William Narváez-Solarte

Ability of non-linear mixed models to predict growth in laying hens

In this study, the Von Bertalanffy, Richards, Gompertz, Brody, and Logistics non-linear mixed regression models were compared for their ability to estimate the growth curve in commercial laying hens. Data were obtained from 100 Lohmann LSL layers. The animals were identified and then weighed weekly from day 20 after hatch until they were 553 days of age. All the nonlinear models used were transformed into mixed models by the inclusion of random parameters. Accuracy of the models was determined by the Akaike and Bayesian information criteria (AIC and BIC, respectively), and the correlation values. According to AIC, BIC, and correlation values, the best fit for modeling the growth curve of the birds was obtained with Gompertz, followed by Richards, and then by Von Bertalanffy models. The Brody and Logistic models did not fit the data. The Gompertz nonlinear mixed model showed the best goodness of fit for the data set, and is considered the model of choice to describe and predict the growth curve of Lohmann LSL commercial layers at the production system of University of Antioquia.

Alteraciones Hematológicas y Zootécnicas del Pollo de Engorde bajo Estrés Calórico

espanolEl objetivo de este trabajo fue determinar los cambios hematologicos y zootecnicos del pollo de engorde criado bajo estres calorico cronico inducido y en las condiciones de temperatura ambiental del Piedemonte Amazonico colombiano. Se utilizaron 500 pollos machos, de dos lineas comerciales, de 21 dias de edad, distribuidos en un diseno en bloques completamente aleatorizados, en un esquema factorial 2x2 (dos lineas de pollo y dos condiciones de temperatura), cinco repeticiones por tratamiento y 25 animales por unidad experimental. Se evaluo recuento leucocitario, leucograma diferencial, hemoglobina, relacion heterofilo/linfocito, hematocrito, consumo, ganancia de peso, conversion alimenticia y mortalidad. El factor linea no tuvo efecto sobre las variables evaluadas (p>0,05). Existio diferencia (p Englishhe objective of this work was to determine hematologic and zootechnical changes in broiler breeders raised under induced chronic heat stress in the Amazon foothills at room temperature conditions. Five hundred male chickens from two different production lines were used, 21 days old each. They were randomly distributed in a block design with a factorial scheme 2x2 (two chicken production lines and two conditions of temperature), five repetitions per treatment and 25 animals per experimental unit. The following factors were determined: White blood cell count, differential complete blood count, hemoglobin, heterophils/lymphocytes relation, hematocrit, intake, weight gain, feed conversion and mortality. The production line factor did not have any effect over the variables that were evaluated (p>0,05). There was a meaningful difference (p