EFFECT OF STARTING BODY FAT CONTENT OF LEGHORN-TYPE LAYING HENS ON THE CHANGES IN THEIR BODY FAT CONTENT, EGG PRODUCTION AND EGG COMPOSITION DURING THE FIRST EGG LAYING PERIOD

The experiment was carried out with 60 TETRA BLANCA laying hens chosen from 250 TETRA BLANCA pullets based on their body fat content, predicted at 16 weeks of age by means of computer tomography (CT). Pullets with the highest (n=20), lowest (n=20) and average (n =20) body fat content were chosen for the investigation. Changes in the body fat content of the experimental animals were followed by means of computer tomography in vivo, scanning the hens at every fourth week of the experiment, between 20 and 72 weeks of age. Eggs produced by these birds, were collected at 32, 52 and 72 weeks of age and, after breaking them, their yolk, albumen and egg shell ratio was determined and their dry matter, crude protein and crude fat content was chemically analyzed. Based on the results it was established that the body fat content of the hens started the egg production with high body fat content being higher than that of the hens started the egg production with average or low body fat content during the whole experimental period. The differences in the body fat content of the two extreme groups were statistically proven between 24 and 48 weeks of age (P<0.05). The total egg production of the hens with high starting body fat content was lower by 11 and 12 eggs per hen on the average than that of the hens with low and average starting body fat content, respectively. The composition of the produced eggs was mainly not affected significantly (P>0.05) by the starting body fat content of the hens.