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Context: A great body of evidence is available on the in vitro efficacy of white-rot fungi (WRF) to degrade lignin in fibre-rich biomass (e.g. wheat straw, wood chips and rice straw (RS)) and improve the biomass' nutritive value for ruminants. Aims: Determining the impact of incubation temperature of three WRF to improve the nutritional value of rice straw. Methods: Growth of Ceriporiopsis subvermispora, Lentinula edodes and Pleurotus eryngii on RS for 26 days at the following six temperature regimes: continuous at 24°C, 30°C, 35°C and 40°C, and 3 days at 35°C and 40°C, with subsequent days at 24°C. In a follow-up experiment, improvement in fermentability in buffered rumen fluid of RS treated by the three WRF at 24°C and 30°C for up to 8 weeks was investigated. Key results: All three fungi grew at temperatures up to 35°C, with no growth observed at 40°C, with C. subvermispora being more temperature sensitive. There were significant differences in cellulose, hemicellulose and lignin degradation of RS at 24°C and 30°C, with C. subvermispora degrading 69% and 90% of the hemicellulose and lignin respectively at 30°C, greater than at 24°C (55% and 80% respectively). For L. edodes, there were significant differences in cellulose degradation between 24°C and 30°C, with 12% more degradation at 30°C, but not for hemicellulose and lignin. In vitro gas production showed no significant differences between the two incubation temperatures for either of the two fungi. Pleurotus eryngii treatment did not show any improvement in terms of in vitro gas production. Conclusions: Treatment of RS with L. edodes and C. subvermispora, but not P. eryngii, is robust and temperature changes will not have a major impact on their efficacy as long as the temperature remains below 30°C. Implications: Temperature during the incubation of WRF with rice straw needs to be below 30°C for this biotechnology to be applied in practice.

In-home pet food testing has the benefit of yielding data which is directly applicable to the pet population. Validated and standardised in-home test protocols need to be available and here we investigated key protocol requirements for an in-home canine food digestibility protocol. Participants were recruited via an online survey. After meeting specific inclusion criteria, 60 dogs of various breeds and ages received during 14 consecutive days, a relatively low and high digestible complete dry extruded food containing titanium (Ti) dioxide. Both foods were given for seven days in a cross-over design. Owners collected faeces daily allowing daily faecal Ti concentrations and digestibility of nitrogen (N), dry matter, crude ash, organic matter, crude fat (Cfat), starch and gross energy to be determined. Faecal Ti and digestibility values for all nutrients were not different (P>0.05) from the second day onwards after first consumption for both foods. One day of faecal collection yielded reliable digestibility values with additional collection days not reducing the confidence interval around the mean. Depending on the accepted margin of error, the food and the nutrient of interest, the minimal required sample size was between 9-43 dogs. Variation in digestibility values could in part be explained by a dog's neuter status (N, crude ash) and age (crude ash, Cfat), but not sex and body size. Future studies should focus on further identifying and controlling sources of variation to improve the in-home digestibility protocol and reduce the number of dogs required.

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

Due to the growing demand for food, the availability of starch-rich ingredients (e.g. feed grade cereals), whose areal can be used for producing food, is expect to decline. In turn, the use of co-products, from food- and biofuel industry, is expected to increase in livestock feed. However, these co-products are fibre-rich and can negatively affect pellet manufacturing, by reducing pellet quality and increasing energy costs. The thermomechanical properties of feed mashes are considered to be important for agglomeration processes, but its relation to feed composition and its role in pellet manufacturing is poorly understood. The aim of this study was to investigate the effect of fibrous co-product inclusion in feed mashes on their thermomechanical properties and subsequent effects on pellet manufacturing. Treatment mashes were formulated to contain 700 g/kg basic mash, consisting of soybean meal, maize, and soy oil, to which 0–300 g/kg palm kernel expeller, sugar beet pulp, wheat straw and isolated native maize starch were added, according to a four-component mixture design. Treatments were prepared in duplicate, conditioned using a single-shaft conditioner and compacted using a ring-die pelletizer (die hole diameter 6 mm, L/D ratio 12). Pellet quality, production capacity and gross specific mechanical energy consumption per megagram (Mg) were documented. Mash deformability was evaluated by increasing the moisture content of a mash sample to 150 g/kg, followed by compression at 10 MPa and increasing temperature by 4 °C/minute using the Phase Transition Analyzer (PTA; Wenger Manufacturing, Sabetha, KS, US). Inclusion of wheat straw significantly increased mash deformability. Inclusion of isolated native maize starch and fibrous co-products was observed to increase pellet quality in comparison to the basic mash. Mash deformability at compactor temperature was correlated with bulk density (r = −0,83; P < 0.001). Pellet compressive strength was associated with mash deform

The world population is growing, and improving living standards and urbanisation are driving factors in the global increase in meat, egg and milk consumption (Boland et al., 2013). Poultry production is a key factor in providing sufficient animal protein. To achieve efficient poultry production, highly digestible diets need to be fed, often resulting in competition for resources for human consumption (the food-feed competition). This intensifies the search for novel dietary ingredients that neither compete for resources, nor for arable land and freshwater. Seaweed is such a novel dietary ingredient of interest. This thesis describes studies into the nutritional value of various seaweed species (an alternative protein source), with a focus on nutritional composition, digestibility and health in broiler chickens.In Chapter 2 the composition of intact seaweeds obtained from coastal waters in Northwestern Europe were studied as source of macronutrients for livestock. The chemical composition, in vitro digestibility and in vitro gas production were determined. The seaweed species included in this study were brown: Saccharina latissima, Laminaria digitata and Ascophyllum nodossum, red: Palmaria palmata and Chondrus crispus, and green: Ulva lactuca. The nutrient content was highly variable between and within species. Based on the protein content and amino acid pattern, intact P. palmata and U. lactuca could be a valuable protein source for farm animals, with the high non-starch polysaccharides and non-protein nitrogen contents and a low in vitro digestibility potentially limiting their use as a feed ingredient for monogastric species. Furthermore, the fermentability of L. digitata, S. latissima and P. palmata indicate that these intact seaweeds may have a higher nutritional value in ruminants. The high ash content hampers the use of intact seaweed for both ruminants and simple stomached animal species.To be able to include seaweed in broiler diets, the ash content needs to

The impact of addition of an Ulva laetevirens (previously Ulva rigida) co-product treated with a broad-spectrum endo-protease when added to a standard corn-soy (S) based diet and a diet based on European protein sources (EU) on performance, in vivo digestibility and multiple gastrointestinal characteristics was investigated in broilers. In total, 624 Ross 308 one-day-old male broilers were fed one of 6 experimental diets (8 replicates) consisting of a basal diet (S or EU), or a basal diet including the U. laetevirens co-product (U) treated without (U-) or with (U+) a proteolytic enzyme. Starter diets contained 0 (wk 1) and 2.5 (wk 2), and the grower diets (wk 3 and 4) 5% seaweed co-product. In the last 2 wk, birds fed the S vs. EU grower diets showed a higher BW, BWG, and FI, as well as a lower FCR (−0.05 g/g) in wk 3 (P < 0.05). Heavier gizzards (+13%; P < 0.001) and heavier gizzard contents (+92%; P < 0.001) were observed in birds fed the EU vs. S diets, as well as longer villi (+8%; P = 0.010). U diets had a higher water holding capacity than the basal diets (+19%). In wk 4, U inclusion resulted in increased FCR (+0.06 g/g; P < 0.001), water intake (+7%; P < 0.001), and duodenal cross section (+5%; P = 0.033). Enzyme treatment did not affect digestibility of any nutrients, except for ash which was increased in birds fed U+ vs. U- diets (+60%; P < 0.001). U in S diets led to higher, and U in EU diets led to lower apparent pre-cecal digestibility of all nutrients (P < 0.001 for all nutrients). Although for both diet types performance was decreased, dietary U. laetevirens inclusion had different effects when added to a standard corn-soy diet and a diet based on European protein sources. No obvious health effects were observed, leading to the conclusion of the absence of performance of health promoting bioactive components in the U. laetevirens co-product, or of diminishing of these effects due to the proteolytic enzyme treatment.

Grinding is an important feed processing technology, determining physical and nutritional characteristics of ground materials, which affects nutrient digestion in animals and their growth performance. This study aimed to clarify if differences in moisture content (MC) lead to differences in nutrient composition over various particle size fractions after grinding that have potential to affect feed manufacturing characteristics or animal performance. Maize and soybean meal (SBM) with targeted MC of 120, 140 and 160 g/kg (adding no (0), 30 and 60 g/kg of tap water, respectively) were hammer-milled and the physical and chemical characteristics as well as in vitro apparent ileal digestibility (AID) of particle size fractions were determined. The mill was fitted with a 6-mm (maize) or 2-mm (SBM) sized screen, with milled material subsequently separated by dry sieving (size ranging from < 0.075 to > 3.36 mm) and each fraction was analyzed for its nutrient composition, morphology characteristics and in vitro AID of organic matter (OM) and crude protein (CP). For the latter assay, specific particle size fractions were additionally ground using a laboratory mill (1 mm screen). Geometric mean particle size diameter and energy consumption increased with increasing MC (P < 0.05). Chemical composition, physical characteristics and in vitro AID of particle size fractions were significantly different (P < 0.001). Moisture addition had no significant effect on nutritional and physical parameters except for solidity in maize, ash content, projected area, circularity, and solidity in SBM. Physical characteristics of particles, especially particle size affected in vitro AID of OM and CP most (P < 0.05). Additional grinding of samples before determination of in vitro AID increased the OM digestibility up to 0.684 in maize (P < 0.001). Additional grinding of particles larger than 0.595 mm increased in vitro AID of OM and CP (P < 0.05). In summary, increasing MC has limited effect on the

Housefly larvae can be reared on manure and used as animal feed. Larvae can utilise proteins and easily digestible carbohydrates and have a largely unknown relation with microorganisms. The hypothesis addressed in this study was that larvae compete with microorganisms for easily digestible carbohydrates such as starch. This was tested by adding starch or (non-digestible) fructo-oligosaccharides (FOS) to unsterilised or heat-sterilised fresh chicken excreta. Experimental substrates were unsterilised excreta (E), sterilised excreta (sE) with either starch (E + star, sE + star) or FOS (E + FOS, sE + FOS). The highest wet yield (9.7 g) and heaviest larvae (13.2 mg) were on sE + star, followed by E (7.2 g and 8.1 mg). Both E + FOS and sE + FOS had minimal yields and larval weights (0.3 and 0.2 g, 2.9 and 1.7 mg) with E + star intermediate (3.3 g and 7.5 mg). Survival differed between diets, sE and E averaged 70%, sE + star 57%, E + star 33% with 9% for E + FOS and sE + FOS. DM bioconversion decreased from E (3.5%), sE + star (3.1%), sE (2.6%), E + star (1%) to E + FOS and sE + FOS (0.1%). Nitrogen bioconversion was highest on sE + star (9.9%) and E (9.3%), lower on sE (6.6%), E + star (4%) and the lowest on E + FOS and sE + FOS (0.5%). Different substrate temperature profiles during the larval growth period and different larval size distributions were found for the different substrates. The results support the hypothesis that larvae compete with microorganisms for an easily digestible carbohydrate (starch).

Particle size plays an important role in the digestibility of nutrients by animals. Methodologies developed to simulate the digestive system to determine digestibility values require the grinding of samples to pass a specific sieve size (e.g. 1 mm) before in vitro digestion. The objective of this study was to evaluate if particle size affects in vitro (ileal) digestibility values of organic matter (OM) and crude protein (CP) in maize and soybean meal (SBM). Both ingredients were ground in a laboratory mill over four screens (1.50, 1.00, 0.75 and 0.50 mm) with trapezoidal holes in a sequential manner from large to fine. Particle size distribution, nutrient content and in vitro digestibility were determined of the various samples. With decreasing screen size, geometric mean diameter of particles significantly decreased from 351.4 to 203.2 µm for maize, and from 239.1 to 99.1 µm for SBM. Ash, CP and starch content were not affected whereas the neutral detergent fibre in maize and dry matter content in SBM differed after grinding with various sized screens (P < 0.05). The in vitro digestibility of OM and CP of maize and CP of SBM ground over the four different screens did not differ (P > 0.185). The OM in vitro digestibility differed (P < 0.05) with values for SBM ground over the 1.50 mm screen being lower (P < 0.05) than the smaller screen sizes: 0.814 (1.50 mm) vs 0.833 (1.00 mm), 0.829 (0.75 mm) and 0.834 (0.50 mm), respectively. Based on the current work and literature data, particles ≥ 595 µm of comminuted maize and SBM affect OM and CP in vitro digestibility. Analysis of three feeds and 10 feed ingredients ground over a 1.0 mm sieve showed that the fraction ≥ 595 µm can make up to 32.1% of the mass. It is recommended that before in vitro digestibility determination, particle size distribution is assessed, especially the mass fraction of particles ≥ 595 µm and further grinding is conducted to ensure that particles are < 595 µm for maize and SBM. The cut off size wh

To explore the potential use of seaweed co-products for broiler diets, this study investigates whether an enzyme treatment of seaweed co-products improves performance, in vivo digestibility and health in broilers. In total, 360 Ross 308 male broilers were fed one of 5 experimental diets: a basal diet, or a basal diet including the U. laetevirens or S. chordalis co-product, with or without proteolytic enzyme treatment of the seaweed, using 6 replicate pens of 12 birds each. The starter (d 0–13) and grower (d 14–21) diet contained 5 and 10% (w/w) seaweed product, respectively. A general linear model with contrast statements was used after model assumptions and goodness of fit were evaluated through normal distribution of residuals. Inclusion of seaweed in the broiler diets increased body weight gain (+14%; P = 0.002), and feed intake (+12%; P = 0.001) in the third week of the experiment. Birds fed the U. laetevirens compared to the S. chordalis diets had a higher body weight gain (+11%; P = 0.007), and a lower feed conversion ratio (FCR; -7%; P < 0.001). Seaweed inclusion reduced apparent pre-cecal digestibility of all nutrients (P < 0.05). Birds fed U. laetevirens vs. S. chordalis diets had a 10% reduced villus length (P < 0.001). Enzymatic treatment reduced the digestibility of most nutrients, and increased crypt depth in birds fed the U. laetevirens diets, whereas the opposite was observed for the birds fed the S. chordalis diets (Seaweed × Enzyme P = 0.035). Untreated vs. treated seaweed in the diets led to lower (−60%) plasma Interleukin-13 levels (P = 0.035). In conclusion, the proteolytic enzyme treatment of the seaweed co-products did not improve performance nor health-related parameters, and reduced digestibility of the diets. Dietary inclusion of U. laetevirens co-products did improve performance based on growth and FCR, whereas inclusion of S. chordalis did not. Inclusion of U. laetevirens in broiler diets slightly reduced duodenal villus length and crypt d

Feed processing involves the use of various technologies to transform feed ingredients into valuable feeds enabling the production of animal-sourced foods (e.g. meat, eggs, milk). Hammer-milling, a standard technology used in the feed industry, is a critical process affecting feed efficiency and animal production. After grinding, the particle size of ingredients is reduced, the physical characteristics of particles and nutrient distribution are changed, which can affect the digestibility and kinetics of nutrient digestion.The research described in this thesis provides hitherto unknown insights into the breakage of maize and soybean meal as a result of hammer-milling via physical and chemical characteristics as well as in vitro digestibility of nutrients of size-fractionated particles. Moisture content and mixture ratio effects of feed ingredients on the breaking behaviour were also investigated enabling the development of novel grinding strategies to produce feeds with higher nutrient digestibility. This thesis provides important data on the importance of sample preparation before in vitro digestion analysis to improve the prediction and repeatability of nutrient digestibility estimates.