Effect of Pre- and Post-Insemination Maternal Plane of Nutrition on Estrus and Embryo Development.

Nutritional changes immediately after insemination can result in differential embryonic development. Therefore, the objective of this study was to evaluate the impact of a nutritional change before or after AI on estrus expression, interval to estrus, and day 6 embryo recovery, development, and quality. Sixty Angus-cross heifers (351 ± 47 kg) were allotted into two pre-AI treatments with Low heifers fed to achieve 70% and High heifers fed to achieve 125% maintenance requirements. Following AI, heifers were randomly reassigned within treatment, creating 4 nutritional treatments: low remaining low (LL), low moved to high (LH), high remaining high (HH), and high moved to low (HL). On day 6 after AI uteri were flushed. Interval to estrus was analyzed using the GLM procedure of SAS. Estrus expression and embryo recovery rates were analyzed with the GLIMMIX procedure in SAS while embryo stage and grade were analyzed using the MIXED procedure of SAS. No difference was observed between low and high for estrus expression (P = 0.22) or interval to estrus among heifers expressing estrus (P = 0.57). Pre-AI treatment did not impact embryo recovery rate (P = 0.57), but post-AI treatment approached a tendency (P = 0.12) with greater recovery rates from high (48.3 ± 9.1%) compared to low (27.4 ± 9.6%) heifers. There was no pre- by post-AI treatment interaction (P = 0.75). Embryo stage was impacted by pre-AI treatment (P = 0.05), with embryos that were more advanced from high (2.98 ± 0.4) compared to low heifers (1.79 ± 0.4). Post-AI treatment also tended to affect embryo stage (P = 0.07), with embryos being more advanced from high (2.93 ±0.3) compared to low heifers (1.83 ± 0.5). There was no pre- by post-AI interaction (P = 0.42). Pre-AI nutrition also approached a tendency to impact embryo grade (P = 0.17), with low heifers yielding poorer quality embryos (3.21 ± 0.4) compared to high heifers (2.40 ± 0.4). Post-AI nutrition also tended to affect embryo grade (P = 0.08), with low having poorer quality embryos (3.33 ± 0.5) compared to high heifers (2. 29 ± 0.5). However, there was no interaction on embryo quality (P = 0.37). In summary, nutritional status both before and after AI impact early embryo development, with undernutrition negatively influencing embryo development.