Estimation Of Digestibility Research Articles

Estimation of Fiber Fragility and Digestibility of Corn Silages and Cool Season Pastures

Fiber fragility is defined as the particle size reduction rate during chewing and can help to explain the effects on feed intake and animal performance of different fiber sources. This study aimed to estimate the fiber fragility of corn silage and cool-season pasture based on their chemical composition. Between June and December 2022, 25 samples of corn silage and 25 samples of cool-season pasture were collected from dairy farms in the state of Rio Grande do Sul. The samples were analyzed for particle size distribution, chemical composition, and fiber fragility. Contents of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), and fiber fragility were greater in corn silages compared to cool-season pasture. However, the ADF–NDF ratio was similar in forages. Crude protein (CP) content and the in situ degradation of DM and NDF were greater in cool-season pasture than corn silage. Dry matter and NDF in situ degradation were negatively correlated with increased contents of ADF, NDF, and ADL and the ADF–NDF ratio in forages. Fiber fragility was negatively correlated with DM degradation and positively correlated with contents of ADF, NDF, ADL, and DM. Fiber fragility decreased as CP content increased. Thus, greater fiber fragility may jeopardize nutrient degradation, and levels of fiber fragility are directly associated with fiber content.

Fecal image-based starch digestibility estimation in fattening cattle using deep learning

Estimating starch digestibility in cattle can be facilitated by examining starch content in their feces. Nonetheless, the chemical analysis of fecal starch content, which typically involves enzymatic reactions and colorimetry, is time-consuming and labor-intensive. In this study, we aimed to formulate a fecal image-based system to assess starch digestibility in fattening cattle. Images of the feces, including undigested corn particles, were taken with a smartphone’s color camera. The image dataset utilized in our experiments encompassed 4,570 images derived from 154 fecal samples obtained from six farms dedicated to fattening cattle. To assess the adaptability of our models, we conducted evaluations based on data from fecal samples originating from an external farm—one that was not included in the initial training set. Estimating fecal starch content involved utilizing three distinct models: EfficientNetV2, YOLOv8, and random forests. These models were built upon information about fecal water content, corn area, and the number of corns present. Subsequently, starch digestibility was derived from the estimated fecal starch content using an equation based on chemical analysis, as established in a previous study. Our proposed system exhibited an R2 and an RMSE of the estimated fecal starch content of 0.589 and 5.49% of dry matter, respectively. Furthermore, the RMSE of the estimated starch digestibility was 2.36%. These findings underscore the practicality of our starch digestibility estimation system when applied to fecal image analysis. This system holds promise in contributing to the real-time monitoring of the digestive system’s health status in individual farm animals.

Using faecal nitrogen as a marker to estimate intake and digestibility in sheep fed multi-species native forage

Livestock production in southern South America heavily relies on extensive native grasslands, characterized by high plant species diversity, which makes estimating forage digestibility and intake by ruminants in this pastoral ecosystem challenging. Therefore, the aim of this study was to develop regression models to establish the relationship between total faecal nitrogen excretion (FNe) and organic matter (OM) intake, and faecal nitrogen content (FNc) and OM digestibility in sheep fed multi-species native forage. In a completely randomized design, 16 Corriedale sheep averaging 44 kg of body weight (BW) were housed in metabolism cages and received forage in amounts of 15, 20, 25 g of dry matter per kg of BW or ad libitum. During the spring of 2019 and the summer of 2020, four measurement periods were carried out. The sheep had 5 days of adaptation to the metabolism cage, 10 days to adapt to the treatments of amounts of forage offered, and 5 days for intake and digestibility measurements. The forage was harvested once a day, and then the fresh forage was offered at two different times, 8 and 17 h. A linear regression model was developed to estimate OM intake in sheep fed multi-species native forage based on the FNe [Intake (g OM/sheep/day) = 107.7 + 101.5 × FNe]. An exponential regression model was developed to estimate forage OM digestibility in sheep based on the FNc (Digestibility = 0.31411e0.02995 × FNc). In conclusion, our findings highlight that the OM intake can be precisely estimated using FNe and a reasonably precise estimation of the forage OM digestibility can be reached by assessing FNc in sheep fed a multi-species native forage from the Rio de la Plata region in South America.

255 Anchor Talk: Consider intrinsic factors that regulate homeostasis to optimize sustainability of mineral supplements for swine

Abstract Decades of research has focused on methodologies to improve the efficiency of mineral use while assuring sufficient intake to meet animal well-being and production needs. A primary focus of these efforts is P, as P is the third most expensive category of nutrients supplemented in swine diets. Bioavailability of P is more variable than other nutrients in feed ingredients commonly fed to swine. Due to complexities involved in assessments of P bioavailability efforts shifted to defining P digestibilities for each ingredient. Efforts to refine P digestibilities, based on intake and fecal excretion, even with corrections for endogenous losses, have failed to provide a constant coefficient for feed ingredients that can be included in diet formulations, as the digestibility estimates vary with animal age, production phases and inclusion of enzymes such as phytase. An under-appreciated contribution to inaccuracies of digestible P relates to intrinsic regulation of Ca and P homeostasis by the animal. Regulation of Ca and P homeostasis by PTH and 1,25(OH)2D3, must now include a third mineralotropic hormone, FGF23. Applying insights for intrinsic roles of FGF23 will allow more efficient use of nutrients, especially P and vitamin D. FGF23 regulates activation of vitamin D and controls renal P excretion. Over-supplementation of P signals osteocytes (bone cells embedded in a mineralized matrix) to release intact FGF23 which targets the kidney to block reabsorption of P for maintenance of soft tissue homeostasis, resulting in an inefficient use of dietary P. Intact FGF23 also inhibits hydroxylation of 25-OH D3 to form 1,25(OH)2D3. These endocrine pathways illustrate major roles provided by kidneys and bone to allow adaptation to variable Ca and P inputs, thus maintaining homeostasis. Recent efforts to assess P requirements of sows during gestation and lactation illustrate the sensitivity of using renal excretion of Ca and P to assess requirements. Based on 24-h collections, urine Ca:P ratios > 1.5 were consistent with deficient P intake, ratios from 0.5 to 1.5 reflected P adequacy, and ratios < 0.5 indicated excessive P intake. As a practical method, spot urine samples collected at variable times throughout the day reliably predicted Ca:P ratios in 24-h urine collections. Thus, a simplified approach using Ca to P ratio in spot urine samples can be used to assess P intake adequacy. This practical approach can be applied in commercial sow herd to allow herd-based assessment of P status. In conclusion, within herd assessments, based on urine Ca:P ratios, can be used to determine if P supplements are deficient, adequate, and excessive. As such, significant progress can be made to provide a balance between the need to adequately meet animal need with efforts to minimize negative environmental impacts from over-supplementation of P.

Evaluation of internal markers in digestibility estimation for sheep and goats.

The objective of this study was to compare the indirect methods of obtaining digestibility with the direct method of total fecal collection to estimate the apparent digestibility of nutrients in sheep and goats supplemented with non-protein nitrogen. Five goats and five sheep with no defined racial pattern were used, distributed in two 5 × 5 Latin squares, with split plots, considering the diets as plots and the apparent digestibility determination methodologies as subplots. The diets were composed of buffelgrass hay and the addition, via ruminal infusion, of increasing amounts of nitrogen supplementation in order to gradually raise the CP level of the basal diet in intervals of 2% points, that is, + 2, +4, + 6 and + 8%. Samples of the feeds offered, and the leftovers were collected daily during the five days of collection to determine the nutrient intake, as well as the total collection of feces to determine the apparent digestibility of the nutrients. The amount of fecal dry matter excreted was estimated by the concentration of Indigestible Acid Detergent Fiber (ADFi), Indigestible Neutral Detergent Fiber (NDFi), Indigestible Dry Matter at 244h (DMi 244h) and Indigestible Dry Matter at 264h (DMi 264h). Among the evaluated markers, DMi 264h had the lowest accuracy in estimating fecal excretion and nutrient digestibility. For the goat species, the markers ADFi and DMi 244h proved to be able to adequately predict fecal excretion and digestibility indices, while NDFi stood out for both species. Among the evaluated markers, NDFi is the one that most accurately estimates the nutrient digestibility of the diet for goats and sheep.

Effectiveness of near-infrared spectroscopy to predict the chemical composition of feces and total-tract apparent nutrients digestibility estimated with undigestible neutral detergent fiber or acid-insoluble ash in lactating buffaloes' feces

Following a comparison of nutrient total-tract digestibility estimates in lactating buffaloes using single-point undigestible NDF (uNDF) or acid-insoluble ash (AIA) as internal markers, the potential of fecal near-infrared spectroscopy (NIRS) to provide calibration equations for the assessment of the chemical composition of feces and nutrient total-tract digestibility estimated with internal markers was explored. Chemical analyses were performed on 147 fecal samples from lactating buffaloes reared on 5 farms in central Italy (Naples). Each farm fed a silage-based TMR to the buffaloes, and the TMR was sampled in the 2 d before the fecal collection. The TMR and individual fecal samples were collected and analyzed for DM, OM, ash, AIA, ether extract (EE), starch, fiber fractions (amylase-treated NDF without residual ash [aNDFom], amylase-treated NDF inclusive of residual ash [aNDF], ADF without residual ash [ADFom], ADF, hemicellulose, cellulose, ADL, uNDF), N, CP and CP bound to aNDF (NDICP) and to ADF (ADICP). The uNDF content was determined through a 240-h in vitro fermentation and employed, together with AIA as markers, to estimate the total-tract apparent digestibility and total-tract digestibility of DM, OM, ash, N, CP, EE, aNDFom, aNDF, NDIP, ADFom, and ADF, ADIN, ADL, hemicellulose, cellulose, starch, NFC, and the B3 fraction of N (NB3). No correlation was found between DM and OM digestibility estimated with AIA and uNDF as internal markers. Weak correlations were detected for all the other nutients digestibilities, and strong correlations were observed for EE, ADFom, hemicellulose, NDIN, ADIN, NB3, NFC, and starch. The sample set (n = 147) was divided in a calibration set (n = 111) and a validation set (n = 36) to "train" and "validate" the fecal NIRS curve through an external validation process. An estimation usable for preliminary or initial evaluation was obtained for N, CP, and aNDF fecal content. An excellent prediction was obtained for total tract digestibility of ADIN (R2 = 0.90) when estimated with uNDF as the internal marker. The NIRS technology was not able to accurately predict all the other traits and the estimated nutrient digestibility of lactating buffalo diets from fecal spectra.

81 Effect of thymol on intake and digestion in beef cattle

Abstract Reducing enteric methanogenesis has been an area of focus and significance as methane emissions from cattle contribute to climate change and represent a loss of dietary-derived energy. Methane mitigation strategies have been widely researched, but most are limited in practical value due to associated diminishments in animal performance. One strategy, dietary supplementation of essential oils, has demonstrated variable reductions in enteric methane production in ruminants. The efficacy of using essential oils to reduce enteric methanogenesis likely varies due to inconsistent concentrations of bioactive components. Therefore, it is justified to investigate the effects of these individual bioactive components on methanogenesis and animal performance. Thymol, a terpene and main bioactive component in many essential oils, has effectively reduced methane production in vitro but in vivo data are limited. The objective of this study was to assess thymol fed at levels that correspond with effective in vitro doses on intake and digestion in beef steers consuming forage. This study was approved by the Texas State University IACUC (#8693). The project was a 4×4 Latin Square where four steers were provided one of four levels of thymol (0, 120, 240, and 480 mg thymol/kg forage intake) soaked on alfalfa cubes fed at 20% of the intake from the previous day, and ad libitum hay and water daily. Periods were 28-d with 8-d to adapt steers to treatments, 5-d to measure intake and digestion, 2-d to collect additional samples (i.e., ruminal microbiome and fat tissues), and a 14-d washout period for thymol depletion from the animal system. Diet, refusal, and fecal samples were analyzed for dry matter, organic matter, and fiber. Acid detergent insoluble ash was used to calculate total fecal production for digestibility estimates. Data were analyzed using the MIXED procedure in SAS 9.4. There was no effect of thymol dose on forage OMI (4.61 kg/d ± 0.31; P ≥ 0.48), total OMI (5.65 kg/d ± 0.38; P ≥ 0.44), or total digestible OMI (3.18 kg/d ± 0.18; P ≥ 0.26). Further, organic matter and neutral detergent fiber digestibility were not affected by treatment (56.70% ± 2.81, and 63.04% ± 2.49 respectively; P ≥ 0.14). These data indicate that thymol supplementation at doses that suppress in vitro methane production do not negatively impact intake and digestion in beef cattle. Future project activities include whole genome sequencing of rumen microbial communities to evaluate the impact of thymol on populations, with an emphasis on the methanogen archaea. These data have value for establishing a novel methane-mitigating feed additive to lower the carbon footprint of cattle production without sacrificing performance.

Estimation of ruminal digestibility and fermentation characteristics of coffee pulp: A meta-analysis of in vitro experiments

Integrating various studies with statistical methods can be used by applying a meta-analysis method. The objective of this meta-analysis was to evaluate the effect of coffee pulp as ruminant feed on in vitro digestibility and rumen fermentation characteristics. The database was developed from six related articles containing 25 studies, collected from Scopus and Google Scholar. The parameters integrated were in vitro dry matter digestibility (IVDMD), in vitro organic matter digestibility (IVOMD), pH value, total volatile fatty acids (VFA), NH3 and total protozoa. The data were analyzed using a mixed model methodology. The level of coffee pulp was considered as a fixed factor and the different studies as a random effect. The results revealed that coffee pulp addition had a significant quadratic effect to enhance IVDMD (P<0.01) and a significant linear effect to decrease total VFA (P<0.05). However, coffee pulp addition did not significantly affect (P>0.05) on IVOMD, pH, NH3 and total protozoa. In conclusion, coffee pulp can be used as an alternative feedstuff due to its good digestibility in the rumen. Nevertheless, it should be applied in the right amount to avoid negative effects on animal performance.

Beyond the Bowl: Understanding Amino Acid Requirements and Digestibility to Improve Protein Quality Metrics for Dog and Cat Foods.

The determination of amino acid (AA) requirements for mammals has traditionally been done through nitrogen (N) balance studies, but this technique underestimates AA requirements in adult animals. There has been a shift toward researchers using the indicator amino acid oxidation (IAAO) technique for the determination of AA requirements in humans, and recently in dogs. However, the determination of AA requirements specific to adult dogs and cats at maintenance is lacking and the current requirements outlined by the National Research Council are based on a dearth of data and are likely underreporting the requirements of indispensable AA (IAA) for the population. To ensure the physiological requirements of our cats and dogs are met, we need methods to accurately and precisely measure digestibility. In vivo methods, such as ileal cannulation, are most commonly used, however, due to ethical considerations, we are moving away from animal models and toward in vitro methods. Harmonized static digestion models have the potential to replace in vivo methods but work needs to be done to have these methods more accurately represent the gastrointestinal tract (GIT) of cats and dogs. The Digestible IAA Score (DIAAS) is one metric that can help define protein quality for individual ingredients or mixed diets that uses AA SID estimates and ideally those can be replaced with in vitro AA digestibility estimates. Finally, we need accurate and reliable laboratory AA analyses to measure the AA present in complete diets, especially those used to quantify methionine (Met) and cysteine (Cys), both often limiting AAs in cat and dog diets. Together, this will guide accurate feed formulation for our companion animals to satisfy requirements while avoiding over-supplying protein, which inevitably contributes to excess N excretion, affecting both the environment and feed sustainability.

Effect of day-old chick weight on the response of broilers to high doses of exogenous phytase

A total of 360 Ross 708 male broiler chicks were used in an 8 treatment and 9 replicate cage study to explore the influence of day-old chick weight on the efficacy of exogenous phytase. Treatments were arranged as a 2 × 4 factorial with the factors being diet (a positive (PC) and negative control (NC) varying in nutrient density fed without or with 2 concentrations of exogenous phytase) and chick weight (light; <38.5 g or heavy; >42 g). Chicks were sourced from the same breeder flock, with light and heavy chicks being selected from the naturally occurring heterogeneity in the population. The diets were corn-soybean meal based and the PC was formulated to meet the nutrient requirements of male broiler chicks. The NC was formulated to contain 120 kcal/kg, 0.5, 0.18, and 0.18% less apparent metabolizable energy (AME), crude protein (CP), calcium (Ca), and phosphorus (P), respectively, than the PC. Amino acid (AA) density in the NC was also reduced in line with the reduction in CP and the manufacturers' recommendations for the effect of phytase on amino acid digestibility. Phytase at either 1,000 FYT/kg or 3,000 FYT/kg was added only to the NC to create a total of 4 diets. Water and mash feed were available ad libitum and were offered to 8 replicate cages, each containing 5 chicks. The experiment was conducted over a period of 3 wk and diets were offered in 2 phases (starter from d 1 to 10 and grower from d 11 to 21). Growth performance was monitored at the end of each diet phase and on d 21 ileal digesta were collected for estimation of apparent digestibility of energy (DE), nitrogen (N), Ca, P, dry matter (DM), and AA. There were no statistically significant interactions between diet and day-old chick weight for any of the measured parameters. Light chicks had significantly lower weight gain (approx. 5%) at both d 10 and d 21 compared with heavy chicks. This effect was principally associated with reduced feed intake and there was no significant effect of chick weight on feed conversion ratio (FCR). Chick weight had no effect on ileal nutrient digestibility. The reduction in nutrient density from the PC to the NC generated a significant reduction in weight gain (around 12%) and a significant increase in FCR (1.68 vs. 1.83). This effect was associated with a significant reduction in ileal DE (approximately 150 kcal/kg) and in the digestibility of several AA. Exogenous phytase significantly increased weight gain, reduced FCR and generated a significant increase in the ileal digestibility of energy, N, P, and several AA. Although chick weight and diet did not interact statistically, heavy chicks benefited more than light chicks from high doses of exogenous phytase across almost all measured end points which was confirmed by regression analysis. In conclusion, light chicks have inferior performance outcomes than heavy chicks principally because of reduced feed intake, but putatively not in digestive capacity per se. Exogenous phytase is effective in improving performance and nutrient digestibility in nutrient deficient diets. The effect of chick weight per se, and also breeder flock age, on the utility of supra-nutritional inclusion concentrations of exogenous phytase warrants further study.

PSX-26 A Comparison of Buffer Type and Methodology in Determination of in Vitro Digestibility of Four Bermudagrass Cultivars

Abstract Buffers are an essential component in various biochemical and biophysical assays, enabling the control of pH shifts in the environment. The Tilley and Terry (1963) and Goering Van Soest (1970) methods dominate in vitro forage digestibility research with equally viable results. However, the methods utilize distinct buffer solutions to control the in vitro environment. Given this divergence, it is of interest whether differences in estimates are a factor of the methodology, or the buffer solutions employed in the method. The objective of this study was to determine the effects of in vitro DM digestibility (IVDMD) methodology and buffer solution on digestibility estimates of four bermudagrass cultivars. We conducted our experiment as a randomized complete block design with a 2 × 2 × 4 factorial treatment structure. Approximately 1,000 mL of rumen content (solid and liquid fractions) were collected from two ruminally fistulated heifers in each of two periods (blocks). The samples were separated into two 500-mL aliquots; the first aliquot was subjected to the procedures of Tilley and Terry (1963), and the second aliquot was subjected to the Goering and Van Soest (1970) procedure. Duplicate samples of four bermudagrass cultivars (Coastal, Russell, Tifton 44, Tifton 85) were placed in 125-mL Erlenmeyer flasks and incubated according to the assigned in vitro method. One-half of the samples in each method received the methodologically prescribed buffer solution, and the other one-half in each method received the opposite buffer. There was no effect of in vitro method (P = 0.78), buffer solution (P = 0.53), or bermudagrass cultivar (P = 0.46), or their interactions (P ≥ 0.23) on IVDMD estimates in this experiment. Results are interpreted to mean that buffer type is not pivotal to methodological success, and both methods will yield similar estimates of digestibility.

Short communication: Estimation of ileal digestibility in chickens using single- and dual-tracer methods

Fractionation of digesta, as occurs during gastrointestinal transit in chickens, complicates accurate measurements of ileal digestibility using tracers. Dual-tracer methods using separate tracers for solid and fluid digesta phases may improve the accuracy of digestibility measurements when assumptions of the single tracer method are violated. The aim of the present study was to compare the apparent ileal digestibility (AID) of nutrients calculated with single- and dual-tracer methods in chickens fed diets varying in particle size, anticipating digesta phase separation in the proximal gastrointestinal tract. A total of 112 Dekalb White (BW: 1.53 ± 0.107 kg) and 112 Bovans Black (BW: 1.79 ± 0.127 kg) 29-week-old laying hens were distributed over 32 pens (seven birds/pen). Within breed, pens were randomly assigned to one of two experimental diets (coarse vs fine oat hulls; n = 8 replicate pens per diet/breed combination). Diets were supplemented with TiO2 (3 g/kg) and Co-EDTA (2 g/kg). On days 34, 35, or 36, birds were euthanised and digesta from the ileum was collected for tracer and nutrient analyses. Apparent ileal digestibility was subsequently calculated by single- and dual-tracer methods. Although coarse oat hulls were hypothesised to increase the fractionation of solid and fluid digesta phases, no breed or diet × method interactions were found. Using a single tracer method based on TiO2, AID of nitrogen (N) was overestimated by 3%-units (P < 0.01) compared with the dual-tracer method, whereas AID estimates of DM, starch, fat, and non-starch polysaccharides did not differ (P > 0.09) and precision of all AID estimates was improved. In conclusion, these results show that although from a conceptual perspective, dual-tracer methods are presumed to better account for the variation in flow behaviour of different digesta phases, AID estimates obtained by the commonly used single tracer method using solid-phase tracer TiO2 were more precise and only marginally differed from estimates obtained by a dual-tracer method using distinct tracers for solid (TiO2) and liquid (Co-EDTA) digesta phases. Considering technical and economical constraints, the single tracer method may thus be the method of choice in many situations. Only when digestibility of proteins or amino acids is of specific interest, single tracer methods using a solid-phase tracer may not suffice. Nevertheless, for both single- and dual-tracer methods, tracer selection is critical, and the choice of tracers should depend on the nutrient(s) of interest.

Effects of direct-fed microbial supplementation on performance and immune parameters of lactating dairy cows

We evaluated the effects of supplementing bacterial direct-fed microbial (DFM) on performance, apparent total-tract digestibility, rumen fermentation, and immune parameters of lactating dairy cows. One hundred fourteen multiparous Holstein cows (41 ± 7 DIM) were used in a randomized complete block design with an experiment comprising 14 d of a covariate (pre-experimental sample and data collection) and 91 d of an experimental period. Cows were blocked based on energy-corrected milk (ECM) yield during the covariate period and the following treatments were randomly assigned within each block: (1) control (CON), corn silage-based total mixed ration without DFM; (2) PRO-A, basal diet top-dressed with a mixture of Lactobacillus animalis and Propionibacterium freudenreichii at 3 × 109 cfu/d; and 3) PRO-B, basal diet top-dressed with a mixture of L. animalis, P. freudenreichii, Bacillus subtilis, and Bacillus licheniformis at 11.8 × 109 cfu/d. Milk yield, dry matter intake (DMI), and body weight were measured daily, while milk samples for component analysis were taken on 2 consecutive days of each week of data collection. Feces, urine, rumen, and blood samples were taken during the covariate period, wk 4, 7, 10, and 13 for estimation of digestibility, N-partitioning, rumen fermentation, plasma nutrient status and immune parameters. Treatments had no effect on DMI and milk yield. Fat-corrected milk (3.5% FCM) and milk fat yield were improved with PRO-B, while milk fat percent and feed efficiency (ECM/DMI) tended to increase with PRO-B compared with PRO-A and CON. Crude fat digestibility was greater with PRO-B compared with CON. Feeding CON and PRO-A resulted in higher total volatile fatty acid concentration relative to PRO-B. Percentage of neutrophils tended to be reduced with PRO-A compared with CON and PRO-B. The mean fluorescence intensity (MFI) of anti-CD44 antibody on granulocytes tended to be higher in PRO-B compared with CON. The MFI of anti-CD62L antibody on CD8+ T cells was lower in PRO-A than PRO-B, with PRO-A also showing a tendency to be lower than CON. This study indicates the potential of DFM to improve fat digestibility with consequential improvement in fat corrected milk yield, feed efficiency and milk fat yield by lactating dairy cows. The study findings also indicate that dietary supplementation with DFM may augment immune parameters or activation of immune cells, including granulocytes and T cells; however, the overall effects on immune parameters are inconclusive.

Estimation of Energy Value and Digestibility and Prediction Equations for Sheep Fed with Diets Containing Leymus chinensis Hay

The objective of this study was to investigate the feeding value of sheepgrass, including its chemical composition, dry matter intake, nutrient digestibility, and available energy, as well as the prediction equations of dry matter intake (DMI), neutral detergent fiber digestibility (NDFD), dry matter digestibility (DMD), digestible energy (DE), and metabolizable energy (ME). Two independent experiments based on a completely randomized experimental design were performed to evaluate the feeding value. The results showed that there were significant relationships between chemical composition and DMI, digestibility, and available energy. The best-fit equations were as follows: DMI (g/d·W0.75) = 121.75 + 0.06CP (%) − 0.24EE (%) − 0.10ADF (%) − 0.60NDF (%) − 0.15OM (%) (R2 = 0.85, p &lt; 0.01), DMD (%) = −1.37 + 0.23CP (%) + 2.96EE (%) + 0.32ADF (%) − 0.82NDF (%) + 1.27OM (%) (R2 = 0.83, p &lt; 0.01), NDFD (%) = 225.58 − 0.59CP (%) + 0.04EE (%) + 0.09ADF (%) − 2.46NDF (%) + 0.12OM (%) (R2 = 0.67, p &lt; 0.01), DE (MJ/kg) = −5.19 + 0.38OM (%) − 0.26NDF (%) − 0.03ADF (%) + 0.16CP (%) (R2 = 0.91, p &lt; 0.01), and ME (MJ/kg) = 5.55 + 0.67DE (MJ/kg) + 0.01CP (%) − 0.01ADF (%) − 0.08NDF (%) + 0.02OM (%) (R2 = 0.98, p &lt; 0.01). This study found the energy value of sheepgrass to be 11 MJ/kg, which is similar to that of millet grass silage. The NDF was the main component that affected DMI and digestibility. Using a hay replacement ratio of 28.5% to determine the forage value of sheepgrass allowed accurate prediction equations to be established. The NDF demonstrated the strongest correlation with DMI, NDFD, OMD, DE, and ME. DE was estimated to be the best single predictor of ME.

Determining the protocol requirements of in-home cat food digestibility testing.

In-home cat food digestibility testing has the potential to yield data that are highly representative of the pet population for which the food is intended. However, no standardized and validated in-home digestibility test protocols are currently available. Such protocols for in-home testing should address key factors that explain variation in cat food digestibility values and here we investigated the required period of adaptation, fecal collection and sample sizes. Thirty privately-owned indoor housed cats of various breeds (20♀ 10♂, 5.9 ± 3.9 yr, 4.5 ± 1.3 kg) received a relatively low and high digestible complete dry extruded food with the marker titanium (Ti) dioxide. Foods were given in a cross-over design of 2 periods of 8 consecutive days each. Owners collected feces daily for the determination of daily fecal Ti concentrations and digestibility of dry matter, crude protein, crude fat, and gross energy. Data originating from 26 cats were analyzed as mixed models and broken line regressions to investigate the required adaptation and fecal collection period. Bootstrap sampling was used to assess the impact of increasing the number of fecal collection days and sample size on the precision of the digestibility estimates. Feces were collected on 347 out of 416 study days (16 days/cat; 26 cats), implying the necessity for multiple collection days to account for cats not defecating every day. Cats showed stable fecal marker concentrations from day 2 onwards when fed the low digestible food and from 3 onwards when fed the high digestible food. Digestibility values were stable from day 1, 2 or 3 onwards, depending on the test food and nutrient. Increasing the number of fecal collection days from 1 to 6 days did not result in more precise digestibility estimates, whereas increasing the number of animals from 5 to 25 cats did. For future in-home digestibility tests of cat food, the findings support a minimum of 2 adaptation days and 3 fecal collection days. Appropriate sample sizes depend on the test food, the nutrient of interest, and the acceptable margin of error. The findings of this study support the protocol development for future in-home digestibility testing of cat foods.

Intrinsic labelling of common beans with 2H2O to enable estimates of protein digestibility

ABSTRACT Background: The use of plant protein intrinsically labelled with stable isotopes provides an innovative solution to assess the efficiency of protein intake by humans. Here, the incorporation of 2H has been applied to intrinsically labelled plant protein in the common bean. This study aimed to evaluate which is the best phenological phase of seed maturation to incorporate the heavy hydrogen isotope 2H into seed amino acids. Common beans (Phaseolus vulgaris L.) were grown in pots, then, after 50 days sowing, 2H2O dissolved in irrigation water was applied, then again at an interval of either 3, 6, 9, and 12 days. Results: Applications of 2H2O at 6, 9, and 12 days after the first application, in the full-flowering stage, were the best treatments for enriching protein-bound amino acids in the bean seed with 2H. Conclusion: All treatments resulted in enrichment above 500 ppm, so the treatments (quantity and timing of 2H2O addition) were deemed successful for enriching bean seeds. This makes the intrinsically labelled seeds suitable for preparing test meals to assess the digestion and essential amino acid absorption of common bean amino acids in human subjects.

Can Associative Effects Affect In Vitro Digestibility Estimates Using Artificial Fermenters?

We aimed to test the associative effects among forages, and between forage and concentrates on the in vitro digestibility of dry matter and neutral detergent fibre using an artificial ruminal fermentation system. The study consisted of two assays, in which associative effects were evaluated among three forages, sugarcane, maize silage, and Tifton 85 hay under two incubation conditions (single feed or all feeds together in a jar), and the associative effects between sugarcane and soybean meal and/or ground maize. For the first assay, sugarcane digestibility increased (p &lt; 0.02), whereas the maize silage digestibility decreased (p &lt; 0.01) when forages were incubated together in the same jar. Tifton hay digestibility was not altered (p ≥ 0.57) by the incubation condition. In the second assay, the sugarcane digestibility was depressed (p &lt; 0.05) when the forage was incubated along with maize grain. For both assays, the pattern of repeatability for digestibility estimates presented an influence of the incubation condition. We concluded that the incubation of different feeds together in the same jar using artificial fermenters causes associative effects among them. These effects can influence the estimates of in vitro dry matter and fibre digestibility and alter their repeatability.

Evaluation of N-alkanes as Faecal Markers to Estimate Diet Composition, Feed Intake, and Digestibility in European Bison (Bison bonasus)

There is a lack of knowledge on the European bison (Bison bonasus L. 1758) foraging behavior that is essential to develop an appropriate feeding strategy for each specific situation (captive or wild). Utilization of faecal markers may allow us to fill this gap, accommodating animal welfare and intensive labour issues that are major limitations of traditional techniques. This study aimed to evaluate the potential of n-alkane markers (C25 to C33) to estimate diet composition, feed intake its digestibility on three captive maleBison bonasus fed on known amounts of straw, and a beeswax labelled concentrate feed. Feeds and faecal samples were taken daily during 10 days. Prior to calculations, faecal concentrations were corrected for incomplete faecal recovery (FR). Results indicated that 4–5 days were sufficient for these markers to reach a steady concentration in bison faeces. Accurate estimates of diet composition and feed intake were obtained not differing from known values. Results suggest that faecal recovery of n-alkanes in bison are incomplete and tend to increase with carbon-chain length. Apparent dry-matter digestibility (DMDap) estimates were affected by the n-alkane (C27, C29,C31, and C33) used in the calculations. Estimates of DMDap obtained with application of FR corrections were 6.3% higher than those without correction. Results indicate that feeding a known amount of beeswax labelled supplement can be successfully used to estimate composition, feed intake, and its digestibility, requiring the application of n-alkane FR data.

Predicción del valor nutricional de sorgo para forraje mediante espectroscopia de reflectancia en el infrarrojo cercano (NIRS) y ecuaciones empíricas

In the present work it is studied the predictive ability of NIRS for the estimation of chemical composition (n=171) and organic matter digestibility (n=71) of whole plants forage sorghum and morphological components, being developed empirical equations based on chemical parameters to estimate the organic matter digestibility (OMD) values and compared the predictive ability of empirical models vs. NIRS equations. The predictive ability of NIRS models for estimating the OMD and chemical composition showed high reliability, according to the coefficient of determination in external validation (r²≥0.90), whilst the ratio of the standard deviation of the original data to standard error of external validation (RPD) values were higher than 3.0 for all parameters studied. Applying NIRS models to the prediction of OMD of whole plants and morphological components of forage sorghum led to the reduction in the standard error of external validation, in comparison of the best empirical model based on the chemical composition of samples (from ±3.9 to ±1.9%). It is concluded that the NIRS equations developed in the present work are valuable tools for the fast and accurate assessment of the nutritive value of the whole plant and components of forage sorghum.

202 An Update on in Vitro and in Situ Experimental Techniques for Approximation of Ruminal Fiber Degradation

Abstract Measures of the quantity of chemical components are used to make certain assumptions about forage or feed quality. However, additional ruminal degradation kinetic measures are necessary for modern nutrient requirement models and more accurate estimates of intake and digestibility. The extent and rate of ruminal degradation is most easily and inexpensively measured with in vitro and in situ experimental techniques. This presentation is a summary of updates to these techniques in the last thirty years. The Daisy Incubator by ANKOM Technology has been marketed for over twenty-five years. This product resulted in standardization of materials and methods used to measure in vitro true digestibility. The biological component of the technique, ruminal fluid, is still a variable component since it is influenced by fistulated animal diet and collection and transport procedures. Despite several calls through review papers over the last thirty years, the in situ experimental technique is not standardized and there remains variation among laboratories and experiments. Animal species, ingredients and quantity of animal diet, grind size of the test material, bag pore size, ratio of the sample: surface area of bag, replications, sample treatment prior to incubation and after removal, incubation method, microbial contamination, bag washing, and even laboratory balance weigh method contribute to the variation among in situ experiments. Once in situ data is obtained, it is typically fitted to a first order exponential model and parameters estimated without determining if the model is the best fit. Perhaps understanding the reasons that standardization of in situ methodology have failed would facilitate ways to make standardization possible. In the meantime, careful in situ experimental technique results in measures that are valuable inputs into models for nutrient requirements, intake, and digestibility and an increase in knowledge about ruminal degradation kinetics, despite the inability to compare results across laboratories or experiments.