Effect of feeding method on nutrient utilization and cow performance in limit-fed cow-calf systems.

Delivery of limit-fed, complete rations requires significant capital investment, and creates logistical challenges for producers. Deconstruction and separate delivery of roughage and concentrate portions of diets may decrease feeding cost. Two experiments were conducted to evaluate the potential of separately limit-feeding roughage and concentrate. In Experiment 1, 4 ruminally cannulated steers (371 ± 12 kg bodyweight) were used in a 4 × 4 Latin square to evaluate the effects of time of concentrate delivery in deconstructed diets. Intake was restricted to 80% of predicted NEm requirements of a diet consisting of wheat straw (35%), cracked corn (29%), and distillers' grains (27%) formulated to contain 1.58 Mcal NEm/kg. Treatments were: concentrate fed 2 h prior to wheat straw (-2S), concentrate and wheat straw fed as total mixed ration (TMR), concentrate fed 2 h after wheat straw (+2S), and concentrate fed 12 h after wheat straw (+12S). In Experiment 2, 95 mid- to late-gestation cows (503 ± 151 kg) were used in a 112-d trial to evaluate feeding system on cow performance. Cows were assigned to 1 of 12 pens. Treatments were limit-fed the complete diet from Experiment 1 (TMR), fed roughage and concentrate portions of the deconstructed TMR 12 h apart (SEP), and ad libitum bermudagrass hay (HAY). Bodyweight (BW), BCS, and back fat measures were collected every 28 d. In Experiment 1, treatment did not affect DM or OM digestion (P ≥ 0.88), rate of particulate passage (P ≥ 0.55), or ruminal DM fill (P ≥ 0.19). Fill averaged 3.8 kg DM. Nadir of ruminal pH occurred 4-8 h after concentrate was delivered, but mean ruminal pH was not different among treatments (P = 0.22) ranging from 6.4 to 6.6 for +2S and 12S, respectively. In Experiment 2, treatment did not affect final BW (518 kg; P = 0.72) or final BCS (5.6; P = 0.67), but limit-fed strategies tended (P = 0.06) to have greater final RE (137.1, 98.9, and -14.6 Mcal for TMR, SEP, and HAY, respectively). Delivering forage and concentrate separately did not change digestion, and timing of concentrate delivery had only minor effects on ruminal fermentation. Limit-feeding a TMR or separate delivery of roughage and concentrate sustained cow performance compared to ad libitum hay consumption.

Effect of bioactive proteins on gait kinematics and systemic inflammatory markers in mature horses.

Twenty-seven mature Quarter horses were used in a randomized design to determine the effects of bioactive protein supplementation on gait kinematics and systemic inflammatory markers in a 34-d trial. Treatments consisted of oral doses of 230 g/d of pelleted supplements containing 0 g (CON; n = 9), 40 g of bioactive protein (40BP; n = 9; LIFELINE, APC, LLC, Ankeny, IA), and 80 g of bioactive protein (80BP; n = 9) daily. Horses were fed a commercial concentrate at 0.5% BW (as-fed) and received ad libitum coastal bermudagrass (Cynodon dactylon) hay daily. On day 33, horses consistent in exercise (CON, n = 6; 40BP, n = 8; 80BP, n = 7) participated in a trailering and riding challenge. Kinematic gait analysis was performed on day 0 for use as a covariate, and on day 14, 28, and 34 to allow for the determination of potential time and dosage effects. Video footage was collected and analyzed using gait analysis software (EquineTec, Monroe, GA) for the determination of stride length (SL) and range of motion (ROM). Blood was collected via jugular venipuncture on days 0, 14, 28, and 34 for determination of systemic expression of tumor necrosis factor (TNF)-α and IL-1ß. Data were analyzed using PROC MIXED of SAS. A trend towards treatment × time interaction was observed in ROM of the knee at the walk (P = 0.10), due to the increasing ROM for 40BP and 80BP as time increased and decreasing ROM for CON. A treatment × time interaction was observed (P < 0.01) for hock ROM at a walk resulting from CON and 80BP decreasing from day 14 to 28 with 40BP increasing, while from day 28 to 34 ROM at a walk decreased for 40BP and increased for 80BP. The main effect of treatment on hock ROM at the walk was quadratic (P < 0.01) and characterized by higher ROM values for 40BP compared to CON or 80BP. Dietary treatment lengthened (P = 0.04) SL of the hind limb at the walk for 40BP and 80BP compared to CON on both days 14 and 28. A significant treatment × time interaction was observed in the expression of IL-1ß (P < 0.01) and can be explained by lower concentrations of IL-1ß for 80BP on day 34 compared to the other treatments, with 40BP being intermediate and CON being the highest. Increased articular ROM with decreased expression of IL-1ß may indicate potential anti-inflammatory effects of 80 g/d of bioactive proteins.

Effect of maternal overnutrition on predisposition to insulin resistance in the foal: Maternal parameters and foal pancreas histoarchitecture.

Results from previous studies indicate that maternal overnutrition during late gestation predisposes foals to metabolic disease, however, specific mechanisms resulting in disease remain unknown. Quarter Horse mares (n = 16), were randomly assigned to dietary treatments, beginning on gestational day 235, and consisted of a control group (CON- diet meeting nutrient requirement; n = 8) or an overfed diet (HIGH; n = 8) where mares received an additional 40 % above CON. On gestational days 285 and 315, an intravenous glucose tolerance test (FSIGTT) was conducted. Following parturition, foals were separated from the mare, prohibited from nursing, and an FSIGTT was conducted at 2 h postpartum. Foals were immediately euthanized and tissues preserved for analyses. There was no effect of treatment on foal BW (P = 0.50), pancreas weight (P = 0.60), or FSIGTT area under the curve for glucose (P = 0.80) and insulin (P = 0.70). Colocalization of α-amylase to isolate pancreatic islets of Langerhans indicated increased islet number and size in foals from HIGH mares (P < 0.01). Immunofluoresent analysis of insulin, glucagon, and somatostatin indicate no difference in intensity of staining (P> 0.10). Foals exposed to overnutrition during peak fetal growth had altered pancreatic islet development that may lead to adult-onset metabolic disease.

Maternal nutrient restriction alters endocrine pancreas development in fetal heifers.

Maternal nutrient restriction during pregnancy alters fetal programming, which modifies the growth and health of the offspring in postnatal life. In cattle, nutrient restriction during pregnancy can be a result of environmental or economic factors, but little is known about how it alters the physiology of the fetus and affects future reproductive or growth efficiency. This study used female monozygotic twins, produced through in vitro fertilization and embryo splitting, to determine the effect of moderate maternal nutrient restriction on fetal development. Recipient Angus cross heifers pregnant with one twin were fed a diet meeting 100% National Research Council (NRC) total energy requirements (n = 4; control), whereas recipient heifers pregnant with the second twin were fed at 70% of NRC total energy requirements (n = 4; restricted) from gestational day (GD) 158 to GD 265 in Calan gate feeders. Recipient heifers were killed at GD 265. Change in maternal metabolic body weight was greater from zero in restricted heifers than controls (P < 0.05); restricted heifers lost weight during the nutrient restriction period. There was no difference in last rib back fat or rib eye area between groups (P > 0.10). There was no difference in fetal weight, uterine weight, or total placentome weight between groups (P > 0.10). The pancreas weight was reduced in restricted fetuses compared with control fetuses (P < 0.01), but there were no other differences in fetal organ weights (P > 0.10). Plasma insulin concentrations were reduced in restricted fetuses compared with controls (P < 0.01), but there was no effect of maternal diet on plasma glucose or glucagon concentrations in the fetus (P > 0.10). Histological analyses of the fetal pancreas revealed no differences in endocrine cell number or localization. Results indicate that a modest late gestation nutritional restriction impairs development of the fetal pancreas in the cow. Additional research will be needed to determine if these developmental changes lead to altered glucose and insulin homeostasis in the adult.

Responses in the rumen microbiome of Bos taurus and indicus steers fed a low-quality rice straw diet and supplemented protein.

Bos indicus typically perform better than Bos taurus when consuming a low-quality diet; however, the response to supplementation is generally greater in B. taurus. The underlying mechanisms supporting these responses have not been fully elucidated. Characterization of differences in rumen prokaryotic populations and their functional role in the two subspecies may provide additional insight. Ten cannulated steers (5 Angus and 5 Brahman) were used in concurrent 5 × 5 Latin squares. Animals were offered ad libitum access to rice straw (4.7% CP). Treatments consisted of an unsupplemented control diet and two levels (50 or 120 mg N/kg BW) of isonitrogenous supplements (30% CP), that were either high (H; 74%) or low (L; 26%) in undegradable intake protein. Rumen samples were collected at 0 and 4 h postfeeding and separated into liquid and solid fractions. Rumen bacterial taxa were sequenced utilizing a Roche 454 platform based on the 16s rRNA gene. At 97% sequence similarity, 97,826 operational taxonomic units were identified, which included 24 phyla, 108 families, and 255 genera. Analysis included SAS PROC mixed model, QIIME, and PICRUSt. Across all samples, Bacteroidetes and Firmicutes accounted for 65% and 28% of total bacterial abundance, respectively. The families Prevotellaceae (P = 0.05) and Ruminococcaceae (P = 0.004) and the genera Prevotellaceae (family; P = 0.003) within the phyla Bacteroidetes differed significantly in relative abundance with added protein when compared to the control. Consistent differences in the relative abundance of family and genus taxa between B. indicus and B. taurus suggest roles the symbiotic rumen microbiome may have in the capacity of B. indicus to utilize low-quality forage over a range of supplement types and levels including (Prevotella, Ruminococcus [family], Sphingobacteriaceae [family], Bacteroidales [order], Pontibacter, Bacteroides, Succiclasticum, Barnesiella, and Xylanibacter). Overall bacterial community diversity differences across parameters were limited. Rice straw is recalcitrant to bacterial digestion because of high levels of silica in the epidermis making this straw more resistant to bacterial attachment. Thus, this analysis represents the bacterial diversity and function of the rumen under conditions depleted CP, recalcitrant fiber matrix and restricted digestibility which appear to limit the microbial population to those capable of attaching and digesting complexed structural carbohydrates, resulting in reduced plasticity, and more evenness in diversity across parameters.

Glucose and acetate metabolism in bovine intramuscular and subcutaneous adipose tissues from steers infused with glucose, propionate, or acetate.

We hypothesized that abomasal infusion of glucose would promote de novo fatty acid biosynthesis from glucose in vitro in bovine intramuscular (i.m.) and subcutaneous (s.c.) adipose tissues to a greater extent than ruminal infusion of acetate, propionate, or glucose. Angus crossbred steers (n = 24), 22 mo of age, were fitted with ruminal cannulas, and steers were adapted to another corn/sorghum finishing diet over a 2-wk period while recovering from the placement of the cannulas. After the adaptation period, the steers were fed the second finishing diet at 130% of their voluntary intake and were infused with isocaloric amounts (3.76 Mcal/d) of glucose, propionate, or acetate for 35 d. Glucose was infused either into the rumen or into the abomasum, whereas propionate and acetate were infused into the rumen. Acetate infusion decreased DM and DE intakes (P < 0.05). The 5th to 8th longissimus muscle section was removed immediately and transported to the laboratory within 10 min post-exsanguination in 38 °C, oxygenated Krebs Henseleit buffer containing 5 mM glucose and 5 mM acetate. Intramuscular and s.c. adipose tissues were dissected from the muscle and incubated in vitro in 5 mM glucose plus 5 mM acetate (containing [U-14C]glucose or [1-14C]acetate). Lipid content was lower (P = 0.04) in i.m. adipose tissue of the acetate-infused steers than in the other treatment groups, and i.m. adipocytes from acetate-infused steers were smaller (P = 0.01) than those from propionate-infused steers. The rate of incorporation of acetate into glyceride-fatty acids (GFA) in i.m. and s.c. adipose tissues was greater (P < 0.03) in steers receiving ruminal or abomasal infusions of glucose than in adipose tissues from steers infused with acetate. The greatest rates of GFA synthesis were observed in s.c. adipose tissue from steers infused ruminally with propionate or abomasally infused with glucose (P < 0.001). In i.m. and s.c. adipose tissues, the proportion of acetyl units from acetate incorporated into GFA was greater in steers receiving glucose infusion in the rumen or abomasum than in steers receiving acetate or propionate infusion (P < 0.05). Contrary to our hypothesis, abomasal glucose infusion did not promote greater fatty acid biosynthesis from glucose in i.m. adipose tissue than ruminal glucose infusion. However, glucose infusion caused the greatest production of acetyl units from acetate in i.m. and s.c. adipose tissues.

Effect of monensin withdrawal on intake, digestion, and ruminal fermentation parameters by Bos taurus indicus and Bos taurus taurus steers consuming bermudagrass hay.

Effects of monensin withdrawal and cattle subspecies on the utilization of bermudagrass hay (14.3% CP, 72.3% NDF, and 36.9% ADF) were evaluated using ruminally cannulated steers (5 [BI] and 5 [BT]). Subspecies were concurrently subjected to a 2-period, 2-treatment crossover design. Treatments consisted of either 0 mg·steer·d-1 monensin with no previous monensin feeding (CON) or withdrawal from 200 mg·steer·d-1 monensin (MON) fed individually in 0.91 kg dried distillers' grains with solubles for 42 d. Withdrawal was evaluated for a 28-d period. Ruminal fluid was collected 2 h after feeding on d 0, 1, 4, 7, 14, and 21 after withdrawal for determination of pH, VFA, ruminal NH-N (RAN), rate of NH production, and CH production rate. Hay, ort, and fecal grab samples were collected d 23 through 28 after withdrawal for determination of intake and digestion. No subspecies × monensin, subspecies × day, or subspecies × monensin × day interactions were observed ( ≥ 0.11). An effect of day after monensin withdrawal was observed ( < 0.01) for total VFA concentration, with an increase following withdrawal followed by a decrease and then stabilization. Monensin × day after monensin withdrawal interactions ( ≤ 0.01) were observed for the acetate:propionate (A:P) ratio and molar percent of acetate and propionate. There was a decrease in molar percent of propionate between d 1 and 4 from 19.1 to 18.0; however, it remained greater ( ≤ 0.10) for MON than CON through d 7. Withdrawal increased molar percent of acetate from 68.3 to 69.8 between d 0 and 4 for MON steers. The A:P ratio was less ( ≤ 0.01) on d 0 for MON than for CON (3.4 vs. 4.0), but by d 4, it increased to 3.8 and was not different ( = 0.14) from CON. By d 14, no differences ( ≥ 0.88) remained for acetate, propionate, or the A:P ratio. After monensin withdrawal, monensin reduced ( < 0.01) RAN by 12.3% (2.09 vs. 1.83 m for CON and MON, respectively). Monensin withdrawal and cattle subspecies had no effect ( ≥ 0.23) on rate of NH production or CH production rate. Monensin withdrawal had no effect ( ≥ 0.45) on intake or digestibility parameters. Greater forage OM intake ( = 0.09; 21.2 vs. 19.2 g/kg BW) and OM digestibility ( < 0.01; 72.4 vs. 63.0%) resulted in greater ( < 0.01) total digestible OM intake (16.8 vs. 13.2 g/kg BW) in BT steers than in BI steers. These results suggest that BT steers are better able to utilize bermudagrass hay than BI steers. Upon monensin withdrawal, steers previously fed monensin continue to have a reduced A:P ratio for at least 7 d.

Effect of monensin inclusion on intake, digestion, and ruminal fermentation parameters by Bos taurus indicus and Bos taurus taurus steers consuming bermudagrass hay.

Effects of monensin inclusion and cattle subspecies on utilization of bermudagrass hay (13.7% CP, 77.3% NDF, and 38.8% ADF) were evaluated using ruminally cannulated steers (5 [BI] and 5 [BT]; 398 kg BW). Subspecies were concurrently subjected to a 2-period, 2-treatment crossover design. Treatments were 0 (CON) or 200 mg·steer·d monensin (MON) in 0.91 kg dried distillers' grains with solubles. Periods were 70 d in length: 20 d of adaptation, 22 d of sample collection, and 28 d for withdrawal of treatment. Steers were group housed during adaptation and moved to individual covered pens for sampling. Hay, ort, and fecal grab samples were collected d 21 through 25 for determination of intake and digestion. Ruminal fluid was collected with a suction strainer 0, 2, 4, 8, and 12 h after feeding on d 42 for pH, VFA, and ruminal NH-N (RAN) analysis. Additionally, at h 2, ruminal fluid and contents were collected for determination of rate of NH production and CH production rate. No subspecies × monensin interactions were observed ( ≥ 0.12). Monensin had no effect ( ≥ 0.16) on intake or digestibility parameters. No subspecies effect ( ≥ 0.11) was observed for forage OM intake, total OM intake, or OM digestion. Total digestible OM intake tended to be greater ( = 0.06) for BT steers than for BI steers (14.0 vs. 12.2 g/kg BW). There was an effect of hour after feeding ( ≤ 0.01) on pH, total VFA, acetate:propionate ratio, and molar percent acetate and propionate. Total VFA concentration was greater ( = 0.01) in CON steers than in MON steers (66.5 vs. 62.0 m). Monensin decreased molar percent acetate ( = 0.02) from 72.5 to 71.2% and increased molar percent propionate ( < 0.01) from 16.9 to 18.7%, resulting in a reduced ( < 0.01) acetate:propionate ratio (from 4.34 to 3.85). Although not significantly ( = 0.19), monensin numerically reduced the CH production rate by 15.8%. Greater ( = 0.07) CH production rate tended to be observed in BI steers than in BT steers (21.4 vs. 16.6 µmol CH·mL·h, respectively). Monensin had no effect ( ≥ 0.32) on pH, RAN, or rate of NH production. A subspecies × hour after feeding interaction was observed for RAN, with BT having greater RAN at h 0 and 4, whereas BI had greater RAN at h 2, 8, and 12. Overall, monensin decreased the acetate:propionate ratio and total VFA concentration but had no effect on forage utilization. steers consumed less digestible OM and had a greater CH production rate compared with BT steers, suggesting BT were better able to utilize the available forage resource than BI.

Effect of source and level of protein supplementation on rice straw utilization by Brahman steers.

Seven ruminally cannulated Brahman steers were used in a 7 × 4 incomplete block design to determine the effects of cottonseed meal (CSM; 43.9% CP, 82.9% RDP) or dried distillers' grains (DDG; 27.5% CP, 43.6% RDP) supplementation on rice straw utilization (47 g/kg CP and 681 g/kg NDF). Treatments consisted of a negative control receiving no supplement (control) and 3 levels (60, 120, and 180 mg N/kg BW) of either CSM or DDG. Periods were 14 d with 8 d for adaptation and 6 d for data collection. Steers had ad libitum access to rice straw and were fed supplements daily. Increased supplementation resulted in a linear increase ( ≤ 0.06) in forage OM intake from 13.5 g/kg BW by controls to 15.5 and 16.1 g/kg BW for 180 mg N/kg BW of DDG and CSM, respectively. No differences between sources were observed ( = 0.84). Total digestible OM intake was increased by supplementation (linear, < 0.01) from 6.9 g/kg BW (control) to 10.0 and 11.2 g/kg BW for 180 mg N/kg BW of CSM and DDG, respectively. A greater response was observed for DDG ( = 0.05) due to greater provision of supplement (g DM/d) to achieve isonitrogenous treatment levels. Total tract OM digestion tended to increase with DDG supplementation (linear, = 0.08) but not CSM supplementation ( = 0.19). Both supplements did not affect NDF digestion ( > 0.40) or calculated forage NDF digestibility ( > 0.40). Ruminal ammonia concentrations peaked 4 h after supplementation/feeding with the greatest concentration (4.0 m) observed for 180 mg N/kg BW of CSM and the lowest concentration at 4 h observed in the control (0.8 m). Provision of CSM resulted in a linear increase ( < 0.01) in average ruminal ammonia, in contrast to the quadratic response ( = 0.02) observed with DDG supplementation. Total VFA production linearly increased for both CSM and DDG supplementation ( = 0.09 and = 0.01, respectively). Protein supplements containing high and low levels of RDP were effective at improving intake and utilization of rice straw by Brahman steers.

Influence of short-term dietary starch inclusion on the equine cecal microbiome.

The objective of this study was to determine bacterial community profiles of the equine cecum in response to abrupt inclusion of varying levels of dietary starch. Seven cecally cannulated Quarter Horse geldings (497 to 580 kg) were used in a crossover design with two 28-d periods and a 28-d washout between each. Horses were randomly assigned to dietary treatments consisting of a commercial concentrate offered as fed at either 0.6 (low starch [LS]) or 1.2% BW (high starch [HS]) daily that was divided into 2 meals at 12-h intervals. Prior to the start of each period, horses were allowed ad libitum access to coastal bermudagrass () hay. Concentrate was fed on d 1 with no adaptation. Cecal fluid was collected on d 1 at h 0 and at 3, 6, 9, and 12 h relative to the initial concentrate meal on d 1. Additional samples were collected 6 h after feeding on d 2, 3, and 7 of each period. Cecal contents were used to determine pH and VFA concentrations and extract microbial DNA. The V4 through V6 region of 16S rRNA gene was amplified using PCR and sequenced on the Roche 454 FLX platform. Sequence analysis was performed with QIIME, and data were analyzed using the MIXED procedure of SAS. Cecal pH tended to decrease ( = 0.09) in horses fed HS in the first 12 h after the first concentrate meal and remained lower ( ≤ 0.05) the following 7 d. Total VFA were greater ( ≤ 0.05) in horses fed HS in the initial 12 h and 7 d after addition of concentrate. Species richness determined using the Chao1 index was unchanged ( > 0.20) over the initial 12 h and decreased ( = 0.01) over 7 d for both treatments. Community diversity determined using the Shannon index tended to decrease ( = 0.06) over the 7 d. Relative abundances of Paraprevotellaceae were greater ( ≤ 0.05) in HS in the first 12 h. Over 7 d, relative abundances of Paraprevotellaceae, Veillonellaceae, and Succinivibrionaceae were greater ( ≤ 0.05) in HS compared with LS. Abrupt and short-term exposure to dietary starch does alter cecal fermentation and microbial community structure in horses, but the impact on horse health is unknown.

Impact of exercise on productivity, behavior, and immune functioning of weaned Bos indicus-cross calves housed in drylots.

The effects of 2 exercise regimes on cattle productivity, immune function, and behavior were evaluated against a control ( = 4 pens/treatment) using weaned -cross calves ( = 203) housed in drylots (16-18 calves/single sex pens). Three treatments were applied 3 times per week for 4 wk: 1) programmatic exercise (PRO), in which cattle and a stockperson walked in the alleyway behind their home pen for 20 min; 2) free exercise (FREE), in which cattle were moved into the drovers alley for 60 min, not exercised by a stockperson, and were allowed free access to their home pen and alleyway; and 3) control (CON), in which calves were removed from their home pen only for routine husbandry. Behavior observations were conducted on d -2 and -1 relative to treatment implementation (d 0) and on d 5, 6, 12, 13, 19, 20, 26, and 27. Instantaneous scan sampling was used to create behavioral profiles for cattle (posture: stand, lie, and walk; and behavior: feed, drink, and ruminate). Focal observations recorded the incidence of social behaviors (allogrooming, social play, and agonistic interactions) and animal-environment interactions (AEI; fencepost licking, rock eating, tongue rolling, and cross-suckling). Body weights, exit velocities, and antibody titers to a bovine viral diarrhea virus type 1b vaccine were measured on d -10, 10, and 28. A linear mixed model (PROC MIXED) was used to evaluate the impact of exercise treatment, sex, time, and their interactions on cattle behavior, health, and productivity. Statistical differences were not observed ( = 0.11) for overall ADG among cattle receiving FREE (1.00 kg ± 0.04) PRO (0.85 kg ± 0.04), or CON (0.86 kg ± 0.05) exercise treatments. Allogrooming ( = 0.05), lying ( < 0. 01), AEI ( < 0.01), rumination ( < 0.01), and agonistic interactions ( < 0.01) increased over time. Comfort-related behaviors (e.g., lying, rumination) increased over the evaluation period, suggesting that calves became acclimated to the environment. Exercise did not alter behaviors or vaccine response and did not reduce the performance of production-critical (e.g., feeding, resting, ruminating) behaviors.

The influence of taste in willingness-to-pay valuations of sirloin steaks from postextraction algal residue-fed cattle.

Consumer preferences and willingness-to-pay (WTP) for beef sirloin steaks with differing production, physical, and credence attributes related to the use of postextraction algal residue (PEAR), a novel feed ingredient, were estimated. Ninety-six consumers participated in a sensory tasting panel before completing a choice set survey; 127 consumers completed only the choice set survey without sampling products. Steaks from grain- and PEAR-fed steers had similar Warner-Bratzler shear force (WBSF) scores (1.89 kg and 2.01 kg, respectively; = 0.77) and had lower WBSF scores than steaks from grass-fed steers (3.37 kg; < 0.05). Eicosapentaenoic acid (20:5) was not different among steaks from grain- and PEAR-fed steers ( = 0.39) but was greater compared with steaks from grass-fed cattle ( ≤ 0.03). Panelists in the sensory portion of the study evaluated beef samples for like/dislike of overall sample, overall flavor, beefy flavor, and juiciness. Panelist rating of overall like, overall flavor like, and beefy flavor like were not different between the PEAR- and grain-fed treatments ( > 0.26). Panelists rated the juiciness like/dislike of steaks from PEAR-fed cattle the highest ( < 0.01) among the 3 samples. Sensory tasting of the products was observed to alter the preferences of consumers. Consumers who completed only the survey negatively perceived beef from PEAR-fed cattle compared with beef from grain-fed cattle, with a WTP discount of -US$1.17/kg. However, with sensory tasting, the WTP for beef from PEAR-fed cattle was not discounted relative to beef from grain-fed cattle ( = 0.21). The nontasting consumers had much higher stated WTP values for credence attributes. Factors that influence the eating experience (tenderness and quality grade) dominated as the most important attributes on WTP among the tasting group. The use of no hormones and no antibiotics in production had a premium of $2.34/kg among the nontasting group, but with tasting, the premium was $1.19/kg. If PEAR-fed beef came to market, there would be no need to differentiate it from grain-fed beef unless retailers wanted to market it as a differentiated product. If it were marketed as a differentiated product, retailers would need to hold promotional tastings to change consumer's preconceived notions about the product.

Effect of postextraction algal residue supplementation on the ruminal microbiome of steers consuming low-quality forage.

Cattle consuming low-quality forages (LQF) require protein supplementation to increase forage utilization via ruminal fermentation. Biofuel production from algal biomass results in large quantities of postextraction algal residue (PEAR), which has the potential to elicit LQF utilization responses similar to cottonseed meal (CSM); however, its effect on ruminal bacterial communities is unknown. Five ruminally and duodenally cannulated Angus steers in a 5 × 5 Latin square had ad libitum access to oat straw diets. Treatments were infused ruminally and consisted of an unsupplemented control; PEAR at 50, 100, and 150 mg N/kg BW; and CSM at 100 mg N/kg BW. Ruminal samples were collected 4 h after supplementation on d 14 of each period and separated into solid and liquid fractions. Each sample was extracted for genomic DNA, PCR amplified for the V4 to V6 region of the 16S rRNA, sequenced on the 454 Roche pyrosequencing platform, and analyzed using the QIIME pipeline. Weighted UniFrac analysis and Morisita-Horn index demonstrated different community composition between liquid and solid fractions. Measures of richness including observed operational taxonomic units (OTU) and abundance coverage estimator metric decreased with greater PEAR provision (P ≤ 0.09). There were 42 core microbiome OTU observed in all solid fraction samples while the liquid fraction samples contained 30 core OTU. Bacteroidetes was the predominant phylum followed by Firmicutes in both fractions, which together characterized more than 90% of sequences. Relative abundance of Firmicutes increased with PEAR supplementation in the liquid fraction (linear, P = 0.02). Among Firmicutes, Lachnospiraceae, Ruminococcaceae, and Clostridiaceae families increased in the liquid fraction with greater PEAR supplementation (linear, P ≤ 0.03). Prevotella represented over 25% of sequences in all treatments, and relative abundance decreased in the solid fraction with increasing PEAR provision (linear, P = 0.01). Fibrobacter and Treponema decreased in the liquid fraction with increasing PEAR (linear, P < 0.10). Results suggest PEAR supplementation increased forage utilization by increasing members of Firmicutes within the liquid fraction of the rumen microbiome.

Effect of increasing amounts of postextraction algal residue on straw utilization in steers.

Algal biomass has been identified as a third-generation biofuel. Significant quantities of the coproduct postextraction algal residue (PEAR) remain after lipid extraction. After extraction, PEAR is concentrated in protein (17.9% CP on a DM basis and 32.5% CP on an ash-free basis), suggesting it may be an alternative to cottonseed meal (CSM) as a protein supplement. Our objectives were to determine the optimal level of PEAR supplementation to steers consuming straw and to compare the effects of PEAR supplementation on straw utilization and N metabolism with an isonitrogenous level of CSM. Five steers (198.2 ± 6.1 kg of BW), in a 5 × 5 Latin square, had ad libitum access to oat straw (80% NDF and 4.5% CP on a DM basis). Treatments were infused ruminally once daily and included no supplemental protein (CON); PEAR at 50, 100, and 150 mg N/kg BW; and CSM at 100 mg N/kg BW. Provision of PEAR increased total digestible OM intake (TDOMI) quadratically (P = 0.01) from 0.9 (CON) to 1.6 kg/d (100 mg N/kg BW of PEAR). Organic matter digestibility (OMD) increased quadratically (P < 0.01) with supplementation and was maximized (55% OMD) at 50 mg N/kg BW of PEAR. At isonitrogenous levels of PEAR and CSM, TDOMI was similar (P = 0.13) as was OMD (P = 0.50). Negative N balance was observed for all treatments except PEAR provided at 100 or 150 mg of N/kg BW. Nitrogen balance was quadratic (P < 0.01) with the greatest retention (1.84 g N/d) occurring at 100 mg N/kg BW of PEAR. There were no differences (P ≥ 0.22) between isonitrogenous PEAR and CSM supplementation in measurements of ruminal ammonia or VFA concentrations. Straw utilization was maximized when PEAR was provided at 100 mg N/kg BW. Our observations suggest cattle provided PEAR utilize straw in a manner similar to those supplemented CSM, indicating PEAR has potential to substitute for CSM as a protein supplement in forage-based operations.

Longitudinal shifts in bacterial diversity and fermentation pattern in the rumen of steers grazing wheat pasture.

Grazing steers on winter wheat forage is routinely practiced in the Southern Great Plains of the US. Here, we investigated the dynamics in bacterial populations of both solid and liquid ruminal fractions of steers grazing on maturing wheat forage of changing nutritive quality. The relationship between bacterial diversity and fermentation parameters in the liquid fraction was also investigated. During the first 28 days, the wheat was in a vegetative phase with a relatively high crude protein content (CP; 21%), which led to the incidence of mild cases of frothy bloat among steers. Rumen samples were collected on days 14, 28, 56 and 76, separated into solid and liquid fractions and analyzed for bacterial diversity using 16S pyrotag technology. The predominant phyla identified were Bacteroidetes (59-77%) and Firmicutes (20-33%) across both ruminal fractions. Very few differences were observed in the rumen bacterial communities within solid and liquid fractions on day 14. However, by day 28, the relatively high CP content complemented a distinct bacterial and chemical composition of the rumen fluid that was characterized by a higher ratio (4:1) of Bacteroidetes:Firmicutes and a corresponding lower acetate:propionate (3:1) ratio. Further, a greater accumulation of biofilm (mucopolysaccharide complex) on day 28 was strongly associated with the abundance of Firmicutes lineages such as Clostridium, Ruminococcus, Oscillospira and Moryella (P<0.05) in the fiber fraction. Such changes were diminished as the CP concentration declined over the course of the study. The abundance of Firmicutes was noticeable by 76 d in both fractions which signifies the development of a core microbiome associated with digestion of a more recalcitrant fiber in the mature wheat. This study demonstrates dynamics in the rumen microbiome and their association with fermentation activity in the rumen of steers during the vegetative (bloat-prone) and reproductive stages of wheat forage.

Influence of maternal plane of nutrition on mares and their foals: determination of mare performance and voluntary dry matter intake during late pregnancy using a dual-marker system.

Thirty pregnant mares (538 to 695 kg BW; 4 to 19 yr of age) were used to evaluate the effects of plane of nutrition on DMI of hay and mare performance (BW, BCS, and rump fat) during the last third of pregnancy. Mares were divided into 4 blocks by their expected foaling date and randomly assigned within block to either a hay or concentrate plus hay diet (concentrate fed at 0.75% BW, as-fed basis) with 15 mares per treatment. Treatments began 110 d before expected foaling date (230 d of gestation) and terminated at parturition. Mares were housed by block and allowed ad libitum access to coastal Bermuda grass (C. dactylon) hay, and concentrate-supplemented mares were fed twice daily in individual stalls. Performance variables were recorded every 14 d, with the last measurements obtained before foaling being considered a prepartum measurement. To evaluate DMI of hay, a dual-marker system was used at 9, 10, and 11 mo of gestation. Titanium dioxide was dosed at 10 g for 14 d. Fecal grab samples were obtained on the last 4 d twice daily via rectal palpation at 12-h intervals with times advancing 3 h each day to account for diurnal variation and to ultimately represent a 24-h period. Fecal samples were analyzed for TiO2 using a colorimetric procedure. Fecal, concentrate, and hay samples were also analyzed for acid detergent insoluble ash. Treatment tended to influence prepartum BW (P = 0.09) and affected prepartum BCS (P < 0.01) and rump fat (P = 0.01), with hay-fed mares having decreased BW and BCS from d 0 (beginning of feeding trial or d 230 of gestation) until parturition, whereas mares fed concentrate gained BW and BCS (P < 0.01). Mares fed only hay consumed 2.3% BW of forage compared with 1.8% BW for concentrate-fed mares (P < 0.01). Regardless of treatment, month of gestation influenced forage intake (P < 0.06), with mares consuming less during the 10th month of gestation and more in the 11th month (1.9% and 2.2% BW, respectively). These data indicate that the altered plane of nutrition of mares in late gestation influenced mare performance. Furthermore, DMI of hay was influenced by both diet and month of gestation. Continued research investigating manipulation of maternal nutrition and its effects on DMI would be beneficial to completely understand the relationships of these observations.

Effects of a slow-release urea product on performance, carcass characteristics, and nitrogen balance of steers fed steam-flaked corn.

Two experiments were conducted to examine the impact of source, urea (U) or Optigen II (OP), and level of dietary NPN on performance (Exp.1) and N balance (Exp. 2) of growing cattle. Sixty Angus crossbred steers (initial BW = 353 ± 13.9 kg) were used to evaluate performance, and fed 1 of 3 steam-flaked corn based diets: U (U(1.2), 1.2% NPN), OP (OP(1.3), 1.3% NPN), or OP without cottonseed meal (OP(3.1), 3.1% NPN). U(1.2)and OP(1.3) contained cottonseed meal and NPN as CP sources, whereas OP(3.1) contained only NPN. For Exp. 1, steers were blocked by postweaning BW and assigned to treatment (TRT) and pen within block. Body weight was collected every 14 d during the 105-d trial. Six steers from each TRT were selected based on residual feed intake (RFI) and harvested. Carcass and organ measurements were obtained. Cumulative animal performance was evaluated in 3 periods (0 to 35, 0 to 70, and 0 to 105 d) using a mixed coefficient model with initial BW as a covariate. For Exp. 2, 5 ruminally cannulated Holstein steers in a 5 × 5 Latin square design were used to evaluate N balance. Steers were fed a steam-flaked corn based diet with either no NPN, 0.75% U or N equivalent OP, or 1.5% U or N equivalent OP. Intake was measured, and feed, orts, urine, and fecal samples were obtained and composited for each steer by period. Data were analyzed using a mixed coefficient model. Orthogonal contrasts were used to evaluate differences between OP and U, and high and low level of NPN. For Exp. 1, there were no differences (P > 0.10) in initial BW, final BW, ADG, or DMI among TRT for any of the periods. However, for period 1 steers on OP(3.1) had reduced F:G than U(1.2) (5.71 kg/kg vs. 7.39 kg/kg; P = 0.03), and steers fed OP(1.3) tended to have less F:G than those fed U(1.2) (6.07 kg/kg vs. 7.39 kg/kg; P = 0.07). In period 2, OP(3.1) had reduced F:G than U(1.2) (5.58 kg/kg vs. 6.56 kg/kg; P = 0.03), but did not differ from OP(1.3) (5.97). For Exp. 2, steers fed OP tended (P = 0.09) to have less apparent N absorption than those fed U. Apparent N absorption differed (P < 0.05) for level of NPN. There were no differences (P > 0.10) in intake or digestibility among source or level of NPN. No major differences (P > 0.10) on performance and carcass composition were observed between U and OP diets. Steers had better initial F:G (Period 1 and 2) when OP was used as the only source of feed N (OP(3.1)), suggesting that OP may replace true protein feeds in finishing cattle diets, minimizing feed use with no impact on carcass quality.

Influence of dietary methionine concentration on growth and nitrogen balance in weanling Quarter Horses.

Twenty-four Quarter Horse weanlings (120 ± 10 d) were blocked by age into 4 groups (n=6) for a 56-d trial to evaluate the influence of dietary Met concentration on growth and N balance. Weanling horses were housed by block and individually fed concentrates twice daily at 1.75% BW (as-fed basis). Weanling horses were randomly assigned to 1 of 4 concentrate treatments: basal (0.20 Met), basal + 0.03% Met (0.23 Met), basal + 0.07% Met (0.27 Met), and basal + 0.11% Met (0.31 Met). Diets were formulated to be isonitrogenous and isocaloric and contained equal amounts of Lys and Thr. Coastal bermudagrass hay (Cynodon dactylon) was individually fed at 0.75% BW (as-fed basis). Growth measurements, BW, rump fat, and plasma were obtained every 7 d. The final 4 d consisted of total collection of urine and feces. Feed, fecal, and urine samples were analyzed for N content, and N balance was calculated. Urine was analyzed for urea and ammonia concentrations. Plasma was analyzed for urea concentration. Grain, hay, and fecal samples were analyzed for nutrient composition. Data were analyzed using the PROC MIXED procedure of SAS. Linear, quadratic, and cubic effects were tested in the form of contrasts. There was no influence (P>0.25) of treatment on growth measurements, N balance, or urinary urea or ammonia. Intake of Lys and Thr did not differ (P>0.08) among treatments. Methionine intake increased as expected with increasing Met inclusion in the diet (P<0.01). Plasma urea N responded quadratically (P=0.04) to treatment. An unexpected peak in PUN was observed with 0.27 Met. The results indicate future studies that can ensure Met as the only dietary variable are necessary to better explain the Met requirements of weanling horses.

Methodology for concurrent determination of urea kinetics and the capture of recycled urea nitrogen by ruminal microbes in cattle.

We measured the incorporation of recycled urea-nitrogen (N) by ruminal microbes, using five ruminally and duodenally fistulated steers (237 kg) fed low-quality grass hay (47 g crude protein/kg dry matter (DM)). Three received 1 kg/day of soybean meal (SBM) and two received no supplemental protein (control). The experiment was 15 days long. Background enrichments of 15N were measured on day 9 and continuous jugular infusion of 0.12 g/day [15N15N]urea began on day 10. Daily samples of urine, feces, ruminal bacteria and duodenal digesta from days 10 through 14 were used to determine plateaus in 15N enrichment. Duodenal and bacterial samples collected on day 15 were used to measure duodenal N flows. Bacterial N flow was calculated as duodenal N flow multiplied by duodenal 15N enrichment divided by bacterial 15N enrichment. Bacterial N from recycled urea-N was calculated as bacterial N flow multiplied by bacterial 15N enrichment divided by urinary urea 15N enrichment. Urinary enrichment of [15N15N]urea plateaued within 24 h, whereas 14N15N urea plateaued within 48 h of [15N15N]urea infusion. Bacteria reached a plateau in 15N enrichment within 24 h and duodenal samples within 48 h. Urea production was 17.6 g of urea-N/day for control and 78.0 g/day for SBM. Gut entry was 0.99 g of urea-N/g of urea-N produced for control and 0.87 g/g for SBM. Incorporation of recycled N into microbial N was 9.0 g of N/day for control and 23.0 g/day for SBM. Recycled urea-N accounted for 0.33 g of N/g of microbial N at the duodenum for control and 0.27 g/g for SBM. Our methods allowed measurement of incorporation of recycled urea-N into ruminal microbial N.

Effect of frequency and amount of rumen-degradable intake protein supplementation on urea kinetics and microbial use of recycled urea in steers consuming low-quality forage.

We evaluated the effect of frequency and amount of rumen-degradable intake protein (DIP) on urea kinetics in steers consuming prairie hay. Five ruminally and duodenally fistulated steers (366 kg of BW) were used in a 5 x 5 Latin square and provided ad libitum access to low-quality prairie hay (4.7% CP). Casein was provided daily in amounts of 61 and 183 mg of N/kg of BW (61/d and 183/d) and every third day in amounts of 61, 183, and 549 mg of N/kg of BW per supplementation event (61/3d, 183/3d, and 549/3d). Periods were 18-d long with 9 d for adaptation and 9 d for collection. Steers were in metabolism crates for total collection of urine and feces. Jugular infusion of (15)N(15)N-urea followed by determination of urinary enrichment of (15)N(15)N-urea and (14)N(15)N-urea was used to determine urea kinetics. Treatment means were separated to evaluate the effects of increasing DIP supplementation and the effects of frequency at the low (61/d vs. 183/3d) and at the high (183/d vs. 549/3d) amounts of DIP provision. Forage OM and total digestible OM intakes were linearly (P < or = 0.05) increased by increasing DIP provision but were not affected by frequency of supplementation at either the low or high amounts. Production and gut entry of urea linearly (P < or = 0.006) increased with DIP provision and tended to be greater (P < or = 0.07) for 549/3d than 183/d but were not different between 61/d and 183/3d. Microbial N flow to the duodenum was linearly (P < 0.001) increased by increasing DIP provision. Additionally, 183/d resulted in greater (P = 0.05) microbial N flow than 549/3d. Incorporation of recycled urea-N into microbial N linearly (P = 0.04) increased with increasing DIP. Microbial incorporation of recycled urea-N was greater for 549/3d than 183/d, with 42 and 23% of microbial N coming from recycled urea-N, respectively. In contrast, there was no difference due to frequency in the incorporation of recycled urea-N by ruminal microbes at the low level of supplementation (i.e., 61/d vs. 183/3d). This study demonstrates that urea recycling plays a substantial role in the N supply to the rumen and to the animal, particularly in steers supplemented infrequently with high levels of protein.