Effects of poor maternal diet during gestation are detected in F2 offspring

Poor maternal nutrition of F0 ewes impairs F1 offspring growth, with minimal differences in glucose tolerance or select metabolic circulating factors, and independent of differences in residual feed intake (RFI). To determine if poor maternal nutrition in F0 ewes alters F2 offspring growth, circulating leptin, feed efficiency, or glucose tolerance, F0 ewes (n = 46) pregnant with twins were fed 100% (control), 60% (restricted), or 140% (over) of National Research Council requirements from days 30 ± 0.02 of gestation until parturition. At 16 to 19 mo of age, female F1 (n = 36) offspring were bred to generate F2 offspring [CON-F2 (n = 12 ewes; 6 rams), RES-F2 (n = 7 ewes; 13 rams), or OVER-F2 (n = 13 ewes; 9 rams) corresponding to diets of the granddam (F0)]. Lamb body weights (BW) and blood samples were collected weekly from days 0 to 28 and every 14 d until day 252 of age. Circulating leptin was measured in serum at days 0, 7, 14, 56, 210, and 252. An intravenous glucose tolerance test was performed at days 133 ± 0.28. At days 167 ± 0.33, individual daily intake was recorded over a 77-d feeding period to determine RFI. Rams were euthanized at days 285 ± 0.93, and body morphometrics, loin eye area (LEA), back fat thickness, and organ weights were collected and bone mineral density (BMD) and length were determined in the right hind leg. During gestation, OVER-F1 ewes tended to be 8.6% smaller than CON-F1 ewes (P ≤ 0.06). F2 offspring were of similar BW from birth to day 70 (P ≥ 0.20). However, from days 84 to 252, RES-F2 offspring tended to be 7.3% smaller than CON-F2 (P ≤ 0.10). Granddam diet did not influence F2 ram body morphometrics, organ or muscle weights, LEA, adipose deposition, or leg BMD (P ≥ 0.84). RES-F2 (-0.20) and CON-F2 (-0.45) rams tended to be more feed efficient than CON-F2 ewes (0.31; P ≤ 0.08). No effects of granddam diet were observed on glucose or insulin average or baseline concentrations, area under the curve, first-phase response, or ratio (P ≥ 0.52). However, CON-F2 rams (297 mg/dL ± 16.5) had a greater glucose peak compared with RES-F2 rams (239 mg/dL ± 11.2; P = 0.05). Peak insulin concentrations were not influenced by granddam diet (P = 0.75). At d 56, RES-F2 and OVER-F2 offspring had 53.5% and 61.8% less leptin compared with CON-F2 offspring, respectively (P ≤ 0.02). These data indicate that poor maternal nutrition impacts offspring growth into the second generation with minimal impacts on offspring RFI, glucose tolerance, and circulating leptin.

Restricted- and over-feeding during gestation decreases growth of offspring throughout maturity

To determine the effects of poor maternal nutrition on the growth and metabolism of offspring into maturity, multiparous Dorset ewes pregnant with twins (n = 46) were fed to either 100% (control; n = 13), 60% (restricted; n = 17), or 140% (over; n = 16) of National Research Council requirements from day 30 ± 0.02 of gestation until parturition. Offspring of these ewes are referred to as CON (n = 10 ewes; 12 rams), RES (n = 13 ewes; 21 rams), or OVER (n = 16 ewes; 13 rams), respectively. Lamb body weights (BW) and blood samples were collected weekly from birth (day 0) to day 28 and then every 14 d until day 252. Intravenous glucose tolerance test (infusion of 0.25 g dextrose/kg BW) was performed at day 133 ± 0.25. At day 167 ± 1.42, individual daily intake was recorded over a 77 d feeding period to determine residual feed intake (RFI). Rams were euthanized at day 282 ± 1.82 and body morphometrics, loin eye area (LEA), back fat thickness, and organ weights were collected. The right leg was collected from rams at necropsy and dual-energy x-ray absorptiometry was used to determine bone mineral density (BMD) and length. Averaged from day 0 until day 252, RES and OVER offspring weighed 10.8% and 6.8% less than CON offspring, respectively (P ≤ 0.02). When adjusted for BW, liver and testes weights tended to be increased and decreased, respectively, in RES rams compared with CON rams (P ≤ 0.08). Additionally, RES BMD and bone length were less than CON rams (P ≤ 0.06). Treatment did not influence muscle mass, LEA, or adipose deposition (P ≥ 0.41). Rams (-0.17) were more feed efficient than ewes (0.23; P < 0.01); however, no effect of maternal diet was observed (P ≥ 0.57). At 2 min post glucose infusion, glucose concentrations in OVER offspring were greater than CON and RES offspring (P = 0.04). Concentrations of insulin in CON rams tended to be greater than OVER and RES ewes at 5 min (P ≤ 0.07). No differences were detected in insulin:glucose or area under the curve (AUC) for glucose or insulin (P ≤ 0.29). Maternal diet did not impact offspring triglycerides or cholesterol (P ≤ 0.35). Pre-weaning leptin tended to be 70% greater in OVER offspring than CON (P ≤ 0.07). These data indicate that poor maternal nutrition impairs offspring growth throughout maturity but does not affect RFI. Changes in metabolic factors and glucose tolerance are minimal, highlighting the need to investigate other mechanisms that may contribute to negative impacts of poor maternal diet.

204 Awardee Talk: Poor Maternal Nutrition Impacts Metabolic Factors and Glucose Tolerance in Sheep Offspring

To evaluate the hypothesis that offspring born to restricted- and over-fed ewes would exhibit decreased glucose tolerance, total cholesterol (TC), and triglyceride (TG), and increased leptin, multiparous Dorset ewes (n = 46) pregnant with twins were fed 100%, 60% or 140% of National Research Council (NRC) requirements from d30±0.02 of gestation until parturition. Offspring are referred to as CON (n=10 ewes; 12 rams), RES (n=13 ewes; 21 rams), and OVER (n =16 ewes; 15 rams), respectively. Blood samples were collected from offspring at d0, 7, 14, 58, 210, and 252 of age and plasma TC, plasma TG, and serum leptin were analyzed with commercial kits. Concentrations of TG were greater in rams than ewes (P=0.029). Leptin was greater (P&lt; 0.0001) in ewes than rams at d30 and 36, and greater in CON than RES and OVER at d252 (P=0.058). At d133±0.25 an intravenous glucose tolerance test was performed, and blood samples collected at -30, -15, 0, 2, 5, 10, 15, 30, 60, and 120 min relative to glucose infusion (0.25 g/kg body weight of a 50% dextrose solution). Glucose and insulin concentrations were determined using commercial kits. Glucose concentrations were greater at 5 and 15 min in ewes than rams (P≤0.04) and at 2 min, OVER were greater than CON and RES (P=0.03). Insulin concentrations were greater in rams than ewes between 5 and 15 min (P=0.0251). Insulin in RES rams tended to be greater than OVER and RES ewes between 5 and 10 min (P=0.06) and continued to be greater than RES ewes at 15 min (P=0.05). First-phase response of insulin tended to be greater in RES compared with CON and OVER (P=0.092). There were no differences detected in insulin:glucose (P=0.312). In conclusion, poor maternal nutrition negatively impacts key metabolic hormones in offspring thereby contributing to altered growth and metabolism.

PSV-A-6 Poor Maternal Nutrition During Gestation Decreases Shear Force and Alters Gene Expression Related to Fibrogenesis

To test the hypothesis that poor maternal nutrition during gestation would alter offspring muscle shear force and adipogenesis, fibrogenesis, and myogenesis mRNA expression, Dorset ewes (n=46) pregnant with twins were fed 100%, 60% or 140% of NRC requirements from d30±0.02 of gestation until parturition. Male offspring from CON (n=12), OVER (n=13), and RES (n=21) ewes were euthanized at d284±1.82 and longissimus muscle (LM) was harvested for shear force and gene expression. Vacuum-sealed LM steaks were aged for 10 d postmortem (4℃) and tenderness was measured using Warner-Bratzler shear force (WBSF) methodology. RNA was isolated from the LM to quantify mRNA expression of genes related to adipogenesis (fatty acid binding protein 4, CCAAT/enhancer-binding protein α, and peroxisome proliferator-activated receptor γ), fibrogenesis [collagen A1A (COLA1A), COL3A1, cystain-c, fibronectin (FN1), and lysyl oxidase (LOX)], and myogenesis [bone-morphogenic protein (BMP)-1, myostatin, myogenin, and myogenic differentiation 1). The WBSF decreased by 21% and 18% in OVER relative to CON (P=0.01) and RES (P=0.03), respectively, but CON and RES were not different (P=0.60). Expression of BMP1 was 1.5- and 1.8-fold greater in RES than OVER and CON, respectively (P≤0.03). Expression of FN1 was 1.6-fold greater in RES than OVER (P=0.02). Expression of COL1A1 was 2.2-fold greater in RES than CON (P=0.05) and was 1.6-fold greater in RES than OVER (P=0.07). Expression of LOX was decreased 37% in OVER compared with CON (P=0.04) and decreased 21% compared with RES (P=0.08). An effect of diet was not observed for other genes (P≥0.18). In summary, RES offspring had greater expression of genes related to fibrogenesis, but no observed difference in tenderness relative to CON. Over-feeding during gestation increased meat tenderness, which may be due to reduced collagen cross-linking by LOX.

PSXV-10 Poor Maternal Nutrition Impacts Mrna Expression of Epigenetic Factors in ram Offspring Liver

Poor maternal nutrition (over- and restricted-feeding) alters growth and metabolism in offspring after birth; however, the mechanisms are not well understood. Epigenetics, the heritable changes in gene expression without altering the DNA sequence, is a possible mechanism. We hypothesized that mRNA expression of epigenetic factors in livers of male offspring would be altered as a result of poor maternal diet during gestation. Multiparous Dorset ewes (n = 46) pregnant with twins were fed 100%, 60% or 140% of NRC requirements from d 30 ± 0.02 of gestation until parturition. Male offspring are referred to as CON (n=12), RES (n=21), and OVER (n=13), respectively. Ram lambs were euthanized at d 284±1.82, and liver tissue was immediately snap-frozen. RNA was isolated from liver and gene expression was quantified using real-time (RT)-PCR. Epigenetic factors of interest included DNA methyltransferases (DNMT; DNMT1, DNMT3B), ten eleven translocation enzyme 2 (TET2), lysine acetyltransferases (KAT; KAT1, KAT2B, KAT6A, KAT8), histone deacetylases (HDAC; HDAC1, HDAC2, HDAC3, HDAC4, HDAC5, HDAC6, HDAC8, HDAC11, sirtuin1), and histone methyltransferases [ASH1 like histone lysine methyltransferase (ASH1L), euchromatic histone lysine methyltransferase (EHMT)1, EHMT2, SET domain bifurcated histone lysine methyltransferase 2 (SETDB2)]. Gene expression of ASH1L and KAT6A were decreased in liver tissue of RES compared with OVER by 42.8% and 59.7%, respectively (P≤0.017). Gene expression of DNMT1 and HDAC3 were decreased in RES compared with CON by 38.3% and 35.0%, respectively (P≤0.045). Gene expression of EHMT1 and HDAC8 were increased in OVER compared with CON by 19.3% and 37.4%, respectively (P≤0.045). There were no differences detected in expression of other genes (P≥0.060). Thus, maternal diet affects hepatic mRNA expression of specific epigenetic factors which may contribute to altered metabolism and liver function. Further investigation is warranted to determine how epigenetic modifications impact offspring growth and metabolism long-term.

215 Awardee Talk: Astaxanthin Supplementation During Deconditioning and Reconditioning Periods Reduces Oxidative Stress in Circulation in Polo Ponies

Oxidative status is impacted by fitness and dietary nutrients, such as antioxidants. We hypothesized that astaxanthin (ASTX) supplementation would improve oxidative status in the circulation and muscle in response to exercise following deconditioning and reconditioning in horses. Twelve conditioned polo ponies (14.8 ± 1.7 yr) were assigned to control (CON; n = 6) or astaxanthin supplemented (ASTX; n = 6; 75 mg ASTX daily) groups. Horses performed 26 min submaximal exercise tests (SET) followed by 30 min of recovery while in condition (SET1), after 16 wk of deconditioning (SET2), and after 16 wk of reconditioning (SET3). Blood samples were collected 30 min before and 0, 15, 30, and 60 min after each SET. Semitendinosus muscle biopsies were collected 2 wk before and 2 hr after each SET. Using commercially available kits, plasma and muscle superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities and plasma malondialdehyde (MDA) concentrations were determined. At SET2, ASTX had 116% greater plasma SOD activities than CON (P=0.001). Both treatment groups increased from SET2 to SET3 (P&lt; 0.001), but there were no treatment effects at SET3 (P=0.788). At SET2, plasma GPX activities were 49.3% greater in ASTX than CON (P=0.012), and ASTX tended to be 21.2% greater than CON at SET3 (P=0.096). Plasma MDA concentrations were 22.2% greater in CON than ASTX at SET2 (P=0.034), but not at SET1 or SET3 (P≥0.449). There were no detectable differences in muscle SOD or GPX activities 2 wk before or 2 hr after any SET (P≥0.309). In conclusion, ASTX supplementation maintained circulating antioxidant capacity and minimized oxidant activities during deconditioning, reducing oxidative stress in response to the SET in the circulation but not in the skeletal muscle. This may enable horses to adjust to strenuous exercise more efficiently, improving athletic performance, especially when they are re-introduced to exercise after deconditioning.

PSIII-24 Poor gestational nutrition impacts sheep offspring growth but not feed efficiency

The objective was to determine the effects of poor maternal nutrition during gestation on growth and feed efficiency of offspring. We hypothesized that body weights (BW) would decrease and residual feed intake (RFI) would increase (reduced feed efficiency) in offspring of restricted- and over-fed ewes. Forty-six multiparous Dorset ewes pregnant with twins were fed 100%, 60% or 140% of NRC requirements from d 30 of gestation until parturition. Offspring are referred to as CON (n = 10 ewes; 12 rams), RES (n = 13 ewes; 21 rams), and OVER (n = 16 ewes; 13 rams), respectively. Lamb BW were measured weekly from birth to d 28 and biweekly until d 252 of age. Starting at d 167±13.6, daily intake of a complete pelleted feed was recorded using a Super SmartFeed (C-lock Inc., Rapid City, SD) over a 77 d- feeding period. Average BW were taken two days before, at mid-point, and two days after the feeding trial period and RFI was calculated for each animal. Rams were euthanized at d 284±12 and body morphometrics, loin eye area (LEA), back fat thickness, and organ weights were collected. From birth to d 252, ram lambs were 5.4 kg heavier (P &lt; 0.001) than ewe lambs. Control ewe lambs were 4.3 kg heavier than RES and OVER (P &lt; 0.05) from birth to 9 months and CON rams were 4.7 kg heavier (P &lt; 0.01) than RES. Rams (-0.17) were more efficient than ewes (0.23; P &lt; 0.01); however, no dietary treatment difference was observed (P ≥ 0.57). No differences in muscle mass, LEA, and adipose deposition were observed (P ≥ 0.41). These data indicate that poor maternal diet during gestation impacts offspring growth but not RFI. Further investigation is warranted to determine if differences in BW are a result of metabolic alterations impacted by poor maternal nutrition during gestation.

500 Late-Breaking: Heart Rate During Exercise Is Positively Correlated with State IV Mitochondrial Respiration in the Equine Skeletal Muscle

Mitochondria are critical for oxidative phosphorylation in skeletal muscle, especially in athletic species such as the horse. Mitochondrial respiration increases with physical exercise, but the relationship between mitochondrial respiration and cardiovascular functions are not well described in the horse. The objective of this study was to determine if there is a relationship between heart rate (HR) during and after submaximal exercise tests (SETs) and skeletal muscle mitochondrial respiration in polo ponies. We hypothesized that horses with greater maximum HR and average HR during the exercise tests would have greater mitochondrial respiration in skeletal muscle. Twelve fit polo ponies (14.8 ± 1.7 years old, 10 mares and 2 geldings) were equipped with Polar equine heart rate monitors (Polar Electro Inc., Lake Success, NY) and underwent 26-minute SETs designed to mimic a polo chukker followed by a 30-minute recovery period. Muscle biopsy samples from the semitendinosus muscle were taken 2 weeks prior to the SET to determine mitochondrial oxygen consumption using the Oroboros O2k high-resolution respirometer (Oroboros Instruments, Innsbruck, Austria). Data were analyzed using the PROC CORR procedure (SAS Inst. Inc., Cary, NC). Correlations were considered strong at r &gt; 0.6 and significant at P &lt; 0.05. Maximum HR during SET and state IV respiration were positively correlated (P = 0.02, r = 0.68). Average HR during SET and state IV respiration were also positively correlated (P = 0.01, r = 0.72). However, correlations between maximum and average HR and state III respiration were not as strong (P ≥ 0.05, r &lt; 0.6). These data suggest that state IV mitochondrial respiration (proton leak) in equine skeletal muscle may impact cardiac responses to high-intensity exercise. Horses with higher HR during exercise may have less efficient oxidative phosphorylation, resulting in earlier fatigue and/or greater formation of reactive oxygen species resulting from proton leak.

Apparent digestibility, fecal particle size, and mean retention time of reduced lignin alfalfa hay fed to horses

Reduced lignin alfalfa (Medicago sativa L.) has the potential to provide a higher-quality forage source for livestock by improving forage digestibility. This study was conducted to evaluate apparent digestibility when feeding reduced lignin and nonreduced lignin alfalfa hay to adult horses, and to examine mean fecal particle size (MFPS) and mean retention time (MRT) between alfalfa forage types. In 2017, reduced lignin ("54HVX41") and nonreduced lignin ("WL355.RR") alfalfa hay was harvested in Minnesota at the late-bud stage. Alfalfa hays were similar in crude protein (CP; 199 g/kg), neutral detergent fiber (NDF; 433 g/kg), and digestible energy (2.4 Mcal/kg). Acid detergent lignin concentrations were lower for reduced lignin alfalfa hay (74 g/kg) compared to nonreduced lignin alfalfa hay (81 g/kg). Dietary treatments were fed to six adult, stock-type horses in a crossover study. Experimental periods consisted of a 9-d dietary adaptation phase followed by a 5-d total fecal collection phase, during which horses were housed in individual boxstalls and manure was removed on a continuous 24-h basis. At 12-h intervals, feces were thoroughly mixed, subsampled in duplicate, and used for apparent digestibility and MFPS analysis. On day 2 of the fecal collection phase, horses were fed two indigestible markers, cobalt (Co) and ytterbium (Yb), which were fed as Co-ethylenediaminetetraacetic acid and Yb-labeled NDF residue, respectively. Additional fecal samples were taken at 2-h intervals following marker dosing until 96-h post-dosing to evaluate digesta MRT. Data were analyzed using the MIXED procedure of SAS, with statistical significance set at P ≤0.05. Dietary treatment (i.e., alfalfa hay type) was included as a fixed effect, while experimental period and horse were considered random effects. Dietary treatments were similar in dry matter intake (1.6% bodyweight) and time to consumption (7.6 h). Apparent dry matter digestibility (DMD) was greater for reduced lignin alfalfa (64.4%) compared to nonreduced lignin alfalfa (61.7%). Apparent CP and NDF digestibility did not differ between dietary treatments, averaging 78% and 45%, respectively. Dietary treatments were similar in MFPS (0.89 mm) and MRT for both liquid (23.7 h) and solid (27.4 h) phase material. These results indicate an improvement in DMD for reduced lignin alfalfa hay when fed to adult horses, with no change in forage consumption, fecal particle size, or digesta retention time.

Forage quality and beef cow preference is affected by wrap type of conventional and reduced-lignin alfalfa round bales stored outdoors

Storing hay outdoors can result in detrimental changes in forage quality. Additionally, alfalfa (Medicago sativa L.) cultivar may influence dry matter intake (DMI) and hay waste when feeding livestock. The objectives were to determine the effects of conventional or reduced-lignin alfalfa round bales stored outdoors and wrapped with plastic twine, net wrap, or B-Wrap on forage quality, beef cow preference, and hay waste. Round bales made from reduced-lignin (n = 12) or conventional (n = 12) alfalfa cultivars were baled and stored outdoors for 16 mo. Within each cultivar, four bale replicates were bound with plastic twine, net wrap, or B-Wrap. After storage, bales were fed in a switchback design with period confounded with alfalfa cultivar to 18 lactating Angus cows (Bos Taurus L.). The pairs had ad libitum access to three round-bale feeders where bales of each wrap type were placed for eight 48 h periods. Position of round bale wrap type was rotated according to a Latin Square arrangement. Bales were weighed and waste surrounding each feeder was collected at 24 and 48 h to calculate DMI and hay waste. Statistical significance was set at P < 0.05. Alfalfa cultivar did not impact any of the response variables (P > 0.05). At feeding, round bales wrapped in net wrap had greater (P < 0.015) moisture content (16.4%) compared with those wrapped with B-Wrap (12.8%). Neutral detergent fiber was lower (P = 0.03) in bales wrapped in B-Wrap (46%) compared with twine-tied bales (49%) while net wrapped bales were not different. Total digestible nutrients (P = 0.02), and relative feed value (P = 0.04) were lower in twine-tied bales compared with B-Wrap while net wrapped bales were not different. Twine (7.1 × 10⁶ colony forming units [CFU]/g) and net wrap (4.7 × 10⁶ CFU/g) bales had greater (P < 0.0001) mold counts than B-Wrap bales (4.8 × 10⁴ CFU/g), while concentrations of other forage components and yeast counts were not different among wrap types (P > 0.05). Total DMI, and DMI during the first 24 h, were greater (P ≤ 0.032) for B-Wrap bales compared to twine-tied bales indicating preference for hay wrapped in B-Wrap; net wrapped bales were not different. Dry matter intake in the first 24 h was negatively associated with the mold count (r = -0.52; P = 0.02), and hay waste was not affected by wrap type (P > 0.05). These results confirm that wrap type affected forage quality and mold counts, which in turn influenced beef cattle preference of round bales stored outdoors.