Digestion, fecal, and blood variables associated with extensive large colon resection in the horse

Nutritional alterations were evaluated in 9 horses before surgery and 3 weeks, 3 months, and 6 months (4 total trials) after sham operation (group 1; n = 3) or extensive large colon resection (group 2; n = 6). Feed and fecal analyses were performed to determine apparent digestion of dry matter, organic matter, crude protein, calcium, phosphorus, magnesium, potassium, manganese, zinc, copper, and iron, and true digestion of dry matter, organic matter, crude protein, total plant cell wall, hemicellulose, cellulose, and lignin. Additional fecal and metabolic variables included the percentage of fecal water (water in the feces), total fecal water, metabolic organic matter, metabolic crude protein, and metabolic nitrogen. A CBC and standard series of biochemical tests were performed. Large colon resection decreased (P less than 0.05) the true digestion of dietary crude protein and cellulose and apparent digestion of phosphorus, and it increased the fecal metabolic matter and water loss. Total fecal output increased 45% and total fecal water increased 55%. Phosphorus digestion was decreased (P less than 0.05) in group-2 horses, but effects of this were not detected on analysis of blood variables or on physical examination. Nevertheless, after extensive large colon resection, horses can regain body weight lost after surgery and have no overt physical changes when fed an alfalfa pellet diet that meets greater-than-maintenance requirements. Ad libitum water access is suggested, because these horses may have to consume 2 gal/day more than would normal horses.     

Large colon resection

With large colon resection and anastomosis, up to 95 per cent of the length of the large colon has been successfully removed. A hand-sewn end-to-end anastomosis is effective for lesions in the left dorsal colon and pelvic flexure. Transection and a side-to-side anastomosis with stapling equipment is most effective for extensive resections (greater than 50 per cent). Horses with extensive colon resection (95 per cent) have permanent deficiencies of water absorption and digestion of cellulose and protein. Fermentative capacity is reduced, owing to decreased particulate matter retention time in the smaller capacity colon. These deficits are minimized with alfalfa hay as the source of forage (fed at 2 per cent of the body weight), and normal blood variables and body weight can be maintained. Voluntary intake increases to help maintain a positive nutrient balance. Grass hay, owing to the higher cell wall content, is inadequate as the sole source of energy and protein, and weight loss will occur. Ad libitum intake of water is recommended at all times, owing to the increased fecal water loss.     

Clinical nutrition of adult horses

Horses suffering from trauma, sepsis, and severe burns need 12% to 16% of protein (dry matter basis) in their diet. Since reduced appetite may be a problem, relatively energy dense (greater than 2 Mcal DE/kg) feeds should be offered. In hepatic failure, maintenance protein requirements (8% on a dry matter basis for adult horses) should be met with feeds that are high in short branched-chain amino acids and arginine but low in aromatic amino acids and tryptophan (for example, milo, corn, soybean, or linseed meal) in addition to grass hay. Vitamins A, C, and E should also be supplemented. In cases with renal failure, protein, calcium, and phosphorus should be restricted to maintenance or lower levels. Grass hay and corn are the best feeds for horses with reduced renal function. Do not offer free-choice salt to horses with dependent edema from uncompensated chronic heart failure. Following gastrointestinal resection, legume hay and grain mixtures are the feeds of choice. Horses with diarrhea should not be deprived or oral or enteral alimentation for prolonged periods of time. Liquid formulas may be used if bulk or gastrointestinal motility are a problem. Apple cider vinegar and a high grain diet may reduce the incidence of enteroliths in horses prone to this problem. Pelleted feeds will reduce fecal volume and produce softer feces for horses that have had rectovaginal lacerations or surgery. Horses with small intestinal dysfunction or resection should be offered low residue diets initially, but long-term maintenance requires diets that promote large intestinal digestion (alfalfa hay, vegetable oil, restricted grain). Geriatric horses (greater than 20 years old need diets similar to those recommended for horses 6 to 18 months old.     

Digestion in horses after resection or ischemic insult of the large colon

The effect of 60% resection of the large colon vs ischemic insult without resection on the ability of horses to digest grass hay was investigated. Digestion trials were performed on 9 horses before surgery (base line) and 3 weeks, 6 weeks, and 6 months after surgery. The percentage of apparent digestion of crude protein, crude fiber, nitrogen-free extract, calcium, phosphorus, magnesium, manganese, copper, and zinc was calculated. Horses that had resection (n = 5) had decreased apparent digestion of crude protein, crude fiber, and phosphorus 3 weeks after surgery, compared with those in horses with ischemic insults (n = 4) and with base-line values. Horses with ischemic insults also had a decrease in crude protein digestion 3 weeks after surgery, compared with base-line values. All horses returned to base-line values of digestion at the 6-month trials, although horses that had resection had higher fecal concentrations of phosphorus and nitrogen-free extract than did horses with ischemic insult. During the study, all horses had maintained good body condition.     

Digestibility and dry matter intake of diets containing alfalfa and kenaf

Two experiments were conducted to determine the dietary value of pellets containing kenaf (Hibiscus cannabinus cv. 'Everglade 41') hay. Averaged across both experiments, kenaf pellets contained 82.6% kenaf hay, 16.6% liquid molasses, and 0.8% mineral oil. The chemical composition of the kenaf pellet was 12.6% crude protein (CP), 41.2% neutral detergent fiber (NDF), and 14.4% acid detergent fiber (ADF). In Exp. 1 (digestion and N balance trial), 18 lambs (body weight [BW] = 36.4 kg) were blocked by BW. Lambs were randomly assigned within a block to Diet 1 (59.5% corn and 40.5% alfalfa pellet), Diet 2 (59.7% corn, 28.4% alfalfa pellets, and 11.9% kenaf pellets), or Diet 3 (59.6% corn, 16.5% alfalfa pellets, and 23.9% kenaf pellets). Diets were formulated so that CP was the first-limiting nutrient. Each diet was limit-fed at 2.4% of BW. Replacing alfalfa pellets with kenaf pellets tended to decrease (P = 0.10) CP and ADF intakes, but increased (P = 0.01) DM digestibility. Diet had no effect (P = 0.33) on N balance. In Exp. 2 (dry matter [DM] intake trial), 32 lambs (BW = 30.4 kg) were blocked by gender and BW. Within a block, lambs were randomly assigned to one of four diets in a 2 x 2 factorial arrangement. Main effects were hay (bermudagrass or fescue) and supplemental protein source (kenaf or alfalfa pellets). Lambs were housed in individual pens with ad libitum access to the assigned hay. Supplemental protein was fed (185 g of DM) once daily. Hay intake was measured weekly for 8 wk. Lambs consumed more (P = 0.002) fescue than bermudagrass hay (743 vs 621 g/ d). Lambs fed fescue hay gained weight more rapidly (P = 0.001) than lambs fed bermudagrass hay (120 vs 72 g/d). Hay intake and ADG were similar (P = 0.90) for lambs fed alfalfa or kenaf pellets. Kenaf hay mixed with molasses and mineral oil can be formed into a pellet. In the diets used in this experiments, kenaf pellets can replace alfalfa pellets in diets fed to lambs without altering forage intake, gain, or N retention.     

Nitrogen Retention and Nutrient Digestibility in Geldings Fed Grass Hay,Alfalfa Hay,or Alfalfa Cubes

This study was conducted to determine whether feeding different physical forms of hay alters nutrient digestibility and nitrogen retention (NR). Six Quarter Horse geldings were assigned to any one of three different dietary treatments in three 14-day periods. The diets included long-stem Bermuda grass hay (G), long-stem alfalfa hay (A), and alfalfa cubes (C). In the final 4 days of each period, horses were fitted with harnesses for total collection of urine and feces. Samples of feed, orts, feces, and urine were analyzed for dry matter, organic matter, acid detergent fiber, neutral detergent fiber, and nitrogen (N). Digestibility of dry matter, organic matter, and N was greatest for A, intermediate for C, and smallest for G (P < .05). Digestibility of acid detergent fiber was greater (P < .05) for A than G or C, and neutral detergent fiber digestibility was greater (P < .05) for A or G than C. Nitrogen intake (NI) was greatest for A, intermediate for C, and smallest for G (P < .05). Fecal N excretion was not different between diets, but urine N excretion was greater (P < .05) for A and C as compared with G. When expressed as a percentage of NI, NR did not differ among diets. We concluded that NR in mature horses increases with NI, but N utilization is not significantly influenced by the physical form or crude protein content of the hay fed. Potential differences in fiber digestibility and daily fecal output are factors to consider when incorporating processed forages into feeding programs of horses.     

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

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

Evaluation of alfalfa-corn cob associative action. II. Comparative tests of alfalfa hay as a source of ruminal degradable protein

The effect of ruminal degradable protein source in roughage diets on nutrient digestibility and animal growth was evaluated in two trials using lambs. In trial 1, two qualities of alfalfa and smooth brome hays replaced 0, 15, 30 or 100% of an ammonia (NH3)-treated corn cob negative control diet in a digestion trial using 26 mixed breed wethers (31.8 kg). Fifteen or 30% inclusion of hay increased (P less than .01) dry matter (DM) intake, regardless of hay type or quality. Cell wall intake was highest for 100% high quality brome hay. Positive associative action on digestibility of DM and cell walls occurred with 30% of each hay tested when diets were fed ad libitum. Measured at equal intakes, DM and cell wall digestibilities were affected by forage type X level and forage quality X level interactions (P less than .01), which showed that the magnitude of associative action was greater for 30% of high vs low quality and alfalfa vs brome hay, respectively. Magnitude of associative response on cell wall digestibility was more highly correlated to degradable N (r = .88) than cell solubles (r = .64) content of hay. In trial 2, 72 young growing lambs were allotted to three sources of supplemental ruminal degradable N (NH3, casein, corn steep liquor) superimposed upon two levels of alfalfa hay (0 or 30% of diet DM). Diets containing 0% alfalfa were supplemented with ruminal escape protein equivalent to that supplied by 30% alfalfa hay.(ABSTRACT TRUNCATED AT 250 WORDS)     

Voluntary intake and digestion of Coastal Bermuda grass hay by yearling and mature horses

Coastal Bermuda grass hay was fed as the sole source of nutrients to determine comparative voluntary intake and nutrient digestibility of hay in yearling and mature horses. Yearling horses consumed dry matter at a higher (P<.10) percentage of their body weight (2.5%) than mature horses (2.0%). digestion of hemicellulose was higher (P<.05) in mature horses, but digestion of dry matter, gross energy, neutral detergent fiber and crude protein was similar between the 2 classes of horses.     

粗饲料组合对奶牛饲粮养分消化率、能量和氮的利用的影响

本试验旨在研究粗饲料组合对奶牛饲粮养分消化率、能量和氮的利用的影响。试验采用单因素随机区组设计,将 １６头体重、年龄、胎次相近的,处于干奶期的健康荷斯坦奶牛分为 ４组,每组 ４头。以常用的粗饲料设计 Ａ（玉米青贮 ＋玉米秸秆）、Ｂ（玉米青贮 ＋羊草）、Ｃ（玉米青贮 ＋玉米秸秆 ＋羊草）、Ｄ（玉米青贮 ＋苜蓿草 ＋羊草）４种粗饲料组合的饲粮。结果表明：饲粮Ｄ干物质、有机物和中性洗涤纤维的消化率最高,显著高于其他各饲粮（Ｐ＜０．０５）,其次为饲粮Ｂ和饲粮 Ｃ,饲粮 Ａ最低,显著低于其他各饲粮（Ｐ＜０．０５）,各饲粮的酸性洗涤纤维消化率差异不显著（Ｐ＞０．０５）。粗饲料组合显著影响饲粮摄入总能、能量消化率和能量代谢率（Ｐ＜０．０５）,饲粮 Ｄ甲烷能占摄入总能比显著低于其他 ３种饲粮（Ｐ＜０．０５）。各饲粮的粪氮、尿氮占摄入总氮比差异不显著（Ｐ＞０．０５）,饲粮 Ｄ的氮消化率显著高于饲粮 Ｂ与饲粮 Ｃ（Ｐ＜０．０５）,且饲粮 Ｂ显著高于饲粮 Ａ（Ｐ＜０．０５）;饲粮 Ｂ、饲粮 Ｄ的氮利用率显著高于饲粮 Ａ（Ｐ＜０．０５）。由此可见,玉米青贮 ＋苜蓿草 ＋羊草型饲粮的养分消化率、能量和氮的利用均优于其他各饲粮,羊草与玉米秸秆之间存在正组合效应,两者搭配使用可提高玉米秸秆的消化率,优化能量和氮的利用。     

Influence of diet and water supply on mineral content and pH within the large intestine of horses with enterolithiasis

To determine the effects of two diets and water supplies on intestinal pH and mineral concentrations in the colon of horses, and to identify whether differences in these parameters exist in horses with and without enterolithiasis, surgical fistulation of the right dorsal colon was performed in six adult horses, three with and three without enterolithiasis. Each horse underwent four feeding trials: grass hay and untreated water, alfalfa hay and untreated water, grass hay with filtered/softened water, and alfalfa hay with filtered/softened water. Samples of colonic contents were analyzed for pH, dry matter, and mineral concentrations.Horses with enterolithiasis had higher calcium, magnesium, phosphorus and sulfur concentrations and higher pH in colonic contents than controls. Horses fed alfalfa had lower colonic sodium and potassium, higher calcium, magnesium, phosphorus and sulfur concentrations, and a more alkaline pH than those fed grass. Grass hay consumption leads to reduced concentrations of select minerals and a more acidic colonic environment compared with alfalfa, probably beneficial in the prevention of enterolithiasis. Under controlled dietary and management conditions, horses with enterolithiasis have differences in colonic mineral and pH parameters that may be consistent with physiological differences between horses with and without the disease.     

Nitrogen digestion and urea recycling in Hokkaido native horses fed hay‐based diets

Nitrogen (N) digestion and urea‐N metabolism in Hokkaido native horses fed roughage‐based diets containing different types and levels of protein sources were studied. Horses (173 ± 4.8 kg) fitted with an ileum cannula were fed four diets consisting of 100% timothy hay (TH), 88% TH and 12% soybean meal (SBM), 79% TH and 21% SBM, and 51% TH and 49% alfalfa hay at 2.2% of body weight. Dietary protein content varied from 5% to 15% of dry matter. Apparent N digestibilities in the pre‐cecum and total tract for the TH diet were lower than those for other diets. However, the proportion of post‐ileum N digestion to N intake was not affected by the diets. Urea‐N production was linearly related to N intake, but gut urea‐N entry was not affected by the diets. The proportion of gut urea‐N entry to urea‐N production tended to be higher for the TH diet (57%) than the two SBM diets (39%). Anabolic use of urea‐N entering the gut was not affected by the diets (20–36% of gut urea‐N entry). These results indicate that urea‐N recycling provides additional N sources for microbial fermentation in the hindgut of Hokkaido native horses fed low‐quality roughages.     

Castor beans hulls as a replacement for Tifton 85 hay in lamb diets

The objective of this study was to evaluate the effect of replacing Tifton 85 hay (0, 33, 66, or 100 %) with by castor bean hulls on the intake and nutrient digestibility and performance of 28 noncastrated lambs, averaging 7 months in age, 19.5?±?2.0 kg average live weight, fed on diets based on forage cactus. The animals were housed in individual pens for 100 days. The digestibility trial occurred 40 days after the start of the performance using LIPE® as an external indicator for estimating fecal dry matter production. The replacement of hay with Castor beans hulls linearly decreased the intakes of dry matter, neutral detergent fiber, organic matter, and crude protein and reduced the digestibility coefficients of the dry matter, neutral detergent fiber, organic matter content, crude protein, and total digestible nutrient content. The hot carcass and true carcass yields were not influenced by the treatments and the feed conversion increased linearly. The empty body weight, live weight at slaughter, hot and cold carcass weights, total gain, and average daily gain decreased linearly with the replacement. The replacement of Tifton 85 hay with castor bean hulls reduced the intake of dry matter, crude protein and energy, consequently reducing the performance of the animals. However, as the regression coefficients were of low magnitude, data were subjected to analysis of variance and means were compared using the Dunnett test with diet without castor bean hulls set as the control treatment. The Tifton 85 hay can be replaced up to 66 % by castor bean hulls in finishing diets for lambs.     

Effect of Yeast Culture Supplementation on Digestibility of Varying Forage Quality in Mature Horses

Supplementation of yeast culture to equine diets has improved digestion of nutrients in some studies but not others. Improving the digestibility of lower-quality forages could be advantageous both for the producer and for the horse's health. The objective of this study was to evaluate the effect of yeast culture on digestibility of high- and low-quality forage in mature horses. Sixteen geldings (483.6 ± 25.5 kg and 6.8 ± 3.2 years), of Quarter Horse (n = 14) and Thoroughbred (n = 2) breeding, were used in a 4 × 4 Latin square design with 28-day treatment periods. Russell Bermuda grass hay of either high (13.1% crude protein (CP), 73.1% neutral detergent fiber (NDF), 35.3% acid detergent fiber (ADF), and 6.0% ash) or low (8.1% CP, 75.3% NDF, 37.6% ADF, and 4.3% ash) quality was offered at 1.35% of body weight (BW, dry matter [DM] basis). Diets consisted of high-quality forage with the addition of yeast culture (HY), high-quality forage without yeast culture (HC), low-quality forage with the addition of yeast culture (LY), and low-quality forage without yeast culture (LC). All horses were fed a commercial grain mix (12.6% CP, 25.4% NDF, 12.1% ADF, and 4.0% ash) offered at 0.45% of BW (DM basis) daily. Yeast culture was added to the grain mix during the morning feeding at a rate of 56 g per horse. Body weight was measured weekly and feed intake was adjusted accordingly. Fecal samples were obtained every 6 hours on the last 3 days of each treatment period. Horses receiving low-quality hay (LY and LC) had greater (P < .01) intake expressed as a percentage of BW compared with horses receiving high-quality hay (HY and HC). No influence of yeast culture supplementation was seen on intake of grain or forage (P < .23 and P < .62, respectively). Digestibility of DM, organic matter (OM), CP, and NDF were greater (P < .01, P < .01, P < .01, and P < .01, respectively) for the diets with high-quality forage compared with the diets with low-quality forage. Dry matter, CP, and NDF digestibilities were greater (P < .09, P < .03, and P < .05, respectively) for horses receiving LY compared with LC. Supplementation of yeast culture to mature horses improved digestibility of lower-quality Bermuda grass hay.     

饮用磁化水对饲喂颗粒日粮绵羊消化代谢的影响

为研究饮用磁化水对饲喂颗粒日粮绵羊消化代谢的影响,本研究设计了2个试验:试验1:选取4只约1.5岁、体重(44.7±1.8)kg的小尾寒羊公羊,采用4×4拉丁方设计,每期每只羊分别饲喂粉碎日粮(处理1)、粉碎日粮+磁化水(处理2)、颗粒日粮(处理3)及颗粒日粮+磁化水(处理4),研究饲喂粉碎、颗粒两种日粮条件下饮用磁化水对绵羊自由采食和消化代谢的影响;试验2:选取6只约1.5岁、体重(46.3±2.1)kg的小尾寒羊空怀母羊,采用3×3拉丁方设计,每期每组饲喂相同的颗粒日粮,处理1:自由采食;处理2:在自由采食条件下饮用磁化水;处理3:在限饲(相当于处理1的喂量)条件下饮用磁化水,研究饮用磁化水时限饲对绵羊消化代谢的影响。结果显示:(1)在试验1中,饮用磁化水组绵羊的干物质自由采食量,干物质、粗蛋白质和总能表观消化率及氮保留量较饲喂粉碎日粮时分别提高14.7%(P<0.05)、2.6%(P>0.05)、2.2%(P>0.05)、2.2%(P>0.05)和22.7%(P<0.01);在饲喂颗粒日粮时分别提高14.3%(P<0.05)、4.2%(P<0.05)、4.8%(P<0.05)、6.0%(P<0.01)和14.2%(P<0.05)。(2)在试验2中,饮用磁化水时限饲母羊的干物质、有机物、粗蛋白质、纤维素、半纤维素、不可酶解纤维素和半纤维素、总能表观消化率及氮保留量较自由采食时分别提高19.1%、19.0%、9.7%、18.4%、16.2%、341.5%、226.7%、17.4%和14.8%,均差异极显著(P<0.01)。综上所述,在饲喂颗粒日粮的基础上饮用磁化水时,绵羊干物质自由采食量可进一步提高;自由采食条件下饮用磁化水不影响饲喂粉碎日粮绵羊日粮消化率,但可提高饲喂颗粒日粮绵羊干物质、粗蛋白质和能量的表观消化率,且氮保留量显著增加;限饲条件下饮用磁化水可显著提高饲喂颗粒日粮绵羊日粮营养物质消化率。     

Effect of supplemental niacin or niacinamide and soybean source on ruminal bacterial fermentation in continuous culture

Effects of niacin or niacinamide in diets containing either soybean meal, raw whole soybeans or whole soybeans extruded at 132 and 149 C on ruminal bacterial fermentation were examined with a dual-flow continuous culture system. In Exp. 1, soybean sources each provided 50% of total crude protein in diets comprised of 52% concentrate mix, 36% corn silage and 12% alfalfa hay (dry-matter basis). Each diet was supplemented with 0 or 100 mg/kg niacin. Niacin supplementation increased (P less than .05) total nonstructural carbohydrate digestibility and lowered (P less than .05) butyrate concentration. There was also an increase (P less than .10) in amino acid effluent flow from 8,413.3 to 8,665.3 mg/d with addition of niacin to the diet. In Exp. 2, diets were supplemented with 0 or 100 mg/kg of niacin or niacinamide. The total mixed diet was comprised of 60% concentrate mix, 20% corn silage and 20% alfalfa hay (dry matter basis). Acid detergent fiber and cellulose digestibilities and total amino acid effluent flow were higher (P less than .10) with niacinamide supplementation. Niacin or niacinamide had no effect on dry matter and organic matter digestibilities, ammonia-N, total VFA concentration or crude protein degradation. Contrary to results found in other studies, niacin or niacinamide supplementation had no effect on bacterial protein synthesis.     

Renal energy excretion of horses depends on renal hippuric acid and nitrogen excretion

The prediction of renal energy excretion is crucial in a metabolizable energy system for horses. Phenolic acids from forage cell walls may affect renal energy losses by increasing hippuric acid excretion. Therefore, the relationships were investigated between renal energy, nitrogen (N) and hippuric acid excretion of four adult ponies (230–384 kg body weight (BW)) consuming diets based on fresh grass, grass silage, grass cobs (heat‐dried, finely chopped, pressed grass), alfalfa hay, straw, extruded straw and soybean meal. Feed intake was measured; urine and faeces were quantitatively collected for three days. Feed was analysed for crude nutrients, gross energy, amino acids and neutral‐detergent‐insoluble crude protein (CP); faeces were analysed for crude nutrients and cross energy; urine was analysed for N, hippuric acid, creatinine and gross energy. Renal energy excretion (y; kJ/kg BW^0.75) correlated with renal N excretion (x₁; g/kg BW^0.75) and renal hippuric acid excretion (x₂; g/kg BW^0.75): y = 14.4 + 30.2x₁+20.7x₂ (r = .95; n = 30; p < .05). Renal hippuric acid excretion was highest after intake of fresh grass and lowest after intake of soybean meal. The ratio of hippuric acid to creatinine in urine and the excretion of hippuric acid per gram of dry matter intake was significantly higher for fresh grass than for all other rations. There was no relationship between aromatic amino acid intake and renal hippuric acid excretion. The results of the present study and literature data suggest that feed can be categorized into four groups with regard to the energy losses per gram CP intake: (i) protein supplements (e.g., soybean meal): 4.2–4.9 kJ/g CP intake (ii) alfalfa hay, grains, dried sugar beet pulp: 6.4 kJ/g CP intake, (iii) hay, preserved grass products, straw: 5.2–12.3 kJ/g CP intake (mean 8) and (iv) fresh grass. For group (iii) a negative relationship was observed between renal energy losses per gram of CP and the content of CP or neutral‐detergent‐insoluble CP in dry matter.     

The particulate passage rate,nutrient composition and fermentation characteristics across gastrointestinal tracts in lactating dairy cows fed three different forage source diets

This study was conducted to investigate the particulate passage rate, nutrient characteristics and fermentation parameters across the gastrointestinal tract (GIT) in lactating dairy cows fed cereal straws in comparison with alfalfa hay. Eighteen multiparous Holstein cows were randomly assigned to one of three experimental diets consisting of 55% concentrate, 15% corn silage and 30% different forage sources as follows (% of dry matter [DM]): (i) 23% alfalfa hay and 7% Chinese wild rye hay (AH); (ii) 30% corn stover (CS); and (iii) 30% rice straw (RS). The Cr‐mordanted corn silage‐neutral detergent fibre was used to estimate the passage flow at week 14. After 14‐week feeding, the animals were slaughtered to collect the gastrointestinal digesta. Dietary forage sources had little effect on the fractional passage rates in the rumen (range from 5.05 to 6.25%/hr) or hindgut (range from 4.49 to 5.24%/hr). Total volatile fatty acid (VFA) concentration in the caecum was highest, followed by the rumen, colon and rectum, and the lowest in the abomasum and duodenum, indicating that the large intestines, especially caecum, are the important positions for carbohydrate degradation. Greater proportion of propionate and butyrate and lower acetate were found in the AH compared to CS or RS in colon, but higher acetate in abomasum was found in the cows fed CS or RS compared to AH. In conclusion, cereal straw diets did not change the particulate passage rate in the rumen and hindgut which might be mainly due to the similar DM intake among these three diets. Different forage source diets significantly changed VFA proportion in the abomasum and colon, indicating the existence of different digestion or absorption rates in these tracts among the experimental diets.     

Nutritive value of a vegetable amaranth cultivar for growing lambs

Current interest in amaranth as a food resource for humans and animals has been stimulated by activities in germplasm collection and testing in the U.S. Fifteen growing, intact male lambs weighing 18.7 kg were assigned randomly to three diets (five lambs/diet) for a 14-d growth trial followed immediately by an 8-d (4-d adjustment, 4-d collection) digestion and N balance trial to determine the utilization of the forage component (leaves and stems) of an African cultivar (Zimbabwe cultivar PI 482049, Amaranthus cruentus L.) All diets contained 40.95% ground corn, 8.0% soybean meal and 1.05% mineral-vitamin supplement plus either 50% ground alfalfa hay, 25% ground alfalfa hay plus 25% ground amaranth forage or 50% ground amaranth forage. Lambs had ad libitum access to feed during the growth trial and at 4% of BW daily during the digestion and N balance period. Replacement of half or all the alfalfa in the diet with amaranth had no effect on weight gain or feed utilization. Apparent digestibility of cell contents, NDF, ADF, cellulose, ADL, N and GE and percentage of absorbed N retained did not differ among the three diets. The amaranth vegetable cultivar Zimbabwe PI 482049 promoted weight gain and feed utilization equal to that obtained with alfalfa as the sole forage for growing lambs. Additional research is needed to evaluate further the potential role of forage/vegetable amaranth as an animal feed resource.     

Alkanes as internal markers to estimate digestibility of hay or hay plus concentrate diets in horses.

Dry matter intake (DMI), dry matter digestibility (DMD), and fecal output (FO) are difficult to measure directly in the field, and indirect methods using external and internal markers have thus been developed. An experiment was conducted consisting of two digestion trials with two periods in each trial to examine the use of five odd-chain alkanes (C25 to C33) of plant cuticular wax as internal markers to estimate DMD of hay or hay plus concentrate diets in horses. Eight mature Thoroughbred geldings were housed in 4- x 4-m stalls and randomly assigned to one of two mixed grass/legume hays (Diets 1 and 2) in Trial 1 and to mixed grass/legume hay plus one of two concentrates (Diets 3 and 4) in Trial 2. After the first 12-d period was conducted, dietary assignments for each group were switched for the second period in each trial. Each period consisted of a dietary accommodation from d 1 to 7 and total fecal collection from d 8 to 11. Results indicated that fecal recoveries of odd-chain alkanes were 88 to 90% for Diet 1, 75 to 92% for Diet 2, 71 to 81% for Diet 3, and 71 to 82% for Diet 4. Alkane recoveries were not related to alkane chain lengths. Digestibilities calculated from alkane concentration data adjusted using the mean fecal recovery of individual odd-chain alkanes (DA1) were not significantly different from the digestibilities estimated from total collection (DTC) for Diets 1 and 2 in Trial 1 and Diets 3 and 4 in Trial 2. When adjustment was based on the mean recovery of all alkanes (DA2; estimated by linear regression), all DA2 estimates for horses offered all diets were similar to DTC. Results indicate that accurate mean estimates of DMD can be obtained by using plant wax alkane markers and adjusting for the mean recovery of five odd-chain alkanes in a diet.