NUTRITION

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Abstract

In Algeria, 90% of poultry feedstuffs are imported (maize, soyabean, meat meal, mineral and vitamin supplements, various additives) . To reduce these imports, several solutions have been considered, the most important of which is the search for local feedstuffs for substitution. Maize and soyabean are the main sources of energy and protein in poultry diets (Larbier and Leclercq, 1992) but locally produced barley, rye, oat, rape or lupin could be used as substitutes. Lupin in particular has been studied by several authors (Carré and Lacassagne, 1992; Brenes et al., 1993; Alloui et al., 1994; Bedford and Morgan, 1996; Carré and Lacassagne, 1992) . Barley can partially replace maize in poultry diets ( Jeroch and Dänicke, 1995) , but its use is aided by addition of enzymes that eliminate the anti-nutritional factors ( -glucans) contained in this cereal. The aim of this experiment was to investigate the effect of the substitution of maize by barley on production performance (weight, feed conversion, gain) in broilers. The production tests were conducted on 5 groups of 20 ISA broiler chicks. Group 1 received a control diet (no barley and no enzymes) , groups 2 and 4 received a diet containing 100 or 300 g/kg of a local variety of barley, groups 3 and 5 received the same diet as groups 2 and 4 supplemented with 5 g/kg of -glucanase (Table 1) . Each diet contained a mean of 200 g/kg crude protein and 12 MJ/kg AME. We used conventional methods to estimate the chemical composition of raw materials (dry matter, ash, total nitrogen, crude cellulose) . The ADF and NDF fractions were studied using the method of Van Soest (1967) . Statistical analysis was performed using analysis of variance and a post hoc comparison of means. The level of significance was set at 5%. The chemical analysis of barley and maize revealed a similar composition, mainly in protein content (103·0 vs 96·0 g/kg) and N-free extract (NFE) (674·0 vs 702·0) of the two cereals. These results agree with those found by Åman et al. (1985) For both cereals, NFE represents starch and sugar which permits the substitution of maize by barley. Crude cellulose and NDF fraction are higher in barley and represent 173·0 and 48·0 g/kg, respectively. These constituents are considered as antinutritional factors. It is generally considered that -glucanase constitutes a large part of the NDF fraction. -glucan content in barley varies considerably from one variety to another. Indeed, contents varying from 3·7 to 8% have been reported (Hesselman, 1983; Jeroch and Dänicke, 1995) . The results (Table 2) indicate that enzymatic supplementation of diets containing 100 and 300 g/kg barley did not show any significant improvements (P<0·05) . These performances are comparable to the control for mean live weight (1914 g in group 1 vs 1900 g in groups 3 and 5) . Some authors have reported an improvement of performances in broiler chickens when diets were supplemented by enzymes such as -glucanase and xylanase. The rates of incorporation of barley can then be increased to between 350 and 600 g/kg. The improvement in weight and feed conversion was more significant during the period of growth 21