Effect of almond hulls as alternative ingredients on broiler performance, nutrient digestibility and cecal microbiota diversity

The objective of this study was to evaluate 2 types of almond hulls (prime hulls and California-type hulls) as alternative feed ingredients for broilers. A total of 560 one-day-old Cobb male chicks were randomly placed to 7 experimental treatments with 8 replicates of 10 birds each. Seven treatments consisted of a corn-soybean meal control diet and diets containing prime hulls or California-type hulls at 3, 6, and 9%. The nitrogen-corrected true metabolizable energy, crude protein, and crude fiber from prime hulls and California-type hulls were 1,624 and 1,514 kcal/kg, 4.8 and 5.0%, and 13.1 and 26.45%, respectively. During 0-19 d of age, the inclusion of the prime hulls at 3 levels had no significant effects on growth performance, but the California-type hulls at 9% increased feed intake (P = 0.02) and feed conversion ratio (P < 0.01), compared with control. The prime hulls at 9% decreased (P < 0.01) ileal dry matter and ileal nitrogen digestibility, and the California-type hulls at 9% only decreased ileal dry matter digestibility, but both prime hulls and California-type hulls at 6% had no effects on ileal dry matter digestibility and nitrogen-corrected apparent metabolizable energy compared to control. In addition, inclusion of prime hulls at 3% decreased (P < 0.01) AMEn compared with control group. There were no significant differences in cecal microbiota diversity at a phylum or genus level among treatments, but 9% inclusion rate of the California-type hulls increased (P < 0.05) the population of certain bacteria in the genus Clostridium and Oscillospira compared with control. In conclusion, as a dietary energy and fiber source, the prime hulls can be used at up to 9% without a negative effect on body weight gain, whereas the California-type hulls can be used up to 6%.