Effect of ovarian structure and bovine's age on amount and quality of oocytes and in vitro embryo production

Abstract

The aim of the present study was the evaluation of whether the age or the estrous cycle phase would influence the quantity and/or quality of oocytes and in vitro embryo production. Oocytes from ovaries of 63 Holstein- Friesian slaughtered cows, aging between 1 and 15 years old, were divided into 5 groups considering their age and then subdivided according to their phase of estrous cycle. The groups were: ;8 years old. The estrous cycle phase (lutheal or follicular) was evaluated by the presence or absence of a functional corpus luteum. The cumulus-oocyte-complex (COC's) was divided in classes A, B, C and D according to their morphological aspect. The COC's classed as C and D were excluded, being the COC's classed as A and B matured in vitro and fertilized. As result of the study, it was observed that the number of total produced COC's was directly proportional to the age of the cow (R=0,99 - P<0,001). It has also noticed that cows in the lutheal phase produced more COC's than cows in the follicular phase (P<0,001), respectively 7,05 ± 0,11 and 10,87 ± 1,01. The COC's quality augmented from the group of cows aging less than 2 years to cows aging between [7, 8] years old, with a positive correlation (R = 0.94 p<0.01) starting then to decrease. It was also realized that cows in the lutheal phase produced better COC's quality than cows in the follicular phase (6,77 ± 0,64 e 3,84± 0,64; respectively). In what cleavage rate is concerned, better results were achieve with cows in lutheal phase (59,03%) then in follicular phase (45,52%). It was also possible to notice a better embryo production in cows in the lutheal phase (44,23%) then cows in the follicular phase. The results of the present study allow to conclude that there is a relation between the age and the estrous cycle stage in the quality and quantity of COC's and in vitro produced bovine embryos.