Daily rhythms of cloacal temperature in broiler chickens of different age groups administered with zinc gluconate and probiotic during the hot?￠????dry season

摘要

The aim of the experiment was to evaluate effects of zinc gluconate (ZnGlu) and probiotic administration on the daily rhythm of cloacal temperature ( t cloacal ) in broiler chickens of different age groups during the hot?￠????dry season. One?￠????day?￠????old broiler chicks ( n ????=????60) were divided into groups I?￠????IV of 15 chicks per group, and treated for 35????days: Group I (control) was given deionized water; Group II, ZnGlu (50????mg/kg); Group III, probiotic (4.125????????????10 6???? cfu/100????mL), and Group IV, ZnGlu (50????mg/kg)????+????probiotic (4.125????????????10 6???? cfu/100????mL). Air dry?￠????bulb temperature ( t db ), relative humidity (RH), and temperature?￠????humidity index (THI) inside the pen, and t cloacal of each broiler chick were obtained bihourly over a 24?￠????h period; on days 21, 28, and 35 of the study. Values of t db (32.10???????±????0.49???°C), RH (49.94???????±????1.91%), and THI (38.85???????±????0.42) obtained were outside the thermoneutral zone for broiler chickens, and suggested that the birds were subjected to heat stress. Application of the periodic model showed disruption of daily rhythm of t cloacal in broilers on day 21, which was synchronized by probiotic administration. The administration of probiotics or ZnGlu????+????probiotics to a greater extent decreased the mesor and amplitude, delayed the acrophases of t cloacal in broilers, especially at day 35, as compared to the controls. Overall, the t cloacal values in broiler chickens administered with probiotic alone (41.25???????±????0.05???°C) and ZnGlu????+????probiotic (41.52???????±????0.05???°C) were lower ( P ????