Estimation Of Digestibility Research Articles

PSI-35 Comparison of in situ techniques to evaluate the recovery of indigestible components and the accuracy of digestibility estimates

Abstract Our objective was to evaluate the effects of bag type (BT) and incubation length (IL) when using in situ incubations for determination of indigestible components. Indigestible components play an integral role as an internal marker for rumen kinetics and digestibility estimations, as well as providing parameter estimates for nutritional models. However, the accuracy of internal markers is dependent upon the incubation technique utilized, with BT and IL acting as sources of error. A 3 × 2 factorial design was used to investigate the effect of BT (F57, F58, and Dracon) and IL (288 and 576 h) on indigestible dry matter (iDM) and neutral detergent fiber (iNDF) residues, as well as estimated DM and NDF digestibilities. Feed and fecal samples were obtained from two animals from an independent trial that collected total fecal production over 4 days. All bags contained a sample size-to-surface area ratio of 20 mg/cm2 and were ruminally incubated within three rumen-cannulated steers (229.5 ± 10 kg). For iDM and iNDF, feed residues demonstrated a BT × IL interaction (P < 0.01). Fecal residues for iDM and iNDF had BT and IL effects (P < 0.01) with the Dracon BT and 576 h IL having the least residues. Digestibility estimates for DM and NDF were influenced by BT × IL (P < 0.01) with the accuracy of estimates demonstrating a BT × IL interaction (P < 0.01) in which F57 at 576 h had the greatest accuracy. Resultant fecal recovery estimates for DM and NDF excreted exhibited a BT × IL interaction (P < 0.01), with F57 at 576 h better representing the excretion profiles. Based upon our analysis, utilizing the F57 BT at 576 h IL combination provides more accurate estimates relative to all other combinations used within the current study.

PSIX-29 Effect of quebracho (Schinopsis balansae) extract inclusion in a high roughage diet upon in situ digestion

Abstract The objective was to determine the effect of quebracho tannin extract (QT; Schinopsis balansae) within a roughage-based diet upon dry matter and neutral detergent fiber digestibility (DMD and NDFD, respectively). The use of natural plant secondary compounds as a feed additive in animal nutrition has been studied due to their ability to modify digestive and metabolic functions in both ruminants and non-ruminants. Condensed tannin (CT) supplementation has demonstrated potential to mitigate CH4 emissions, but this commonly corresponds with reduced ruminal fiber degradation. However, prolonged supplementation of CT in a roughage-based diet is limited within the literature. Twenty rumen cannulated animals (227 ± 19 kg) were randomly assigned to four dietary treatments (n = 4): QT at 0, 1, 2, and 3% of DM (QT0, QT1, QT2, and QT3). A maintenance-fed diet containing 88% bermudagrass hay and 12% concentrate was offered at 2.1% of shrunk body weight. Steers were adapted to the base diet for 24-d then introduced to predetermined treatments for 35 d. In situ digestibility data were collected weekly over 5 wk. Digestibility estimates were determined using 48-h in situ disappearance of DM and NDF. Data were analyzed using a random coefficients model. There was no difference in DM or NDF intake for dietary treatment (P = 0.66, and P = 0.65, respectively). However, on week 2 QT2 had lower DMD (P = 0.03) and tended to decrease NDFD (P = 0.06) compared to QT1, and QT3. In contrast, there was no observed difference (P = 0.22) in DMD, and NDFD on week 1, 3, 4, 5, and when the 5-wk data were combined. The addition of QT up to 3% DM in a roughage-based diet does not sacrifice DMD and NDFD over time, but it is not clear as to why QT2 affected DMD and NDFD.

PSIV-B-23 Late-Breaking: Detection of dietary external markers using portable X-ray fluorescence spectrometry for estimation of digestibility in beef cattle

Abstract The use of portable X-ray fluorescence (PXRF) spectrometry to detect dietary external markers on processed or unprocessed bovine fecal specimens to estimate apparent total tract digestibility (ATTD) was evaluated. Seven beef crossbred, ruminally-cannulated steers (BW = 520 ± 30 kg) were used in a completely randomized design. Steers were individually fed a steam-flaked corn-based finishing diet ad libitum for 21-d. Degradable gel capsules containing 7.5 g of titanium dioxide and chromic oxide were placed inside the rumen through the ruminal-cannulae twice daily, throughout the experiment. Fecal samples were collected twice daily from d 14–21, stored frozen (-20oC), and thawed on d-21 to make a composite sample per steer/day. Wet chemistry analyses of fecal samples included atomic absorption for Cr and spectrophotometry for TiO2 and were compared with PXRF to determine the concentration of these markers on three types of fecal specimens: fresh (average 22.5 % DM), dried (60oC, 72 h), or dried/ground (1 mm). Data were analyzed using the GLIMMIX procedures of SAS with collection day as a repeated measure. Delta between ATTD estimated by wet chemistry and PXRF was not different from zero when using fresh fecal specimens analyzed for Cr (P = 0.40) or Ti (P = 0.14), while for dried or dried/ground specimens it differed (P ≤ 0.04), in which ATTD was underestimated by 3.6 and 1.1 percent units for Cr and Ti, respectively, when using PXRF. Concentration of Ti in fecal specimens was similar (P = 0.39) between analytical methodologies regardless of sample preparation. However, concentration of Cr was underestimated (P < 0.01) by 13% when PXRF was used in dried or dried/ground fecal samples compared to wet chemistry. Detection of Cr and Ti in fresh fecal samples with PXRF spectrometry seems to be a viable alternative to wet chemistry for estimating ATTD for finishing steers.

PSIX-27 Moo-vie Snacks: Storage stability and nutritive value of waste popcorn as a feedstock

Abstract The use of by- or co-products in livestock production is not a novel concept. However, as adoption of a novel feed ingredient increases, the cost efficiency of its use generally decreases. Therefore, discovery of novel feed ingredients is a worthwhile academic pursuit. Our objective was to determine the storage stability of popcorn (Zea mays L.) in terms of gain or loss in nutritive value. Popcorn was collected on consecutive weekdays in two wk from a local cinema. Samples (n = 10) were subdivided into 9 aliquots and subjected to storage, uncovered, for 0, 1, 2, 3, 7, 35, 70, 105, and 140 d. Following the assigned storage time, samples were dried at 55°C to determine weight loss. Samples were dried at 55°C, ground to pass through a 2-mm screen, and subjected to a batch-culture in vitro assay for digestibility estimates [in vitro true digestibility (IVTD) and in vitro NDF digestibility (IVNDFD)]. Subsamples were ground to 1 mm assayed for neutral detergent fiber and acid detergent fiber. There was a linear increase (P < 0.01) in weight following open storage which was attributed to absorption of ambient moisture. There was a linear decrease (P = 0.03) in NDF, with values decreasing from 20.2% at d 0 to 16.6% at d 140. However, there was no effect of storage on ADF (P = 0.29), IVTD (P = 0.38), or IVNDFD (P = 0.37). Results are interpreted to mean that waste popcorn is relatively shelf stable and may be a viable candidate as a feedstock for diet formulation.

Comparison of Faecal versus Rumen Inocula for the Estimation of NDF Digestibility

Simple SummaryThe evaluation of fibre digestibility is very important for the formulation of ruminant diets. Fibre digestibility is usually determined in lab with rumen inoculum obtained from cannulated cows. The research of alternative and less invasive inoculum sources is a critical issue that should be addressed. The present study evaluated the potential of faecal inocula, obtained from cows fed different diets, to assess fibre digestibility of different substrates at different incubation times (48, 240 and 360 h). At short incubation time, fibre digestibility obtained with rumen fluid was always higher than those obtained with faecal inocula, confirming a lower activity of the faecal inocula compared with rumen fluid. However, the type of diets fed to the donor animals had a significant effect on fibre digestibility, with a more active faecal inoculum for cows fed a diet based on maize silage. Despite the differences obtained at the short incubation time, the digestibility values at longer intervals showed that faecal inoculum could replace rumen inoculum. As a consequence, faeces may replace rumen fluid as inoculum for end-point measures, avoiding the use of cannulated animals and decreasing the analytical costs.Cow faeces have been investigated as alternative inoculum to replace rumen fluid to determine neutral detergent fibre (NDF) digestibility (NDFD). Aims of this study were to estimate: (1) the NDFD (48 h) of feed ingredients using a rumen inoculum in comparison with faecal inocula from cows fed diets with different forage basis; (2) the undigestible NDF (uNDF) at 240 and 360 h with ruminal fluid and faecal inocula from lactating cows fed two different diets. At 48 h incubation, the NDFD was affected both by feed and type of inoculum (p < 0.01) and by their interaction (p = 0.03). Overall, the mean NDFD was higher for rumen inoculum than for faecal inocula (585 vs. 389 g/kg NDF, p < 0.05), and faecal inoculum obtained from cows fed hay-based diets gave lower NDFD than those from cows fed maize silage (367 vs. 440 g/kg, p < 0.05). At long incubation times, the average uNDF was affected by substrate, inoculum and incubation time (p < 0.01), but not by their interactions. For each inoculum, significantly lower values were obtained at 360 than at 240 h. Regressions between uNDF with rumen and with the tested faecal inocula resulted in r2 ≥ 0.98. Despite the differences at 48 h, the uNDF showed that faecal inoculum could replace rumen fluid at longer incubation times.

Assessment of in situ techniques to determine indigestible components in the feed and feces of cattle receiving supplemental condensed tannins1.

Reliable assessments of indigestible dietary components are required when using internal markers to estimate diet digestibility and determine the potentially digestible portion of the fiber. The lack of a standardized methodology and understanding of how antinutritional factors influence indigestible residues can result in erroneous estimates with inconsistent variation across trials and among studies. Previous studies have detailed suitable bag porosity and sample size (SS) with incubation length (IL) varying from 96 to 504 h, with many assuming that 288-h IL yields truly indigestible components. Recent studies have primarily investigated the variation that exists among feedstuffs, but most have failed to account for possible effects of secondary compounds. Using 2 similar concentrate diets, one of which contained supplemental condensed tannins (CT), we investigated the effect of bag type (BT; 10 and 25 μm), SS (20 and 40 mg/cm2), and IL (288 and 576 h) on in situ indigestible DM (iDM) and neutral detergent fiber (iNDF) residues of feed and feces, and resultant DM and NDF digestibilities. There were no 3-way interactions (P > 0.05), but 2-way interactions were present for iDM and iNDF residues with BT × SS influencing the control (no CT) ration (P < 0.01), SS × IL impacting feed containing CT (P < 0.01), and BT × IL affecting both feedstuffs (P ≤ 0.01). For the control diet, only BT × SS affected DM and NDF digestibilities. Whereas the CT diet did not demonstrate any significant interactions for digestibilities. Values of iDM were largely influenced by contamination that varied greatly based on intrinsic factors associated with the bag and incubation duration. The presence of CT influenced iDM and iNDF to varying degrees due to possible trapping of CT-substrate complexes. For the control diet, the use of 25-μm bags resulted in lower fecal recoveries relative to the 10 μm (P < 0.01). However, there appears to be a dynamic relationship among BT, SS, and IL within respective diets and sample types that can affect indigestible components and resultant digestibility estimates. Based on simulations from these data, the sample size required to attain 90% power when utilizing 2 incubation animals exceeds the triplicate and quadruplicate replications commonly utilized. Further emphasizing the necessity for a more complete understanding of incubation dynamics to design biologically and statistically valid investigations.

Apparent and standardised ileal digestibility of amino acids in wheat, triticale and barley for broiler chickens at two different ages

ABSTRACT1. The influence of the age of broiler chickens on ileal amino acid (AA) digestibilities in three cereals was examined. The digestibility estimates, including both apparent (AID) and standardised (SID) coefficients, for wheat, triticale and barley samples were determined using 14 and 28 d old broilers of mixed sex, fed diets containing the test grains as the only source of protein.2. Each assay diet was offered to five replicate cages of 14 and eight birds respectively, for the 14 and 28 day samplings. On both sampling days, the contents from the lower half of the ileum were collected for determination of the AID coefficients. The SID coefficients were calculated using ileal endogenous amino acid (EAA) losses previously determined from birds fed an N-free diet.3. The average AID for essential AA (EAA) in triticale and barley were significantly higher at 28 day compared to those at 14 days. In contrast, the magnitude of AID coefficients of AA in wheat was found to be in larger in the younger chickens.4. Correction of AID for EAA losses increased the values of digestibility coefficients by an average of about 7%. The SID values of AA in wheat was not influenced by the age of broilers. The SID of most AA in triticale, and of all the AA in barley, were higher in 28-day-old chickens compared with their 14-day-old counterparts. The results suggested that the SID coefficients of EAA in wheat determined at day 28 could be applied to feed formulations for 14-day-old broilers, but in the case of triticale and barley, the values obtained in older chickens were not applicable in younger birds and vice versa.

95 Emerging Young Scholar: Impact of phosphorus recycling on the equine phosphorus requirement

Abstract Optimal dietary P intakes provide only what animals require, thus minimizing the excretion of P into the environment. Feeding programs for horses commonly include inorganic P in excess of requirements, because organic P (e.g. phytate-P) is thought to be poorly digested by the horse. We have observed that 95% of phytate is degraded by the time it reaches the feces, suggesting that phytate-P availability, and thus true P digestibility, may be greater than believed. In other species but not in horses, it is recognized that fecal P excretion is an important means of maintaining P homeostasis, but can result in low estimates of P digestibility and subsequently greater P requirements. Adjusting the estimates of digestibility that are used to calculate requirements would reduce P requirements and the use of inorganic P, which is in diminishing supply world-wide. This research evaluated two factors that could affect P excretion, a change in physiological state (from lactation to post-lactation) and weight loss. We found that post-lactational mares tended to excrete more P than control mares (P = 0.082), but fecal P excretion exceeded P intake for both groups of mares, and mares also lost weight during the study. In the subsequent study, horses fed to lose weight tended to excrete more P than horses fed to gain weight (P = 0.085). If horses lost weight in previous studies used to determine P digestibility it is likely that body P, and not just undigested dietary P, was recovered in feces, skewing digestibility estimates. We hypothesize that previous studies have underestimated P digestibility by horses and that requirements could be revised, resulting in a significant reduction in the amount of inorganic P added to equine diets and in the amount of P excreted into the environment.

190 Reduce Reuse ReRumen: Preservation method of rumen fluid collected from slaughtered cattle affects in vitro digestibility

Abstract Microbes and chemical constituents in the rumen fluid play an important role when re-establishing the rumen microbial population. Identification of a viable preservation method could have lasting implication of veterinary and research applications. Our objective was to determine the efficacy of preservation methods on rumen liquor. Twelve paunch samples were collected from slaughtered cattle at the Tarleton State University Meat Laboratory, Stephenville, TX. Rumen content was collected from different locations within the rumen, strained through eight layers of cheesecloth, and divided into five 500-mL aliquots. Aliquots were randomly allocated to one of five preservation methods (freezing or lyophilisation) and preservative (glycerol; yes or no). A fresh control was maintained from each sample. Three reference feeds and two roughage sources were used in the batch culture procedure. Reference feeds were dried to a constant weight at 55°C and ground to pass through a 2-mm screen. Ground samples were subjected to batch culture in vitro true digestibility (IVTD) assays using each of the four ruminal fluids (plus the control) for digestibility estimates. Original samples and incubated residues were assayed for DM, CP, NDF, and ADF. Data were analyzed in a 2 × 2 + 1 augmented factorial design using GLIMMIX procedure of SAS. There were no differences (P &gt; 0.05) in IVTD when using protein or energy feeds; however, there were differences in IVTD for all treatments for fiber concentrates and forage reference feeds. Despite lower degradation of feeds when frozen or lyophilized rumen fluid was used, preserved rumen fluid may be a viable option in the absence of fresh inoculum for veterinary and research applications

166 Moo-vie Snacks: Evaluation of waste popcorn as a feedstuff in comparison with known livestock feeds

Abstract While the use of by- or co-products can help offset the costs of feeding cattle, these feeds often increase in price with increased adoption. Therefore, discovery and characterization of novel feedstuffs could benefit the producer. Our objective was to evaluate the viability of waste popcorn (Zea mays L.) as a feedstuff in ruminant diets. This objective was addressed through a series of two experiments. In Exp. 1, storage stability of popcorn was evaluated. Popcorn was collected on consecutive weekdays in 2 wk from a local cinema. Samples (n = 10) were subdivided into 9 aliquots and subjected to storage, uncovered, for 0, 1, 2, 3, 7, 35, 70, 105, and 140 d. Following the assigned storage time, samples were dried at 55°C to determine weight loss. Following open storage in a laboratory at approximately 24°C, popcorn gained (P &lt; 0.05) between 2.6% (3 d) and 5.6% (105 d) of the original weight through moisture absorption. When dried, however, samples from any length of storage were within 1% of the original weight (P &lt; 0.05). In Exp. 2, a composite sample of popcorn was used in comparison with cracked and steam-flaked corn (Zea mays L.), popped milo [Sorghum bicolor (L.) Moench ssp. bicolor], and rolled barley (Hordeum vulgare L.). Samples were dried at 55°C, ground to pass through a 2-mm screen, and subjected to a batch-culture in vitro assay for digestibility estimates. In vitro true digestibility of popcorn (77.8%) was less (P &lt; 0.05) than estimates for cracked corn (94.8%), popped milo (93.6%), steam-flaked corn (92.6%), or rolled barley (90.3%). From these results, we may conclude that, while popcorn is not as digestible as other commercial energy sources, it may represent a viable option in the arsenal of feed formulation.

Vegetation Responses to Fixed Stocking Densities in Highly Variable Montane Pastures in the Chinese Altay

Variability in aboveground herbaceous biomass and its quality were studied in response to three different stocking densities during a 2-yr grazing experiment with sheep on a montane summer pasture in the Chinese Altay. We determined herbaceous cover and aboveground biomass in 16 paddocks of 0.25 ha each. Vegetation cover showed high spatial variation, prompting us to implement a randomized block design. Forage intake of one male sheep per paddock was quantified four times per grazing season by collection of total feces and estimation of diet digestibility. Sheep weight was recorded every 3 wk. Aboveground herbaceous dry mass (DM) was characterized by pronounced annual variation. Biomass quality declined with progressing season and increasing sheep density. Daily organic matter intake per sheep ranged from 0.7 to 1.4 kg, which was paralleled by a biomass removal of 710−1 560 kg DM/ha at densities of 8−24 sheep/ha. At 8 sheep/ha, animals gained weight throughout each grazing period, whereas weight losses of 40−100 g/d occurred at higher densities. These results challenge the presently followed concept of a fixed stocking density for summer pastures in Altay Prefecture, Xinjian, China. Such practice may result in low herbage allowances and thus deficient sheep nutrition in one year, as well as underutilization of forage resources in another. Flexible adjustment of stocking densities is also advisable for montane pastures where spatiotemporal variability, although less pronounced than in desert steppes of the Altay foothills, is nonetheless highly relevant.

Effects of dietary fiber content and different fiber-rich ingredients on endogenous loss of fat and fatty acids in growing pigs

Effects of dietary fiber content and different fiber-rich ingredients on endogenous loss of fat and fatty acids in growing pigs

Unveiling the relationships between diet composition and fermentation parameters response in dual-flow continuous culture system: a meta-analytical approach.

The objective of this study was to investigate the functional form of the relationship between diet composition (dietary crude protein [CP] and neutral detergent fiber [NDF]) and amount of substrate (fermenter dry matter intake [DMI]) with microbial fermentation end products in a dual-flow continuous culture system. A meta-analysis was performed using data from 75 studies. To derive the linear models, the MIXED procedure was used, and for nonlinear models, the NLMIXED procedure was used. Significance levels to fit the model assumed for fixed and random effects were P ≤ 0.05. Independent variables were dietary NDF, CP, and fermenter DMI, whereas dependent variables were total volatile fatty acids (VFA) concentration; molar proportions of acetate, propionate, and butyrate; true ruminal digestibilities of organic matter (OM), CP, and NDF; ammonia nitrogen (NH3–N) concentration and flows of NH3–N; non-ammonia nitrogen; bacterial-N; dietary-N; and efficiency of microbial protein synthesis (EMPS). Ruminal digestibilities of OM, NDF, and CP decreased as fermenter DMI increased (P < 0.04). Dietary NDF and CP digestibilities were quadratically associated (P < 0.01). Total VFA linearly increased as DMI increased (P < 0.01), exponentially decreased as dietary NDF increased (P < 0.01), and was quadratically associated with dietary CP (P < 0.01), in which total VFA concentration was maximized at 18% dietary CP. Molar proportion of acetate exponentially increased (P < 0.01) as dietary NDF increased. Molar proportion of propionate linearly increased and exponentially decreased as DMI and dietary NDF increased, respectively (P < 0.01). Bacterial-N quadratically increased and dietary-N exponentially increased as DMI increased (P < 0.01). Flows of bacterial-N and dietary-N linearly decreased as dietary NDF increased (P < 0.02), and dietary-N flow was maximized at 18% CP. The EMPS linearly increased as dietary CP increased (P < 0.02) and was not affected by DMI or dietary NDF (P > 0.05). In summary, increasing fermenter DMI increased total VFA concentration and molar proportion of propionate, whereas, dietary NDF increased the molar proportion of acetate. Dietary CP increased bacterial-N flow and was positively associated with NH3–N concentration. Overall, the analysis of this dataset demonstrates evidences that the dual-flow continuous culture system provides valuable estimates of ruminal digestibility, VFA concentration, and nitrogen metabolism.

Effects of free-choice hay and straw bedding on digestion of nutrients in 7-week-old Holstein calves

ABSTRACT Objective Bedding with long straw improves animal health and performance but could affect digestibility measurements if calves consume the bedding. Feeding hay with calf starters is common practice; however due to the limited capacity of the young calf’s rumen, high levels of roughage can lead to decreased DMI, digestibility, and ADG. The objectives of this study were to evaluate the effect of long-straw bedding and free-choice hay on nutrient digestibility in calves less than 2 mo old. Materials and Methods Sixteen calves (45.4 ± 1.18 kg of BW, 3 d of age) were bedded on long wheat straw or on rubber mats and fed diets with or without free-choice, long-grass hay. Calves were fed a 25% CP, 17% fat milk-replacer powder at 0.66 kg of DM 2 times per day for 35 d and then 0.33 kg of milk replacer 1 time per day for 7 d. Milk replacer was diluted to 14% DM. Calves were fed free-choice textured starter and water for the entire 56-d trial. Hay was 5.4% CP and 62.8% NDF (DM basis). Digestibility was estimated on d 47 to 51 using acid insoluble ash in feeds and feces as an internal marker. Results and Discussion Hay intake varied and reduced the digestion of dietary DM, OM, CP, and fat by calves. As hay intake increased, digestion of OM decreased linearly. Implications and Applications Long wheat straw as bedding did not change estimates of digestion in young calves consuming coarse, textured starter, whereas moderate- to low-quality hay intake reduced digestion.

Estimating compartmental and total tract apparent digestibility in horses using internal and external markers

Partitioning of apparent digestibility is helpful to assess the nutritive value of feedstuffs and to identify possible risks for digestive disorders. In horses, information on partial digestibility is less available and address less on carbohydrate fractions. It is suggested that large parts of water-soluble carbohydrates (WSC) are degraded already in the stomach, which elevates the risk for mucosal ulceration. Our objective was to investigate apparent digestibility of dry matter (DM), proximate nutrients, and WSC along the digestive tract using internal and external markers. Twelve adult horses were adapted for 20 d to meadow hay (1.5 kg/100 kg body weight per day) and crushed oats (1.2 g starch/kg body weight per day), which were offered 2 times a day. Six horses on the treatment group also received 0.15 g of fructooligosaccharides + inulin (via Jerusalem artichoke meal) per kg body weight per day. The other 6 horses on the control group received corncob meal without grains. The tested markers were 4 N acid insoluble ash (AIA), acid detergent lignin (ADL), n-heptacosane, n-nonacosane, n-hentriacontane, and n-tritriacontane. Additionally, Cr2O3 (approximately 2.8 g/bolus) and TiO2 (approximately 2.5 g/bolus) were provided as a bolus 2 times a day. The horses were euthanized at d 21 approximately 1 h after the morning meal. Samples of digesta were collected from the stomach (pars nonglandularis and pars glandularis), cecum, ventral and dorsal colon ascendens, and colon transversum. Feces were sampled at 5 d ante mortem. Compartmental and total tract apparent digestibility was calculated for each horse. The stomach seemed to be considerably involved in nutrient degradation with particular great disappearance of simple sugars, starch, and fructans (apparent digestibility was up to 78, 74, and 56%). No WSC were measured in the cecum. In the hindgut, apparent digestibility increased from the cecum to the colon transversum (e.g., for DM: 0.49–0.79 with AIA, and 0.44–0.56 with n-tritriacontane; for crude protein: 0.51–0.82 with AIA, and 0.47–0.63 with n-tritriacontane; and for neutral detergent fiber: 0.43–0.76 with AIA, and 0.37–0.50 with n-tritriacontane; P < 0.05). Supplying of fructooligosaccharides and inulin had no effect on apparent digestibility. Differences among apparent digestibility estimates did mainly belong to the gut compartments (P < 0.05) and the markers (P < 0.001). For all nutrients, apparent digestibility estimates did differ less among the plant alkanes, but they had a vast variation among the horses when based on Cr2O3 or TiO2. The extensive disappearance of WSC, including starch, in the stomach should be considered for dietary composition and risk assessment concerning stomach ulceration. Parts of WSC possibly had not been degraded in the stomach, but rapidly flowed with the liquid phase into the intestine. The probable underestimation of apparent digestibility by ADL confirms the known instability of ADL during the digestive process. Acid insoluble ash probably overestimated apparent digestibility along the hindgut, especially for the fiber fractions. Thus, apparent digestibility seemed to be best estimated by cell wall-associated plant alkanes. The estimations made by Cr2O3 and TiO2 were only accurate for the total tract, considering mealtime feeding of mixed diets.

Symposium review: Re-evaluation of National Research Council energy estimates in calf starters

Provision of nutrients in appropriate amounts to meet nutrient requirements for growth, production, and reproduction is the basis for modern animal nutrition. Ration formulation systems predict nutrient requirements based on numerous inputs and then predict nutrient supply based on predicted intake and nutrient content of feeds. Energy systems are used to predict energy supply based on gross caloric content of feeds followed by adjustments for digestion and metabolism of ingested energy. Many models of energy supply use static coefficients of digestibility based on nutrient composition of feed. Other models partition digestion dynamically between ruminal and postruminal digestion but use static estimates of intestinal digestibility to predict energy supplied to the animal. In young calves, both ruminal fermentation and intestinal digestion are underdeveloped; therefore, existing models of energy supply might overestimate the energy available before complete gastrointestinal maturation. In a series of experiments, we reported that total-tract digestion of nutrients changes with advancing age and nutrient intake. Total-tract digestion was measured in calves from 3 to 16 wk of age when fed different amounts and types of milk replacers. Calves were also fed different types of calf starter for ad libitum consumption. Total-tract digestibility of protein, fat, neutral detergent fiber, and nonfiber carbohydrate (NFC) was used to calculate the metabolizable energy (ME) in starter. We used nonlinear regression to estimate the contribution of protein and fat from starter and milk replacer before weaning. Early in life, calculated ME of starter was low and increased with increasing intake of NFC. Cumulative intake of NFC was more highly correlated with changing ME values than other indices, including age, intake of milk replacer, or intake of other nutrients in starter. When calves consumed at least of 15 kg of NFC, ME calculated from digestibility measurements was similar to the ME calculated using National Research Council equations and indicated maturation of gastrointestinal digestion. Our data suggest that intake of NFC is critical to gastrointestinal maturation and the calf's ability to extract energy from calf starter.

Estimates of calf starter energy affected by consumption of nutrients. 2. Effect of changing digestion on energy content in calf starters

Apparent total-tract digestibility data from 3 published studies with calves from 0 to 4 mo of age were used to evaluate National Research Council (NRC; 2001) estimates of digestible energy (DE) and metabolizable energy (ME) in calf starters (CS). Calves (n = 83) or pens of calves (n = 24) were used in model development. In each study, 48 Holstein bull calves (2-3 d of age at initiation of each study) were fed varying amounts of milk replacer with CS and water for ad libitum consumption. Calf starters varied in nutrient composition and physical form (pelleted, textured, or mixed with 5% grass hay and fed as a total mixed ration). Apparent total-tract digestibility was measured at various ages. Feed and feces were collected from 20 calves per trial during 5-d collection periods during the first 56 d of each trial. In 2 studies, calves were grouped in pens (4 calves/pen) for a second 56-d measurement period. Fecal collections were repeated occasionally during the second period. Total-tract digestibilities (n = 207) of neutral detergent fiber, nonfiber carbohydrates (NFC), crude protein (CP), and fat were used to calculate ME in CS using equations from the 2001 Dairy NRC. Contributions of digestible CP and fat from milk replacer before weaning were estimated using nonlinear regression and removed from estimates of fat and CP digestibility in CS. Digestion of most nutrients in CS and calculated DE and ME in CS were low early in life and increased with increasing cumulative NFC intake. The natural logarithm of cumulative NFC intake, measured from d 0 to the end of each digestibility period, accounted for more variation in CS nutrient digestibilities, DE and ME estimates compared with daily NFC intake or intake of other nutrients, intake of milk replacer, or age of calf. Calculated ME values in CS were similar to those predicted by NRC after calves consumed approximately 15 kg of cumulative NFC or 28 kg of cumulative dry matter intake (assuming 53% NFC in CS). Current estimates of energy in CS fed to 4 mo of age may overestimate contribution of dry feed to overall energy metabolism in young calves.

Evaluation of wedge wire screen as a new tool for faeces collection in digestibility assessment in fish: The impact of nutrient leaching on apparent digestibility of nitrogen, carbon and sulphur from fishmeal, soybean meal and rapeseed meal-based diets in rainbow trout (Oncorhynchus mykiss)

The study was carried out to evaluate wedge wire screen as a potential tool for collecting fish faeces from the tank outlet water. Apparent digestibility (AD) estimates of carbon (ADC), nitrogen (ADN), sulphur (ADS), organic material (ADORG) and individual amino acids obtained by the wire screen were compared with stripping. Three diets, with fishmeal, soybean meal (SBM) or rapeseed meal (RSM) as main protein source were extruded and fed to triplicate groups of 120-g rainbow trout (Oncorhynchus mykiss). Faeces were obtained by gentle stripping from the distal abdomen, and by collection from a wedge wire screen 15, 30, 60, 120 and 240 min post feeding. ADORG, ADN and ADS obtained by collection on the screen were significantly (P < .05) higher than those obtained by stripping, except for some values for ADC. Differences in AD between stripping and faeces collected with the wire screen were lower than reported for other methods of collection from water media. Most of the increase in AD of nutrients for wedge wire screen occurred during the first 15 min after defecation. The ADORG, ADC, ADN and ADS were lowest in the RSM diet. The AD of amino acids followed the same pattern as ADN. ADS in the rapeseed diet was particularly low (54.7%), compared to the fishmeal (72.4%) and SBM diet (70.1%). In addition to AD of cysteine, low digestibility of glucosinolates, its degradation products and other sulfonated components are likely reasons for the low ADS. Faeces from the RSM based diet had higher dry matter (DM) concentration than the SBM based diet. Faecal DM recovery for SBM was lowest among the diets for both collection methods. The low DM recovery for the SBM faeces did not affect AD estimates of faeces at the different time intervals, possibly due to simultaneous leakage of nutrients and indigestible marker. In conclusion, the use of wedge wire screen for collection of faeces represents an interesting supplement to stripping. The AD estimates had low random variation and nutrient leaching during faeces collection were dependent on dietary composition.

Effect of harvest method and ammoniation of baled corn residue on intake and digestibility in lambs.

To determine the effect of harvest method and ammoniation on both in vivo and in vitro digestibility of corn residue, six corn residue treatments consisting of three different harvest methods either with or without anhydrous ammonia chemical treatment (5.5% of dry matter [DM]) were evaluated. The harvest methods included conventional rake-and-bale (CONV) and New Holland Cornrower with eight rows (8ROW) or two rows (2ROW) of corn stalks chopped into the windrow containing the tailings (leaf, husk, and upper stem) from eight rows of harvested corn (ammoniated bales of each harvest method resulted in treatments COVAM, 8RAM, and 2RAM). Nine crossbred wether lambs (49.2 ± 0.5 kg BW) were fed 64.2% corn residue, 29.8% wet corn gluten feed, 3.3% smooth-bromegrass hay, and 2.8% mineral mix (DM basis) in a 9 × 6 Latin rectangle metabolism study with a 3 × 2 factorial treatment to measure total tract disappearance. Six 21-d periods consisted of 14-d adaptation and 7-d total fecal collection, and lambs were fed ad libitum (110% of the previous day’s DM intake [DMI]) during days 1 to 12 and reduced to 95% of ad libitum intake for days 13 to 21. There was a harvest method by ammoniation interaction (P < 0.01) for ad libitum DMI (days 7 to 11). Ammoniation increased (P < 0.01) intake across all harvest methods, where 2RAM DMI was 4.1%, COVAM was 3.6%, and 8RAM was 3.1%, which were all different (P < 0.01) from each other, but all untreated residues were consumed at 2.6% of BW (P ≥ 0.92) regardless of harvest method. There were no interactions (P > 0.34) between harvest method and ammoniation for any total tract or in vitro digestibility estimate. Harvest method affected (P < 0.04) DM, neutral detergent fiber (NDF), and acid detergent fiber (ADF) digestibility, where 2ROW was greater than both CONV and 8ROW, which did not differ. The organic matter (OM) digestibility (P = 0.12) and digestible energy (DE; P = 0.30) followed the same numerical trend. Both in vitro DM digestibility (IVDMD) and in vitro OM digestibility (IVOMD) of the residue were affected (P < 0.01) by harvest method, with 2ROW being greater (P < 0.01) than both CONV and 8ROW. For IVDMD, 8ROW was not (P = 0.77) different from CONV, but 8ROW IVOMD was lower (P = 0.03) than CONV. Ammoniation improved (P < 0.01) DM, OM, NDF, and ADF digestibility of all harvest methods, resulting in a 26% increase (P < 0.01) in DE due to ammoniation. Similar digestibility improvements were observed in vitro with ammoniation improving IVDMD and IVOMD by 23% and 20%, respectively. Both selective harvest methods and ammoniation can improve the feeding value of baled corn residue.

Caulim e óxido crômico sob diferentes formas de administração em estudo de consumo e digestibilidade

Animal nutrition needs simple methodologies to be applied under field conditions, providing valid estimates of consumption and digestibility that can be used by both farmers and animal input industry. Thus, the search for new substances, provided in a practical way, quantified by simple and low-cost analytical methodologies, replacing external indicators (chromic oxide used as reference) would be well accepted by the scientific community. In this context, the aim of this study was to assess the supply of chorionic oxide by esophageal route or mixed in the diet and the use of kaolin as an indicator, under the same forms of administration, to estimate fecal production and digestibility using four castrated male Holstein cattle. The experimental design was a 4 × 4 Latin square design, with four experimental periods of 12 days and six-day intervals between periods. Treatments consisted of supplying chromic oxide by esophageal route (COer), kaolin by esophageal route (Kaoer), chromic oxide mixed to the diet (COdiet), and kaolin mixed to the diet (Kaodiet). The treatment Kaodiet allowed obtaining estimates of fecal production similar to the treatment COer. The treatment COdiet did not differ from the treatment COer (p &gt; 0.05) considering all the assessed parameters, evidencing that the indicator chromic oxide can be supplied mixed directly in the diet without damaging the estimates of fecal production and digestibility. Under the studied conditions, kaolin was not an effective indicator to obtain accurate estimates of fecal production and further studies are needed to adjust the analytical techniques of aluminum extraction as well as to resolve some doubts regarding its digestion process.