Objectives were to investigate the effects of supplementation with corn dried distiller’s grains plus solubles (DDGS) to late gestating beef cows on arterial blood flow to the mammary glands during late gestation and early lactation; colostrum and milk production; dystocia and immunity; and calf BW. Cows were fed a control (CON; n = 15; 5.1% CP; 36.2% ADF) diet consisting of 90% corn stover and 10% corn silage on a dry basis offered ad libitum or CON diet with supplementation of DDGS (0.30% of BW; SUP n = 12). Mammary gland blood flow was assessed on day 245 of gestation. At parturition, maternal and calving parameters were assessed; colostrum and jugular blood was sampled; and dams were weighed. Mammary gland blood flow and milk production was measured on day 44 of lactation. Calves were weighed fortnightly for 8 wk and at weaning. Colostrum production tended to be greater in SUP dams than in CON dams (837 vs. 614 ± 95 g, P = 0.10). Calves of SUP dams were heavier at birth and 24 h (0 h, 43.2 vs. 39.8 ± 1.0 kg, P = 0.02; 24 h, 44.0 vs. 40.4 ± 1.1 kg, P = 0.02). At birth and 24 h, blood pCO₂ was greater in calves born to SUP dams (6.82 vs. 6.00 ± 0.41 kPa, P = 0.04). Serum IgG did not differ (P = 0.21) at 24 h. Ipsilateral mammary gland blood flow of SUP cows was greater than CON cows (2.76 vs. 1.76 ± 0.30 L/min; P = 0.03); however, when summed with contralateral, total blood flow was similar (P = 0.33). Hemodynamic measures on day 44 of lactation were similar (P ≥ 0.32). Milk production tended to be increased (13.5 vs. 10.2 ± 1.2 kg/d, P = 0.07) in SUP vs. CON cows. Despite similar BW through 56 d, calves from SUP cows were heavier (P = 0.04) at weaning (309.7 vs. 292.0 ± 6.0 kg). In conclusion, we accept our hypothesis that DDGS supplementation during gestation influenced mammary blood flow, milk production and calf weights. These findings implicate maternal nutrition’s leverage on both nutrient and passive immunity delivery to the calf early in life as well as potential advantages on long-term performance.

In the ruminant placenta, glucose uptake and transfer are mediated by facilitative glucose transporters SLC2A1 (GLUT1) and SLC2A3 (GLUT3). SLC2A1 is located on the basolateral trophoblast membrane, whereas SLC2A3 is located solely on the maternal-facing, apical trophoblast membrane. While SLC2A3 is less abundant than SLC2A1, SLC2A3 has a five-fold greater affinity and transport capacity. Based on its location, SLC2A3 likely plays a significant role in the uptake of glucose into the trophoblast. Fetal hypoglycemia is a hallmark of fetal growth restriction (FGR), and as such, any deficiency in SLC2A3 could impact trophoblast glucose uptake and transfer to the fetus, thus potentially setting the stage for FGR. By utilizing in vivo placenta-specific lentiviral-mediated RNA interference (RNAi) in sheep, we were able to significantly diminish (p ≤ 0.05) placental SLC2A3 concentration, and determine the impact at mid-gestation (75 dGA). In response to SLC2A3 RNAi (n = 6), the fetuses were hypoglycemic (p ≤ 0.05), exhibited reduced fetal growth, including reduced fetal pancreas weight (p ≤ 0.05), which was associated with reduced umbilical artery insulin and glucagon concentrations, when compared to the non-targeting sequence (NTS) RNAi controls (n = 6). By contrast, fetal liver weights were not impacted, nor were umbilical artery concentrations of IGF1, possibly resulting from a 70% increase (p ≤ 0.05) in umbilical vein chorionic somatomammotropin (CSH) concentrations. Thus, during the first half of gestation, a deficiency in SLC2A3 results in fetal hypoglycemia, reduced fetal development, and altered metabolic hormone concentrations. These results suggest that SLC2A3 may be the rate-limiting placental glucose transporter during the first-half of gestation in sheep.

Deficiency of the placental hormone chorionic somatomammotropin (CSH) can lead to the development of intrauterine growth restriction (IUGR). To gain insight into the physiological consequences of CSH RNA interference (RNAi), the trophectoderm of hatched blastocysts (nine days of gestational age; dGA) was infected with a lentivirus expressing either a scrambled control or CSH-specific shRNA, prior to transfer into synchronized recipient sheep. At 90 dGA, umbilical hemodynamics and fetal measurements were assessed by Doppler ultrasonography. At 120 dGA, pregnancies were fitted with vascular catheters to undergo steady-state metabolic studies with the ³H₂O transplacental diffusion technique at 130 dGA. Nutrient uptake rates were determined and tissues were subsequently harvested at necropsy. CSH RNAi reduced (p ≤ 0.05) both fetal and uterine weights as well as umbilical blood flow (mL/min). This ultimately resulted in reduced (p ≤ 0.01) umbilical IGF1 concentrations, as well as reduced umbilical nutrient uptakes (p ≤ 0.05) in CSH RNAi pregnancies. CSH RNAi also reduced (p ≤ 0.05) uterine nutrient uptakes as well as uteroplacental glucose utilization. These data suggest that CSH is necessary to facilitate adequate blood flow for the uptake of oxygen, oxidative substrates, and hormones essential to support fetal and uterine growth.

The objective of this study was to investigate the effects of supplementing dried distillers' grains plus solubles (DDGS) during late gestation on uterine blood flow (BF), circulating steroid hormones and hepatic steroid metabolizing enzymes, and calf and placental weights. Multiparous beef cows were randomly divided into a control group (CON; n = 15) consuming a diet containing 90% corn stover and 10% corn silage (DM basis) for ad libitum intake and a treatment group (SUP; n = 12) consuming the same diet and DDGS (0.3% of BW). Corn silage inclusion was increased to 30% as gestation progressed to meet increasing caloric requirements. Ipsilateral and contralateral uterine BF and cross-sectional area (CSA) of each uterine artery were measured by Doppler ultrasonography on d 180, 216, and 246 of pregnancy. Contralateral BF and CSA increased (P < 0.01) as gestation advanced. Ipsilateral BF and CSA was affected by a treatment × day of gestation interaction (P < 0.05). A main effect of treatment (P = 0.02) and day (P < 0.01) was observed for total BF; BF increased over time and SUP cows had greater BF than CON cows. Circulating concentrations of both progesterone (P4) and estradiol-17β (E2) were affected by an interaction of treatment and day (P < 0.01). Concentrations of circulating E2 steadily increased throughout the study and were greater in CON cows than in SUP cows by d 242. Concentrations of P4 also increased over time; P4 of CON cows was greater than that of SUP cows by d 242. Uridine 5′-diphospho-glucuronosyltransferase (UGT) and cytochrome P450 1A (CYP1A) activity increased with advancing gestation (P < 0.01). There was greater UGT activity (P < 0.05) and a trend for greater CYP1A activity (P = 0.06) in SUP cows than in CON cows. Activity of cytochrome P450 3A was greater (P < 0.01) in SUP cows and decreased (P < 0.05) with advancing gestation. Supplementing DDGS to cows fed low-quality forage during late gestation increased uterine BF but decreased circulating E2 and P4 concentrations and altered hepatic steroid metabolizing enzyme activity. It was anticipated that enzyme activity would reflect circulating hormone levels; however, our data suggests the observed increases in BF are not driven by alterations in hormone concentration. Therefore, further research is warranted to elucidate the underlying mechanisms.

To investigate the effects of corn dried distillers grains plus solubles (DDGS) supplementation to cows fed corn stover and silage during late gestation, 27 multiparous beef cows (674 ± 17 kg; BCS, 5.6 ± 0.1) were divided randomly into 2 pens equipped with electronic feeders. For 10 wk, both groups were fed the basal diet for ad libitum intake while 1 group was supplemented (SUP; n = 12) with DDGS at 0.3% of BW (DM basis). Following parturition, all cows received the same diet for an additional 8 wk. During gestation, SUP cows gained BW (P < 0.01), and there was no change in BCS (P = 0.79). Nonsupplemented (CON) cows tended to lose BW (P = 0.06) and lost BCS (P < 0.01) during gestation. Supplemented cows consumed more forage (P < 0.01) and total feed than CON cows. An interaction of treatment and day was observed for time spent consuming forage (P < 0.01); SUP cows consumed forage faster than CON cows (P ≤ 0.01) early in gestation. Control cows ate more meals than SUP cows (P = 0.06) from d 201 to 218 of gestation. Supplemented cows tended (P = 0.09) to consume larger meals than CON cows and spent more (P < 0.01) time eating than CON cows around d 240 of gestation. Calves born to SUP cows tended (P = 0.06) to be heavier than calves born to CON cows. During lactation, both groups gained (P < 0.01) BW. Body condition score was less (P < 0.05) in CON cows than it was in SUP cows at the end of the study. Dry matter intake during lactation increased (P < 0.01) over time but was not influenced (P = 0.44) by treatment. Supplemented cows spent more time (P < 0.01) eating than CON cows after wk 4 of lactation, and they ate faster than CON cows until wk 3 of lactation whereas CON cows ate faster than SUP cows after wk 6 of lactation (P = 0.01). The number of meals increased with advancing lactation (P < 0.01) and CON cows averaged more meals daily than SUP cows (P = 0.01). Conversely, meal size decreased as lactation advanced (P < 0.01), and SUP cows consumed larger meals than CON cows (P = 0.05). Supplementation with DDGS during gestation influenced intake behavior during gestation and lactation as well as the maintenance of maternal BW and BCS and calf birth BW.