To examine effects of nutrient restriction and dietary Se on maternal and fetal visceral tissues, 36 pregnant Targhee-cross ewe lambs were allotted randomly to 1 of 4 treatments in a 2 × 2 factorial arrangement. Treatments were plane of nutrition [control, 100% of requirements vs. restricted, 60% of controls] and dietary Se [adequate Se, ASe (6 μg/kg of BW) vs. high Se, HSe (80 μg/kg of BW)] from Se-enriched yeast. Selenium treatments were initiated 21 d before breeding and dietary restriction began on d 64 of gestation. Diets contained 16% CP and 2.12 Mcal/kg of ME (DM basis) and differing amounts were fed to control and restricted groups. On d 135 ± 5 (mean ± range) of gestation, ewes were slaughtered and visceral tissues were harvested. There was a nutrition × Se interaction (P = 0.02) for maternal jejunal RNA:DNA; no other interactions were detected for maternal measurements. Maternal BW, stomach complex, small intestine, large intestine, liver, and kidney mass were less (P ≤ 0.01) in restricted than control ewes. Lung mass (g/kg of empty BW) was greater (P = 0.09) in restricted than control ewes and for HSe compared with ASe ewes. Maternal jejunal protein content and protein:DNA were less (P ≤ 0.002) in restricted than control ewes. Maternal jejunal DNA and RNA concentrations and total proliferating jejunal cells were not affected (P ≥ 0.11) by treatment. Total jejunal and mucosal vascularity (mL) were less (P ≤ 0.01) in restricted than control ewes. Fetuses from restricted ewes had less BW (P = 0.06), empty carcass weight (P = 0.06), crown-rump length (P = 0.03), liver (P = 0.01), pancreas (P = 0.07), perirenal fat (P = 0.02), small intestine (P = 0.007), and spleen weights (P = 0.03) compared with controls. Fetuses from HSe ewes had heavier (P ≤ 0.09) BW, and empty carcass, heart, lung, spleen, total viscera, and large intestine weights compared with ASe ewes. Nutrient restriction resulted in less protein content (mg, P = 0.01) and protein:DNA (P = 0.06) in fetal jejunum. Fetal muscle DNA (nutrition by Se interaction, P = 0.04) concentration was greater (P < 0.05) in restricted ewes fed HSe compared with other treatments. Fetal muscle RNA concentration (P = 0.01) and heart RNA content (P = 0.04) were greater in HSe vs. ASe ewes. These data indicate that maternal dietary Se may alter fetal responses, as noted by greater fetal heart, lung, spleen, and BW.

Managing nutrient supply to match demand is critical for sustainable and efficient livestock production. The California Net Energy System (CNES) was developed during the late 1950s and 1960s, as documented in the classic publication of Lofgreen and Garrett (1968). This system was a significant step forward and has served the beef cattle industry well during the past 50 yr. Energy requirements for maintenance (NEm) and gain (NEg), described by Lofgreen and Garrett (1968) as modified by expanding databases ( Garrett 1980) and for specific situations [ National Research Council (NRC), 1984, 1996, 2000; The National Academies of Sciences, Engineering, and Medicine (NASEM), 2016], are used worldwide as a basis for feeding beef cattle and often other ruminant species as well.

The objectives were to evaluate effects of maternal nutrient restriction and stage of gestation on maternal and fetal visceral organ mass and indices of jejunal growth and vascularity in beef cows. Thirty multiparous beef cows (BW = 571 ± 63 kg; BCS = 5.4 ± 0.7) carrying female fetuses (d 30 of gestation) were allocated to receive a diet of native grass hay (CON; 12.1% CP, 70.7% IVDMD, DM basis) to meet NRC recommendations for BW gain during early gestation or a nutrient-restricted diet of millet straw (NR; 9.9% CP, 54.5% IVDMD, DM basis) to provide 68.1% of NE_m and 86.7% of MP estimated requirements. On d 125 of gestation, 10 CON and 10 NR cows were killed and necropsied. Five remaining CON cows received the CON diet, and 5 NR cows were realimented with a concentrate supplement (13.2% CP, 77.6% IVDMD, DM basis) and the CON hay to achieve a BCS similar to CON cows by d 220 of gestation. Remaining cows were necropsied on d 245 of gestation. Cow BW and eviscerated BW (EBW) were less (P < 0.01) for NR than CON at d 125 but did not differ (P > 0.63) at d 245. Cows fed the CON diet had greater (P < 0.09) total gastrointestinal (GI) tract, omasal, and pancreatic weights. Stomach complex, ruminal, and liver weights were greater for CON than NR cows (P < 0.09) on d 125. Total GI, stomach complex, and pancreatic weights increased (P < 0.001) with day of gestation. Restricted cows had decreased (P = 0.09) duodenal RNA:DNA compared with CON. Duodenal DNA was less (P = 0.01) and jejunal RNA:DNA (P = 0.09) was greater for cows at d 125 vs. 245. Cow jejunal capillary area density increased with day of gestation (P = 0.02). Fetal BW and EBW were unaffected by dietary treatment (P ≥ 0.32). Total GI tract and all components increased in mass with day of gestation (P < 0.001). Fetuses from NR dams had greater (P = 0.003) reticular mass at d 245 than CON fetuses. Fetuses from NR cows had greater (P = 0.02) percent jejunal proliferation at d 125 and greater (P = 0.03) total intestinal vascularity (mL) at d 245. Fetal jejunal DNA decreased (P = 0.09), RNA:DNA increased (P = 0.05), and total jejunal proliferating cells increased (P < 0.001) with day of gestation. Jejunal capillary area density, number density, and surface density were greater (P < 0.008) during late gestation. Results indicate that maternal and fetal intestines undergo changes during gestation, which can be affected by nutrient restriction and may partially explain differences observed in fetal development and postnatal performance. Copyright © 2010. American Society of Animal Science .

The objectives were to investigate effects of nutritional plane and Se supply during gestation on yield and nutrient composition of colostrum and milk in first parity ewes. Rambouillet ewe lambs (n = 84, age = 240 ± 17 d, BW = 52.1 ± 6.2 kg) were allocated to 6 treatments in a 2 × 3 factorial array. Factors included Se [adequate Se (ASe, 11.5 µg/kg of BW) or high Se (HSe, 77.0 µg/kg of BW)] initiated at breeding, and nutritional plane [60 (RES), 100 (CON), or 140% (HIH) of requirements] initiated at d 40 of gestation. Ewes were fed individually from d 40, and lambs were removed at parturition. Colostrum was milked from all ewes at 3 h postpartum, and one-half of the ewes (n = 42) were transitioned to a common diet meeting lactation requirements and mechanically milked for 20 d. Colostrum yield was greater (P = 0.02) for HSe ewes than ASe, whereas CON had greater (P < 0.05) colostrum yield than RES and HIH. Colostrum Se (%) was greater (P < 0.01) for HSe than ASe. Colostrum from ewes fed HSe had less (P = 0.03) butterfat (%), but greater (P ≤ 0.05) total butterfat, solids-not-fat, lactose, protein, milk urea N, and Se than ASe. Colostrum from HIH ewes had greater (P ≤ 0.02) solids-not-fat (%) than RES, whereas RES had greater (P ≤ 0.04) butterfat (%) than CON and HIH. Colostrum from ewes fed the CON diet had greater (P = 0.01) total butterfat than HIH. Total solids-not-fat, lactose, and protein were greater (P < 0.05) in colostrum from CON than RES and HIH. Ewes fed HSe had greater (P < 0.01) milk yield (g/d and mL/d) than ASe, and CON and HIH had greater (P < 0.01) yield than RES. Milk protein (%) was greater (P ≤ 0.01) in RES compared with CON or HIH. Ewes fed HSe had greater (P < 0.01) milk Se (µg/g and mg/d) than ASe on each sampling day. Milk from CON and HIH ewes had greater (P < 0.01) total solids-not-fat, lactose, protein, and milk urea N than RES. Total Se was greater (P = 0.02) in milk from ewes fed the CON diet compared with RES. Somatic cell count and total somatic cells were greater (P ≤ 0.05) in milk from CON than RES. A cubic effect of day (P ≥ 0.01) was observed for milk yield (g and mL). Butterfat, solids-not-fat, lactose, milk urea N, and Se concentration responded quadratically (P ≤ 0.01) to day. Protein (%), total butterfat, and total Se, and somatic cells (cells/mL and cells/d) decreased linearly (P < 0.01) with day. Results indicate that gestational nutrition affects colostrum and milk yield and nutrient content, even when lactational nutrient requirements are met. Copyright © 2011. American Society of Animal Science .

The focus of this review is maternal nutrition during the periconceptual period and offspring developmental outcomes in beef cattle, with an emphasis on the first 50 d of gestation, which represents the embryonic period. Animal agriculture in general, and specifically the beef cattle industry, currently faces immense challenges. The world needs to significantly increase its output of animal food products by 2050 and beyond to meet the food security and agricultural sustainability needs of the rapidly growing human population. Consequently, efficient and sustainable approaches to livestock production are essential. Maternal nutritional status is a major factor that leads to developmental programming of offspring outcomes. Developmental programming refers to the influence of pre-and postnatal factors, such as inappropriate maternal nutrition, that affect growth and development and result in long-term consequences for health and productivity of the offspring. In this review, we discuss recent studies in which we and others have addressed the questions, “Is development programmed periconceptually?” and, if so, “Does it matter practically to the offspring in production settings?” The reviewed studies have demonstrated that the periconceptual period is important not only for pregnancy establishment but also may be a critical period during which fetal, placental, and potentially postnatal development and function are programmed. The evidence for fetal and placental programming during the periconceptual period is strong and implies that research efforts to mitigate the negative and foster the positive benefits of developmental programming need to include robust investigative efforts during the periconceptual period to better understand the implications for life-long health and productivity.