Effect of processing on high-protein feedstuffs: A review

Apparent metabolizable energy and ileal amino acid digestibility of commercial soybean meals of different origins in broilers

We studied the chemical composition and the in vivo AMEn content and apparent (AID) and standardized (SID) ileal digestibility of CP and amino acids (AA) of 27 samples of soybean meals (SBM) from Argentina (ARG), Brazil (BRA), and USA, collected in Spain. On 88% DM basis, the BRA meals had more CP (46.9 vs. 46.0 and 45.9%; P < 0.05) and less sucrose (5.21 vs. 6.28 and 6.47%; P < 0.001) and stachyose (4.20 vs. 4.66 and 4.78%; P < 0.05) than the USA and ARG meals. Urease activity, protein dispersibility index, KOH protein solubility, and trypsin inhibitor activity values, were higher for the USA meals than for the South American meals (P < 0.05). In the in vivo trial, broilers received a common crumble diet from 0 to 16 d of age and then, their respective experimental diets (53% of a N-free diet and 47% of each of the 27 SBM tested) in mash form, for 5 d. The AMEn (2,334 vs. 2,282 and 2,277 kcal/kg; P = 0.062) and the AID (87.3 vs. 86.7 and 86.4%; P = 0.054) and SID (91.9 vs. 91.2 and 90.8%; P < 0.05) of the protein, were greater for the USA meals than for the ARG and BRA meals. In fact, the SID of Lys (93.5 vs. 93.0 and 92.1%; P < 0.001) and of the sum of Lys, Met, Thr, Trp, and Cys (91.4 vs. 91.0 and 90.2%; P < 0.05) were greater for the USA meals than for the ARG and BRA meals. In summary, the chemical composition, protein quality indicators, AMEn content, and ileal digestibility of the CP and the AA of the SBM, varied with the country of origin of the soybeans. In order to increase the accuracy of the feed formulation process, the composition and nutrient content of commercial batches of SBM, by country of origin should be controlled and periodically updated.

Cereal type and conditioning temperature altered protein and carbohydrate molecular structure, nutrient retention and performance in broilers fed pellet diets during starter and grower period

1. Effects of cereal type and conditioning temperature (CT) on protein and carbohydrate (CHO) molecular structures, nutrient retention, carcass and blood characteristics, caecal microbial population and growth criteria of broilers fed pellet diet were evaluated for a total period of 35 d.2. In total, 336-day-old Cobb 500 broiler chicks were randomly allotted into a 2 × 2 factorial arrangement with two different cereal types (maize or wheat) processed in two different temperatures (CT; 68°C or 90°C) with seven pen replicates containing 12 birds each.3. Chicks fed the maize-based diets significantly gained higher body weight (BW) and lower feed conversion ratio (FCR) in comparison to the chicks fed wheat-based diets during the whole grow-out period (p < 0.01). Overall, the highest BW and feed intake (FI) were seen in birds fed wheat-based diets conditioned at 68°C, but the lowest FCR was observed in maize-based diet conditioned at 90°C at 7, 14 and 21 d of age (p < 0.01). However, BW was higher and FCR lower in chicks fed maize-based diets conditioned at 90°C in the grower period (28 and 35 d; p < 0.01).4. The α-helix height was higher in wheat-based starter diets in comparison to the maize-based diet (p < 0.01). Ratio of amide I to II area and total CHO peak height were increased when diets were processed at 90°C in both maize and wheat-based starter diet (p < 0.05). Increasing the CT from 68°C to 90°C reduced CHO peak 1 and 2 height by 11.6% and 3.95%, respectively, in maize-based starter diets, while increasing the CT from 68°C to 90°C reduced CHO peak 1 and 2 height by 54.3% and 57.2%, respectively, in wheat-based starter diets. In the grower diets, increasing the CT from 68°C to 90°C increased CHO peak 1 by 23% in maize-based diets, but reduced CHO peak 1 by 24.5% in wheat-based diets.5. Calcium and phosphorous retention were highest in chicks fed wheat-based diets conditioned at 90°C and lowest in chicks fed maize-based diets conditioned at 90°C (p < 0.01). Salmonella, E. coli and coliforms in the caeca reduced significantly (p < 0.05) in chicks fed wheat-based diets conditioned at 90°C on d 11 and increased with the same diet at 35 d of age compared to the chicks fed maize-based diets conditioned at both 68°C and 90°C or wheat-based diets conditioned at 68°C.6. Conditioning the wheat-based diets at 68°C improved production responses without causing any adverse effects on protein and CHO molecular structures, however increasing the conditioning temperature to 90°C impaired performance due to alteration of protein and CHO molecular structures. In contrast, conditioning of the maize-based diets at 90°C had the opposite effect, and improved production performance compared to diets conditioned at 68°C.

Particle size and water content impact breakdown and starch digestibility of chickpea snacks during in vitro gastrointestinal digestion

Chickpeas are an agriculturally-important legume that are an excellent source of protein, fiber, and minerals. Developing chickpea-based snacks could provide consumers with snack products rich in protein and other nutrients. In this study, chickpea puree (high moisture content) and cracker (low moisture content) were each produced with large (7 mm sieve; coarse) or small (2 mm sieve; fine) particle size to investigate the impact of initial particle size and moisture content on particle breakdown, starch hydrolysis, and protein hydrolysis during in vitro digestion. All treatments underwent static in vitro oral digestion, dynamic gastric digestion in the Human Gastric Simulator (HGS), and static in vitro small intestinal digestion. The emptying rate from the HGS was significantly (p < 0.05) higher for fine puree compared to the other treatments, due to higher saturation ratio and smaller initial particle size. The reducing sugars and free amino groups released (representing starch and protein hydrolysis, respectively) from fine puree were higher than coarse puree, and fine cracker was higher than coarse cracker due to the influence of initial particle size. For example, after 360 min total in vitro digestion, the starch hydrolysis of the fine cracker (48.1 ± 3.2%) was significantly higher than (p < 0.05) the coarse cracker (36.3 ± 5.8%). Overall, crackers had higher protein and starch hydrolysis compared to puree in the liquid phase during digestion. The study showed that both the smaller initial particle size and drying significantly (p < 0.05) increased the particle size reduction during gastric digestion and starch and protein digestibility in chickpea-based snacks.

Feed Clusters According to In Situ and In Vitro Ruminal Crude Protein Degradation

Effective degradation (ED) of crude protein (CP) was estimated in vitro at 0.02, 0.05 and 0.08 h−1 assumed ruminal passage rates for a total of 40 feedstuffs, for which in situ ED was available and used as reference degradation values. For this, the Streptomyces griseus protease test was used. The differences between in vitro CP degradation and the in situ CP degradation values were lowest in legume grains and highest in cereal by-products and barley. The differences between in situ and in vitro ED were expressed using a degradation quotient (degQ), where degQ = (EDin vitro − EDin situ)/EDin situ. Among the tested feedstuffs, eight specific clusters were identified according to degQ for the assumed passage rates. The feedstuffs clustered in an unspecific way, i.e., feedstuffs of different nutrient composition, origin or treatment did not necessarily group together. Formaldehyde−treated rapeseed meal, soybean meal, wheat, a treated lupin, sunflower meal and barley could not be assigned to any of the clusters. Groupwise degradation (range of degQ for assumed passage rates are given in brackets) was detected in grass silages (−0.17, −0.11), cereal by-products together with sugar beet pulp (−0.47, −0.35) and partly in legume grains (−0.14, 0.14). The clustering probably based on different specific nutrient composition and matrix effects that influence the solubility of feed protein and limit the performance of the protease. The matrix can be affected by treatment (chemically, thermally or mechanically), changing the chemical and physical structure of the protein within the plant. The S. griseus protease test had reliable sensitivity to reflect differences between native feedstuffs and treatments (thermally or chemically) that were found in situ. The in situ results, however, are mostly underestimated. The clustering results do not allow a clear conclusion on the groupwise or feed-specific use of carbohydrate-degrading enzymes as pre- or co-inoculants as part of the S. griseus protease test and need to be tested for its potential to make this test more conform with in situ data.

Feeding thermally processed spray-dried egg whites, singly or in combination with 15-acetyldeoxynivalenol or peroxidized soybean oil on growth performance, digestibility, intestinal morphology, and oxidative status in nursery pigs

Two experiments (EXP) determined the susceptibility of spray-dried egg white (SDEW) to oxidation (heating at 100 °C for 72 h; thermally processed, TP) and whether feeding TP-SDEW, 15-acetyldeoxynivalenol (15-ADON), or peroxidized soybean oil (PSO), singularly or in combination, would affect pig performance, intestinal morphology, digestibility, and markers of oxidative stress in nursery pigs. In EXP 1, 32 pigs (7.14 kg body weight, BW) were placed individually into pens and fed diets containing either 12% SDEW, 6% TP-SDEW plus 6% SDEW, or 12% TP-SDEW. Performance was measured at the end of the 24-d feeding period with biological samples harvested following euthanasia. In EXP 2, 64 pigs (10.6 kg BW) were placed individually into pens and fed diets containing 7.5% soybean oil or PSO, 10% SDEW or TP-SDEW, and diets without or with 3 mg 15-ADON/kg diet in a 2 × 2 × 2 factorial arrangement. Performance was measured at the end of the 28-d feeding period with biological samples harvested following euthanasia. In EXP 1, dietary treatment did not affect pig performance, apparent ileal digestibility of amino acids (AAs), apparent total tract digestibility (ATTD) of gross energy (GE) or nitrogen (N), ileal crypt depth, or villi height:crypt depth ratio (P > 0.05). The effects of feeding TP-SDEW on protein damage in the plasma and liver (P < 0.05) were variable. In EXP 2, there were no three-way interactions and only one two-way interactions among dietary treatments on parameters evaluated. There was no effect of feeding TP-SDEW on ATTD of GE or N, intestinal morphology, or on oxidative markers in the plasma, liver, or ileum (P > 0.05). There was no effect of feeding diets containing added 15-ADON on ATTD of GE, ileal AA digestibility, intestinal morphology, oxidative markers in the plasma, liver, or ileum, or pig performance (P > 0.05). Feeding pigs diets containing PSO resulted in reduced ATTD of GE and N, plasma vitamin E concentration, and pig performance (P < 0.01) but did not affect intestinal morphology or oxidative markers in the liver or ileum (P > 0.05). In conclusion, it was difficult to induce protein oxidation in SDEW and when achieved there were limited effects on performance, digestibility, intestinal morphology, and oxidative status. Furthermore, singly adding 15-A-DON to a diet had no effect on the animal. At last, adding PSO reduces animal performance, but has limited effect on digestibility, intestinal morphology, and oxidative status in nursery pigs.

Fervidobacterium pennivorans subsp. keratinolyticus subsp. nov., a Novel Feather-Degrading Anaerobic Thermophile

Fervidobacterium pennivorans subsp. keratinolyticus subsp. nov. strain T was isolated from a terrestrial, high-altitude hot spring in Tajikistan. This strain is an obligate anaerobic rod and their cells occur singly, in pairs, or as short chains under the optimal growth conditions of a temperature of 65 °C and pH 6.5, with peptone, glucose, and galactose as the preferred substrates. The minimum generation time of this strain is 150 min. Strain T can efficiently degrade feather keratin at 65-75 °C; this unusual feature is also exhibited by a few other members of the Fervidobacterium genus. The total genome size of this bacterial strain is 2,002,515 base pairs, with a C + G content of 39.0%. The maximum digital DNA-DNA hybridization (dDDH) value of 76.9% was observed on comparing the genome of this strain with that of Fervidobacterium pennivorans type strain DSM9078. This study describes the physiological and genomic properties of strain T, with an emphasis on its keratinolytic power and differences from other members of the genus Fervidobacterium.

Fourier Transform Infrared Spectroscopy for Assessing Structural and Enzymatic Reactivity Changes Induced during Feather Hydrolysis

Chicken feathers are major byproducts of the livestock processing industry with high potential in the feed sector. In this study, we present a new approach using Fourier transform infrared (FTIR) spectroscopy to detect the structural changes of feather keratin and its availability for enzymatic hydrolysis (AEH) induced by the thermal pressure hydrolysis (TPH) process. Compared to time-consuming in vitro measurement techniques, the proposed method provides rapid information about the structural changes during TPH which enables quick adaptation of TPH conditions as the quality of the incoming feather changes. By analyzing the FTIR spectra of raw and processed feathers, it was found that AEH negatively relates to the β-sheet content (represented by two IR peaks centered at 1635 and 1689 cm^-1), while it positively relates to a new series of peaks centered around 1700 cm^-1 appearing after the TPH process. The proposed FTIR technique provides a reliable and rapid approach to determine the digestibility indicated by AEH of the processed feather and may be used in process control and optimization.

Barley, an Undervalued Cereal for Poultry Diets: Limitations and Opportunities

Simple Summary

With the ever-increasing demand for poultry products, the continuous supply of conventional cereal grains such as maize has become a challenge. Barley has been recognised as a potential alternative feed ingredient that can replace common cereal grains in poultry diets. However, due to several limitations such as the presence of various anti-nutritive factors and the variability in nutrient composition and quality, the use of barley in poultry diets remains comparatively low. The previous findings on the optimum use of barley in poultry diets are also inconsistent primarily due to differences in research methodologies. The importance of using accurate nutrient profiles for specific barley cultivars to formulate barley-based diets is emphasised in this review. Moreover, the need to adapt feed processing conditions suitable to different barley cultivars to increase the inclusion of barley in poultry diets is highlighted in this review.

Abstract

The supply of conventional cereal grains, especially of maize, will be a significant constraint to the future growth of the poultry industry. Various alternative feed ingredients are being tested to replace maize in poultry diets. Barley (Hordeum vulgare L.) is one such feed ingredient, the use of which remains limited in poultry diets due to its low metabolisable energy, presence of anti-nutritive, soluble non-starch polysaccharides and consequent inter-cultivar variability. Differences in research methodologies used in published studies have also contributed to the inconsistent findings, preventing a good understanding of the nutritional value of barley for poultry. The importance of using accurate nutrient profiles, specifically metabolisable energy and digestible amino acids, for specific barley cultivars to formulate barley-based diets is emphasised. Nutritionists should also pay close attention to feed processing conditions tailored to the specific barley cultivars to increase the barley inclusion in poultry diets.

Perspectives on Converting Keratin-Containing Wastes Into Biofertilizers for Sustainable Agriculture

Keratin-containing wastes become pollution to the environment if they are not treated properly. On the other hand, these wastes can be converted into value-added products applicable to many fields. Organic fertilizers and biofertilizers are important for sustainable agriculture by providing nutrients to enhance the growth speed of the plant and production. Keratin-containing wastes, therefore, will be an important resource to produce organic fertilizers. Many microorganisms exhibit capabilities to degrade keratins making them attractive to convert keratin-containing wastes into valuable products. In this review, the progress in microbial degradation of keratins is summarized. In addition, perspectives in converting keratin into bio- and organic fertilizers for agriculture are described. With proper treatment, feather wastes which are rich in keratin can be converted into high-value fertilizers to serve as nutrients for plants, reduce environmental pressure and improve the quality of the soil for sustainable agriculture.

Metabolizable energy and standardized ileal amino acid digestibility of full-fat soybeans for broilers are influenced by wet-heating, expansion temperature, and autoclaving time

The influence of wet-heating (WH) and expansion temperature (ET), and autoclaving time (AT) on the nitrogen-corrected apparent metabolizable energy (AME_n) and standardized ileal digestibility (SID) of AA in full-fat soybeans (FFSB) for broilers was examined in 2 experiments. The AME_n and SID AA of FFSB were determined by the difference and direct methods, respectively. In Experiment 1, raw FFSB (K0) were either treated by WH at 80°C for 1 min and expanded at 115°C (K1-115) or 125°C (K1-125), WH at 100°C for 6 min and expanded at 115°C (K2-115) or 125°C (K2-125), or WH at 100°C for 16 min and expanded at 115°C (K3-115) or 125°C (K3-125). Wet-heating and ET significantly (P < 0.001) increased the AME_n in FFSB. Among heat-treated FFSB, K1-115 and K1-125 resulted in the lowest and highest AME_n values, respectively, with all samples wet-heated at 100°C being intermediate. The K3-125 had AME_n values similar (P > 0.05) to K1-125. Among heat-treated FFSB, the highest average SID AA was recorded for K3-125. In Experiment 2, K3-125 from experiment 1 was divided into 9 batches and autoclaved at 110°C for 15 (Z1), 30 (Z2), 45 (Z3), 60 (Z4), 120 (Z5), 180 (Z6), 240 (Z7), 300 (Z8), and 360 (Z9) min. A quadratic (P < 0.01) pattern was observed for the effects of AT on AME_n. The AME_n was unaffected until 300 min AT and then declined at 360 min. The AT quadratically (P < 0.001) affected the average SID AA where the SID increased from K3-125 to Z1, plateaued to Z5, and then declined to Z9. In conclusion, the results demonstrated that WH at 100°C for 16 min followed by expansion at 125°C as the most optimal wet-heating and expansion processing, associated with the highest SID AA. Autoclaving at 110°C for 30 min enhanced energy utilization and AA digestibility in FFSB, suggesting that further advantages may be achieved by short-time autoclaving of previously wet-heated and expanded FFSB samples.

Bioconversion of Keratin Wastes Using Keratinolytic Microorganisms to Generate Value-Added Products

The management of keratinous wastes generated from different industries is becoming a major concern across the world. In each year, more than a billion tons of keratin waste is released into the environment. Despite some trials that have been performed and utilize this waste into valuable products, still a huge amount of keratin waste from different sources is a less explored biomaterial for making valuable products. This indicates that the huge amount of keratin waste is neither disposed properly nor converted into usable products rather thrown away to the environment that causes environmental pollution. Due to the introduction of this waste associated with different pathogenic organisms into soil and water bodies, human beings and other small and large animals are affected by different diseases. Therefore, there is a need for modern and ecofriendly approaches to dispose and convert this waste into usable products. Hence, the objective of this review is to give a concise overview regarding the degradation of keratin waste by biological approaches using keratinase producing microorganisms. The review also focuses on the practical use of keratinases and the economical importance of bioconverted products of keratinous wastes for different applications. Various researches have been studied about the source, disposal mechanisms, techniques of hydrolysis, potential use, and physical and chemical properties of keratin wastes. However, there is negligible information with regard to the use of keratin wastes as media supplements for the growth of keratinolytic microorganisms and silver retrieval from photographic and used X-ray films. Hence, this review differs from other similar reviews in the literature in that it discusses these neglected concerns.

Interaction of Soybean Varieties and Heat Treatments and Its Effect on Growth Performance and Nutrient Digestibility in Broiler Chickens

Simple Summary

Soybeans are the major source of protein in today´s livestock diets. However, European soybean imports are under criticism because of environmental issues. Therefore, production of European soybeans is expected to grow. To ensure optimal feeding properties, soybeans require a heating process to eliminate intrinsic compounds interfering negatively with the animal’s digestive tract. A heating process might have different effects on different soybean varieties. Therefore, two different soybean varieties were treated at two different heat intensities in the present study—110 °C and 120 °C. The results showed, that while both heat intensities had a sufficient deactivating effect in one variety, the other variety was not treated sufficiently at 110 °C. Insufficient heat treatment was expressed in lower weight gains and lower feed intake. No negative effect of heat treatment at 120 °C was observed for growth performance, but amino acid digestibility was reduced. The present study shows that the optimal processing conditions can vary for different soybean varieties, which has to be considered especially when handling small and heterogeneous soybean batches.

Abstract

As production of European soybeans is expected to grow, optimal processing conditions need to be ensured for small and heterogeneous batches of soybeans. The effect of different soybean varieties, as well as heat treatments, on the growth performance and nutrient digestibility in broiler chickens was investigated. Two varieties, regarded as heat stable and heat labile after preliminary experiments, were partially de-oiled and thermally processed at 110 °C for 20 min and 120 °C for 20 min. The resulting soybean cakes were integrated into a mash diet and subjected to a 36-day long feeding experiment. A total of 336 one-day-old broiler chickens were divided into 24 pens, resulting in 6 replicates per treatment. With application of the 110 °C treatment, analysis of soybean cakes showed that the commonly required reduction in trypsin inhibitor activity (TIA) was only reached with one soybean variety. The higher processing temperature of 120 °C ensured sufficient TIA reductions in both soybean varieties. Elevated TIA concentrations resulted in decreased growth performances (p < 0.05) of the chickens, whereas no negative effect from overheating on growth performance appeared. Total-tract nitrogen retention (p < 0.05) and pre-caecal digestibility of several amino acids (p < 0.10) decreased with higher processing temperatures but had no negative effects on growth performance. In conclusion, the results indicate that processing conditions adjusted to the different varieties are essential to ensure optimal product quality.

Growth, Chemical Composition, Histology and Antioxidant Genes of Atlantic Salmon (Salmo salar) Fed Whole or Pre-Processed Nannochloropsis oceanica and Tetraselmis sp

New sustainable feed ingredients are a necessity for the salmon aquaculture industry. In this study, we examined the effect of pre-extrusion processing of two microalgae, Nannochloropsis oceanica and Tetraselmis sp., on the growth, fatty acid content in the flesh and health of Atlantic salmon. The fish were fed one of the following five diets for nine weeks: (1) CO: a fish meal-based control (basal) diet, (2) NU: a Nannochloropsis diet, (3) NE: a pre-extruded Nannochloropsis diet, (4) TU: a Tetraselmis diet, and (5) TE: a pre-extruded Tetraselmis diet. The algae-incorporated diets contained 30% of the respective microalgae. Our results showed that the best growth performance was achieved by the CO diet, followed by the NE diets. Feeding of unprocessed Nannochloropsis and Tetraselmis resulted in a significant reduction in enterocyte vacuolization compared to the CO feeding. A significant effect of processing was noted in the fillet fatty acid content, the intestine and liver structure and the expression of selected genes in the liver. The expression of antioxidant genes in both the liver and intestine, and the accumulation of different fatty acids in the fillet and liver of the extruded algae-fed groups, warrants further investigation. In conclusion, based on the short-term study, 30% inclusion of the microalgae Nannochloropsis oceanica and Tetraselmis sp. can be considered in Atlantic salmon feeds.

Can we effectively manage parasites, prions, and pathogens in the global feed industry to achieve One Health?

Prions and certain endoparasites, bacteria, and viruses are internationally recognized as types of disease-causing biological agents that can be transmitted from contaminated feed to animals. Historically, foodborne biological hazards such as prions (transmissible spongiform encephalopathy), endoparasites (Trichinella spiralis, Toxoplasma gondii), and pathogenic bacteria (Salmonella spp., Listeria monocytogenes, Escherichia coli O157, Clostridium spp., and Campylobacter spp.) were major food safety concerns from feeding uncooked or improperly heated animal-derived food waste and by-products. However, implementation of validated thermal processing conditions along with verifiable quality control procedures has been effective in enabling safe use of these feed materials in animal diets. More recently, the occurrence of global Porcine Epidemic Diarrhea Virus and African Swine Fever Virus epidemics, dependence on international feed ingredient supply chains, and the discovery that these viruses can survive in some feed ingredient matrices under environmental conditions of trans-oceanic shipments has created an urgent need to develop and implement rigorous biosecurity protocols that prevent and control animal viruses in feed ingredients. Implementation of verifiable risk-based preventive controls, traceability systems from origin to destination, and effective mitigation procedures is essential to minimize these food security, safety, and sustainability threats. Creating a new biosafety and biosecurity framework will enable convergence of the diverging One Health components involving low environmental impact and functional feed ingredients that are perceived as having elevated biosafety risks when used in animal feeds.

Structure, Application, and Biochemistry of Microbial Keratinases

Keratinases belong to a class of proteases that are able to degrade keratins into amino acids. Microbial keratinases play important roles in turning keratin-containing wastes into value-added products by participating in the degradation of keratin. Keratin is found in human and animal hard tissues, and its complicated structures make it resistant to degradation by common proteases. Although breaking disulfide bonds are involved in keratin degradation, keratinase is responsible for the cleavage of peptides, making it attractive in pharmaceutical and feather industries. Keratinase can serve as an important tool to convert keratin-rich wastes such as feathers from poultry industry into diverse products applicable to many fields. Despite of some progress made in isolating keratinase-producing microorganisms, structural studies of keratinases, and biochemical characterization of these enzymes, effort is still required to expand the biotechnological application of keratinase in diverse fields by identifying more keratinases, understanding the mechanism of action and constructing more active enzymes through molecular biology and protein engineering. Herein, this review covers structures, applications, biochemistry of microbial keratinases, and strategies to improve its efficiency in keratin degradation.

Sustainable enzymatic technologies in waste animal fat and protein management

Waste animal fats and proteins (WAFP) are rich in various animal by-products from food industries. On one hand, increasing production of huge amounts of WAFP brings a great challenge to their appropriate disposal, and raises severe risks to environment and life health. On the other hand, the high fat and protein contents in these animal wastes are valuable resources which can be reutilized in an eco-friendly and renewable way. Sustainable enzymatic technologies are promising methods for WAFP management. This review discussed the application of various enzymes in the conversion of WSFP to value-added biodiesel and bioactivate hydrolysates. New biotechnologies to discover novel enzymes with robust properties were proposed as well. This paper also presented the bio-utilization strategy of animal fat and protein wastes as alternative nutrient media for microorganism growth activities to yield important industrial enzymes cost-effectively.

High steam-conditioning temperature during the pelleting process impairs growth performance and nutrient utilization in broiler starters fed barley-based diets, regardless of carbohydrase supplementation

The influence of supplemental carbohydrase (Carb) and conditioning temperature (CT) on growth performance, nutrient utilization and intestinal morphometry of broilers (d 1-21) fed barley-based diets was examined in a 2 × 3 factorial arrangement, evaluating 2 levels of Carb (0 and 150 g/tonne of feed) and three CT (60, 74, and 88°C). A total of 288, 1-day-old male broilers (8 birds/cage; 6 cages/treatment) were used. The activities of endo-1,4-β- glucanase, endo-1,3 (4)-β-glucanase and endo-1,4-β-xylanase in the Carb were 800 BGU/g, 700 BGU/g and 2,700 XU/g, respectively. On d 21, ileal digesta was collected for the determination of nutrient digestibility. There was no significant interaction between Carb and CT for any tested parameter. Supplemental Carb, regardless of CT, increased weight gain (WG; P < 0.05) and reduced feed per gain (F/G; P < 0.001) by 30 g/bird and 6.5 points, respectively. Increasing CT to 88°C reduced (P < 0.05) WG, but increased (P < 0.05) F/G compared to the diets conditioned at 60° and 74°C. Regardless of CT, Carb enhanced (P < 0.05) the digestibility of starch and AMEn by 1.15% and 32 kcal/kg, respectively. Compared to the diets conditioned at 60° and 74°C, CT at 88°C reduced (P < 0.05) digestibility of dry matter, nitrogen, phosphorus, gross energy, and AMEn. Birds fed diets conditioned at 88°C showed lower (P < 0.05) starch digestibility compared to those fed diets conditioned at 60°C. Conditioning at 88°C increased (P < 0.05) jejunal digesta viscosity by 10.2% compared to diets conditioned at 60° and 74°C. Overall, Carb supplementation improved WG, F/G, starch digestibility and AMEn in broilers fed barley-based diets, irrespective of CT applied. Conditioning barley-based diets at 88°C impaired the ability of birds to utilize nitrogen, starch, phosphorus and energy, and consequently deteriorated WG and F/G. The lack of significant interactions between Carb and CT indicated that negative impacts caused by high CT on bird performance and nutrient utilization occurred regardless of Carb enzyme supplementation. Supplemental Carb per se could not remedy the adverse effects of high CT.

Standardized ileal amino acid digestibility of protein sources for broiler chickens is influenced by the feed form

The aim of present study was to determine the influence of the feed form (FF) on standardized ileal digestibility (SID) of nitrogen (N) and amino acids (AA) in 3 protein sources (PS) for broiler chickens. Six diets were tested in a 3 × 2 factorial arrangement of treatments involving 3 PS (meat and bone meal [MBM], soybean meal [SBM], and canola meal [CM]) in mash and pelleted forms. The basal endogenous N and AA losses were determined by offering a N-free diet in the mash form. From day 1 to 18, the birds were offered a broiler starter diet. The diets and the N-free diet were randomly assigned to 6 replicate cages (8 birds per cage) and fed from day 19 to 23. The ileal digesta were collected on day 23. The SID of N was higher (P < 0.05) in SBM followed by MBM and CM. The average SID of AA in SBM and MBM were similar (P > 0.05), and greater (P < 0.05) than that in CM. The FF had no influence (P > 0.05) on the SID of indispensable AA, the only exception being His, which was reduced (P < 0.05) by pelleting. Pelleting, however, resulted in reduction (P < 0.001) in the SID of all dispensable AA and average of AA. The AA most affected by pelleting was Cys, with a 15.4% decrease in the SID. The standardized ileal digestible contents of protein and the average of indispensable AA and dispensable AA were higher in MBM than in SBM, with CM being the lowest. Pelleting decreased (P < 0.05) the digestible protein and total digestible AA contents. These findings reveal that the FF has a substantial impact on AA digestibility estimates of feed ingredients and it must be considered in AA digestibility assays of ingredients with high protein and AA contents.

Challenges and Opportunities in Identifying and Characterising Keratinases for Value-Added Peptide Production

Keratins are important structural proteins produced by mammals, birds and reptiles. Keratins usually act as a protective barrier or a mechanical support. Millions of tonnes of keratin wastes and low value co-products are generated every year in the poultry, meat processing, leather and wool industries. Keratinases are proteases able to breakdown keratin providing a unique opportunity of hydrolysing keratin materials like mammalian hair, wool and feathers under mild conditions. These mild conditions ameliorate the problem of unwanted amino acid modification that usually occurs with thermochemical alternatives. Keratinase hydrolysis addresses the waste problem by producing valuable peptide mixes. Identifying keratinases is an inherent problem associated with the search for new enzymes due to the challenge of predicting protease substrate specificity. Here, we present a comprehensive review of twenty sequenced peptidases with keratinolytic activity from the serine protease and metalloprotease families. The review compares their biochemical activities and highlights the difficulties associated with the interpretation of these data. Potential applications of keratinases and keratin hydrolysates generated with these enzymes are also discussed. The review concludes with a critical discussion of the need for standardized assays and increased number of sequenced keratinases, which would allow a meaningful comparison of the biochemical traits, phylogeny and keratinase sequences. This deeper understanding would facilitate the search of the vast peptidase family sequence space for novel keratinases with industrial potential.

Progress in Microbial Degradation of Feather Waste

Feathers are a major by-product of the poultry industry. They are mainly composed of keratins which have wide applications in different fields. Due to the increasing production of feathers from poultry industries, the untreated feathers could become pollutants because of their resistance to protease degradation. Feathers are rich in amino acids, which makes them a valuable source for fertilizer and animal feeds. Numerous bacteria and fungi exhibited capabilities to degrade chicken feathers by secreting enzymes such as keratinases, and accumulated evidence shows that feather-containing wastes can be converted into value-added products. This review summarizes recent progress in microbial degradation of feathers, structures of keratinases, feather application, and microorganisms that are able to secrete keratinase. In addition, the enzymes critical for keratin degradation and their mechanism of action are discussed. We also proposed the strategy that can be utilized for feather degradation. Based on the accumulated studies, microbial degradation of feathers has great potential to convert them into various products such as biofertilizer and animal feeds.

Production of feather oligopeptides by a newly isolated bacterium Pseudomonas otitis H11

Oligopeptides usually have high nutritive value and multiple physiological functions. To achieve the highly efficient utilization of feather waste, a feather-degrading bacterium, Pseudomonas otitis, was isolated and used for production of feather oligopeptides. The production potential and characteristics of the produced oligopeptides by H11 were also investigated. The results demonstrated that the optimal initial pH, temperature, fermentation time, and sterilization conditions were 11, 40°C, 24 h, and 121°C for 20 min, respectively. After 24 h of fermentation under the optimal conditions, the feathers were almost completely degraded. Correspondingly, 35.37% oligopeptides (accounting for 69.70% of the total soluble peptides) and varieties of essential amino acids (valine, isoleucine, leucine, phenylalanine, methionine, threonine, and lysine) were obtained. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis indicated that the produced oligopeptides were mainly low molecular weight (below 1600 Da) and rich in branched-chain amino acids. Also, the oligopeptide-enriched hydrolysate displayed good antioxidant activity with 83% 2,2-diphenyl-1-picrylhydrazyl (DPPH•) scavenging ability and 53% superoxide anion (O2•-) scavenging activity. This study demonstrated that the hydrolysate of feathers was abundant in oligopeptide fractions with 5-10amino acid residues and possessed good antioxidant activity. This oligopeptide-enriched hydrolysate could be used as a functional feed supplement and as a source for functional oligopeptide extraction.

Processing techniques of selected oilseed by-products of potential use in animal feed: Effects on proximate nutrient composition, amino acid profile and antinutrients

The effects of processing by autoclaving (AC), soaking (SK), short-term fermentation (S-TF, 4 d) and long-term fermentation (L-TF, 14 d) on the nutritional composition, amino acid profile and some antinutrients were determined for cottonseed meal (CSM), groundnut meal (GNM) and groundnut husk (GH) in this study. After processing, crude protein content improved by 11% after L-TF, and crude lipid content 25% after SK for CSM; crude protein content improved by 27% after S-TF and L-TF, and crude lipid content 13% after SK for GNM. Soaking and fermentation were shown to significantly increase essential amino acid contents by 44% (SK, methionine) in CSM and 46% in GNM (L-TF, histidine). Phosphorus content was reduced by 59% in CSM and 57% in GNM by L-TF. All processing techniques, with the exception of AC, reduced phytic acid and gossypol contents in CSM and GNM. It was concluded that SK and fermentation were simple, cost-effective, and efficient ways to improve the nutritional value of the selected oilseed by-products.

Screening lactic acid bacteria to manufacture two-stage fermented feed and pelleting to investigate the feeding effect on broilers

Bacillus subtilis var. natto N21 (BS) and different lactic acid bacteria were applied to produce two-stage fermented feeds. Broilers were fed these feeds to select the best fermented feed. The selected fermented feed was pelleted and investigated for its effects on growth performance, carcass traits, intestinal microflora, serum biochemical constituents, and apparent ileal nutrient digestibility. Trial 1 involved three hundred thirty-six 1-d-old broilers with equal numbers of each sex, randomly assigned into control, BS + Bacillus coagulans L12 (BBC), BS + Lactobacillus casei (BLC), BS + Lactobacillus acidophilus (BLA), BS + Lactobacillus acidophilus L15 (BLA15), BS + Lactobacillus delbruekckii (BLD), and BS + Lactobacillus reuteri P24 (BLR24) groups with 3 replicates per group. Trial 2 involved two hundred forty 1-d-old broilers with equal numbers of each sex, randomly assigned into control, BBC, and pelleted BS + Bacillus coagulans L12 fermented feed (PBBC) groups with 4 replicates per group. Trial 3 involved sixteen 21-d-old male broilers randomly assigned into control and PBBC groups with 4 replicates per group for a nutrient digestibility trial. The feed conversion ratio (FCR) in the BBC group was better than the control (P < 0.05), and the production efficiency factor (PEF) was the best. However, weight gain (WG), feed intake (FI), and PEF were the lowest in the BLD group (P < 0.05). The WG during 0 to 21 d and 0 to 35 d in the PBBC groups were higher than the control (P < 0.05). The relative weight of the proventriculus + gizzard in the BBC and PBBC groups were higher than the control (P < 0.05). The digestible amino acid content in the PBBC group increased significantly (P < 0.05). Bacillus coagulans L12 is the best lactic acid bacteria for second stage fermentation. PBBC improved broiler growth performance, which may be due to the higher digestible amino acid content, it has the potential to become a commercial feed.

Specialized protein products in broiler chicken nutrition: A review

In poultry nutrition, most attention is given to protein products, due to the importance of protein as a major constituent of the biologically active compounds in the body. It also assists in the synthesis of body tissue, for that renovation and growth of the body. Furthermore, protein exists in form of enzymes and hormones which play important roles in the physiology of any living organism. Broilers have high dietary protein requirements, so identification of the optimum protein concentration in broiler diets, for either maximizing broiler performance or profit, requires more knowledge about birds' requirements for protein and amino acids and their effects on the birds' growth performance and development. It also requires knowledge about the protein sources available that can be used in poultry diets. The broad aim of this review is to highlight the importance of some of the available high-quality specialized protein products of both animal and plant origins which can be explored for feeding broiler chickens. Minimization of the concentration of anti-nutritional factors (ANFs) and supplementation with immunologically active compounds are the main focus of gut health-promoting broiler diets. These diet characteristics are influenced by feed ingredient composition and feed processing. The general hypothesis is that these protein products are highly digestible and devoid of or contain less ANFs. Feeding these products to broiler chicks, especially at an earlier age, can assist early gut development and digestive physiology, and improve broiler growth performance and immunity.

Potential of chicken by-products as sources of useful biological resources

By-products from different animal sources are currently being utilised for beneficial purposes. Chicken processing plants all over the world generate large amount of solid by-products in form of heads, legs, bones, viscera and feather. These wastes are often processed into livestock feed, fertilizers and pet foods or totally discarded. Inappropriate disposal of these wastes causes environmental pollution, diseases and loss of useful biological resources like protein, enzymes and lipids. Utilisation methods that make use of these biological components for producing value added products rather than the direct use of the actual waste material might be another viable option for dealing with these wastes. This line of thought has consequently led to researches on these wastes as sources of protein hydrolysates, enzymes and polyunsaturated fatty acids. Due to the multi-applications of protein hydrolysates in various branches of science and industry, and the large body of literature reporting the conversion of animal wastes to hydrolysates, a large section of this review was devoted to this subject. Thus, this review reports the known functional and bioactive properties of hydrolysates derived from chicken by-products as well their utilisation as source of peptone in microbiological media. Methods of producing these hydrolysates including their microbiological safety are discussed. Based on the few references available in the literature, the potential of some chicken by-product as sources of proteases and polyunsaturated fatty acids are pointed out along with some other future applications.

Chemical alterations with nutritional consequences due to pelleting animal feeds: a review

Pelleting is an energy-demanding process that is carried out on many animal feeds to assure a large macro-structure and thus improved handling properties and a high and homogenous feed intake. Due to the heat applied during conditioning and pelleting, some chemical alterations may take place. Proteins are to some extent denatured, and this will potentially improve nutritional value through inactivation of proteinous antinutrients, although may contribute negatively through inactivation of exogenous enzymes. Only a small fraction of the starch will be gelatinised, and pelleting will not affect starch digestibility to any considerable extent. Some vitamins, however, may be destroyed during the pelleting process, and viscosity of soluble fibres may increase.

Biological treatment of chicken feather waste for improved biogas production

A two-stage system was developed which combines the biological degradation of keratin-rich waste with the production of biogas. Chicken feather waste was treated biologically with a recombinant Bacillus megaterium strain showing keratinase activity prior to biogas production. Chopped, autoclaved chicken feathers (4%, W/V) were completely degraded, resulting in a yellowish fermentation broth with a level of 0.51 mg/mL soluble proteins after 8 days of cultivation of the recombinant strain. During the subsequent anaerobic batch digestion experiments, methane production of 0.35 Nm3/kg dry feathers (i.e., 0.4 Nm3/kg volatile solids of feathers), corresponding to 80% of the theoretical value on proteins, was achieved from the feather hydrolyzates, independently of the pre-hydrolysis time period of 1, 2 or 8 days. Cultivation with a native keratinase producing strain, Bacillus licheniformis resulted in only 0.25 mg/mL soluble proteins in the feather hydrolyzate, which then was digested achieving a maximum accumulated methane production of 0.31 Nm3/kg dry feathers. Feather hydrolyzates treated with the wild type B. megaterium produced 0.21 Nm3 CH4/kg dry feathers as maximum yield.

Chicken feathers: a complex substrate for the co-production of alpha-amylase and proteases by B. licheniformis NH1

This study is concerned with the co-production of alkaline proteases and thermostable alpha-amylase by some feather-degrading Bacillus strains: B. mojavensis A21, B. licheniformis NH1, B. subtilis A26, B. amyloliquefaciens An6 and B. pumilus A1. All strains produced both enzymes, except B. pumilus A1, which did not exhibit amylolytic activity. The best enzyme co-production was obtained by the NH1 strain when chicken feathers were used as nitrogen and carbon sources in the fermentation medium. The higher co-production of both enzymes by B. licheniformis NH1 strain was achieved in the presence of 7.5 g/l chicken feathers and 1 g/l yeast extract. Strong catabolic repression on protease and alpha-amylase production was observed with glucose. Addition of 0.5% glucose to the feather medium suppressed enzyme production by B. licheniformis NH1. The growth of B. licheniformis NH1 using chicken feathers as nitrogen and carbon sources resulted in its complete degradation after 24 h of incubation at 37 degrees C. However, maximum protease and amylase activities were attained after 30 h and 48 h, respectively. Proteolytic activity profiles of NH1 enzymatic preparation grown on chicken feather or casein-based medium are different. As far as we know, this is the first contribution towards the co-production of alpha-amylase and proteases using keratinous waste. Strain NH1 shows potential use for biotechnological processes involving keratin hydrolysis and industrial alpha-amylase and proteases co-production. Thus, the utilization of chicken feathers may result in a cost-effective process suitable for large-scale production.

Gene cloning and heterologous expression of a serine protease fromStreptomyces fradiaevar.k11

The gene sfp1, which encodes a predicted serine proteinase designated SFP1, was isolated by the screening of a gene library of the feather-degrading strain Streptomyces fradiae var.k11. The open reading frame of sfp1 encodes a protein of 454 amino acids with a calculated molecular mass of 46.19 kDa. Sequence analysis reveals that SFP1 possesses a typical pre-pro-mature organization that consists of a signal sequence, an N-terminal propeptide region, and a mature proteinase domain. The pre-enzyme of SFP1 was expressed in Escherichia coli and consequently purified. The 25.6 kDa fraction with protease activity separated by gel filtration chromatography indicated that the mature enzyme of SFP1 was formed by autolysis of the propeptide after its expression. The purified SFP1 is active under a broad range of pH and temperature. SFP1 has pH and temperature optima of pH 8.5 and 65 °C for its caseinolytic activity and pH 9 and 62 °C for its keratinolytic activity. SFP1 was sharply inhibited by the serine proteinase inhibitor phenylmethyl sulfonyl fluoride and exhibited a good stability to solvents, detergents, and salts. Comparison of the protease activity of SFP1 with other commercial proteases indicates that SFP1 has a considerable caseinolytic and keratinolytic activity as does proteinase K.

Lime treatment of keratinous materials for the generation of highly digestible animal feed: 1. Chicken feathers

Chicken feather keratin was treated with lime (calcium hydroxide) to obtain a liquid product rich in amino acids and polypeptides that can be used as an animal feed supplement. The effect of treatment conditions and the properties of the soluble keratin were studied. At high temperatures (150 degrees C), 80% of feather keratin was solubilized within 25 min, whereas a relatively longer reaction time (300 min) is needed at moderate temperatures (100 degrees C). After 3h of hydrolysis at 150 degrees C, 95% of feather keratin was digested. For the recommended conditions (100 degrees C, 300 min, and 0.1g Ca(OH)(2)/g dry feather), after lime treatment, about 54% of calcium can be recovered by carbonating. In rumen fluid, ammonia production from soluble keratin was similar to that of soybean and cottonseed meals and was greatly less than that of urea, indicating that no ammonia toxicity will result from cattle being fed soluble keratin.

Effect of pressure processing on amino acid digestibility of meat and bone meal for poultry

In the future, it may become desirable or required to process meat and bone meal (MBM) under pressure to reduce human health concerns associated with bovine spongiform encephalopathy (BSE). Therefore, three experiments evaluated the effects of different processing pressures on the digestibility of amino acids (AA) in MBM when the pressure processing was done after typical rendering (Experiments 1 and 2) or during the initial rendering process of raw materials (Experiment 3). Processing pressures varied from 0 to 60 psi in experimental or commercial feather meal cookers. Increasing pressure during processing reduced MBM Cys concentrations in Experiments 1 and 2. True digestibilities of most AA were significantly decreased by increasing pressures in Experiments 1 and 2, and reductions were generally largest for Cys and Lys, particularly Cys, and increased with severity as pressure increased. For example, in Experiment 1, Cys digestibility decreased from 65 to 50 to 15%, and Lys digestibility decreased from 76 to 68 to 41% as the MBM was processed at 0, 30, and 60 psi, respectively, for 20 min. When the pressure processing occurred during the initial rendering of the MBM raw material (Experiment 3), a significant reduction in digestibility of most AA was observed only at 60 psi, and the decrease was much less than that observed in Experiments 1 and 2. Our results indicate that pressure processing of MBM decreases the digestibility of AA for poultry. Thus, pressure processing of MBM to reduce potential BSE infectivity will likely decrease the nutritional value of the MBM.

Isolation and partial characterisation of extracellular keratinase from a wool degrading thermophilic actinomycete strain Thermoactinomyces candidus

The keratinase production by the thermophilic actinomycete strain Thermoactinomyces candidus was induced by sheep wool as the sole source of carbon and nitrogen in the cultivation medium. For complete digestion of wool by the above strain, both keratinolytic serine proteinase and cellular reduction of disulfide bonds were involved. Evidence was presented that substrate induction was a major regulatory mechanism and the keratinase biosynthesis was not completely repressed by addition of other carbon (glucose) and nitrogen (NH4C1) sources. The enzyme was purified 62-fold by diethylaminoethyl-anion exchange and Sephadex G-75 gel permeation chromatographies. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the purified keratinase is a monomeric enzyme with a molecular mass of 30 kDa. The pH and temperature optima were determined to be 8.6 and 70 degrees C, respectively. The purified thermophilic keratinase catalyses the hydrolysis of a broad range of substrates and displays higher proteolytic activity against native keratins than other proteinases. Ca2+ was found to have a stabilizing effect on the enzyme activity at elevated temperatures.

Utilization of fermented flocculated poultry sludge as a feed constituent for pigs

Flocculated poultry sludge was mixed with 3% molasses and was flow-therm pasteurized for 5 min at a core temperature of 95 C. The sludge was subsequently cooled to between 20 and 25 C and fermented with Lactobacillus plantarum as starter culture. Three groups of eight 8- to 10-wk-old, individually housed fattening pigs (Hypor) were fed according to a fixed scheme correlated with age. One control group received a restricted ration of commercial compound feed (Group A). The other control group was provided "nearly ad libitum" access to the same commercial compound feed (Group C). The experimental group received the same amount of commercial compound feed as Group A, but the diet was supplemented with fermented sludge, at an inclusion rate of 19 to 28% of the total ration (DM basis). The pigs fed the sludge-containing diet and those receiving the compound pig feed "nearly ad libitum" showed comparable growth results. It was concluded that the net energy (NEpig) level of .68 g DM of sludge was comparable to the NEpig level of 1 g compound pig feed (88% DM). A decrease in colony counts of Enterobacteriaceae in the intestinal tract of the pigs, was regarded as positive, as it might lower the risk of disturbance of the gut flora by enteropathogenic bacteria such as Escherichia coli and Salmonella. No adverse effects on health and performance were observed as a result of the feeding of pasteurized and subsequently fermented flocculated poultry sludge to fattening pigs. It is concluded that this sludge can serve as a valuable feed constituent as long as it is processed properly.

Characterization of a keratinolytic serine proteinase from Streptomyces pactum DSM 40530

A serine protease from the keratin-degrading Streptomyces pactum DSM 40530 was purified by casein agarose affinity chromatography. The enzyme had a molecular weight of 30,000 and an isoelectric point of 8.5. The proteinase was optimally active in the pH range from 7 to 10 and at temperatures from 40 to 75 degrees C. The enzyme was specific for arginine and lysine at the P1 site and for phenylalanine and arginine at the P1' site. It showed a high stereoselectivity and secondary specificity with different synthetic substrates. The keratinolytic activity of the purified proteinase was examined by incubation with the insoluble substrates keratin azure, feather meal, and native and autoclaved chicken feather downs. The S. pactum proteinase was significantly more active than the various commercially available proteinases. After incubation with the purified proteinase, a rapid disintegration of whole feathers was observed. But even after several days of incubation with repeated addition of enzymes, less than 10% of the native keratin substrate was solubilized. In the presence of dithiothreitol, degradation was more than 70%.

Microbial and nutritional aspects of feeding fermented feed (poultry by-products) to pigs

Broiler by-products (heads, feet, and viscera) mixed with 4% dextrose were pasteurized for 4 min at 90 degrees C core temperature, cooled to 20 degrees C, and fermented with Lactobacillus plantarum as starter culture. These fermented poultry by-products were fed to 12 individually housed fattening pigs as part (17.6% of the dry matter) of their fattening ration, the remainder composed of compound pig feed. Control pigs received a compound pig feed only. Both groups of pigs were fed restrictively on the basis of body weight. The technical results of the pigs fed the experimental diet showed a significantly improved feed:gain ratio (2.46 vs 2.57), a significantly higher carcass weight (86.1 vs 81.8 kg), a lower meat percentage (50.9 vs 52.5%) and an increased backfat thickness (21.5 vs 18.7%). The bacterial flora in the intestinal tract of the pigs fed the experimental diet differed significantly from the control animals. Decreased colony counts of mesophilic aerobic bacteria, Enterobacteriaceae, enterococci and lactobacilli were found in the rectal content and the prevalence of salmonella was lower. It is suggested that the improved feed:gain ratio and the reduced bacterial activity of the measured groups of bacteria is a result of 1) the higher energy content of the diet, and(or) 2) an assumed enhanced digestibility of nutritional components in the diet, and(or) 3) the lower incidence of diarrhea in the pigs fed with fermented poultry by-products. This resulted in a lower contamination level of enteropathogenic bacteria like, salmonella and Escherichia coli, in the gastro-intestinal tract of the pigs fed fermented poultry by-products.

Slaughter by-products: problems, preliminary research and possible solutions

The collection, storage, disposal and processing of slaughterhouse by-products is an important part of veterinary care in regions with intensive animal husbandry and meat production. Transmission of diseases and environmental pollution through an improper and/or incorrect handling of slaughterhouse by-products needs to be prevented. The use of animal by-products as feedstuff could be of economical benefit to slaughterhouses and could add nutritive value to animal feed. As a results of the centralisation and intensification of slaughtering, the amount of slaughter by-products produced at a single location is increasing. Until now, hardly any attention, in practice or in research, has been paid to the collection and disposal of these by-products. There are important socio-economic reasons to increase scientific knowledge about the handling of slaughter by-products. Several animal by-products were contaminated with Salmonella. We also showed that rapid breakdown of amino acids in poultry by-products occurs during storage at 20 degrees C. It is concluded that as far as safety, environmental care and nutritive value of animal by-products is concerned, diversification and separation of slaughter by-product collection, storage, disposal and processing is necessary. Measures at source, the slaughterline, and some technologies are suggested for future use.