Progesterone concentrations measured by radioimmunoassay in blood plasma and in fat-free milk of Gir breed cows iBos indicus). Determinations during oestrus cycle. Early pregnancy diagnosis.

Abstract

Progesterone concentrations were measured by radioimmunoassay in 137 fat-free milk and in 138 blood plasma samples obtained three times weekly during 17 estrous cycles from 12 zebu Gir cows, raised in range conditions at the "Centro Intraunidade de Zootecnia e Indústrias Pecuárias Fernando Costa", Pirassununga, State of São Paulo, Brazil. Profiles of progesterone concentrations for early pregnancy diagnosis were also examined on samples taken 23 days after natural service. Correlations were found between frozen and cooled milk samples (r = 0.92), as well as
between milk and blood plasma progesterone levels (r = 0.63). Variations during estrous cycle were detected, with lower values in folicular phase (less than 1.49 nmol/l in plasma and 2.61 nmol/l in milk) and peak values in luteal phase (from 15.60 to 21.30 nmol/l in plasma and 5.91 to 11.37 nmol/l in milk). All pregnancy and non pregnancy diagnosis were confirmed by rectal palpation, when 9.54 nmol/l in plasma and 3.18 nmol/l in milk discriminations values were utilized. From the combined data of 24 oestrus observations and progesterone profiles (29 oestrus) it was found that 17.2% of failure occured in oestrus detection.