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A cannulation technique was developed to collect blood samples from the ovarian vein of mares over an extended period. Ovarian venous cannulae placed in 4 mares remained patent for a mean (± sem) duration of 36.8 (± 6.2) days. During mid-diestrus, concentrations of progesterone in the ovarian vein ipsilateral to the corpus luteum (1,663.8 ± 238.8 ng/ml) were significantly (P < 0.001) higher than concentrations measured in paired samples from the jugular vein (6.1 ± 0.3 ng/ml). Concentration of estradiol in the ovarian vein ranged from a mean of 1,053.2 ± 303.1 pg/ml during diestrus to 3,353.8 ± 1,052.8 pg/ml during estrus, whereas values for 74% of samples collected concurrently from the jugular vein were near or below the sensitivity of the assay (10 pg/ml).

Results of the study indicate that patent long-term ovarian vein cannulation can be achieved in mares. The cannulation technique provides access to important fundamental information on equine reproductive endocrinology, which to our knowledge, has not been available.

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in American Journal of Veterinary Research


To determine concentrations of estrone sulfate in serum, estrone sulfate in urine, relaxin in serum, and progesterone in serum in pregnant llamas and alpacas and to assess the potential of these hormones as pregnancy indicators.


Prospective study.


19 parous pregnant camelids (8 llamas and 11 alpacas).


Estrone sulfate concentrations (in serum and in urine) and progesterone concentrations (in serum) were determined by enzyme immunoassay. Relaxin concentrations (in serum) were measured by radioimmunoassay. Serum and urine samples were collected daily for the first 30 days after breeding and, thereafter, once weekly until parturition.


Estrone sulfate concentrations (in serum and in urine) peaked twice during pregnancy. The first took place 21 days after breeding and the second during the last month of pregnancy. Relaxin concentrations increased at 3 months of gestation to > 20 ng/ml, decreased at 5 months to 5 ng/ml, then increased from 8 months of pregnancy until parturition. Progesterone concentrations were detectable 4 days after breeding and were maintained > 2 ng/ml throughout pregnancy.

Clinical Implications

The first increase in estrone sulfate concentration over basal values may indicate early interaction between mother and embryo, whereas the second increase may reflect fetal viability. Use of estrone sulfate concentration to diagnose pregnancy in llamas and alpacas is highly dependent on time of sampling. Relaxin concentration in serum is a superior indicator of pregnancy after the second month in the llama and alpaca because its existence is suggestive of interaction between mother and fetus, and concentrations are greater than basal values for a long period of pregnancy. Progesterone is not a direct product of the embryo or fetus and only indirectly confirms a diagnosis of pregnancy. (J Am Vet Med Assoc 1996;208:2027-2030)

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in Journal of the American Veterinary Medical Association