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A 2-yr experiment was conducted to determine whether isolation of ewes from rams is necessary to achieve a high response to the ram effect and whether ewes respond as well in May as in June. The experiment was conducted at two locations, with the same four treatments at each location. The four treatments differed with respect to ewe proximity to rams before mating (isolated vs adjacent) and date of joining with novel breeding rams (May 15 vs June 15). The proximity treatment at one location was changed in the 2nd yr; teaser rams were joined with the ewes instead of being adjacent to them. Overall, 86% of the eligible ewes were judged to have responded to the ram effect. A period of isolation before mating did not increase response compared with ewes that remained adjacent to, or in contact with, rams (86 vs 85%). Response was greater (P less than .05) in June and in the 2nd yr (P = .05). A physiological response, different from that generally described, was identified. Ewes ovulated approximately 8 d (8.0 +/- .19 d) after joining with breeding rams. The subsequent ovulation, accompanied by estrus, occurred approximately 15 d later (15.3 +/- .29 d). Eighty-five percent (87/102) of the ewes sampled responded in this manner. However, 82% (31/38) of a sample of these ewes had at least one morphologically normal corpus luteum when examined by laparoscopy 4 d after joining. It seems that these corpora lutea were not completely functional with respect to progesterone production. The ram effect can be achieved without prior isolation of ewes from rams.(ABSTRACT TRUNCATED AT 250 WORDS)

Whole blood is a common source of DNA, especially for genotype diagnostic services. Many laboratories now receive blood samples by mail and/or store blood samples prior to DNA extraction. Therefore, the effects of storage time (number of days from blood collection to DNA extraction) and temperature on DNA yield and quality are important. We compared DNA yield and quality from bovine blood samples exposed to one of sixteen treatment combinations of storage time (3, 7, 14 or 28 days) and temperature (-20 degrees, 4 degrees, 23 degrees or 37 degrees C) to the results obtained when DNA was extracted within 4 h of collection. The highest mean DNA yields, relative to the control samples, were obtained from blood stored at 4 degrees C. Blood stored at 37 degrees C foror = 3 days or 23 degrees C foror = 7 days yielded less (P.05) DNA, compared with blood stored at 4 degrees or -20 degrees C for up to 28 days. DNA was not recovered from three of the samples stored at 23 degrees C and five of the samples stored at 37 degrees C. The genomic DNA obtained was of high molecular weight and suitable for restriction enzyme digestion and PCR amplification, regardless of the treatment.