The nutritional value of navy bean (Phaseolus vulgaris) following autoclaving of dry extrusion as a mixture with soya beans for growing pigs.

Abstract

Animal Production in Australia Vol. 15 THE NUTRITIONAL VALUE OF NAVY BEAN (PHASEOLUS VULGARIS) FOLLOWING AUTOCLAVING OR DRY EXTRUSION AS A MIXTURE WITH SOYA BEANS FOR GROWING PIGS K.C. WILLIAMS*, A.R. NEILL* and M.H. MAGEE* SUMMARY The apparent digestibility of dry matter, organic matter, crude protein and energy determined by substitution were 83.9, 85.9, 87.6 and 84.9% for a blend (55:45) of navy bean and soya bean (NB-SOY) extruded at 146OC; 93.5, 93.9, 97.6 and 94.5% for full-fat soya bean (FF-SOY) extruded at 140�C; and 93.9, 94.7, 94.0 and 93.3% for navy bean (NB) autoclaved at 126OC for 15 minutes respectively. The nutritive value of isonitrogenous and isoenergetic levels of these processed beans, raw NB-SOY and NB-SOY extruded at 121, 135 or 157OC was assessed by pig growth assay. The raw NB-SOY diet caused severe scouring and was fed only for two weeks. Growth rate and feed conversion of pigs fed extruded NB-SOY improved as the extrusion temperature increased to 135OC but declined with higher temperatures. The nutritive value of isoenergetic levels of autoclaved NB and extruded FF-SOY was similar and significantly better than all extruded NB-SOY supplements apart from that extruded at 135OC. INTRODUCTION Navy beans (NB) and other dry beans (Phaseolus vulgaris) rejected for canning are often available in large quantities for feeding to livestock. These beans contain 22 to 30% crude protein and though low in methionine (1.2 g/l6 g N) are a good source of lysine (7.1 g/16 g N) and other essential amino acids (Tobin and Carpenter 1978). However, the beans contain toxic lectins which interfere with nutrient uptake and protein utilization (Pusztai et al. 1979). Conventional dry cooking processes such as roasting have not been fully effective in detoxifying the raw dry bean; autoclaving and other wet cooking methods have been effective (Yadav and Liener 1977; Carpenter 1981) but such methods have limited application for on-farm processing. Extrusion processing has been advocated by Harper (1979) as an effective yet simple means of eliminating growth inhibitors from soya beans and many other feedstuffs. The efficacy of dry extrusion processing in detoxifying NB is reported in this paper. MATERIALS AND METHODS Bean Processing NB could not be dry extruded alone as its low fat content caused excessive frictional resistance in the extruder? However, NB could be extruded as a blend with full-fat soya bean (FF-SOY) if it did not exceed 60% of the mixture. A 55:45 blend of NB and FF-SOY (NB-SOY) was evaluated in this study. NB-SOY was extruded at exit temperatures of either 121, 135, 146 or 157OC. For comparison, FFSOY was extruded at 140�C and NB was autoclaved for 15 minutes at 126OC. Analyses (i) Feed and faeces Proximate and energy analysis of the individual ingredients were determined according to the procedures described by Connor et al. (1971). A *Dept. of Primary Industries, Animal Research Institute, Yeerongpilly, Qld 4105, f-INSTA-PRO Model 500 Dry Extruder - Tripple F P/L, Des Moines, IOWA, U.S.A. 635 Animal Production in Australia Vol. 15 Beckman 12OC amino acid analyser following hydrolysis of samples 18 h. Cystine was determined as composition of the major dietary was used for the determination of amino acids with 6N HCl at llO�C under an atmosphere of N2 for cysteic acid after performic acid oxidation. The ingredients is given in Table 1. (ii) Statistical Data were subjected to an analysis of variance appropriate to the design using prepared programmes for a C.D.C. CYBER 76 computer. Table 1 The as-fed crude protein (CP), fat, lysine (Lys), methionine and cystine (M+C) t threonine (Thr) and gross energy (GE) content of the feedstuffs Digestibility determination - Experiment 1 Theo apparent digestibility of 146OC extruded NB-SOY, 140�C extruded FF-SOY and 126 C autoclaved NB was determined by substitution procedures. A basal diet and three test diets in which the respective test protein sources replaced 25% of the basal diet were fed to eight male pigs in accordance with a replicated 4 x 4 latin square design. Pigs were confined individually in digestibility crates and fed daily an amount of feed equal to 6% of live weight0'75. Total collections of faeces were made over 5 d periods and a period of similar duration was allowed between diet changes, Live weights, ?SD, of the pigs at the start and finish of the experiment were 19.4 2 0.60 and 31.6 + 0.68 kg respectively. Growth assay - Experiment 2 Isonitrogenous amounts of NB-SOY (raw and after extrusion at 121, 135, 146 or 157OC), extruded FF-SOY and autoclaved NB were compared by pig growth assay when incorporated as the sole protein supplement of a wheat based diet. Vegetable oil was added to the diets to offset differences in the fat content between the supplemental protein sources; a second autoclaved NB diet without added vegetable oil was formulated. Composition of the diets is detailed in Table 2. Table 2 Composition (g/kg) of the diets fed in the growth assay experiment t Contained (g/kg): CaHP04, 22.5; NaCl, 2.5; Vitamin and trace mineral premix, 4. 636 Animal Production in Australia Vol. I.5 Thirty two female and 24 male pigs were stratified on live weight at 10 weeks of age into groups of eight of like sex. Within groups, pigs were assigned at random to one of the eight diets. Pigs were fed daily an amount of feed equal to 10% of live weight0'75 as two equal meals at 07.30 and 15.00 h. Adjustments to the daily feeding allowance were made following the weekly weighing of the pigs. Live weights, &SD, of the pigs at the start and finish of the growth assay were 22.0 + 1.70 and 50.9 2 1.36 kg respectively. RESULTS The apparent digestibility of the diets and the values calculated for the individual test protein sources in Experiment 1 are given in Table 3. Table 3 Apparent digestibility of dry matter (DM), organic matter (OM), crude protein (CP) and energy (E) in diets and test protein sources In Experiment 2, raw NB-SOY (diet 1). weeks of feeding, the (ADG) t feed conversion remaining seven diets severe scouring and weight loss occurred in all pigs fed the As these effects showed no signs of diminishing after two diet was withdrawn from the experiment. Average daily gain ratio (FCR) and daily feed intake (DFI) of the pigs fed the are presented in Table 4. Table 4 Average daily gain (ADG) , feed conversion ratio (FCR) and daily feed intake (DFI) of pigs fed in Experiment 2 DISCUSSION The apparent digestibilities of autoclaved NB, extruded FF-SOY and 146OC extruded NB-SOY were high although those of the latter were somewhat lower than for either of the other two protein sources. This result was probably due to the slight over cooking of the NB-SOY during the 146OC extrusion process. In the growth assay, pig performance on diets containing NB-SOY improved as the extrusion temperature increased to 135OC but then declined with higher extrusion temperatures. Thus, the optimum temperature for dry extrusion processing of NB-SOY appears to be about 135OC which is similar to the 135 to 138OC range advocated by Harper (1979) for soya beans. 637 Animal Production in Australia Vol. I5 Performance of pigs fed the autoclaved NB in the growth assay was greatly improved by the addition of vegetable oil to the diet. The addition of oil was calculated to increase the digestible energy content of the autoclaved NB diet from 14.0 to 14.9 MJ/kg. However, it obviously also had a marked effect on the palatability of the diet as DFI increased significantly from 1.0 to 1.4 kg even though all pigs were fed restrictively. The palatability of the diet influencing the performance of the DFI irrespective of the diet fed. following equations: ADG: Y = 0.519X - 0.319 FCR: Y = -2.47X + 6.19 where X is DFI in kg. as indicated by DFI was the dominant factor pigs. Both ADG and FCR responded linearly to These relationships are described by the (PcO.01; r = 0.99) (P<O.Ol; r = 0.97) This dependence of ADG and FCR on DFI can be interpreted in a number of ways. It may indicate that each of the processing conditions examined in the study was effective in destroying the toxic substances in the raw bean but had variable effects on palatability. Thus, what feed was eaten by the pigs was efficiently utilized for growth without apparent toxic effect. But this does not explain why the digestibility of 146OC extruded NB-SOY was apparently lower than either extruded FF-SOY or autoclaved NB. Alternatively, the continued presence of toxic substances in the processed bean may have restricted feed intake to levels such that overt toxicity did not occur. Such explanation though, does not explain the inferiority of NB-SOY when extruded at temperatures above 135OC. Thus, it seems likely that extrusion temperatures of 135-140�C were needed to destroy the toxins but heat damage to the protein occurred with higher temperatures. This work autoclaving or extruded as a efficacious in has shown that the toxic substances in raw NB can be denatured by dry extrusion. NB could not be dry extruded alone but when blend with soya bean at 135OC resulted in a meal equally eliciting pig growth as autoclaved NB of similar energy content. ACKNOWLEDGEMENTS We thank Mr. R. Carter and staff of Bayer (Australia) Ltd. for the extrusion of the beans and the Queensland Navy bean board for the navy bean. REFERENCES CARPENTER K.J. (198 Fd. Technol. CONNOR, J K ., NE ILL, A.R. and BURTON, Husb 11: 387. HARPER, J M-719 79) . CRC Crit. Rev. PUSZTAI, A., CLARKE, E.M.W. and KING, TOBIN, G. and CARPENTER, K.J. (1978). YADAV, N.R. and LIENER, I.E. (1977). 1) l 35: 77. H.W. (1971). Aust. J. Exp. Aaric. Anim. Food Sci. Nutr. 11: 155. T.P. (1979). Proc. Nutr. Soc. Nutr. Abstr. and Rev. C 9. 48: Legume Res. = 17. 1: 38: Z 115. 638