Materials and Methods
Genetic Stocks
The LSN line was obtained from the University of Connecticut in 1997 and was originally housed in the poultry research center at the OARDC. After determining that no egg-transmitted organisms were present (Y.M. Saif, Food Animal Health Research Program, OARDC, Wooster, OH 44691; personal communication), the line was moved to a separate house at the turkey research center at the OARDC.
The LSN line has been reproduced yearly since 1997 using a paired mating system (Nestor, 1977) with 36 pairs of parents. With this system, the pairs are mated at random, except that full-sib matings are avoided.
At 3 months of age, the exhaustion score of each bird was measured. The bird was placed on its back on a flat surface. Each time the bird righted itself without rolling over was counted as a positive result. The test was repeated for a maximum of 30 times. Only birds with an exhaustion score of 6 or less were used to reproduce the LSN line.
A sample of eggs was obtained from a specific pathogen free (SPF) White Leghorn line. The SPF White Leghorn line is currently being maintained by the Food Animal Health Research Program at the OARDC (Y.M. Saif; personal communication).
Management of Birds
The offspring were grown in floor pens until approximately 20 weeks of age after which they were housed in individual laying cages. During rearing, the birds were fed turkey rations (Naber and Touchburn, 1970) that exceeded the protein requirements of the birds and met or exceeded National Research Council (1994) requirements for other nutrients. After housing in laying cages, the birds were fed turkey breeder rations (Naber and Touchburn, 1970).
Matings Made
Matings were made by artificial inseminations. Multiple hatches were used to produce the desired number of offspring. Reciprocal F1 offspring were produced by crossing the LSN line and the SPF White Leghorns with each male being mated to one female. The number of paired matings was 10 in the LSN line male X SPF White Leghorn female cross and 12 in the SPF White Leghorn male X LSN line female cross. The number of offspring in the respective F1 crosses was 137 and 126. The F2 generation was produced within each F1 cross by random selection of individuals and use of paired matings. Nineteen pairs of parents were used to produce each F2 population. There were 300 and 346 offspring, respectively, in the F2 generation for the LSN line male X SPF White Leghorn female and SPF White Leghorn male X LSN line female crosses. Each F1 cross was backcrossed to the SPF White Leghorn line with three parental pairs being used for the F1 from the LSN line male X SPF White Leghorn female and six parental pairs for the other F1 cross. The number of offspring in the respective back crosses was 58 and 102.