DISCUSSION Performance

The performance outcomes for broilers in this experiment indicated that CM can be fed as a partial replacement (≤ 40%) of soybean meal without significantly decreasing BW or FI if energy values are maintained at a level consistent with that of a typical corn-soy diet. BW data did not reveal a significant decrease over these levels although a trend was noted. This trend

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showed a slight improvement in growth for birds eating 10% CM rates and then slight reductions as CM rates increased as compared to the control group. As for FCR, though none of the

treatments showed significant differences for the first stage of development (starter), the final two stages (grower and finisher) did exhibit significant differences. Birds consuming the control diet consistently achieved the lowest FCR and birds consuming the full CM replacement diets had the highest. All three growth periods showed no developmental trends in FCR results for birds within the intermediate levels (10, 20, 30 and 40%) of CM inclusion groups.

While some research has been conducted with CM as a replacement for SBM, few trials have evaluated levels of 40 and 100% inclusion rates. Even fewer researchers have examined processing parts yield of broilers fed CM as a protein source. A summary of other research studies containing CM in broiler diets is found in Table 10.

Body Weight, Feed Intake, Feed Conversion Ratio, and Mortality

Results for this study were compared with the previous findings from the following scientists for BW, FI, FCR, and MORT. Elwinger and Saterby, (1986) reported in their 35 day- experiment that feeding diets with 12 to 20% of a low glucosinolate rapeseed meal did not adversely affect BW, FI or MORT. Our findings disagreed with Elwinger and Saterbys’ findings for FCR. They reported no significant difference for CM inclusion diets as compared to the control, however, our findings showed differences occurring between the control group and the CM inclusion groups. Salmon et al., (1981) evaluated the use of canola meal in broiler diets with low and high crude protein and nutrient density. These researchers incorporated canola meal into wheat-based broiler diets at up to 28.1% in starter diets (0-4 wks.) with either 21 or 23% crude protein (CP) and up to 12.1% in finisher diets (4-8 wks.) with either 17 or 19% CP. Confirming our results, Salmon reported that live weight gain and MORT were unaffected by

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canola meal when diets were maintained isocalorically. Thomke et al., (1983) conducted

numerous studies using a low-glucosinolate rapeseed meal (RSM) of Swedish origin. Our results were in agreement with Thomke et al., (1983) findings who reported that feeding meal from solvent extraction processing to broilers in two separate experiments resulted in unaltered BW or FI as compared to soybean meal. However, Thomke et al., (1983) found depressed growth for broilers fed RSM at a 20% substitution amount from prepress solvent processing. Prepress solvent processing resulted in an incomplete oil extraction and Thomke et al., (1983) accredited this reduction in weight to activity of the enzyme myrosinase that would be inactivated with proper processing of the RSM. Our findings are in agreement with Perez-Maldonado et al., (2003) who reported that 20% of a solvent extracted or a solvent extracted-extruded canola meal could be used during the starter phase and 30 % could be used in finisher diets formulated on a digestible amino acid basis without adverse effect on BW. However, our findings disagreed with Perez-Maldonado et al., (2003) for FCR and FI. Our data showed significant differences in FCR occurring between the control group and the CM inclusion groups. Perez-Maldonado et al., (2003) reported a reduction of FI compared to control during the finisher phase. The reduction in FI reported by Perez-Maldonado et al., (2003) could have been caused by a reduction in pellet quality that would have been present with additional supplemental fat to maintain diets

isocalorically. Our findings were also in agreement with Ahmad et al., (2007) who reported that canola meal could be incorporated at 20% and fed 1 to 28 d without any adverse effects on broiler BW, FI, or MORT. However, the results observed in our experiment were in

disagreement with Hickling, (2001) who recommended a maximum inclusion level of 15% canola meal in standard broiler diets. Nassar and Arscott (1986) reported satisfactory BW and FI when canola meal was used in both broiler starter (19.2%) and finisher (16.3%) diets replacing

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up to 50% of soybean meal and decreased performance at inclusion rates of 75 and 100% replacement.

Although the results are in agreement with the above scientists in the mentioned

categories, the findings are in disagreement with Leeson et al., (1987) who reported canola meal could replace 100% of the soybean meal in broiler rations without any effect on feed intake, weight gain or feed efficiency.

Processing

Our results were in agreement with the findings for carcass dress percentages of Naseem et al., (2006), Khan et al., (2006), Ajuyah et al., (1991), and Montazer-Sadegh et al., (2008) who reported no significant differences for birds eating CM at inclusion rates ≤ 25% when compared to control diets. Taraz et al., (2006a) reported no significant differences in carcass weights for CM levels of 0, 25, 50, and 75% replacement. Ajuyah et al., (1991) reported a reduction in carcass weights with CM inclusion rates of 20%. Our findings of a reduction in carcass weight for broilers fed 40 and 100% replacement CM were in disagreement with both of these studies. Montazer-Sadegh et al., (2008) reported that CM up to 16% had no impact on carcass weights. For the parts yield category of breast weight, our findings related no significant decrease through the 30% group compared to control with improved breast weight in birds fed 10% CM, but McNeill et al., (2004) reported a linear decline as CM was included at 10 and 20%. The findings of our experiment disclosed noteworthy loss in breast weight as a percentage of carcass when birds were fed amounts of CM at 20% rate and this was in disagreement with Ajuyah et al., (1991)and Naseem et al., (2006) who reported similar breast percentage (%) carcass results with birds consuming 10, 20, and 25%.

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CONCLUSION

These data suggest that canola meal can be used as a partial replacement for SBM (<40%) in isocaloric broiler diets when formulated on a digestible amino acid basis without significantly effecting BW, FI, FCR, or Mortality. However, processing data suggested CM cannot exceed 10% without significantly impacting breast weights. More work is needed to define proper usage levels in diets without excessive levels of supplemental fats.

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REFERENCES