Improving the nutritive value and utilisation of non-conventional protein feed resources in smallholder village chicken production systems.

Abstract

Poultry production is one of the most important activities for creating wealth in developing countries. This study was conducted to assess methods of improving the nutritive value and utilization of cowpeas, and ameliorating the negative effects of aflatoxins in chicken feeds. Farmer perceptions on feed resource availability and utilization of non-conventional feed resources for indigenous chickens were investigated in three Mozambican districts (n=240). Scavenging was the major source of feeds for chickens and two out of five of the respondents experienced feed shortages during the dry season (from May to October/November). Nearly 90 % of the respondents were willing to use novel protein sources (e.g. houseflies, earthworms and snails) as chicken feed. Household leftovers were identified as the major supplemental feed source, followed by kitchen waste, then crushed grain and maize bran, suggesting protein is deficient in chicken diets. Most often, the kitchen scraps include foods that are spoiled with mould or damaged by insects and are not used in human consumption. Farmers had no specific biases against the use of non-conventional feed ingredients for chickens. Households in mountain zones were more likely to use maize bran for feeding chickens than those near dams (odds ratio 8.26). Educated farmers were three times more likely to feed chickens with maize bran (odds ratio 3.01). Topography highly influenced household’s likelihood of experiencing feed shortage. Farmers in mountains zones were 2.3 times more likely to experience feed shortage than the farmers in dam areas. Households headed by females were 1.2 times more likely to experience feed shortage than households headed by men. Chemical composition, amino acid digestibility and the true metabolisable energy of cowpeas and pigeon peas- under various processing (heat and enzyme) treatments, as well as effects on growth performance, growth of internal organs, and gut health were investigated through feeding trials. The precision-fed cecectomized rooster assay was used to determine amino acid digestibility and true metabolizable energy of cowpeas. Crude protein (CP) content was higher (P<0.05) for raw nhemba cowpea (228 g/kg) in comparison to raw black-eyed beans (207 g/kg). Except for tryptophan, amino acid contents were higher (P<0.05) in nhemba than in black-eyed beans. Trypsin inhibitor levels in nhemba averaged 6700 TIU/g, whereas the black-eyed beans contained 2200 TIU/g. Both roasting and extrusion increased the CP content of cowpeas. Extruded and roasted black-eyed beans contained higher (P>0.05) amino acid concentrations compared with raw black-eyed beans. Heat treatment had no effect (P>0.05) on the levels of methionine, threonine, proline, alanine, valine or leucine. The amino acid content of nhemba was reduced (P<0.05) by heat treatment. Heat treatment reduced (P<0.05) the concentration of trypsin inhibitors to below 2000 TIU/g. Roasting had no effect (P>0.05) on amino acid digestibility in black-eyed beans, but increased amino acid digestibility of nhemba by 3.4 %. True metabolizable energy (TMEn) was significantly increased (3535 versus 3164 kcal/kg) by extrusion. Body weight gains, feed conversion and gut morphology demonstrated that, despite the overall lower nutritional value of local legumes compared to soybeans, extruded cowpeas with enzymes, or roasted pigeon peas, could improve bird production and gut health. The effectiveness of diatomaceous earth (DE), bentonite clay (BC) and turmeric (TUM) in ameliorating the toxic effects of aflatoxin B1 (AFB1) was assessed in growing chickens. Addition of AFB1 to the BD depressed (P<0.05) BWG and feed intake (FI) when compared to control chickens. The addition of BC to the AFB1 diet reduced the severity of the histological lesions caused by aflatoxins. Body weight gain (BWG), feed intake (FI) and feed: gain of chickens fed the adsorbents (BC or DE) alone were not different (P>0.05) from those of control chicks. In contrast, chicks fed the 2.0 mg AFB1/kg diet alone had significantly depressed (P<0.05) BWG and FI when compared to control chicks. Addition of 0.50 % BC did not improve (P>0.05) feed intake and growth rate of chickens fed the AFB1 diet. Chickens fed a control diet plus BC and either DE or TUM were as healthy as the control chicks. Bentonite clay gave a higher (P<0.05) body weight gain than the control chicks. Compared with chicks fed AFB1 alone, the addition of TUM into the AFB1 diet was not effective in preventing or reducing the increase in relative liver or kidney weight. Addition of a combination of both BC and TUM to the AFB1 diet prevented the increase in relative liver and kidney weights caused by AFB1. In contrast, the addition of a combination of DE and TUM to the AFB1 diet was not effective in reducing or preventing the increase in the weight of these organs caused by AFB1. Chickens fed the AFB1 diet supplemented with combinations of BC and TUM or DE and TUM had lower (P<0.05) concentrations of serum calcium compared to control birds but similar (P>0.05) concentrations of Alanine aminotransferase (AST), Gamma-glutamyltransferase (GGT), and uric acid (UA) to that of chicks fed AFB1 only. In conclusion the addition of TUM alone into the AFB1 diet also did not demonstrate an ameliorating effect. The addition of the combination of BC and TUM to the AFB1 diet was not as effective in reversing the effect of AFB1 on BWG as the combination of DE and TUM. When BC and DE were fed in combination with TUM, the results showed a reversal in the comparative individual effectiveness of BE and DE in their ameliorating effect on BWG.