Influence of pellet length changes at 4, 5 and 6 weeks of age and two pellet diameters on growth performance and carcass characteristics of broiler finishers

A 2 x 4 factorial arrangement of treatments was used to evaluate the effects of two pellet diameters and four pellet length-week combinations on the growth performance and carcass characteristics of broilers (days 22 to 42). A broiler finisher diet based on wheat and soybean meal was formulated. Pelleted diets were manufactured in four different sizes: (i) 3 mm diameter (D3) and 7 mm length (L7), (ii) D3, 9 mm length (L9), (iii) 4.76 mm diameter (D4.76), L7, (iv) D4.76, L9. The four pellet sizes were then used to develop eight feeding treatments: (i) D3 and L7 pellets during weeks 4, 5, and 6 (L777); (ii) D3 and L7 during weeks 4 and 5, and L9 during week 6 (L779); (iii) D3 and L7 during week 4, and L9 during weeks 5 and 6 (L799); (iv) D3 and L9 during weeks 4, 5, and 6 (L999); (v) D4.76 and L7 during weeks 4, 5 and 6 (L777); (vi) D4.76 and L7 during weeks 4 and 5, and L9 during week 6 (L779); (vii) D4.76 and L7 during week 4, and L9 during weeks 5 and 6 (L799); (viii) D4.76 and L9 during weeks 4, 5, and 6 (L999). Increasing the pellet length from 7 to 9 mm increased pellet hardness at both pellet diameters and improved the pellet durability index in D3 pellets but had no effect in D4.76 pellets. Over the whole trial period (days 22-42), birds fed D3 pellets were heavier and had lower feed per gain and higher carcass yield than those fed D4.76 pellets. Feeding length-week combination L999 resulted in lower carcass yield than L777, L779, and L799. Overall, it is concluded that whilst broiler finishers express a preference for a smaller pellet diameter, there is no negative effect of pellet length (up to 9 mm) on performance parameters even when offered as early as day 21.