Assessing the breeding efficiency of broiler breeder flocks by measuring sperm transfer into laid eggs.

1. The breeding efficiency of broiler flocks was assessed by estimating the numbers of spermatozoa trapped in a 5.5 mm2 area of the perivitelline layer of laid eggs. 2. In samples of approximately 60 eggs taken from flocks on the same day, the numbers of spermatozoa ranged from 0 to several hundred. 3. Within each sample of eggs, there appeared to be two distinct populations: eggs in which perivitelline spermatozoa could not be found; and eggs containing spermatozoa for which the logarithm of the number of perivitelline spermatozoa can be approximated by a normal distribution. 4. When data from 15 flocks were considered, the overall flock fertility was linearly correlated with: the median of the number of spermatozoa per 5.5 mm2 of perivitelline layer (r = 0.678); the mean of positive values of the logarithm of the number of spermatozoa (r = 0.620); and the proportion of sampled eggs in which the number of perivitelline spermatozoa was greater than 0 (r = 0.714). 5. Flock age was the major factor influencing fertility and all the variables of perivitelline sperm distribution.