Towards the optimization of canola meal as a protein source for Japanese quails using exogenous feed enzymes
Mnisi, Caven Mguvane
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Broadly, this study was an attempt to valorise canola meal as a source of protein for Japanese quails (Coturnix coturnix japonica) in place of soybean meal using feed enzymes. Growth performance, haematology, serum biochemistry, carcass characteristics and meat quality of the quails were used as indicators in three experiments. The strategy of choice was the use of feed enzymes; a carbohydrase multi-enzyme (endo-1 .4-betaxylanase (> 1-< 3%; 5600 TXU/g, EC no: 232-800-2) and endo-1.4-beta-glucanase (> 0.3-< 1 %; 2500 TGU/g, EC no. 232-734-4)) and a protease (75 '000 PROT/g; EC/IUB no. 3.4.21) mono-enzyme to enhance utilization of CM-based diets. The first objective was to establish the maximum tolerance level of quails for CM without feed enzyme treatment. For four weeks, quails were fed five experimental diets formulated as follows: CON = control diet with no canola meal inclusion, CM25 = control diet in which 2.5% of soybean meal was replaced with canola meal, CM50 = control diet in which 5% of soybean meal was replaced with canola meal, CM125 = control diet in which 12.5% of soybean meal was replaced with canola meal, and CM 175 = control diet in which 17 .5% of soybean meal was replaced with canola meal. Quails fed diet CM 175 had the lowest (P <0.05) feed intake whereas no differences were observed among the other four treatment groups. There were no dietary effects on average weight gain (A WG), gain: feed ratio (GFR) and haematological parameters of quails. All serum biochemical parameters, except for alkaline phosphatase (ALP), were not influenced by experimental diets. Quails on CM25 had higher ALP (161.0 U/L) than those on CON diet (37.3 U/L). Carcass characteristics and dressing percentage of quails across diets were also observed to be similar. Diets influenced the length of small intestines with quails fed diets CON and CM50 having the longest small intestines, which did not differ (P >0.05). No dietary effects were observed in meat quality parameters immediately and 24 h post slaughter, except for meat chroma measured 24 h post slaughter. Quails fed diet CM25 had the highest chroma (7 .39) while those on diet CM125 had the lowest (3 .58). It was, therefore, established that CM can replace SBM in quail diets up to 12.5% without compromising the birds' growth performance, health and quality of meat. The highest inclusion level of canola (CM 175) reduced feed intake, which could be a result of higher levels of fibre and non-starch polysaccharides in the diet. It was hypothesized that the use of feed additives such as enzymes may improve the utilization of CM in quails allowing its inclusion at levels higher than 12.5%. Another trial was, therefore, designed to investigate the potential to enhance the utilization of diets containing CM beyond the 12.5% level tolerated by quails through the use of a dietary carbohydrase multi-enzyme. Thus, the effect of including a carbohydrase multi-enzyme in canola-based quail diets on growth performance, haemo-biochemical parameters, carcass characteristics and meat quality traits was investigated. The application of this multi-enzyme was aimed to improve the utilisation of canola by breaking down the presence of non-starch polysaccharides (NSP) such as glucans and xylans that are known to interfere with digestion and negatively affect feed intake. In this study, CM was only included at 17.5%, a level higher than the maximum tolerable inclusion rate (12.5 %) established in experiment one. For three weeks, quails were fed five dietary treatments formulated as follows: CON = control diet (a commercial growers diet with no CM inclusion), CM0 = control diet in which 17.5% of soybean meal was replaced with CM, and CM0 diet in which a carbohydrase multi-enzyme was added at a rate of 5%, 10% or 15% (CM50, CMlO0 and CM150, respectively). There was a significant diet x week interaction on weekly feed intake indicating that the effect of the diet changed as the quails matured. In both weeks 8 and 9, feed intake showed significant differences between diets. Diets had no influence on haematology and serum biochemical parameters of Japanese quails. Adding the carbohydrase multi-enzyme had no significant effect on internal organs, carcass and meat quali ty of quails. It was, therefore, concluded that the carbohydrase multi-enzyme treatment does not improve the utilisation of a CM-based quail diet. As another attempt to improve the utilisation of CM, the potential of a protease mono-enzyme treatment of canola-based diets to enhance growth performance, haemo-biochemical parameters, carcass characteristics and meat quality parameters in Japanese quails was investigated. For four weeks, quails were offered 5 dietary treatments formulated as follows: CON = control diet (a commercial growers mash with no CM inclusion), CM0 = control diet in which 17.5% of SBM was replaced with CM, and CM0 diet treated with 10, 20 and 30% of protease enzyme (CMlO, CM20 and CM30, respectively). Protease inclusion had no significant effect on feed intake, weight gain, GFR, haemo-biochemical parameters, internal organs, carcass characteristics, and meat quality traits. It was, therefore, clear that the inclusion of protease feed enzyme did not enhance the value of CM as a protein source in Japanese quail diets. The inclusion of either a carbohydrase multi-enzyme or a protease mono-enzyme did not improve the utilisation of a CM-based quail diet. It is, therefore, recommended that the inclusion rate for canola meal as a replacement for SBM in Japanese quail diets be capped at 12.5% and that there is no benefit in applying feed enzymes where higher CM inclusion levels are used.