In vitro development of parthenote embryos derived from goats supplemented with short nutritional flushing

The use of short period feed supplementation (short nutritional flushing) influence the reproductive performance of domestic ruminants, improving follicular development and oocyte quality by stimulating folliculogenesis. This dynamic supplementation is mediated by metabolites acting in the ovaries, influencing subsequent embryo development and contributing to the increase in reproductive efficiency. Thus, the objective of this study was to investigate the effects of short nutritional flushing in goats on the development of parthenote embryos produced in vitro. Thirty adult mixed breed goats, with homogenous body condition score (3.0 ± 0.2; Mean ± SD), body mass index (7.2 ± 0.8) and age (28.2 ± 3.4 months), were grouped in three (n = 10) shaded collective boxes and fed with a total mixed ration (TMR) based on chopped elephant grass (Pennisetum purpureum spp.) and concentrate (10% Crude Protein and 67% Total Digestible Nutrients). Feed mixture was furnished to satisfy the requirement of breeding for adult non-dairy goats (NRC, 2007), during 15 days, from estrus synchronization to oocyte recovery. Seven days prior to oocyte recovery, the three groups of animals (n=10 each) were fed on a daily basis was maintained with: (a) TMR diet (Control Group, CG); (b) 200 mL/goat of crude glycerin (80% glycerin) and water in a 9:1 ratio (Glycerin Group, GG), with each dose of crude glycerin equivalent to 1.03 Mcal of metabolizable energy; and (c) ground flaxseed (Linum usitatissimum L.) on a 30% Dry Matter basis (Linseed Group, LG). The TMR feed mixture in the CG and LG groups were prepared in a water solution. Estrus synchronization was initiated by the insertion of an intravaginal progesterone (CIDR®) insert on Day 0 (D0), 12 days prior to slaughter. On Day 6 (D6) the intravaginal insert was removed and 0.075 mg PGF2a (Prolise®) and 150 IU eCG (Folligon®) were given i.m. After 36 h (Day 7), a 0.125-mg GnRH (Gestran®) dose was given i.m. For superovulation, a total of 200 mg pFSH (Folltropin®) was applied i.m. at 12 h intervals (5 applications of 40 mg/mL) from Day 9 (D9) thorugh Day 11 (D11) (Menchaca et al., 2007). Ovaries were collected upon slaughter on Day 12 (D12), 6 h after the last FSH injection, and transported to the laboratory in saline solution at 25°C. Then, cumulus-oocyte complexes (COCs) were recovered by follicular aspiration, classified morphologically and selected (viable) COCs were placed to in vitro maturation (IVM). After 24 h, matured oocytes selected by the extrusion of the first polar body were parthenogenetically activated by exposure to 5 mM ionomycin for 5 min, followed by an incubation in 2 mM 6- DMAP for 4 h. After activation, oocytes were in vitro–cultured (IVC) in G-1 medium (Vitrolife®), in an incubator at 39o C and 5% CO2 for seven days. Cleavage and blastocyst rates were evaluated on Days 2 and 7 of IVC, respectively. Embryos were classified as viable and non-viable, and in compact morula or blastocyst stages, in accordance with embryonic development. Data were analyzed by the Chi-square test (P<0.05). The LG treatment had significantly lower maturation (73%; 86/118 vs. 84%; 98/116) and cleavage (86%; 74/86 vs. 96%; 94/98) rates than the CG, respectively, with results in GG group being similar to the other two groups. Morula (LG:23%, 8/35; GG:34%, 11/32; CG: 23%, 12/52) and blastocyst rates (LG: 77%, 27/35; GG:66%, 21/32; CG:77%, 40/52) were similar between groups, with a total mean embryo yield efficiency of 44% (119/269). We conclude that the short nutritional flushing protocols used in this study were not able to improve embryo production efficiency in goats. However, embryo production rates were excellent for the goat species, irrespective of the diet.