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| Author(s): |
Bruna Martins Guerreiro
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2015-03-04 |
| Examining board members: |
Pietro Sampaio Baruselli;
Roberto Sartori Filho;
Marcelo Marcondes Seneda
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| Advisor: | Pietro Sampaio Baruselli |
| Abstract | |
The in vitro embryo production of high productive dairy cows (Bos taurus) presents low efficiency in comparison to Bos indicus females. In this context, the use of heifers of 8-10 months age as oocyte donors could be an alternative in order to improve results of this biotechnology and accelerate the genetic gain by the reduction of the interval between generations. However, informations about the in vitro production of embryos coming from prepubertal donors are controversial at literacture. Thus, the objective of the present study was to evaluate the in vivo ovum pick-up (OPU), followed by in vitro embryo production of prepubertal Holstein donors and the conception rate after embryo transfer. The study was performed at Santa Rita farm, with a completely randomized experimental design, performed in six consecutive replicates with distinct animals. A total of 120 donors of four animal categories: prepubertal heifers (PP, n = 30), pubertal heifers (PU, n = 30), lactating cows (LC, n = 30) and non-lactating cows (NLC, n = 30) were submitted to OPU without previous synchronization of follicular wave. Six OPU sessions ware performed with five animals of each category i.e., 20 donors per session. Immediately before the OPU, all follicles were quantified and classified according to their diameter [small (SF ≤ 6 mm), medium (MF = 6 to 10 mm) and large (LF ≥ 10 mm) follicles]. Subsequently, all visible follicles (≥ 2 mm) were punctured and the total recovered structures, quantity and quality of viable oocytes were registered. All viable oocytes were submitted to the in vitro embryo production and their development (cleavage and blastocyst rate) was evaluated. Sex-sorted sperm from the same bull and semen batch were used for the oocytes fertilization of all donor categories. The embryos produced (n = 206) were transferred in crossbred recipients (Bos taurus x Bos indicus). Number of follicles at OPU day, proportion of follicles according to its diameter, number of total and viable oocytes, recovery rate, clivage rate, number of embryos produced per OPU and blastocyst rate were the variables analyzed by the GLIMMIX procedure of SAS® and conception rate by the Fishers exact test. No difference was observed between the experimental groups, regarding the total number of aspirated follicles (PP: 18.3 ± 2.1; PU: 17.3 ± 1.2; LC: 14.0 ± 1.0; NLC: 17.7 ± 1.7; P = 0.08). However, PP donors presented higher proportion of small follicles (PP: 58.4% a; PU: 45.7% b; LC: 41.7% b; NLC: 50.6% b; P < 0.0001) in comparison to other categories. Despite the similar number of total recovered oocytes (PP: 14.2 ± 2.2; PU: 13.1 ± 1.1; LC: 9.8 ± 1.1; NLC: 14.6 ± 1.7; P = 0.12), PP presented intermediate quantity of viable oocytes (PP: 10.5 ± 1.8 ab; PU: 8.3 ± 0.8 ab) and NLC produced more viable oocytes (11.5 ± 1.4 a; P = 0.03) in comparison to LC (6.5 ± 0.9 b). Still, PP donors presented lower clivage rate (PP: 68.6% b; PU: 98.8% a; LC: 87.6 a; NLC: 90.1 a; P < 0.0001), fewer embryos produced per OPU session (PP: 0.5 ± 0.2 b; PU: 1.1 ± 0.2 b; LC: 1.2 ± 0,4 b; NLC: 4.2 ± 0.6 a; P < 0.0001) and lower blastocyst rate (PP: 4.8% c; PU: 12.7% b; LC: 18.0% b; NLC: 36.5% a; P < 0.0001) in comparison to other categories. Lastly, it was observed a different conception rate among heifers and adult cows [PP: 0.0% (0/15)b; PU: 9.7% (3/28)b; LC: 28.6% (10/25)a; NLC: 32.7% (36/74)a; P < 0.05]. Thus, it is concluded that prepubertal Holstein donors present low competence for in vitro embryo production, being non-lactating cows the most efficient category for IVEP. Yet, PP embryos resulted in inferior conception rate in comparison to LC and NLC embryos. However, similar conception rate was verified between PP and PU embryos. (AU) | |
| FAPESP's process: | 12/25290-9 - Production in vitro embryo of donors prepubertal Hostein |
| Grantee: | Bruna Martins Guerreiro |
| Support Opportunities: | Scholarships in Brazil - Master |