Pre-housing fasting and diet physical form impact broiler chicks’ gastrointestinal development along the first week of housing

This study aimed to evaluate body and gastrointestinal development in broilers chicks subjected or not to pre-housing fasting and different diet physical forms during the first week of housing. Nine hundred chicks were distributed into a completely randomized design in a 3×3 factorial arrangement: 0, 24 and 48 hours(h) of fasting; mashed (MM), crushed (CC) and micropelletized (MP) physical forms. For each fasting period, 300 animals were housed in protection circles with 100 chicks each. On days 1, 3, 5 and 7 of feeding, six animals were randomly selected, previously weighed and euthanized to obtain organs biometrical and histological data. Chicks fasted for 24 h and 48 h were lighter compared to the 0 h group and the 24-h fasting x MP interaction had a positive impact on body weight at d7 (P<0.05). Although fasted chicks presented lower body weight, small intestine, liver and gizzard were heavier, and presented greater yolk sac consumption (YSC; P<0.05). There were no alterations in the duodenal mucosa (DM) in pre-housing fasting animals (P>0.05). Despite the diet physical form and pre-housing fasting interactions for villus height (VH) and absorptive area (AA) on d1, only diet physical form affected DM, where greater VH and AA on d7 were observed in CC and MP groups (P<0.05). Animals fed MP after 48 h fasting presented smaller VH and AA compared to chicks fed the same diet after 24 h and were similar to the 0 h group (P<0.05). On d1, YSC was similar among groups of the same diet, but for those fed with MP(P<0.05). The 48 h-fasted group presented heavier intestines relative weights (IRW) at d1(P<0.05). Furthermore, the 0 h group fed with CC presented higher IRW, whereas MP showed the lowest IRW over the first week (P<0.05). The DM development (kinetics) showed an increase in VH and AA overtime in all groups, which was more pronounced in 48 h-fasting chicks throughout the first week, showing the highest increase in VH when fed with MP (P<0.05). VH:CD ratio was similar along the first week in MP groups, regardless of the fasting period but more pronounced in the 24 h group fed MM and CC (P<0.05). Therefore, 24 h fasting associated to MP diet may be the most efficient management practice. Collectively, these findings suggest pre-housing fasting is strongly associated with diet physical form at the first week of housing and should be considered to achieve greater performance in broilers.