Luteolysis, progesterone, and pregnancy per insemination after modifying the standard 7-day Ovsynch program in Holstein-Friesian and Holstein cows.

Two experiments were conducted with Holstein-Friesian cows in the Republic of North Macedonia and with Holstein cows in Kansas. We hypothesized that 1 dose of PGF2α administered on d 8 (Ov-8×1) instead of d 7 (Ov-7×1) in an Ovsynch program [GnRH-1 (d 0)-7 d-PGF2α-56 h-GnRH-2-16 h-timed artificial insemination (AI)] would increase the proportion of cows with complete luteolysis compared with controls receiving a single dose on d 7. Cows were treated with Ov-7×1 or with Ov-8×1 in experiment 1 (n = 347), using only a single dose of PGF2α. In experiment 2 (n = 452), a third treatment was added (Ov-7×2), in which a second dose of PGF2α was administered on d 8. Progesterone was measured in blood samples collected before the first or only PGF2α administration and 72 h later before insemination. Complete luteolysis was defined as having occurred when progesterone was ≥1 ng/mL before PGF2α and ≤0.3 ng/mL 72 h later (time of AI). Follicles and luteal structures were mapped before GnRH-1 and PGF2α administrations. The results of experiment 1 demonstrated a greater percentage of multiparous cows in OV-8×1 having complete luteal regression compared with multiparous Ov-7×1 cows, whereas treatments were equally effective in primiparous cows, as reflected in the concentrations of progesterone before AI. Furthermore, pregnancy per AI did not differ between treatments. Results in experiment 2 revealed that 99.3% of cows in the Ov-7×2 treatment receiving the second dose of PGF2α had complete luteolysis, regardless of parity, compared with significantly fewer cows in the Ov-7×1 and Ov-8×1 treatments (91.2 and 90.6%, respectively). Neither concentrations of progesterone, which averaged <0.4 ng/mL at AI, nor pregnancy per AI differed among the 3 treatments. In both experiments, when status of luteal function before PGF2α treatment was examined [cows with no corpus luteum (CL) before GnRH-1 but which had formed a new CL in response to ovulation after GnRH-1; cows with an older CL (the same CL that was detected before GnRH-1); or cows with both a new and an older CL], treatments did not differ in causing complete luteolysis. Furthermore, complete luteolysis in experiment 2 did not differ regardless of whether cows had 1, 2, or 3 or more CL before PGF2α administration. Pregnancy per AI did not differ among treatments, indicating that any of the 3 treatments might produce similar pregnancy outcomes with the flexibility of applying either of the 7- or the 8-d treatments.

Lack of mitochondrial DNA structure in Balkan donkey is consistent with a quick spread of the species after domestication.

A total of 132 mtDNA sequences from 10 Balkan donkey populations were analysed to ascertain their regional genetic structure and to contribute to the knowledge of the spreading of the species after domestication. The Balkan donkey sequences were compared with those from 40 Burkina Faso donkeys as an African outgroup to account for possible local Balkan scenarios. The 172 sequences gave 62 different haplotypes (55 in Balkan donkey). Virtually all the analysed populations had haplotypes assigned to either Clade 1 or Clade 2 even though the relative proportion of Clade 1 or 2 haplotypes differed across populations. Geographical maps constructed using factors computed via principal component analysis showed that the Balkan donkey populations are not spatially structured. AMOVA confirmed a lack of genetic structure in Balkan donkey mtDNA. Balkan populations were poorly differentiated (ΦST  = 0.071). Differentiation between the Balkan donkey and the African outgroup also was low. The lack of correspondence between geographical areas and maternal genetic structure is consistent with the hypothesis suggesting a very quick spread of the species after domestication. The current research illustrates the difficulties to trace routes of expansion in donkey, as the species has no geographical structure.

Pathways of the dominant follicle after exposure to sub-luteal circulating progesterone concentrations are different in lactating dairy cows versus non-lactating heifers.

With the increased use of different synchronization programs in cattle, attention is given to the progesterone concentration during development of the ovulatory follicle. It has been shown that low peripheral progesterone concentrations during follicular development may lead to decreased fertility. To investigate the effect of low progesterone concentrations on the fate of the dominant follicle, a study was conducted where cycles of dairy cows and heifers were manipulated to induce the development of the first dominant follicle without progesterone (PLACEBO) or under sub-luteal progesterone concentrations from a progesterone releasing intravaginal device (PRID Delta(®)). After insertion of the devices, daily follow up was performed by transrectal ultrasonography to identify and measure follicular development and blood samples were taken to determine the circulating progesterone concentration. Follow up was continued until the ovulation of a follicle occurred. After ovulation, the fate of the first dominant follicle was identified as arrested, atretic or ovulatory. Arrest was defined as persistence of the dominant follicle followed by ovulation whereas atresia was defined as regression of the dominant follicle and subsequent growth and ovulation of a new follicle. During PLACEBO treatment, heifers ovulated earlier and smaller follicles in comparison to cows. During PRID Delta(®) treatment, heifers had greater progesterone concentrations compared to cows and arrest of the dominant follicle occurred more in cows in comparison to heifers. In cycles where the dominant follicle was arrested, the ovulatory follicle was larger in comparison to cycles where the dominant follicle was atretic.