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U. S. Department of Agriculture, Beltsville, MD 20705
Abstract
Studies were conducted with a total of 280 ewes to determine the accuracy of pregnancy diagnosis by use of an ultrasonic scanner. The scanner, previously developed to measure back fat and loin eye areas in swine, employs ultrasonic waves to generate a two-dimensional image of an interior cross section of an animal and a camera to photograph the image. The photographic image obtained when the transducer (the transmitter and receiver of the ultrasomic waves) moved over an area of an animal body was designated as a scan and the process as scanning. The study consisted of three phases: detection of pregnancy by use of scans at various locations on the abdomen in relation to fetal age; assessment of accuracy of detection of single and multiple fetuses by use cf a single scan; and evaluation of a composite scanning technique for detection of fetal numbers. Forty-three ewes were used in the first phase, 100 in the second and 137 in the third. Pregnancy diagnosis could be determined with an accuracy of 100% in ewes during the last half of gestation by making a single scan on the abdomen just anterior to the udder; scans which were made near the navel detected pregnancy with less accuracy. Accuracy of detection of ewes carrying single and multiple fetuses was 67% when a single scan was made midway between the navel and udder at 28 to 52 days before lambing. Accuracy of detection of single and multiple fetuses was increased to 84% when a composite scanning technique was used involving both the right and left sides as well as the lower abdomen. The time of feeding before scanning did not affect the accuracy of detection of fetal numbers.
1 Ruminant Nutrition Laboratory, Nutrition Institute, A.R.S., U.S.D.A., Beltsville, MD.
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