F. A. Igbasan

Comparative studies on the in vitro properties of phytases from various microbial origins.

The physical and chemical properties of six crude phytase preparations were compared. Four of these enzymes (Aspergillus A, Aspergillus R, Peniophora and Aspergillus T) were produced at commercial scale for the use as feed additives while the other two (E. coli and Bacillus) were produced at laboratory scale. The encoding genes of the enzymes were from different microbial origins (4 of fungal origin and 2 of bacterial origin, i.e., E. coli and Bacillus phytases). One of the fungal phytases (Aspergillus R) was expressed in transgenic rape. The enzymes were studied for their pH behaviour, temperature optimum and stability and resistance to protease inactivation. The phytases were found to exhibit different properties depending on source of the phytase gene and the production organism. The pH profiles of the enzymes showed that the fungal phytases had their pH optima ranging from 4.5 to 5.5. The bacterial E. coli phytase had also its pH optimum in the acidic range at pH 4.5 while the pH optimum for the Bacillus enzyme was identified at pH 7.0. Temperature optima were at 50 and 60°C for the fungal and bacterial phytases, respectively. The Bacillus phytase was more thermostable in aqueous solutions than all other enzymes. In pelleting experiments performed at 60, 70 and 80°C in the conditioner, Aspergillus A, Peniophora (measurement at pH 5.5) and E. coli phytases were more heat stable compared to other enzymes (Bacillus enzyme was not included). At a temperature of 70°C in the conditioner, these enzymes maintained a residual activity of approximately 70% after pelleting compared to approximately 30% determined for the other enzymes. Incubation of enzyme preparations with porcine proteases revealed that only E. coli phytase was insensitive against pepsin and pancreatin. Incubation of the enzymes in digesta supernatants from various segments of the digestive tract of hens revealed that digesta from stomach inactivated the enzymes most efficiently except E. coli phytase which had a residual activity of 93% after 60 min incubation at 40°C. It can be concluded that phytases of various microbial origins behave differently with respect to their in vitro properties which could be of importance for future developments of phytase preparations. Especially bacterial phytases contain properties like high temperature stability (Bacillus phytase) and high proteolytic stability (E. coli phytase) which make them favourable for future applications as feed additives.

Nutritive value of peas for nonruminant diets

Peas, the seeds of Pisum sativum, are produced usually in temperate regions but are accepted as a food source worldwide. Traditionally, nonruminant diets utilized peas which had been rejected by the food industry but specific cultivars of feed (or field) peas also have been developed for livestock use. In view of the diversity of varieties, seeding times (spring or winter-sown) and agronomic conditions during the growing season, there is a considerable range in the composition and nutritive value of peas. The seed coat (hull) represents 70 to 140 g kg-’ of the total weight and consists mainly of non-starch polysaccharides, while the major components of the dehulled pea are starch (- 450 g kg-‘) and protein ( - 250 g kg-‘). Published energy values for the whole seed range from 12.2 to 16.6 MJ ME kg-’ DM for pigs and 10.1 to 12.8 MJ TME, kg-’ DM for poultry. Reported analyses for crude protein vary from 156 to 325 g kg-’ DM, while content and availability of the constituent amino acids vary also with cultivar, seed type and analytical methods. Most concerns about low digestibilities relate to the sulphur amino acids and tryptophan. Potentially detrimental constituents in raw peas include anti-proteases, haemagglutinins, phytic acid and tannins although these appear negligible in Canadian peas. When analytical data are lacking, the following limits to use of peas are suggested: 100, 200 and 350 g kg-‘, respectively, in pig starter, grower and finisher diets; 200 g kg-’ in broiler, 250 g kg-’ in turkey and 300 g kg - ’ in layer diets.

The effectiveness of an Escherichia coli phytase in improving phosphorus and calcium bioavailabilities in poultry and young pigs.

The effectiveness of an Escherichia coli phytase in comparison with a commercially available Aspergillus phytase in improving the bioavailability of phosphorus in broilers, layers and young pigs was studied in three separate experiments. Three basal diets, marginally deficient in dietary P mainly provided as phytate, were formulated. Both phytases were added to the diets at the rate of 500 U/kg diet. The phytases significantly (P ≤ 0.05) improved the availability of phytate P to broilers, layers and young pigs. Aspergillus and E. coli phytases enhanced the pre‐caecal digestibility of P by 11 and 29% for broilers and 18 and 25% for layers, respectively. Total tract digestibility of P (P balance) was also enhanced but with smaller magnitude. In pigs, total tract digestibility of P was improved by 33 and 34% by Aspergillus and E. coli phytases, respectively. Under the conditions of this study, it was observed that E. coli consistently, though with small magnitude in layers and pigs, enhanced the availability of phytate P at the same range or slightly better than Aspergillus phytase. It was only in pigs that the availability of Ca was significantly (P ≤ 0.05) improved by addition of both phytases. It can be concluded that E. coli phytase is highly effective in improving the bioavailability of phytate P to broilers, layers and young pigs. This seems to be based on the high proteolytic stability of the enzyme in the digestive tract, as shown recently.

The evaluation and enhancement of the nutritive value of yellow-, green- and brown-seeded pea cultivars for unpelleted diets given to broiler chickens

The evaluation and possible enhancement of the feeding value for broiler chickens of yellow-, green- and brown-seeded pea cultivars were studied in three experiments. In the first experiment, bioavailable energy (AMEn), apparent protein digestibility (APD) and starch digestibility were determined. Dietary AMEn, APD and starch digestibility values were decreased (P ≤ 0.05) with 500 g kg−1 inclusion of peas. The AMEn and starch digestibility were similar (P ≥ 0.05) in yellow- and green-seeded cultivars but lower (P ≤ 0.05) in the brown-seeded cultivar. Significant differences (P ≤ 0.05) were found between the cultivars in APD. The effects of feeding 0, 100, 200 and 400 g kg−1 of these cultivars on the performance of broiler chicks were examined in the second experiment. Concurrently the possibility of alleviating the detrimental effects of antinutritional factors in peas by providing excess (115% of National Research Council (NRC) requirements) crude protein (CP) and essential amino acids (EAAs) to 400 g kg−1 pea-based diets was evaluated. The inclusion of up to 200 g kg−1 of peas did not affect weight gains but feed conversion ratio (FCR) was reduced (P ≤ 0.05) only for the diet containing the brown-seeded peas. When peas comprised 400 g kg−1 of a diet fed to broiler chicks, weight gains and FCR were depressed (P ≤ 0.05). However, this depression was alleviated by supplying excess CP and EAAs to these diets. Feed consumption was not affected by dietary inclusion of peas. The influence of adding pectinase only or in combination with protease to diets in which peas constituted a major dietary protein source was investigated in experiment 3. Supplementation of diets containing 800 g kg−1 peas with pectinase alone increased (P ≤ 0.05) weight gains by 7.3 percentage units, above non-supplemented diets. Feed consumption was also improved (P ≤ 0.05) by the same magnitude. However, feed conversion was not affected. There was no further response observed by adding protease to these diets. It is concluded that broiler chicks can tolerate up to 200 g kg−1 peas in their diets, with satisfactory performance at 400 g kg−1 provided CP and EAAs are supplied at 15% in excess of NRC requirements and addition of pectinase to pea-based diets improved weight gains and feed consumption.

Protein quality of peas as influenced by location, nitrogen application and seed inoculation.

A study was conducted to evaluate the contribution of location, N application andRhizobium seed inoculation to variations in seed protein content and amino acid (AA) composition of field peas. The magnitude of AA variations with protein level and the nature of the relationships that are involved were determined. Regression equations to predict AAs from protein were developed for the cultivar Bohatyr. The experiments were carried out at two locations in southern Manitoba in 1994. The levels of N fertilization investigated were: 56, 75, 100, 125, 150, 200, 250 and 300 kg/ha. At each level of N application, seeds planted were eitherRhizobium inoculated or not inoculated. The combination of location, fertilizer treatments and inoculation yielded 192 samples for chemical analyses. The samples were analyzed for dry matter (DM), N and AA contents. Location and N fertilization had significant (p⩽0.001) effects on seed protein content and AA composition. Seed protein content increased with increasing levels of N application. The response of protein to fertilization was not the same in both locations as evidenced from the presence of interaction (p⩽0.01) between location and N application. Except for methionine and cystine, percent AAs in DM increased with increasing levels of N application. The effects of N application on the concentrations of methionine and cystine were not consistent. On protein basis, the concentrations of AAs decreased with increasing levels of N application. The only exception was arginine which strongly increased in concentration. There was no effect (p⩾0.05) of seed inoculation observed in this study. Strong positive correlations (r>0.80) between seed protein content and AA concentrations expressed as percent of DM were found for all AAs except for methionine (r=0.76) and cystine (r=0.51). When AA concentrations are expressed as g per 16 g N, 15 of the 17 AAs were negatively correlated to seed protein content. Only arginine (r=0.78) and aspartic acid (r=0.17) had positive correlations. The regression equations developed from this study could be used to predict the concentrations of AAs except methionine and cystine for the cultivar Bohatyr once the protein content is known.

The feeding value for broiler chickens of pea chips derived from milled peas (Pisum sativum L.) during air classification into starch fractions

Two pea products, yellow pea chips (WC) and green pea chips (GPC) that were derived from milled peas during air classification into pea starch fractions were evaluated for their nutritional value in three experiments. The products were found to contain 298.3 and 281.3 g kg-’ crude protein, 7.28 and 7.10 g lysine per 16 g N and 1.05 and 0.94 g methionine per 16 g N for YPC and GPC, respectively. The apparent metabolisable energy value of YPC was higher (P I 0.05) than that of GPC, 11.50 vs. 11.28 MJ kg-‘, respectively. A similar result was also obtained with starch digestibility, 81.6 vs. 77.4% (P 5 0.05); however, apparent protein digestibility was similar (P 2 0.05) (experiment 1). In experiment 2, YPC or GPC replaced corn and soybean meal at 0, 150, 300 and 450 g kg - ’ in broiler chick diets. Weight gain and feed conversion ratio (FCR) were similar (P > 0.01) for birds fed the 150 g kg-’ of YPC (397.2 g, 1.41) or GPC (390.4 g, 1.42) diet and the control (403.1 g, 1.38) diet. At 300 and 450 g kg-’ inclusion levels, weight gain (YPC, 377.9 and 345.5 g; GPC, 362.9 and 306.6 g) and FCR (YPC, 1.48 and 1.5 1; GPC, 1.47 and 1.61) decreased significantly (P < 0.01) for both products relative to the control (403.1 g, 1.38). Feed consumption decreased with increasing levels of pea chips in the diets but the effect was significant (P < 0.01) only in those diets containing 450 g kg- ‘. In experiment 3, diets containing 300 g kg-’ of YPC or GPC were supplemented with two levels of DL-methionine to 100% and 120% of the NRC requirements. The performance of these birds was still lower (P < 0.01) than that of birds fed the control diet. The fact that these pea by-products at 300 g kg-’ inclusion level with methionine supplementation were unable to sustain broiler performance equal to birds fed a conventional corn-soy diet, suggests that they should not be fed to broiler chicks in excess of 150 g kg- ‘.

Growth response and carcass quality of broiler chickens fed on diets supplemented with dietary copper sources

An experiment was conducted to determine the effects of dietary sources of copper on growth performance and carcass characteristics of broiler chickens. Three dietary sources of copper (Cu) namely: copper sulphate (CuSO 4), copper oxide (CuO) and copper acetate were added to a corn-soy basal diet, which was formulated to meet the nutrient requirements of broilers, at 150, 200 and 250 ppm. The control diet had no supplemental Cu. There were ten dietary treatment groups. One hundred and sixty ANAK 2000 broiler chicks were randomly divided into these treatment groups of 16 birds each. Each treatment group was further subdivided into four replicates of 4 birds per replicate. The experimental design was completely randomized with 3 ◊ 3 factorial arrangements of treatments and the trial lasted for 42 days, after a pre-trial period of 14 days. The final body weight, body weight gain, feed intake and feed conversion ratio (FCR) of the birds were determined on weekly basis. At the end of the experiment, two birds per replicate were randomly selected and slaughtered for the evaluation of carcass quality traits. The average final body weight and body weight gain of the birds fed with Cu supplemented diets were significantly (P ≤ 0.05) different from those fed with the control diet. The birds on Cu supplemented diets gained more body weight than birds on the control diet. Birds fed with 200 ppm Cu gained (P ≥ 0.05) more weight than those on other levels of inclusion. Although not significant (P ≥ 0.05), those birds fed with CuO gained more weight than birds on CuSO 4 and Cu acetate. There was no significant (P ≥ 0.05) difference in the average feed intake of birds fed Cu supplemented diets compared to the birds on the control diet. The FCR of the birds fed with supplemented diets was significantly (P ≤ 0.05) lower than that of the birds on the control diet. Those birds fed with Cu supplemented diets utilized feed better than birds on the control diet. Among those fed with dietary Cu salts, those birds on CuO utilized feed better (P ≤ 0.05) than the birds on CuSO 4 and Cu acetate. Dietary Cu supplementation had no significant (P ≥ 0.05) effect on carcass quality traits determined. It can be concluded from this study that dietary copper supplementation up to 250 ppm from CuSO 4, CuO and Cu acetate can substantially improve the growth performance and feed utilization of broilers.