L. Garcia  Compean, M.  Itza Ortiz, A. Reyes  Ramirez, H.  Magana-Sevilla, B. Ortiz  de la Rosa, R.  Zamora-Bustillos, J.R. Sangines  Garcia, J.P. Ramon  Ugalde, 
    <I>Escherichia coli</I> Vaccine and Laying Hens Mortality After A Heat Stress Challenge in Tropical Climate,
    Journal of Animal and Veterinary Advances,
    Volume 10,Issue 1,
    2011,
    Pages 96-99,
    ISSN 1680-5593,
    javaa.2011.96.99,
    (https://makhillpublications.co/view-article.php?doi=javaa.2011.96.99)
    Abstract: The objective of the present research was to evaluate a vaccine against <I>E. coli</I> 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 <I>Escherichia coli</I> 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&lt;0.05) (0.05+0.04 vs 0.08+0.12) from 23-1 to 34 (p&lt;0.0001) (0.04+0.02 vs 0.07+0.03) and 34-1 to 46-2 (p&lt;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 against <I>E. coli</I> showed a lower mortality in the study conditions and a relation whit heat stress event.
    Keywords: temperature;mortality;egg layers;THI;E. coli vaccine;heat stress