An average of 31 cryobank bulls was sampled per replicate, 58% being sampled because of outstanding EBVB (see Table 2).
Compared to the case in which all young bulls are sampled for cryopreservation (which corresponds more or less to the current procedure in the Netherlands), the results were basically the same.
In the Netherlands, most of the tested bulls are sampled for preservation in the gene bank [ 8], while in the USA, the selection of animals for cryopreservation is aimed at optimizing genetic diversity within the collection, by sampling animals from clusters determined through computed genealogical relationships [ 9].
Bull TBV were sampled from a normal distribution with a mean of $300+1.5.5 genetic SD of NM$) and a SD of $200.
All the postpubertal bulls, postpubertal heifers, breeding bulls and cows were sampled in each selected herd.
All post-pubertal bulls present in selected herds were sampled once for both C. fetus and T. foetus by collecting preputial samples using preputial scraping technique as follows: The prepuce was cleaned with paper towel and the hair around the preputial orifice clipped where necessary.
Genotypes for 287 bulls and 10,000 diallelic sites were sampled based on the following procedure: First, the allele frequency p of the first allele at a SNP was drawn from a uniform distribution, the allele frequency for the second allele q at this SNP is then given by q = 1-p.
A total of 250 herds containing 602 bulls, with between 1 and 24 bulls per herd (median: 1; interquartile range: 1, 2) were sampled, with 78 herds containing at least one bull positive for C. fetus, giving a herd-level prevalence, adjusted for sampling weights, of 25.5% (95% CI: 19.4-32.7).
Our results also indicate that cryobank bulls that have been sampled for functional traits with high EBV will tend to be used more frequently than other cryobank bulls, independently of the aim.
