Full text
| |
| Author(s): |
Ricardo da Silva Surjus
Total Authors: 1
|
| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2013-02-28 |
| Examining board members: |
Roberto Sartori Filho;
Alexandre Vaz Pires;
José Nélio de Sousa Sales
|
| Advisor: | Roberto Sartori Filho |
| Abstract | |
Nutrition is closely related to reproduction and there is still much to learn about this relationship, mainly because there is so much controversy in the literature on this topic. For example, some studies propose beneficial use of nutritional \"flushing\" on embryo production in ruminants. However, most studies show negative results of high dry matter intake (DMI). Thus, there is a need to advance in studies comparing reproductive physiology and embryo production in females under different nutritional levels. A total of 33 non-lactating Nelore cows received one of the following treatments: Groups maintenance (M), Restriction (0.7M) and High DMI (1.5M) received the same standard diet with variations in the amount offered. The group High intake of energy (E) received a diet with high starch content, but the same amount of energy as group 1.5M, however, with the same DMI as Group M. All cows underwent all treatments in a crossover model. These animals had their estrus synchronized and ovarian dynamics was monitored daily by ultrasound until confirmation of ovulation. Subsequently, on days 7 and 10 of the estrous cycle the volume of the corpus luteum (CL) was estimated. Circulating concentrations of steroid hormones (progesterone [P4] and estradiol [E2]) were measured in strategic days. The cows underwent intrafollicular aspiration (OPU) on day 12 of the estrous cycle, and two days after OPU, the cows ovaries were supererstimulated. The superovulatory response and embryo quality was compared among groups, as well as pregnancy rate of 273 recipients after receiving fixed-time transfer of vitrified embryos. Analyses were performed according to the Proc GLIMMIX of SAS, with a significance level of P < 0.05. Results are presented as least squares means ± standard error. This study included two main areas: physiology and hormone concentrations (Experiment 1) and in vivo embryo production and pregnancy rate (Experiment 2). Although, in Experiment 1, 33 cows were evaluated in four repetitions, totaling 132 synchronizations, there were only 75 ovulations, which were considered for subsequent analyzes. The ovulation rate did not vary between treatments (~57%). The size of the ovulatory follicle incresed as the DMI of the standard diet increased (14.4 ± 0.3a vs 12.8 ± 0.3b vs 12.0 ± 0.3c for groups 1.5 M, M and 0.7M, respectively). Nevertheless, the circulating E2 did not differ between groups. The volume of the CL on Day 7 of the estrous cycle increased as the DMI of the standard diet increased, but the 1.5M group had lower circulating concentrations of P4 (2.4 ± 0.2 ng/mL) than groups M and 0.7M (2.9 ± 0.2 and 3.0 ± 0.3 ng/mL, respectively). In Experiment 2, plasma insulin concentration was higher in the E group (8.7 ± 0.86 ?IU/mL) compared with groups 0.7 M (4.6 ± 0.87) and M (5.3 ± 0.85) not differing from group 1.5M (6.6 ± 0.9). There was a higher superovulatory response (CL) in donors receiving the standard diet [0.7M (13.0 ± 1.3), M (14.2 ± 1.2) and 1.5M (13.9 ± 1.2)] compared with those fed high energy (9.7 ± 1.2 CL) due to the negative correlation between superovulatory response and circulating insulin (r = - 0.32). Nevertheless, there was no difference between groups for the total number of oocytes/embryos collected (~6 structures), viable embryos (~3 embryos), or freezable (~2.7 embryos). Regardless of treatment, circulating insulin at the beginning of superovulation, was negatively correlated with the number of viable embryos (r = -0.22). Pregnancies at 23 and 53 days after embryo transfer did not differ between treatments, however, circulating insulin of the donor cows had a negative correlation with pregnancy of recipients at 60 days of gestation (r = -0.16). In conclusion, different levels of DMI changed the size of ovarian structures and/or the concentrations of circulating steroid hormones. Nevertheless, there was a very minor effect of diet on superovulatory response and embryo quality in cows. Regardless of treatment, high circulating insulin of the donors was associated with lower superovulatory response, lower number of viable embryos and less pregnancies of recipients at 60 days of gestation. (AU) | |
| FAPESP's process: | 10/14494-7 - Embryo production and ovarian physiology in Nelore cows under different levels of nutriton |
| Grantee: | Ricardo da Silva Surjus |
| Support Opportunities: | Scholarships in Brazil - Master |