Use of the male effect to induce reproductive activity in ovine intensive breeding systems

Abstract

THE PRESENCE OF THE MALE EFFECT AND ITS IMPORTANCE IN THE REPRODUCTIVE MANAGEMENT OF COLUMBIA EWES WAS EVALUATED DURING A COMPARATIVE STUDY BETWEEN A HERD OF EWES SUBJECTED TO AN ANNUAL BREEDING SYSTEM WITH SERVICES IN NOVEMBER (AS) AND ANOTHER HERD SUBJECTED TO AN INTENSIVE SYSTEM WITH BREEDING PERIODS IN NOVEMBER, JULY AND MARCH (IS). THE TWO HERDS WERE KEPT ON INTENSIVE IRRIGATED PRAIRIES WITH MODERATE CLIMATE: THE EWES IN THE IS WERE SUPPLEMENTED DURING THE LACTATION AND REBREEDING PERIODS. ESTRUS EXPRESSION WAS DETECTED BY THE PRESENCE OF MARKS ON THE RUMP LEFT BY ANILINE-IMPREGNATED TEASER MALES. IN ADDITION, THE CONCENTRATIONS OF PROGESTERONE WERE DETERMINED IN BLOOD SAMPLES FROM 20 ADULT EWES AND 5 EWE-LAMBS FROM EACH BREEDING SYSTEM. THESE SAMPLES WERE TAKEN TWICE PER WEEK FROM THE TIME THE TEASER MALES WERE INTRODUCED. THE CONCEPTION DATE FOR EACH EWE WAS RETROSPECTIVELY CALCULATED FROM THE DATE OF LAMBING. THE RESULTS INDICATE A CLEAR MALE EFFECT IN THE IS GROUP DURING THE BREEDING PERIODS OF JULY AND MARCH, WHEN SUCH A MALE EFFECT PROVED TO BE VERY IMPORTANT FOR THE REPRODUCTIVE SUCCESS OF THE HERD. IN CONTRAST, THE MALE EFFECT WAS NOT APPARENT DURING NOVEMBER BREEDING PERIODS BECAUSE THE ANIMALS OF BOTH HERDS WERE ALREADY CYCLING WHEN THE TEASER MALES WERE INTRODUCED AT THAT TIME OF THE YEAR. IT IS CONCLUDED THAT THE USE OF THE MALE EFFECT CAN IMPROVE THE REPRODUCTIVE EFFICIENCY OF COLUMBIA EWES EXPOSED TO INTENSIVE BREEDING SYSTEMS IN MEXICO.