Effect of different pellet lengths and diameters on growth performance and intestinal function of young pigeons

Manipulating pellet size provides a potential approach to improving performance in poultry. However, research is limited on the appropriate pellet size required by young pigeons. Thus, effect of pellet length and diameter on growth performance and intestinal function of young pigeons was investigated in two experiments. In Experiment 1, 150 two-month-old young White King pigeons were fed pellets with 5 (control, CON)-, 7-, and 9-mm length for 3 months, respectively. Compared to the CON, feeding 7- and 9-mm length pellets decreased body weight at 3 months of age (P = 0.008), and body weight at 4 months of age (P = 0.031) was inhibited by 9-mm length pellets. Interestingly, feed-to-gain ratio of young pigeons fed pellets of 7-mm length during 4 to 5 months was lower than that of other 2 groups (P = 0.043). In male birds, feeding 9-mm length pellets decreased (P = 0.031) duodenal crypt depth (CD) compared to other 2 groups and increased (P = 0.021) duodenal villus height (VH):CD ratio compared to the CON; feeding 7-mm length pellets decreased (P = 0.040) ileal VH compared to the CON. In female birds, VH in both duodenum (P < 0.001) and jejunum (P = 0.023) were increased by 9-mm length pellets compared to the CON. Young pigeons given 7- and 9-mm length pellets had lower duodenal maltase activity (female, P = 0.014) compared to the CON. Feeding 9-mm length pellets reduced duodenal sucrase activity (P = 0.028) and increased ileal maltase (P < 0.001) and sucrase (P = 0.036) activities in female pigeons compared to 5- and/or 7-mm length pellets. Additionally, ileal sucrase activity in male birds fed 7-mm length pellets was higher (P = 0.004) than that in other 2 groups. In Experiment 2, 150 two-month-old young White King pigeons were fed pellets with 2 (CON)-, 3-, and 4-mm diameter for 3 months, respectively. Increased diameter pellets enhanced VH (P = 0.002) and VH:CD ratio (P = 0.004), and reduced CD (P = 0.017) in duodenum of male pigeons compared to the CON. In contrary, jejunal CD (P = 0.010) in female birds was increased and ileal maltase (P = 0.038) activity in male birds was decreased by larger diameter pellets. Supplemental 3-mm diameter pellets increased jejunal sucrase activity in male birds compared to those fed other 2 diameters pellets (P = 0.016). We concluded that young pigeons show a preference for shorter length pellets during 2 to 3 months of age, and feeding them longer length pellets at the later stages can improve their intestinal function and compensate for their growth. Furthermore, gender differences were observed in the impact of pellet diameters on intestinal function. These results suggest that, to improve young pigeons performance, it is necessary to produce pellets of different sizes according to their growth stage and gender.