The purpose of this thesis was to study the fertility of broiler breeders and the factors that affect it. Fertility is one of the most important features of broiler breeders in order to produce hatching eggs for the production of broiler chickens. Fertility refers to the ability of broiler breeders to produce fertilized eggs for hatching.

The challenge in feeding broiler breeders is to provide them with enough energy without gaining weight. During the final laying period it is important to take care of sufficient energy intake for hens as well as for roosters in order to maintain fertility. Overfeeding or too low energy intake weakens the fertility of the flock. Obesity in roosters is also negatively related to mating activity. Overfeeding or too low feed intake leads to a decrease in semen production.

A questionnaire was prepared for broiler producers regarding their previous breeding flock and the factors affecting the fertility of broiler breeders in general. Regarding these flocks, monitoring data on flock fertility and rooster weight development were also made available.

Based on the results, flock uniformity was considered an important characteristic in terms of starting egg production and fertility. It seems that underweight in roosters may have a minor effect on the fertility of the flock during the late period of egg laying. According to the producers who responded to the questionnaire, there is a lot of variation between the flocks in the uniformity and especially in the uniformity of the roosters. The foot health of roosters came up in the questionnaire survey results. Rooster’s good foot health is a precondition for successful mating.