RESUMEN
This study aimed to induce spiking mortality syndrome (SMS) in 10-day-old broiler chicks by changing feed particle size (crumble feed to pellet feed) and/or feed source location (from a small feeder at the pen's center to a large feeder at the front of the pen), followed by full day feed deprivation of all broiler chicks on day 11. In total, 396-day-old male Ross 308 broiler chicks were randomly assigned to 4 treatments (Con: without change in feed particle size and feed source location; Par: changing crumble feed to pellet feed on day 10; Loc: changing feed source location on day 10; LocPar: changing both feed particle size and feed source location on day 10). Each treatment consisted of 9 replicate pens with 11 chicks each. Each treatment was applied at 09:00 on days 10 and 11. On both days, chicks with SMS were identified based on clinical symptoms (down in sternal or lateral recumbency, hyperventilation). Plasma glucose, 3, 3', 5-triiodothyronine (T3), thyroxine (T4) concentrations, insulin, and liver glycogen concentrations of chicks without (normal) and with SMS were measured. Proportional organ and digestive tract including content weights were recorded. Broiler behavior was assessed hourly from 08:30 to 17:30 on day 10. On day 10, the Par, Loc, and LocPar groups spent significantly less time feeding and more time lying down compared with the Con group. On days 10 and 11, SMS clinical signs were observed around 2.5 to 3.5 h after the initiation of treatments, and the Loc group had the most SMS morbidity level. Spiking mortality syndrome chicks had significantly less digestive tract contents compared with Normal chicks on day 10. Spiking mortality syndrome was induced successfully with the treatments, according to their significantly reduced plasma glucose, insulin, T3 and T4 concentrations as well as liver glycogen content. A significant correlation between plasma glucose and liver glycogen was observed in SMS chicks. In conclusion, management factors inducing the reduction or absence of feed intake on day 10 or day 11 can trigger the occurrence of SMS in young broiler chicks.