Effect of pelleting mixed feeds on phytase activity and the apparent absorbability of phosphorus and calcium in pigs

Animal Feed Science and Technology, 28 (1990) 233-242

233

Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

Effect of Pelleting Mixed Feeds on Phytase Activity and the Apparent Absorbability of Phosphorus and Calcium in Pigs A.W. JONGBLOED and P.A. KEMME

Research Institute for Livestock Feeding and Nutrition (I. V. V. 0.), P.O. Box 160, 8200 AD Lelystad (The Netherlands) (Received 16 January 1989; accepted for publication 28 July 1989)

ABSTRACT Jongbloed, A.W. and Kemme, P.A., 1990. Effect of pelleting mixed feeds on phytase activity and the apparent absorbability of phosphorus and calcium in pigs. Anita. Feed Sci. Technol., 28: 233-242. Six diets were used to determine the apparent absorbability of phosphorus (P), using total faeces collection, in pigs from 40 to 100 kg live weight. In diets containing a considerable phytase activity from feedstuffs such as wheat, wheat middlings or barley, steam pelleting at ~ 80 ° C sometimes decreased the P and calcium (Ca) absorbability by 10 percentage units or more. This was mainly due to a considerable reduction of the phytase activity. Cold-pelleting such diets had no negative effect on the P absorbability or phytase activity. In diets without phytase activity, steam pelleting had no negative effect on P and Ca absorbability. The results indicate, that when the temperature of the pellets reaches ~ 80 ° C, the concentration of absorbable P can be decreased substantially in feeds containing a high phytase activity. The type of diet and the conditions during pelleting are therefore decisive in determining P and Ca absorbability.

INTRODUCTION

In The Netherlands, > 90% of the mixed feed used for pigs is (steam) pelleted. Pelleting is carried out for several reasons, such as reduction of Salmonella (above 70 ° C ), dust, spillage of feed and possibly improvement of the feed conversion ratio and digestibility (Van Schoubroek et al., 1971 ). Pelleting can also affect the absorbability or availability of phosphorus (P). In experiments on chicks, Summers et al. (1967) observed an increase in the availability of P by steam pelleting a diet containing 25% wheat bran. In a second experiment however steam pelleting or dry pelleting wheat bran had no effect (Summers et al., 1968). In another experiment by the same group, ~ e a m pelleting a maize-soya-bean meal diet enhanced the bone ash content in chickens probably by increasing the availability of P. It was surprising that pelleting the maize or soya-bean meal separately had no effect on growth or 0377-8401/90/$03.50

© 1990 Elsevier Science Publishers B.V.

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A.W. JONGBLOED AND P.A. KEMME

bone development (Bayley et al., 1968). In more recent experiments on chicks, no advantage of steam pelleting on P availability has been reported (Corley et al., 1979; Takemasa and Hijkuro, 1983 ). Harrold et al. (1982) even reported a reduction in P availability from pelleting barley, oats, maize or soya-bean meal separately. In experiments on pigs receiving a maize-soya-bean meal diet not supplemented with inorganic P, Bayley and Thomson (1969) and Bayley et al. ( 1975 ) showed an improvement in the absorption of P due to steam pelleting. No improvement was found with diets either supplemented with inorganic P or with a high calcium concentration ( > 9.2 g kg -1 ). Also Harmon et al. (1970) could not find any differences due to pelleting in the ash content of some bones in pigs given unsupplemented or supplemented maize-soya-bean meal diets. Trotter and Allee (1979) concluded that pelleting a sorghum-soya-bean meal diet slightly increased the absorption of P for pigs when the diet was not supplemented with P. Ross et al. (1983) found no effect of pelleting maize on the availability of P. In earlier experiments (Jongbloed, 1987), it was shown that in growing pigs the absorbability of P in mixed feeds, with or without supplementation of inorganic P, was significantly increased on average by three percentage units by steam pelleting. The higher absorbability of P after pelleting might be due to the increase of crushed cells, thus enhancing the hydrolysis of phytate P by phytase. The literature shows that no definite conclusions can be drawn concerning the effect of steam pelleting on the apparent absorption of P. This may be due to the conditions at pelleting (e.g., temperature and exposure time) in relation to the presence of native phytase or to the concentration of P in the diet. Therefore, three digestibility experiments were performed in which the diets and pelleting conditions were precisely controlled. The term digestibility of a mineral will be used here and can be read as apparent absorbability. MATERIALSAND METHODS Animals and management The animals used were pure Large Whites (GY) in Experiments 1 and 2, and (GY × (GY × Finnish Landrace) ) cross breeds in Experiment 3. At ~ 35 kg live weight, the animals were placed in metabolism crates where they remained until 100 kg live weight. In an adaptation period of 5-7 days, the animals were introduced to a new diet and this was followed by a preliminary period of 7 days. During the next 10 days the faeces were collected quantitatively and stored at - 20 ° C. The feed was sampled in triplicate and the faeces of each animal, after homogenizing, in duplicate. The animals were weighed just before and after the collection period in addition to their weekly weighing.

EFFECT OF PELLETING MIXED FEEDS

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Diets and feeding methods I n E x p e r i m e n t 1, t w o d i e t s (A a n d B ) w e r e used. D i e t A w a s c e r e a l b a s e d being composed largely of barley, wheat and soya-bean meal; Diet B was byproduct based and composed mainly of maize by-products, tapioca, soya-bean m e a l a n d c o c o n u t e x p e l l e r ( T a b l e 1 ). I n E x p e r i m e n t 2, t h r e e d i e t s (C, D a n d E ) w e r e used. D i e t C w a s p h y t a s e rich, w i t h p r e d o m i n a n t l y b a r l e y , w h e a t a n d w h e a t m i d d l i n g s ; D i e t D w a s p h y tase deficient, with mainly maize by-products, and Diet E was based on legume seeds, c o m p r i s i n g ~ 50% o f l u p i n s a n d p e a s ( T a b l e 1 ). I n E x p e r i m e n t 3, a m a i z e - w h e a t - s o y a - b e a n m e a l d i e t w a s u s e d ( D i e t F ) . I n E x p e r i m e n t s 2 a n d 3, n o s u p p l e m e n t a r y P w a s used. All d i e t s c o n t a i n e d s u f f i c i e n t p r o t e i n a n d a m i n o a c i d s t o allow g o o d p i g p e r f o r m a n c e . B e c a u s e m o s t o f t h e feeds h a d also b e e n t e s t e d in s e p a r a t e d i g e s t i o n trials, n o m o r e t h a n five w e r e i n c o r p o r a t e d in a n y o n e diet. I n E x p e r i m e n t s 1 a n d 2 t h e d i e t s w e r e o f f e r e d a t t w o f e e d i n g levels, 2.3 a n d 2.8 t i m e s m a i n t e n a n c e (293 k J N E f ( n e t e n e r g y f o r f a t t e n i n g ) o r 418 k J M E p e r kg°75). I n E x p e r i m e n t 3, o n l y t h e f e e d i n g level o f 2.3 t i m e s m a i n t e n a n c e w a s used. T h e feed w a s o f f e r e d t w i c e a day. W a t e r w a s a d d e d t o t h e f e e d in t h e t r o u g h i m m e d i a t e l y b e f o r e f e e d i n g a t a r a t i o o f 2.5 k g w a t e r p e r k g feed. TABLE 1 Feedstuff composition of Diets A-F 1 (g kg- 1) Experiment 1

Experiment 2

A

B

C

193

227 390 174 . 20 171 13.6 4.3

Barley 366 Wheat 350 Maize Soya-bean meal, (crude fibre 3.5-7% ) 193 Soya-bean meal, (crude fibre < 3.5% ) . Maize gluten feed, (crude protein < 21% ) Hominy feed Cane molasses 20 Wheat middlings 50 Coconut expeller Tapioca (starch 62.5-67.5% ) Lupins (crude protein 26% ) Peas (crude protein 24% ) Limestone 13.5 Dicalcium phosphate 3.5 Pre-mix and salt 4.0

. 145 217 20 126 271 19.0 5.0 4.0

.

D

271 149

Experiment 3 E

F -

400 382 200

272 267 20

138 20 380 249 200 17.5 8.7 4.3 4.3

13.5 4.2

IA = cereal diet; B = by-product diet; C = phytase-rich diet; D = phytase-deficient diet; E = legume seed diet; F = maize-wheat-soya-bean meal diet.

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A.W.JONGBLOED AND P.A. KEMME

Experimental design In Experiment 1, Diets A and B were investigated as meal or in pelleted form at a live weight of 40, 60, 80 and 100 kg according to a Latin square design. Experiment 2 was conducted in the same way for Diets C, D and E. Experiment 3 also had a Latin square design. Besides the meal variant, Diet F was steam pelleted and cold pelleted, and a fourth diet was formulated in which the normal wheat was replaced by phytase-inactivated wheat. The phytase-inactivated wheat originated from the same batch as the normal wheat.

Technological treatments The feedstuffs in Experiments 1 and 2 were milled in a hammer mill (2.5mm sieve) and after mixing and manufacture by a local merchant, portions of the various mixes were transported to Wageningen ( T N O Cereals, Flour and Bread Institute) for pelleting. The results of some measurements taken during the pelleting process are given in Table 2. In Experiments 1 and 2, the temperature of the meal was increased to 75 ° C by direct steam injection in a mixer, where meal and steam were thoroughly mixed for a period of 1 min. Subsequently, the mixture was pressed in a 4-kW C P M laboratory press. During this process, the temperature rose by ~ 5 ° C. The press dies had a diameter of 6 mm and a length of 30 mm (for Diets C and D, 35 mm). The rotation speed of the matrix was 300 r.p.m. The pellets were cooled for 15 min on a band cooler. In Experiment 3, the temperature of the meal was raised to 80 ° C by direct steam injection. The press dies had a length of 35 mm. For cold pelleting no steam was used; this resulted in a pellet temperature somewhat > 40 ° C. The phytase activity of the fourth treatment of the feed used in Experiment 3 was destroyed by steam treating the whole wheat kernels for 3 min at 104 ° C. The TABLE 2 Physical measurements during pelleting Diet

Cereal By-product Phytase-rich Phytase-deficient Legume seed M a i z e - w h e a t - s o y a (warm) M a i z e - w h e a t - s o y a (cold)

Power Pellet Pellet quality press production (kW) (kg h - ~) Crumbling Hardness (%) (Newton)

Temperature ( ° C )

1.76 1.63 1.60 1.80 1.63 1.10 3.28

75 75 73 74 74 78 12

113 98 64 87 112 57 115

5.4 22.3 2.8 5.1 4.5 13.0 97.4

263 211 289 160 11

Press meal

Pellets

80 81 76 80 43

EFFECT OF PELLETING

237

MIXED FEEDS

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238

A.W. JONGBLOED AND P.A. KEMME

wheat was then dried and milled over a 2-mm sieve, as with the normal wheat. The maize and soya-bean meal were milled in a hammer mill (2.5-mm sieve).

Analytical methods Methods for the analyses of moisture, crude ash and crude fibre were performed according to the International Organisation of Standardisation (ISO, P.O. Box 56, CH-1211 Geneva ZO, Switzerland) ISO 6494, ISO 5984 and ISO 5498 directives, respectively. The concentration of crude protein (N X 6.25) was estimated by the Kjeldahl method (ISO 5953). The method for analysis of crude fat was according to the E.C. (1984). The concentrations of calcium (Ca) and magnesium were determined by atomic absorption, that of P by spectrophotometry also after dry ashing (Table 3). The concentration of phytate P was estimated by the method described by Oshima et al. (1964). The phytase activity was estimated by weighing 2.0 g (finely ground, 0.5 mm) of sample in a small vessel with 20 ml sodium acetate buffer (0.1 M, pH 5.5) which was placed in a water bath at 40 ° C. After 0, 15, 30 and 60 min, 3 ml 6 N HC1 were added to the vessel and it was shaken for 1-1.5 h at room temperature. After centrifuging for 10 min at 2000 Xg, the concentration of free phosphate was determined in the filtrate. The phytase activity was expressed as ~mol free phosphate released m i n - 1 k g - 1 dry matter.

Statistical methods The results of Experiment 1 were analysed using regression analysis for a non-orthogonal design; analysis of variance was applied to the results from Experiments 2 and 3. RESULTS The experiments went according to plan and there were no feed refusals. In Experiments 1, 2 and 3, the average daily live weight gain from 40 to 100 kg was 780, 710 and 505 g, respectively. The lower daily gain in Experiment 3 was due to the lower feeding level.

Experiment I The statistical analysis showed no interaction between type of diet, level of feeding and physical form of the diet on the digestibility of dry matter and minerals. As expected, there were significant differences in digestibility (P < 0.001 ) between the cereal- and by-product-based diets (Table 4). Pelleting the diets only improved the dry matter and magnesium digestibility slightly, but not that of Ca and P.

EFFECT OF PELLETING MIXED FEEDS

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TABLE 4

Digestibility ( % ) of the cereal (A) and by-product (B) diets

Drymatter Ca Mg P

Diet A

Diet B

SED

Significance a

Meal

Pellets

SED

84.4 41.7 32.6 44.4

78.6 30.5 25.0 29.9

0.29 1.11 1.20 1.02

*** *** **" ***

81.2 36.5 27.0 37.2

81.9 35.7 30.5 37.0

0.29 1.11 1.20 1.02

Significance a

ns ns

a ***p < 0.05; **P < 0.01; ***P < 0.001; n s = not significant. TABLE 5

Digestibility ( % ) of the phytase-rich ( C ) , p h y t a s e - d e f i c i e n t ( D ) and legume seed ( E ) diets

Diet C

Diet D

Diet E

Meal

Pellets

SED

Significance a

Dry matter Ca Mg P

82.9 45.2 31.8 49.5

82.3 34.4 28.4 40.0

0.31 1.89 1.37 1.68

*** "" ***

Dry matter Ca Mg P

78.4 36.8 17.4 28.2

79.4 36.7 19.4 27.6

0.87 3.21 4.28 2.13

Dry matter

81.4 44.8 22.4 33.8

82.6 48.2 25.2 34.6

0.41 2.76 2.09 2.03

Ca Mg P

ns ns ns ns

ns ns ns

aSee Table 4.

Experiment 2 Because the phytase-rich, phytase-deficient and legume seed diets were investigated in separate Latin squares, no statistical analysis could be performed between these three diets. However, Table 5 shows that there are considerable differences in digestibility between the diets. There were no significant differences in digestibility between the low and high feeding levels for the three diets. Pelleting the phytase-rich diet resulted in a significantly lower digestibility for dry matter and minerals. In particular, the digestibility of Ca and P decreased dramatically (10 percentage units ). No effect of pelleting was seen on the mineral digestibility of the phytasedeficient and legume seed diets. However the dry matter digestibility of the legume seed diet was improved by pelleting.

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TABLE 6 D i g e s t i b i l i t y ( % ) a n d p h y t a s e a c t i v i t y (/tmol P i released m i n - 1 k g - 1 d r y m a t t e r ) of several vari a n t s o f t h e m a i z e - w h e a t - s o y a - b e a n m e a l diet

Dry matter Ca Mg P Phytase activity

Meal

Cold-pelleted

Steam-pelleted

Phytase-inactivated

SED

90.2 ab 55.4 a 33.5 ~ 49.1 a 482

91.0 b 36.5 b 29.7 ab 47.2 a 482

89.6 a 36.2 b 26.0 b 31.2 b 0

89.5 a 46.0 c 27.1 b 30.4 b 0

0.42 3.43 2.56 3.58

D i f f e r e n t c h a r a c t e r s in t h e s a m e row i n d i c a t e t h e s i g n i f i c a n c e o f differences; P < 0.05.

Experiment 3 The results of pelleting either cold or with steam are given in Table 6. Moreover in this table the digestibility of a meal diet is given in which the phytase of the wheat was inactivated. The digestibility of Ca was reduced significantly by pelleting and inactivation of the wheat phytase. The same tendencies were observed for Mg. Cold pelleting reduced the digestibility of P non-significantly, but steam pelleting resulted in the same digestibility of P as with the diet containing previously inactivated wheat phytase. DISCUSSION

In Experiment 1, no effect of pelleting was demonstrated on P digestibility in either of the diets. For Diet A, this can be explained by the fact that the phytase activity, as a result of steam pelleting, was only slightly decreased. It is doubtful whether a reduction in phytase activity from 760 to 600 units would significantly reduce P digestibility. No quantitative information is available on the relationship between units of phytase activity and P digestibility; this would be of great interest. Moreover the amount of digestible P offered with Diet A could bias the results because the amount of digestible P offered (2.5 g per kg dry matter) is slightly above the optimum requirement for P in the weight range studied (Jongbloed, 1987). In such a case, it is difficult to show a negative or positive effect because of regulatory mechanisms at the intestinal level. This may also be an explanation for the results of Bayley and Thomson (1969) and Bayley et al. {1975) who found no improvement due to pelleting in the P digestibility of diets supplemented with inorganic P. In diets with a P concentration below the optimum requirement for P, an effect of pelleting on P digestibility can be demonstrated more clearly. In Diets B, D, E and F, this is probably the case. In those diets containing no phytase activity (B, D and E), we could not demonstrate any effect of steam pelleting

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241

on the digestibility of P. This is in accordance with most experiments reported in the literature (Harmon et al., 1970; Ross et al., 1983 ). When diets containing phytase activity are steam pelleted the conditions during pelleting are crucial for P digestibility. Our experiments show clearly that when the temperature of the pellets reached/> 80 ° C a dramatic decrease in P digestibility can be found (Diets C and F). This can be explained by the reduction of phytase activity in these diets. In Experiment 3, the P digestibility of the steam pelleted diet was equal to that of the phytase-inactivated diet. When the diet was cold pelleted no negative effect on P digestibility was demonstrated. So far, no experiments investigating the effect of pelleting phytase-rich diets on pigs, other than those of Jongbloed (1987), have been reported in the literature. In the phytase-rich and maize-wheat-soya-bean meal diets, not only was P digestibility decreased significantly by pelleting, but also Ca digestibility. It is well known that phytic acid has a high affinity to bi- and trivalent cations (Wise, 1983). As the phytic acid is less hydrolysed by phytase owing to its destruction by pelleting, more Ca can be bound to phytic acid. Our experiments show that Ca digestibility can be decreased by 10 percentage units or more in such a case. This has implications for the Ca supply to the animal. Why the Ca digestibility in the cold-pelleted feed was also decreased is not known and deserves more attention. The interpretation of some experiments on minerals reported in the literature is complicated by the experimental design. In the experiments of Bayley et al. (1975), the total duration of the adaptation and preliminary period was 10 days. This may be too short for a complete adaptation to the new diets. Also, the C a / P ratio of the retention in their experiments (ranging from 2.1 to 6.0) confirms this. Normally, the C a / P ratio of the retention is ~ 1.6. Jongbloed {1987) showed that when the dietary supply of P after changing the diet is doubled or halved, an adaptation period should last ~ 3 weeks before total adaptation can be achieved. Therefore criticism can also be made of the great beneficial effect of pelleting on P digestibility of the unsupplemented diets in the experiments of Bayley et al. (1975). In the present experiments, no dramatic changes in the mineral supply occurred. Moreover, most diets were marginally deficient in P and the total adaptation period was >/12 days. Therefore insufficient adaptation to new diets would play a minor part in the results. When evaluating feedstuffs by means of their P digestibility, one may run the risk of overestimating this value for phytase-containing feedstuffs (i.e., wheat, wheat bran, barley) when these are steam pelleted. More knowledge should be gained of the precise conditions under which the phytase is inactivated (temperature, exposure time, feedstuff composition of the mixed feed). The feed industry might consider it useful to determine phytase activity prior to and after steam pelleting.

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ACKNOWLEDGEMENTS

This work was supported by the Dutch Commodity Board for Feedstuffs and the Dutch Fund for Manure Research. Ir. H. Beumer of the TNO Cereals, Flour and Bread Institute of Wageningen is acknowledged for pelleting the diets and Dr. P. Slump of the CIVO Institutes TNO at Zeist for analysing the phytase activity in part of the diets.

REFERENCES Bayley, H.S. and Thomson, R.G., 1969. Phosphorus requirements of growing pigs and effect of steam pelleting on phosphorus availability. J. Anim. Sci., 28: 484-491. Bayley, H.S., Summers, J.D. and Slinger, S.J., 1968. The effect of steam pelleting feed ingredients on chick performance: Effect on phosphorus availability, metabolizable energy value and carcass composition. Poult. Sci., 47: 1140-1148. Bayley, H.S., Pos, J. and Thomson, R.G., 1975. Influence of steam pelleting and dietary calcium level on the utilization of phosphorus by the pig. J. Anim. Sci., 40: 857-863. Corley, J.R., Baker, D.H. and Easter, R.A., 1979. Biological availability of phosphorus in rice bran and wheat bran as affected by pelleting. J. Anim. Sci., 49: 77. E.C.. 1984. Directive No. L 15/28-30. Bureau for Official Publications of the European Communities, Luxembourg. Harmon, B.G., Jensen, A.H. and Baker, D.H., 1970. Effect of pelleting on phosphorus utilization in swine. J. Anim. Sci., 31:202 (Abstract). Harrold, R.L., Johnson, J.N., Slanger, W.D. and Haugse, C.N., 1982. The bioavailablephosphorus content of some common North Dakota feedstuffs. N. D. Farm Res., 40: 22-24. Jongbloed, A.W., 1987. Phosphorus in the feeding of pigs; effect of diet on the absorption and retention of phosphorus by growing pigs. I.V.V.O. Rep. No. 179, Lelystad, The Netherlands. Oshima, M., Taylor, T.G. and Williams, A., 1964. Variations in the concentration of phytic acid in the blood of domestic fowl. Biochem. J., 92: 42-46. Ross, R.D., Cromwell, G.L. and Stahly, T.S., 1983. Biological availability of the phosphorus in high moisture and pelleted corn. J. Anita. Sci., 57:96 (Abstract). Summers, J.D., Slinger, S.J. and Cisneros, G., 1967. Some facors affecting the biological availability of phosphorus in wheat by-products. Cereal Chem., 44: 318-323. Summers, J.D., Pepper, W.E., Bayley, H.S. and Slinger, S.J., 1968. The effect of steam pelleting on the utilization of phosphorus in wheat bran. Poult. Sci., 47: 1397-1403. Takemasa, M. and Hijikuro, S., 1983. Effect of pelleting on the utilization of phosphorus by chicks. Jpn. Poult. Sci., 20: 330-336. Trotter, M. and Allee, G.L., 1979. Effects of steam-pelletingand extruding sorghum grain-soybean meal diets on phosphorus availability for swine. J. Anim. Sci., 49:255-256 (Abstract). Van Schoubroek, E., Coucke, L. and van Spaendonk, R., 1971. The quantitative effect of pelleting feed on the performance of piglets and fattening pigs. Nutr. Abstr. Rev., 41: 1-9. Wise, A., 1983. Dietary factors determining the biological activities ofphytate. Nutr. Abstr. Rev., 53: 791-806.