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RESUMO -Avaliou-se o uso de matéria seca indigestível (MSi) e de fibra detergente neutro indigestível (FDNi) como indicadores internos de digestibilidade em ovinos. Utilizaram-se dados e amostras provenientes de seis ensaios independentes de digestibilidade com ovinos mantidos em gaiolas de metabolismo recebendo à vontade diversos tipos de volumoso e/ou concentrado. Os resíduos indigestíveis (MSi e FDNi) foram determinados após 144 horas de incubação in situ de amostras de alimentos e fezes. O grau de recuperação da MSi variou de 64,8 a 108,5% e o da FDNi, de 49,5 a 67,9%. Quando a relação entre a concentração dos indicadores nas fezes e nos alimentos não foi corrigida para a recuperação fecal, a maior parte das estimativas médias de digestibilidade da matéria orgânica dos experimentos foi inferior às médias obtidas in vivo. Quando a relação foi corrigida para a recuperação fecal, as estimativas médias de digestibilidade da matéria orgânica usando os dois indicadores foram similares às obtidas in vivo em todos os experimentos. Quando as estimativas individuais, corrigidas para recuperação fecal do indicador, foram relacionadas às observações in vivo por análise de regressão, o coeficiente de regressão linear foi similar a 1 usando a MSi, mas foi menor que 1 usando a FDNi. Os valores individuais de digestibilidade da matéria orgânica estimados com os dois indicadores, contudo, foram pobremente relacionados às observações in vivo (r 2 variou de 0,60 a 0,63). Corrigindo-se para a recuperação fecal, a matéria seca residual após 144 horas de incubação in situ pode ser utilizada como indicador interno para estimar a digestibilidade média da dieta consumida por um grupo de animais, mas não é precisa para detectar pequenas diferenças na digestibilidade de alimentos impostas pelos tratamentos em um experimento.Palavras-chave: consumo, digestibilidade, fibra em detergente neutro indigestível, matéria seca indigestível, recuperação fecal Evaluation of indigestible feed fractions as internal markers for predicting digestibility in lambsABSTRACT -The use of indigestible dry matter (iDM) and indigestible neutral detergent fiber (iNDF) as internal markers to estimate digestibility in lambs was evaluated. Data and samples were obtained from six independent digestion trials with lambs housed in metabolism cages given ad libitum different forage and concentrate feedstuffs. Indigestible residues were determined after 144 hours of in situ incubation of feed and faeces samples. Recovery rate varied from 64.8 to 108.5% for iDM, and from 49.5 to 67.9% for iNDF. As the marker ratio between marker concentration in the faeces and the feed was not corrected for fecal recovery, the large part of the estimated apparent organic matter digestibility (AOMD) of the experimental means were lower than the in vivo that obtained. As the marker ratio was corrected for fecal recovery of the marker, the AOMD means estimated using both markers were similar to the in vivo data in all experiments. As individual estimates, corrected for fecal recovery of ...

The study assessed the effect of Acacia mearnsii tannin extract supplementation grazing dairy cows on dry matter (DM) intake, enteric methane (CH) emission, and performance. Twelve Holstein cows were divided into two groups and subjected to two treatments that consisted of millet pasture (Pennisetum glaucum L.) plus supplementation with 6 kg of concentrate (750-g/kg ground corn and 250-g/kg soybean meal) including or excluding 120-g tannin extract. The trial design was a double reversal using three periods of 28 days each, with 21 days for the adaption period, and 7 days for sample collection. Herbage intake was measured using the n-alkane technique, and daily CH emission was measured with the sulfur hexafluoride tracer gas technique. Individual total DM intake (mean = 17.1 kg/day), herbage DM intake (mean = 11.8 kg/day), and milk production (mean = 19.2 kg/day) were similar between treatments. CH emission significantly decreased (32%, P < 0.05) in the animals supplemented with tannin extract, compared to non-supplemented animals. On the other hand, as proportion of DM intake or milk production, methane emission tended to decrease in tannin-supplemented animals. Supplementing dairy cows grazing a millet pasture with 120-g tannin extract reduced daily CH emission without affecting animal performance.

Energy supplementation can increase the consumption of metabolizable energy and substrate for microbial growth, while condensed tannins aid in increasing the duodenal flow of metabolizable proteins. The objective of this study was to evaluate the effects of energy supplementation and the inclusion of tannin extract (TE) from Acacia mearnsii (Weibull Black, Tanac S. A., Montenegro, Brazil) on the production performance of dairy cows grazing on winter pastures. Nine multiparous Holstein cows in mid lactation were distributed in a 3 × 3 Latin square experimental design over three periods of 28 days (21 adaptation and 7 sampling). The treatments were: without supplementation (WS), supplementation with 4 kg of corn grain (CG), and corn grain + 80 g of tannin extract (TE). The dry matter (DM) intake from pastures was similar among treatments, but the consumption of DM of the supplement was higher in the CG treatment than that in the TE treatment. The total DM intake was higher for the supplemented animals (17.3 kg·day -1 ) than that for the unsupplemented animals (14.9 kg·day -1 ) and in the TE treatment (17.7 kg·day -1 ) than in the CG treatment (16.7 kg day -1 ). Milk production increased from the unsupplemented to the supplemented animals (20.9 to 23.5 kg, respectively), while the content of urea N in the milk decreased (12.6 to 10.5 mg·100 mL -1 , respectively). There were no differences in milk production or content of milk urea N between the CG and TE treatments. Energy supplementation is a tool for improving the nutritional profile and the performance of dairy cows in mid lactation grazing on annual winter pastures, while tannin extract aids in improving the energy balance.

SUM M ARYTen Polwarth × Texel lambs (26 ± 2·1 kg live weight (LW)), housed in metabolism cages and offered ryegrass (Lolium multiflorum) ad libitum, were used in a 5 × 5 Latin Square experiment to evaluate the effect of supplement type on digestion processes and on amino acid and energy supplies. Five of the 10 lambs were fitted with a rumen catheter and duodenal cannulae. Treatments included no supplement (control); 7 g/kg LW daily of cassava meal (Manihot esculenta, high-starch low-nitrogen (HS-LN)), cassava meal plus corn gluten meal (2:1, high-starch high-undegradable N (HS-UN)), cassava meal plus calcium caseinate (2·8:1, high-starch high-degradable N (HS-DN)) or corn gluten feed (low-starch high-degradable N (LS-DN)). Total intake of dry matter (DM), organic matter (OM) and N, as well as digestible OM intake were increased with HS-UN, HS-DN and LS-DN (P 4 0·050). Forage DM intake was reduced by HS-LN (P = 0·030). Apparent digestibility of DM and OM was increased by HS-LN and HS-DN (P 4 0·038). Digestibility of neutral detergent fibre (NDF) and OM true digestibility were similar for all treatments. Supplementation with HS-LN decreased duodenal flux of total N, amino acid N, ammonia N and feed residual N (P 4 0·023). None of the supplements affected rumen microbial protein entering the small intestine, whereas the efficiency of rumen microbial protein synthesis (EMPS) was reduced by HS-LN and HS-DN (P 4 0·036). Ruminal degradability of dietary N (RDN) was increased by HS-LN, HS-DN and LS-DN (P 4 0·050). In conclusion, supplementing lambs fed ryegrass with degradable or undegradable high-protein concentrate increased the amino acid supply without affecting the supply of digestible energy, regardless of either the starch content or the degree of ruminal degradability of the protein source. These results indicate that supplementation of ryegrass-based diets should include both starch and protein sources.

The amount of digesta flowing to the duodenum is a relevant measurement for the evaluation of nutrient supply to ruminants, which is usually estimated in animals fitted with a duodenal T-type cannula using internal or external markers. This study evaluated acid detergent fiber (ADF) compared with external (C32n-alkane) and internal [sulfuric acid lignin (ADL) and n-alkanes C31 and C33] markers for estimating duodenal flow and(or) ruminal digestibility of dry matter (DM) in cattle and sheep. In the first assay, 4 duodenally cannulated Holstein steers housed in metabolism cages, dosed with C32n-alkane, and fed Avena strigosa plus concentrate and increasing levels of tannin extract to reduce ruminal digestibility, were used in a Latin square design. The mobile-bag technique was used to measure the intestinal disappearance of ADL and ADF from forage (Avena strigosa, Pennisetum purpureum, Cynodon dactylon, and Medicago sativa) and concentrate (corn grain, soybean meal, and sunflower meal) samples that were previously incubated in the rumen of additional fistulated steer for 12, 24, 36, or 48 h. The ADF concentration in residues recovered in the feces was strongly related to the ADF concentration in residues at the duodenum (R(2)=0.93, standard deviation=30.0, n=901). This relationship showed a lower precision for ADL fraction (R(2)=0.88, standard deviation=12.6, n=590). In a second assay, duodenal flow and ruminal DM digestibility were calculated from the duodenal and fecal concentration of either marker. We observed a significant effect of marker type on ruminal DM digestibility values, and the effect of tannin treatments was observed only when ADF or ADL was used as the marker. The lowest residual error was obtained for ADF. Ruminal DM digestibility was, on average, higher for C31 and C(33)n-alkanes, and the use of dosed C(32)n-alkane resulted in a negative value. In the third assay, a data set of 235 individual observations was compiled from digestibility trials to compare ADF and ADL as markers for estimating duodenal digesta flow in wethers (n=204) and cattle (n=31). We observed a strong relationship between markers (R(2)=0.84 in sheep and R(2)=0.88 in cattle), but variance analysis within trials indicated that ADF was more precise than ADL. In conclusion, in digestibility trials in which fecal output was measured and spot samples of the duodenal digesta were obtained, duodenal flow and ruminal digestibility of the DM may be estimated from the relationship between the ADF concentration in feces and that in the duodenal digesta of ruminants.

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