<div>Background: The indiscriminate crossbreeding is the major cause for losses as well as for risk to existing breeds. Kangayam, a pride indigenous cattle breed of Tamil Nadu, also badly affected due to this unplanned indiscriminate breeding. Urgent and immediate action is required to protect this traditional breed. Estrus synchronization would be a best tool to improve the fertility rate and increase the population of this breed under field condition.&nbsp; 
 
Methods: Fifty Kangayam cows selected at farmer&rsquo;s field were divided into Group I, II, III, IV (Treatment groups) and Group V (Control group). Estrus synchronization with single PGF2&alpha;, double PGF2&alpha;, CIDR+PGF2&alpha; and ovsynch protocols were used in Group I, II, III and IV cows, respectively and inseminated during induced estrus. Group V cows were inseminated during observed estrus. The pattern of estrus, fertility rate and serum hormonal profiles on different days of treatment were studied.&nbsp;&nbsp; 
 
Result: The conception rates were higher in double PGF2&alpha; (80 per cent) and ovsynch protocol (80%) followed by CIDR+ PGF2&alpha; (70%). The progesterone (ng/ml) concentration was significantly (P&le;0.05) higher during estrus induction with PGF2&alpha; in treatment groups than during selection and insemination. The serum estradiol-17&beta; concentration was significantly (P&le;0.05) higher during insemination (24.21&plusmn;1.74 to 25.57&plusmn;0.80 pg/ml) than during PGF2&alpha; injection (12.81&plusmn;0.25 to 13.68&plusmn;0.30 pg/ml). The study concluded that higher conception rate in indigenous Kangayam cows can be obtained with synchronization using Double PGF2&alpha; and Ovsynch protocol followed by CIDR+PGF2&alpha; protocol.</div>

Comparative Study on Effect of Different Estrus Synchronization Protocols on the Pattern of Estrus, Conception Rate and Serum Hormonal Profile in Indigenous Kangayam Cows