Estimation Of Digestibility Research Articles

The Metabolic Availability of Threonine in Common Feedstuffs Fed to Adult Sows Is Higher Than Published Ileal Digestibility Estimates ,

Amino acid (AA) requirements for sows during pregnancy are currently under review. However, requirement recommendations must be accompanied by an estimate of the bioavailability of AA from feeds to ensure adequate supply of AA and to minimize excess nitrogen excretion. Current ileal AA digestibility estimates are based on growing pig data; however, availability of AA in adult pigs may be different from that in growing pigs. The metabolic availability (MA) of threonine (Thr) in corn and barley was determined in 6 pregnant sows using the indicator AA oxidation method and L-[1-(13)C]phenylalanine as the tracer AA. Sows were fed reference diets formulated from 30 to 75% of the breakpoint derived in Expt. 1; all other nutrients were set at 120% of requirement. Test ingredients diets were formulated to supply Thr at 75% of the determined requirement. Tracer phenylalanine was given orally in 8 one-half-hourly meals and expired (13)CO(2) was quantified. The determined MA of Thr from corn and barley fed to pregnant sows was 88.0 and 89.3%, respectively. The determined MA was 7 and 9% greater than the published standard ileal digestibility estimates of Thr in corn (82%) and barley (81%), respectively. Mature animals have a greater capacity to digest and absorb nutrients from feed ingredients than previously assumed based on ileal digestibility studies. Sow diets formulated based on published ileal digestibility estimates are overformulated with respect to available protein and AA and thus increase excess nitrogen excretion and potential environmental concerns.

Do experimental methods affect estimates of pollen digestion by birds?

Pollen protoplasts may supply important nutritional resources for birds; however, they are locked up within the mechanically strong and biochemically complex pollen wall. Previous studies of pollen digestion in birds have yielded highly variable and often contradictory results. We tested whether these differences could reflect the vastly different methodologies that have been used. We used a standard method to investigate digestion of Banksia grandis (Proteaceae) pollen in New Holland honeyeaters (Phylidonyris novaehollandiae). Four types of B. grandis pollen were examined: fresh, frozen for a week, stored in conditions to stimulate pregermination for 24 h, or collected by honeybees. Our data indicate that although pollen treatment may influence digestibility of the pollen grains, these differences do not reach statistical significance because they are dwarfed by a high degree of variability between birds fed the same diet as well as variability in gut transit time (generally more pollen grains were digested over longer transit times). Similar patterns were observed for red wattlebirds (Anthochaera carunculata) fed bee-collected pollen. We believe that feeding behaviour or gut transit time may explain the marked differences between previous studies of pollen digestion by nectarivores, particularly the conflicting results for New Holland honeyeaters.

Improving the accuracy of digestibility estimates for cattle grazing tropical pastures when sampling with oesophageal fistulated cattle

The in vitro digestibility analysis of extrusa samples collected from oesophageal fistulated cattle is widely used to estimate the digestibility of diets selected by resident grazing cattle. In the present study, oesophageal fistulated steers were used to sample a range of grass–legume pastures continuously stocked with small herds of resident cattle at two sites in northern Queensland at different times of the year. Pepsin–cellulase in vitro analysis was used to measure in vitro dry matter loss (IVDML) during incubation. Additional laboratory analyses were used to demonstrate that unless appropriate corrections are applied, serious inaccuracies can occur in the estimates of in vivo digestibility as a result of (1) differences between IVDML of extrusa (feed plus saliva) and the IVDML of the feed consumed (feed without saliva), (2) differences in the botanical and chemical composition between the extrusa samples and the diets of the resident cattle, and (3) differences between grasses and legumes in the linear-regression relationships used to estimate in vivo digestibility from IVDML. Methodologies to minimise such errors are described and results illustrating the magnitude of potential errors are presented. In the dataset from the present study, it was clear that differences between extrusa and resident diets in grass–legume proportions consumed were the major cause of error but other causes of error were also important. Appropriate methodologies to improve accuracy are recommended.

Evaluation of Chemical Composition and In vitro Digestibility of Appennine Pasture Plants Using Yak (Bos grunniens) Rumen Fluid or Faecal Extract as Inoculum Source

Pastures of the Apennines of Central Italy contribute to feed resources of high altitude (above 1,300 m sea level) grazing systems. The objective of this study was to evaluate the effectiveness of faecal extract from the yak (Bos grunnienes) as an alternative microbial inoculum to rumen fluid for estimation of digestibility of several forage species. Forage samples produced at high altitude were tested in this study: four legumes (Lathyrus sativus L., Lotus corniculatus L., Onobrychis viciaefolia L. and Trifolium pratense L.), three forbs (Achillea millefolium L., Potentilla reptans L. and Teucrium flavum L.) and one grass (Brachipodyum pinnatum L.) were incubated with yak rumen fluid or faecal extract. A large variability in chemical composition was observed among the species collected. Rumen liquor and faecal samples were collected from adult healthy yak. The Daisy II incubator was used to evaluate the nutrient digestibility of forages using rumen liquor as control and faecal extract as alternative microbial inoculum sources. Filter bags containing samples of browse species were added to the four digestion vessels along with their respective inoculum and then incubated for 48 h and dry matter (DM), organic matter (OM), crude protein (CP), neutral and detergent fiber (NDF) digestibility was determined. There was a significant relationship between estimates, indicating that faecal liquor has the potential to be used instead of rumen fluid for estimation of in vitro digestibility of plants. It is concluded that the Daisy II incubator results are appropriate for the determination of

Comparison of in vitro digestibility estimates using the DaisyII incubator with in vivo digestibility estimates in horses1

The objective of this study was to determine if in vitro methodologies developed for the Ankom Daisy(II) incubator could produce accurate estimates of in vivo equine DM digestibility (DMD) and NDF digestibility (NDFD) when equine feces were used as the inoculum source. Four mature geldings were utilized in a 4 × 4 Latin square design experiment with a 2 × 2 factorial arrangement of dietary treatments (timothy hay, alfalfa hay, timothy hay plus oats, and alfalfa hay plus oats), in which the geldings were individually housed and fed. During each 5-d total fecal collection period, feces were collected and composited daily and used to calculate in vivo digestibility. Digestion of the 4 treatment diets was evaluated in vitro using the Daisy(II) incubator. Each incubation vessel of the Daisy(II) was assigned to 1 of the horses and contained 18 filter bags (6 containing the assigned treatment hay, 6 containing hay-oat mix, and 6 containing oats). Three incubation periods were evaluated: 30, 48, and 72 h. Although the 30- and 48-h in vitro estimates were consistently less than the in vivo estimates, they ranked diets in the same order as the in vivo method. For the alfalfa oat diet, timothy diet, and the timothy oat diet, the mean 72-h in vitro DMD and in vivo DMD were not different (P = 0.1444). However, for the alfalfa diet, the DMD estimate from 72-h in vitro incubation was less than the in vivo estimate (P < 0.010). For NDFD, the timothy diet was the only diet, in which the mean 72-h in vitro NDFD estimate was not different than the in vivo estimate. However, the in vitro method correctly ranked the alfalfa-based diets as having greater NDFD estimates than the timothy-based diets. Of the 3 incubation periods, the 72-h period provided digestibility estimates most similar to the in vivo data. Using the methodologies described in this research, the Daisy(II) incubator and equine feces can be used to estimate in vivo DMD of horse feeds.

A comparison of two methods to assess nutrient digestibility in pigs

The noninvasive estimation of nutrient digestibility (DIG) is usually done by total collection (TC) of feces in balance crates or by the indicator method (IM) using an indigestible marker such as chromic oxide (CO). TC is precise but involves much labor. These methods were compared using pigs fed corn–soybean meal diets. In Trial 1, 10 pigs (68.1 kg) were individually housed in metabolism crates for a 5-day (d) TC. The IM phase immediately followed by adding CO to the feed for 2 consecutive d, and collecting a single grab fecal sample. In Trial 2, 24 pigs (66.2 kg) were used and Cr was fed for 7 consecutive d with single samples collected for 5 d starting when the stool color appeared bright green (which usually occurred on d3 after Cr was fed). Samples were composited into 5 final samples (d1, d1 + 2, d1 + 2 + 3, d1 + 2 + 3 + 4, d1 + 2 + 3 + 4 + 5) labeled D1, D2, D3, D4, and D5, respectively. In Trial 1, DIG values of DM, energy, and N were 2–3 percentage points lower for IM vs TC; DIG of Ca and P was 10–20 percentage points lower for IM. Differences related to dietary treatments were observed for 4 of these nutrients with TC but none of the nutrients with IM. In Trial 2, DIG by IM increased from D1 through D5, coinciding with increasing Cr excretion. For the macronutrients evaluated, all reached their DIG plateaus by D5 and similar values were observed between TC and IM. Dietary treatment differences were observed for Ca and P by TC and were also detected by IM. It is concluded that a multiday sample works better than a single grab sample for IM and that several days of marker observance are required before the marker content stabilizes in feces.

Effects of inclustion and exposition times of sugar cane to calcium oxide on the physiologic and digestive parameters of Nellore heifers

It was aimed to evaluate the effect of inclusion and times of sugar cane exposition to whitewash on intake and total and partial digestibility of nutrients and ruminal parameters and to compare titanium dioxide and chromium oxide as markers to estimate fecal dry matter excretion and dry matter abomasal flow. It was used six rumen and abomasum cannulated Nellore females, with average body weight of 250 ± 19 kg, distributed in an incomplete 6 x 6 latin square design. The experiment was set in a 3 x 2 factorial scheme with three levels of whitewash (0; 0.5 or 1.0% natural matter) and two times of sugar cane storage (0 and 3 days). There was no effect of storage times neither interaction among levels of whitewash and storage times on the intake of nutrients. However, levels of whitewash linearly increased consumption of dry matter (DM), organic matter (OM) and non-fibrous carbohidrates (NFC).Storage times reduced total apparent digestibility of dry matter, organic matter and neutral detergent fiber corrected for ash and protein (NDFap), but they did influence ruminal apparent digestibility of the nutrients. The inclusion of whitewash increased the consumption of total digestible nutrients (TDN), but it did not affect total digestibility and ruminal digestibility of the nutrients. The markers produced similar results for the estimates of total and ruminal apparent digestibility of all the evaluated nutrients. Interactions for ruminal pH were observed. However, values of amonical nitrogen were only influenced by sampling times. Addition of whitewash does not affect preservation of sugarcane, but it positively influences consumption of DM, OM, and TDN of the animals. The markers produced similar estimative to total tract and ruminal apparent digestibility of all nutrients. Titanium dioxide and chromium oxide markers produce similar estimates of digestibility.

Digestibility and energy value of cereal-based diets in relation to digesta viscosity and retention time in turkeys and chickens at different ages estimated with different markers

Digesta viscosity, ileal transit time of digesta, apparent ileal protein digestibility and apparent metabolisable energy (AMEN) of diets based on wheat and dehulled barley (WB), oats (O) or a mixture of these (WBO) fed as such or with enzyme supplementation in three- and six-week old turkeys and broilers were investigated. In addition, differences between ileal digestibility and AMEN calculated by using titanium dioxide (TiO2), chromic oxide (Cr2O3) or acid insoluble ash (AIA) as indigestible markers were compared. Digesta viscosities were generally moderate reaching from 2.5 mPa · s to 7.3 mPa · s. The highest viscosities were observed in WBO diets. Viscosities were reduced with age in broilers, and were generally higher in turkeys than in broilers, especially at six weeks of age. Digesta retention time in ileum was elongated with age of the birds, pronouncedly in broilers. Oat inclusion to the diets decreased retention time especially in broilers at six weeks of age. Apparent ileal digestibility of protein ranged from 0.64–0.83, was lower at six weeks of age than at three weeks of age and generally lowest in O diets, especially in turkeys. AMEN of the diets ranged from 11.2–13.4 MJ/kg being higher at six weeks of age than at three weeks of age. AMEN of Diets O was the lowest but AMEN of WBO diets was higher than that of WB diets indicating a synergistic interaction of cereals, this trend being more pronounced in broilers. Enzyme supplementation decreased viscosity and improved AMEN in most diets, but did not affect ileal protein digestibility. Differences between ileal digestibility estimates obtained with TiO2 or Cr2O3 were small and mainly not significantly different from 0. AMEN estimates were generally higher when calculated with Cr2O3 than with TiO2. AIA gave remarkably lower AMEN values than TiO2 (the significant differences ranging from 0.24–0.94 MJ/kg). In addition, effects of markers on AMEN estimates interacted with age of the birds and dietary treatments.

Acurácia, precisão e robustez das estimativas da digestibilidade aparente da matéria seca determinada com o uso de indicadores em ovinos

O objetivo foi avaliar a acurácia, precisão e robustez das estimativas da digestibilidade aparente da matéria seca obtidas utilizando-se como indicadores fibra em detergente ácido indigestível (FDAi), fibra em detergente neutro (FDNi) indigestível, lignina em detergente ácido (LDA), LDA indigestível (LDAi) e óxido crômico em comparação ao método de coleta total de fezes. Dezoito ovinos (56,5 ± 4,6 kg PV) foram designados aleatoriamente a dietas compostas de 25, 50 ou 75% de concentrado e feno de Coast cross por 25 dias. As fezes foram coletadas por cinco dias para determinação da digestibilidade aparente da MS. As amostras de alimentos e fezes foram incubadas no rúmen de três bovinos por 144 horas, para obtenção das frações indigestíveis. Óxido crômico foi administrado a 4,0 g/animal/dia. A acurácia foi avaliada pela comparação do viés médio (DAMS predito - DAMS observado) entre os indicadores; a precisão, por meio da raiz quadrada do erro de predição e do erro residual; e a robustez, pelo estudo da regressão entre o viés e o consumo de matéria seca, o nível de concentrado e o peso vivo. A recuperação fecal e a acurácia das estimativas da digestibilidade aparente da MS foram maiores para FDAi, seguida pela FDNi, LDAi, pelo óxido crômico e depois pela lignina em detergente ácido. O viés linear foi significativo apenas para FDAi, FDNi e LDAi. O uso de óxido crômico permitiu estimativas mais precisas da digestibilidade aparente da MS. Todos os indicadores foram robustos quanto à variação no consumo de matéria seca e apenas LDAi e óxido crômico foram robustos quanto aos níveis de concentrado na dieta. O óxido crômico não foi robusto quando houve variação no peso vivo animal. Assim, a FDAi é o indicador mais recomendado na estimativa da digestibilidade aparente da MS em ovinos quando o objetivo é comparar aos dados da literatura, enquanto o óxido crômico é mais recomendado quando o objetivo é comparar tratamentos dentro de um mesmo experimento.

A study of the in vitro protein digestibility of indica and japonica cultivars

Protein digestibility was determined in 18 indica and japonica raw milled rices using an in vitro pH-drop method with three- or four-enzyme system. Similar protein digestibility was found between indica and japonica rices, which is in agreement with the in vivo digestibilities in human. Cooking improved protein digestibility in the four-enzyme assay, while reducing agents exhibited apparent inhibition in multienzyme digestibility of indica and japonica rices. A significant correlation was detected between protein content and the estimates of digestibility, whereas no significant correlation was found between amylose content and digestibility estimates. SDS–PAGE analysis showed a significant difference in the degradation extent of prolamin between multienzyme and pepsin digestion, which might contribute to the inconsistence between results of this study and previous findings that in vitro protein digestibility of japonica rice was higher than that of indica rice. In addition, our results supported the previous report that waxy gene product level is not a major determinant of protein digestibility in milled rice.

Relation between estimates of cornstarch digestibility by the Englyst in vitro method and glycemic response, subjective appetite, and short-term food intake in young men

Starch composition and rate of digestion are determinants of blood glucose concentrations and food intake (FI). Our objective was to describe relations between estimates of digestibility of starches by the in vitro Englyst method and their effect on blood glucose concentrations, subjective appetite, and FI in young men. Subjects consumed 5 soups containing 50 g maltodextrin, whole-grain, high-amylose, regular cornstarch, or no added starch at 1-wk intervals. Ad libitum FI was measured at 30 min (experiment 1) or 120 min (experiment 2) later, which were the estimated times of digestion of a rapidly digestible starch (RDS) and slowly digestible starch, respectively. Blood glucose concentrations and appetite were measured pre- and postmeal. At 30 min, FI was reduced by maltodextrin only [86% RDS, 12% resistant starch (RS); P < 0.05], but at 120 min FI was reduced by whole-grain (24% RDS, 66% RS), high-amylose corn (40% RDS, 48% RS), and regular corn (27% RDS, 39% RS) (P < 0.0001). The premeal blood glucose concentration at 30 and 120 min was highest and lowest after maltodextrin treatment, respectively (P < 0.0001). After the meal, the blood glucose area under the curve at 30 min was lower after all starch treatments (P < 0.05), but at 120 min the blood glucose area under the curve was lower only after the regular cornstarch treatment (P < 0.05). Premeal appetite decreased by all treatments (P < 0.05). The in vitro estimates of starch digestibility by the Englyst method predicted the effects of starch composition on blood glucose concentrations and FI in young men 30 and 120 min after consumption. This trial was registered at clinicaltrials.gov as NCT00980941 for experiment 1 and NCT00988689 for experiment 2.

Effect of milk replacer program on digestion of nutrients in dairy calves

There are concerns with feeding young dairy calves amounts of milk solids approaching 0.9kg of dry matter (DM) or more because of slumps in average daily gain (ADG) at weaning and low starter intakes. Additionally, programs feeding more than 0.6kg of DM have not been thoroughly tested for success at different weaning ages. Four milk replacer (MR) programs were compared in trial 1. Program A was 0.44kg of DM of a 21% crude protein (CP), 21% fat MR powder fed daily for 42 d. Program B was 0.66kg of DM of a 27% CP, 17% fat MR powder fed daily for 42 d. Program C was 0.66kg of DM of a 27% CP, 17% fat MR powder daily fed for 28 d. Program D was up to 1.09kg of DM of a 29% CP, 21% fat MR daily fed for 49 d. Digestibility estimates were made and blood was sampled for serum constituents on d 53 to 56, and performance was measured for 84 d. Three programs feeding a 27% CP, 17% fat MR powder were compared in trial 2 over 56 d. Calves on program A were fed 0.66kg of DM powder daily and weaned at 28 d. Calves on program B were fed 0.66kg of DM powder daily and weaned at 42 d. Calves on program C were fed up to 1.09kg of DM powder daily and weaned at 42 d. Digestibility estimates were made and blood was sampled for serum constituents d 21 to 24, d 36 to 39, and d 53 to 56. In trial 1, calves fed program A had the least overall ADG. Calves fed program D had the greatest ADG from 0 to 56 d, the least ADG from d 56 to 84, the least digestibility estimates, and the least concentrations of serum amylase. At 84 d, there were no differences in body weights of calves fed programs B, C, and D. In trial 2, calves fed program A had the greatest starter intake and greatest concentrations of serum amylase. Calves fed program C had the least estimates of digestibility from d 53 to 56 and the least serum concentrations of amylase. Calves fed up to 1.09 kg/d of 27 to 29% MR powders and weaned at 42 or 49 d had lower starter intakes, concentrations of serum amylase, and digestion of starter postweaning compared with calves fed conventional 21% CP, 21% fat MR powders fed at 0.44 kg/d. Calves fed 0.66 kg/d of a 27% CP, 17% fat MR powder and weaned at 28 or 42 d of age had no reductions in intake or digestion compared with calves fed conventional MR and gained as much total body weight from 0 to 84 d as calves stepped up to 1.09kg of MR.

Variability in in situ ruminal degradation parameters causes imprecision in estimated ruminal digestibility

The ruminal digestibility of dietary ingredients is frequently estimated with degradation parameters (e.g., rate and extent of degradation). Mean degradation parameters (e.g., those in a feed library) are often used, but limited data suggest considerable variation around these means, potentially leading to imprecise digestibility estimates. This experiment quantified degradation parameter variation for forage hays and determined the impact of this variation on the precision of ruminal digestibility estimates. Degradation data were those previously published by our laboratory and included degradation rate, λd (h−1), fraction instantly degraded, a (g·g−1), potential extent of degradation, (a + b) (g·g−1), and fraction not instantly degraded that is potentially degradable, b (g·g−1) of alfalfa, grass, and grass-legume hays. Ruminal digestibilities of chemical fractions (dry matter, neutral detergent fiber, acid detergent fiber, hemicellulose, crude protein) were estimated using these data. Ninety-five percent confidence limits of digestibility were determined using propagation of uncertainty with measured standard deviations of degradation parameters. Values for coefficients of variation of degradation parameters were large; averaged across chemical fractions, they were 24.8, 28.6, 20.7, and 12.6% for λd, a, b, and (a + b). Ninety-five percent confidence limits of digestibility were large (80.5% of digestibility means) and often overlapped each other, even when digestibility means differed greatly numerically. Consequently, digestibility values computed with mean degradation parameters may have little biological and practical significance. When uncertainty in all parameters but λd was set to zero (λd alone had uncertainty), 95% confidence limits still encompassed 54.5% of digestibility means. Thus, uncertainty in λd alone caused considerable imprecision in estimated digestibility. These results caution against using mean degradation parameters to estimate digestibility.

Estimation of rumen outflow in dairy cows fed grass silage-based diets by use of reticular sampling as an alternative to sampling from the omasal canal

A study was conducted to compare nutrient flows determined by a reticular sampling technique with those made by sampling digesta from the omasal canal. Six lactating dairy cows fitted with ruminal cannulas were used in a design with a 3 × 2 factorial arrangement of treatments and 4 periods. Treatments were 3 grass silages differing mainly in neutral detergent fiber (NDF) concentrations: 412, 530, or 639 g/kg of dry matter, each combined with 1 of 2 levels of concentrate feed. Digesta was collected from the reticulum and the omasal canal to represent a 24-h feeding cycle. Nutrient flow was calculated using the reconstitution system based on 3 markers (Co, Yb, and indigestible NDF) and using 15N as a microbial marker. Large and small particles and the fluid phase were recovered from digesta collected at both sampling sites. Bacterial samples from the reticulum and the omasum were separated into liquid- and particle-associated bacteria. Reticular samples were sieved through a 1-mm sieve before isolation of digesta phases and bacteria. Composition of the large particle phase differed mainly in fiber content of the digesta obtained from the 2 sampling sites. Sampling site did not affect marker concentration in any of the phases with which the markers were primarily associated. The 15N enrichment of bacterial samples did not differ between sampling sites. The reticular and omasal canal sampling techniques gave similar estimates of marker concentrations in reconstituted digesta, estimates of ruminal flow, and ruminal digestibility values for dry matter, organic matter, starch, and N. Sampling site × diet interactions were also not significant. Concentration of NDF was 2.2% higher in reconstituted omasal digesta than in reconstituted reticular digesta. Ruminal NDF digestibility was 2.7% higher when estimated by sampling the reticulum than by sampling the omasal canal. The higher estimate of ruminal NDF digestibility with the reticular sampling technique was due to differences in NDF concentration of reconstituted digesta. This study shows that nutrient and microbial protein outflow from the rumen can be measured using a reticular sampling technique. The reticular sampling technique provides a promising alternative to sampling from the omasal canal because there is less interference with the animal and it does not require advanced sampling equipment.

Consumo, digestibilidade e estimativa do valor energético de alguns volumosos por meio da composição química

Avaliou-se o consumo, a digestibilidade dos nutrientes e o teor de nutrientes digestíveis totais (NDT) da cana-deaçúcar e das silagens de capim-elefante, de milho e de sorgo em ovinos. Além disso, estimou-se o teor de NDT de acordo com o sistema de equações proposto pelo NRC (2001). Foram utilizados 20 ovinos, sem raça definida, machos, castrados, alojados em gaiolas de metabolismo, distribuídos em um delineamento inteiramente casualizado, sendo quatro tratamentos (volumosos) e cinco repetições (animais). A determinação da digestibilidade dos nutrientes foi realizada pela coleta total de fezes, com uso de sacolas coletoras. A comparação dos valores de NDT observados e estimados foi feita por meio do ajuste do modelo de regressão linear simples dos valores preditos sobre os valores observados. Os ovinos alimentados com as silagens consumiram maiores quantidades (P &lt; 0,05) de matéria seca (MS), proteína bruta (PB), extrato etéreo (EE) e fibra em detergente neutro (FDN) em relação aos alimentados com cana-de-açúcar. Não houve diferença (P &gt; 0,05) para o consumo de NDT entre as silagens. As digestibilidades aparentes da MS, MO, PB e EE não diferiram (P &gt; 0,05) entre os tratamentos. Constataram-se diferenças (P &lt; 0,05) entre os valores estimados e observados de NDT e das frações digestíveis da PB, da FDN e dos carboidratos não-fibrosos (CNF). As equações propostas pelo NRC (2001) mostraram-se inadequadas para estimar o valor energético dos volumosos para ovinos.

Review on endogenous nitrogen recycling in the rumen of ruminants

Study on protein requirement is the central research work in protein nutrition in ruminants and the exact measurement of endogenous nitrogen entering the rumen and efficiently utilized by microbial constitutes an important step for the estimation of true digestibility of dietary protein and protein requirements in ruminants. The objective of this article was to review studies on the sources of endogenous nitrogen, research methods of endogenous nitrogen recycling, endogenous urea nitrogen and total nitrogen entering the rumen of ruminants, and the proportion of nitrogen absorbed by microbe as reported in recent 30 years.

Fermentation kinetics and protein digestibility estimation of sheep diets containing different levels of Babaçu meal and cake in vitro

Fermentation kinetics and protein digestibility estimation of sheep diets containing different levels of Babaçu meal and cake in vitro

Standardized ileal amino acid digestibility in wheat distillers dried grains with solubles for broilers

A study was conducted to estimate the ileal digestibility of amino acids (AA) in 5 different samples of wheat distillers dried grains with solubles (DDGS) fed to broilers. Two hundred sixteen male Ross broiler chicks were fed a commercial starter diet from d 1 to 15 of age followed by the test diets from d 15 to 21. The 5 test diets consisted of a DDGS sample or wheat as the sole source of AA, dextrose, minerals, and vitamins. Chromic oxide (0.3%) was included in all diets as a digestibility marker. Each test diet was randomly assigned to 6 replicate cages, each with 6 birds. On d 21, birds were killed to sample ileal digesta for determining the apparent (AID) and standardized (SID) ileal AA digestibilities. The SID values were calculated using ileal endogenous AA losses previously determined in our laboratory. Among the indispensable AA in wheat DDGS, the lowest and highest AID average values were observed for Lys (35.6%) and Phe (79.2%), respectively. The most variable AID estimates of wheat DDGS samples were observed for Lys (24.4 to 45.7%), Thr (48.2 to 60.9%), and His (57.4 to 69.1%) as indispensable and Asp (32.5 to 50.9%), Gly (49.6 to 63.1%), and Ala (53.6 to 66.8%) as dispensable AA, respectively. Apparent ileal digestibility estimates of the wheat sample for Lys, Thr, His, Gly, and Ala were 77.5, 74, 83.6, 79.3, and 78.9%, respectively. All AA digestibility estimates for both AID and SID determined in wheat were higher than in wheat DDGS samples (P < 0.05). Considering both AID and SID coefficients of wheat DDGS samples, Lys was the least digestible AA, averaging 35.6 and 40.0%, respectively. Using SID values in practical diet formulation can increase accuracy, prevent overformulation of diets, and reduce cost of safety margins.

In vitro digestibility of individual amino acids in rumen-undegraded protein: The modified three-step procedure and the immobilized digestive enzyme assay

Three soybean meal, 3 SoyPlus (West Central Cooperative, Ralston, IA), 5 distillers dried grains with solubles, and 5 fish meal samples were used to evaluate the modified 3-step in vitro procedure (TSP) and the in vitro immobilized digestive enzyme assay (IDEA; Novus International Inc., St. Louis, MO) for estimating digestibility of AA in rumen-undegraded protein (RUP-AA). In a previous experiment, each sample was ruminally incubated in situ for 16h, and in vivo digestibility of AA in the intact samples and in the rumen-undegraded residues (RUR) was obtained for all samples using the precision-fed cecectomized rooster assay. For the modified TSP, 5g of RUR was weighed into polyester bags, which were then heat-sealed and placed into DaisyII incubator bottles. Samples were incubated in a pepsin/HCl solution followed by incubation in a pancreatin solution. After this incubation, residues remaining in the bags were analyzed for AA, and digestibility of RUP-AA was calculated based on disappearance from the bags. In vitro RUP-AA digestibility estimates obtained with this procedure were highly correlated to in vivo estimates. Corresponding intact feeds were also analyzed via the pepsin/pancreatin steps of the modified TSP. In vitro estimates of AA digestibility of the feeds were highly correlated to in vivo RUP-AA digestibility, which suggests that the feeds may not need to be ruminally incubated before determining RUP-AA digestibility in vitro. The RUR were also analyzed via the IDEA kits. The IDEA values of the RUR were good predictors of RUP-AA digestibility in soybean meal, SoyPlus, and distillers dried grains with solubles, but the IDEA values were not as good predictors of RUP-AA digestibility in fish meal. However, the IDEA values of intact feed samples were also determined and were highly correlated to in vivo RUP-AA digestibility for all feed types, suggesting that the IDEA value of intact feeds may be a better predictor of RUP-AA digestibility than the IDEA value of the RUR. In conclusion, the modified TSP and IDEA kits are good approaches for estimating RUP-AA digestibility in soybean meal products, distillers dried grains with solubles, and fish meal samples.

Methods for predicting the energy value of pet foods

The energy value of foods as well as energy requirements of dogs and cats is currently expressed in terms of metabolizable energy (ME). The determination of ME content of foods requires experimental animals and is too expensive and time consuming to be used routinely. Consequently, different indirect methods have been proposed in order to estimate as reliably an accurately as possible the ME content of pet food. This work analyses the main approaches proposed to date to estimate the ME content of foods for cats and dogs. The former method proposed by the NRC estimates the ME content of pet foods from proximal chemical analysis using the modified Atwater factors, assuming constant apparent digestibility coefficients for each analytical fraction. Modified Atwater factors systematically underestimate the ME content of low-fibre foods whereas they overestimate those that are high in fibre. Recently, different equations have been proposed for dogs and cats based in the estimation of apparent digestibility of energy by the crude fibre content, which improve the accuracy of prediction. In any case, whatever the method of analysis used, differences in energy digestibility related with food processing and fibre digestibility are unlikely to be accounted for. A simple in vitro enzymatic method has been recently proposed based in the close relationship that exist between energy digestibility and organic matter disappearance after two consecutive enzymatic (pepsin-pancreatin) incubation of food sample. Nutrient composition and energy value of pet foods can be also accurately and simultaneously predicted using near infrared reflectance spectroscopy (NIRS).