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In a 4 x 4 Latin square experiment the effects of DM content and/or the extent of fermentation in grass silages on the pattern of rumen fermentation and rumen kinetics were studied. In a separate study two cows were used to measure the rate of degradation using the dacron bag technique. Four rumen cannulated dairy cows were used to measure rumen fermentation pattern, rumen kinetics were measured in three of these animals. Basal diets (70% of total DM) consisted of maize silage, moist ensiled beet pulp, moist ensiled maize gluten feed, moist ensiled brewers' grains and a concentrate mixture. The remainder of the diet (30% of total DM) was wilted grass silage (WGS), high moisture grass silage with molasses (MGS), high moisture silage with formic acid (FGS) or wilted grass silage with additional water (WW). All diets were fed as complete feeds. pH of the rumen fluid was lower on the MGS and FGS diets. Concentrations of total VFA, acetic acid, ammonia and branched-chain fatty acids (BCFA) were highest on high moisture diets (MGS and FGS). Rates of clearance and digestion of the organic matter (OM) fractions were or showed tendencies towards being negatively influenced by both MGS and FGS, but remained unaffected by WGS and WW. Degradability of the grass silages was influenced by fermentation in the silo (lower digestible fractions and higher soluble fractions), as were rates of degradation (higher). Results of the degradability measured on the basal diet ingredients were in agreement with published literature and showed a strong correlation between OM digestibility in vitro and the undigestible fraction.

Effects of carbohydrates in concentrate mixtures (starch vs. cell wall constituents) and in rate of rumen degradation (rapid vs. slow) on rumen fermentation and rumen kinetics were studied using a 4 x 4 Latin square design. The basal diets, which comprised 75% of total DM, consisted of wilted grass silage, maize silage and concentrates. The remainder consisted of barley (B), maize (M), pressed ensiled beet pulp (P) or moist ensiled maize bran (MB). All diets were fed as totally mixed rations (TMR). The pH of the rumen fluid and the total concentration of volatile fatty acids (tVFA) did not differ among diets. The major volatile fatty acids did differ between diets and were expressed as the non-glucogenic:glucogenic ratio (NGR), being lowest for B and highest for P. Differences in NGR could be explained by differences in the rate of degradation of starch and/or NDF, using nylon bag incubations. Concentrations of ammonia and branched chain fatty acids (BCFA) were higher for diet MB and corresponded with the availability of nitrogen and energy for microbial protein synthesis, which was also reflected in the amount of bacterial protein in the rumen. Degradability was lower for maize starch compared with starch from barley. The rates of digestion measured in sacco and from rumen evacuations were similar for organic matter and N, but the nylon bag method showed a lower estimate for starch and NDF. The large particle fraction of mean total rumen contents consisted mainly of cell wall constituents and did not differ between diets. (Abstract retrieved from CAB Abstracts by CABI’s permission)

A feeding trial was carried out with 64 multiparous dairy cows, in which the effect of type of carbohydrate in concentrate mixtures (starch vs. cell wall constituents) and differences in rumen degradation (fast vs. slow) on feed intake and milk yield were studied. The experiment started immediately after parturition and lasted for 15 wk. The basal diet, which comprised 75% of the total DM intake, consisted of wilted grass silage, maize silage and concentrates. The remaining part of the diet consisted of barley (B), maize (M), pressed ensiled beet pulp (P) or moist ensiled maize bran (MB). All diets were given as totally mixed rations. Total intake of DM and net energy did not differ between diets, but differences were found in energy partition. There was a tendency for cows given diet B to show increased liveweight gain, while cows given P mobilized more body reserves compared with the other treatments. Milk yield did not differ between diets, but milk fat content was higher for diet P. Milk protein content was higher for diets B and M compared with P and MB. The lower protein content of the milk of treatment P can be explained by a longer period of negative energy balance, while the lower milk protein in cows given diet MB probably resulted from reduced microbial protein synthesis. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Dutch Landrace X Large White pigs 14 to 15 weeks old and about 45 kg were fed on low-protein diets (16.1%) and supplemented with lysine, orally, by slow or rapid jugular infusion or by slow portal/caval infusion in order to evaluate the bioavailability of lysine with type of treatment. Elimination rate after intravenous treatment had a half-life of 2.0+or-1.6 h (after bolus injection) or 3.7+or-1.9 h (after slow infusion). Absorption of an oral dose of lysine from the intestine (half-life of 3.6+or-0.9 h) was slower than elimination rate (half-life of 0.9+or-0.3 h). No significant liver first-pass effects could be detected and bioavailability of lysine after enteral intake was 82+or-6%. Analysis of plasma kinetics of amino acids may provide a valuable tool to evaluate bioavailability of dietary amino acids. (Abstract retrieved from CAB Abstracts by CABI’s permission)

A feeding trial was carried out with 56 dairy cows during 1st 18 weeks of lactation. Rations consisted of 40% grass and maize silage (in a 50:50 ratio) and 60% concentrates based entirely on by-products (beet pulp, maize gluten feed and brewers' grains) and were offered ad lib. 60% (on DM basis) of concentrates were given either ensiled (WET) or dehydrated (DRY). Half of the cows receiving WET or DRY diets also received an additive containing approx. 80 g of calcium salts of iso-butyrate, 2-methyl butyrate, 3-methyl butyrate and valerate. No significant effects of additive on feed intake, milk yield and milk composition were found. Feed, energy and protein intake and milk protein production were significantly lower after feeding WET diet compared with DRY diet. (Abstract retrieved from CAB Abstracts by CABI’s permission)

The 9 cows used in the preceding trial [see DSA 39, 2470] were allocated during the dry period (approx. 8 wk) to 3 levels of aldrin, heptachlor and beta -hexachlorocyclohexane ( beta -BHC) mixed with the concentrate ration. The daily dosages/cow were (i) 0.5, (ii) 1 or (iii) 2 mg of each pesticide. Because the date of parturition could only be predicted roughly, the dry period/cow varied resulting in large differences in total doses for cows within a group; mean total dose of each pesticide was (i) 26, (ii) 56 and (iii) 87 mg/cow. The pesticide levels in milk fat after parturition did not only represent the effect during the dry period because the cows had also been dosed with pesticides late in the preceding lactation. Aldrin and heptachlor residues in milk fat were below the detection limit of 0.01 mg/kg and content of beta -heptachlor epoxide was