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A published model designed to predict individual feed required for the observed shrunk BW and ADG of growing cattle when fed in groups was modified and evaluated to improve its accuracy. This model is needed to accurately bill feed and compute cost of gain in marketing programs based on individual animal management. Because of its importance in predicting energy required for growth, a database of 401 steers was used to develop an equation to predict percentage of empty-body fat (EBF) from carcass measurements (12th rib fat thickness, hot carcass weight, USDA quality grade, and longissimus muscle area), which accounted for 61% of the variation in EBF with no bias (P [is greater than] 0.1). When tested with an independent data set of 951 steers, the equation accounted for 51% of the variation with 1% proportional bias. The large variation in the carcass measurements at a particular EBF observed in this study indicates further improvement is limited by the inability of carcass measurements to account for variation in fat distribution in the various carcass components. Because of its importance in setting the target end point, a database of 1,355 steers and heifers was used to determine the relationship between EBF and USDA quality grade. These data indicate growing and finishing cattle reach Select and low-Choice quality grades at an EBF of 26.15 [plus or minus] 0.19 and 28.61 [plus or minus] 0.20%, respectively (P [is less than] 0.05). A data set of 228 steers from different breeds from two serial slaughter studies indicated 14.26 [plus or minus] 1.52 kg of empty BW change are required to increase EBF one percentage unit for cattle fed high-energy diets; this adjustment is needed to adjust final shrunk BW to the target EBF end point. The model to predict DM required with modifications developed in this study was evaluated with data from 365 individually fed cattle and it accounted for 74% of the variation in observed DM consumed with no bias (P [is greater than] 0.1). When the revised model was applied to a commercial feedlot data set containing 12,105 steers and heifers, the total observed DM consumed was predicted with a bias of less than 1%. The model presented in this study accounts for differences known to affect animal requirements (breed type, BW and ADG, and weight at the target EBF end point) and can be used to fairly allocate feed to individuals fed in a group under commercial feedlot conditions. Key Words: Carcass Composition, Cattle, Feed Intake, Feedlots, Mathematical Models, Nutrient Requirements

The beneficial effects of forages containing condensed tannins (CTs) on ruminants are well documented, but the chemical features of CT that yield benefits have not been defined. Some evaluations of limited numbers of highly purified compounds have resulted in positive correlations between CT molecular weight (MW) and biological activity, while others have failed to show a correlation. The objectives of this study were to determine if MW of CT could predict biological activity relative to protein precipitability. MW of condensed tannin, proteinprecipitable phenolics (PPP), and the amount of protein bound (PB) were determined for nine species of warmseason perennial legumes. There was no correlation between PPP or PB and MW (R² 0.11 and R² 0.02, respectively). However, CT concentration did correlate with PPP and PB (R² 0.81 and R² 0.69, respectively). It was concluded that CT MW does not explain the variation in protein precipitation by CT from the forage legumes surveyed. [ABSTRACT FROM AUTHOR]

• Dried distillers grains in finishing diets reduced organic matter digestibility. • Dried distillers grains in finishing diets reduced total digestible nutrients intake. • Higher nitrogen intake increased its excretion through feces and urine. • Increased intake of metabolizable protein did not increase retained nitrogen. This study aimed to evaluate the effect of including levels of low-fat dried distillers grains without soluble (DDG) in high-concentrate diets on intake and digestibility. Four rumen-cannulated Nellore cattle received four dietary treatments in a 4×4 Latin square experimental design. Treatments included diets without DDG (D0) and varying inclusion levels of DDG at 150 g/kg (D150), 300 g/kg (D300), and 450 g/kg (D450). Four periods of total feces and urine collection were performed to estimate nutrient intake and digestibility and estimate nitrogen balance. Collections of omasum digesta were used to estimate ruminal degradability. The ruminal emptying technique was performed to estimate the ruminal rates of ingestion, passage, and digestion (kd). The inclusion of DDG reduced the intake of total digestible nutrients (TDN) (P < 0.01), dry matter (DM) (P = 0.02), organic matter (OM) (P = 0.02), non-fiber carbohydrates (NFC) (P < 0.01) and ether extract (EE) (P = 0.06). The intake of neutral detergent fiber (NDF) increased linearly (P < 0.01), whereas CP had a quadratic pattern (P = 0.02). The total digestibility in kg/d of DM (P < 0.01), OM (P < 0.01), NFC (P < 0.01) and EE (P = 0.02) decreased linearly. The total digestibility in kg/d of the NDF increased linearly (P < 0.01) and the CP had a quadratic pattern (P = 0.01). The kd of DM (P = 0.01), OM (P < 0.01) decreased linearly and NDF increased linearly (P < 0.01). The amount of N retained did not change (P = 0.72), but the intake of metabolizable protein increased (P = 0.03). Therefore, the inclusion of low-fat DDG in finishing diets reduces TDN intake and reduces the digestibility of almost all nutrients. [ABSTRACT FROM AUTHOR]

The original Cornell Net Carbohydrate and Protein System (CNCPS) model, which was developed in 1992 and revised in 2004, included a rumen submodel with a set of equations that were algebraically programmed in a spreadsheet to predict bacterial N flow to the caudal tract of cattle. In this study, we propose a modification to the original CNCPS rumen submodel based on mathematical concepts that simulate the flow paths of solids and liquid in the rumen, which are known to be essential factors affecting rumen fermentation and microbial growth. This modification allows the quantification of the impact of aging mechanisms on the availability of both soluble and insoluble substrates for microbial growth in the rumen. Additionally, a correction has been proposed on peptide uptake by rumen bacteria. Literature data were used to evaluate the model adequacy of CNCPS versions 1992 and 2004, along with the proposed model, to determine their ability to predict bacterial N flow. The proposed model more accurately predicted the variable of interest, but there was an overall underprediction bias. Despite the rightful critics of the ability of mechanistic models to predict microbial crude protein flow from the rumen, the 1992 and 2004 versions of the CNCPS and the proposed modifications implemented within the CNCPS framework led to predictions that agreed with observational data at a discordance rate of 0.05, tolerance probabilities <0.001 for versions 1992 and 2004, and a tolerance probability equal to 0.13 for the proposed model given a sample size n = 39. Therefore, the proposed modifications might improve the ability of CNCPS-based models to predict the bacterial N flow from the rumen, thereby resulting in improved predictive performance compared to the original CNCPS model. Thus, it seems that models built on time-dependent kinetics of food particles and fluid are more fitting than time-independent ones to predict bacterial N flow to the caudal tract. • The original CNCPS framework was modified to predict microbial growth in the rumen. • The proposed modifications accounted for time-dependent kinetic aspects in the rumen. • Bacterial N flow predictions with CNCPS-1992, −2004, and a modified model were compared. • The modified model was more accurate and precise than the CNCPS-1992 and −2004 versions. [ABSTRACT FROM AUTHOR]

• Inclusion of DDG in finishing diets reduces the rate of dry matter degradation. • It is possible to estimate in vivo digestibility using in situ incubation method. • DDG increases in situ incubation time to estimate in vivo dry matter digestibility. • Literature data about in situ incubation time are not suitable for diets with DDG. This study aimed to evaluate ruminal in situ degradation of diets containing different levels of dried distillers grains (DDG) replacing soybean meal, urea and corn and the effect of these diets on in situ ruminal degradation of DDG, and to propose alternative methods to estimate in vivo digestibility of diets. Four rumen-cannulated Nellore bulls were used in a 4 × 4 Latin square design, for both in situ incubation and in vivo digestibility. We evaluated the following treatments: diet without DDG (D0) or containing 150 (D150), 300 (D300), or 450 g/kg (D450) of inclusion. For in situ evaluation, DDG was incubated in all animals, and diets only in those fed with the same diet that would be incubated. To estimate in vivo digestibility, three days of total feces collection were performed in each period. Data was analysed in PROC MIXED, PROC NLIN and PROC REG of SAS (version 9.4, SAS Institute Inc., Cary, NC, USA). There was no effect of diet on the in situ degradation parameters of the DDG (P > 0.05). However, for the diets, the readily soluble fraction (parameter " a ") (P < 0.01), and the rate constant for degradation (parameter kd) of the potentially degradable fraction in the rumen (parameter " b") (P = 0.05) of dry matter (DM), decreased linearly. On the other hand, the parameter "b" (P < 0.01) and kd rate (P = 0.03) of the neutral detergent fiber (NDF) of the diets increased linearly. The in situ incubation time to estimate the in vivo DM digestibility ranged from 27.2 h to 37.7 h. For the NDF, the time was 60-h for all diets. In addition, to estimate the in vivo digestibility of DM (DMD), and the residual NDF (RNDF) of diets, two equations were suggested for each one: DMD = 804.8 - 0.092 × level, and DMD = 658 + 0.468 × a ; RNDF = 393.9 - 0.138 × level, and RNDF = 874.3 - (0.602 × b) - (0.805 × I) + (1,662 × kd), where I = indigestible NDF. We conclude that the DDG can be incubated in animals fed diets without DDG or inclusion level up to 450 g/kg (DM basis), and that the inclusion of DDG in finishing diets reduced DM degradability, and it is possible to estimate in vivo digestibility using alternative methods. [ABSTRACT FROM AUTHOR]

• Oil source did not affect performance or blood and rumen variables. • The biosurfactant significantly improved average daily gain. • Treatments did not affect blood hematological and chemistry variables. • Rumen papillae area and mitotic cells decreased with the use of the biosurfactant. Diets enriched with oil and high-energy content for feedlot lambs are often used to improve animal performance. The uptake of energy lipids can be optimized with the addition of biosurfactants. This experiment evaluated the effects of two oil sources and the addition of a biosurfactant on the performance of lambs. The research also assessed biosurfactant effects on blood parameters, number of protozoa and short-chain fatty acids levels in ruminal digesta, and ruminal and duodenal papilla morphometry. For that purpose, four treatments were studied: soybean oil without a biosurfactant, soybean oil with a biosurfactant, sunflower oil without a biosurfactant, and sunflower oil with a biosurfactant. Common ingredients included in the diets were corn silage, a milled-corn-based concentrate, soybean meal, and minerals. Soy lysolecithin was the biosurfactant used. Each treatment consisted of ten 90-d old commercial lambs individually confined for 60 days. The animals were weighed every 14 days, and feed intake was monitored daily. The dry matter intake (DMI), average daily gain (ADG), food conversion ratio (FCR) and body condition were recorded. Blood was sampled for hematological and biochemical evaluation at the end of the feedlot period. After slaughtering, rumen digesta was collected to evaluate the number and population of protozoa and the production of short-chain fatty acids. For ruminal and duodenal papilla morphometry, the rumen and duodenum were sampled. The statistical design was 2 × 2 factorial, with two oil sources and the addition or not of biosurfactant, and the means were compared using Tukey's test (at 5% probability). There was no treatment effect on DMI, FCR, blood hematological, protozoan population, production of short-chain fatty acid in the rumen or duodenum morphometry. Lambs fed biosurfactant had higher ADG (P = 0.02). These animals also had reduced rumen papilla area and a mitotic cell index. The results show that the oil source did not affect the studied parameters, and the addition of the biosurfactant shows potential for use in lamb diets because it increases ADG. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the inclusion of physically effective fiber (peNDF) from sugarcane in feedlot diets containing whole corn grain on ingestive, digestive, and ruminal parameters. Five rumen-cannulated Nellore bulls (BW = 393 ± 9 kg) distributed in an incomplete 5 × 5 Latin square received diets containing 5% (D5), 15% (D15), 25% (D25), or 35% (D35) sugarcane. All diets included a mineral-protein supplement. Omasal digesta collection and fecal spot collection were carried out to estimate ruminal and total digestibility. The ruminal contents were emptied to calculate ingestion (ki), passage (kp), and digestion (kd) rates. The linear, quadratic, and cubic effects of including sugarcane (i.e., different peNDF contents) were evaluated using orthogonal contrasts. The intake of total digestible nutrients (TDN , P = 0.06), dry matter (DM , P = 0.03), and organic matter (OM , P = 0.03) showed a quadratic pattern, with the highest estimated values occurring between 6.14 and 10.2% of peNDF. Ruminal digestibility [%, (P = 0.01) and kg/d, (P = < 0.01)] and total digestibility (kg/d, P = 0.03) of OM, ki (P = < 0.01), kp (P = 0.01) and kd (P = < 0.01) rates of OM, ki (P = 0.07), kp (P = 0.01), and kd (P = 0.05) rates of neutral detergent fiber (NDF) and microbial crude protein synthesis (MPS) (P = < 0.01) were also maximized, with inclusion levels between 6.14 and 10.2% of peNDF, although the efficiency of MPS tended to increase linearly (P = 0.08). The total concentration of volatile fatty acids (VFA) decreased linearly (P = 0.03), while the rumen ammonia pool [concentration (mmol/L) x volume of rumen liquid (L)] increased linearly (P = < 0.01). Ruminal pH responded linearly with the addition of sugarcane to the diet. We conclude that feedlot animals might benefit from diets containing between 6.14 and 10.2% of peNDF when whole corn grain diets are used. • Levels of 6.14 to 10.2% peNDF in finishing diets improve TDN intake. • Inclusion of peNDF in whole corn diets improves ruminal pH and fibre digestion. • Improvement in intake and ruminal pH allow greater microbial synthesis. • Fibre content in the diet is directly related to microbial efficiency. [ABSTRACT FROM AUTHOR]