Plasma urea-N Research Articles

Valine and isoleucine requirement of 20- to 45-kilogram pigs1,2

Three experiments were conducted to determine the Val and Ile requirements in low-CP, corn-soybean meal (C-SBM) AA-supplemented diets for 20- to 45-kg pigs. All experiments were conducted for 26 to 27 d with purebred or crossbred barrows and gilts, which were blocked by initial BW. Treatments were replicated with 5 or 6 pens of 3 or 4 pigs per pen. At the beginning of Exp. 1 and the end of all experiments, blood samples were obtained from all pigs to determine plasma urea N (PUN) concentrations. All diets were C-SBM with 0.335% supplemental Lys to achieve 0.83% standardized ileal digestible (SID) Lys, which is the Lys requirement of these pigs. In Exp. 1, 0, 0.02, 0.04, 0.06, 0.08, or 0.10% L-Val was supplemented to achieve 0.51, 0.53, 0.55, 0.57, 0.59, or 0.61% dietary SID Val, and Thr, Trp, Met, and Ile were supplemented to maintain Thr:Lys, Trp:Lys, TSAA:Lys, and Ile:Lys ratios of 0.71, 0.20, 0.62, and 0.60, respectively. Also, supplemental Gly and Glu were added to all diets to achieve 1.66% Gly + Ser and 3.28% Glu, which is equal to the Gly + Ser and Glu content of a previously validated positive control diet that contained no supplemental AA. Treatment differences were considered significant at P < 0.10. Valine addition increased ADG, ADFI, and G:F in pigs fed 0.51 to 0.59% SID Val (linear, P < 0.08), but ADG and ADFI were decreased at 0.61% SID Val (quadratic, P ≤ 0.10). On the basis of ADG and G:F, the SID Val requirement is between 0.56 and 0.58% in a C-SBM diet supplemented with AA. In Exp. 2 and 3, 0, 0.02, 0.04, 0.06, or 0.08% L-Ile was supplemented to achieve 0.43, 0.45, 0.47, 0.49, or 0.51% dietary SID Ile, and Thr, Trp, Met, and Ile were supplemented to maintain Thr:Lys, Trp:Lys, TSAA:Lys, and Val:Lys ratios of 0.71, 0.20, 0.62, and 0.74, respectively. Also, supplemental Gly and Glu were added to achieve 1.66% Gly + Ser and 3.28% Glu as in Exp. 1. Data from Exp. 2 and 3 were combined and analyzed as 1 data set. Daily BW gain, ADFI, and G:F were not affected by Ile additions to the diet; however, ADFI was decreased among pigs fed the diet with 0.45% SID Ile (P < 0.10) compared with pigs fed the 0.43% SID Ile diet. Broken-line analysis requirements could not be estimated for the combined data from Exp. 2 or 3. The results of this research indicate that the SID Val requirement is between 0.56 to 0.58% (0.67 to 0.70 SID Val:Lys), and the Ile requirement is adequate at 0.43% SID Ile (0.52 SID Ile:Lys) for 20- to 45-kg pigs.

Standardized ileal digestible tryptophan-to-lysine ratios in growing pigs fed corn-based and non-corn-based diets1,2

Two 21-d experiments were conducted to determine the optimum standardized ileal digestible (SID) Trp:Lys in growing pigs fed corn-based diets compared with non-corn-based diets. The primary response variables in both experiments were ADG and plasma urea N (PUN) concentrations with the optimum SID Trp:Lys determined using broken-line analysis. Experiment 1 evaluated the optimum SID Trp:Lys in growing pigs fed corn-based diets consisting primarily of corn with minor inclusion of Canadian field peas and corn gluten meal to keep the SID Trp:Lys low. This experiment used 120 crossbred pigs (initial BW: 25.73 ± 2.46 kg) that were blocked by sex and initial BW and allotted to 5 SID Trp:Lys with 5 pens each for the first 4 treatments and 4 pens for the last treatment and 5 pigs/pen. Diets were formulated by the addition of supplemental Trp to create various SID Trp:Lys (12.77, 14.07, 15.50, 16.91, and 17.94%) with a constant SID Lys of 0.66%, which was determined to be 83% of the Lys requirement for pigs at this location. As the SID Trp:Lys increased from 12.77 to 17.94%, ADG increased (0.562, 0.648, 0.788, 0.787, and 0.815 kg/d) linearly (P < 0.001) and quadratically (P = 0.009), resulting in an optimum SID Trp:Lys of 15.73% (P < 0.001). Plasma urea N decreased (10.43, 9.30, 8.21, 8.55, and 9.25 mg/dL) linearly (P = 0.069) and quadratically (P = 0.015), resulting in an optimum SID Trp:Lys of 15.83% (P = 0.007). Experiment 2 evaluated the optimum SID Trp:Lys in growing pigs fed non-corn-based diets consisting primarily of barley and Canadian field peas, with smaller proportions of corn and wheat. Experiment 2 used 120 crossbred pigs (initial BW: 28.49 ± 2.92 kg) that were allotted to 5 increasing SID Trp:Lys (13.05, 14.32, 15.59, 16.85, and 18.11%; 0.66% SID Lys) in the same manner as Exp. 1. As SID Trp:Lys increased in Exp. 2, ADG increased linearly (P = 0.007) with the optimum SID Trp:Lys of 15.99% (P = 0.048). Plasma urea N concentrations decreased linearly (P = 0.056) and quadratically (P = 0.067) as SID Trp:Lys increased, resulting in an optimum SID Trp:Lys of 15.29% (P = 0.009). Averaging the break point values for ADG and PUN obtained from broken-line analysis for Exp. 1 and 2 produced optimum SID Trp:Lys of 15.78 and 15.64%, respectively. Based on the results from these 2 experiments, it seems that the optimum SID Trp:Lys is virtually unaffected by the dietary feedstuffs used as long as the diets are formulated on an SID AA basis.

A comparative study on mimosine, 3,4-dihydroxy pyridone (3,4-DHP) and 2,3-dihydroxy pyridone (2,3-DHP), purine derivatives (PD) excretion in the urine, thyroid hormone and blood metabolites profiles of Thai swamp buffalo (Bubalus bubalis) and Murrah buffalo (Bubalus bubalis)

Four Thai swamp buffaloes (SB) and four Murrah buffaloes (MB) fed a based diet of fresh ruzi grass (Bachiaria ruziziensis) with an increased proportion of fresh leucaena leaves. Intake of nutrients in animals increased when ruzi grass was mixed with leucaena. Digestibility of nutrients were the highest in SB and MB fed diets containing 25% and 50% of leucaena, respectively, and nitrogen (N) balances in both animal breeds were varied among diets. The regression equation coefficient of mimosine + DHP in the urine was twice as high in SB than in MB. Urinary purine derivatives excretion rate in SB was higher than that in MB. Plasma triiodothyronine and thyroxine declined in both animal breeds fed a diet containing >1 g mimosine intake/kg BW(0.75)/day. Plasma urea-N was the lowest in SB, but the highest in MB when fed a diet containing 84% of leucaena. Plasma β-HBA in SB have declined when diets contained >50% of leucaena but that in MB was not affected by any diet. In conclusion, the effect of leucaena in diet upon buffalo breeds depends on the proportion of leucaena in the diet, mimosine contents and condensed tannins components.

Technical note: Effect of determining baseline plasma urea nitrogen concentrations on subsequent posttreatment plasma urea nitrogen concentrations in 20- to 50-kilogram pigs1,2

Plasma urea N (PUN) has been used as an indicator of AA requirements and efficiency of AA utilization in swine. However, PUN concentrations vary among a population of pigs, even a population with a close range of BW and fed the same diet. Thus, pretreatment or baseline PUN concentrations are used as a covariate to reduce variation of posttreatment PUN. However, this procedure increases experimental costs and stress to the pigs. Data from 14 experiments (26 to 28 d in duration) conducted using PUN as a response variable were compiled into 1 data set. Each experiment had 4 to 6 treatments. The purpose of this technical report was to summarize the effect of determining pretreatment baseline PUN concentrations on subsequent posttreatment PUN concentrations in 20- to 50-kg pigs. In all experiments, pigs were fed corn- and soybean meal-based diets and low-CP diets with various AA additions; pigs were assigned to dietary treatments in a randomized complete block design with a minimum of 4 replicates of 3 to 5 pigs each. Before the start of each experiment, all pigs were fed a common diet for a minimum of 3 d. Blood samples were collected from each pig before allotment to dietary treatments (d 0) and at the end of each experiment. The baseline (d 0) PUN was analyzed as a covariate for posttreatment PUN. Data from each experiment were analyzed without and with baseline PUN in the statistical model. In all experiments combined, there were 768 possible treatment comparisons. The covariate baseline PUN was statistically significant (P < 0.10) in 9 of 14 experiments. However, only 8 treatment differences changed statistical significance as a result of analyzing the data with baseline PUN as a covariate. These 8 treatment differences were in 3 experiments. These results indicate that it is not always necessary to determine baseline PUN concentrations when feeding diets with large differences in AA content.

Net nutrient flux in visceral tissues of goats fed diets based on maize or wheat

The objective of this study was to investigate the effects of dietary starch sources on the net portaldrained viscera (PDV) flux of metabolites in goats fed diets based on maize and wheat, respectively. Eight 8-month-old Liuyang Black wether goats, with catheters surgically in the mesenteric vein, the portal vein and the carotid artery, were assigned to one of two diets for determination of net nutrient flux across the PDV. There were no differences (P>0.05) in plasma concentrations of glucose and ammonia-nitrogen (N) in the portal vein and carotid artery, and net PDV flux of glucose and urea-N between maize diet and wheat diet. The portal plasma urea-N concentration and net PDV flux of ammonia-N of goats fed maize diet were lower (P<0.05) than those of goats fed wheat diet. Plasma concentrations in the portal vein and carotid artery and net PDV flux of certain essential amino acids of goats fed maize diet were higher (P<0.05) than those of goats fed wheat diet. The results of this study suggested that dietary starch source could affect N absorption and utilization in goats.

Maximizing the use of supplemental amino acids in corn-soybean meal diets for 20- to 45-kilogram pigs1,2

Four experiments were conducted to determine the Lys requirement, the maximum amount of supplemental Lys that does not decrease growth performance, and to determine the order of limiting AA beyond Lys, Thr, Trp, and Met in a corn-soybean meal diet for 20- to 45-kg pigs. All experiments were conducted for 27 to 28 d with purebred or crossbred barrows and gilts, which were blocked by initial BW. Treatments were replicated with 4 to 6 pens of 4 to 6 pigs per pen. In all experiments, pigs and feeders were weighed on d 0, 14, and 27 or 28. At the beginning and end of all experiments, blood samples were obtained from all pigs to determine plasma urea N (PUN) concentrations. In Exp. 1, 0.830, 0.872, 0.913, and 0.955% standardized ileal digestible (SID) Lys was fed, whereas 0.747, 0.788, 0.830, 0.872, and 0.913% SID Lys was fed in Exp. 2. Broken-line analysis requirement estimates could not be estimated from any response variable in Exp. 1, but in Exp. 2, using ADG and PUN, the estimated SID Lys requirement was 0.83%. In Exp. 3, 0, 0.118, 0.191, 0.264, and 0.335% supplemental Lys was added to achieve 0.83% SID Lys in all diets, and Thr, Trp, and Met were supplemented to maintain Thr:Lys, Trp:Lys, and TSAA:Lys of 0.65, 0.18, and 0.60, respectively. Based on ADG, ADFI, and G:F, up to 0.23% supplemental Lys can be added along with supplemental Thr, Trp, and Met without negatively affecting growth performance; PUN was linearly decreased (P < 0.001) by supplemental Lys. In Exp. 4, treatments were 1) positive control (PC) without supplemental AA, 2) negative control (NC) with 0.335% supplemental Lys + 0.140% l-Thr + 0.035% l-Trp + 0.117% dl-Met, 3) NC + 0.044% l-Val, 4) NC + 0.021% l-Ile, and 5) NC + 0.044% l-Val + 0.021% l-Ile. Individual addition of Val and Ile did not improve (P > 0.10) ADG or G:F compared with the NC. The combined addition of Val + Ile resulted in ADG that was intermediate between the PC and NC diets but not different from either diet (P > 0.10); G:F was not improved (P > 0.10) to that observed in pigs fed the PC diet. The PUN was not different (P > 0.10) among pigs fed diets with supplemental AA but less (P < 0.10) than pigs fed the PC. The results of this research indicate that the Lys requirement for 20- to 45-kg pigs is 0.83% SID Lys, up to 0.23% supplemental Lys (0.29% l-Lys·HCl or 0.45% l-Lys·SO(4)) can be added along with supplemental Thr, Trp, and Met without negatively affecting growth performance, and another AA besides Val and Ile may be limiting growth performance in a corn-soybean meal diet with 0.335% supplemental Lys.

Effect of corn particle size and soybean meal treatment on performance of finishing beef steers fed corn-silage-based diets

In the first experiment, 39 medium-frame beef steers (456 ± 41 kg) were used in a 2 × 2 factorial arrangement of treatments to evaluate the effect of different feeding strategies to maximize energy and protein deposition on finishing performance and plasma amino acid profile of beef steers fed corn silage ad libitum for 99 d. To achieve this goal, steers were individually supplemented with either 6.6 kg DM d-1 of cracked corn (CC) or ground corn (GC) in combination with 540 g DM d-1 of either solvent extracted (SS) or lignosulfonate-treated soybean meal (Soypass® SP). Dry matter intake, average daily gain and feed to gain ratio were not affected by treatments or by their interaction (P &gt; 0.10). When compared with SS, SP tended to increase (P = 0.07) grade fat (1.3 and 2.2 ± 0.5 mm, respectively). The CC diets reduced the plasma concentration of branched-chained amino acids (P = 0.03) and leucine (P = 0.01), and tended to decrease that of isoleucine (P = 0.06) compared with the GC diets. No effect of diet was observed on plasma urea-N concentration. In the second experiment, four steers were used in a 4 × 4 Latin square design to evaluate digestibility and N balance of the diets used in exp. 1. Reducing particle size of corn increased apparent digestibility of starch (P = 0.01) and tended to reduce apparent digestibility of NDF (P = 0.07). In conclusion, formulating diets with ground or cracked corn in combination with solvent extracted or lignosulfonate-treated soybean meal does not appear to influence steer performance or digestion parameters.

CASE STUDY: Relationships Between Dietary, Plasma, and Muscle Amino Acids in Maintenance Horses, Exercising Horses, and Growing Weanling Horses

The objective of this study was to evaluate relationships between diet, plasma, and muscle amino acids for horses in maintenance, exercise, and growth. Eight horses in each maintenance (MH) and exercise (EH) group were fed diets for 8 wk, whereas 6 weanlings in the growth (GH) group were fed diets for 4 wk. Blood samples and muscle biopsies were taken at the beginning of the study from the MH and EH groups and at the end of the study for all groups. Plasma urea-N and lysine concentrations were higher for the EH group than for the MH group, whereas plasma urea-N concentrations were higher for the GH group than for the MH group. Plasma histidine and 3-methyl-histidine concentrations for the GH group were higher than for the MH group at the conclusion of the study. Poststudy muscle methionine concentrations for the EH group were lower than for the MH group. Correlations were found between plasma and muscle concentrations of urea-N for the MH and EH groups. Plasma and muscle correlations also existed with serine for the EH group and with threonine, leucine, valine, histidine, phenylalanine, and serine for the GH group. Fewer correlations for the MH and EH groups may indicate an excess of amino acids in the diet in relation to needs, whereas the large number of correlations for the GH group may indicate a closer relationship between supply of amino acids in the diet and need by the body. More exploration of this area is needed for horses in all functions.

Dietary effects of distillers dried grains with solubles on performance and milk composition of lactating sows1

A study was conducted to evaluate the dietary effect of adding increasing concentrations of distillers dried grains with solubles (DDGS) to corn- and soybean meal-based sow lactation diets on sow and litter performance, energy and N digestibility, plasma urea N (PUN), and milk fat and protein concentrations. Mixed-parity sows [n = 307; 221 ± 15 kg of BW, 4.54 parities, litter size of 10.6, and litter weight at birth (alive) of 15.14 kg] were assigned randomly to 1 of 5 dietary treatments: control (CON; corn-soybean meal); 10, 20, and 30% DDGS; and 30% DDGS high-protein (HP) diets. Sows were moved to farrowing rooms on d 109 of gestation and were fed the dietary treatments until weaning. Within each treatment group, feces and urine for energy and N digestibility analysis (from d 10 to 12 of lactation) and blood for PUN analysis and milk fat and protein concentrations (on d 0 and 19 of lactation) were collected from 6 randomly chosen parity 3 to 5 sows. There were no dietary effects (P = 0.10) of DDGS on ADFI of sows and sow backfat change. However, sows fed 30% DDGS HP lost more BW compared with sows fed CON (P < 0.05). There were no dietary effects (P = 0.71) of DDGS on preweaning mortality of piglets, litter weight gain, and piglet ADG. Dietary treatments did not affect (P > 0.05) DE, ME, N retention, or N digestibility of the diets. There were no differences in the concentrations of fat and protein in milk at weaning (d 19) among dietary treatments. Sows fed 20 and 30% DDGS had less (P < 0.05) PUN at weaning (d 19) than sows fed CON and 30% DDGS HP. Inclusion of up to 30% DDGS in a lactation diet did not affect (P > 0.05) sow and litter performance, DE and ME contents of the diets, N retention and digestibility, and milk composition compared with sows fed a corn-soybean meal CON diet. It was concluded that addition of up to 30% DDGS in a lactation diet will support satisfactory sow and litter performance.

Effect of dry- versus wet-autoclaving of spray-dried egg albumen compared with casein as protein sources on apparent nitrogen and energy balance, plasma urea nitrogen and glucose concentrations, and growth performance of neonatal swine1

Forty crossbred neonatal pigs with an average initial age of 4 d and BW of 2.16 kg were used in a 28-d experiment to evaluate the nutritional effects of autoclaving a commercial sugar-free, spray-dried egg albumen (EA) compared with casein. Basal diet protein sources were lactic acid casein and EA. Two more dietary treatments were made by replacing the EA with dry-autoclaved EA (DAEA) or wet-autoclaved EA (WAEA, EA and water mixed in a 1.0:1.2 ratio before autoclaving). The DAEA and WAEA were autoclaved at 121 degrees C and 1.75 kg/cm(2) pressure for 30 min, and WAEA was oven-dried after autoclaving. Analyzed trypsin inhibitor units/mg of EA, DAEA, and WAEA were 535.0, 9.0, and 6.5, respectively. Pigs were fed the diets in gruel form to appetite in individual metabolism cages every 2 h during the experiment. Blood samples were taken on d 7, 14, and 21, and total urine and fecal grab-samples were collected from d 14 to 21 of the experiment. Response criteria were N and energy balance, plasma urea N (PUN) and glucose concentrations, and growth performance. The WAEA was a higher quality protein source for neonatal pigs than DAEA. Pigs fed the diet containing WAEA absorbed and retained more (P < 0.05) grams of N/d, had higher (P < 0.05) percentages of N and energy that were absorbed and retained/intake, had lower (P < 0.05) concentrations of PUN overall, and had higher (P < 0.05) ADG and G:F than pigs fed the diet containing DAEA. Most response criteria of pigs fed the diets containing DAEA or EA were not different, although pigs fed the diet containing DAEA had lower (P < 0.05) overall PUN concentrations, and pigs fed the diet containing EA had higher (P < 0.05) percentages of energy absorbed and retained/intake, and higher ADG and G:F than pigs fed the diet containing DAEA. Growth performance was not different for pigs fed the diets containing WAEA or casein. However, pigs fed the diet containing casein excreted less (P < 0.05) fecal N, retained more (P < 0/05) grams of N/d, had higher percentages of N absorbed and retained/intake, and had lower (P < 0.05) PUN concentrations overall than pigs fed the diet containing WAEA. In conclusion, WAEA was a higher quality protein source for neonatal pigs than DAEA or EA, whereas lactic casein was a higher quality protein source for neonatal pigs than EA, DAEA, or WAEA.

Inflammation-associated responses in piglets induced with post-weaning colibacillosis are influenced by dietary protein level

Forty piglets (average body weight = 5.32 kg) were used to investigate the effect of dietary crude protein (CP) content on immunological responses following a challenge with enterotoxigenic Escherichia coli (ETEC) K88. Pigs, housed 4 per pen, were randomly allotted to 2 diets: 1) a high, 225 g/kg CP diet (HCP) or 2) a low, 176 g/kg CP diet (LCP) supplemented with crystalline amino acids. Pigs were orally challenged with 6 mL of an ETEC K88 suspension containing 10 10 cfu/mL on d 8 after weaning. Blood samples were collected from 10 pigs (1 pig/pen) on d 7 (at weaning), −24 h, 8 h, 72 h and 7 d after the challenge for determination of plasma urea N (PUN) and serum concentrations of tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) and haptoglobin (Hp). Tumor necrosis factor alpha, IL-1β and Hp were measured as indicators of inflammatory responses. The concentrations of serum TNF-α at 8 h, 72 h and 7 d after challenge were similar to the level observed at 24 h before challenge but higher ( P < 0.05) than the weaning level. Pigs fed the LCP diet had lower ( P = 0.032) concentrations of IL-1β (72 vs. 116 pg/mL) at 8 h post-challenge compared with those fed the HCP diet. Likewise, pigs fed the LCP diet tended to have lower ( P = 0.088) concentration of Hp (9 vs. 25 mg/dL) compared with those fed the HCP diet at 8 h post-challenge. Compared with the weaning concentration, PUN concentration at 72 h after ETEC challenge was higher ( P < 0.05) in pigs fed the HCP diet. The results indicate that the LCP diet supplemented with crystalline amino acids reduced inflammatory responses, as indicated by serum IL-1β, in piglets infected with ETEC K88.

Intake, digestibility, and nitrogen retention by sheep supplemented with warm-season legume haylages or soybean meal

The high cost of commercial supplements necessitates evaluation of alternatives for ruminant livestock fed poor quality warm-season grasses. This study determined how supplementing bahiagrass haylage (Paspalum notatum Flügge cv. Tifton 9) with soybean [Glycine max (L.) Merr.] meal or warm-season legume haylages affected the performance of lambs. Forty-two Dorper x Katadhin lambs (27.5 +/- 5 kg) were fed for ad libitum intake of bahiagrass haylage (67.8% NDF, 9.6% CP) alone (control) or supplemented with soybean meal (18.8% NDF, 51.4% CP) or haylages of annual peanut [Arachis hypogaea (L.) cv. Florida MDR98; 39.6% NDF, 18.7% CP], cowpea [Vigna unguiculata (L.) Walp. cv. Iron clay; 44.1% NDF, 16.0% CP], perennial peanut (Arachis glabrata Benth. cv. Florigraze; 40.0% NDF, 15.8% CP), or pigeonpea [Cajanus cajan (L.) Millsp. cv. GA-2; 65.0% NDF, 13.7% CP]. Haylages were harvested at the optimal maturity for maximizing yield and nutritive value, wilted to 45% DM, baled, wrapped in polyethylene plastic, and ensiled for 180 d. Legumes were fed at 50% of the dietary DM, and soybean meal was fed at 8% of the dietary DM to match the average CP concentration (12.8%) of legume haylage-supplemented diets. Lambs were fed each diet for a 14-d adaptation period and a 7-d data collection period. Each diet was fed to 7 lambs in period 1 and 4 lambs in period 2. Pigeonpea haylage supplementation decreased (P < 0.01) DM and OM intake and digestibility vs. controls. Other legume haylages increased (P < 0.05) DM and OM intake vs. controls; however, only soybean meal supplementation increased (P = 0.01) DM digestibility. All supplements decreased (P = 0.05) NDF digestibility. Except for pigeonpea haylage, all supplements increased (P < 0.01) N intake, digestibility, and retention, and the responses were greatest (P = 0.04) with soybean meal supplementation. Microbial N synthesis was reduced (P = 0.02) by pigeonpea haylage supplementation, but unaffected (P = 0.05) by other supplements. Efficiency of microbial protein synthesis was unaffected (P = 0.05) by diet. Ruminal ammonia concentration was increased (P = 0.01) by all supplements, but only soybean meal and annual peanut haylage increased (P < 0.03) plasma urea-N concentrations. Perennial peanut, annual peanut, and cowpea haylages are promising protein supplements for growing lambs.

Effects of abomasal pectin infusion on milk production, digestion and nitrogen utilization pattern of lactating Saanen dairy goats

To study the effects of graded abomasal infusion of pectin on milk production, nitrogen balance and nutrient digestibilities of goats, four abomasally cannulated lactating Sannen dairy goats were used in a 4 × 4 latin square design with 14-d periods. Goats were fed the same basal diet and the treatments were the abomasal infusion of 0, 40, 80 or 120 g/d of citrus pectin. Pectin infusion resulted in linear decreases in basal ration intake from 2250 to 1985 g/d. There was insignificant decrease in total tract apparent digestibilities of dry matter and neutral detergent fiber. Decreased basal ration intake and digestibility led to decreased milk production from 1.95 to 1.75 kg/d. Milk fat content increased quadratically with increasing levels of infused pectin ( P = 0.04), but milk fat yield was unaffected by treatments. Milk total solids and solid-not-fat were also linearly decreased by pectin infusion. There were linear decreases in urinary N and plasma urea N (PUN) with the increase in infusion of pectin. As a proportion of N intake, urinary N excretion decreased from 36.31 to 31.92%, whereas N excreted from faeces increased from 25.2 to 29.4%, as the amount of pectin infusion increased. Abomasal pectin linearly decreased faecal pH from 7.31 to 6.86 and tended to decrease faecal ammonia from 0.246 to 0.215 mg/g faecal DM. These results suggest that manipulating dairy goats diets to increase postruminal fermentation may reduce urinary N and consequently manure ammonia losses. However, decreased digestibility and milk production at the highest level of pectin infusion is suggesting that pectin may have reduced postruminal nutrient utilization.

Digestion and nitrogen utilization in dairy heifers limit-fed a low or high forage ration at four levels of nitrogen intake

The hypothesis of this experiment is that a low-forage (LF) ration will be utilized with greater efficiency than a high-forage ration (HF) by dairy heifers and that the response will be affected by level of N intake. To test this hypothesis, 8 Holstein heifers (beginning at 362±7kg and 12.3±0.4 mo) were fed 8 rations according to a split-plot, 4×4 Latin square design. Treatments were formulated to contain 25 or 75% forage (corn silage and chopped wheat straw) and fed at 4 levels of N intake [0.94 (Low), 1.62 (MLow), 2.30 (MHigh), 2.96 (High) g of N/kg of metabolic body weight per day]. Diets were limit-fed to maintain equal intake of metabolizable energy. Blood samples were collected over d 19 to 20, and feces and urine were collected for 8 d per 28-d period. Organic matter (OM) intake was greater for heifers fed HF, but, due to increased OM digestibility of LF (74.0 vs. 67.6%±0.9), digestible OMI was unaffected by forage level. Organic matter digestibility was affected by an interaction between forage level and N intake, increasing to a plateau of 78.01% at 18.43% crude protein for LF-fed and 68.78% at 13.90% crude protein for HF-fed heifers. Apparent N digestibility was greater for heifers fed LF and increased from 47.7 to 80.8% between Low and High N intake. Less N appeared in the feces of heifers fed LF than HF (45.56 vs. 52.60 g/d). Urea-N excretion was not different between forage levels, but increased linearly with N intake. Concentration of plasma urea-N was significantly higher for LF and with increasing N intake. Urea clearance rate (L/h) did not differ between forage levels and increased, but at a decreasing rate, as N intake increased. A significant interaction resulted from urea clearance increasing at a greater rate and resulting in higher values for HF, whereas clearance of urea for heifers fed LF resulted in significantly lower maximal values. Like urea-N excretion, daily urinary N excretion was affected only by N intake. Retained N responded linearly to increased levels of N intake. The significant reduction observed in fecal N excretion for LF was counterbalanced by numerical increases in urinary N excretion so that total N excretion and retention were not different between forage levels. The percentage of N intake that was retained only tended to be affected by an interaction and was not significantly affected by forage level. It is concluded that increasing N intake increases the digestibility of OM, the magnitude of which depends on the level of dietary forage provided. Furthermore, differences in N utilization between LF and HF in this trial were small and were not evident until N intake increased to impractical levels.

The comparative study digestion and metabolism of nitrogen and purine derivatives in male, Thai, Swamp buffalo and Thai, Brahman cattle

Studies on in vivo digestion, rates of passages, metabolism of nitrogen, urinary purine derivative excretion and blood metabolites were carried out in Thai Brahman cattle and Thai swamp buffaloes (16 months old). The animals were fed mixed diets based on pineapple (Ananas comusus) waste silage containing urea-N (NPN) and true protein from a concentrate (TP). The Brahman cattle (310 +/- 15 kg) were heavier than the swamp buffaloes (195 +/- 9.4 kg) and had higher dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF) intakes when compared on the basis of their metabolic body weight (BW(0.75)), but these intakes did not differ significantly when the diets of each animal species were compared. The total tract, apparent digestibilities of dry matter (DM) and organic matter (OM) were not significantly different between the animal species when comparing the two types of diets. The NDF digestibility was significantly (P < 0.01) decreased in both animal species when fed the TP diet, but was significantly (P < 0.01) greater in cattle than in swamp buffaloes. The passage rate digesta k(1) (P < 0.01) and the passage rate digesta k(2) (through the caecum and proximal colon) (P < 0.03) were significantly slower, and the total mean retention time (TMRT) (P < 0.01) was significantly longer in swamp buffaloes when compared to Brahman cattle, but the transit time (TT) showed no difference (P = 0.07) between the animal species or the diets. The N intakes were not different in both animal species and diets, but urine-N was greater (P < 0.05) in Brahman cattle than that in swamp buffaloes. Urine N and digestibility of N were significantly (P < 0.04) higher in animals fed the NPN diet than those fed the TP diet. Urinary purine derivatives (PD) and the creatinine (Cr) excretion of swamp buffaloes were significantly (P < 0.01) lower than those in Brahman cattle. Plasma urea-N (BUN) concentration was significantly (P < 0.01) higher in swamp buffaloes than that in Brahman cattle, but plasma glucose and insulin concentrations were significantly (P < 0.01) higher in Brahman cattle than in swamp buffaloes. The concentrations of non-esterified fatty acids (NEFA) were not significantly (P > 0.05) different in animals fed different diets. The present study demonstrated that Brahman cattle were better in fiber digestibility than swamp buffaloes at utilizing pineapple waste silage with both N sources.

Feeding strategies for improving productivity of growing steers fed grass silage

Two experiments were conducted to determine the relationship between corn particle size and soybean meal treatment on growth, diet digestibility, and nitrogen balance of growing steers. In the first experiment, 40 medium-frame beef steers (250 ± 11 kg) were fed individually for 140 d a diet based on grass silage offered for ad libitum consumption and supplemented with either 3.5 kg of DM d-1 of cracked corn (CC) or ground corn (GC) and with 450 g of DM d-1 of solvent extracted (SS) or lignosulfonate-treated soybean meal (Soypass™ SP). Dry matter intake was not affected by treatments and averaged 8.6 ± 0.3 kg d-1 (P &gt; 0.10). Average daily gain was higher for animals receiving the ground corn than those fed cracked corn. Feed to gain ratio was not affected by treatments. There was an interaction between treatments for plasma urea-N concentration, with source of soybean meal having no effect with CC. When compared with SS, SP supplement reduced plasma urea-N when fed with GC. No effect of soybean meal and its interaction with corn processing was observed on growth performance. In the second experiment four additional steers were used in a 4 × 4 Latin square design to evaluate diet digestibility and nitrogen balance. There was an interaction between treatments for starch apparent digestibility and N retained, the values being respectively, 90, 86, 93, and 92% (SEM = 1.2; P &lt; 0.01) and 36, 42, 44 and 41 g d-1 (SEM = 2.8; P &lt; 0.03) for CCSS, CCSP, GCSS and GCSP, respectively. Altogether, the results indicate a slight advantage to reduce particle size of corn in growing steers fed grass silage. However, soybean meal treatment resulted in limited effects on growth and digestion. Key words: Rumen carbohydrate, undegradable protein, performance, steers

Effects of rumen-protected methionine supplementation and bacterial lipopolysaccharide infusion on nitrogen metabolism and hormonal responses of growing beef steers1

Metabolic demand for sulfur-containing AA increases during inflammation in nonruminants. Therefore, Met supplementation may alleviate the negative effects of infection on N balance. Effects of gram-negative bacterial lipopolysaccharide (LPS) and supplemental dietary Met on N balance, serum hormones and haptoglobin, and plasma urea-N and AA were evaluated in 20 Angus-cross steers (BW = 262 +/- 6.3 kg). Treatments (2 x 2 factorial) were infusion of no LPS (-LPS) or a prolonged low dose of LPS (+LPS) and dietary supplementation of no (-MET) or 14 g/d (+MET) of rumen-protected Met (providing 7.9 g/d of dl-Met). Steers were adapted to a roughage-based diet (DMI = 1.4% of BW daily) and supplemental Met for 14 d, and were then infused (1 mL/min via intravenous catheter) with LPS on d 1 (2 microg/kg of BW) and 3 (1 microg/kg of BW) of a 5-d collection period. Blood was collected on d 1, before LPS infusion, and at 2, 4, 6, 8, 10, 12, and 24 h after LPS challenge. Diet samples, feed refusals, feces, and urine were collected daily for 5 d. Rectal temperature and serum concentrations of cortisol, prolactin, tumor necrosis factor-alpha, and haptoglobin increased, whereas thyroxine and triiodothyronine decreased for +LPS vs. -LPS steers (LPS x h; P < 0.01). Plasma urea-N was greater for +LPS than -LPS steers (LPS; P = 0.03), and serum IGF-1 was not affected (P > or = 0.26) by LPS or Met. Plasma concentrations of Thr, Lys, Leu, Ile, Phe, Trp, Asn, Glu, and Orn decreased, plasma Ala increased, and Gly and Ser initially increased, then declined in +LPS vs. -LPS steers (LPS x h; P < or = 0.04). Plasma Met was greater for +MET than -MET steers before LPS infusion, but declined in +MET steers after LPS infusion (LPS x Met x h; P < 0.01). By design, DMI was not different, but DM digested was less (P = 0.04) for +LPS than -LPS steers. Infusion of LPS did not affect (P > or = 0.24) N intake, fecal N excretion, or N digested, but resulted in greater (P < 0.01) urinary N excretion and less (P < 0.01) N retention. The absence of an LPS x Met interaction (P = 0.26) for N retention indicates that supplemental Met does not improve the N utilization of growing beef steers exposed to a gram-negative bacterial endotoxin. Decreases in plasma concentrations of several essential AA in +LPS steers suggest that metabolic demand for these AA likely increased in steers exposed to endotoxin.

Nutrition, Metabolism, and Fertility in Dairy Cows: 1. Dietary Energy Source and Ovarian Function

In previous studies, high plasma insulin was associated with earlier resumption of postpartum estrous cycles in dairy cows. The objective of this experiment was to quantify hormonal and ovarian responses to dietary starch and fat contents. Thirty cows were fed on a standard diet from calving until 40 d in milk (DIM) and then 6 cows were allocated to each of 5 isoenergetic diets containing 231, 183, 159, 135, and 87g of starch and 39, 42, 43, 45, and 48g of fat/kg of dry matter (DM) for diets 1 to 5, respectively, until 70 DIM. Estrus was synchronized at 60 DIM. Between 60 and 70 DIM, energy intake, milk yield, and energy balance were similar among diet groups. Plasma insulin-to-glucagon ratio increased with increasing dietary starch and decreasing dietary fat concentrations, reaching a break point at 159g of starch, 43g of fat/kg of DM (diets 1 to 5: mean 3.86, 3.78, 3.59, 2.98, 2.06±standard error 0.22). Growth hormone, insulin-like growth factor-I, and leptin did not vary among diets. The greatest dietary starch concentration was associated with elevated plasma urea-N (diets 1 to 5: mean 3.69, 3.01, 2.94, 2.95, 2.75,±standard error 0.13mmol/L, respectively) and delayed postovulatory progesterone increase (progesterone at 3 to 5 d postovulation for diets 1 to 5: mean 2.7, 5.9, 4.2, 5.6, 4.3±standard error 0.9ng/mL, respectively). The number of small (<5mm) ovarian follicles was positively related to starch intake (r=0.381) and plasma insulin concentration (r=0.402). It is concluded that to maintain adequate insulin-to-glucagon ratio in cows at the start of the breeding period, dietary starch concentration should be above 160g/kg of DM and dietary fat below 44g/kg of DM, and this should have a positive effect on ovarian function.

The effects of concentrate added to pineapple (Ananas Comosus linn. Mer.) waste silage in differing ratios to form complete diets, on digestion, excretion of urinary purine derivatives and blood metabolites in growing, male, Thai swamp buffaloes

Four, male, growing Thai swamp buffaloes (197 +/- 5.3 kg and all 1 year old) were used to evaluate the effects of concentrate added to pineapple waste silage in differing ratios, to form a complete diet, studying in vivo digestion, the rate of passage, microbial protein synthesis and blood metabolites. Animals were fed ad libitum with 4 diets, using four combinations of pineapple waste silage (P) and concentrate (C), in the proportions (on a dry matter basis) of 0.8:0.2 (P80:C20), 0.6:0.4 (P60:C40), 0.4:0.6 (P40:C60) and 0.2:0.8 (P20:C80). The results showed that the intakes of dry matter (DM), organic matter (OM), nitrogen (N), the N-balance, urinary purine derivatives (PD) excretion, the ratios of allantoin to creatinine (CR), PD to CR, the plasma urea-N (PUN) and insulin increased in the animals, but the intake of neutral detergent fiber (NDF), the coefficient of whole tract, apparent digestibility of NDF, the transit time (TT) and the mean retention time (TMRT) decreased, when the proportion of concentrate in the diet increased. This study indicated that the proportion of P40:C60 in the diet produced the best efficiency of urinary PD excretion (mmol) per digestible OM intake (kg DOMI).

The effects of feeding sericea lespedeza hay on growth rate of goats naturally infected with gastrointestinal nematodes1

Goat production is increasing in the United States due to high ethnic demand, but infection with gastrointestinal nematode (GIN) parasites is a major constraint to the industry. Increasing GIN resistance to chemical anthelmintics worldwide has led to the development of alternative control strategies, including use of forages containing condensed tannins (CT). An experiment was designed using infected and dewormed male kids (Kiko x Spanish, 6 mo old, 18.9 +/- 3.25 kg) fed diets containing 25% concentrate and either 75% sericea lespedeza [SL; Lespedeza cuneata (Dum-Cours.) G. Don], a high CT forage (87 to 181 g of CT/kg), or 75% bermudagrass [BG; Cynodon dactylon (L.) Pers.] hay (n = 10/treatment). The kids were weighed every 14 d, and fecal and blood samples were taken weekly for fecal egg counts and packed cell volume determination, respectively. Fecal cultures were processed every 14 d to determine CT effect on larval development. At slaughter, adult GIN were collected from the abomasum and small intestines for counting and speciation. Blood samples were also analyzed for plasma urea-N, and ruminal VFA and pH were determined. The infected SL-fed kids had consistently lower (P < 0.05) fecal egg counts than the infected BG goats throughout the trial and greater (P < 0.05) packed cell volume beginning by d 77. Average daily gain was greater (P < 0.001) in kids fed SL- than BG-based diets, regardless of infection status (104.3 +/- 5.0 and 75.5 +/- 4.8 g/d, respectively). Total VFA and acetate concentrations were greater (P < 0.001) in the BG- than in SL-fed goats, whereas propionate levels were unaffected by diet. Acetate:propionate ratio (P = 0.01) and plasma urea-N (P = 0.03) levels were greater in BG-fed goats, whereas rumen pH was greater (P < 0.001) in the SL-fed goats. Feeding SL hay can reduce GIN infection levels and increase performance of goats compared with BG hay.