Effect of food supplementation on in vitro embryo production and growth performance in prepubertal Nelore heifers.

In vitro embryos production from prepubertal heifers can help contribute to breeding programs; however, strategies are necessary to increase their embryo production. The aim of this study was to investigate the effects of two nutritional plans on oocyte recovery, embryo production and growth performance of prepubertal Nelore heifers. Thirty-four Nelore heifers with age of 6.5 months were divided into two feeding treatments (NP1 and NP2). The NP1 diets served as the control and NP2 diets were formulated to contain an average of 1.22-fold more energy than NP1. After 3 months of supplementation, the animals underwent follicular aspiration (ovum pick-up, OPU) every 21 d for 3 months and embryos were produced in vitro. Wither height, chest depth, body weight and subcutaneous fat of animals were measured. The number of retrieved and viable oocytes per OPU were 1.49-fold and 1.42-fold greater in NP2 heifers (p = 0.018 and p = 0.049, respectively) than those in NP1 heifers. Heifers administered NP2 produced 29.7% blastocysts, a percentage higher than NP1 animals that produced 24.40% embryos (p < 0.05). Consequently, females in the NP2 treatment showed improved body development. These results indicate a positive effect of a higher energy diet on assisted reproduction and body development in prepubertal heifers.

Effect of delipidant agents during in vitro culture on the development, lipid content, gene expression and cryotolerance of bovine embryos.

In vitro produced embryos are still sensitive to the freezing process which can be explained, in part, by the high-lipid accumulation that characterizes these embryos. Therefore, we aimed to evaluate the effect of delipidating agents, L-carnitine and the trans-10 cis-12 conjugated linoleic acid (CLA) isomer, on blastocyst development, lipid content, gene expression and cryotolerance when added to embryo culture media. Embryos were cultured in four different media: T1: control (n = 616), synthetic oviduct fluid (SOF) media with 5% foetal bovine serum (FBS); T2: L-carnitine (n = 648), SOF medium with 5% FBS and 0.6 mg/ml of L-carnitine; T3: CLA (n = 627), SOF medium with 5% FBS and 100 µM trans-10 cis-12 CLA; and T4: L-carnitine + CLA: (n = 597), SOF medium with 5% FBS plus 0.6 mg/ml L-carnitine and 100 µM trans-10 cis-12 CLA. Supplementation of culture medium with either or both delipidating agents reduced (p < .05) blastocyst rate on D7 (T1 = 49 ± 3.5; T2 = 39 ± 3.0; T3 = 42 ± 3.9 and T4 = 39 ± 3.9), but did not affected gene expression (p > .05). Although embryos cultured in the presence of L-carnitine contained fewer (p < .05) lipid droplets than the control embryos, they showed a lower re-expansion rate 24 hr post-thaw than those (p < .05). In conclusion, although L-carnitine reduced the amount of lipids in cultured embryos, the use of L-carnitine and CLA during in vitro culture was not able to improve the embryo production and the response to cryopreservation.