We divided the adhesion process of the predominant cellulolytic rumen bacteria Fibrobacter succinogenes, Ruminococcus flavefaciens, and Ruminococcus albus into four phases: 1) transport of the nonmotile bacteria to the substrate; 2) initial nonspecific adhesion of bacteria to unprotected sites of the substrate that is dominated by constitutive elements of bacterial glycocalyx; 3) specific adhesion via adhesins or ligands formation with the substrate, which can be dominated by several bacterial organelles including cellulosome complexes, fimbriae connections, glycosylated epitopes of cellulose-binding protein (CBP) or glycocalyx, and cellulose-binding domain (CBD) of enzymes; 4) proliferation of the attached bacteria on potentially digestible tissues of the substrate. Each of the phases and its significance in the adhesion process are described. Factors affecting bacterial adhesion are described including: 1) factors related to bacterial age, glycocalyx condition, and microbial competition; 2) factors related to the nature of substrate including, cuticle protection, surface area, hydration, and ionic charge; and 3) environmental factors including pH, temperature, and presence of cations and soluble carbohydrate. Based on the information available from the literature, it appears that each of the predominant rumen bacteria--F. succinogenes, R. flavefaciens, and R. albus--has a specific mechanism of adhesion to cellulose. In F. succinogenes, both the glycosidic residues of the outer membrane CBP and especially of the 180-kDa CBP, and the distinct CBD of EG2 EGF and Cl-stimulated cellobiosidase, may play a role in the adhesion to cellulose. No direct evidence, except scanning electron microscopy observations, yet supports the existence of either cellulosome complex or fimbriae structures involved in the adhesion mechanism of F. succinogenes. At least two mechanisms, cellulosome-like complexes and carbohydrate epitopes of the glycocalyx layer are involved in the specific adhesion of R. flavefaciens to cellulose. Ruminococcus albus possesses at least two mechanisms for specific adhesion to cellulose: a cellulosomal-like mechanism, and a CbpC (Pil)-protein mechanism that probably involves the production of fimbrial-like structures. Indirect and direct studies suggested that carbohydrate epitopes of CBPs and CBD epitope of cellulases may also be involved mostly in the nonspecific phase of adhesion of R. albus.

Conjugated linoleic acid (CLA), a naturally occurring anticarcinogen found in dairy products, is a byproduct of incomplete ruminal biohydrogenation of unsaturated fatty acids. Our objective was to determine the effect of nonstructural carbohydrate sources, addition of full fat extruded soybeans as a source of unsaturated fatty acids, and possible interactions on the milk fat content of CLA. Cows (n = 20) were assigned to a 4 x 4 Latin square involving two sources of nonstructural carbohydrate, high starch (corn) or high pectin (citrus pulp), with or without addition of extruded soybeans. Milk yield was not affected by nonstructural carbohydrate source, but milk production was increased by 7.8 to 10.5% with dietary additions of extruded soybeans. Milk fat content did not differ between treatments, but fatty acid composition was affected. Cows fed extruded soybean diets had reduced concentrations of C8 to C16 fatty acids and increased concentrations of octadecenoic acids. Diets with extruded soybeans also resulted in more than a doubling in milk fat concentration and yield of CLA. Nonstructural carbohydrate source had only minor effects on CLA, and there was no interaction with extruded soybeans. Milk fat content of trans-C18:1 and CLA were closely related (r2 = 0.77). However, variation among cows was about threefold for each of the diets and rank order of individual cows differed among diets. Overall, we demonstrated that diet modification can be used to alter CLA content of milk fat, but there was substantial individual cow variation for all diets.

The aim of the study was to determine the effect of 10 sources of lactic acid bacteria (LAB) on dry matter digestibility (DM-D) and neutral detergent fiber digestibility (NDF-D), in various combinations with starch, in vitro. The soluble starch represented a concentrate feed, whereas silage represented feeding only roughage. The DM-D and NDF-D were determined after 24 and 48 h of incubation to represent effective (24 h) and potential (48 h) digestibility. Addition of LAB was both by direct application of the inoculants to rumen fluid (directly fed microbials) and by the use of preinoculated silages. For each feed combination, tubes without added LAB served as controls. The results indicate that, overall, some LAB inoculants applied at ensiling or added directly to the rumen fluid had the potential to increase the DM-D and NDF-D. The major significant inoculant effect on NDF-D was obtained after 24 h of incubation, whereas the effect after 48 h was mainly nonsignificant. The effective inoculants seemed to minimize the inhibitory effect of the starch on NDF-D within 24 h, perhaps by competition with lactate-producing rumen microorganisms.

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Nonforage byproduct feeds, including distillers dried grains (DDG), corn gluten feed (CGF), wheat bran (WB), beet pulp (BP), soybean hulls (SH), and dried citrus pulp (DCP), were examined for monosaccharide composition and in vitro digestibility by ruminal liquor. The dicotyledonous feeds (BP, SH, and DCP) contained more galactose, pectin, and NDF glucans and less NDF-xylan and NDF-arabinose than the monocotyledonous ones (DDG, CGF, and WB). The lowest values of lignin were found in CGF, SH, and DCP. Digestibility of total carbohydrate was around 90% in CGF, DCP, BP, and SH and around 80% in DDG and WB. Digestibility of total NDF polysaccharides was 86% in CGF and SH, 78--84% in DDG, DCP, and BP, and 56% in WB. In all byproducts, digestibility of NDF glucose and arabinose was higher than that of NDF xylose and uronic acids.

The potential of pellets made of soy hulls (SH) and corn gluten feed (CGF) to replace starchy pelleted supplement in diets of lactating cows was measured in a feeding regime comparable to automatic milking systems. Twenty-four cows were divided into 2 equal groups and fed for 7 wk in individual feeders monitored by computer on one of the 2 experimental diets. Both diets contained 75% basic total mixed ration plus an additional 25% of pelleted supplement (17% CP), being either high starch pellets (HST) in treatment, or pellets made of SH + CGF (2:1) (SHCG) in treatment. In vitro dry matter digestibility was higher in the HST pellets, whereas neutral detergent fiber (NDF) digestibility was higher in the SHCG pellets. The NDF content was higher in the SHCG diet. Individual cow behavior at the feeding lane was analyzed during the experimental period. Average number of meals and daily eating duration of the SHCG cows were significantly greater, as compared with the HST group. However, intake per meal and rate of eating were greater in the HST cows, whereas meal duration was similar in both groups. Feeding behavior resulted in significantly higher daily dry matter and NDF intake by the SHCG cows (27.1 and 11.1 kg, respectively) as compared with the HST group (24.8 and 7.61 kg, respectively). Consequently, significantly higher milk fat content, milk fat yield, and 4% FCM yield were obtained in the SHCG cows. Milk and milk protein yields were similar in both treatments. Data suggest potential advantages of the SHCG pellets for herds using automatic milking systems.

I. The changes in the solubility of calcium, magnesium and phosphorus in digesta flowing along the intestinal tract and the net movement across the intestinal wall of these elements were determined in six rams, each equipped with three T-shaped cannulas; cannulas were placed in a total of six different sites of the small intestine. CrzO, was used as a marker substance to measure the rate of flow of the digesta.2. The concentrations of soluble Ca, Mg and P decreased as digesta moved along the intestine. The greatest fall in soluble Ca occurred after the first 3 m of the intestine, while a significant decrease in soluble Mg was found only at 15 and 25 m from the pylorus. The concentration of soluble P in digesta decreased until the 7 m site and then remained stable. In the faeces, the level of soluble Mg was approximately 4 times higher than, and that of Ca equal to, the levels of Mg and Ca found in digesta flowing through the upper intestine. Unlike Ca and Mg, a very low concentration of soluble P was found in the faeces. 3.In the duodenum, 84, 78 and 62 yo of the total Ca, Mg and P respectively were soluble, whereas in the digesta flowing through the terminal ileum the corresponding values were 3.2, 7.2 and 19 % for Ca, Mg and P respectively. 4.The forestomachs and the colon were found to be the main sites of Mg net absorption;1.12 mmol/h was apparently absorbed from the stomach and 1.05 mmol/h from the colon.The upper small intestine (1-3 m from the pylorus) appeared to be the major site of Ca and P absorption. 5.In the last 10 m of the small intestine, considerable amounts of minerals were secreted; 4'70, 0.96 and 1.85 mmol Ca, Mg and P/h respectively were added to the digesta flowing between 15 and 25 m from the pylorus. The effect of the increase in the pH of digesta along the small intestine on the solubility of these minerals is discussed.