In vivo production, quality and pregnancy of bovine embryos from cows with high or low intake of dry matter or energy

Abstract Text:

This study evaluated the influence of dry matter (DM) or energy intake on in vivo embryo production and quality. Nonlactating Nelore cows (n=32, 4 to 10 y old) weighing 489.5±11.3 kg and with BCS of 3.3 (1 to 5) were used. After 15 d on a maintenance diet [1.2% of DM per kg of body weight (BW)], cows were randomly divided into four groups. Maintenance (M), 0.7M, and 1.5M received the equivalent of 70, 100 and 150% of the M diet, respectively. The fourth group (Energy; E) received a diet with DM similar to the M group, but with an energy level equivalent to the 1.5M group. Cows were fed individually and offered all diets in a Latin-square arrangement every 42 d. Cows were submitted to a conventional superovulation protocol. Superovulatory response was assessed by ultrasonography and embryo quality was evaluated according to the IETS guidelines, as well as by pregnancy per fixed-time transfer (P/ET) of 274 vitrified embryos to Nelore recipients. Pre-prandial blood plasma insulin was performed by RIA at the onset of superovulation. Data were analyzed by PROC GLIMMIX of SAS (P<0.05). Circulating insulin was greater in the E group (8.7±0.9 µIU/mL) compared with groups 0.7 M (4.6±0.9) and M (5.3±0.85), not differing from group 1.5M (6.6±0.9). Superovulation (CL number) was lower in donors fed high energy (9.7±1.2) compared with cows receiving the standard diet [0.7M (13.0±1.3), M (14.2±1.2) or 1.5M (13.9±1.2)] due to the negative correlation between circulating insulin and CL number (r=-0.32). Nevertheless, there was no difference between groups for number of ova/embryos (~6), viable (~3), or freezable embryos (~2.7). Regardless of treatment, circulating insulin was negatively correlated with the number of viable embryos (r=-0.22). There was lower P/ET at 60 d in the 97 cows receiving embryos from donors fed high energy (E; 29.4%) compared with the 177 cows receiving embryos from donors fed the standard diet (0.7M, M or 1.5M; 43.3%). Moreover, probability of P/ET at 60 d evaluated by logistic regression decreased as circulating insulin of donor cows increased from 0.64 to 25.0 µIU/mL. In conclusion, there was effect of diet on the superovulatory response and P/ET. Additionally, high circulating insulin of the donors was associated with lower superovulatory response, less viable embryos and less P/ET at 60 d. Financial support from FAPESP and CNPq. We also thank InVitro Brasil and Hildergard Pritzelwitz Experimental Station.

Keywords: cattle, fertility, insulin, nutrition