In vivo mechanical and in vitro electromagnetic side-effects of a ruminal transponder in cattle

This work was undertaken to assess the long-term impacts of a ruminal transponder, used for electronic identification, on ruminal motility and on health and performance of cattle, as well as to study the electromagnetic effects on ruminal bacteria in vitro. A passive transponder (51.4 g, 67 x 17 mm) was delivered into the forestomachs of 8 calves, 32 bulls, 10 heifers, and 40 dairy cows. Final readability was 87.5% in calves, 96.9% in bulls, 90% in heifers, and 100% in cows at 481, 360, 650, and 601 d, respectively, after transponder administration. The transponder did not affect production or reproduction of cows over a 2-yr period, or performance of bulls, or mortality compared with control animals. Chewing movements per bolus were lower (P <0.01) in treated animals than in controls (49.6 vs. 52.2, 51.2 vs. 63.6, and 57.0 vs. 59.7 for bulls, heifers, and cows, respectively). Regurgitation frequency (number of boluses/10 min) tended to be greater in treated cattle: 12.4 vs. 11.3 (P = 0.07), 11.3 vs. 10.6, and 11.3 vs. 10.7 (P = 0.08) for bulls, heifers, and cows, respectively. Rumination patterns of calves fitted with transponders within the first weeks of life were similar to controls. During the experiment, 43 treated animals (8 calves, 29 bulls, and 6 cows) were slaughtered. Thirty transponders were localized in the reticulum (3 calves, 24 bulls, and 3 cows), 11 in the rumen (4 calves, 4 bulls, and 3 cows), and 2 were not recovered (1 calf and 1 bull). Within the calves, 57% of the boluses were found in the rumen. In 8 reticula (2 calves and 6 bulls) and 1 rumen (1 cow), an impression left by physical contact of the transponder was observed, although histological examination did not reveal specific lesions in the mucosa of the dystrophic areas. In strained, whole ruminal contents incubated in vitro, pH values were lower after 24 and 48 h (P <0.001) of continuous exposure to an electromagnetic field induced by the transponder-reading system. After 48 h of incubation, total bacterial numbers and NH3-N concentration were greater (P <0.001) in exposed flasks than in controls. These data indicate that the transponder may alter, via mechanical action, the reticuloruminal mucosa and rumination patterns. Furthermore, the transponder may increase, via its electromagnetic action, the growth rate and metabolic activity of ruminal bacteria.     

Propionic acid disappearance from the foregut and small intestine of the beef steer

Studies were conducted to determine the disappearance of propionic acid from the rumen and across the small intestine. Four crossbred beef steers, fitted with ruminal, duodenal and ileal cannulas, were given pulsed-continuous infusions of a nonabsorbable liquid phase marker (CrEDTA) and buffered propionic acid to achieve ruminal propionate productions (RPP) of 142 (basal), 567 and 997 mmol/h. Liquid flows from the rumen, and at the duodenum and ileum (2.75, 3.57 and .92 liters/h, respectively) were not affected by RPP (P greater than .23), although significant differences existed between sites (P = .001), reflecting a net addition of liquid between the rumen and duodenum and a net removal of liquid within the small intestine. Propionate disappearance from the rumen was 40 to 57% irrespective of RPP, with the complement passing from the rumen. Of the propionate that exited the rumen, 93 to 97% disappeared prior to entering the duodenum. Overall removal of RPP prior to the duodenum was 97 to 99% irrespective of RPP. Passage of propionic acid at the duodenum and at the ileum did not differ (P greater than .76) across all RPP, and the overall mean passages did not differ from zero (P greater than .34); similar results were observed for other VFA. These observations indicate that essentially all RPP is removed prior to entering the small intestine. Additionally, net propionate disappearance across the small intestine was undetectable and likely biologically irrelevant. Therefore, VFA absorption does not appear to be a limiting biological process in the beef steer.     

Polyamines in the gastro-intestinal tract of goat kids and in the regenerating ruminal epithelium of sheep

The aim of the present study was to investigate whether temporal changes in polyamine concentration and synthesis could be found in the luminal content and wall tissue of the rumen and abomasum, two organs which have entirely different growth patterns during the first month of life. In the abomasal mucosa there was a marked gradual decrease in the ornithine decarboxylase (ODC) activity during the first month of life, while the ODC activity in the ruminal mucosa was low during the whole experimental period. However, injury of the rumen wall was followed by increased ODC activity. The ODC activity in duodenal mucosa was about 10 times higher than in the ileal mucosa and the ruminal epithelium. In ruminal liquid a clear peak in ODC activity was observed during the period 51-70 days after birth. The polyamine concentration did not parallel the ODC activity, in either the ruminal epithelium or the ruminal liquid. Of the polyamines, the spermine concentration was always highest, and with the exception of duodenal mucosa, the putrescine concentration was lowest. In liver a clear decrease in spermidine concentration from day 1 to about day 60 after birth was observed. Otherwise no marked temporal changes in tissue polyamine concentrations were observed. Two and a half hours after oral administration of 14C-labelled spermine, nearly all of the radioactivity was found in the lumen of the gastrointestinal tract. On the other hand, 1 h after intravenous injection of polyamines the walls of the gastrointestinal tract were strongly labelled. In conclusion, the polyamines needed for ruminal epithelial development seem to come from sources other than the ruminal epithelium itself or the ruminal lumen.     

反刍动物小肠氨基酸调控

反刍动物小肠氨基酸调控是反刍动物营养研究的重要课题。反刍动物小肠氨基酸的调控是以反刍动物氨基酸的需要为基础,有目的地通过各种途径使小肠吸收氨基酸含量达到动物的生产需要。反刍动物小肠氨基酸调控主要有以下几方面:通过瘤胃蛋白质保护、改变饲料在瘤胃中停留时间和添加生物制剂调节日粮过瘤胃蛋白质;通过日粮可发酵能、能氮平衡和瘤胃微生物环境控调微生物蛋白质;通过瘤胃保护氨基酸(RPAA)调控小肠氨基酸。     

Effect of ruminal dosing of mechanical stimulating brush on rumination time, ruminal passage rate and rumen fermentation status in Holstein steers fed a concentrate diet

This experiment was conducted to determine the effect of ruminal dosing of a mechanical stimulating brush on rumination time, ruminal passage rate and rumen fermentation status in steers fed a concentrate diet at maintenance level. Animals were dosed three Rumen Faibu (RF) per head through the rumen fistulae (RF treatment) and not dosed (control) in a change‐over design. The organic cell wall content of the concentrate diet was 12.7% of dry matter. Daily time spent on rumination was very short in both treatments with 24 min in RF treatment and 15 min in control. The turnover rate of ruminal fluid in RF treatment was higher than that in control. There were no differences in ruminal pH and total volatile fatty acid concentration between RF treatment and control. Acetic and butyric acid concentrations were not different between the treatments. Propionic acid concentration tended to be higher in the animals on RF treatment than in control animals. The RF dosing in Holstein steers fed a low fiber diet did not affect the rumination time, but increased rumen digesta passage rate and ruminal propionic acid production.     

Rumen fermentation and starch degradation by Holstein steers fed sodium-hydroxide- or formaldehyde-treated wheat

The authors investigated the effect of feeding 2% sodium-hydroxide-treated (as-fed basis) or 2% formaldehyde-treated (crude protein basis) wheat to rumen-, duodenal- and ileocaecal-cannulated Holstein steers on rumen fermentation and ruminal and postruminal starch degradation. Feeding 2 kg/day wheat treated with sodium hydroxide (NaOH) or formaldehyde did not affect negatively the main parameters of rumen fermentation, i.e. pH, short-chain fatty acid (SCFA) production, and microbial activity. Fibre degradation in the rumen was significantly improved when NaOH-treated wheat was fed. The in vivo experiments demonstrated that feeding NaOH- and formaldehyde-treated wheat to steers significantly increased the amount of starch that reached the small intestine. The amount of starch that entered the duodenum increased by 57% and 75% when steers were fed NaOH- and formaldehyde-treated wheat compared to the control phase, respectively. This higher quantity of starch was digested and absorbed, which can provide an increased glucose supply to the animals.     

Severe hypoplasia of the omasal laminae in a Japanese Black steer with chronic bloat--a case report

An 11-month-old Japanese Black steer with chronic bloat underwent clinical and histological analyses. During the observation period, it showed normal appetite and fecal volume but persistent chronic bloat symptoms. Compared to controls, the steer's feces contained undigested large straws. Necropsy revealed normal rumen, reticulum, and abomasum but a small omasum. The rumen, reticulum, and abomasum mucosa was normal, with well-developed ruminal papillae. However, severe hypoplasia of the omasal laminae was observed along with hypoplasia reticular groove and ruminoreticular fold. The contents of the reticulum, omasum, and abomasums comprised undigested large sized hay particles. The omasum papillae showed no pathological abnormalities. This is a rare case of a steer with chronic bloat probably caused by severe hypoplasia of the omasal laminae.     

杀灭瘤胃纤毛虫对饲喂粗料日粮湖羊纤维素消化代谢的影响

系列Ⅰ应用两头装有永久性瘤胃瘘管和十二指肠“Ｔ”型瘘管的湖羊，舍饲青干草；系列Ⅱ两头湖羊除装有上述两瘘管外还装有回肠瘘管，舍饲青草。研究杀灭瘤胃纤毛虫对纤维素消化代谢的影响。结果表明：杀灭瘤胃纤毛虫后，瘤胃内ＮＨ３·Ｎ浓度显著下降（Ｐ＜０．００１），ＭＣＰ显著上升（Ⅰ：Ｐ＜０．０５，Ⅱ：Ｐ＜０．０１）；复胃中氮的表现消化率显著下降，进入十二指肠的ＮＡＮ量显著增加，且肠道中氮的表现消化率极显著上升；复胃中纤维素的消化率增加；复胃与大肠的微生物消化之间存在代偿作用。     

Absorption of magnesium and other macrominerals in sheep infused with potassium in different parts of the digestive tract

Two metabolism trials were conducted with 12 crossbred wether lambs, each surgically equipped with a ruminal catheter and abomasal and ileal cannulae, to study the effect of K infusion in different sites of the digestive tract on site of absorption and flow of minerals. The treatments consisted of the infusion of 33.6, 12.0 or 12.0 g K/d as bicarbonate into either the rumen, abomasum or ileum, respectively. Each trial consisted of a minimum 5-d preliminary period, five 3-d collection periods to determine mineral balance and a 6-d sampling period to determine mineral flow and site of absorption. Chromic oxide was incorporated into the diet for use as a marker. Magnesium was absorbed primarily from the preintestinal region. Ruminal infusion of K tended to decrease preintestinal Mg absorption. Absorption of Mg in the entire tract was decreased (P less than .05) 43% when K was infused into the rumen. There was a slight absorption of Mg in the small intestine, followed by a net secretion into the large intestine. Serum Mg levels tended to be depressed in lambs infused with K intraruminally. Calcium flow from the preintestinal region was decreased (P less than .05) by infusion of K into the rumen. Only lambs infused with K in the rumen had a net secretion of Na into the small intestine. The large intestine was the primary site of net Na absorption for ruminal-infused lambs. Phosphorus flow from the preintestinal region was decreased (P less than .05) by infusion of K into the rumen. Potassium flow from both the preintestine and small intestine was increased (P less than .05) by ruminal K infusion. The infusion of K into the rumen, abomasum or ileum increased (P less than .05) the total absorption of K, with the small intestine being the major absorptive site. The infusion of potassium bicarbonate into the rumen of sheep raised (P less than .05) the pH of the ruminal contents 15%. Ruminal infusion of K depresses Mg absorption, while the infusion of K into the abomasum or ileum does not affect Mg absorption. Therefore, the role of K in grass tetany may be via this depression of Mg absorption.     

Consequences of failure of the reticular groove reflex in veal calves fed milk replacer

A number of problems seen in veal calves are associated with insufficient adaptation to the changes in husbandry connected with the fattening system. These problems include chronic tympanitis, chronic vomiting, cachexia, unthriftiness, abomasal erosions and ulcers. Some of these problems are associated with failure of the reticular groove reflex, and result in ruminal drinking. Persistent ruminal drinking causes a syndrome characterised by a variety of symptoms such as unthriftiness, severe growth retardation, inappetence, recurrent tympany, abdominal distension, a long dry haircoat and clay-like faeces. Clinical studies performed to investigate the pathogenesis of the syndrome are described. It was found that the milk was stored in the rumen and was partly broken down. The presence of milk in the rumen induced typical changes in the ruminal mucosa (hyper/parakeratosis) and also inhibited casein clot formation in the abdomasum. The small intestinal mucosa showed villous atrophy. After training, the reticular groove reflex was re-established in a number of patients but the growth rate of these calves did not return to normal.     

Dehydrogenase activity in small intestine mucosa in experimental coccidiosis in suckling pigs]

The activities of 3-beta-hydroxybutyrate dehydrogenase (EC. 1.1.1.30.; HBD) and isocitrate dehydrogenase (EC. 1.1.1.41; ICD) were evaluated microdensitometrically in the mucosa of duodenum, jejunum and ileum of 19 conventional piglets infected on the first day after parturition (DAP) with oocysts of Eimeria debliecki coccidium (infection dose of 200,000 oocysts). The two investigated enzymes are deposited in mitochondria which are dispersed in the supra-, para- and infranuclear region of absorption cells (Fig. 1). The synthesis of the two dehydrogenases was investigated in the small intestine mucosa in the period of 1st to 10th day after infection (DAI). The HBD and ICD activities were also followed in the small intestine of four control conventional piglets at the age of 2-5 days (Tab. I). The two dehydrogenases could be characterized by a topographic gradient; it means that their activity was increasing in the small intestine mucosa through duodenum in an aboral direction. The ICD activity is higher in the intestinal mucosa of healthy piglets (Figs. 2 and 3), where its topic concentration was more marked while the HBD activity is dispersed in enterocytes (Fig. 4). In infected piglets the density of the two enzymes was demonstrated to decrease already in the starting period of experimental infection, and it reaches the lowest values for the first time on DAI 5-6 (Fig. 5, Tab. II), then on DAIs 9 (HBD; Fig. 6, graph 11)) or 8 (ICD, Fig. 7 and 10). In the period of experimental infection no statistically significant predisposition to the hypoactivity of target dehydrogenases nor its marked shift were observed. Somewhat rapid resumption of synthesis was demonstrated as soon as on DAI 8 in ICD (Fig. 8); its activity on DAI 10 in the intestinal mucosa corresponded to the 93% activity of this dehydrogenase recorded in the small intestine of control piglets. The density of HBD to the same day (DAI 10) reached in the intestinal mucosa of infected piglets the values making only 44.7% of those demonstrated in the intestinal mucosa of the control group of animals.     

Effects of underfeeding and refeeding on weight and cellularity of splanchnic organs in ewes.

We assessed the effects of a long and severe period of underfeeding, followed by a rapid refeeding with a high-concentrate diet, on weight, protein mass, and cellularity of the splanchnic organs in adult ewes. Twenty-four ewes, allocated to four groups of six, were fed a forage diet (50% regrowth of natural grassland hay and 50% wheat straw) either at maintenance (groups M and MO) or at 40% maintenance (groups U and UO) for 78 d. Groups M and U were then slaughtered, and groups MO and UO were subsequently overfed a high-concentrate diet (52% hay, 20% barley, 16% rapeseed meal, 4% fish meal, and 8% Megalac) at 236% maintenance for 26 d before being slaughtered. During the experiment, feed was adjusted to maintain feed supply at a constant percentage of animal requirements. After slaughter, fresh weight, dry weight, and protein mass of the reticulorumen, omasum, abomasum, small intestine, large intestine, and liver were measured. Cellularity was assessed from nucleic acids and protein contents for both ruminal mucosa and muscular-serosa layers, jejunum, and liver. The concentrations of ubiquitin and cathepsin D mRNA were measured in ruminal mucosa and muscular-serosa layers and in jejunum. Underfeeding decreased protein mass of splanchnic organs, especially in liver (-29%) and reticulorumen (-39%). Refeeding previously underfed animals increased protein mass of liver (+102%) and small intestine (+59%). No carry-over effect of the previous level of intake (UO vs. MO) was observed on the protein mass of splanchnic tissues after 26 d of refeeding. Variations in liver mass were mainly due to hypertrophy, as determined by the protein:DNA ratio, whereas variations in small intestinal mass were mainly due to hyperplasia, as determined by the amount of DNA. By contrast, changes in rumen mass associated with increasing ME intake seemed to be related to hypertrophy in the muscular-serosal component and hyperplasia in the epithelial component. The concentrations of ubiquitin and cathepsin D mRNA in the rumen and jejunum were not modified by feeding level, demonstrating that the expression of these genes for proteolytic enzymes was unchanged under these conditions.     

宏基因组测序分析野生林麝瘤胃、小肠和大肠微生物组成和抗生素抗性基因

本试验旨在研究野生林麝(Moschus berezovskii)瘤胃、小肠和大肠微生物组成和抗生素抗性基因。采集野生林麝消化道3个区段(瘤胃、小肠和大肠)的内容物进行宏基因组测序,并进行常规物种注释和抗生素抗性基因功能注释。结果表明:3个区段共有优势菌门为厚壁菌门(Firmicutes)和变形菌门(Proteobacteria);瘤胃中主要优势菌属为普雷沃氏菌属(Prevotella)、月形单胞菌属(Selenomonas),小肠中主要优势菌属为链球菌属(Streptococcus)、埃希氏菌属(Echerichia),大肠中主要优势菌属为梭菌属(Clostridium)、拟杆菌属(Bacteroides)。基因常规注释显示各个区段微生物基因在不饱和脂肪酸合成和抗生素抗性上差异较大。抗生素抗性基因注释显示macB、sav1866和bcrA绝对丰度最高,且都来自于大肠细菌;瘤胃中抗生素抗性基因绝对丰度最大的是Aminocoumarin_resistant_alaS,小肠中是adeG,大肠中是macB。通过对野生林麝消化道微生物组成分区段比对,发现瘤胃、小肠和大肠微生物组成和抗生素抗性基因分布存在较大差异,大肠和小肠中细菌与野生林麝的多重耐药性关系更密切。     

The role of ciliate protozoa in nutrition of the ruminant

The effects of ciliate protozoa on the ruminal ecosystem, digestion in different parts of the gut, the nature of nutrients available for absorption and their effects upon the nutrition and productivity of their host are reviewed. Compared with fauna-free ruminants, the presence of ciliate protozoa results in a more stable ruminal fermentation, higher levels of ammonia, reduced numbers of bacteria, as well as changes in dry matter (%), liquid volume and turnover rate of ruminal contents. Associated with these differences in the rumen are higher ruminal and total tract digestion of organic matter and fiber in faunated animals. A reduction in net microbial synthesis and an increase in dietary protein degradation in the rumen results in the flow of protein to the small intestine being lower in faunated ruminants. The major nutritional effect of the ciliate protozoa is to change the ratio of protein to energy in the nutrients absorbed, with faunated animals having lower protein and higher energy availabilities compared with ciliate-free ruminants. Of the nutrients available for absorption, the ciliates have no consistent effect on the proportions of volatile fatty acids or amino acids. However, there is evidence that hydrogenation of lipids is increased, as is the supply of choline, and that the bioavailability of copper is reduced by the presence of ciliates. Defaunation of young growing ruminants that are fed high energy diets, containing low levels of ruminal nondegradable protein, results in increased growth rate and feed efficiency. It is unlikely, with the possible exception of wool growth, that there are other situations in which defaunation will be beneficial; and it is more likely to be detrimental to animal productivity. It remains to be determined whether manipulation of the types of ciliate protozoa in the rumen could improve animal performance. Information for this review was largely derived from comparisons of faunated and fauna-free animals. However, it is indicated that there are large differences in protozoa numbers and types between naturally faunated individuals in the same flock or herd, and that the effects of such variations on their host's nutrition are unknown.     

肉牛日粮精料进食水平对淀粉的瘤胃发酵和小肠表观消化率的影响

为了研究日粮精料进食水平对肉牛真胃食糜淀粉流量及其表观消化率的影响,试验选择体重650kg左右荷斯坦(Holstein)公牛3头,安装有瘤胃、真胃瘘管,按3×3拉丁方试验设计分别饲喂粗料进食量相同而精料进食量不同的3种日粮,以三氧化二铬(Cr2O3)作真胃食糜标记物,全收粪法收集粪样,测定真胃食糜和粪中的淀粉流量及在瘤胃内、真胃后段消化道(简称肠道)内的表观消化率。结果表明:日粮精料进食水平对瘤胃及全消化道的淀粉表观消化率没有显著影响(P>0.05),日粮精料水平明显影响到达真胃的淀粉量(P<0.05)。     

滩羊羔羊瘤胃和小肠菌群多样性的比较研究

目的 研究滩羊羔羊瘤胃和小肠菌群多样性的差异。方法 选取健康的断奶滩羊公羔,屠宰后采集瘤胃、十二指肠、空肠和回肠内容物,利用16S rDNA高通量测序技术分析瘤胃和小肠菌群结构及多样性。结果 十二指肠样品Chao1指数高于瘤胃、空肠和回肠,瘤胃样品Shannon指数和Simpson指数均高于其他部位,但差异不显著（P>0.05）。瘤胃液中拟杆菌门（Bacteroidetes）、螺旋菌门（Spirochaetae）、丝状杆菌门（Fibrobacteres）的相对丰度显著（P<0.05）高于十二指肠、空肠和回肠,十二指肠中广古菌门（Euryarchaeota）的相对丰度与瘤胃相比有升高的趋势（0.05<P<0.10）,空肠和回肠中厚壁菌门（Firmicutes）的相对丰度显著（P<0.05）高于十二指肠。瘤胃中的未鉴定菌属（Unidentified）、理研菌属_RC9（Rikenellaceae_RC9_gut_group）、密螺旋体属_2（Treponema_2）、瘤胃球菌属_NK4A214（Ruminococcaceae_NK4A214_group）、普雷沃菌属_UCG-001（Prevotellaceae_UCG-001）相对丰度显著（P<0.05）高于十二指肠、空肠和回肠,空肠中Family_ⅩⅢ_AD3011_group相对丰度显著（P<0.05）高于其他部位。结论 滩羊羔羊瘤胃中细菌的多样性更丰富,瘤胃微生物与十二指肠、空肠和回肠的细菌区系显著不同。     

Reflux of bile acids from the duodenum into the rumen of cows with a reduced intestinal passage

The purpose of this study was to find out whether the concentration of bile acids in the rumen of healthy cows differs from that of cows with a reduced gastrointestinal passage. The investigations were performed on 277 heifers and cows of the Swiss Braunvieh, Simmental and Swiss Holstein breeds. Forty of these had traumatic reticuloperitonitis, 30 had right or left abomasal displacement, 14 had an ileus of the duodenum, 36 had an ileus of the jejunum and 54 had a caecal dilatation. The other 103 animals had disorders which did not affect the digestive system and were used as controls. The mean (+/- se) bile acid concentration in the rumen fluid of the control animals was 1.0 +/- 0.30 mumol/litre. The bile acid concentrations in the rumen fluid of the cows with a duodenal or jejunal ileus were significantly higher than those of the other groups, demonstrating that bile acids may reflux from the duodenum into the rumen of cows with an ileus in the small intestine.     

Consequences of failure of the reticular groove reflex in veal calves fed milk replacer

Summary

A number of problems seen in veal calves are associated with insufficient adaptation to the changes in husbandry connected with the fattening system. These problems include chronic tympanitis, chronic vomiting, cachexia, unthriftiness, abomasal erosions and ulcers.

Some of these problems are associated with failure of the reticular groove reflex, and result in ruminal drinking.

Persistent ruminal drinking causes a syndrome characterised by a variety of symptoms such as unthriftiness, severe growth retardation, inappetence, recurrent tympany, abdomal distension, a long dry haircoat and clay‐like faeces.

Clinical studies performed to investigate the pathogenesis of the syndrome are described. It was found that the milk was stored in the rumen and was partly broken down. The presence of milk in the rumen induced typical changes in the ruminal mucosa (hyper/parakeratosis) and also inhibited casein clot formation in the abdomasum. The small intestinal mucosa showed villous atrophy. After training, the reticular groove reflex was re‐established in a number of patients but the growth rate of these calves did not return to normal.     

Effects of level of feeding and ruminally undegraded protein on ruminal bacterial protein synthesis, escape of dietary protein, intestinal amino acid profile, and performance of dairy cows.

Six cannulated lactating cows were used in two replicated, concurrently run 3 x 3 Latin square experiment to study the interaction between level of feeding and diets differing in ruminally undegraded protein (RUP) on bacterial protein synthesis, ruminal escape of dietary protein, and flow of total and individual amino acids (AA) to the small intestine. Treatments consisted of three diets formulated to contain 69 g (HL), 53 g (HH), and 48 g (LL) of RUP per kilogram of DM, respectively. Measurements were made in early lactation, at high feeding level (19.3 kg DM/d), and repeated at late lactation (9.8 kg DM/d, low feeding level) with the same animals and diets. Decreasing feed intake increased (P < .05) the apparent digestibility of OM, NDF, and ADF in the rumen and the total tract, decreased (P < .05) ruminal liquid and particulate passage rate and total ruminal VFA concentration, and increased ruminal pH and ammonia concentration. Decreased level of intake reduced the (P < .05) efficiency of bacterial N synthesis (28.1 vs 23.7 g bacterial N/kg OM truly digested in the rumen) and decreased (P < .05) ruminal protein degradation rate measured with an in situ method. Duodenal flow of nonammonia nitrogen (NAN), and total AA were highest (P < .05) for the HL diet and lowest (P < .05) for the LL diet at the high feeding level. However, at the low feeding level, diet composition did not affect the amount of NAN or total AA passing to the small intestine. Diet HL increased the proportion of Met, His (P < .05), and Arg (P < .07) in the duodenal digesta at both feeding levels. When purines were used to calculate bacterial N synthesis, no differences between diets were detected. However, when diaminopimelic acid was used, highest bacterial N synthesis was detected for diet HH at the high feeding level. Diet HL supported the highest (P < .05) milk protein production at the high feeding level, and the highest (P < .05) milk protein content at the low feeding level. In conclusion, level of feeding and amount of RUP altered the amount and composition of AA presented to the cows.     

Effects of an abrupt increase of starch-rich concentrates in the diet of dairy cows on concentrations of volatile fatty acids in the rumen and large intestine and on myoelectric activity of the spiral colon

OBJECTIVES: To describe the effects of an abrupt increase of concentrates in the diet of dairy cows on myoelectric activity of the spiral colon and on fermentation patterns in the rumen and large intestine. ANIMALS: 6 healthy lactating Simmental x Red-Holstein cows. PROCEDURES: The diet of 6 cows implanted with bipolar electrodes in the spiral colon was changed from hay only to a ration of 50% hay:50% starch-rich concentrates during a period of 60 hours. Myoelectric activity of the spiral colon, concentrations of absolute and undissociated volatile fatty acids (VFA), and pH of ruminal and large intestinal contents were monitored before, during, and after the dietary change. RESULTS: Significant changes in patterns of myoelectric activity of the spiral colon were restricted to phases III and IV of the bovine migrating myoelectric complex and to propagation velocity. Significant alterations were not observed in pH or VFA concentrations in ruminal fluid, but pH decreased and VFA concentrations increased significantly in fecal specimens after the change of diet. CONCLUSIONS AND CLINICAL RELEVANCE: Although rumen fluid is of limited value for measurement of certain indicators of fermentation, fecal samples can be used for measurement of pH and VFA concentrations, which serve as indicators of fermentation patterns in the large intestine. Increased concentrations of VFA and low pH in large intestinal digesta have a minimal influence on myoelectric activity of the spiral colon. Increased luminal VFA concentrations are unlikely to play an important role in the etiopathogenesis of motility disorders of the large intestine in cattle.