Frequency and duration of estrous cycle and period in genetically non-descript (SRD) type of goats in the tropical northeast of Brazil

Abstract

In a one-year study conducted in the tropical, semi-and region of Northeast of Brazil, 30 genetically non-descript (SRD) does, 1.5 - 2.0year old, were grazed on native range (2.3 ha/head/year) with ad libitum water, salt and bone meal. Fourteen goats were supplemented with green chopped elephant grass (P. purpureum Schum.) at the proportion of 2% dry matter in relation to the mean body weight of goats, during the most critical part of the dry season (November 2 to February 26). The remaining 16 goats served as controls. The 480estrous cycles and 511 estrous period lengths were compared for the wet season (February 27 to July 10) and dry season (July 11 to February 26) as well as for level of feed. The incidence of estrus classified by month was evenly distributed throughout the year with a mean of 8.3% and 7% to 9.8% range (P>0.05) monthly variation. The average lengths of estrous periods were 55.8 vs 57.4 hours (P>0.05) and the estrous cycles 20.9 vs 21.5 days (P>0.05) for non-supplemented and supplemented groups, respectively. The same traits between wet and dry seasons were 62.0 vs 51.2 hours (P<0.05) and 20.6 vs 21.8 days (P<0.06), respectively.