**2.3 Biostimulation in bovines**

Biostimulation (bull effect) a stimulatory effect of male upon female reproductive parameters, due to pheromones, result in the induction of oestrus and ovulation through genital stimulation, and therefore, has got potential in improving reproductive efficiency in livestock including bovines. It has been observed that significant proportion of heifers exposed to bull urine attained early puberty against the proportion of heifers not exposed, suggesting presence of priming pheromone in the bull urine [28]. Similar observation of early puberty attainment due to social interactions between bulls and prepubertal heifers [29], and also due to exposure to vasectomized bulls at significantly lower age of 23.1 months, as against 26.4 months in non-exposed heifers has been made [30]. In multiparous cows duration of post-partum anestrous was decreased when exposed to bulls [12], and interval to estrus was shorter in exposed cows [31]. Exposure to the androstenone a boar sex pheromone, was found having positive effect on reproductive parameters such as earlier onset of cyclicity at puberty and better results from artificial insemination in cows [32]. In a bioassay a mixture of compounds consisting of acetic acid, 1-iodo undecane and propionic acid from estrus cows were smeared on the genitalia of non-estrous cows, thereafter bulls were allowed to sniff the cows for 30 min, and it was observed that bulls displayed significantly longer flehmen behavior and increased number of mounts than the individual compounds and control, indicating the possible role of these chemicals in the induction of mating behavior [21]. Also various volatile compounds from bovine estrous urine (6-amino undecane, 2-butanone, coumarin, 1,2-dichloroethylene, 9-octadecenoic acid and squalene), resulted in improved reproductive function of a exposed bull in terms of enhanced libido and semen production [24]. Several mechanisms of biostimulation have been postulated such as, pre-estrus progesterone rise associated with bull exposure in

*Chemical Signaling in Bovines: Understanding the Behavior and Way of Communication DOI: http://dx.doi.org/10.5772/intechopen.99834*

postpartum cows, resumption of cyclicity due to luteinizing hormone (LH) release following exposure resulting in positive feedback for LH release in the hypothalamus to estrogen (overriding inhibitory effects of low concentration of estrogen on the hypothalamus), and increased sensitivity of the ovary to LH by increasing the number of LH receptors [13, 31].
