Abstract
The dog has been a good companion animal to humans. Companionship, security, hunting, and herding are the best utilities for the owner. The amazing sense of smell of some of the breeds of dogs is taken advantage to train for accurately tracking and sniffing out criminals. The heralding and tracking efficiencies of the majestic Rajapalayam breed of dog are outstanding but little is documented about the reproductive status of females through volatile compounds to which the males respond appropriately to facilitate sexual attraction and mating of this breed. Therefore, the present study was carried out to investigate the reproductive behaviours and urinary volatiles at various stages of the estrous cycle. The repeated behaviors such as approach, attempted investigation, investigation, pre-mount contact, and mounting were significantly higher in male dogs exposed to females in estrus. By contrast, such reproductive behaviors were totally absent in males exposed to females in post-estrus. Pre-copulatory behaviors and urinary volatiles of female dogs were hypothesized to be the guiding/exhibitioner factors. As many as, 30 urinary volatile compounds were identified during the estrous cycle. Among these, 2-methyl-hexadecane, 3-methylene-4- methypentan-1-ol, (E)-9-methyl-7-undecenoic acid, 4,5-dimethyl-4-hexen-2-one, and 2-octyldodecan-1-ol were specific to estrus phase. Behavioral observation clearly revealed that stud males exhibited the highest attraction to females, with repeated attempts of investigation, actual investigation, mounting, and penile erection being significantly high toward estrus urine sample as well as mixture of synthetic estrus-specific volatile compounds. However, pro-estrus-specific 2, 3-dimethyl-1-butanol and postestrus-specific pentadecane did not evoke such sexual behaviors in male dogs. It is concluded that the female dog in estrus phase releases specific volatiles chemicals in the urine, which is instrumental in provoking the manifestations of premating behaviors in male dogs. Thus, the present study provides evidence that non-invasive methods such as assessment of behaviors and estrus-specific urinary volatiles would serve as good for detection of estrus in the Rajapalayam dog. Among the volatiles identified in estrus urine, based on the behavioral assay, urinary (E)-9-methyl-7-undecenoic acid proves to be the most effective male-attracting pheromone in the female dog. Thus, the present study provides evidence to the effect that assessment of male behaviors to estrus-specific urinary volatiles can facilitate detection of estrus in the Rajapalayam dog so as to precisely time the mating.