Degradable Intake Protein Research Articles

134 Effect of Rumen Degradable Protein Intake on Performance, Carcass Quality, and Methane Emissions of Yearling Finishing Steers

Abstract The performance, economic, and environmental consequences of feeding rumen degradable protein (RDP) levels above and below calculated maximum energy-dependent microbial crude protein (MCP) synthesis potential are poorly understood. Yearling steers (n = 54; initial BW = 484.1 ± 26.03 kg) were assigned to one of two pens that each contained an automated head chamber system (GreenFeed; C-Lock Inc., Rapid City, SD) for individual measurement of enteric methane (CH4) emissions. Each steer was assigned to an individual feed bunk (Calan Gate; American Calan, Northwood, NH) and randomly assigned to one of three dietary treatments: low RDP intake (LRDPI; n = 8), neutral RDP intake (NRDPI; n = 8), or high RDP intake (HRDPI; n = 8) in a completely randomized design. Steers were transitioned to treatment diets utilizing a two-ration blend system for 20-day followed by an 80-day finishing period. Diets were formulated to provide cattle with similar metabolizable protein (MP) and net energy for gain (NEg) but different RDP supply. Diets were formulated to provide approximately 87% (LRDPI), 100% (NRDPI), or 113% (HRDPI) of calculated RDP requirements to maximize energy-allowable MCP-yield. Paired-day, unshrunk BW was collected on d 0, 50, and 80, and cattle were transported to a commercial abattoir for carcass data collection. Statistical analyses were conducted using Analysis of Variance in JMP Pro6.0 using the Fit Model procedure. Least-squares means differences were considered statistically significant if P < 0.05 and considered a tendency toward significant if 0.05 ≤ P < 0.15. Treatment rations provided approximately 94% (LRDPI), 106% (NRDPI), and 118% (HRDPI) of the RDP required to maximize energy-allowable MCP yield, respectively. Daily DMI was similar (P > 0.15) for HRDPI and NRDPI cattle, but LRDPI cattle tended (P = 0.06) to have less DMI than NRDPI cattle. Dietary treatment did not affect (P ≥ 0.32) ADG, feed conversion efficiency, ribeye area, marbling score or carcass yield grade. Yet, LRDPI cattle had lighter hot carcass weight (P < 0.05) and less subcutaneous fat thickness (P < 0.05) than NRDPI cattle, whereas HRDPI cattle were not different (P ≥ 0.15) from the other treatments. On average, LRDPI cattle tended to emit 7.0% more daily CH4 (g×d-1; P = 0.05) than both NRDPI and HRDPI. Moreover, the LRDPI treatment elicited a 14.7% and 18.1% increase in CH4-yield (g CH4×kg DMI-1; P < 0.01) and emission intensity (g CH4×kg ADG-1; P < 0.05) compared with the other treatments, respectively. These data indicate that limiting MCP-yield by restricting RDP intake may reduce subcutaneous fat thickness and carcass weight while increasing enteric CH4 emissions. These results reiterate the importance of meeting RDP requirements and suggest no performance or methane emission benefits of overfeeding RDP.

Dietary polymer-coated urea enhances the goats lactational performance, excretion of microbial purine derivatives and blood metabolites in the semi-arid zone of Iran

This study aimed to determine the effect of using different sources of nitrogen to supply part of degradable intake protein needs in lactating goat performance and its effect on excretion of microbial purine derivatives and blood metabolites. Thirty-two lactating Saanen goats (body weight 38.85 ± 2.14 kg and 1979 ± 0.25 g day-1 milk yield) were used in a one-way ANOVA completely randomized design. Goats were assigned to the following treatments for a 10-wk experimental period: 1) Control (canola meal as a nitrogen source); 2) Urea (0.5% urea); 3) Optigen (0.55% Optigen- Alltech. Inc., Lexington, KY) and 4) Polymer-Coated Urea (PCU- international patent number: A01K5/00, 0.7% PCU) based on dry mater intake. Non-protein nitrogen groups had a comparative effect (p > 0.05) between control and other treatments on milk composition, microbial protein synthesis and they affected on blood factors including urea, cholesterol, and ALT. Dry matter intake decreased (p > 0.05) in PCU, Optigen, Urea than Control goats. Synthesis of microbial protein in PCU goats was 22.5 g day-1 and it was greater (p > 0.05) than other treatments. Plasma cholesterol was increased in PCU and Optigen, whereas urea concentration was increased in Urea and Control goats. Milk production was higher in PCU than Urea and Control. Feed conversion ratio was improved (p > 0.05) in PCU and Optigen goats versus other treatments. This study demonstrated that polymer-coated urea can be utilized as a nitrogen source and improve goats milk performance.

Cottonseed characteristics related to beef cattle consumption: Protein degradability, digestibility, and gossypol content

Our objectives were to (1) evaluate effects of whole cottonseed (WCS) storage conditions on protein and digestibility characteristics and (2) characterize protein degradability, gossypol content, and seed characteristics of cotton ( Gossypium hirsutum L.) in the southern United States. Seed with 0% heat damage (NN), 50% heat damage (N/B), or 100% heat damage (BB) was analyzed for in situ digestibility and protein degradability in Exp. 1. In Exp. 2, seed from 88 cotton breeding lines was obtained from a public cotton breeding program and analyzed for CP, undegradable intake protein (UIP), degradable intake protein (DIP), gossypol concentrations, and seed size. In situ DM disappearance was greatest ( P < 0.001) for NN after 48 h, and N/B was greater ( P < 0.05) than BB. Cottonseed that was not burned had a greater ( P = 0.01) amount of N degradable at a definable rate (B fraction) than BB, and the undegradable fraction (C fraction) tended to be less ( P = 0.06) for NN than BB and N/B. Cotton breeding lines had a mean CP value similar to those reported by the NASEM (2016), whereas DIP, UIP, and gossypol values had greater variability than CP in the present study. Correlations between seed size and protein were low, but there was a positive correlation with free gossypol. Heat-damaged WCS has decreased DM disappearance and N disappearance. Characterization of DIP, UIP, and gossypol in cottonseed may provide baseline selection criteria for cotton breeding programs, as well as aid in ration formulation strategies. Measuring WCS quality can help cotton breeders, animal scientists, and livestock producers develop seed value and feed recommendations for use.

Ruminal undegradable protein enriched diet during late gestation of beef cows affects maternal metabolism and offspring’s skeletal muscle development

We aimed to investigate the impacts of ruminal undegradable protein (RUP) enriched diet during late gestation on performance of pregnant beef cows and skeletal muscle growth of the offspring. From 180d of gestation to parturition, a total of 31 Brahman pregnant cows were randomly assigned to one of the experimental treatments: High-RUP diet (H-RUP, n = 17), and control diet (CTRL, n = 14). Maternal results showed no differences (P > 0.05) in dry matter intake, and total digestible nutrients intake between treatments. However, crude protein intake and the RUP intake were greater (P < 0.01) in H-RUP, while CTRL group had greater (P < 0.01) rumen degradable protein intake. Cows from H-RUP group were heavier (P < 0.01) at parturition and had greater (P = 0.01) average daily gain. Blood levels of nitric oxide tended (P = 0.06) to be greater in H-RUP, while blood glucose levels were not altered (P > 0.60) by RUP-enriched diet. Blood aminoacidic profile showed greater (P = 0.02) concentrations of methionine in CTRL group, and greater (P < 0.01) concentrations of the branched chain amino acids in H-RUP cows. A greater (P = 0.04) number of muscle fibers were observed in the H-RUP offspring, while a tendency (P = 0.07) of greater muscle fiber diameter was observed in CTRL offspring. Gene expression analysis indicated higher (P < 0.01) expression of the satellite cells marker (PAX7) in CTRL offspring. In contrast, the expression of the markers of fibro-adipogenic progenitor cells (PDGFRα), and adipogenesis (ZFP423, PPARγ, C/EBPα) were higher in the skeletal muscle of H-RUP offspring. Consistently, at the protein level the greater abundance of ZFP423 (P = 0.03), and PPARγ (P = 0.01) were observed in H-RUP offspring. Moreover, the expression of the fibrogenic marker (TGFβ) was higher (P = 0.01) in H-RUP offspring. Our findings suggest that supplementing pregnant beef cows during late gestation may increase the availability of amino acids, responsible to maintain maternal body conditions and to change the skeletal muscle characteristics of the offspring. Since the resulting offspring from H-RUP treatment showed greater number of muscle fiber and an increase in the process of intramuscular adipogenesis our data suggest that a RUP-enriched diet for pregnant cows at late gestation may be beneficial for the achievement of better carcasses at slaughter. However, the feeding strategy showed no changes in the offspring’s performance during the growing phase.

Infrequent dietary supplementation feeding in beef cattle: animal responses and factors affecting its success

Abstract Infrequent supplementation (IS; i.e., feeding supplement to animals at frequency less than daily) as opposed to frequent (i.e., daily) could be used as a management tool to improve economic returns of extensive beef production systems by reducing costs associated with the delivery of supplement to cattle. However, previous reports on the effectiveness of IS on production responses in beef cattle are ambiguous and the factors affecting responses to IS by beef cattle are poorly known. The objective of this study was to summarise available data related to the success of IS in beef cattle fed a low quality diet. Additionally, we aimed to identify other potential factors, such as supplement type and composition, forage quality, supplemental degradable intake protein, breed of cattle and environment, which may influence the animal’s response to IS. The results of our study suggest that no single factor could fully explain the discrepancies among studies and, therefore, each of these factors should not be treated in isolation. Cattle maintained with IS appear to be more efficient using the urea recycling mechanism to maintain level of ruminal ammonia during the non-supplemental feeding days. Systematic approaches compiling all potential factors affecting responses of beef cattle to IS are required to determine the likelihood of success with IS for a given farming system.

Influence of Different Cutting Dates on Cornell Net Carbohydrate and Protein System (CNCPS) Parameters and the Fatty Acid Compositons of Caramba Hay (Lolium multiflorum cv. caramba)

The aim of the study was to determine the influence of different cutting dates on Cornell Net Carbohydrate and Protein System (CNCPS) parameters and the fatty acid (FAs) compositons of caramba hay (Lolium multiflorum cv caramba). The samples were taken from the five randomized plots at the three different cuts (first cut:before blossom, second cut:blossom 50%, and third cut:after blossom). The samples were analyzed including the crude protein (CP), ether extract (EE), CP fractions (A= NPN, B1= fast, B2= intermediate, B3= slow and C= not fermented and available for the animal), degradable intake protein (DIP), undegradable intake protein (UIP) and the FAs compositions (C14:0, C16:0, C18:0, C18:1, C18:2 and C18:3). The CP, EE and A1 fraction were negatively affected by the different cutting dates (P 0.05). A positive strong linear relation was found between the C18:3 and CP contents in caramba hay (R2= 0.769, P<0.001). The study showed that CP, soluble protein (A+B1 fraction) and C18:3 were significantly decreased, the other crude protein fractions (B2, B3 and C) and other major FAs (C16:0 and C18:2) were increased by growing stage.

Nitrogen Delivery Method and Monensin Effects on Productivity, Nutritive Value, and Botanical Composition of Grazed Annual Ryegrass Pasture

Nitrogen fertilization is a major input cost of forage production, and alternatives that maintain yield and nutritive value would be advantageous. A 3‐yr study was conducted to evaluate forage nutritive value and clover proportion when N fertilizer was replaced partially with interseeded clovers (Trifolium spp.) or protein supplements for stocker cattle grazing annual ryegrass (Lolium multiflorum Lam.). Nitrogen delivery methods with or without monensin included annual ryegrass fertilized with 112 kg N ha−1 in split application (NFERT), and other methods that received 56 kg N ha−1, including annual ryegrass interseeded with crimson clover (CC, Trifolium incarnatum L.) or arrowleaf clover (AC, Trifolium vesiculosum Savi), or grazing cattle supplemented with distillers dried grains plus solubles at a rate of 0.65% body weight daily (DDGS) or whole cottonseed (Gossypium hirsutum L.) at the rate of 0.65% body weight daily (WCS). Clover proportion was greater (P = 0.003) for CC than AC across all 3 yr of the study, and CC was more (P = 0.003) abundant when monensin was fed. Year affected forage in vitro true digestibility (IVTD, P &lt; 0.001) and crude protein (CP, P &lt; 0.001) concentration such that IVTD and CP were greatest in Year 3, intermediate in Year 2, and least in Year 1. Forage degradable intake protein (DIP) concentration was affected by N delivery method (P &lt; 0.001) and year (P &lt; 0.001) such that CC was less than NFERT, DDGS, WCS, and AC, and Year 1 was greatest, Year 2 was intermediate, and Year 3 was the least. Results are interpreted to mean that year affected forage nutritive value more than did N delivery method.

In situ ruminal degradation characteristics of dry matter and crude protein from dried corn, high-protein corn, and wheat distillers grains.

BackgroundThe continuing growth of the ethanol industry has generated large amounts of various distillers grains co-products. These are characterized by a wide variation in chemical composition and ruminal degradability. Therefore, their precise formulation in the ruminant diet requires the systematic evaluation of their degradation profiles in the rumen.MethodsThree distillers grains plus soluble co-products (DDGS) namely, corn DDGS, high-protein corn DDGS (HP-DDGS), and wheat DDGS, were subjected to an in situ trial to determine the degradation kinetics of the dry matter (DM) and crude protein (CP). Soybean meal (SBM), a feed with highly degradable protein in the rumen, was included as the fourth feed. The four feeds were incubated in duplicate at each time point in the rumen of three ruminally cannulated Hanwoo cattle for 1, 2, 4, 6, 8, 12, 24, and 48 h.ResultsWheat DDGS had the highest filterable and soluble A fraction of its DM (37.2 %), but the lowest degradable B (49.5 %; P < 0.001) and an undegradable C fraction (13.3 %; P < 0.001). The filterable and soluble A fraction of CP was greatest with wheat DDGS, intermediate with corn DDGS, and lowest with HP-DDGS and SBM; however, the undegradable C fraction of CP was the greatest with HP-DDGS (41.2 %), intermediate with corn DDGS (2.7 %), and lowest with wheat DDGS and SMB (average 4.3 %). The degradation rate of degradable B fraction (% h−1) was ranked from highest to lowest as follows for 1) DM: SBM (13.3), wheat DDGS (9.1), and corn DDGS and HP-DDGS (average 5.2); 2) CP: SBM (17.6), wheat DDGS (11.6), and corn DDGS and HP-DDGS (average 4.4). The in situ effective degradability of CP, assuming a passage rate of 0.06 h−1, was the highest (P < 0.001) for SBM (73.9 %) and wheat DDGS (71.2 %), intermediate for corn DDGS (42.5 %), and the lowest for HP-DDGS (28.6 %), which suggests that corn DDGS and HP-DDGS are a good source of undegraded intake protein for ruminants.ConclusionsThis study provided a comparative estimate of ruminal DM and CP degradation characteristics for three DDGS co-products and SBM, which might be useful for their inclusion in the diet according to the ruminally undegraded to degraded intake protein ratio.

Effect of slow-release urea inclusion in diets containing modified corn distillers grains on total tract digestibility and ruminal fermentation in feedlot cattle.

Ruminal degradable intake protein (DIP) deficit may result when cattle are fed diets containing a greater inclusion of processed corn grain and small to moderate inclusion of corn distillers grains (DG). This deficit may arise from greater proportions of rapidly fermentable carbohydrates and RUP in corn grain. Urea-derived N is 100% DIP; however, rates of degradation of carbohydrates and conventional urea (CU) may not match. Therefore, beneficial effects may result from the use of slow-release urea (SRU) sources over CU when added to DIP-deficient diets. An experiment was conducted to evaluate the effect of increasing DIP concentration through inclusion of 1 of 2 SRU sources or CU in DG-containing feedlot diets on ruminal fermentation and total tract digestibility. In addition, an in situ experiment was conducted to characterize N disappearance of urea sources from polyester bags. Four ruminally cannulated steers (initial BW = 588 ± 8 kg) were arranged in a 4 × 4 Latin square design and assigned randomly to 1 of 4 dietary treatments containing 0% (CON) or 0.6% urea in the form of CU (UREA) or SRU as Optigen II (polymer-encapsulated urea; OPTI) or NitroShure (lipid-encapsulated urea; NITRO), and 30% corn earlage, 20% modified corn DG with solubles, 7.8% corn silage, 4.3% dry supplement, and dry-rolled corn (DM basis). Dietary DIP was estimated at 6.6% and 8.3% for CON and urea-containing dietary treatments, respectively. Steers were fed ad libitum once daily. Differences in purine derivatives-to-creatinine (PDC) index between treatments were used as indicators of differences in microbial CP synthesis. Intake of OM, digestibility of OM, NDF, CP, and starch, ruminal pH, total VFA ruminal concentration, and PDC index were not affected by treatment ( ≥ 0.21). Concentration of ammonia-N noticeably peaked at 4 h after feed delivery for cattle fed UREA (treatment × time, = 0.06) and measured at least 5.5 mg/dL for any treatment and at any hour after feed delivery. During the first 12 h after incubation, N disappearance was greater for CU and NitroShure than Optigen II (urea source × time, < 0.01). Supplementing DIP through inclusion of CU or SRU did not affect feed intake, digestibility, or most of the ruminal fermentation parameters evaluated, which may relate to the lack of need of urea supplementation in the present experiment. More research is warranted to evaluate the use of SRU in DIP-deficient diets.

In vivo ruminal degradation characteristics and apparent digestibility of low-quality prairie hay for steers consuming monensin and Optimase.

Seven ruminally cannulated crossbred steers (BW = 720 ± 62 kg) were used in a randomized crossover design (4 periods, each 18 d) to evaluate in vivo rumen characteristics and apparent digestibility of steers consuming low-quality prairie hay and 1 of 4 isonitrogenous protein supplements. Treatments included 1) 40% CP (DM basis) cottonseed meal and wheat middlings-based supplement (Control), 2) a cottonseed meal and wheat middlings-based supplement with slow-release urea and a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) designed to replace 30% of plant-based CP provided in the Control (OPT), 3) the Control plus 0.40 mg∙kg BW∙d monensin (Rumensin 90; Elanco Animal Health, Greenfield, IN; MON), and 4) the OPT plus 0.40 mg∙kg BW∙d monensin (COMBO). Steers were allowed ad libitum access to prairie hay (5.0% CP and 76% NDF) and were provided each respective supplement at 0800 h daily at a rate of 1.0 g/kg of BW. Steers were adapted to diets for 10 d before sample collection. Beginning on d 11, DMI was measured and samples were collected to determine apparent digestibility. On d 15 of the 18-d period, rumen fluid was collected 10 times over a 24-h period. Forage DMI was greater ( ≤ 0.02) for steers consuming the OPT compared with steers consuming the MON or COMBO, although forage DMI was not different ( = 0.10) among steers consuming the Control compared with steers consuming the OPT, MON, or COMBO. Steers fed the MON and COMBO had lower ( ≤ 0.05) passage rate compared with steers fed the Control and the OPT. The MON-fed steers had lower ( = 0.01) ruminal pH and increased ( = 0.03) propionate as a percentage of total VFA production. A time × treatment ( = 0.01) interaction was observed for ruminal NH-N due to a rapid (0 to 1 h after feeding) increase followed by a quick (1 to 4 h after feeding) decline in NH-N by steers consuming the OPT and COMBO that was not observed for steers consuming all other treatments. Apparent digestibility of DM ( = 0.01) and NDF ( = 0.03) were improved for steers fed the COMBO supplement compared with steers consuming all other experimental supplements. This work suggests that the OPT may be an effective replacement for a portion of supplemental degradable intake protein in low-quality forage. Further research is necessary to determine if the combination of monensin and the Optimase consistently improves low-quality forage utilization.

Effect of direct-fed microbials on utilization of degradable intake protein in receiving steers

Kenney, N. M., Vanzant, E. S., Harmon, D. L. and McLeod, K. R. 2015. Effect of direct-fed microbials on utilization of degradable intake protein in receiving steers. Can. J. Anim. Sci. 95: 93–102. One hundred ninety-two crossbred beef steers (280±25 kg) were assigned to a 5×2 factorial; degradable intake protein (DIP; 80, 90, 100, 110, 120% of requirement) with and without a direct-fed microbial (DFM) primarily containing Lactobacillus acidophilus and Enterococcus faecium (109CFU steer−1d−1). Dry matter intake, morbidity, and immune response were not affected (P≥0.11). The first 28 d, average daily gain (ADG) did not differ with DIP in control, but increased in a cubic fashion with DFM (DIP×DFM; P=0.05). No differences (P≥0.25) in ADG occurred from days 29 to 56; however, there was a tendency (P=0.08) for a cubic increase in ADG with increasing DIP with DFM over 56 d. The first 28 d, growth efficiency did not differ across DIP levels in control but increased linearly with DFM (DIP×DFM; P=0.05). No differences (P≥0.21) in efficiency were observed from days 29 to 56 or overall. Without DFM, fecal pH decreased between days 7 and 14; however, with DFM there was no change in pH (DFM×time; P&lt;0.05). Performance response to DFM is dependent on DIP; however, DFM does not impact morbidity or humoral immune response.

The effects of degradable nitrogen level and slow release urea on nitrogen balance and urea kinetics in Holstein steers

The objective of this study was to compare nitrogen metabolism and urea kinetics between diets containing either rapidly degrading or slow degrading non-protein nitrogen (NPN) at varying levels of degradable intake protein (DIP). Treatments were slow release urea (Optigen®, Alltech, Inc.) fed at 1.01 and 1.14 and feed grade urea (UREA) fed at 0.89 and 1.00 of calculated DIP requirements. Eight Holstein steers (209 ±15kg) implanted with 28mg estradiol+200mg trenbolone acetate (Synovex Plus, Fort Dodge Animal Health, Fort Dodge, IA) were used in a replicated 4×4 Latin square. Experimental periods were 27 days, with 19 day adaptation followed by 7 day of urine and fecal collection and 1 day of blood sampling. Continuous (78h) intravenous infusion of 15N15N-urea allowed the estimation of systemic urea kinetics. Dry matter intake was not different between treatments (7.2kg/day). Increasing DIP had a tendency to increase dry matter digestibility (DMD) for both Urea and Optigen®. Urea had higher DMD than Optigen®. Increasing DIP increased urinary N output for both UREA and Optigen®, and increased N-retention at 1.14 Optigen®. Increasing DIP increased urea-N entry rate (UER) and urinary urea-N excretion (UUE) for both Optigen® and UREA. Gastrointestinal entry of urea-N, urea-N lost to feces and urea-N apparently used for anabolism were not different between treatments. Plasma urea concentration was greater in higher DIP diets and higher for Urea than Optigen® at 1.00 DIP. Therefore increasing DIP level will increase N-excretion related to higher urea production and excretion in urine but may also increase diet digestibility. Most changes in N metabolism were driven by N intake.

Effect of urea inclusion in diets containing corn dried distillers grains on feedlot cattle performance, carcass characteristics, ruminal fermentation, total tract digestibility, and purine derivatives-to-creatinine index.

Increased availability of rapidly fermentable carbohydrates and a great proportion of corn-derived CP in the diet may result in a degradable intake protein (DIP) deficit. Therefore, ruminal DIP deficit may result from high dietary inclusion of processed corn grain and small to moderate inclusion of corn distillers grains (DG). Two experiments were conducted to evaluate the effect of increasing dietary DIP concentration through the inclusion of urea on feedlot cattle performance, carcass characteristics, ruminal fermentation, total tract digestibility, and purine derivatives-to-creatinine (PDC) index. In Exp. 1, 42 steers (428 ± 5 kg initial BW) were assigned randomly to 1 of 3 diets containing (DM basis) 0 (control [CON]), 0.4 (low urea [LU]), or 0.6% urea (high urea [HU]) to provide 6.4, 7.5, or 8.0% dietary DIP, respectively, and 12% high-moisture corn (HMC), 20% corn dried DG with solubles (DDGS), 10% ryegrass haylage, 2.9% dry supplement, and dry-rolled corn (DRC). Steers were fed ad libitum once daily using a Calan gate system. Carcass-adjusted final BW and DMI were similar among treatments (P ≥ 0.58). Carcass-adjusted ADG was greater (P ≤ 0.04) for the HU diet compared with the LU and CON diets and was similar (P = 0.73) between the LU and CON diets. Carcass-adjusted G:F was greater (P = 0.03) for the HU diet compared with the LU diet, tended (P = 0.09) to be greater compared with the CON diet, and was similar (P = 0.61) between the LU and CON diets. Carcass characteristics were similar (P ≥ 0.34) among treatments. In Exp. 2, 4 ruminally cannulated steers (347 ± 18 kg initial BW) were randomly assigned to a replicated 2 × 2 Latin square design. Steers were fed the same CON or HU diet used in Exp. 1 ad libitum once daily. Differences in the PDC index were used as indicators of differences in microbial CP synthesis. Ruminal pH, OM intake, and starch and CP digestibility were not affected by treatment (P ≥ 0.13). Digestibility of OM and NDF and ruminal concentration of ammonia-N and total VFA were greater (P ≤ 0.04) for the HU diet compared with the CON diet. The PDC index was similar (P = 0.81) between treatments at 2 h before feed delivery: 4% lower and 14% greater for the HU diet compared with the CON diet at 4 and 10 h after feed delivery, respectively (P < 0.01). These results suggest that, due to limited DIP supplied by a DRC- and HMC-based feedlot diet containing 20% DDGS, urea supplementation resulted in improved ruminal fermentation and feed digestibility, which may explain the concurrently improved cattle performance.

Replacement of wheat bran with spineless cactus (Opuntia ficus indica Mill cv Gigante) and urea in the diets of Holstein x Gyr heifers.

The aim of this study was to evaluate the replacement effect of wheat bran with spineless cactus and urea in heifers. Twenty-four heifers with an average initial weight of 185 ± 13 kg were used in this experiment. Four levels of spineless cactus corrected with urea and ammonium sulfate (9:1) were studied: 0, 33, 66, and 100 % replacement with wheat bran. Samples of feed, orts, and feces were analyzed to estimate the intake and digestibility of dry matter (DM) and nutrients. Indigestible neutral detergent fiber was used as an internal marker. The experiment was conducted in a completely randomized design. Dry matter, neutral detergent fiber, and total digestible nutrient intake demonstrated a quadratic effect (P < 0.05). Rumen degradable protein intake increased linearly (P < 0.05). The maximum DM digestibility was estimated to be 0.67 with a 43 % replacement. Crude protein and NDF digestibility increased linearly (P < 0.05). The total body weight gain and average daily gain decreased linearly with the replacement. Thus, it is practical to replace wheat bran with spineless cactus containing urea and ammonium sulfate up to 66 % in sugar cane-based diets.

Influence of ruminal degradable intake protein restriction on characteristics of digestion and growth performance of feedlot cattle during the late finishing phase.

Two trials were conducted to evaluate the influence of supplemental urea withdrawal on characteristics of digestion (Trial 1) and growth performance (Trial 2) of feedlot cattle during the last 40 days on feed. Treatments consisted of a steam-flaked corn-based finishing diet supplemented with urea to provide urea fermentation potential (UFP) of 0, 0.6, and 1.2%. In Trial 1, six Holstein steers (160 ± 10 kg) with cannulas in the rumen and proximal duodenum were used in a replicated 3 × 3 Latin square experiment. Decreasing supplemental urea decreased (linear effect, P ≤ 0.05) ruminal OM digestion. This effect was mediated by decreases (linear effect, P ≤ 0.05) in ruminal digestibility of NDF and N. Passage of non-ammonia and microbial N (MN) to the small intestine decreased (linear effect, P = 0.04) with decreasing dietary urea level. Total tract digestion of OM (linear effect, P = 0.06), NDF (linear effect, P = 0.07), N (linear effect, P = 0.04) and dietary DE (linear effect, P = 0.05) decreased with decreasing urea level. Treatment effects on total tract starch digestion, although numerically small, likewise tended (linear effect, P = 0.11) to decrease with decreasing urea level. Decreased fiber digestion accounted for 51% of the variation in OM digestion. Ruminal pH was not affected by treatments averaging 5.82. Decreasing urea level decreased (linear effect, P ≤ 0.05) ruminal N-NH and blood urea nitrogen. In Trial 2, 90 crossbred steers (468 kg ± 8), were used in a 40 d feeding trial (5 steers/pen, 6 pens/ treatment) to evaluate treatment effects on final-phase growth performance. Decreasing urea level did not affect DMI, but decreased (linear effect, P ≤ 0.03) ADG, gain efficiency, and dietary NE. It is concluded that in addition to effects on metabolizable amino acid flow to the small intestine, depriving cattle of otherwise ruminally degradable N (RDP) during the late finishing phase may negatively impact site and extent of digestion of OM, depressing ADG, gain efficiency, and dietary NE.

Performance and ultrasound measurements of beef cattle fed diets based on whole corn or oats grains

This study intended to contrast dietary effects of whole grain oats versus corn included in rations with moderate roughage content on animal performance, beef ultrasound measurements, rumen and blood parameters. Ten Aberdeen Angus steers (203 kg) in individual pens were fed twice daily on either whole oats (OD) or corn (CD) based diets. Measurements were: DM intake (DMI), average daily gain (ADG), feed to gain ratio (F/G); back fat (BF) and rib eye area (RA); blood parameters. Four cannulated steers were used to study rumen pH, NH3-N and grain degradability. Rations dietary components were 55% grain, 30.1% barley straw, and 10.6% whole soybeans. Despite calculated higher ME supply (P = 0.0887) no differences were found for DMI, ADG, or F/G. Metabolizable protein intake (19.4%) was larger and degradable protein intake (43.3%) smaller for CD compared with OD (P < 0.01). The growth rate (cm2 d-1) for RA was 40% grater for OD, but larger BF deposition (P = 0.0787) was found for CD. Blood Mg was higher for OD (p = 0.0564), nevertheless other blood parameters remained unaffected. Rumen pH and NH3-N were not influenced by diet, variations were only observed within time periods. Rumen pH decreased linearly from 7.05 to 6.13 and 7.11 to 6.37 for OD and CD respectively (P < 0.05). Minimum NH3-N concentrations (mg dL-1) were reached 12 and 18 h after morning meal for OD (7.10) and CD (5.82) respectively. Rumen degradation was larger for oats than corn. Whole oats rather than corn fed up to 55% of total DM seems to improve protein deposition, without significant changes in animal performance, rumen environment or blood parameters.

Daily and alternate day supplementation of urea or soybean meal to ruminants consuming low-quality cool-season forage: II. Effects on ruminal fermentation

Five ruminally cannulated steers (initial BW=464±26kg) consuming low-quality forage (5% CP; 78% NDF; DM basis) were used in an incomplete 5×4 Latin square with four 18-d periods to determine the influence of supplemental N source and supplementation frequency (SF) on ruminal fermentation dynamics. Treatments, arranged as a 2×2 factorial with a negative control, consisted of urea or soybean meal (SBM) supplements offered daily (D) or alternate days (2D) plus an unsupplemented treatment (CON). Urea supplements were provided to meet 100% of the degradable intake protein requirement while SBM supplements were provided on an isonitrogenous basis. All supplemented treatments received an equal quantity of supplemental N over a 2-d period. Ruminal indigestible acid detergent fiber (IADF) passage rate was increased with supplementation (P≤0.03) on the days when D and 2D supplements were provided, as well as when only D supplements were provided. In contrast, ruminal liquid fill and dilution rate were not affected by supplementation, N source, or SF on the days when D and 2D supplements were provided (P≥0.24). However, when only D supplements were offered, ruminal liquid dilution rate was greater (P=0.03) for SBM supplemented steers compared with cohorts receiving supplemental urea, whereas ruminal liquid fill was greater (P=0.03) for steers fed urea supplements. Nitrogen supplementation increased (P<0.01) ruminal NH3–N by 122% and 70%, compared with the CON, on the days when both D and 2D supplements were provided and when only D supplements were provided, respectively. We noted a N source×SF interaction for ruminal NH3–N on the days when D and 2D supplements were provided (P=0.02), as well as when only D supplements were provided (P<0.01). On the days when D and 2D supplements were provided, urea increased NH3–N by 61% (2.93 vs. 4.73mM for D and 2D, respectively), whereas the increase in NH3–N with SBM was only 15% (2.23 vs. 2.58mM for D and 2D, respectively). However, when only D supplements were provided, NH3–N was almost 36% less for the 2D compared with the D urea treatment (2.76 vs. 1.81mM, respectively), whereas an 11% increase was noted for SBM 2D compared with SBM D (1.99 vs. 1.79mM, respectively). Total concentration of VFA was increased on the days when both D and 2D supplements were provided (P=0.03), but not influenced by treatments on the days when only D supplements were provided (P≥0.50). In summary, providing a urea-based supplement, as infrequently as every-other-day, was an effective alternative to a SBM-based supplement in maintaining acceptable ruminal fermentation of steers consuming low-quality, cool-season forage.

Effects of increasing concentrations of wet distillers grains with solubles in steam-flaked, corn-based diets on energy metabolism, carbon-nitrogen balance, and methane emissions of cattle1

The use of wet distillers grains with solubles (WDGS) in feedlot diets has increased in the Southern Great Plains as a result of the growing ethanol industry. Nutrient balance and respiration calorimetry research evaluating the use of steam-flaked corn (SFC)-based diets in conjunction with WDGS is limited. Therefore, the effects of increasing concentrations of WDGS in a SFC-based diet on energy metabolism, C, and N balance, and enteric methane (CH4) production was evaluated in Jersey steers fed at 2 times maintenance, using respiration calorimetry chambers. Four treatments were used in two 4 × 4 Latin square designs, using 8 steers. Treatments consisted of: 1) SFC-based diet with 0% WDGS (SFC-0); 2) SFC-based diet with 15% WDGS (SFC-15); 3) SFC-based diet with 30% WDGS (SFC-30); and 4) SFC-based diet with 45% WDGS (SFC-45). Diets were balanced for degradable intake protein (DIP) by adding cottonseed meal to the SFC-0 diet. As a proportion of GE, fecal, urinary, and CH4 energy increased linearly (P < 0.03) as WDGS concentration increased in the diet. In contrast, DE, ME, and retained energy decreased linearly (P < 0.01) as a proportion of GE as WDGS concentration increased. Increasing concentration of WDGS in the diet did not affect (P > 0.78) heat production as a proportion of GE. As a result of greater N intake, total N excretion increased linearly (P < 0.01) with increasing WDGS inclusion in the diet. Fecal C loss and CH4-C respired increased linearly (P < 0.01) when WDGS concentration increased in the diet whereas CO2-C respired decreased (linear, P = 0.05) as WDGS concentration increased. We conclude that CH4 production as a proportion of GE increases linearly (P < 0.01) when WDGS concentration in the diet is increased; however, dietary inclusion of WDGS at up to 45% seems to have no effect (P > 0.78) on heat production as a proportion of GE. The reason for a linear decrease in retained energy as WDGS increased was likely because of increased fecal energy loss associated with feeding WDGS. Total N excretion, fecal C loss, and CH4-C respired increased linearly with increasing concentration of WDGS in the diet. We determined NEg values for WDGS to be 2.02, 1.61, and 1.38 Mcal/kg when included at 15%, 30%, and 45%, respectively, in a SFC-based diet. From these results we conclude that the energy value (NEg) of WDGS in a finishing cattle diet based on SFC must be decreased as the inclusion increases.

Effects of Catecholamines on Gut Microflora and Potential for Beta- Adrenergic Agonists to Impact Ruminal Fermentation

Catecholamines are produced by chromaffin cells of the adrenal medulla and adrenergic and dopaminergic neurons from tyrosine. Catecholamines regulate many vital physiological and metabolic responses because of the location of receptors. The impact of catecholamines is not limited to mammals; direct effects of natural catecholamines on bacteria have been researched extensively to understand the potential impact of these compounds on bacterial infections in humans. Catecholamines have increased the growth of bacteria, virulence-associated factors, and adhesins and increased biofilm formation. Beta-adrenergic agonists are similar in structure and pharmacological properties to natural catecholamines. Beta-adrenergic agonists enhance performance of finishing cattle during the final days prior to harvest. Responses to beta-adrenergic agonists include increased average daily gain, improved feed efficiency, and increased carcass lean. These responses have been observed as a direct effect to the animal; however, a review of the literature suggests that the response to beta-adrenergic agonists also could be mediated by a direct or indirect effect on ruminal microorganisms. Ractopamine hydrochloride increased fermentation in vitro, particularly with increased amounts of degradable intake protein. Inclusion of ractopamine hydrochloride in vivo decreased ruminal concentrations of ammonia and amino acid. The rumen is host to a large population of diverse microorganisms, and a direct impact of a synthetic catecholamine on the microbial population could potentially alter fermentation and the ruminant performance. Reviewing literature on catecholamines and their direct impact on microorganisms could lead to improved decisions regarding dietary supplementation of beta-adrenergic agonists, threreby increasing the growth performance response in ruminants.

Effects of ruminal casein and glucose on forage digestion and urea kinetics in beef cattle1

Effects of supplemental glucose and degradable intake protein on nutrient digestion and urea kinetics in steers (Bos taurus) given ad libitum access to prairie hay (4.7% CP) were quantified. Six ruminally and duodenally cannulated steers (initial BW 391 kg) were used in a 4 × 4 Latin square with 2 extra steers. Treatments were arranged as a 2 × 2 factorial and included 0 or 1.2 kg of glucose and 240 or 480 g of casein dosed ruminally once daily. Each period included 9 d for adaptation, 4 d for total fecal and urine collections, and 1 d for ruminal and duodenal sampling. Jugular infusion of (15)N(15)N-urea with measurement of enrichment in urine was used to measure urea kinetics. Glucose reduced forage intake by 18% (P < 0.01), but casein did not affect forage intake (P = 0.69). Glucose depressed (P < 0.01) total tract NDF digestion. Glucose supplementation decreased ruminal pH 2 h after dosing, but the effect was negligible by 6 h (treatment × time; P = 0.01). Providing additional casein increased the ruminal concentration of NH(3), but the increase was less when glucose was supplemented (casein × glucose; P < 0.01). Plasma urea-N was increased (P < 0.01) by additional casein but was reduced (P < 0.01) by glucose. Microbial N flow to the duodenum and retained N increased (P ≤ 0.01) as casein increased, but neither was affected by glucose supplementation. Urea-N entry rate increased (P = 0.03) 50% with increasing casein. Urinary urea-N excretion increased (P < 0.01) as casein increased. The proportion of urea production that was recycled to the gut decreased (P < 0.01) as casein increased. Glucose supplementation decreased (P < 0.01) urinary urea excretion but did not change (P ≥ 0.70) urea production or recycling. The amount of urea-N transferred to the gut and captured by ruminal microbes was less for steers receiving 480 g/d casein with no glucose than for the other 3 treatments (casein × glucose interaction, P = 0.05), which can be attributed to an excess of ruminally available N provided directly to the microbes from the supplement. Overall, the provision of supplemental glucose decreased forage intake and digestibility. Increasing supplemental casein from 240 to 480 g/d increased urea production but decreased the proportion of urea-N recycled to the gut.