UUDISED

GOOD PROJECT EXAMPLE: Development of New Technologies for Bull Sperm Sex Selection and Fertility Management

The problem to be solved

Historically, dairy cattle production together with milk production has been, and will evidently be, the most important area of agricultural production in Estonia. The increasing demand for milk and milk products has significantly advanced Estonian dairy cattle production over the last twenty years. In addition to milk, pedigree animals have become an important export article.

The project had two main objectives:

1. to develop a novel sex selection technology for bull sperm to be used in insemination resulting in the birth of calves of the desired sex and
2. to develop a bull fertility test and an artificial supplement that enables early detection of animals with poor sperm quality in the hopes of increasing the sperm doses from bulls with low fertility sperm but with a high breeding value.

“The results of the bull sperm fertility identification markers are vital in terms of breeding and according to the Animal Breeders´ Association of Estonia, the results have perspective for further research.” Triin Hallap, the project leader

Project outcomes

It was concluded that TGM1-marker was not sufficiently effective for the development of a sex-selection technology due to large biological variation among bulls. A cheaper alternative to the hightech bovine sperm sex selection method was developed. The colloid centrifugation method shifted the sperm sex ratio to X-chromosome-bearing sperm. However, it was not economically efficient. Data on high and low fertility bulls were compared to identify sperm fertility markers.

As a result of the sperm transcriptome analysis, 32 genes were identified which showed a four-fold or higher expression difference between the two groups of bulls. Validation confirmed that the expression of two genes was related to bull sperm quality. The results are promising and there is an important prospect in terms of cattle breeding. The mRNA expression matrix of high fertility (highFert) and low fertility (lowFert) bull sperm is based on 32 genes, whereas the expression difference between the groups is four-fold and the nominal p-value <0,05.

Additionally, two original methods were developed, which can be used for: a) simultaneous analysis of the occurrence rate of Y and X chromosomes in the sperm sample; b) simultaneous detection of immune response of antibodies and the presence of X-chromosome in the sperm sample. These methods are important in terms of the quality control of sexed semen.