C. Castrillo

Urinary excretion of allantoin and allantoin precursors by sheep after different rates of purine infusion into the duodenum

Two experiments were carried out to determine endogenous losses and the response of urinary purine derivatives to increased duodenal inputs of purine bases. Four ewes each fitted with a re-entrant cannula at the proximal duodenum, and conventionally fed, were subjected to full replacement of duodenal digesta followed by the administration of a solution either free of purines (Expt 1) or enriched with increasing amounts of purines, to supply 0·48–21·27 mmol/animal per day (Expt 2). Basal daily urinary excretions of allantoin, uric acid, hypoxanthine and xanthine were 11·5 ± 0·94, 9·9 ± 0·67, 6·9 ± 0·46 and 1·2 ±0·16 mg/kg W 0·75 . Allantoin was the only purine derivative which increased in response to incremental inputs of duodenal purines. The relationship between allantoin excretion and infused purines showed a urinary recovery of 0·8 for purines infused at > 220 μmol/kg W0·76. Lower rates of infusion did not alter allantoin excretion. The results show urinary allantoin to be a useful index to estimate duodenal input of purines when animals are fed close to or above their energy maintenance requirements.

Quantification and chemical composition of mixed bacteria harvested from solid fractions of rumen digesta: effect of detachment procedure

Four ewes were given two diets made up with two ratios of rolled barley grain and ammonia treated straw (80/20, diet C and 20/80 diet R) twice a day. Two microbial markers, purine bases (PB) and 15N, were used as internal and external markers, respectively. Ruminal bacteria from the liquid (LAB) and solid (SAB) fractions of digesta were harvested from samples obtained at 1 and 6 h after feeding. Bacteria were separated from the particulate material by cooling plus homogenisation (B) and also by applying tertiary butanol (TB), methylcellulose (M) or changes of temperature (CHT). The most effective procedures to remove bacteria from the solid phase were M and CHT although CHT showed the highest level of losses and the lowest total recovery of the bacterial pellet. There were no differences between B and TB in both detaching efficiency and total recovery ratio of adherent bacteria. Ratio of recovery of detached material as a bacterial pellet was 32.0, 32.2, 33.3 and 27.8% for B, TB, M and CHT, respectively. Diet did not interact with detaching efficiency of the experimental treatment although concentration of total N (g/100 g OM) and PB (μmol/g OM) content concentration were higher in pellets obtained with diet C (9.11 and 125) than with R (8.20 and 107, respectively, P<0.05). Postprandial differences were not significant. Bacterial samples extracted from the liquid phase contained significantly (P<0.001) more total N (9.21 vs. 8.51) PB (160.5 vs. 104.3) and PB/N (1.73 vs. 1.23 μmol/mg) than those samples extracted from the solid phase. There were no differences in the chemical composition of the microbial sample after detachment by B, BT and M but bacterial extract obtained after CHT treatment showed significant changes in PB, N content and PB/N ratio (P<0.01).

By-products from the canning industry as feedstuff for ruminants: Digestibility and its prediction from chemical composition and laboratory bioassays

Abstract Fresh artichoke by-product, pepper and cauliflower residues, dried tomato pulp and fresh or ensiled apple pomace were fed, together with alfalfa hay, to adult ewes in four diets including 20, 40, 60 and 80% of each by-product, and organic matter digestibility (OMD) was estimated by the regression and difference methods. The OMD of ensiled artichoke and pea haulms was also determined directly giving both by-products as a whole diet. The OMD varied linearly with the dietary level of inclusion of each by-product, except for diets including pepper residues, where digestibility was similar tothat of the alfalfa hay. The digestible organic matter (DOM) content (g kg −1 DM) of fresh artichoke, pea haulms, apple pomace, pepper and cauliflower residues and dried tomato pulp was estimated to be 750, 650, 847, 615, 679 and 449, respectively, and that of ensiled artichoke, pea haulms and apple pomace 669, 508 and 739, respectively. Dry matter disappearances after in vitro incubation with rumen liquor-pepsin or pepsin-cellulase solutions and after 24 as well as 48 h of in situ incubation were determined to study their usefulness as predictors of OMD compared with several chemical parameters. The most accurate predictions were obtained with the in situ method after 48 h of incubation ( r = 0.97; RSD = ± 3.03) followed by the rumen liquor-pepsin procedure ( r = 0.94; RSD = ± 4.62) and pepsin-cellulase bioassay ( r = 0.88; RSD = ± 6.09). Chemical parameters proved to be poor predictors of OMD for this sort of by-product (RSD ranged from ± 7.00 to ± 11.96).

Study of the effect of presence or absence of protozoa on rumen fermentation and microbial protein contribution to the chyme.

The aim of this study was to investigate the effect of presence or absence of protozoa on rumen fermentation and efficiency of microbial protein synthesis under different diets. Of 20 twin paired lambs, 1 lamb of each pair was isolated from the ewe within 24 h after birth and reared in a protozoa-free environment (n = 10), whereas their respective twin-siblings remained with the ewe (faunated, n = 10). When lambs reached 6 mo of age, 5 animals of each group were randomly allocated to 1 of 2 experimental diets consisting of either alfalfa hay as the sole diet, or 50:50 mixed with ground barley grain according to a 2 × 2 factorial arrangement of treatments. After 15 d of adaptation to the diet, the animals were euthanized and total rumen and abomasal contents were sampled to estimate rumen microbial synthesis using C(31) alkane as flow marker. Different ((15)N and purine bases) and a novel (recombinant DNA sequences) microbial markers, combined with several microbial reference extracts (rumen protozoa, liquid and solid associated bacteria) were evaluated. Absence of rumen protozoa modified the rumen fermentation pattern and decreased total tract OM and NDF digestibility in 2.0 and 5.1 percentage points, respectively. The effect of defaunation on microbial N flow was weak, however, and was dependent on the microbial marker and microbial reference extract considered. Faunated lambs fed with mixed diet showed the greatest rumen protozoal concentration and the least efficient microbial protein synthesis (29% less than the other treatments), whereas protozoa-free lambs fed with mixed diet presented the smallest ammonia concentration and 34% greater efficiency of N utilization than the other treatments. Although (15)N gave the most precise estimates of microbial synthesis, the use of recombinant DNA sequences represents an alternative that allows separate quantification of the bacteria and protozoa contributions. This marker showed that presence of protozoa decrease the bacterial-N flow through the abomasum by 33%, whereas the protozoa-N contribution to the microbial N flow increased from 1.9 to 14.1% when barley grain was added to the alfalfa hay. Absolute data related to intestinal flow must be treated with caution because the limitations of the sampling and maker system employed.

Tomato pomace as a protein supplement for growing lambs

Abstract A barley-based diet (B) with 115 g CP/kg DM was supplemented, on DM basis, with 100 (T1), 200 (T2) or 300 (T3) g tomato pomace/kg to achieve final CP contents of 136, 156 and 172 g/kg DM, respectively, and fed to four growing lambs each. DM intake was adjusted to achieve the same energy intake for all diets (50 g DOM/kg BW0.75). N retention increased from 0.50 to 0.69 g/kg BW0.75 between diets B and T1, but higher levels of supplementation did not improve N retention. In a second balance trial, a barley-based diet (B) with 122 g CP/kg DM was supplemented, per kg ration DM, with 200 g tomato pomace untreated (TU) or treated with 50 g NaOH/kg DM (TT). The supplemented diets, containing 155 and 151 g CP/kg DM, respectively, were compared to an isonitrogenous soybean meal diet (SL; 145 g CP/kg DM), and a higher protein soybean meal diet (SH; 163 g CP/kg DM). All diets were fed ad libitum to four lambs per treatment. There were no differences in DM or DOM intake, mean values being 99.1 ± 1.66 and 65.3 ± 1.24 g/kg BW0.75, respectively. N retention (g/kg BW0.75) increased significantly from 0.84 on diet B to 1.07 on diets TU, TT and SL, but diet SH did not promote a significantly higher N retention. In a growth trial, diets TU, TT, SL and SH were fed to seven lambs each for an experimental period of 6 wk. Mean live weight increased from 15.5 ± 0.56 to 28.2 ± 0.44 kg final weight. DM intake (g/kg BW0.75) was not affected by dietary treatment and was 95.4, 97.1, 102.3 and 97.0 for TU, TT, SL and SH, respectively. Growth rates ( g d ) and feed conversion rates (kg DM/kg gain) were 304, 318, 337, 329 and 3.20, 2.95, 3.10 and 2.95 for the same diets. It was concluded that supplementation of barley-based diets with tomato pomace at a rate of 200 g/kg ration DM promote similar N retentions and growth performances to soybean protein in young lambs up to 28 kg BW.

Influence of dietary rumen-degradable protein supply on rumen characteristics and carbohydrate fermentation in beef cattle offered high-grain diets.

Four crossbred Holstein‐Friesian heifers (initial live weight 306 6:1 kg) fitted with rumen and duodenal cannulae were randomly allocated to one of two dietary treatments in a double 2 2 crossover design. Both diets were composed of (g/kg as fed) 250 barley straw and 750 concentrate. The concentrate consisted of (g/kg as fed) 655 corn and 225 barley (Diet C) and 225 corn and 655 barley (Diet B), respectively. During Period 1, two heifers were given Diet C and the other two heifers were given Diet B and all four heifers were infused intraruminally, during four sequential 16-day intervals, with four levels of effective rumen degradable protein (ERDP). ERDP was given as an iso-nitrogenous mixture of urea and casein at 0, 25, 50 or 75 g/kg of concentrate intake. Animals offered Diet B ate more DM, OM and NDF than those offered Diet C (97.6, 89.9 and 37.6 g/kg versus 94.4, 87.3 and 31.9 g/kg metabolic live weight (W 0.75 ), respectively (P < 0:05). Starch digestion did not differ significantly between diets, but fibre was better digested in Diet C than in Diet B, i.e. 56.5% versus 47.5%, 51.3% versus 36.4% and 50.5% versus 40.2% for arabinose, xylose and cellulose‐glucose digestibilities, respectively (P < 0:05). Mean rumen ammonia concentrations increased linearly from 29.1 mg/l when no ERDP was infused to 184.5 mg/l when ERDP was infused at the highest level. Ruminal pH was lower (P < 0:05) in animals offered Diet B than those offered Diet C (6.29 versus 6.46) and in ERDP-supplemented rather than unsupplemented diets (6.73 versus 6.28). However, pH never fell below 5.5. There were no differences in effective rumen degradability between Diets B and C, and increasing the ERDP supply promoted an increase in straw (P < 0:05) and corn (P < 0:1) DM disappearance from polyester bags. The diets without ERDP infusion were apparently deficient in degradable N because rumen microbial yield increased from 76.0 to 102.5 g N/d (P < 0:05) when ERDP infusion rate was increased from 0 to 25 g/kg of concentrate, irrespective of which type of grain concentrate was used. With further increases in ERDP, microbial yield maintained constant and there was no further

Effect of ammonia treatment and carbohydrate supplementation on the intake and digestibility of barley straw diets by sheep

Abstract The changes in straw voluntary intake and apparent digestibility caused by the ammoniation of straw and energy supplementation in diets fed to adult, non-productive sheep were studied in two experiments. In Experiment 1, untreated (US) or ammonia treated (TS) barley straw were given as the only feed to four ewes in a cross-over design. Ammoniation increased straw dry matter (DM) intake from 30.2 to 50.6 g kg −1 LW 0.75 , organic matter digestibility (OMD) from 0.438 to 0.519 and digestible organic matter intake (DOMI) from 12.5 to 24.7 g kg −1 LW 0.75 , allowing energy maintenance requirements to be met. In Experiment 2, three groups of four ewes received US, with another three groups of four receiving TS, both supplemented with meadow grass hay (H), rolled barley (B) or sugar-beet pulp (P) in a 2 × 3 factorial design. Each supplement was given in amounts of 150, 300, 450 and 600 g day −1 , in a Latin-square design. The type of supplement did not significantly affect straw intake at any level of inclusion. The level of supplementation scarcely affected US intake, whereas DM intake of TS diminished linearly. Substitution rates were 0.49 ± 0.088, 0.61 ± 0.085 and 0.55 ± 0.131 for TS-H, TS-B and TS-P diets, respectively ( P > 0.05). Apparent digestibility of straw was not significantly affected by supplementation. Increases in total DOMI when the level of supplementation was augmented were lower in TS than in US diets, and with H than with B or P as supplements. To reach the DOMI obtained with TS as the only feed, US has to be supplemented with 420, 272 or 269 g DM of H, B or P, respectively.

Effect of ammonia treatment and carbohydrate supplementation of barley straw on rumen liquid characteristics and substrate degradation by sheep

Abstract The effect of ammonia treatment and supplementation of barley straw with increasing levels (0, 200, 400 and 600 g day −1 ) of meadow grass hay (H), rolled barley (B) or pelleted sugar-beet pulp (P) on ruminal characteristics and straw degradation was studied using eight adult ewes, divided in two groups, receiving either untreated (US) or ammonia treated (TS) straw, supplemented with H, B or P consecutively. Urea (30 g kg −1 straw) was added to US 24 h before feeding. Sheep fed US showed higher ammonia-N (NH 3 N) concentration than those fed TS, either as the only feed (17.5 and 12.3 mg per 100 ml) or supplemented (15.0 and 12.7 mg per 100 ml). There was no effect of ammoniation over rumen pH or total volatile fatty acid (VFA) concentration. Supplementation with B or P depressed pH and enhanced VFA concentration, whereas H did not have any great effect. Extent of straw rumen degradation was enhanced by ammoniation (maximum degradation of 593 and 741 g kg −1 for US and TS), but rate of degradation and lag time remained unaffected. Both rate and extent of straw degradation were decreased to a similar extent when supplemented with B or P, while with H this effect was only noticeable when it was included in the diet at 600 g day −1 .

Validation of use of purine bases as a microbial marker by 15 N labelling in growing lambs given high-concentrate diets: effects of grain processing, animal age and digesta sampling site

The origin of post-ruminal purine bases ( PB) was studied in 24 growing lambs that were given a pelleted concentrate plus barley straw (C) or whole barley grain plus protein supplement ( WB). Six lambs from each treatment were slaughtered at 10 and 30 days post weaning after 15 N labelling of microbial nitrogen (N) and PB. Microbial contribution to digesta nonammonia N (NAN) and PB was lower ( P < 0·01) when estimated from duodenal rather than abomasal samples (0·36 v. 0·52 (s.e.d. 0·021) for NAN and 0·47 v. 0·77 (s.e.d. 0·029) for PB) as a result of endogenous contamination. In comparison with 15 N, total PB/N led to higher estimates ( P < 0·01) of microbial contribution to abomasal NAN in WB treatment (0·62 v. 0·46 s.e.d. 0·049). The difference was removed after correcting for microbial PB, while this effect was not observed with < the C diet, resulting in a marker by diet interaction ( P < 0·05). Abomasal PB flow increased ( P < 0·1) from 10 to 30 days after weaning mainly due to the higher proportion of microbial PB (0·70 v. 0·81 (s.e.d. 0·047)). Rumen apparent PB degradation did not differ between diets in older lambs, but it was proportionally 0·39 lower for WB treatment ( P < 0·05) in younger lambs. When the microbial PB flow was estimated indirectly from labelled microbial N and the PB/N ratio of bacterial extracts the estimates were in agreement with those derived from PB- 15 N in the WB treatment but resulted in unrealistic values in lambs on diet C. Results suggest that significant proportions of dietary PB can escape rumen degradation which may lead to overestimation of microbial contribution to abomasal NAN when the PB/N ratio is used as marker. The extent of the overestimation is affected by the lamb age and grain processing.

Gas production from straw incubated in vitro with different levels of purified carbohydrates

The effect of the type (starch (S); cellulose (C) and pectin (P)) and level (0–4 mg/ml) of added carbohydrate on gas production from ammoniated straw (AS) at a fixed pH (6.7) was studied in vitro in three incubation runs. The S, C and P were also incubated without AS at levels of 1, 2.5 and 4 mg/ml. On a dry weight basis, gas produced from P as the only substrate was higher than S, and from S higher than C up to 12 h of fermentation (P<0.05). From 24 to 36 h, gas volume from S was higher than P, with no differences after 48 h. Gas produced from AS in mixed incubations was estimated by subtraction of the carbohydrate contribution, calculated by linear regression. Gas volume from AS was higher with P than with S or C at all times (P<0.05). Proportion of acetate was higher, and propionate lower, in P than in S or C media (P<0.05). Addition of C or S reduced gas volume from AS compared with level 0 from 24 or 30 h onwards, respectively (P<0.05). However, inclusion of P increased linearly gas production until 8 h (P<0.01). In vitro, carbohydrates affected straw fermentation at an optimum pH, being negative with starch and cellulose from 24 h onwards. A positive effect of pectin on straw fermentation was observed in the first 8 h of incubation, and no effect was seen thereafter.