Reproductive deficiency in bulls from synthetic breeds according to the type of crossbreed and the morphology of the Y chromosome

Abstract

We used 550 Braford and 214 Brangus-Ibagé bulls to study the association between Y chromosome morphology and the evaluation of breeding-soundness, karyotyping and breeding records were used to assess Y chromosome morphology. In general, no direct association was detected between the individual type of Y chromosome and reproductive fitness as previously estimated through breeding soundness examination. The type of breeding strategy used to form the synthetic breeds was also analyzed. The Braford breed is about 3/8 Zebu (Bos taurus indicus) and 5/8 Hereford (Bos taurus taurus) but when the breeding strategy used 1/4 Zebu animals to produce Braford bulls which were 3/8 Zebu a greater percentage of the bulls had to be culled due to reproductive problems. Our study shows that certain interactions between genotypes can be detrimental to the reproductive efficiency of 3/8 Zebu animals and that breeding strategies avoiding or favoring certain genotypes can be used to reduce the percentage of bulls from synthetic breeds that are culled due to problems with semen quality.

Cellular and Molecular Insights Into the Etiology of Subfertility/Infertility in Crossbred Bulls (Bos taurus × Bos indicus): A Review

“…Several authors reported that almost 80-90% of purebred animals have no reproductive problems (Kennedy et al, 2002;Bjelland et al, 2011). In contrast, a greater proportion of bulls with reduced potential fertility was found in hybrids in comparison with their parental pure breeds (Horn et al, 2005). A synthetic breed (i.e., composite or hybrid or stabilizer) is a new breed or line from crossing two or more existing breeds, especially to increase hybrid vigor (Chacko, 2005).…”

“…At chromosome level, the Y-chromosome in Bos taurus is submetacentric while that in Bos indicus is acrocentric. Therefore, it was proposed that the lower fertility in zebu crosses with European cattle could be due to small deletions or position changes between the synapse region of the X and Y chromosomes, or to alterations in genes participating in the regulation of reproduction ( Horn et al, 2005 ). With the advancements in science and analytical techniques, nowadays, there is an increased interest in identification of male fertility markers.…”