**8. Conclusions**

These studies covering the physiological mechanisms regulating ovarian follicular development through multiple births displayed us the reproductive traits are highly complex traits that involve a potential genetic background and significant contributions of various environmental factors. Several studies report that causative mutations in TGF-β pathway-related genes, including BMP15, BMPR1B, and GDF9, strongly affect the ovulation rates in prolific small ruminants, which tend to conceive and maintain multiple ovulation spontaneously. Even if the bovine is naturally low-ovulating mammals, some variations may still be observed in the ovulation rates, despite the low heritability; thus, there is a potential to make genetic progress through selection against reproductive traits by using multiple observations of ovulation rate as the indirect selection criterion in cattle. Recent fine-mapping studies that narrow the genomic region truly, influencing multiple ovulation, especially on BTA5, 10, 11, 14, and 24, give positive signals that causative mutation controlling high ovulation may be identified shortly.

The complete understanding of the complex process of follicular growth during the estrus cycle and the development of oocytes will undoubtedly improve the knowledge to maximize and control the efficiency of reproduction in livestock species, especially the existence of twin or triplet births since the fertilization of more than one oocyte after ovulation will be the main reason for multiple births. On the other hand, it should not be ignored that many factors, including genetic but primarily environmental sources, specifically breed differences, age and parity of dams, the season of calving, and the effect of feeding and management systems significantly affect ovulation and twinning rates importantly in especially cattle production systems. Therefore, the production of twin calves might be more profitable for the breeder by implementing appropriate management and feeding programs to cope with the reproductive problems faced by twin-bearing cows.

In conclusion, understanding the genetic background of high fertility in mammals, on the one hand, is extremely important for the designing of convenient genetic improvement and management programs in livestock; on the other hand, it provides the basic knowledge necessary to overcome fertility problems in humans by using the cow as the ideal model organism.

*The Incidence of Ovulation and Detection of Genes Associated with Ovulation and Twinning… DOI: http://dx.doi.org/10.5772/intechopen.99936*
