Effect of rumen ciliates on the digestion of different carbohydrates in sheep. I.--Utilization of cell wall carbohydrates (cellulose and hemicellulose) and of starch

Two diets rich in cell-wall carbohydrates or starch were given to 10 rumen-fistulated sheep; two sheep were defaunated and the others were inoculated with Polyplastron multivesiculatum (P) or Entodinium sp. (E), or both (P + E), or with conventional fauna. Ciliate biomass was greater when the animals were fed a high starch diet than when the diet was rich in cell-wall carbohydrates (table 2). With both diets, the Entodinium genus in the mixed fauna sampling predominated. We showed that Polyplastron was directly involved in cell-wall carbohydrate breakdown, while Entodinium capacity to digest cellulose remained low. We noted that with a diet rich in cellulose and hemicellulose, bacterial cellulolytic activity was improved by the presence of ciliates in the rumen but was decreased with the "starch" diet (table 3). The greater VFA concentration observed in the faunated animals expressed ciliate effect on the fermentations as well as activation of bacterial metabolism. With a high starch diet, the Entodinium sp. ciliates may have a buffering effect on the pH values in the rumen by limiting bacterial fermentation after food intake and by prolonging starch digestion during the day (table 4). The composition of the VFA mixture was modified by ciliate inoculation. The molar proportion of butyric acid always increased, while that of acetic and propionic acids evolved differently according to the diets and the ciliates (table 4). The higher ammonia concentration in the rumen liquor observed in faunated animals (table 4) could be explained either by the breakdown of both feed and bacterial proteins ingested by ciliates or by a lower ammonia nitrogen incorporation by fewer bacteria. Statistical analyses were used to explain the specific effect of P and E and also the interactions between them and between each of them and the diets.     

Nitrogen utilisation by dairy cows fed diets differing in crude protein level with a deficit in ruminal fermentable nitrogen

We studied the efficiency of nitrogen utilisation by dairy cows, using three diets differing in the crude protein (CP) level but with similar deficits (10 g x kg(-1) dry matter, DM) in ruminal fermentable nitrogen. There was no difference in milk yield from the cows offered the three diets (130, 145 and 160 g CP x kg(-1) DM). The milk protein content differed between the two most extreme diets (28.9 vs. 29.9 g x kg(-1), P < 0.05), resulting in higher protein yields for the highest CP treatment (P < 0.01). The efficiency of nitrogen utilisation, calculated as the proportion of ingested nitrogen recovered in the milk, was significantly higher for the 130 g CP x kg(-1) DM diet than for the other two diets (0.37 vs. 0.33 and 0.32 respectively. P < 0.01). The different diets also resulted in different levels of nitrogen excretion into the environment (237, 270 and 330 g N x d(-1), P < 0.01). Hepatic deamination of the amino acids may have generated additional energy to enable the animal to make use of the additional nitrogen in the diet, resulting in an increase in plasma urea concentration.     

Proteolytic activity of ruminal digesta during the feeding cycle in sheep receiving grass hay/concentrate or maize silage/concentrate diets

Proteolytic activity was measured by the digestion of 14C-labelled casein in digesta removed from the rumen of four sheep receiving a grass hay/concentrate diet and four sheep receiving a maize silage/concentrate diet. Samples were removed immediately before feeding and at 2-h intervals after feeding up to 12 h. Animals on both diets produced similar proteolytic activities (1.83 (S.D. 0.41) and 2.14 (S.D. 0.61) mg 14C-casein hydrolysed (ml ruminal fluid)-1 h-1 with the maize silage- and grass hay-based diets, respectively). Time after feeding had no effect on proteolytic activity, but between-animal variation was consistent and highly significant, with the highest-activity animals having activities 64 and 74% higher than the lowest-activity animals on the two diets, respectively.     

Reducing dietary protein in dairy cow diets: implications for nitrogen utilization,milk production,welfare and fertility

In light of increasing global protein prices and with the need to reduce environmental impact of contemporary systems of milk production, the current review seeks to assess the feasibility of reducing levels of dietary CP in dairy cow diets. At CP levels between 140 and 220 g/kg DM there is a strong positive relationship between CP concentration and dry matter intake (DMI). However, such effects are modest and reductions in DMI when dietary CP is below 180 g/kg DM can be at least partially offset by improving the digestibility and amino acid profile of the undegradable protein (UDP) component of the diet or by increasing rumen fermentable energy. Level and balance of intestinally absorbable amino acids, in particular methionine and lysine, may become limiting at lower CP concentrations. In general the amino acid composition of microbial protein is superior to that of UDP, so that dietary strategies that aim to promote microbial protein synthesis in the rumen may go some way to correcting for amino acid imbalances in low CP diets. For example, reducing the level of NDF, while increasing the proportion of starch, can lead to improvements in nitrogen (N) utilisation as great as that achieved by reducing dietary CP to below 150 g/kg. A systematic review and meta-analysis of responses to rumen protected forms of methionine and lysine was conducted for early/mid lactation cows fed diets containing ⩽150 g CP/kg DM. This analysis revealed a small but significant (P=0.002) increase in milk protein yield when cows were supplemented with these rumen protected amino acids. Variation in milk and milk protein yield responses between studies was not random but due to differences in diet composition between studies. Cows fed low CP diets can respond to supplemental methionine and lysine so long as DMI is not limiting, metabolisable protein (MP) is not grossly deficient and other amino acids such as histidine and leucine do not become rate limiting. Whereas excess dietary protein can impair reproduction and can contribute to lameness, there is no evidence to indicate that reducing dietary CP levels to around 140 to 150 g CP/kg DM will have any detrimental effect on either cow fertility or health. Contemporary models that estimate MP requirements of dairy cows may require refinement and further validation in order to predict responses with low CP diets.     

Urease activity of adherent bacteria and rumen fluid bacteria

In experiments on six sheep fed on a low nitrogen diet (3.7 g N/day), urease (EC 3.5.1.5) activity (nkat X mg-1 bacterial dry weight) 3 h after feeding was found to be highest in the bacteria adhering to the rumen wall (13.25 +/- 2.10), lower in the rumen fluid bacteria (8.96 +/- 1.35) and lowest in the bacteria adhering to feed particles in the rumen (5.69 +/- 2.13). The urease activity of bacteria adhering to the rumen wall and of the rumen fluid bacteria of six sheep fed on a high nitrogen diet (21 g N/day) was significantly lower than in sheep with a low N intake and in both cases was roughly the same (3.81 +/- 1.37 and 3.76 +/- 1.02 respectively); it was lowest in bacteria adhering to feed particles in the rumen (1.92 +/- 0.90). It is concluded from the results that the urease activity of rumen fluid bacteria and of bacteria adhering to the rumen wall and to feed particles in the rumen is different and that it falls significantly in the presence of a high nitrogen intake. From the relatively high ureolytic activity of bacteria adhering to the rumen wall in the presence of a low nitrogen intake it is assumed that this is one of the partial mechanisms of the hydrolysis of blood urea entering the rumen across the rumen wall and of its reutilization in the rumen-liver nitrogen cycle in ruminants.     

Nitrogen levels in low-roughage diets for efficient rumen microbial protein production

The influence of dietary nitrogen (N) available in the rumen on the efficiency of microbial protein production was examined for 43 predominantly low-roughage diets given to cattle or sheep with rumen and duodenal (re-entrant) cannulae. The minimum amount of available N required for efficient microbial protein production was 2.0 g/100 g of organic matter actually digested in the rumen. When the diet supplied 2.7 g of available N/100 g of organic matter actually digested in the rumen, there was no net utilisation of recycled N.From this information, concentrations of N in organic matter required in low-roughage diets differing in organic matter digestibility and availability of dietary N have been calculated. Also a method of calculating the quantities of amino acid N and of particular amino acids absorbed from the small intestine from a knowledge of the diet composition is presented.     

Digestion, rumen fermentation and circulating concentrations of insulin, growth hormone and IGF-1 in steers fed diets based on different proportions of maize silage and grass silage

Replacing grass silage with maize silage results in a fundamental change in the ratio of structural to non-structural carbohydrates with commensurate changes in rumen fermentation patterns and nutrient utilisation. This study investigated the effects of feeding four forage mixtures, namely grass silage (G); 67 g/100 g grass silage + 33 g/100 g maize silage (GGM); 67 g/100 g maize silage + 33/100 g grass silage (MMG); maize silage (M) to four ruminally and duodenally canulated Holstein Friesian steers. All diets were formulated to be isonitrogenous (22.4 g N/kg DM) using a concentrate mixture. Dietary dry matter (DM) and organic matter (OM) digestibility increased with ascending maize silage inclusion (P < 0.1) whereas starch and neutral detergent fibre digestibility declined (P < 0.05). Ratio of non-glucogenic to glucogenic precursors in the rumen fluid increased with maize silage inclusion (P < 0.01) with a commensurate reduction in rumen pH (P < 0.05). Mean circulating concentrations of insulin were greatest and similar in diets MMG and GGM, lower in diet M and lowest in diet G (P < 0.01). There were no effects of diet on the mean circulating concentration of growth hormone (GH), or the frequency, amplitude and duration of GH pulses, or the mean circulating concentrations of IGF-1. Increasing levels of DM, OM and starch intakes with the substitution of grass silage with maize silage affected overall digestion, nutrient partitioning and subsequent circulating concentrations of insulin.     

Dietary sodium alginate administration affects fingerling growth and resistance to Streptococcus sp. and iridovirus, and juvenile non-specific immune responses of the orange-spotted grouper, Epinephelus coioides

The percent weight gain (PWG) and feeding efficiency (FE) of fingerling orange-spotted grouper, Epinephelus coioides, fed diets containing sodium alginate at 1.0 and 2.0 g kg(-1) were calculated on the 2nd, 4th, 6th, and 8th weeks after feeding. Survival rates of the fingerling grouper against Streptococcus sp. and an iridovirus, and non-specific immune parameters such as alternative complement activity (ACH50), lysozyme activity, natural haemagglutination activity, respiratory bursts, superoxide dismutase (SOD) activity, and phagocytic activity of juvenile grouper were also determined when the fish were fed diets containing sodium alginate at 0.5, 1.0, or 2.0 g kg(-1). The PWG and FE of fish were better when the fish were fed diets containing sodium alginate at 1.0, and 1.0 and 2.0 g kg(-1), respectively. The PWG and FE of fish fed the 0, 1.0 and 2.0 g kg(-1) sodium alginate-containing diets after 8 weeks were 271.0%, 454.4% and 327.8%, and 0.61, 0.72 and 0.68, respectively. Fish fed a diet containing sodium alginate at the level of 2.0 g kg(-1) had a significantly higher survival rate than those fed the control diet after challenge with Streptococcus sp. and an iridovirus causing an increase of survival rate by 25.0% and 16.7%, respectively, compared to the control group. The ACH(50) level of fish fed the sodium alginate-containing diets at 2.0 g kg(-1) was significantly higher than those fed the 1.0 g kg(-1) sodium alginate diet and control diet after 12 days, and had increased to 1.9-fold, compared to those fed the control diet. The lysozyme activity, phagocytic activity, respiratory bursts, and SOD level of fish fed the sodium alginate-containing diets at 1.0 and 2.0 g kg(-1) were significantly higher than those fed the control diet after 12 days, and had increased to 1.97- and 1.68-fold, 1.35- and 1.50-fold, 1.63- and 1.81-fold, and 1.23- and 1.31-fold, respectively, compared to those fed the control diet. We therefore recommend dietary sodium alginate administration at 1.0 and 2.0 g kg(-1), respectively, to promote growth and enhance immunity and resistance against Streptococcus sp. and an iridovirus.     

Narrow-leaved lupine seeds as a dietary protein source for fattening rabbits: a comparison with white lupine seeds

Lupine seeds have the potential to be an alternative to imported dietary proteins. In rabbits, it has been indicated that White lupine seed (WLS) is a suitable protein source. Other lupine species, for example, narrow-leaved lupine seed (NLS), have not yet been tested in rabbit diets. Two experiments were carried out to evaluate the effect of the dietary inclusion of NLS on growth performance, sanitary risk index (SRI), coefficients of total tract apparent digestibility (CTTAD) and nitrogen output in fattening rabbits. Narrow-leaved lupine was compared with WLS as a main protein source. For Experiment I, a total of 198 Hyplus rabbits (37 days of age) were allocated into two groups (99 rabbits per group), fed the WLS I diet (120 g/kg of WLS cv. Amiga) or the NLS I diet (150 g/kg of NLS cv. Probor), and used for performance and carcass trait evaluations. In addition, the CTTAD of the diets and the nitrogen output were determined in 10 Hyplus rabbits per treatment (37 days of age). For Experiment II, a total of 180 Hyplus rabbits (32 days of age) were allocated into two groups (90 rabbits per group), fed the WLS II diet (120 g/kg of WLS cv. Amiga) or the NLS II diet (130 g/kg of NLS cv. Primadona), and used for performance and carcass trait evaluations. In addition, the CTTAD of the diets was determined in 10 Hyplus rabbits per treatment (32 days of age). Regardless of the treatment, the dietary inclusion of NLS had a negative effect on growth of the rabbits. The nitrogen excretion and coefficients of nitrogen retention of rabbits were not affected by the treatments. In Experiment I, SRI (37 to 80 days of age) was higher in rabbits fed the NLS I diet than in those fed the WLS I diet (38.4% v. 23.2%, respectively; P = 0.031). Similarly, in Experiment II (32 to 74 days of age), SRI was higher in rabbits fed the NLS II diet than in rabbits fed the WLS II diet (37.8% v. 23.3%, respectively; P = 0.052). In conclusion, regardless of the variety, the dietary inclusion of NLS had no negative effect on the nitrogen output or dressing-out percentage of rabbits when compared to those of rabbits fed the WLS diets. With respect to the SRI and performance, however, NLS did not provide a satisfactory outcome.     

Lotus corniculatus condensed tannins decrease in vivo populations of proteolytic bacteria and affect nitrogen metabolism in the rumen of sheep

Condensed tannins in forage legumes improve the nutrition of sheep by reducing ruminal degradation of plant protein and increasing crude protein flow to the intestine. However, the effects of condensed tannins in forage legumes on rumen bacterial populations in vivo are poorly understood. The aim of this study was to investigate the specific effects of condensed tannins from Lotus corniculatus on four proteolytic rumen bacteria in sheep during and after transition from a ryegrass (Lolium perenne)-white clover (Trifolium repens) diet (i.e., low condensed tannins) to a Lotus corniculatus diet (i.e., higher condensed tannins). The bacterial populations were quantified using a competitive polymerase chain reaction. Lotus corniculatus was fed with or without ruminal infusions of polyethylene glycol (PEG), which binds to and inactivates condensed tannins, enabling the effect of condensed tannins on bacterial populations to be examined. When sheep fed on ryegrass-white clover, populations of Clostridium proteoclasticum B316T, Butyrivibrio fibrisolvens C211a, Eubacterium sp. C12b, and Streptococcus bovis B315 were 1.5 x 10(8), 1.1 x 10(6), 4.6 x 10(8), and 7.1 x 10(6) mL(-1), respectively. When the diet was changed to Lotus corniculatus, the average populations (after 8-120 h) of C. proteoclasticum, B. fibrisolvens, Eubacterium sp., and S. bovis decreased (P < 0.001) to 2.4 x 10(7), 1.1 x 10(5), 1.1 x 10(8), and 2.5 x 10(5) mL(-1), respectively. When PEG was infused into the rumen of sheep fed Lotus corniculatus, the populations of C. proteoclasticum, B. fibrisolvens, Eubacterium sp., and S. bovis were higher (P < 0.01-0.001) than in sheep fed Lotus corniculatus without the PEG infusion, with average populations (after 8-120 h) of 4.9 x 10(7), 3.8 x 10(5), 1.9 x 10(8), and 1.0 x 10(6), respectively. Sheep fed the Lotus corniculatus diet had lower rumen proteinase activity, ammonia, and soluble nitrogen (P < 0.05-0.001) than sheep that were fed Lotus corniculatus plus PEG. The Lotus corniculatus diet reduced rumen nitrogen digestibility (P < 0.05) and ammonia pool size and increased the flow of undegraded feed nitrogen to the abomasum. The nitrogen intake, rumen non-ammonia nitrogen pool size, rumen microbial non-ammonia nitrogen pool size, and abomasal microbial non-ammonia nitrogen fluxes were similar both in sheep fed only Lotus corniculatus and in sheep fed Lotus corniculatus plus PEG, but nonmicrobial non-ammonia nitrogen flux to the abomasum was higher (P < 0.01) for the sheep fed only Lotus corniculatus. Although condensed tannins in Lotus corniculatus reduced the populations of some proteolytic bacteria, total ruminal microbial protein and microbial protein outflow to the abomasum were unchanged, suggesting a species-specific effect of condensed tannins on bacteria in the rumen.     

The effects of barley, unmolassed sugar-beet pulp and molasses supplements on organic matter, nitrogen and fibre digestion in the rumen of cattle given a silage diet

In a 4 × 4 Latin-square experiment with a 2 × 2 factorial arrangement of treatments, 4 cattle fitted with a rumen and duodenal cannula were given four grass-containing diets [480 g kg⁻¹ of the total dry matter (DM) intake] and barley (BU), barley + molasses (2:1) (BM), sugar-beet pulp (SU) or sugar-beet pulp + molasses (SM). Duodenal flow was estimated using Cr-mordanted straw and CoEDTA as markers, and microbial nitrogen entering the small intestine using purine bases of nucleic acids.

Molasses-containing diets had a higher (P < 0.01) organic matter (OM) digestibility. The proportion of digestible OM apparently disappearing in the rumen averaged 0.72 and was not significantly affected by the diet. When cattle received molasses, the quantity of microbial N entering the small intestine was higher (P < 0.05) and there was a trend towards a higher efficiency of microbial N synthesis (28.8 vs. 25.6 g N kg⁻¹ OM apparently digested in the rumen). When S diets were consumed, total non-ammonia N flow at the duodenum exceeded N intake by 7.0 g day⁻¹ and when B diets were consumed, it was 0.7 g day⁻¹ less than N intake. Feed N degradability in the rumen and apparent N digestibility of S diets were lower (P < 0.05; P < 0.001) than those of B diets.

Rumen (P < 0.05) and total (P < 0.001) digestibility of neutral detergent fibre (NDF) and acid detergent fibre (ADF) was higher when S diets were given. The proportion of digestible fibre disappearing in the rumen was not affected by the diet. The rate and extent of silage and hay DM degradation were not significantly affected by the diet. However, dietary inclusion of molasses decreased (P < 0.05) the lag time of both hay and silage DM degradation.

The rumen dilution rate of liquid averaged 0.097 and that of particles, 0.049; neither was significantly different for either B and S diets or U and M diets. Duodenal liquid flow was higher (P < 0.05) for M diets.

Average rumen pH was not affected by the diet, but the molasses diets increased (P < 0.05) the range in rumen pH. The BM diet was associated with higher (P < 0.01) rumen ammonia concentration than the other diets. Low rumen ammonia concentrations (< 2 mM) were observed for long periods between feeds. The molar proportion of butyrate was higher on B diets and there was a trend towards a higher proportion of acetate and propionate on S diets. Molasses tended to increase the molar proportion of propionate and butyrate.     

Why does the establishment of the starch preferring<Emphasis Type="Italic">Entodinium caudatum</Emphasis> in the rumen decrease the numbers of the fibrolytic ciliate<Emphasis Type="Italic">Eudiplodinium maggii</Emphasis>?

The effect of the establishment of Entodinium caudatum on the population of Eudiplodinium maggii was examined in the rumen of three sheep fed a hay/ground barley diet. The cell concentration of E. maggii were 15.9-38.5 and 11.7-12.4 x 10(3) cells per g of the rumen contents in the absence and presence of E. caudatum, respectively. Microscopic analysis showed that starch was the only material engulfed by eudiplodinia irrespective of the time after feeding and the presence or absence of E. caudatum. Up to 82-93% of individuals contained starch grains when E. maggii was the only ciliate species in the rumen; the proportion was 70-77% after entodinia had been established. The largest quantity of starch engulfed by E. maggii ciliates was 12.4-19.0 and 6.7-7.6 mg per 100 mg protozoal dry mass in the absence and presence of entodinia, respectively. No visible engulfment of hay was observed in vivo in spite of the fact that hay particles up to 42 microns in length were dominating in rumen fluid. Ingestion of fresh particles of hay separated from the rumen digesta was found when they were added in the proportion of 1 g per 40 mL suspension of ciliates. No preferential intake of starch was observed when E. maggii ciliates were incubated in vitro with a mixture of hay and barley starch. It is suggested that competition for starch between the two ciliate species was responsible for the drop in the numbers of E. maggii. This could result from a too low concentration of small particles of hay in the rumen fluid.     

Substrate specificity in the control of digestive enzymes in larvae of the black carpet beetle

When starved larvae of the black carpet beetle, Attagenus megatoma, were fed selected diets, increases in proteolytic, trypsin, and chymotrypsin activity were correlated with total midgut protein and not with the amount of food consumed. Although larvae initially consumed more of a starch diet than of 2 diets that contained added protein, total protease activity in these larvae was minimal. Starch-fed larvae and larvae fed a casein-sucrose diet had a consistently higher level of sucrase activity than larvae fed an all-casein diet. These total results support a secretagogue mechanism for control of digestive enzyme synthesis in insects. In addition, the absence of parallel stimulation of different digestive enzymes by a single substrate (starch) indicated nutrient class specificity in the control of inducible midgut enzymes in this species.     

Responses to dietary starch or sucrose on protein and glucose kinetics in goats fed a high-concentrate diet

Responses of whole body protein synthesis (WBPS) and glucose irreversible loss rate (ILR) were compared between dietary starch and sucrose in four male goats. Diets were fed at 1.2 times maintenance requirements of ME and CP with 30% of the ME as starch, starch plus sucrose or sucrose, twice daily. The diets consisted of 33, 32, 11 and 24% of alfalfa hay, corn, soybean meal and the carbohydrates, respectively. The WBPS and glucose ILR during 5-7 h after feeding were determined by an isotope dilution method of [2H5]phenylalanine, [2H2]tyrosine, [2H4]tyrosine and [13C6]glucose. Sucrose elevated ammonia nitrogen and lowered acetate concentrations in the rumen, but did not differ from starch in nitrogen retention. Glucose ILR and WBPS were similar between the carbohydrates. It was concluded that dietary sucrose would have effects similar to starch on WBPS and glucose kinetics in the absorptive state in goats fed a high-concentrate diet.     

Effects of soluble corn bran arabinoxylans on cecal digestion, lipid metabolism, and mineral balance (Ca, Mg) in rats

The effects of soluble corn bran arabinoxylans on cecal digestion, lipid metabolism, and mineral utilization [calcium (Ca) and magnesium (Mg)] were investigated in rats adapted to semipurified diets. The diets provided either 710 g/kg wheat starch alone (control) or 610 g/kg wheat starch plus 100 g/kg corn soluble fiber (arabinoxylans) and either 0 or 2 g/kg cholesterol (control + cholesterol and arabinoxylans + cholesterol, respectively). Compared with rats fed the control diets, rats fed the arabinoxylan diets had significant cecal hypertrophy (+50% after 3 days of the fiber adaptation) and an accumulation of short-chain fatty acids, especially propionic acid (up to 45% in molar percentage). Arabinoxylans enhanced the cecal absorption of Ca and Mg (from 0.07 to 0.19 micromol/min for Ca and from 0.05 to 0.23 micromol/min for Mg). Mg balance was enhanced by arabinoxylans (+25%). The arabinoxylan diet markedly reduced the cholesterol absorption from 50% of ingested cholesterol in controls up to approximately 15% in rats adapted to the arabinoxylans diet. Arabinoxylans were effective in lowering plasma cholesterol (approximately -20%). There was practically no effect of the diets on cholesterol in d > 1.040 lipoproteins (high density lipoproteins) whereas arabinoxylans were very effective in depressing cholesterol in d < 1.040 lipoproteins (especially in triglyceride-rich lipoproteins). Corn fermentable fiber decreased the accumulation of cholesterol in the liver. In parallel, the arabinoxylan diet counteracted the downregulation of 3-hydroxy-3-methylglutaryl-CoA by cholesterol. These data suggest that arabinoxylans may have a great impact on intestinal fermentation, mineral utilization, and cholesterol metabolism.     

Supplemental sodium phytate and microbial phytase influence iron availability in growing rats.

Five groups of individually housed albino rats (n = 7 each, initial average weight = 42 g) were fed diets based on corn starch and casein over a 4-week period. All diets were supplemented with 35 mg/kg of iron from FeSO4 x 7 H2O. Group I (control) was fed the basal diet free of phytic acid (PA) and phytase. By replacing corn starch by 7.5 g (groups II and IV) and 15 g phytic acid (groups III and V) from sodium phytate per kg diet, molar PA/iron ratios of 18 and 36 were obtained. In groups IV and V, 1000 U phytase from Aspergillus niger per kg diet were added. Food conversion efficiency ratio and growth rate as well as iron in plasma and spleen, hemoglobin, red blood cell count and erythrocyte zinc protoporphyrin were not influenced by the different dietary treatments. Dietary phytate reduced apparent iron absorption in groups II and III. Furthermore hematocrit, transferrin saturation and iron concentration in liver and femur were lowered in rats fed diets with PA, while total and latent iron-binding capacity of plasma increased. Microbial phytase supplementation (groups IV and V) partly counteracted the antinutritive effects of phytic acid on iron availability.     

Effect of bean (Vicia faba) extrusion on nitrogen and starch intestinal flux in lactating cows]

Four mature lactating Holstein cows fitted with permanent ruminal, duodenal and ileal cannulae were used to study the effect of extrusion at 195 degrees C of beans (Vicia faba cv Castel) on organic matter (OM), nitrogen (N) and starch degradation in the rumen and their flow to and absorption from the small intestine. The test protein sources, raw beans (RB) and extruded beans (EB), provided about 45% of the dietary protein. The diets were composed of 23.1% beans, 56.2% corn silage, 10.1% corn grain and 10.7% Italian rye-grass hay on a DM basis; the diets were isocaloric (4.5 Mcal/kg of DM) and isonitrogenous (14% of DM). Cr-EDTA, YbCl3 and purines were used as liquid, particulate and bacterial markers respectively. Extruding the beans did not influence intraruminal pH (6.6), ammonia-N (99 mg/l) and volatile fatty acids (97 mM/l) concentrations. Apparent digestibility in total tract of energy, OM, N and starch were not affected with inclusion of EB instead of RB, the corresponding mean values were: 66, 68, 64 and 95% of intake. Apparent ruminal digestion of OM, starch and N in the forestomach were 39, 58 and 52% for diets containing RB and 38, 72 and 45% for EB diets; efficiency of bacterial protein synthesis (gN/kg organic matter truly digested in the stomach) was higher for EN diets compared with RN diets (25 vs 22). Eating diets including EB increased non-ammonia-N, bacterial-N and dietary-N flows (g/d) to the duodenum compared with diets containing RB: 409 vs 366, 216 vs 194 and 193 vs 172 respectively; while starch flow was reduced (1.5 vs 2.2 kg/d) and OM flow was unchanged (9.8 kg/d). Apparent digestion from the small intestine (g/d) of nonammonia-N, bacterial-N and dietary-N were higher for EB diets: 268 vs 229, 181 vs 160 and 87 vs 69 respectively; meanwhile, starch digestion decreased (975 vs 1,612). The PDIA, PDIN and PDIE contents (g/kg of DM) of the RB were 33, 175 and 127 respectively; the corresponding values after extrusion were: 58, 147 and 178.     

Variation in proteinase activities in the rumen

Rumen fluid was taken from fistulated sheep and a cow receiving various diets based on grass hay or grass cubes with and without cereal-based concentrates. Proteinases in the extracellular fluid, and extracted from particulate material by Triton X-100, were visualized using SDS-PAGE in which gelatin was co-polymerized with the gels. Each animal sampled had a different pattern of proteinase activity. No single proteinase band predominated, although a few appeared in several samples, indicating that some microbial species were commonly involved in proteolysis but none was dominant. The banding patterns in samples taken from the same animals two weeks apart were fairly similar, indicating some stability within animals. Patterns obtained with extracellular fluid and Triton X100 extracts of small and large particulate material from the same sample were similar for the most part, although the relative intensity of the bands differed. The serine protease inhibitor, phenyl methyl sulphonyl fluoride, had little influence on the banding pattern. Concentrate in the diet appeared to increase inter-animal variation, and sheep in adjacent pens and consuming the same grass hay:concentrate diet had different banding patterns. Thus, no microbial proteolytic enzyme was predominant in protein digestion in the rumen.     

Gastrointestinal nematodes and dietary fibre: Two factors to consider when using FN for wildlife nutrition monitoring

Faecal nitrogen (FN) – the combination of metabolic nitrogen and residual food nitrogen – has been used as a proxy for diet quality in wild and domestic ruminants for over half a century. However, a common misconception in some of these studies is that FN is a direct proxy for dietary N, in spite of experimental evidence that links FN to general diet digestibility. Additionally, gastrointestinal nematodes (GIN) can alter N metabolism and increase FN by various mechanisms. To clarify the role of dietary N, fibre and GIN as a factor in FN excretion, 10 naturally parasitised sheep were fed two different isocaloric diets (LPF: low-protein, low-fibre; HPF: high-protein, high-fibre). One month after these diets began, a single anthelmintic treatment was applied to remove GIN, after which the sheep were kept on the same diet for an additional 2 weeks. Throughout the experiment, individual faecal samples were obtained to estimate both FN and GIN intensity (using faecal egg counts, FEC). In addition, two blood samples were taken before and after deworming to measure serum total protein concentrations (TP) as a proxy for protein absorption. In spite of the difference in dietary protein, FN was higher on an LPF diet, supporting the overall digestibility concept. The influence of GIN on FN was later revealed by the anthelmintic treatment, which led to a decrease of FEC and FN in both dietary groups. Serum total protein showed a slight but non-significant increase in both groups after the anthelmintic treatment. Our study supports not only the concept that FN is a proxy for diet digestibility, and not directly for dietary N, but also that gastrointestinal nematodes limit its use as a proxy for diet quality in ruminants, especially under high parasite loads (e.g., 1000 faecal eggs per gram of faeces). Such limitations should be considered before using FN for wildlife nutrition monitoring. Some recommendations are given to avoid misinterpretations.     

Determination of the optimum proportion of saccharides in the diet of adult rats

SPF male Wistar rats weighing 250-260 g and aged 90 days were fed 14 days on diets with a constant 10% protein (casein) content, a constant 11% fat (margarine) content and mounting saccharide (rice starch: sugar: potato starch - 6.4: 1.2: 1) contents of 31, 36, 41, 46, 51, 56, 61 and 66%. Protein intake and the body and liver nitrogen values were used to determine the utilization parameters of protein biological value, i.e. NPU (body) and LPU (liver), for the individual diets. Liver gluconeogenesis was also studied by measuring specific phosphoenolpyruvate carboxykinase (PEPCK) and fructose-1.6-diphosphatase (FDP-ase) activity. On the basis of linearity between the growth parameter NPR and protein and saccharide intake we determined the reciprocal relationship of the intake of the two nutrients and used it to compute the optimum saccharide concentration for the diet. The 51% saccharide diet gave the best protein utilization (the maximum (net) protein utilization value) in the 90-day-old rat organism. This was confirmed by the course of gluconeogenesis, which was significantly activated in the presence of 31-46% saccharide diets. By substituting the optimum protein intake in the reciprocal saccharide-protein intake relationship we obtained the optimum saccharide intake, which corresponded to a 49% concentration in the diet. With its use of a biological, biochemical and computation method, the study is a contribution to the determination of optimum nutrient values.