Luteolysis in Bos indicus cows on Days 5 and 7 of estrous cycle with varying doses of PGF2α.

The aim of this study was to evaluate luteolysis using three doses of PGF2α on Day 5 or Day 7 of the estrous cycle in nonlactating Nellore (Bos indicus) cows. Cows (n = 323) were assigned within date of estrus (Day 0 of estrous cycle) to receive 12.5, 25.0, or 50.0 mg of PGF2α on either Day 5 or Day 7 of the estrous cycle in a 3 × 2 factorial arrangement. Blood samples for progesterone (P4) concentrations were collected at 0, 24, 48, and 72 hours after PGF2α to assess luteolysis (L). Luteolysis was defined on the basis of P4 concentrations at 72 hours using either less than 0.5 ng/mL (L0.5) or less than 1.0 ng/mL (L1.0) as the cut off. Luteolysis was considered "partial" when P4 concentration declined within 24 hours after PGF2α but failed to decline further or, in some cases, increased. Incidence of luteolysis was less (P < 0.01) on Day 5 than Day 7 of the estrous cycle (17.3 vs. 47.6% and 30.4 vs. 77.2%; for L0.5 and L1.0, respectively). Dose of PGF2α increased (P < 0.01) L1.0 (12.5 mg = 38.9%; 25.0 mg = 52.3%; and 50.0 mg = 70.4%). Incidence of partial luteolysis for cows on Day 5 (57.1%) was greater (P < 0.01) than that on Day 7 (19.1%) of the estrous cycle and was more prevalent (P < 0.01) with lower doses of PGF2α (12.5 mg = 49.1%; 25.0 mg = 37.4%; and 50.0 mg = 27.8%). In conclusion, both days of the estrous cycle and doses of PGF2α influenced the incidence of complete and partial luteolysis in Nellore cows and should be an important consideration when devising estrus synchronization programs in this species.

Amniotic cell culture during different ages of gestation for karyotype analysis in bovine

Bovine karyotyping has become an important diagnostic tool in animal breeding. In the prenatal period it can diagnose several chromosomal abnormalities such as Robertsonian translocations, testicle feminization syndrome, gonadal dysgenesis and Klinefelter's syndrome. An important cell source for karyotype analysis is the amniotic fluid. It has been extensively used in humans but in bovine, however, this is not the case despite its diagnostic value. Since a small percentage of cells is viable, cells and their growth conditions as well as the handling of the material should be optimal to insure a successful analysis. For this, we have compared the growth efficiency for bovine amniocytes in two media, employing cells from 10 to 14 weeks of gestation. Amniocytes were cultured in the Amniomax (Gibco-BRL/ Life Technologies, Rockville, MD USA) medium during eleven days and in the RPMI 1640 (Gibco-BRL) medium during sixteen days at 37§C and 5 por cento CO2, then fixed and GTG banded. All the cultures with RPMI showed a poor cell growth, regardless the gestational age. Out of the samples cultured in Amniomax one presented 100 por cento of cellular confluence at day 11 (10 weeks of gestation) and the others resulted in an increased proliferation compared with those that were cultured in RPMI. To ensure a successful karyotyping, amniotic fluid from cows with gestational ages of 10-12 weeks should be used and care should be taken for critical steps in preparation of spread metaphases - hypotonic and trypsin treatments