Abstract: 49

LUTEINIZING HORMONE LEVELS IN ANESTROUS SUCKLED COWS WITH AND WITHOUT DOMINANT FOLLICLE.

ZT Ruiz-Cortés¹ , LM Greiffestein² , J Gallego³ , M Olivera-Angel¹
Biogénesis, Facultad de Medicina Veterinaria y Zootecnia, Universidad de Antioquia, Colombia ¹
Clinica de la Americas, Medellin, Antioquia , Colombia ²
Centro de Investigacion El Nus, Antioquia, Colombia ³

In a previous study we found that follicles >than 4 mm in diameter were present after 20 days pp. and up in grazing suckled Zebu cows (Ruiz-Cortés and Olivera-Angel) and regular patterns of growth and regression of large follicles (10-12 mm) were evident most of the time, but that so-called dominant follicles apparently did not have the capacity to ovulate. The main purpose of this research was to determine the levels, amplitude, frequency, mean and basal concentration of LH pulses in the presence or absence of a dominant follicle in grazing sukled Zebu cows. The experiment was conducted in Bos indicus nursing cows (n=9), 5 with dominant follicle and 4 without, between the third and the 10th month after calving. The first day of dominance of the presumptive ovulatory follicle was defined ecographically as the first day that dominant follicles have an increased growth rate compared to subordinate follicles which slow down. The second day of dominance, blood samples were collected every 15 minutes during 8 hours and LH plasma concentration was determined using EIA (Sanofi Santé Animale). Characteristics of the pulsatility of LH were determined using the Pulsar program. The mean LH concentrations was 0.156 ng/ml for the controls and 0.165 ng/ml for the cows with a DF; the basal level was 0.124 ng/ml and 0.155 ng/ml, the frequency of the pulses/h were 0.54 and 0.33 and the amplitude was 0.122 ng/ml and 0.02 ng/ml respectively. Using Student's test to compare them, indicate no significant differences between control and DF cows. However, such low levels of LH and the low-frequency LH pulses could explain the incapacity of the DF to lead to ovulation.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.