Title: Effects of maternal nutrient restriction followed by re-alimentation during mid-gestation on uterine blood flow in beef cows Authors
|Camacho, L -|
|Lemley, C -|
|Prezotto, L -|
|Bauer, M -|
|Swanson, K -|
|Vonnahme, K -|
Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2014
Publication Date: N/A
Interpretive Summary: Beef cows are commonly managed in grazing systems where the quality of forage can negatively impact the nutritional and physiological status of the dam resulting in underdevelopment of their offspring at birth. Giving proper supplemental nutrition can mitigate the underdevelopment; however, there is a scarcity of information on how the timing of realimentation impacts placental and fetal development. Researchers at North Dakota State University and the U.S. Meat Animal Research Center determined that blood flow to the uterus during early gestation in cows that received a nutrient restriction did not differ from cows fed to meet nutrient requirements. However, when restricted cows received additional nutrients during late pregnancy, the blood flow to the portion of the uterus that contained the fetus increased above that of the control cows. These findings suggest that the placenta may be programmed to function differently after a period of nutrient restriction.
Technical Abstract: The objective was to examine the effect of maternal nutrient restriction followed by realimentation during mid-gestation on uterine blood flow (BF). On day 30 of pregnancy, lactating, multiparous Simmental beef cows were assigned randomly to treatments: control (CON; 100% NRC; n = 6) and nutrient restriction (RES; 60% of CON; n= 4) from day 30 to 140 (Period 1) and, thereafter, realimented to CON until day 198 of gestation (Period 2). Uterine BF, pulsatility index (PI), and resistance index (RI) were obtained from both the ipsilateral and contralateral uterine arteries via Doppler ultrasonography. Generalized least squares analysis was performed. Ipsilateral uterine BF in both groups increased quadratically (P < 0.01) during period 1 and linearly (P < 0.01) during Period 2. There was a treatment (P = 0.05) effect during Period 2; where RES cows had greater ipsilateral BF vs. CON. Ipsilateral uterine PI and RI decreased linearly (P = 0.01) during Period 1 across treatments. Contralateral uterine BF in CON cows tended (P < 0.09) to be greater vs. RES in both periods. Contralateral PI in both groups increased linearly (P = 0.01) during Period 1. Contralateral uterine RI was increased (P = 0.05) in RES cows vs. CON in both periods. There was no interaction or treatment effect (P = 0.24) for total BF during either period. Nutrient restriction does not alter total uterine BF, but it may increase vascular resistance. However, upon realimentation, local conceptus derived vasoactive factors appear to influence ipsilateral uterine BF.