Profile of isoacids in rumen fluid and influence of added isoacids on in sacco dry matter disappearance of untreated and ammonia treated wheat straw

The influence of type of diet and time after feeding on concentration of isoacids in rumen fluid of 6 fistulated sheep were investigated. The concentration of isoacids in rumen fluid was higher in diets rich in concentrate and protein (5.6) than in roughage diets (3.4) or in straw-starch-urea diets poor in native protein (highest concentration: 2.1 mmol/l rumen fluid). Feeding of roughage diet or straw-starch-urea-diet effected a significant decrease of concentration of isoacids in the rumen fluid after morning feeding, but concentrate-roughage diet, increased the isoacids-concentration. Reasons for decreased concentration of isoacids may be a shortage of corresponding amino acids and a high activity of cellulolytic microbes. Infusion of isoacids (3 g per day) in the rumen of sheep fed with a straw-starch-sugar-urea diet did not significantly influence the in sacco dry matter degradability of untreated wheat straw, but increased the dry matter loss of ammonia treated wheat straw from 16.0; 26.6; 39.4; 54.0 and 58.8% to 17.3; 29.7; 43.1; 56.3 and 63.0% after 6; 12; 24; 48 and 72 h rumen incubation time respectively. Further experiments seem to be necessary. The effect of isoacids may be expected to occur with poor quality feeds, rich in fibre low in protein and hence low in branched-chain amino acids.     

Influence of yeast (Saccharomyces cerevisiae as Yea-Sacc or Levaferm) on in Sacco dry matter degradability and ruminal parameters of variously fed small ruminants.

Two series of experiments with rumen fistulated castrated male sheep and goats were carried out. In experiment I three sheep each consumed rations rich in concentrate (700 g concentrate, 200 g chopped wheat straw) or roughage (700 g artificially dried ryegrass, 200 g chopped wheat straw per animal per day) and supplemented with 0, 1, 2 or 4 g Yea-Sacc (Saccharomyces cerevisiae; USA) per sheep per day. In experiment II three sheep were fed with 1000 g artificially dried ryegrass and 200 g concentrate, three goats consumed 750 g ryegrass and 150 g concentrate. 0, 0.5, 1 or 2 g Levaferm (Saccharomyces cerevisiae; Germany) per animal per day were added. Rations of all animals were supplemented with minerals and vitamins. After 14 days of feeding wheat straw, ammonia treated wheat straw and artificially dried grass (exp. I) or wheat straw and artificially dried grass (exp. II) were incubated in nylon bags in the rumen for 6, 12, 24, 48 and 72 hours. At the end of the experiments rumen fluid was taken via cannulae and parameters of rumen fermentation were measured. Higher levels of added Yea-Sacc decreased in sacco dry matter degradability of all incubated feeds. Depression was much higher if Yea-Sacc was added to the concentrate ration (overall mean for 24, 48 and 72 h incubation time: 55.1, 47.1, 46.1 and 44.5 for 0, 1, 2 and 4 g Yea-Sacc) than to the roughage diet (58.7, 56.3, 55.0 and 54.1%). Levaferm did not significantly influence the rumen dry matter degradability of incubated feeds (overall mean for 24, 48, and 72 h incubation time: 64.0; 64.9; 64.9 and 64.2% for sheep; 63.0; 63.2; 63.2 and 61.6% for goats, if added with 0, 0.5, 1 and 2 g Levaferm per animal per day). Rumen pH, concentration of volatile fatty acids and molar concentration of fatty acids in rumen fluid were not significantly influenced by added yeasts. More research seems necessary to find out the mode of action of yeast and to quantify and to reproduce the effects of added yeast.     

Effect of defaunation and refaunation of the rumen on rumen fermentation and N-flow in the duodenum of sheep

In order to confirm earlier fragmentary results, the effect of defaunation and refaunation of the rumen on the fermentation pattern and flow of N-components in the proximal duodenum of two sheep was investigated. Defaunation had no effect on acetic acid as a proportion of the total volatile fatty acids in the rumen, while the proportions of propionic acid increased with a concomitant decrease in butyrate. Refaunation resulted in lower acetic acid and higher butyric acid proportions. The concentration of ammonia N in the rumen was clearly decreased after defaunation, already indicating an effect of the elimination of protozoa on nitrogen metabolism in the rumen. Defaunation also increased significantly the flow of total N, non ammonia N and individual and total amino acids in the proximal duodenum. Defaunation resulted in higher bacterial growth efficiency, significantly in one sheep, but the decrease after refaunation was statistically significant for both sheep. Determination of rumen digestibility of organic matter and acid detergent fibre (ADF) revealed lower values in the absence of the protozoa, while total digestibility was only influenced to a much lower extent. This indicated a shift of digestion from rumen to the lower digestive tract. Finally, earlier work is discussed in the light of the present findings.     

高精料诱导的SARA对泌乳期山羊血液和瘤胃液中皮质醇的影响

选择7只装有永久性瘤胃瘘管的泌乳中期山羊,2×2拉丁方设计,分别饲喂精粗比为6∶4和4∶6的饲料,通过饲喂精粗比6∶4饲料建立泌乳期山羊瘤胃亚急性酸中毒(subacute ruminal acidosis, SARA)模型,研究SARA时山羊血液和瘤胃液中皮质醇浓度、肝脏皮质醇受体(glucocorticoid receptor, GR)mRNA表达及其他相关指标的变化。结果表明,精粗比6∶4日粮饲喂2周后成功诱导SARA状态(SARA组),采食后瘤胃液pH值低于5.8持续时间约6 h,而精粗比为4∶6组山羊瘤胃液pH均高于6.0 (对照组)。高精料日粮处理对瘤胃pH和乳酸以及瘤胃液和血浆内的脂多糖、皮质醇浓度有显著性影响(P<0.05),采食前SARA组山羊瘤胃液中乳酸浓度显著高于对照组(P<0.05),采食后0~4 h乳酸含量下降,6~10 h时逐渐增加并极显著高于对照组(P<0.01);2组间瘤胃液中脂多糖浓度无显著性差异(P>0.05),SARA组血浆脂多糖浓度在采食前和采食后6 h均显著高于对照组(P<0.05);采食前SARA组山羊血液中皮质醇浓度高于对照组(P=0.05),但采食后6 h两组间无显著差异(P>0.05); 2组山羊瘤胃液中皮质醇浓度在采食后2,4和6 h分别显著高于对照组(P<0.05),但在采食前和采食后10 h无显著差异(P>0.05)。Real-time PCR结果显示,SARA组山羊肝脏中GR mRNA表达显著下调(P<0.05)。本研究结果显示,泌乳期山羊发生SARA时糖皮质激素水平升高,负反馈下调肝脏GR的表达水平,提示SARA时机体处于应激状态,可能引起肝脏的物质代谢和营养物质重分配的改变。     

Metabolism of microbial nitrogen in ruminants with special reference to nucleic acids

Characteristically the metabolism of microbial nitrogen (N) compounds in ruminants involves the degradation of dietary N and synthesis of microbial protein (MP), compounds including a small amount of peptides and free amino acids, which may account for 75–85% of total N and the remainder are nucleic acids (NA: DNA and RNA). Generally rumen microbes contain 10–25% NA‐N of the total N while 70–80% is in the form of RNA. This paper describes the degradation and synthesis of NA in the rumen and their fate in the lower digestive tracts. Their physiological and nutritional significance in different types of ruminant animals is also discussed. The research works on NA metabolism in ruminants has been mainly on metabolism of purines after rumen microbial digestion and absorption in the lower gut. Subsequently, the fate of absorbed purines has been intensively investigated to assess the extent of MP synthesis in the rumen. The method for predicting ruminal synthesized MP and subsequently digested MP has been proposed using urinary purine derivative (PD) excretion in sheep and cattle fed on ordinary feed. The latter approach has now been adopted for calculation of protein supply in some feeding standards, although there are still difficulties in predicting representative samples of rumen microbes, and also uncertainties in variations of non‐renal and endogenous purine losses.     

Rumen fermentation response to a direct-fed xylanase enzyme preparation from Thermomyces lanuginosus in sheep

A study was conducted to obtain data on the effects of a fungal fibrolytic enzyme preparation (Rumino-zyme, with 250 FXU/g xylanase activities) from Thermomyces lanuginosus on some rumen fermentation parameters in sheep. Ruminal fluid samples were taken just before the morning feeding and then 2 h and 4 h after feeding. Xylanase activity, pH, concentration of ammonia and volatile fatty acids were measured. The enzyme supplementation did not affect the pH but increased the xylanase activity and the total VFA concentration of the rumen fluid. The molar proportion of acetate increased, propionate was not affected and butyrate decreased after enzyme administration. The concentration of ammonia also decreased after supplementation with the enzyme product. It can be concluded that the xylanase enzyme preparation from T. lanuginosus induced favourable changes in the major rumen fermentation parameters in sheep.     

Concentration of free amino acids in the blood plasma of sheep with different amounts of nitrogen in the feed

Trials were conducted with four adult sheep of the Merino breed, live weight 45 to 50 kg, fed two diets with different nitrogen levels (7.6 g nitrogen per day as protein or 24 g nitrogen per day with an addition of 17.4 g urea nitrogen to 7.6 g nitrogen as protein). The following findings were obtained: the concentration of free amino acids in blood plasma in the 9th, 12th, 15th, 18th and 22nd weeks from the beginning of feeding with both diets was lower, in most of the analyzed amino acids, three hours after feeding than before feeding. The results show that at an increased intake of urea nitrogen the concentration increases of the free amino acids lysine, serine, glutamic acid, glycine, valine and isoleucine before feeding. Three hours after feeding these differences are less pronounced. An increase is only recorded in the concentration of arginine, glutamic acid and glycine, whereas the concentration of alanine decreases.     

Stability of ivermectin in rumen fluids

To determine whether ivermectin is metabolized in the rumen, in vitro studies were conducted with the tritium-labelled H₂B_1a component of ivermectin in rumen fluid from sheep and cattle. No detectable metabolism occurred over 24 h in in vitro incubations at 38°. The viability of the microbes in the rumen fluids was demonstrated by the conversion of 17% and 11% of [¹⁴C]cellulose to ¹⁴CO₂ in 24 h in the incubations with sheep and steer rumen fluids respectively. The results indicate that ivermectin is not metabolized in the rumen. Based on the lack of in vitro metabolism of ivermectin in rumen fluid, the similarity of in vitro liver microsomal metabolism with in vivo metabolism of the avermectins and the physicochemical properties of the avermectins, any disappearance of ivermectin in vitro from rumen fluid is probably a result of binding to solids or surfaces. Apparent discrimination by dung beetles, where observed, between control faeces and faeces from cattle or sheep treated with ivermectin or abamectin therefore must be attributable to chance, to factors unrelated to treatment or to factors such as changes in amino acid composition rather than the production of volatile metabolites of ivermectin.     

日粮硝酸盐水平对湖羊瘤胃硝态氮动态消失率、发酵参数及血液高铁血红蛋白含量的影响

本试验研究日粮硝酸盐的添加量对湖羊瘤胃还原硝态氮程度和对发酵参数及血液高铁血红蛋白的影响。试验选取6头湖羊,采用随机区组试验设计,每期分别饲喂含0%,1%,2%,3%,4%,5%硝酸钾的日粮。测定喂后0,0.5,1.0,1.5,2.0,4.0,6.0,8.0 h瘤胃液硝酸盐和亚硝酸盐含量及瘤胃发酵参数。晨饲后2.0 h通过颈静脉采血,测定高铁血红蛋白含量。结果表明,湖羊在采食1.0 h后硝酸盐含量达到最高(0.952.14 g/L),之后快速消失,亚硝酸盐含量在喂后1.5 h达到最高(0.936.22 μmol/L),之后降低。高铁血红蛋白的含量随硝酸盐添加量的增加而显著升高(P<0.01),最高达0.32%。添加硝酸盐显著提高瘤胃液pH值(P<0.01)和2.0 h的氨态氮含量(P<0.01)以及乙酸/丙酸,添加量高于3%会降低微生物蛋白和总挥发性脂肪酸的浓度,2%的硝酸盐添加量微生物蛋白和总挥发性脂肪酸的合成量最高,最有利于微生物发酵。     

Relationship between the volatile fatty acids (VFA) in the rumen and nitrogen secretion into isolated sheep's rumen]

Two sheep with a ruminal fistula and an isolated small rumen were studied for the secretion of ammonia nitrogen, urea nitrogen, and amino nitrogen into the isolated rumen at different levels of volatile fatty acids (VFA) (50, 133-97, and 97-66 M Mol 1(-1)) in the rumen. The VFA level in the rumen was found to exert a great influence on the quantitative secretion of endogenous nitrogen from the blood through the rumen wall into rumen content. When the VFA level in the rumen was increased by administration of a single dose of acetic, propionic, and butyric acid, the secretion of ammonia nitrogen and amino nitrogen abruptly dropped and the secretion of urea into the isolated rumen slightly increased. The over-all amount of nitrogen (NH3-N + urea-N + amino-N) that had passed into the isolated rumen in the course of an hour showed a highly significant correlation with the passage of nitrogen in the form of ammonia and amino nitrogen and was greatest before the application of VFA to the rumen, i.e. at the level of 50 m mol 1-1. Of the metabolites under study, which were passing to the isolated rumen, amino nitrogen shared the greatest proportion (45.38-46.54%). When the VFA level in the rumen was raised, the proportion of ammonia secreted to the isolated rumen decreased and the proportion of urea in the total amount of nitrogen increased.     

The effect of bentazone manufactured in Czechoslovakia on the synthesis of bacterial proteins in the rumen of sheep]

The effect of the perorally ingested pesticide bentazone (195 mg.kg-1) of Czechoslovak origin on the amino acid composition of proteins of bacteria adhering to the ventral and dorsal ruminal wall investigated in six sheep. Proteosynthesis of adherent bacteria was studied by a modified and quantified elution method (elution of bacteria by an isotonic buffered solution at 4 degrees C). By the latter, a concentrate of undamaged bacteria a adhering to the sheep ruminal epithelium could be obtained. The yield of the method was estimated by scanning electrone microscopy and it was 93.3% (Legáth et al., 1990). The high correlation coefficient (r = 0.94, p < 0.01) suggested that in comparison with the control group of sheep, bentazone in the diet did not have a marked effect on the amount of amino acids in hydrolyzates of bacteria adhering to the dorsal and ventral ruminal epithelium. From the analysis of the single amino acids, it however follows that bentazone in the feeding ration caused significant changes in the concentrations of some amino acids in the proteins of bacteria adhering to the epithelium in the ventral and dorsal part of the rumen (p < 0.05) (Tab. I, II). In both topographico-anatomical parts of the rumen phenylalanine levels significantly increased whereas those of alanine and glycine decreased (Fig. 1). Pesticides can be one of the factors that negatively affect the biosynthetic processes in the rumen of ruminants.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in amino acid levels in bacteria adhering to rumen epithelium in sheep after oral administration of very low doses of mercury

The effect of low concentrations of mercury taken in the diet (4 mg per a head and day) on the amino acid composition in the proteins of rumen bacteria adhering to the dorsal and ventral parts of the rumen was studied in six sheep. Though the mercury did not influence the amino acid concentration in hydrolyzates of epimural bacteria, low-mercury doses caused significant changes of some amino acids, as compared with the control group of animals. The levels of alanine, histidine, threonine, serine and glycine were significantly decreased and at the same time the levels of proline, valine, isoleucine, tyrosine, lysine and phenylalanine were significantly increased. It was stated in our experiment that the levels of histidine, alanine and threonine in hydrolyzates of epimural bacteria of the rumen were significantly decreased both in the sheep given the balanced feed ration with additions of mercury and nitrogen (according to the standard) and in the sheep given a low-nitrogen diet. Similarly, the levels of proline, tyrosine and phenylalanine in the hydrolizates of epimural bacteria in rumen were significantly increased both with the low-nitrogen diet and in the normal -nitrogen diet with mercury supplement. The results suggest that unexplained disorders frequently occurring in the microbial synthesis in the rumen might be caused by long-continued administration of feed contaminated with extremely low concentrations of heavy metals. The problem deserves detailed investigation in future studies, oriented to explaining the biosynthesis disorders in rumen, reducing the production ability of ruminants.     

Assessment of ruminal degradation, oral bioavailability, and toxic effects of anticoagulant rodenticides in sheep

OBJECTIVE: To assess the rate and extent of ruminal degradation of warfarin, chlorophacinone, and bromadiolone in vitro and determine the oral availability and clinical and hemostatic effects of each anticoagulant rodenticide in adult sheep. ANIMALS: 3 Texel sheep. PROCEDURE: Samples of ruminal fluid were incubated with each of the anticoagulants to assess the kinetics of ruminal degradation over 24 hours. To determine the plasma kinetics of the anticoagulants, each sheep received each of the anticoagulants IV or via a rumenimplanted cannula at 2-month intervals (3 rodenticide exposures/sheep). At intervals during a 240- to 360- hour period after treatment, prothrombin time (PT) was measured, plasma anticoagulant concentration was assessed, and clinical signs of rodenticide poisoning were monitored. In plasma and rumen extracts, anticoagulant concentrations were determined via high-performance liquid chromatography. RESULTS: In the rumen extracts, anticoagulants were slightly degraded (< 15%) over 24 hours. In vivo, oral availability of warfarin, chlorophacinone, and bromadiolone was estimated at 79%, 92%, and 88%, respectively. Although maximum PT was 80 seconds after chlorophacinone and bromadiolone treatments, no clinical signs of toxicosis were detected; PT returned to baseline values within 2 weeks. CONCLUSIONS AND CLINICAL RELEVANCE: In sheep, warfarin, chlorophacinone, and bromadiolone were not degraded in the rumen but their bioavailabilities were high after oral administration; the kinetics of these compounds in sheep and other mammals are quite similar. These data suggest that the lack of susceptibility of ruminants to these anticoagulant rodenticides cannot be explained by either ruminal degradation or the specific toxicokinetics of these anticoagulants.     

埃氏巨型球菌及其乙酸生成关键酶基因缺失工程菌体外代谢特性的初步研究

埃氏巨型球菌是奶牛瘤胃中的一种优势菌。本研究运用瘤胃微生态理论,结合埃氏巨型球菌能利用乳酸发酵产生丙酸的特点,初步研究埃氏巨型球菌(H6)及其乙酸生成关键酶基因缺失工程菌(TnH6)体外发酵特性。经健康羊瘤胃液体外连续培养结果表明,埃氏巨型球菌及其乙酸生成关键酶基因缺失工程菌均能利用乳酸生成VFA,发酵生成的VFA以丙酸为主,发酵类型倾向于丙酸型,但工程菌生成乙酸的能力明显降低,尽管丙酸生成能力有所下降,但显著降低了乙酸与丙酸的比例,从而为调控瘤胃乳酸发酵和利用H6、TnH6防治奶牛亚临床性瘤胃乳酸酸中毒提供了理论和试验基础。     

湖羊利用混合挥发性脂肪酸铵的研究——体外试验与前胃消化代谢试验

体外试验研究表明,试验管NH_3-N浓度于培养过程中逐渐下降。而三氯醋酸沉淀蛋白(TCA-P)浓度则迅速上升,2.5小时后超过对照管。同时丁酸向乙酸转化。利用3头装有永久性瘤胃瘘管和皱胃瘘管的湖羊,进行体内试验,以挥发性脂肪酸胺(AS-VFA)替代日粮总氮34％。饲喂后瘤胃NH_3-N、TVFA和丁酸浓度迅速上升,瘤胃内稻草粉纤维素48小时消失率为38.6％,显著高于对照期的31.94％(P<0.05)。试验期1昼夜通过皱胃的总氮量为14.27克,非氨氮(NAN)13.02克,微生物氮4.06克,均有提高趋势。微生物蛋白合成效率提高70％(P<0.01),而前胃有机物消化率则趋于降低。     

Protein supplement resistant against ruminal degradation as a factor improving utilization of urea in ruminant feeding

The metabolic and productive effects of the blood meal and formaldehyde (FA) treated casein supplements (5-10% of crude protein content) given with urea concentrates in sheep and fattening bulls were investigated. The blood meal has a similar composition of essential amino acids (EAA) to casein. The mean solubility of the FA treated casein and the blood meal after 6 hours of incubation in the sterilized rumen contents amounted 10.5% and 8.5% respectively. The average rumen ammonia concentration and plasma urea level was the highest in bulls fed urea ration without protected protein supplement. The supplementation of this ration with blood meal diminished the large daily fluctuation of plasma AA level and increased plasma EAA/NEAA ratio. The blood meal supplement improved the nitrogen retention in sheep (14%) and body gains in bulls (9%) but did not influence digestible coefficients and rumen protein synthesis in sheep.     

The estimation of utilizable amino acids (uAA) of feeds for ruminants using an in vitro incubation technique

The in vitro incubation technique of Zhao and Lebzien (2000; Arch. Anim. Nutr. 53, 293-302) was used for the estimation of utilizable amino acids (uAA) (sum of amino acids from undegraded feed protein and microbial protein, when N is not limiting) of feeds for ruminants. The rumen fluid from a cow fed only with hay (Expt. 1) and that from a sheep fed with a mixed ration (Expt. 2) was compared with respect to estimation of uAA. In Expt. 1, 30 feeds and feed mixtures were tested and in Expt. 2, 33 feeds and feed mixtures were tested. A close linear relationship was found between the utilizable crude protein (uCP=undegraded feed protein + microbial protein) (X, g/kg) calculated from in vivo experiments and the uAA (Y, g/kg) estimated from in vitro incubations both in Expt. 1: y= 0.95 x-1.39, r2=0.85, p<0.001,n=30; and in Expt. 2: Y=0.85X-6.67,r2= 0.85,p<0.001,n=33. Statistical analysis indicates that there was a significant regressive relationship between uAA determined with the rumen fluid of a sheep (X, g/kg) and uAA determined with the rumen fluid of a cow (Y, g/kg): Y=1.06X+12.4,r2= 0.80,p<0.001,n=27. The results indicate that the in vitro incubation technique of Zhao and Lebzien (2000) can be used for the estimation of uAA of feeds for ruminants. As a rumen-fistulated cow is more expensive than a rumen-fistulated sheep, it is suggested to use a sheep fed a mixed ration as the donor of rumen fluid for the estimation of uAA of feeds with in vitro incubation. Further experiments should be performed to standardize the method and to test the most valid length of the incubation period.     

Passage of amino acids through the minimal wall in sheep]

Three sheep with a small isolated rumen (after Gridin et al., 1964) were studied for the passage of amino acids from the blood to the isolated rumen before feeding and 1, 2, 3, 4 and 5 hours after feeding. It was found that, on an average for all the time intervals mentioned above, the passage of glycine was the largest of all the amino acids studied (0.512 muMol per 100 ml), followed, in descending order, by lysine, alanine, glutamic acid, aspartic acid, serine, leucine, threonine, isoleucine, arginine, tyrosine, and phenylalanine (0.038 muMol per 100 ml). Before feeding and one hour after feeding, lysine shared the greatest proportion of all amino acids that had passed into the isolated rumen (0.565-0.43 muMol per 100 ml), followed, in descending order, by glycine, alanine, valine, aspartic acid, glutamic acid, leucine, serine, threonine, isoleucine, tyrosine, phenylalanine; arginine was, in this case, represented by the smallest proportion (0.042-0.030 muMol per 100 ml). It is inferred from the results that the amount of amino acids passing from the blood through the rumen wall changes with the time that has elapsed from feeding, and that before feeding this passage is more intensive than after feeding. These changes are held to be related with an increased passage of endogenous nitrogen to the rumen in the period of a relative deficiency of substances which are derived from the feed and are essential for maintaining homeostasis in the rumen.     

不同加工方式针茅草对绵羊干物质采食、消化及瘤胃内环境的影响

本试验旨在研究针茅草的不同加工方式对绵羊采食、消化及瘤胃内环境的影响。选用体重[(45±2)kg]、年龄(1.5~2.0岁)相近安装有永久性瘤胃瘘管的乌珠穆沁羯羊48只,随机分为4组,每组12只,分析干草、草颗粒、草块、草粉4种加工方式的针茅草对绵羊干物质采食量、表观消化率及瘤胃液pH及总氮、氨氮、总可利用氮、挥发性脂肪酸浓度的影响。预试期10 d,正试期7 d。结果表明:1)针茅草颗粒的干物质采食量及表观消化率显著高于其他组(P0.05)。2)与其他各组相比,针茅草颗粒组的绵羊食后1 h瘤胃液pH显著降低(P0.05),总氮、氨氮和总可利用氮浓度较高。3)草颗粒组的瘤胃液总挥发性脂肪酸浓度显著高于干草和草粉组(P0.05)。由此可见,针茅草颗粒的干物质采食量、表观消化率以及在绵羊瘤胃内的发酵指标均较优,是饲喂绵羊的最佳利用形态。     

Feeding animal fats to sheep.

In an experiment lasting 7 weeks, 18% of the calculated energy requirement of 5 nonpregnant ewes was met by giving natural fats of animal origin mixed in the ration (at a level of 6.6%). Changes in certain blood and blood plasma parameters of lipid and energy metabolism were monitored at 5 time-points during the experiment. Samples of rumen fluid were taken three times for determining the concentrations of volatile fatty acids (VFA). Rumen fermentation was studied by in sacco method. Total lipid (TL) content of the liver and fatty acid composition of the liver tissue and subcutaneous adipose tissue (from the tailhead) were analyzed at the beginning and at the end of the experiment. At the concentration used in this experiment, fat supplementation caused neither digestive disturbances nor any other adverse changes in the animals' health status. It did, however, exert a significant influence on blood plasma lipid composition. TL and total cholesterol (TCh) concentration increased and blood glucose level decreased. A rise in triglyceride (TG) content was accompanied by a drop in free fatty acid (FFA) concentration. The in sacco experiments and volatile fatty acid (VFA) levels in the rumen fluid suggested an impaired crude fibre digestion in the rumen. At the same time, fat supplementation enhanced rumen proteolysis. The TL content of liver samples did not exceed the physiological limit. The liver biopsy samples had decreased myristic acid and increased stearic and oleic acid concentrations. No change occurred in the fatty acid composition of the fat depots.