The nutritional value of ryegrass-white clover leaf protein concentrate : a thesis presented in partial fulfillment [sic] of the requirements for the degree of Doctor Philosophy in Biochemistry at Massey University
Leaf Protein Concentrate (LPC ) , which was manufactured from a mixture of Ryegrass and White Clover (Lolium perenne and Trifolium repens) at the Ruakura Agricultural Research Centre , was evaluated as a possible protein source for feeding to chickens . The nutritional value of LPC was compared to that of soybean meal ( SBM ) . LPC was shown to have a lower nutritional value than SBM in the growth trials . The addition of methionine or cystine to the diet containing LPC improved both food utilization and weight gain of the chickens . These growth parameters showed the greatest improvement when 2 g methionine/kg diet was added to the LPC diet. The additional quantity of 2g methionine/kg diet was similar to the amount of sulphur amino acid contributed by LPC to the d i e t ; 1.8 g sulphur amino acid from L PC /kg diet. When an equivalent amount of cystine (1.6g) to methionine , on a sulphur basis , was added to the LPC d i e t and fed to chickens , it was shown to support the same amount of growth and maintain a similar food utilisation level as additional methionine . LPC contributed only 0.6g cystine/kg of diet . As this was much lower than the added cystine and/or methionine , it was concluded that the availability of cystine in the whole diet was reduced by the presence of LPC rather than the lack of availability of cystine in LPC alone . The following information was also obtained : - (i) Pancreatic hypertrophy and increased pancreatic enzyme activity (trypsin and chymotrypsin ) occurred due to feeding the LPC diet . (ii) The invitro exhaustive enzyme digestibility study indicated that while the overall digestibility of LPC was approximately 6% lower than that of SBM, none of the individual amino acid digestibility estimates i n LPC diverged markedly from the mean . All LPC amino ac ids were released equally by enzyme hydrolysis . (iii) In contrast to the invitro findings , the in vivo mean amino acid availability estimates for the ingredient LPC (as measured in the excreta) were lower than the corresponding SBM estimates by approximately 1 5% . The cystine availability estimate for the ingredient LPC was only 5 1 . 2% in terms of corrected amino acid availability ( CAAA), and 1 1 . 9% in terms of apparent amino acid availability ( ApAAA). By comparison the cystine availability estimates for the ingredient SBM were 80 . 8% CAAA and 7 5 . 7 % ApAAA. When the diets containing LPC or SBM were assayed by the same technique , the differences in the amino acid availability estimates were markedly reduced . The availability estimates of cystine in the LPC diet were still lower than the other amino acid availability estimates for the LPC diet . These however were only 8-10% lower than the corresponding estimates for the SBM diet. (iv) The mean amino acid digestibility estimates, derived by analysis of the ileal contents of chickens fed with the LPC d i e t were 26% lower than those for chickens fed the SBM d i e t s . The cystine digestibility estimates for the LPC d i e t was approximately 45% lower than the corresponding cystine digestibility estimate for the SBM diet. These results indicated that digestion and/or absorption of the LPC diet was probably being retarded as compared with the SBM diet. (v) Supplementation of the LPC diet with the antibiotic , Neomix , gave an improvement in growth and an increase in the mean amino acid availability ( measured by excreta analysis ) of approximately 7%. This indicated that the gut microflora were influencing the nutritional value of LPC . Feeding the LPC diet in comparison to feeding the SBM diet also tended to increase the level of c1 9 cyclopropane fatty acid in the excreta. This indicated that feeding the LPC diet was influencing the nature and/or activity of the microfloral population . The physiological and metabolic effects of feeding r aw soybean meal and/or trypsin inhibitors , which have been reported in the literature, included pancreatic hypertrophy , increased pancreatic proteolytic enzyme activity , retardation of ileal protein digestibility and.an influence by gut microflora . Each of these factors were characteristic of chickens fed the 1PC diet. It was therefore concluded that the additional need for cystine or methionine by chickens fed the 1PC diet , was due to the presence of trypsin inhibitors in the 1PC . It was demonstrated, by feeding 1 - (methyl 14c) methionine that phenolic compounds were being methylated . However the need for detoxification of aromatic compounds , which required methionine (as a methyl donor ) and /or arginine ( ornithine ) , could not explain the growth depression experienced by chickens fed the unsupplemented 1PC diet. The feeding of 1- (methyl 14c) methionine in conjunction with the 1PC diet also indicated that the digestibility of methionine was not being hindered during the digestive process by preferential binding with other compounds in the 1PC diet. I t was concluded from the result s of this study that 1PC adequately supplemented with methionine , could b e a useful addition to the range of ingredients available for use in poultry feeds.
Ryegrass, Lolium perenne, White clover, Trifolium repens, Chicken feed, Poultry feed, Protein, Animal nutrition
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