Development of a subjective scoring system for evaluating corpus luteum function in beef cattle

Abstract

The objective of this project was to develop a scoring system to evaluate blood flow through the corpora lutea and circulating progesterone concentrations in heifers and cows through the progression of a normal, nonmanipulated estrous cycle. Sixteen, non-lactating, beef females were subjected to reproductive tract ultrasound scans every other day for the duration of an entire normal bovine estrous cycle (22 days). Ovarian structures (follicles and corpora lutea) were identified and measured. Color Doppler mode was used to visualize blood perfusion through luteal tissue and was given a subjective score based on percent of the corpus luteum that showed color (0, no color; 1, small color at periphery; 2, up to 80% color; 3, >80% color). Venous blood samples were collected at the time of ultrasound examination, and serum progesterone values were used to confirm corpus luteum function. The area of the corpus luteum was correlated with serum progesterone concentrations (P <0.0001, r=0.45). Doppler score was strongly correlated with serum progesterone concentrations (P < 0.0001, r=0.62) and area of the corpus luteum (adjusted for lacunas) (P <0.0001, r=0.48). Peak serum progesterone concentrations were not correlated with age (P=0.74), weight (P=0.80), or BCS (P=0.13). There was a tendency for peak progesterone concentration to be correlated with the area of the corpus luteum (P=0.07, r=0.46). Doppler score was not correlated (P = 0.59) with ultrasonographer. In summary, Doppler scores can be utilized as an estimation of corpus luteum function, irrespective of scanning technician, and may be a more reliable measure than by corpus luteum area determination, alone.