In this study, we demonstrate the production of transgenic goats by nuclear transfer of fetal somatic cells. Donor karyoplasts were obtained from a primary fetal somatic cell line derived from a 40-day transgenic female fetus produced by artificial insemination of a nontransgenic adult female with semen from a transgenic male. Live offspring were produced with two nuclear transfer procedures. In one protocol, oocytes at the arrested metaphase II stage were enucleated, electrofused with donor somatic cells, and simultaneously activated. In the second protocol, activated in vivo oocytes were enucleated at the telophase II stage, electrofused with donor somatic cells, and simultaneously activated a second time to induce genome reactivation. Three healthy identical female offspring were born. Genotypic analyses confirmed that all cloned offspring were derived from the donor cell line. Analysis of the milk of one of the transgenic cloned animals showed high-level production of human antithrombin III, similar to the parental transgenic line.

After luteolysis, subluteal concentrations of progesterone or treatment with a synthetic progestagen result in an extended period of dominance (persistence) of the dominant follicle in cattle. Two experiments studied (1) the relationship between the duration of dominance of the ovulatory follicle and pregnancy rate and (2) the ability of a persistent dominant follicle to ovulate and form a normal functioning corpus luteum. In Expt 1, beef heifers were either untreated (n = 30) or given a synthetic progestagen implant (3 mg norgestomet) for 12 days starting on day 16 of their cycle (n = 32). The mean duration of dominance of the ovulatory follicle differed (P < 0.05) between treated and control heifers (10.8 +/- 1.2 and 3.3 +/- 0.8 days, respectively) and 20 of 26 control and 7 of 30 treated heifers were diagnosed pregnant 28 days after artificial insemination (P < 0.01). In Expt 2, on the first day of dominance of the second dominant follicle, heifers received either a PGF2 alpha analogue alone (controls; n = 18), or prostaglandin and a norgestomet implant for 6 (T6; n = 19) or 10 days (T10; n = 20). Increases in the duration of dominance of the second dominant follicle (controls, 4.1 +/- 0.2 days; T6, 8.6 +/- 0.2 days; T10, 12.1 +/- 0.2 days; P < 0.05) resulted in a decrease in pregnancy rate (controls, 14 of 16; T6, 11 of 19; T10, 0 of 13; P < or = 0.05). Progesterone concentrations on days 7 and 12 and the area of luteal tissue on day 12 after artificial insemination were not different (P > 0.05) between treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

There is a low incidence of ovulation of the first dominant follicle that develops in the early postpartum period of beef suckler cows, which prolongs the interval from calving to first ovulation. The objective of this study was to determine whether a single injection of a GnRH analogue would ovulate the first postpartum dominant follicle. Limousin x Friesian beef suckler cows were assigned at parturition, over two years (16 cows in year 1; 19 cows in year 2), to one of three treatments: (1) untreated (control; n = 12), (2) GnRH analogue (20 micrograms buserelin i.m.) administered in the growing-plateau phase of the first postpartum dominant follicle (GnRH-G; n = 12) and (3) GnRH analogue administered in the declining phase of the first postpartum dominant follicle (GnRH-D; n = 11). From day 8 or 9 post partum, the ovaries of each cow were examined daily by ultrasound to determine the time of GnRH injection and ovulation. Blood samples were collected daily for progesterone measurement to confirm ovulation and in year 2 to determine the duration of the first oestrous cycle. The mean (+/- SEM) number of days from parturition to development of the first dominant follicle was 11.0 +/- 0.3, 10.3 +/- 0.5 and 10.1 +/- 0.7 for cows assigned to treatments 1-3, respectively (P > 0.05). The proportion of cows ovulating the first dominant follicle was higher (P < 0.05) following GnRH treatment (12 of 12 and 7 of 10; GnRH-G and GnRH-D, respectively) than with controls (2 of 12).(ABSTRACT TRUNCATED AT 250 WORDS)

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