DIETARY SELF-SELECTION OF LAYING HENS INADEQUATE TO OVERCOME THE EFFECTS OF HIGH ENVIRONMENTAL-TEMPERATURE

Two environmental temperatures, 21.degree. and 30.degree. C, were used during a 28 day experimental period. There were 2 groups of hens in each temperature treatment. The control groups (C) were given a conventional balanced diet and each dietary self-selection group (S-S) was provided on an individual hen basis 3 diets. each one being high in energy, protein or Ca. The S-S groups had significantly reduced egg production, which probably resulted from the significantly reduced protein intake. Egg weight and energy intake were reduced in the S-S group at 21.degree. C; Ca intake and egg shell strength at 30.degree. C were higher as compared to the corresponding C group. Dietary self-selection did not enable hens to regulate nutrient intake for comparable performance to hens provided 1 balanced diet. Also, the detrimental effects of high environmental temperature were not overcome by dietary self-selection.