Effects of Pre- and Post-Insemination Maternal Plane of Nutrition on Peripheral and Uterine Luminal Fluid Metabolites.

Nutritional changes immediately after insemination can affect embryonic survival, but the mechanisms that cause embryonic mortality are not known. Therefore, the objective of this study was to evaluate the impact of a nutritional change before or after AI on peripheral and uterine luminal fluid (ULF) metabolites. Sixty Angus-cross heifers (351±47 kg) were allotted into two pre-AI treatments with Low heifers limit-fed to achieve 70% maintenance 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). Blood samples were collected daily from AI to day 6, when uteri were flushed. Heifer weights, energy intake, and plasma concentrations of NEFA, glucose, and protein were analyzed by repeated measures using the MIXED procedure in SAS, and ULF concentrations of NEFA, glucose, and protein were analyzed using the GLM procedure of SAS. There was a treatment x time effect on energy intake and weight change: LL lost weight throughout the study (-0.81±0.24 kg/d), HH maintained weight (0±0.26 kg/d), HL maintained weight prior to AI (0.26±0.29 kg/d) but lost weight following AI (-2.90±1.42 kg/d), and LH lost weight prior to AI (-0.72±0.22 kg/d) but gained following AI (1.37±0.94 kg/d). Heifers in the LL (0.59±0.04 mEq/L) and HL treatments (0.61±0.04 mEq/L) had greater plasma NEFA concentrations (P<0.01) compared to LH heifers (0.37±0.04 mEq/L) and HH heifers (0.34±0.04 mEq/L). However, ULF NEFA concentrations were not impacted by pre-AI (P=0.95) or post-AI treatment (P=0.74). Treatment impacted plasma protein concentrations (P<0.01), with LL heifers (0.61±0.007 mcg/mL) having greater plasma protein concentrations than LH (0.58±0.007 mcg/mL) and HH heifers (0.57±0.007 mcg/mL) but similar concentrations compared to HL heifers (0.59±0.007 mcg/mL). Neither time (P=0.22) nor treatment by time (P=0.84) impacted plasma protein concentrations, and ULF concentrations of protein were not impacted by pre-AI (P=0.55) nor post-AI treatment (P=1.0). Treatment did not impact plasma glucose concentrations (P=0.49); however, time did (P=0.002), with greatest concentrations occurring on d 0 (0.75±0.02 mg/dL) and d 3 (0.71±0.02 mg/dL) and declining on d 6 (0.66±0.02 mg/dL). There was no interaction (P=0.81). Furthermore, ULF glucose was not impacted by pre-AI (P=0.41) or post-AI treatment (P=0.70). In summary, nutritional changes at time of AI impacted circulating concentrations of NEFA and protein, but did not impact ULF concentrations on d 6 after insemination.