A biofloc system avoids the adverse effects of diets with suboptimal protein levels on zootechnical performance, intestinal histomorphometry, and protein metabolism of Nile tilapia juvenile fed Spirulina biomass (Arthrospira platensis) as an alternative protein source.

This study aimed to evaluate the effect of the biofloc technology (BFT) system and the replacement of fish meal with Spirulina biomass on productive performance, intestinal histomorphometry, plasma biochemistry, and oxidative stress of Nile tilapia juveniles (Oreochromis niloticus) fed suboptimal levels of protein. Two factors were evaluated: production systems (clear water × BFT) and replacement of fish meal with Spirulina (0, 33, 66 e 100%). The design was in a 2 × 4 randomized factorial scheme with four replications, and the fish were evaluated for 48 days. Four isoproteic (28% crude protein) diets were formulated with gross energy values close to 4300 kcal kg-1. Nile tilapia juveniles (0.23 ± 0.01 g) were distributed in 16 circular tanks (70 L) at seven fish/tank. The diets were formulated with protein levels approximately 20% below that required for the species and life stage. No interaction was observed between the factors evaluated (production systems × Spirulina inclusion). Rearing the fish in the BFT system avoided the adverse effects of diets with suboptimal protein levels on performance, intestinal histomorphometry, and protein metabolism. Lower values lower lipid peroxidation and higher antioxidant capacity were observed in fish reared in the BFT system, showing evidence of improvements in antioxidant responses and lower levels of physiological oxidative stress. Spirulina completely replaced fish meal in the diets of Nile tilapia juveniles without adverse effects on intestinal morphometry, protein metabolism, and antioxidant response. Replacing 66% of fish meal with Spirulina improved the productive performance, regardless of the rearing system.

Effects of Early Weaning on Performance and Carcass Quality of Nellore Young Bulls.

This study compared early weaning (EW; 150 days) with conventional weaning (CW; 240 days) in Nellore young bulls, evaluating performance, carcass characteristics, and meat quality. A total of 74 non-castrated male calves were divided into two weaning strategies: EW (n = 37) and CW (n = 37). During the growth phase, which lasted 454 ± 14 d for EW calves and 359 ± 16 d for CW calves, animals received a protein-energy supplement at a ratio of 5 g per kg of body weight while grazing Brachiaria brizantha cv. Marandu. The animals were managed for an 87d finishing phase in three collective feedlot pens, with a 3-week adaptation protocol, starting with corn silage to a concentrate ratio of 55:45 and reaching a ratio of 30:70 in the final diet. Body weight, average daily gain (ADG), dry matter intake (DMI), feed efficiency (FE), carcass characteristics, and meat quality were evaluated. The EW group was approximately 44 kg lighter than the CW at the time of conventional weaning (p < 0.001). However, this weight difference did not influence ADG, DMI, and FE in the finishing phase. No significant differences were observed in carcass characteristics such as yield percentage, loin area, subcutaneous fat thickness, and meat quality, except for the weight of primal cuts, which was greater in the CW group (p < 0.001). Thus, although calves weaned early are lighter throughout subsequent production phases than those weaned conventionally, performance, efficiency, carcass yield, and meat quality are not affected.

Morphological aspects of rumen papillae of lambs fed agro-industrial wastes.

Sheep meet production systems require roughage feed of good nutritional quality. However, the production of sorghum or corn silage, besides expensive, also depends on large cultivable areas and favorable weather conditions. Thus, agro-industrial residues have stood out as a feed alternative that contribute to the reduction of production costs and to the conservation of the environment. Fragments of the ruminal mucosa of 30 healthy lambs fed with agro-industrial residues and slaughtered with a final weight of 36 kg were analyzed by light and scanning electron microscopy. We observed that the coproducts grape residue and wet brewery residue affected the shape, dimensions, and cytoarchitecture of the rumen epithelium in contrast to traditional sorghum silage. The rumen papillae of lambs fed grape waste were larger, and their epithelium was thinner when compared to the papillae of lambs fed wet brewery waste and sorghum silage. It can be assumed that the increased mucosal surface area of the rumen contributed to greater weight gain and reduced time to slaughter. The use of a greater variety of agro-industrial residues as a substitute for traditional feedstuffs contributes to the increase in animal protein production in many countries, making the confinement of sheep more viable and sustainable.

Oxidative Stress and Antioxidant Defense in the Heart, Liver, and Kidney of Bat Species with Different Feeding Habits.

The aim of this study was to compare the oxidative metabolism of four neotropical bat species with different feeding habits and investigate the relationship between their feeding habits and oxidative status. In terms of oxidative damage, our findings revealed major differences among the four bat species. In particular, hematophagous bats had lower levels of oxidative damage in the heart but higher levels in the liver. Nectarivorous bats had lower levels of carbonyl groups in the kidneys compared to insectivorous and hematophagous bats. The activity of various antioxidant and non-antioxidant enzymes in the heart, liver, and kidney also showed significant differences among the bat species. H2O2 consumption was lower in the heart of hematophagous bats, while insectivorous bats exhibited the highest enzymatic activity in the kidney. SOD activity was lower in the heart of hematophagous bats and lower in nectarivorous bats in the liver. Fumarase activity was higher in the heart of frugivorous/insectivorous and lower in nectarivorous/hematophagous bats. GPx activity was higher in the heart of nectarivorous/insectivorous and higher in the kidney of insectivorous bats. GST activity was higher in the heart of nectarivorous and lower in hematophagous bats. The correlation analysis between oxidative markers and enzymatic/non-enzymatic antioxidants in the heart, liver, and kidney exhibited distinct patterns of correlations due to variations in antioxidant defense mechanisms and oxidative stress responses in different organs. The observed differences in oxidative damage, antioxidant enzyme activities, and correlations between oxidative markers and antioxidants highlight the adaptability and complexity of the antioxidant defense systems in these bats. Each organ appears to have specific demands and adaptations to cope with oxidative stress based on its physiological functions and exposure to dietary components. Our results have major significance for the conservation and management of bats, which are threatened species despite being crucial components of ecosystems. Our study's implications go beyond bat biology and offer valuable insights into comparative oxidative physiology.

New Perspective for Macroalgae-Based Animal Feeding in the Context of Challenging Sustainable Food Production.

Food production is facing challenging times due to the pandemic, and climate change. With production expected to double by 2050, there is a need for a new paradigm in sustainable animal feed supply. Seaweeds offer a highly valuable opportunity in this regard. Seaweeds are classified into three categories: brown (Phaeophyceae), red (Rhodophyceae), and green (Chlorophyceae). While they have traditionally been used in aquafeed, their demand in the feed market is growing, parallelly increasing according to the food demand. Additionally, seaweeds are being promoted for their nutritional benefits, which contribute to the health, growth, and performance of animals intended for human consumption. Moreover, seaweeds contain biologically active compounds such as polyunsaturated fatty acids, antioxidants (polyphenols), and pigments (chlorophylls and carotenoids), which possess beneficial properties, including antibacterial, antifungal, antiviral, antioxidant, and anti-inflammatory effects and act as prebiotics. This review offers a new perspective on the valorization of macroalgae biomass due to their nutritional profile and bioactive components, which have the potential to play a crucial role in animal growth and making possible new sources of healthy food ingredients.

Spray-Dried Animal Plasma as a Multifaceted Ingredient in Pet Food.

Plasma is a co-product from pork and beef obtained during the processing of animals for human consumption. The spray-drying process maintains the solubility of spray-dried animal plasma (SDAP) and its nutritional and functional properties, making this ingredient multifunctional in human and animal nutrition. In pet food, SDAP has been used in the production of wet foods (pates and chunks in gravy) as an emulsifying and binding agent, with the potential to replace hydrocolloids partially or totally, which have some negative implications for digestibility, fecal quality, and intestinal inflammation. From a nutritional point of view, SDAP has high digestibility and an amino acid profile compatible with high-quality ingredients, such as powdered eggs. Studies in companion animals, especially in cats, have shown that SDAP is an ingredient with high palatability. Despite the immunomodulatory, anti-inflammatory, prebiotic, and neuroprotective properties demonstrated in some animal models, there are still few publications demonstrating these effects in dogs and cats, which limits its use as a functional ingredient for these species. In this review, the potential use of SDAP in pet food, aspects related to the sustainability of this ingredient, and opportunities for studies in companion animals are discussed.

Can banana peel and sweet potato vines serve as efficient feed ingredients in diets for growing rabbits?

This study aimed to evaluate the use of banana peel (BP) and sweet potato vines (SPV) as a replacement for maize and alfalfa hay in diets for rabbits. Animal performance, economic analyses, meat composition, and color were evaluated for 49 days in a total 50 New Zealand White rabbits weaned at 35 days with an average body mass of ± 614 g. The animals were allotted, in a completely randomized design, having five dietary groups: control diet (0), without banana peels and sweet potato vines, or experimental diets, 25, 50, 75, and 100-with 25%, 50%, 75%, and 100% of banana peels and sweet potato vines in substitution to maize and alfalfa hay, respectively. The data were analyzed using ANOVA, while the means were compared by Tukey test (p < 0.05). The results indicate that daily feed intake, mass gain, and feed conversion were not statistically different from one another in the test groups compared to the control group treatment. In addition, the study shows no differences were observed in centesimal compositions and muscle color. The replacement of maize and alfalfa hay by the combination of BP and SPV resulted in reduction in feed costs, reaching 50% in the experimental diet with 100% of substitution the ingredients. It can be concluded, based on the results on animal performance, meat/color composition, and economic analyses, that BP and SPV may be used as a substitute for maize and alfalfa hay up to 100% in diets for growing rabbits.

Systematic review of the relationship between rumen acidosis and laminitis in cattle.

Laminitis is usually considered a consequence of digestive disorders that reduce ruminal pH. However, it is still not clear the direct relation between low ruminal pH provoked by excessive fast-digesting carbohydrate ingestion and laminitis, considering indicators, signs, and diagnosis aspects. This study aimed to clarify the association between different clinical presentations of laminitis with ruminal acidosis provoked by diet using the systematic review methodology. Three electronic databases were used: ISI Web of Science, PubMed, and Scopus. A total of 339 manuscripts were identified and only 16 were included. Manuscripts were published between 2000 and 2021 in 11 different peer-reviewed journals. Fifteen studies confirmed the occurrence of ruminal acidosis. The main indicators used were ruminal pH and clinical signs, such as anorexia, depression, discomfort and diarrhea. Two of the studies that administered oligofructose to induce acidosis and acute laminitis did not observe clinical signs of laminitis, using lameness score or hooves' sensitivity as an indicator. Various diagnostic methods were used to describe laminitis, like thermography, hoof biopsy, sensitivity test, and visual inspection. Although the variety of laminitis indicators used in the included studies, we evidence the existence of an association between diet (high level of fast-digesting carbohydrates), ruminal acidosis, and acute laminitis, mostly in the short-term acidosis' induction protocols, but the mechanism of action is still not clear.

Addition of chromium propionate in dog food: metabolic, immunological, and oxidative effects.

Chromium is a trace element essential in metabolising carbohydrates, lipids, and proteins and is involved in other biological functions. Therefore, this study determined whether chromium propionate supplementation in dogs improves haematologic, metabolic, immune/inflammatory, and antioxidant biomarkers. A commercial product (Labex® Chromium) containing 0.4% chromium was used at 500 g/ton of food, which provided an additional calculated amount of 2 mg of chromium per kg of food. We used ten beagles divided into two treatments: the chromium group (supplemented with 0.380 mg of chromium/dog/day; T-CHR) and the control group comprised dogs fed a basal diet (no chromium supplementation). The experiment included two periods of 28 days, with an interval of 15 days, i.e. the dogs in the control group in the first period were in the chromium group in the second period (all dogs underwent all treatments in a crossover design). Dogs supplemented with chromium had higher serum mineral levels on days 14 and 28 (P ≤ 0.001). The group in the chromium group showed significantly higher numbers of total leukocytes and lymphocytes and concentrations of total protein, globulin, thio-proteins, and catalase activity in blood than the control group. Serum urea concentrations and TBARS (lipid peroxidation) were lower (P ≤ 0.05) in the chromium group. Tendencies towards lower concentrations of reactive oxygen species were observed on day 28 in the T-CHR group (P = 0.10). Chromium supplementation increased the concentration of cytokines in serum (tumour necrosis factor-alpha [TNF-α], IFN-γ, and IL-10) and C-reactive protein (P ≤ 0.05). Dogs in the chromium group had higher gamma globulin concentrations than controls (P ≤ 0.001). These findings suggest that supplementation with chromium propionate (2 mg/kg) in food positivity modulates metabolic, antioxidant, and immune indicators in dogs.

Assessment of cecal microbiota modulation from piglet dietary supplementation with copper.

BACKGROUND: Swine production expanded in the last decades. Efforts have been made to improve meat production and to understand its relationship to pig gut microbiota. Copper (Cu) is a usual supplement to growth performance in animal production. Here, two performance studies were conducted to investigate the effects of three different sources of Cu on the microbiota of piglets. A total of 256 weaned piglets were randomly allocated into 4 treatments (10 replicates per treatment of 4 piglets per pen in Trial 1 and 8 replicates of 3 piglets per pen in Trial 2). Treatments included a control group (fed 10 mg/kg of Cu from CuSO4), a group fed at 160 mg/kg of Copper (II) sulfate (CuSO4) or tri-basic copper chloride (TBCC), and a group fed with Cu methionine hydroxy analogue chelated (Cu-MHAC) at 150, 80, and 50 mg/kg in Phases 1 (24-35 d), 2 (36-49 d), and 3 (50-70 d), respectively. At 70 d, the cecum luminal contents from one pig per pen were collected and polled for 16 S rRNA sequencing (V3/V4 regions). Parameters were analyzed in a completely randomized block design, in which each experiment was considered as a block. RESULTS: A total of 1337 Operational Taxonomic Units (OTUs) were identified. Dominance and Simpson ecological metrics were statistically different between control and treated groups (P < 0.10) showing that different Cu sources altered the gut microbiota composition with the proliferation of some bacteria that improve gut health. A high abundance of Prevotella was observed in all treatments while other genera were enriched and differentially modulated, according to the Cu source and dosage. The supplementation with Cu-MHAC can modify a group of bacteria involved in feed efficiency (FE) and short chain fatty acids (SCFA) production (Clostridium XIVa, Desulfovibrio, and Megasphera). These bacteria are also important players in the activation of ghrelin and growth hormones that were previously reported to correlate with Cu-MHAC supplementation. CONCLUSIONS: These results indicated that some genera seem to be directly affected by the Cu source offered to the animals. TBCC and Cu-MHAC (even in low doses) can promote healthy modifications in the gut bacterial composition, being a promising source of supplementation for piglets.

Dataset of feed bunk score images of cattle feedlot.

Bunk management is an important technique to minimize the variations in consumption in feedlot cattle and can be performed according to the South Dakota State University classification system. The use of information and communication technology (ICT) can help, in an objective way, in the interpretation of these measurements. We created a dataset with the objective to develop an automatic classification method of feed bunk score. In May, September and October on the 2021 and September on the 2022 we captured 1511 images in the morning on the farms, in natural lighting conditions with different angles and backgrounds and at a height of about 1.5 m from the bunk. After acquisition data, each image was classified according to its score classification. Additionally, we resized the images to 500 × 500 pixels, generated annotations files, and organized the dataset in folders. The images in this dataset can be used to train and validate a machine learning model to classify feed bunk images. This model can be used to develop an application to support bunk management.

Inclusion of Soybean Hulls (Glycine max) and Pupunha Peach Palm (Bactris gasipaes) Nanofibers in the Diet of Growing Rabbits: Effects on Zootechnical Performance and Intestinal Health.

This study evaluated the inclusion of nanofibers from soybean hulls and pupunha peach palm heart sheaths in the diet of growing rabbits. Twenty-four New Zealand White rabbits (male and female) were allocated in three experimental groups: control, fed a basal diet; Nanosoy, fed a diet containing 7% soybean-hull nanofibers; and Nanopupunha, fed a diet containing 7% pupunha palm heart-sheath nanofibers. The Nanosoy-group rabbits showed poorer final weight, daily feed intake, and daily weight gain than those in other groups. In the duodenum, villus height, total mucosal thickness, and villus width were higher in rabbits that received nanofiber-supplemented diets than in the controls. Higher villus density and wall thickness were observed in Nanopupunha-fed rabbits than in the controls. In the jejunum, although the crypt depth was higher in Nanosoy-fed rabbits, the villus height:crypt depth ratio was higher in the Nanopupunha-fed group. Nanosoy-fed animals exhibited increased count Enterobacteriaceae populations. Rabbits in both nanofiber-fed groups exhibited higher lactic-acid bacterial counts than those in the control-diet group. Therefore, although the inclusion of 7% Nanopupunha in the diet of rabbits did not alter the performance, it improved intestinal health and increased the lactic-acid bacterial count in the cecum of growing rabbits.

Sugarcane yeast with urea in replace of soybean meal in the diet of Murrah buffaloes does not cause metabolic, endocrine, and mineral disorders.

The aim of this study was to evaluate the effect of the replacement of soybean meal by increasing levels of sugarcane yeast and urea on the energy, enzymatic, protein, mineral, and hormonal profiles of buffalo heifers. Twenty Murrah heifers with an average body weight of 168 ± 2.0 kg and 1 year old were used in a completely randomized design. The treatments consisted of the replacement of soybean meal by increasing levels of sugarcane yeast and urea (0, 33, 67, and 100% dry matter). The animals were weighed at the beginning and end of the experimental period, and blood was collected on the final day. The replacement of soybean meal with sugarcane yeast influenced the performance and metabolic dynamics, with total weight gain (P = 0.005) and average daily gain (P = 0.015), presenting, for both variables, a quadratic effect. Considering the biochemical profile, there was an influence on the serum concentration of triglycerides (P = 0.055), the serum activities of aspartate aminotransferase, gamma-glutamyl transferase, and alkaline phosphatase (P < 0.05), in addition to the serum concentration of phosphorus (P = 0.007) and potassium (P = 0.053), which showed positive linear effects. The hormonal profile was not influenced by diets (P > 0.05). The elements copper, iron, and zinc were able to be quantified at all levels of sugarcane yeast and urea in the diets offered. The use of sugarcane yeast with urea promotes adequate metabolic response of buffalo heifers and can replace up to 100% of soybean meal in the concentrate.

Insect meal in poultry feed: a potential protein source

The present study aims to conduct a review on the potential use of insect meal as an alternative protein source in poultry feed, particularly to serve the rearing of free-range chickens. Insects are already part of the diet of birds in their natural habitat, and the availability of low-cost alternative foods with low environmental impact is essential for the development of the activity. The review comprehended studies that used meals consisting of silkworm (Bombyx mori) chrysalis, earthworm (Eisenia foetida), housefly (Musca domestica), black soldier fly (Hermetia illucens) and mealworm beetle (Tenebrio molitor) to replace plant-based protein sources. In general, insect meals have a high content of crude protein and ether extract, as well as an essential amino acid profile suitable for poultry feeding. The addition of insect meal in poultry feed normally shows good results as to growth performance and egg production, without causing a negative effect on carcass characteristics, meat sensory quality and egg quality, presenting itself as an alternative protein source with good prospects for replacing plant-based sources in poultry feed.(AU)

Effects of dietary fiber on performance and egg quality of laying hens at pre-laying and laying peak

This study aimed to evaluate the effects of different levels of dietary fiber on the performance and egg quality of laying hens at pre-laying and laying peak periods. The experimental period was divided into three periods: pre-laying (16 to 19 weeks of age), the start of laying (20 to 22 weeks of age) and laying peak (23 to 28 weeks of age). The experimental design was completely randomized with treatments constituted by five levels of fiber (2.00, 2.50, 3.00, 3.50, and 4.00%) in the diets, with five replicates (pens) of six birds each, totalling 180 hens. Performance and egg quality results were evaluated by polynomial regression at 5%. Fiber levels were not influenced (p >0.05) the first laying of the hens. However, levels above 2.50% of fiber provided worst (p <0.05) performance results, regardless of the period evaluated. Shortly after the start of laying, higher levels of fiber also caused a linear reduction (p <0.05) on egg weight and percentages of yolk and albumen, and an increase (p <0.05) on eggshells. Higher fiber levels caused a linear reduction (p <0.05) in the quality of the eggs, regardless of the period evaluated. It was concluded that the fiber levels did not influence the start period of the laying. Both pre-laying and start of the laying, levels above 2.5% of fiber caused a gradual worsening in performance. From the start of laying up to laying peak, levels above 2.5% of fiber also caused a gradual worsening in egg quality.(AU)

Does the mycotoxin ingestion by beef heifers on feedlot change the productive parameters?

In intensive beef cattle production systems, silage, corn, soy bean, and their coproducts are commonly used as feed. However, these ingredients are highly susceptible to contamination by fungi and mycotoxins, which may lead to immunological challenges and reduce animal production. The aim of the present study was to evaluate the effects of mycotoxin contamination of diet on intake, digestibility, and performance of heifers. Twenty non-pregnant (Nellore) heifers (age, >18 months; initial body weight, 348±30 kg) were used and randomly distributed in two treatments: (1) control (non-contaminated diet) and (2) zearalenone-contaminated diet (300 ppb). The diet comprised 70% corn silage and 30% concentrate. Individual dry matter intake and digestibility were estimated using external and internal markers. Heifer body weight was evaluated every week without fasting to calculate performance. The experimental design was completely randomized. Each animal was considered one experimental unit. Assumptions were tested for variance analyses (error normality, independence of errors, and homogeneity of variances) (p<0.05). There were no differences in dry matter intake (p=0.96) and digestibility (p=0.62). Performance (kg/day) did not vary as a function of zearalenone ingestion (p=0.68). Therefore, contamination of diet with 300 ppb zearalenone did not affect the intake, digestibility, and performance of feedlot-finished heifers.

Bioactives and Extracellular Enzymes Obtained from Fermented Macrofungi Cultivated in Cotton and Jatropha Seed Cakes.

This work focused on obtaining fermented oil cake (cotton or Jatropha) via macrofungi growth with potential characteristics for animal feed formulations, such as the presence of extracellular enzymes, bioactive (ergosterol and antioxidants), and detoxification of antinutritional compounds. The concentration of phorbol esters was reduced by four macrofungi in Jatropha seed cake (JSC) to non-toxic levels. At least two macrofungi efficiently degraded free gossypol in cottonseed cake (CSC). Fermentation with Coriolopsis sp. INPA1646 and Tyromyces sp. INPA1696 resulted in increased ergosterol concentrations, antioxidant activity reduction, and high activity of laccases and proteases. Bromatological analysis indicated high crude protein concentrations, with partial solubilization by fungal proteases. Fermented products from Coriolopsis sp. and Tyromyces sp. in JSC or CSC can be considered important biological inputs for monogastric and polygastric animal feed.

Effects of dietary electrolyte balance on performance, energy balance, and expression of genes related to acid-basic balance, absorption, and transport of nutrients in broilers.

The objective of this study was to evaluate the effect of dietary electrolyte balance (DEB) levels on performance characteristics (feed intake, FI; body weight gain, BWG; and feed efficiency, FE), energy balance (retained energy, RE; metabolizable energy ingested, MEI; heat production, HP; and energy retention efficiency, ERE), and the expression of genes related to acid-base balance, nutrient absorption, and transport in broilers from 1 to 21 days of age. A total of 245 male Cobb chickens were used in a completely randomized design with five DEB levels (110, 175, 240, 305, and 370 mEq/kg) and seven replicates of seven birds each. The inclusion of DEB levels influenced FE; 110 mEq/kg provided the better values for this characteristic both in the pre-initial phase and in the initial phase but was different only concerning 175 mEq/kg (1-7 days) and 240 mEq/kg (1-21 days). Birds that ingested diets with a level of 240 mEq/kg of DEB had a higher MEI and HP. This DEB level caused a lesser and greater expression of the SLC12A2 gene in the liver and the ATP1A1 gene in the intestine, respectively. On the other hand, the ATP1A1 gene was less expressed in the liver and kidney of broilers supplemented with 370 mEq/kg compared to a level of 110 mEq/kg. In general, a level of 110 mEq/kg DEB in the ration seems to be the most suitable for good performance, energy balance, and gene expression of broilers from 1 to 21 days of age.

Performance, Digestibility, Nitrogen Balance and Ingestive Behavior of Young Feedlot Bulls Supplemented with Palm Kernel Oil.

Vegetable oils can be used to increase energy density in diets; manipulate rumen fermentation; and alter the capacity for degradation, digestion and absorption of nutrients. Two experiments were conducted to evaluate palm kernel oil (PKO) in the diet of confined bulls with the inclusion of 0.0, 11.5, 23.0 and 34.6 g PKO/kg dry matter (DM). The first experiment evaluated nutrient intake, performance, ingestive behavior and carcass characteristics. In the second experiment, steers crossbred with a ruminal cannula were used to evaluate digestibility, nitrogen balance, microbial protein synthesis, short-chain fatty acid levels and protozoal counts. The results showed that the inclusion of PKO linearly reduced intake in kg/day (DM, crude protein-CP, neutral detergent fiber-NDFap, nonfibrous carbohydrates-NFC and total digestible nutrient-TDN) and digestibility (DM, NDFap and TDN). Ether extract intake increased quadratically with the predicted maximum intake of 15.4 g/kg DM. Regarding ingestive behavior, there was a quadratic increase in rumination time and a quadratic reduction in idle time. Nitrogen balance, nitrogen intake, nitrogen retention, microbial protein production, acetate, butyrate, acetate/propionate ratio and protozoa count showed linear decreases due to dietary PKO inclusion. Regarding the carcass characteristics, linear decreases were observed for the final weight, average daily gain, hot carcass weight, cold carcass weight, hot carcass yield, cold carcass yield, loin eye area and subcutaneous fat thickness. The inclusion of PKO at up to 34.6 g/kg DM in diets for confined bulls reduces intake, negatively affecting digestibility, performance and carcass characteristics.