion Urinary N excretion
P-value2
LPAA
LPAABP
HP
HPBP
SEM
1
2
3
4
1.23 148 42.4
1.14 145 58.6
1.12 131 44.2
1.29 166 63.3
0.22 31 8.6
0.145 0.304 –
0.049 0.014 –
0.089 0.078 0.386
0.078 0.074 0.204
31.1 4.6 8.0 26.4 18.4 69.4
29.0 5.2 6.7 23.8 17.1 71.9
36.6 4.5 13.9 32.1 19.2 60.6
44.7 6.3 13.0 38.4 25.4 66.1
6.52 1.10 2.19 6.19 4.51 6.79
0.166 0.183 0.020 0.118 0.241 0.043
0.015 0.003 0.182 0.035 0.003 0.018
– – – – – –
– – – – – –
15.3 25.7
18.3 22.9
12.7 36.3
14.6 28.9
3.76 0.20
0.092 0.005
0.160 0.001
– –
– –
1 LPAA = low CP, AA-supplemented diet; LPAABP = low CP, AA-supplemented diet + 15% dried beet pulp; HP = high CP; HPBP = high CP + 15% dried beet pulp. 2 Contrast: 1 = LPAA vs. LPAABP; 2 = HP vs. HPBP; 3 = LPAA vs. HP; 4 = LPAABP vs. HPBP. Contrasts were based on n = 8 per diet.
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will increase N in feces, reduce N in urine, and affect overall balance of N. The present results indicate that undigested fiber serves as an energy source for intestinal microbiota. Microbial populations exploit N from urea and other N resources to a greater extent and therefore less N is excreted via urine. From an environmental point of view, N excreted in feces as microbial protein is favorable because its degradation is slower than urinary N. Using diets with higher N content may increase N absorbed. Part of the absorbed protein is transported back to the intestine and is used for synthesis of microbial protein. LITERATURE CITED Aarnink, A. J. A., and M. W. A. Verstegen. 2007. Nutrition, key factor to reduce environmental load from pig production. Livest. Sci. 109:194–203. Association of Official Analytical Chemists (AOAC). 1998. Official Methods of Analysis, 16th ed. AOAC, Washington, DC. Basset-Mens, C., and H. M. G. van der Werf. 2005. Scenario-based environmental assessment of farming systems: the case of pig production in France. Agric. Ecosyst. Environ. 105:127–144. Galassi, G., G. M. Crovetto, and L. Malagutti. 2007. Growth and slaughter performance, nitrogen balance and ammonia emission
from slurry in pigs fed high fibre diets. Ital. J. Anim. Sci. 6:227– 239. Högberg, A., and J. E. Lindberg. 2004. Influence of cereal nonstarch polysaccharides on digestion site and gut environment in growing pigs. Livest. Prod. Sci. 87:121–130. Le Goff, G., J. Noblet, and C. Cherbut. 2003. Intrinsic ability of the faecal microbial flora to ferment dietary fibre at different growth stages of pigs. Livest. Prod. Sci. 81:75–87. Lizardo, R., and A. Aumaître. 2001. Non-starch polysaccharides of sugar-beet pulp improve the adaptation to the starter diet, growth and digestive process of the weaned pig. Pages 85–89 in Feed Manufacturing in the Mediterranean Region. Improving Safety: From Feed to Food. J. Brufau, ed. International Centre for Advanced Mediterranean Agronomic Studies – Mediterranean Agronomic Institute of Zaragoza (CIHEAM-IAMZ), Zaragoza, Spain. Nahm, K. H. 2003. Influence of fermentable carbohydrates on shifting nitrogen excretion and reducing ammonia emission of pigs. Crit. Rev. Environ. Sci. Technol. 30:165–186. Ramonet, Y., S. Robert, A. Aumaître, J. Y. Dourmad, and M. C. Meunier-Salaün. 2000. Influence of the nature of dietary fibre on digestive utilization. some metabolite and hormone profiles and the behaviour of pregnant sows. J. Anim. Sci. 70:275–286. Zervas, S., and R. T. Zijlstra. 2002. Effects of dietary protein and fermentable fiber on nitrogen excretion patterns and plasma urea in grower pigs. J. Anim. Sci. 80:3247–3256.
