Expression of several traits of fertility in young and old dwarf broiler breeder hens inseminated with duplicate doses of semen.

One hundred sixty-two dwarf broiler breeder females were each inseminated at 4-wk intervals with either 30, 60, or 120 million spermatozoa repeated on 2 consecutive days. The experiment was conducted at two age periods, i.e., 32 to 41 wk (Period I) and 55 to 63 wk (Period II). Females during Period II had a significantly shorter duration of fertility than during Period I (P less than .0001). Also, the mean duration of fertility but not maximum percent fertility was improved in females inseminated with the highest doses compared with the lower doses of spermatozoa. Individual fertility results confirmed that a large majority of the females (81 to 93% during Period I and 62 to 76% during Period II) are capable of laying 100% fertile eggs for at least 7 days. The mean duration of fertility during Period II was longer in females primarily classified as having the longest duration of fertility in Period I. This confirms that duration of fertility is consistent during the reproductive life.