Abstract:
High feed costs are part of any broiler rearing enterprise and continuous effort is required to help overcome this problem. The use of a feed expander may be beneficial in improving bird performance and thus increasing the profitability of broiler meat production. Four experiments were conducted to evaluate the performance of birds fed expanded feed in relation to the performance of birds fed non-expanded feed. The effect of feeding birds expanded feed was also tested under heat stress conditions. In this experiment, a significant improvement in cumulative feed conversion ratio (CFCR) was observed for birds fed expanded feed (Chapter 3). Pellet size influenced bird performance as birds fed a 3.2 mm non-expanded feed had a better cumulative FCR than the non-expanded 4.5 mm pellets, and this CFCR did not differ significantly from that in birds fed 3.2 mm expanded pellets (Chapter 4). There is, however, an improvement in the cumulative FCR to two weeks of age in birds fed expanded feed, over that in birds fed non-expanded feed, indicating that expanding of feed improves nutrient availability to the young broiler with a partially developed digestive tract. The effects of expanding feed on the body weight of birds were not consistent between experiments. This might be attributed to expanding temperature, as the feed in Chapters 3 and 4 was expanded at 90°C and not at higher temperatures as in the other chapters. Expanding feed at 90°C may not allow proper starch gelatinisation and alteration of nutrient availability. Expanded feed had better pellet durability than non-expanded feed and there were no significant negative effects on vitamin recovery, enzyme stability and nutrients when feed was expanded at temperatures between 95 and 1 05°C. Pellet quality increased with an increase in expanding temperature. Expanding of broiler feed led to a significant improvement in lipid digestibility (Chapter 6). Expanding of feed at 105°C is recommended as feed expanded at this temperatures tend to have significantly higher AMEn values for broilers than non-expanded feed.
