Escherichia coli vaccine and laying hens mortality after a heat stress challenge in tropical climate

Abstract

The objective of the present research was to evaluate a vaccine against E. coli in laying hens in tropical climates and its response to heat stress challenge. About 47880 Bovans White laying hens were assigned at two treatments: 24.806 were vaccinated (sprayed) against Escherichia coli and 23 074, the control treatment were not vaccinated. Two applications were made during breeding, the day 1 and week 12. At 16 weeks were transferred form the breeding farm to the layer farm and were distributed at random in a layer house and identified. The daily mortality in both treatments was recorded. A t-test is performed to determine differences between daily mortality rates, differences were found for the three stages: 16-23 weeks (p<0.05) (0.05+0.04vs0.08+0.12)from23-lto34(p<0.0001)(0.04+0.02vs0.07+0.03) and 34-lto46-2(p<0.0001)(0.04+0.01 vs. 0.08+0.04). Mortalities in this flock were 14.384% for unvaccinated and 8.224% in vaccinated. Regression analysis were performed for cumulative mortalities before and after a heat stress event, finding that the trend lines have different slopes for birds vaccinated and unvaccinated before and after the event. Vaccination againstZi. coli showed a lower mortality in the study conditions and a relation whit heat stress event. © Medwell Journals, 2011.