Condensed Tannin and Saponin Content of Vigna unguiculata (L.) Walp,Desmodium uncinatum,Stylosanthes guianensis and Stylosanthes scabra Grown in Zimbabwe

Samples of the tropical forage legumes Vigna unguiculata (L.) Walp (cowpea), Desmodium uncinatum (silverleaf desmodium), Stylosanthes guianensis (oxley fine stem stylo) and Stylosanthes scabra (fitzroy) and of natural pasture (veld) hay were analysed and ranked according to their proanthocyanidin (PA) and saponin content. Silverleaf desmodium and fitzroy leaf and stem samples of different ages were also separately analysed for the PA contents. All the samples analysed contained some PA but no saponins. High levels of PA were detected in silverleaf desmodium and very low levels in veld hay and cowpea. In all samples, more of the tannins were bound to protein or neutral detergent fibre (NDF) than were extractable, most being bound to proteins. The proportion of the unextractable PA was greater in younger than in mature materials.     

Apparent digestibility and microbial protein yield of Desmodium uncinatum,Mucuna pruriens and Vigna unguiculata forage legumes in goats

This study examined the effects of adding forage legumes as protein supplements to poor-quality natural pasture (veld) hay offered to goats on microbial protein yield and nitrogen metabolism. Four indigenous Nguni-type goats were used in a 4×4 Latin cross-over design experiment. Goats were randomly allocated to four dietary treatments comprising commercial goat feed (GF), veld hay supplemented with cowpea (CW), velvetbean (VB) or silverleaf desmodium (SD). Microbial protein yields were determined using the purine derivatives technique and nitrogen retention was calculated from the digestible organic matter intake. Total nitrogen intake was significantly higher in the GF followed by CW, SD and VB, respectively. Microbial protein supply, calculated microbial true protein and digestible microbial true protein were affected (P<0.05) by legume supplementation. Animals on poor-quality forages had the most efficient microbial protein synthesis. However, supplementation of hay failed to meet the maintenance requirements of animals as evidenced by negative nitrogen balances in VB and SD. The efficiency of utilisation of nitrogen in the supplements could have been limited by unavailable fermentable metabolisable energy in the diets. Supplementation of poor-quality veld hay with legume forages could improve utilisation, especially in the dry season.     

The potential of replacing conventional dairy supplements with forage legume-based diets in Zimbabwe’s smallholder dairy sector

The effect of replacing commercial supplements with isoenergetic and isonitrogenous velvet bean-, cowpeaand lablab-based supplements on milk yield, milk quality and economic returns in smallholder crossbred dairy cows was investigated in the 2013 and 2014 dry seasons. Using 3 × 3 Latin square designs, nine multiparous Red Dane, Guernsey and Holstein-Friesian crosses in mid-lactation (130 ± 19 d) were offered forage legume-based supplements for 63 d at 0.5 kg per litre of milk produced. Milk quantity and quality were significantly (P < 0.05) different among supplements in both seasons. Cows fed commercial supplements had higher milk yield than cows fed forage legume supplements. Milk fat content was significantly (p < 0.05) higher in cows fed lablab-based supplements than cows fed other supplements. Milk protein, total solids and lactose content of cows fed commercial supplements was significantly (p < 0.05) higher than those fed forage legume-based supplements, although protein content was similar to cows fed lablab-based supplements. Dietary gross margins were higher for cows fed velvet beanand lablab-based supplements by 17% and 16.5%, respectively. Based on supplement, production costs per litre of milk was higher by 28% and 23% using commercial supplements compared to velvet bean and lablab supplements, respectively.     

Effect of mixed maize-legume silages on milk quality and quantity from lactating smallholder dairy cows

The study investigated the effect of the following maize:legume (70:30) mixed crop silages: maize:cowpea, maize:velvet bean, and maize:lablab on milk production during the 2016 dry season. Using a 5?×?5 double Latin square design, five Holstein-Friesian crossbred cows in early lactation (30?±?15 days) and five Jersey crossbred cows in early lactation (25?±?10 days) were given the supplementary mixed crop silage diets at 0.5 kg/l of milk produced over 105 days. Commercial dairy meal and sole maize silage were used as positive and negative controls, respectively. Milk yield was significantly higher (P?< 0.05) in cows given the dairy meal compared to mixed crop silages; however, milk yield was also significantly higher (P?< 0.05) for cows given the three mixed crop silages compared to cows given sole maize silage. Cows given mixed crop silages produced milk of significantly higher protein content (P?< 0.05) than those given sole maize silage. There was no significant difference (P?> 0.05) in butterfat content of milk across all the dietary treatments. The dietary cost of producing 1 l of milk was highest at 0.31USD/l for cows given commercial dairy meal and lowest for cows given maize:velvet bean and maize:cowpea silage at 0.19USD/kg. The highest dietary gross margins of 68% were observed when cows were given maize:velvet mixed silage compared to commercial dairy meal (47%) and sole maize silage (57%). The 70:30 maize:legume mixed crop silages showed the capability to increase milk quantity and quality at very low production costs in smallholder dairy schemes.     

Profile of digested feed amino acids from untreated and expander treated feeds estimated using in situ methods in dairy cows

Guar meal, sunflower meal, rapeseed cake, peas, maize, rye, wheat and barley were subjected to expander treatment at different temperatures (95–150 °C), and effect on amino acid availability was assessed using rumen nylon bag and mobile bagin situ methods. Expander treatment of rapeseed cake at 142 °C decreased feed lysine content, probably due to formation of complex compounds. Effective rumen degradability and total tract digestibility of protein, total amino acids, lysine, methionine, threonine, isoleucine, leucine, valine, and phenylalanine were compared to values for the untreated feeds. Effective rumen degradability seemed to decrease due to expander treatment for all cereals, except maize. Effective rumen degradability for sunflower meal and rapeseed cake was unaffected by expander treatment at 115 °C, whereas expander treatment at 142 °C appeared to decreased effective rumen degradability for rapeseed meal. Total amino acid digestibility was not decreased by expander treatment. Both for untreated and heat treated feeds rumen degradability and total tract digestibility of individual amino acids were generally in agreement with results for crude protein. Observed amino acid profiles supplied by digestible rumen undegraded feed amino acids were compared to a theoretical optimal profile obtained from the literature using a χ²-index. A low index is equivalent to a high biological value. Smallest and largest index for the difference between the observed and theoretical optimal amino acid profile were obtained for peas and maize, respectively. Lysine was the first limiting amino acid for cereals, sunflower meal, expander treated (142 °C) rapeseed cake and untreated guar meal, leucine for untreated and expander treated (115 °C) rapeseed cake, and methionine for peas and expander treated guar meal. It was concluded that based on the assumed ideal amino acid profile, expander treatment only changed the first limiting amino acid for rapeseed cake and guar meal, and that although expander treatment decreased the index, and thereby improved the biological value of the intestinally digested feed amino acids, the ranking of feeds based on the index was unaffected by expander treatment.     

Dairy cows fed on tropical legume forages: effects on milk yield,nutrients use efficiency and profitability

Two trials with multiparous dairy cows were conducted. Experiment 1 tested the effects of increasing forage proportion in the diet (500, 600, and 700 g/kg DM) when a mixed sorghum (Sorghum bicolor) and jackbean (Cannavalia ensiformis) silage was used as forage. Experiment 2 studied the substitution of sorghum silage and soybean meal by jackbean silage or fresh cowpea (Vigna unguiculata) forage in the diet. All diets were iso-energetic and iso-proteic. In each experiment, 30 cows were used and separated into three groups. In experiment 1, there were no differences in dry matter intake (DMI), milk yield (MY), or apparent total tract digestibility (aTTd) among the three diets, but milk fat content increased with increasing forage proportion, even though the similar neutral detergent fiber of all diets. Nitrogen use efficiency was highest in the diet containing 600 g forage/kg DM, and some evidence was observed for a better profitability with this forage proportion. In experiment 2, feeding legumes increased DMI despite no effects on aTTd. Milk yield increased in line with DMI, with a larger increase for the fresh cowpea. Nitrogen use efficiency and milk composition were not affected by the diets. The increased MY and lower feed costs increased the economic benefits when feeding legumes, particularly when feeding fresh cowpea. Feeding fresh cowpea or jackbean silage to dairy cows appears to be an alternative to soybean as protein source, ideally at a forage proportions of 600 g/kg DM, without altering milk yield and quality and increasing the farm profitability.     

Cell wall degradation of tropical and temperate forage grasses measured by nylon bag and in vitro digestion techniques

Four tropical and four temperate grasses were subjected to nylon bag fiber degradation study with fistulated Holstein cattle as well as in vitro digestion with broad spectrum cellulase, and the degradability of cell wall carbohydrate and lignin for the respective forage grasses were determined. The degradability of neutral detergent fiber and acid detergent fiber for the same plant materials appeared to be similar, but that of acid detergent lignin was constantly lower. As for the plant materials used in the present study, Italian ryegrass, orchardgrass and guineagrass showed high degradability of fibers in nylon bag incubation, while setaria, cogongrass and wheat showed smaller degradability. In both nylon bag incubation and in vitro digestion experiments, the forage samples showing relatively lower degradability exhibited notably lower disappearance of xylose than that of glucose or arabinose. It was also observed that dry matter degradability correlated negatively with the initial content of esterified and/or etherified p‐coumaric acid. These results were assumed to be caused by the difference in resistance towards rumen microbial degradation due to the concentration of lignin‐carbohydrate complex.     

裹包全混合日粮瘤胃降解特性的研究

试验选用2头安装有永久性瘤胃瘘管的荷斯坦奶牛作为试验动物,采用尼龙袋法研究了裹包贮存、精粗比和水分含量对全混合日粮(TMR)营养成分瘤胃降解特性的影响。结果表明:裹包贮存可显著提高TMR饲料干物质(DM)、粗蛋白(CP)和中性洗涤纤维(NDF)的瘤胃消失率和有效降解率(P0.05)。DM和CP的瘤胃消失率及有效降解率随TMR饲料精料水平的提高显著增加(P0.05)。水分含量60%组TMR饲料中CP的有效降解率显著高于40%和50%组(P0.05),40%和50%组间差异不显著(P0.05)。因此,裹包贮存可提高TMR饲料中营养物质瘤胃消失率和有效降解率(P0.05),营养物质的瘤胃消失率和有效降解率随TMR饲料精粗比的增加而增加,水分含量对裹包TMR中不同营养物质的消失率和有效降解率有不同影响。     

Energy Supply to Livestock from Tropical Rangeland during the Dry Season

Nine key forage species (grasses and legumes), together with two types of crop residues, usually fed by farmers to their livestock, were collected from a rainfed area in western Sudan during the dry season (May–April). The grasses investigated were Leptadena pyrotechnia, Cenchrus setigrus, Arista pallida, Eragrotis tremula, Schoenefeldia gracilis, Chloris vergata and Cenchrus biflorus. The crop residues investigated were the grasses, sorghum straw (Sorghum bichlor) and millet straw (Pennisetum typhodium) and the legumes Stylosanthes flavicans and Cajanus cajana. Estimates of organic matter (OM) degradability were done using the nylon bag technique, which was fitted into the model Y = a + b (1 – e^–ct), in which the asymptote (a + b) represented the total potential degradability. Organic cell wall constituents and hence both metabolizable energy and total digestible energy or nutrients (TDN) were determined. S. flavicans showed the best organic matter degradability, and sorghum straw was better degraded than millet straw. The rest of the grasses showed poor OM degradability. Acid detergent insoluble nitrogen was inversely related to TDN, the latter falling within a narrow range for the different forages. Fermentable metabolizable energy differed only slightly, while the legume S. flavicans had the highest effective rumen digestible protein. Undegraded proteins were high for the straws and the grasses L. pyrotechnia and C. setigerus. Metabolizable protein and microbial protein were highest in the sorghum straw, C. setigerus and S. flavicans.     

Nutritive evaluation of legume seeds for ruminant feeding

Chemical composition, rumen degradability and the effect of particle losses, and intestinal digestibility of protein by using in situ‐in vitro and in vitro techniques were stated for beans (Vicia faba), lupin (Lupinus albus), vetch (Vicia sativa) and bitter vetch (Vicia ervilia) and four diets including those legume seeds. In addition, the apparent digestibility of experimental diets was determined in goats. The legume seeds showed high protein content (206–319 g/kg dry matter). Effective degradability of protein for legumes and diets varied from 0.80 to 0.87 and 0.76 to 0.82, respectively, decreasing to 0.53–0.76 and 0.61–0.67, respectively, when particle loss was taken into account. Different intestinal digestibility values were obtained with both methodologies without significant relationship between them (y = 1.058–0.463x; R² = 0.068; RSD = 0.140; p = 0.53). There were no differences in the apparent nutrients and energy digestibility among diets (p > 0.05). These legumes can supply rapidly degradable protein for microbial protein synthesis and contribute to the pool of amino acids available for the synthesis of milk protein and for retention in the body.     

Effect of Adding Different Mannan Oligosaccharide to Diets with Different Concentrate to Forage Ratios on Rumen Degradability of Fiber in Sheep

To investigate the effect of adding mannan oligosaccharide to diets with different concentrate to forage ratios on the degradability of neutral detergent fiber (NDF) and acid detergent fiber(ADF) in rumen of sheep by nylon bags technique,6 wethers (White Suffolk♂×Small-tailed Han sheep♀) installed permanent rumen fistula were used for offering rumen fluid.The 4×6 two-factor experimental design was chosen and the two factors were the ratio of concentrate to forage (A1(20:80),A2(30:70),A3(40:60),A4(50:50)) and the dose of mannan oligosaccharide (B1 (0),B2 (0.4%),B3 (0.8%),B4 (1.2%),B5 (1.6%),B6 (2.0%)).The results showed that the rumen degradability of NDF and ADF in different times,degradation parameters and effective degradability were influenced by the factor A significantly (P< 0.05).The rumen degradability of NDF and ADF in each time of group A1 were higher than group A3 and A4 (P< 0.05).Expect for 24 h,the rumen degradability of ADF were influenced significantly by the factor B,and the rumen degradability of ADF in group B5 was higher than group B1 and B2 (P< 0.05).The rumen effective degradability of NDF in group A3 was significantly higher than groups A1 and A2 (P< 0.05), and a little higher than group A4 (P >0.05),which showed that the rumen effective degradability of NDF and ADF were higher when the ratio of concentrate to forage was 40:60.     

不同精粗比日粮添加甘露寡糖对绵羊瘤胃纤维降解率的影响

选取6只安装永久瘤胃瘘管羯羊(白萨福克♂×小尾寒羊♀)为瘤胃液供试动物,采用4×6二因子析因试验设计,共设2个因子,分别为不同精粗比日粮(A1(20:80)、A2(30:70)、A3(40:60)、A4(50:50))和不同甘露寡糖添加量(B1 (0)、B2 (0.4%)、B3 (0.8%)、B4 (1.2%)、B5 (1.6%)、B6 (2.0%)),进行尼龙袋半体内试验,旨在研究不同精粗比日粮中添加甘露寡糖对绵羊瘤胃中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)降解率的影响。结果表明,A因子对日粮中不同时间点NDF、ADF瘤胃降解率、降解参数及有效降解率均产生了显著影响(P< 0.05),A1处理组的NDF和ADF各个时间点(除3 h外)的瘤胃降解率均显著高于A3和A4处理组(P< 0.05);B因子对3、6、9、12、48 h的瘤胃ADF降解率均产生了显著影响(P< 0.05),其中B5处理组显著高于B1、B2处理组(P< 0.05);A3处理组的NDF有效降解率显著高于A1、A2处理组(P< 0.05),稍高于A4处理组(P >0.05)。综上所述,在精粗比为40:60时,NDF和ADF的瘤胃有效降解率处于较高水平。     

Digestibility, methane production and nitrogen balance in sheep fed ensiled or fresh mixtures of sorghum–soybean forage

The feeding value of a mixture of sorghum and soybeans plants, either fresh or ensiled, was evaluated with sheep. Sorghum and soybeans were harvested during the Cuban rainy season and ensiled in a ratio of 0.6/0.4 (w/w, as feed) with molasses and a bacterial inoculant. Silos were opened between 162 and 182 d post ensiling during the Cuban dry season and silages were fed to six pelibuey sheep (including two fistulated). Six other sheep (also including two fistulated) were fed sorghum and soybean in the same proportion, but freshly harvested during the dry season. The experiment lasted 21 d (14 d adaptation and 7 d data collection period). Silage quality parameters included pH, ammonia, lactate, and short chain fatty acids (SCFA). Further, both fresh and ensiled diets were offered to study the rumen fermentation characteristics (pH, ammonia, lactate, SCFA, in situ degradability and methane), duodenal flow of microbial protein (assessed through urinary purine derivatives secretion), fecal degradability of nutrients and urinary N excretion. From these measurements ME value and degradable CP supply at the small intestine (DCPSI) were estimated. Silage was of excellent quality. Compared to fresh forage feeding silage increased molar propionate proportion and rumen microbial protein synthesis and reduced methane emission. Fresh forage showed lower rumen degradability and total digestibility. Further, the higher ME concentration (11.2 vs. 10.3 MJ/kg DM) and DCPSI (84.7 vs. 56.1 g/kg DM) of the silage would allow a higher milk production or daily gain as compared with fresh forage available during the Cuban dry season.     

Efficiency of utilisation of different diets with contrasting forages and concentrate when fed to sheep in a discontinuous feeding pattern

The effects of feeding different levels of forages and concentrate, in a discontinuous feeding pattern, on the efficiency of feed utilisation and rumen function were studied using rumen fistulated sheep. Experiment 1 was a 4 × 4 latin square design to determine the whole tract digestibility and rumen characteristics of diets comprising 15% (C15), 25% (C25), 35% (C35) and 45% (C45) concentrate (energy-dense dairy pellets) with the rest of the diet being a combination of fresh short rotation ryegrass (Lolium mutiforum) and conserved (lucerne hay and maize silage) forages. In Experiment 2, the rumen degradation characteristics of feed ingredients were determined using the nylon bag technique. Daily dry matter intake (either expressed as g/kg LW or g/kg W ^0.75) was 10% lower (p = 0.03) for the C15 diet compared with C25, C35 and C45 diets. The apparent in vivo digestibility of dry matter (DM) for C15 diet was 4% higher (p = 0.04) than the C35 and C45 diets which may be attributed to the high quality of the forage (ryegrass) used.Fibre digestibility decreased as proportion of concentrate in the diet increased. However, this was unlikely due to changes in the rumen fermentation pattern, as neither pH (6.1 ± 0.23) nor ammonia concentration (24.4 ± 6 mg/dl), were different (p > 0.05) among diets. Instead, the lower fibre digestion was most likely the result of different type and proportion of fibre among diets, as total rumen degradability and rate of fibre degradation in the rumen were higher (p = 0.001) for ryegrass than for other feedstuffs. There was no significant difference in total nitrogen balance and urinary allantoin excretion among diets, which indicated similar total microbial protein synthesis (MPS). The asynchrony observed, for N and energy availability in the rumen for different diets using Sinclair et al. [Sinclair, L.A., Garnsworthy, P.C., Newbold, J.R., Buttery, P.J., 1993. Effect of synchronizing the rate of dietary energy and nitrogen release on rumen fermentation and microbial protein synthesis in sheep. J. Agric. Sci. 120, 251–263] equation, was due to the feeding pattern used in this study leading to excess of N in relation to total organic matter digested in the rumen. In conclusion, feeding concentrates in the diets as PMR with conserved forages in a discontinuous feeding pattern may be valuable to develop feeding strategies in a pasture based system for high producing dairy cows without affecting the rumen system.     

Effects of forage offering method on performance,rumen fermentation,nutrient digestibility and nutritional behaviour in Holstein dairy calves

The potential effect of dietary forage supplementation on the performance and rumen development in dairy calves is well established. However, limited research has been directed to the comparative effects of forage offering methods on calf performance. The objective of the present study was to determine the effects of forage provision methods (total mixed ration or free choice) on the performance, nutrient digestibility, rumen fermentation and nutritional behaviour in newborn calves. Forty‐five Holstein dairy calves (3 days of age and 41 ± 2 kg of body weight) were assigned to the following three groups (n = 15): (i) starter without forage provision (CON), (ii) starter supplemented with 10% alfalfa hay (AH) as a total mixed ration (AH‐TMR) and (iii) starter and AH as a free‐choice provision (AH‐FC) for a period of 70 days. All the calves were offered 5 l of milk/day from day 3 to 50, and 2.5 l/day from day 50 until weaning on day 56. Dry matter intake (DMI) was greater (p < 0.01) in the AH‐TMR and AH‐FC treatments than in the CON during the pre‐ and post‐weaning periods. Calves fed the AH‐FC diet showed the highest post‐weaning DMI among the treatments. The calves receiving ad libitum forage tended (p = 0.08) to increase crude protein digestibility and overall volatile fatty acids (VFA) concentrations in the rumen. No differences were observed among the treatments at the time spent on standing, lying, eating and performing non‐nutritive oral behaviours. Compared to CON calves, animals in the AH‐TMR treatment spent more time (p < 0.05) ruminating. In conclusion, our data suggest that forage supplementation in both forage offering methods increased total DMI, ruminal pH and ruminating time in dairy calves. Hence, there is no benefit in the free‐choice provision of AH in dairy calves.     

Dry Matter and Crude Protein Degradability of Four Parasitic Plants (Mistletoes) Associated with Browse Trees in Botswana

Four parasitic plants (Tapinanthus lugardii, Erianthenum ngamicum, Viscum rotundifolium and Viscum verrucosum) associated with browse trees in Botswana were evaluated for the degradability of their dry matter (DM) and crude protein (CP). All these plants have high levels of crude protein, ranging from 144.5 to 163.4 g/kg DM, with a significant (p<0.001) difference in crude protein content between the plants. The rate of degradation of DM was highest for V. rotundifolium (0.197 h⁻¹) and lowest for E. ngamicum (0.031 h⁻¹). The two Viscum species had the highest effective DM degradability at an outflow rate of 0.05%. The rate of degradation of crude protein was highest for V. rotundifolium (0.144 h⁻¹) and lowest for T. lugardii (0.0346 h⁻¹). The effective degradability (ED) of crude protein was highest for V. rotundifolium at 0.03 and 0.05 h⁻¹ outflow rates. T. lugardii and E. ngamicum had an apparently low effective degradability, but this may result from an association of their protein with tannins, which would be able to supply amino acids in the small intestine after dissociation due to the abomasal pH. This revised version was published online in July 2006 with corrections to the Cover Date.     

常规与非常规粗饲料在奶牛瘤胃中的降解特性研究

旨在探讨非常规粗饲料(玉米芯、毛豆荚壳)与奶牛常用粗饲料(苜蓿干草、玉米青贮)在奶牛瘤胃中的降解规律,试验选用3只装有永久性瘤胃瘘管的荷斯坦奶牛,采用尼龙袋法测定4种粗饲料的干物质(DM)、粗蛋白(CP)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的瘤胃降解规律。结果表明:1)苜蓿干草和毛豆荚壳的CP含量分别为17.55%和11.10%,且苜蓿干草显著高于毛豆荚壳(P<0.05);玉米芯和玉米青贮的CP含量分别为2.97%和8.41%,且玉米芯显著低于玉米青贮(P<0.05);玉米芯的NDF和ADF含量显著高于其他3种粗饲料(P<0.05),达到79.98%和43.35%。2)苜蓿干草的DM有效降解率最高(P<0.05),由高到低依次为苜蓿干草、毛豆荚壳、玉米青贮和玉米芯。毛豆荚壳的CP有效降解率显著高于其他3种粗饲料(P<0.05),由高到低依次为毛豆荚壳、苜蓿干草、玉米青贮和玉米芯。苜蓿干草的NDF有效降解率显著高于毛豆荚壳(P<0.05),玉米青贮和毛豆荚壳无显著差异(P>0.05);玉米芯的ADF有效降解率最高(P<0.05),苜蓿干草、玉米青贮和毛豆荚壳无显著差异(P>0.05)。综上所述,玉米芯和毛豆荚壳可作为非常规粗饲料资源加以开发利用。     

A comparative study on the rumen microbial populations,hydrolytic enzyme activities and dry matter degradability between different species of ruminant

A comparative study among Korean native cow (Hanwoo), Holstein dairy cow, Korean native goat and crossbred sheep on the population and marker concentration of ruminal microbes, the activities of carboxymethylcellulase (CMCase), xylanase and amylase, and in situ dry matter (DM) degradability were conducted. Twelve ruminally cannulated animals, three of each species, were used. Animals were fed the same diet containing 40% formula feed and 60% rice straw at the level of 2.5% of body weight. Total viable microbial populations in the rumen fluid were significantly (P < 0.01) greater for bacteria and fungi in goat than those of Holstein. The protozoan population among ruminant species was the reverse from that of bacteria. The concentrations of 2,6‐diaminopimelic acid and chitin as markers for bacteria and fungi in the rumen fluid, respectively, were highest in goat, which is in accordance with the above population data. The concentration of aminoethylphosphonic acid as marker of protozoa was highest in Hanwoo and lowest in sheep (P < 0.01). Goat had the highest (P < 0.01) activities of all the enzymes investigated among ruminants. In situ effective degradation of the DM of rice straw was approximately 19% higher in the rumen of goat compared with other animals.     

In vitro metabolism of tyrosine by rumen bacteria, protozoa and their mixture

An anaerobic in vitro study of tyrosine (Tyr) metabolism by rumen bacteria (B), protozoa (P) and their mixture (BP) was conducted using an HPLC analytical method to obtain some basic and systematic information on aromatic amino acid metabolism in the rumen. Most of the Tyr (> 96%) disappeared after 12 h incubation in B and BP, but only 58% in P. Tyr was converted mainly to p‐hydroxyphenylacetic acid (HPA) in all microbial suspensions. About 45% of disappeared Tyr in B and P, and about 35% in BP were converted to HPA. An appreciable amount of phenylalanine (Phe), 13 and 3% of disappeared Tyr, and a small amount of tryptophan (Trp), 8 and 1% of disappeared Tyr, were also produced from Tyr by rumen bacteria and protozoa, respectively. Small amounts of p‐hydroxyphenylpyruvic acid (about 4 and 6% of disappeared Tyr) were produced from Tyr in B and P, respectively. A moderately large amount of phenylacetic acid (14% of disappeared Tyr) was produced from Tyr in P which was 1.9 times higher than that in B. Phenylpropionic acid and p‐hydroxybenzoic acid were produced only in B and BP. It was concluded that the Tyr degradation ability of rumen bacteria was about 1.5 times higher than that of rumen protozoa. Degraded Tyr mainly produces HPA and then two other aromatic amino acids, Phe and Trp, which are considered essential amino acids for ruminants. Therefore, it is speculated that the requirement for Phe and Trp in ruminants may be partially fulfilled if Tyr is sufficiently supplied in rations.     

Effect of flow parameters of rumen digesta on effective degradability and microbial yield in sheep

The aim of this experiment was to examine the effect of rumen digesta flow parameters on effective degradability (EDG) and microbial nitrogen (MBN) yield in sheep fed diets of identical provision of both metabolizable energy and rumen degradable nitrogen (RDN). Ruminal degradation parameters of early‐harvested perennial ryegrass hay (EH), late‐harvested perennial ryegrasses hay (LH) and winter sown barley straw (BS) were determined by a nylon bag technique. Subsequently, three experimental diets (EHD, LHD and BSD) were formulated using the tested forages, sucrose and urea as supplements. An in vivo feeding study was conducted using four rumen cannulated sheep in a partial Latin square design. Digestibility, rate constants of rumen particle breakdown and passage, ruminal fermentation parameters and MBN supply to the small intestine were determined. Animals thoroughly consumed the forages fed at a restricted level. Digestion coefficients were greater for EHD than for LHD and were lowest for BSD (P < 0.05). The rate constant of large particle breakdown was 4.3, 5.9 and 6.7 %/h, respectively, and small particle passage was 5.3, 4.7 and 6.3 %/h for EHD, LHD and BSD, respectively. The estimates differed (P < 0.05) between the diets. The overall passage rate constant of total rumen particles was estimated to be higher for BSD than that for EHD or LHD (P < 0.05). Ruminal fermentation parameters were unaffected by dietary treatments (P > 0.05). Intake levels of rumen degradable organic matter (RDOM) and RDN were estimated to be greater for LHD than that for EHD or BSD (P < 0.05). Although dietary arrangements were made to give identical microbial efficiency, the estimated value was higher for EHD than that for LHD or BSD (P < 0.05); and the MBN yield for BSD was estimated to be lower than that for EHD or LHD (P < 0.05). Rumen kinetic parameters of degradation and particle flow of forage affected EDG values and MBN yield from forage‐related RDN intake, although those had little effect on the efficiency of MBN yield from forage‐related RDOM intake.