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The hypothesis that dietary inclusion of microbial phytase improves apparent calcium (Ca) digestibility thereby allowing a lower dietary Ca inclusion without compromising growth performance was tested. One-day-old male Ross 308 broilers (25 birds/pen, 9 pens/treatment) were assigned to 8 experimental diets containing one of 4 dietary Ca to retainable P (rP) ratios (1.3, 1.8, 2.3, and 2.8) with (1,000 FTU/kg) or without microbial phytase. On d 21 to 23, digesta from different intestinal segments of 8 birds per pen were collected to determine apparent Ca and P digestibility. Mid duodenal mucosa was collected for expression of Ca (CaBP-D28k, PMCA1) and P (NaPi-IIb, PiT-1, PiT-2, and XPR1) transporters by RT-qPCR. Dietary phytase inclusion in low Ca/rP diets increased Ca digestibility in the distal ileum (Pinteraction = 0.023) but not the proximal or distal jejunum. Broilers receiving the lowest Ca/rP displayed the lowest body weight gain, highest feed conversion ratio (P < 0.001), and lowest tibia strength, irrespective of dietary phytase inclusion. Incremental dietary Ca/rP linearly reduced P digestibility to a greater extent in the absence of phytase in the distal jejunum and ileum (Pinteraction = 0.021 and 0.001, respectively). Incremental dietary Ca/rP linearly reduced serum P more in phytase-free diets (Pinteraction < 0.001), and lowered duodenal expression of P transporters NaPi-IIb, PiT-2, and XPR1 (P = 0.052, 0.071 and 0.028, respectively). Incremental dietary Ca/rP linearly increased (P < 0.001) serum Ca irrespective of phytase inclusion, accompanied by a lower (P < 0.001) duodenal expression of Ca transporters CaSR, CaBP-D28k and PMCA1 and Ca-pore forming claudins CLDN-2 and CLDN-12. Dietary phytase increased (P = 0.026) NaPi-IIb but reduced (P = 0.029) CLDN-2 expression. Incremental Ca/rP reduced Ca and P digestibility, increased serum Ca, lowered serum P and inhibited mRNA levels of Ca and P-related transporters, indicating that these transporters and CLDN contribute to the observed effect of dietary Ca and phytase on Ca and P absorption. Despite the improvement in Ca digestibility, dietary phytase did not restore the compromised growth performance and tibia strength of broilers fed a Ca-deficient diet, leading to rejection of the hypothesis.

This study was designed to evaluate the effects of green light emitting diode (LED) light during incubation and dietary organic macro and trace minerals during rearing on tibia morphological, biophysical, and mechanical characteristics of broiler chickens at slaughter age. The experiment was setup as a 2 × 2 × 2 factorial arrangement, with the following treatments: 1) light during incubation (green LED light or darkness), 2) macro mineral source during rearing (organic or inorganic Ca and P), and 3) trace mineral source during rearing (organic or inorganic Fe, Cu, Mn, Zn, and Se). A total of 2,400 eggs (Ross 308) were either incubated under green LED light (16L:8D) or in complete darkness. After hatch, a total of 864 male broiler chickens were reared until slaughter age (day 42) and provided with 1 of 4 diets, differing in macro and/or trace mineral source. During rearing, the experiment had a complete randomized block design with 9 replicate pens per treatment and 12 chickens per pen. At slaughter age (day 42), 2 chickens per replicate were randomly selected and tibia bones were obtained. Tibia weight, length, thickness, osseous volume, pore volume, total volume, mineral content, mineral density, ultimate strength, and stiffness were determined. Green LED light during incubation did not affect any of the tibia characteristics. Dietary organic macro minerals positively affected most of the tibia morphological, biophysical, and mechanical characteristics compared to the inorganic macro minerals, whereas trace mineral sources did not affect tibia characteristics. It can be concluded that dietary organic macro minerals Ca and P stimulated tibia characteristics, whereas green LED light during incubation and dietary trace minerals during rearing did not affect tibia characteristics, locomotion, or leg disorders.

The increasing demand for animal protein by the growing world population intensifies the exploration of novel feed sources. This study evaluated the nutritional value of six intact seaweed species (i.e. the brown species Saccharina latissima, Laminaria digitata, and Ascophyllum nodossum, the red species Palmaria palmata, and Chondrus crispus and green species Ulva lactuca), collected from the coast of Ireland, Scotland and France as an ingredient for animal feed. The nutrient composition, in vitro digestibility, and in vitro gas production simulating rumen fermentation, were determined. The nutrient contents (g/kg dry matter), both between and within species, were highly variable, ranging from 45–248 for crude protein, 351–691 for non-starch polysaccharides, and 173–445 for ash. Overall, the brown seaweeds had the highest non-starch polysaccharides content, whereas samples of the red and green seaweeds had an amino acid content up to 265 g/kg dry matter. All samples had a substantial non-protein nitrogen fraction, varying from 0.12–0.29 of nitrogen. The fibre fractions of brown seaweeds showed different properties than land-based plants, as illustrated by a lower analysed neutral detergent fibre than acid detergent fibre content. The ileal organic matter and nitrogen digestibility, as well as the total tract organic matter digestibility (mean digestibility coefficients: 0.81, 0.89 and 0.88, respectively) were lower for all seaweeds compared to soybean meal (digestibility coefficients: 0.84, 0.98 and 0.97, respectively). S. latissima, L digitata, P. palmata and U. lactuca had a higher maximum gas production than alfalfa, but lower than sugar beet pulp. Based on the protein content and amino acid-pattern, intact P. palmata and U. lactuca would 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. 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 in all seaweed species hampers the use of intact seaweed for both ruminants and monogastrics. Extraction of protein and other favourable components, while reducing the ash content, seems an important step towards seaweed inclusion in animal diets. Further identification and characterisation of seaweed polysaccharides is required to understand and improve the digestibility of seaweed fractions.

Feather pecking (FP) by laying hens is a significant welfare issue in the poultry industry. Pecking at and pulling out feathers of conspecifics can seriously reduce the well-being of birds and causes economic losses for the farmer. Records of FP in laying hen flocks from the last 20 years show a prevalence of between 24% and 94%. Several research groups worldwide have hypothesised about the causes of FP. From a nutritional point of view, re-directed behaviour and feather eating seem to be the most plausible causes. The gut microbiome seems to be involved in FP due to its influence on hormonal pathways and as it is influenced by the diet, which might include feathers ingested by the hens. Bird experiences during the rearing period are related to FP in later life by possible effects on the physiological development of the pullets. Most likely, pullets experience a sensitive period within the first few weeks post-hatch during which FP can develop due to various factors such as hormonal influences, nutrition and (the lack of) environmental enrichment. Nutrition could influence FP in two ways. Imbalances in certain nutrients, such as amino acids may have a direct effect on physiological mechanisms that trigger FP. Furthermore, ingredients such as roughages, fibres and non-nutritive ingredients may have an effect on exploratory and foraging or feeding behaviour. Literature (mainly in adult layers) shows that nutritional interventions increased eating time by 23–45% and/or the mean retention time of feed in the gut by 2.9–6.0 min/g fibre, and reduced or delayed FP. Using nutritional strategies (i.e. provision of specific AA profiles and/or high fibrous ingredients) during the sensitive period during rearing could prevent ultimately the development of FP, by altering the pullets’ (gut) physiology and/or her time allocation. Research focussing on critical periods during rearing should be initiated.

An experiment was conducted to investigate the effects of dietary inclusion of rye, a model ingredient to increase gut viscosity, between 14 and 28 d of age on immune competence-related parameters and performance of broilers. A total of 960 day-old male Ross 308 chicks were weighed and randomly allocated to 24 pens (40 birds per pen), and the birds in every 8 replicate pens were assigned to 1 of 3 experimental diets including graded levels, 0%, 5%, and 10% of rye. Tested immune competence-related parameters were composition of the intestinal microbiota, genes expression in gut tissue, and gut morphology. The inclusion of 5% or 10% rye in the diet (d 14 to 28) resulted in decreased performance and litter quality, but in increased villus height and crypt depth in the small intestine (jejunum) of the broilers. Relative bursa and spleen weights were not affected by dietary inclusion of rye. In the jejunum, no effects on number and size of goblet cells, and only trends on microbiota composition in the digesta were observed. Dietary inclusion of rye affected expression of genes involved in cell cycle processes of the jejunal enterocyte cells, thereby influencing cell growth, cell differentiation and cell survival, which in turn were consistent with the observed differences in the morphology of the gut wall. In addition, providing rye-rich diets to broilers affected the complement and coagulation pathways, which among others are parts of the innate immune system. These pathways are involved in eradicating invasive pathogens. Overall, it can be concluded that inclusion of 5% or 10% rye to the grower diet of broilers had limited effects on performance. Ileal gut morphology, microbiota composition of jejunal digesta, and gene expression profiles of jejunal tissue, however, were affected by dietary rye inclusion level, indicating that rye supplementation to broiler diets might affect immune competence of the birds.

The objective of this ring test was to investigate the prececal phosphorus (P) digestibility of soybean meal (SBM) in broiler chickens using the trial protocol proposed by the World's Poultry Science Association. It was hypothesized that prececal P digestibility of SBM determined in the collaborating stations is similar. Three diets with different inclusion levels of SBM were mixed in a feed mill specialized in experimental diets and transported to 17 collaborating stations. Broiler chicks were raised on commercial starter diets according to station-specific management routine. Then they were fed the experimental diets for a minimum of 5 d before content of the posterior half of the ileum was collected. A minimum of 6 experimental replicates per diet was used in each station. All diets and digesta samples were analyzed in the same laboratory. Diet, station, and their interaction significantly affected (P < 0.05) the prececal digestibility values of P and calcium of the diets. The prececal P digestibility of SBM was determined by linear regression and varied among stations from 19 to 51%, with significant differences among stations. In a subset of 4 stations, the prececal disappearance of myo- inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate)-P; InsP6-P) also was studied. The prececal InsP6-P disappearance correlated well with the prececal P digestibility. We hypothesized that factors influencing InsP6 hydrolysis were main contributors to the variation in prececal P digestibility among stations. These factors were probably related to the feeding and housing conditions (floor pens or cages) of the birds in the pre-experimental phase. Therefore, we suggest that the World's Poultry Science Association protocol for the determination of digestible P be should extended to the standardization of the pre-experimental period. We also suggest that comparisons of P digestibility measurements among studies are made only with great caution until the protocol is more refined. info:eu-repo/semantics/publishedVersion

Processed Animal Proteins (PAPs) have long been banned from farm animal diets in the EU. In this period, raw material selection and processes to prepare PAPs have been improved and diversified allowing for a range of products available for inclusion in animal diets. As a consequence, the products and their respective specifications in present feedstuff tables do not cover the composition and quality of presently available PAPs. This report presents the methods and results of a study, conducted by Wageningen Livestock Research at the request of European Fat Processors and Renderers Association (EFPRA), in which the total tract digestibility of proximate components and ileal phosphorus, calcium and amino acid digestibility of 2 PAPs of pig origin in broiler chickens were evaluated. The results from this study showed that the chemical composition of the new PAPs are broadly similar to the 'former' PAPs, but that the AME and the digestibility of crude fat, crude protein and amino acids of the new PAPs was lower. Therefore it is recommended, once the ban on the use of animal proteins in broiler diets ends, to update the present PAP table figures for broilers.

The aim of the current study was to determine the degradation of free amino acids in freshly produced liquid feeds. It can be concluded that the level of degradation of free amino acids in liquid feeds might be limited, provided the conditions applied in the current study.---Het doel van deze studie was na te gaan in welke mate vrije aminozuren gevoelig zijn voor afbraak onder brijvoercondities. Onder de toegepaste condities in dit onderzoek trad er slechts in beperkte mate degradatie van vrije aminozuren in de brijvoeders op.

Nutrition is a crucial factor for growth and bone development in broiler chickens. Adjustments in dietary ingredients might affect bone development and consequently locomotion related problems. This study was designed to evaluate effects of dietary organic minerals (ORM), fish oil (FISH), and hydrolyzed collagen (COL) on growth performance and tibia characteristics of broiler chickens. A total of three hundred eighty four 1-day-old Ross 308 male broiler chickens were used in a complete randomized block design with 4 diet groups and 8 replicates per diet group. In the ORM diet, the inorganic macro and trace minerals were replaced by their organic varieties. In the FISH diet, palm oil and soybean oil were partly replaced by FISH. In the COL diet, soybean meal was partly replaced by COL. Results showed that the ORM and COL diet groups reached a higher body weight (BW) at 42 D of age than the FISH diet group, whereas the control group was in between. The feed conversion ratio between day 1 and 42 was lower in the ORM and COL diet groups than in both other diet groups. On day 28, 35, and 42, gait score (GS), Varus Valgus deformity, tibia length (TL), thickness, femoral and metatarsal head thickness (THT), mineral content (TMC), mineral density (TMD), breaking strength (TBS), stiffness (TSF), and energy to fracture (TEF) were measured (n = 3/replicate). The ORM diet group had higher TL at day 42, higher THT at day 28, higher TMC at day 42, higher TMD at day 28, 35, and 42, higher TBS at day 42, higher TSF at day 35 and 42, and higher TEF at day 42 compared to the FISH diet group, with the COL and control diet groups in between. It can be concluded that replacing dietary inorganic macro and trace minerals by their organic varieties seems to stimulate tibia dimensions, strength, and mineral content of broiler chickens. On the contrary, FISH appears to negatively affect tibia characteristics.

A study with 884 Ross 308 male broilers, housed in 68 floor pens (0.75 m2) from 0 to 35 days of age was conducted to evaluate the effects of low crude protein (CP) diets, with partial replacement of soybean meal by free amino acids (AA), on performance, slaughter yields, litter quality and footpad lesions. During the first 11 d, all broilers received the same control starter diet (216 g/kg CP, 11.5 g/kg apparent fecal digestible (AFD) lysine, and 2900 kcal/kg AMEn). Thereafter, four experimental feeding programs with different levels of dietary CP (control and control with 1% (CP-1%), 2% (CP-2%) and 3% (CP-3%) less CP units) were provided in both the grower and finisher phase. In the control grower and finisher diet, the CP content was 208 and 198 g/kg, respectively. All diets were formulated to meet or exceed the recommendations concerning AFD AA, and to be iso-caloric within each feeding phase. Feed and water were provided for ad libitum intake during the entire experimental period. None of the low CP feeding programs affected body weight gain, feed intake or mortality from 0 to 35 d. However, CP conversion was improved with the reduction of CP content of the diet. Broilers fed the CP-2% or CP-3% feeding program had an improved feed conversion ratio. Broilers fed the low CP protein feeding programs had a better litter quality and less footpad lesions, compared to broilers fed the control feeding program. Broilers fed the CP-3% feeding program had a lower breast meat yield than broilers fed the control feeding program. Slaughter yields of broilers fed CP-1% or CP-2% feeding program did not differ from the control feeding program. This study demonstrated that the CP content of grower and finisher diets can be reduced by 2.2–2.3% units without adverse effects on growth performance of broilers, while CP reduction seems promising to reduce nitrogen excretion from broiler houses, improve bird welfare, and reduces dependence on vegetable protein sources.

This report presents the methods and results of a study, conducted by Wageningen Livestock Research at the request of EFPRA, in which the effect of partially replacement of soybean meal by two different processed animal proteins (PAPs) of pig origin on performance results, intestinal health, litter quality, footpad lesions and bone quality in broilers chickens from 0 – 42 days was evaluated. The two PAPs differ from each other in processing method. From this study it was concluded that it is possible to replace a part of the dietary soybean meal by processed proteins from pig origin, while maintaining performance results, litter quality, footpad health, gait, intestinal health and bone quality.

1. An experiment was conducted to evaluate the effects of technical feed ingredients between 14 and 28 d of age on performance and health status of broilers (d 14–35) fed diets with a high inclusion rate of rapeseed meal as a nutritional challenge. It was hypothesized that the feed ingredients would improve health status related parameters. 2. A total of 1008 one-day-old male Ross 308 chicks were distributed over 36 floor pens and allocated to one of six iso-caloric (AMEN 13 MJ/kg) growing diets (d 15–28): a control and five test diets supplemented with quercetin (400 mg/kg), oat hulls (50 g/kg), β-glucan (100 mg/kg), lysozyme (40 mg/kg) or fish oil ω-3 fatty acids (40 g/kg), with six replicate pens per treatment. 3. Dietary inclusion of oat hulls and lysozyme resulted in a reduction in broiler performance during the first week after providing the experimental diets. 4. No effect of interventions on the microbiota diversity in the jejunum and ileum was observed. Ileal microbiota composition of birds fed oat hulls differed from the other groups, as shown by a higher abundance of the genus Enterococcus, mainly at the expense of the genus Lactobacillus. 5. In the jejunum, villus height and crypt depth of lysozyme-fed birds at d 28 were decreased compared to the control group. Higher total surface area of villi occupied by goblet cells and total villi surface area in jejunum (d 21 and 28) were observed in chickens fed oat hulls compared to other groups. 6. Genes related to the growth-factor-activity pathway were more highly expressed in birds fed β-glucan compared to the control group, while the genes related to anion-transmembrane-transporter-activity pathway in the quercetin- and oat hull-fed birds were less expressed. The genes differently expressed between dietary interventions did not seem to be directly involved in immune related processes. 7. It was concluded that the tested nutritional interventions in the current experiment only marginally effected health status related parameters.

An experiment with 288 male (Ross 308) 1-d-old broilers was conducted to test the hypothesis that a coarse diet supplemented with butyric acid (BA) and fermentable carbohydrates (FC) improves performance of broilers with a poorly digestible protein source. The interaction effects of diet structure (fine or coarse), FC supplementation (with or without), and BA supplementation (with or without) in a poorly digestible diet based on rapeseed meal (RSM) were tested in a factorial arrangement of 8 (2 × 2 × 2) dietary treatments. The coarseness of the diet affected feed intake (FI) (P < 0.001), BW gain (P = 0.001), and the feed conversion ratio (FCR) (P = 0.001) positively. Broilers fed the coarse diets had, on average, 14% heavier gizzards and 11, 7, 5, and 6% lower relative empty weights of the crop, duodenum, jejunum, and ileum, respectively, compared with those fed the fine diets. Dietary coarseness resulted in, on average, 6% greater ileal protein digestibility, 20% lower gizzard pH, 19% greater villus height, 18% lower crypt depth, and 23% reduced cecal branched chain fatty acids (BCFA) compared with chickens fed the fine diets. Broilers fed BA-supplemented diets had an improved FCR (P = 0.004) and decreased crypt depth (P < 0.001) compared with those fed diets without BA. Fermentable carbohydrate supplementation did not influence growth performance, gut development, or contents of total BCFA and total biogenic amines in the cecal digesta (P > 0.05). Supplementation with FC, however, decreased the cecal concentration of spermine by approximately 31% compared with broilers fed diets without FC (P = 0.002). In conclusion, feeding a coarse diet supplemented with BA improved performance of broilers fed a diet containing a poorly digestible protein source. The negative effects of a poorly digestible protein source can thus be partly counterbalanced by coarse grinding and BA supplementation in the diet.

A broiler study was performed to determine the pre-cecal phosphorus (P) digestibility of 5 P sources, 3 from animal (Delfos, Calfos, and porcine bone meal) and 2 of inorganic (monocalcium phosphate [MCP] and dicalcium phosphate [DCP]) origin. Delfos is processed from bones resulting in a dicalcium phosphate product, and Calfos is processed from bones in which part of the gelatin is removed but in which the hydroxy-apatite matrix is preserved. During the first 14 d, birds were housed in floor pens bedded with wood shavings and received a commercial starter diet. At d 14, broilers were randomly assigned to pens (0.9 m2, 10 birds/pen) with a slatted floor. From d 14 onwards, one of the 6 experimental diets (a basal diet, and 5 diets containing the P sources) was provided. Test diets were replicated 6 times, and the basal diet 8 times. Electron microscopy images of test products were made in order to verify whether the spatial structure of the test products could be related to the pre-cecal P digestibility of the same products. Diets met or exceeded CVB (2011) requirements for all nutrients except for P and were formulated to contain a calcium to total P ratio of between 1.4 and 1.6 and a minimal amount of phytate P. Diets contained 5 g/kg titanium oxide as a marker to determine digestibility of P. At d 24 all birds were euthanized, after which the content of the terminal part of the ileum was sampled. The P digestibility was calculated by linear regression according to World's Poultry Science Association (WPSA) protocol for determination of pre-cecal P digestibility. Pre-cecal P digestibility of MCP, DCP, Delfos, Calfos, and porcine bone meal was 88.5, 82.4, 94.5, 86.9, and 78.2%, respectively. Based on visual inspection of electron microscopy images of test products, the spatial structure of the test products might be related to P digestibility. It is concluded that processing of bone meal increases the pre-cecal P digestibility in broilers.

To sustainably contribute to food security of a growing and richer world population, livestock production systems are challenged to increase production levels while reducing environmental impact, being economically viable, and socially responsible. Knowledge about the sustainability performance of current livestock production systems may help to formulate strategies for future systems. Our study provides a systematic overview of differences between conventional and organic livestock production systems on a broad range of sustainability aspects and animal species available in peer-reviewed literature. Systems were compared on economy, productivity, environmental impact, animal welfare and public health. The review was limited to dairy cattle, beef cattle, pigs, broilers and laying hens, and to Europe, North America and New Zealand. Results per indicators are presented as in the articles without performing additional calculations. Out of 4171 initial search hits, 179 articles were analysed. Studies varied widely in indicators, research design, sample size and location and context. Quite some studies used small samples. No study analysed all aspects of sustainability simultaneously. Conventional systems had lower labour requirements per unit product, lower income risk per animal, higher production per animal per time unit, higher reproduction numbers, lower feed conversion ratio, lower land use, generally lower acidification and eutrophication potential per unit product, equal or better udder health for cows and equal or lower microbiological contamination. Organic systems had higher income per animal or full time employee, lower impact on biodiversity, lower eutrophication and acidification potential per unit land, equal or lower likelihood of antibiotic resistance in bacteria and higher beneficial fatty acid levels in cow milk. For most sustainability aspects, sometimes conventional and sometimes organic systems performed better, except for productivity, which was consistently higher in conventional systems. For many aspects and animal species, more data are needed to conclude on a difference between organic and conventional livestock production systems.

1. In poultry investigations, the main interest is often to study the effects of many factors simultaneously. Two or three level factorial designs are the most commonly used for this type of investigation. However, it is often too costly to perform when number of factors increase. So a fractional factorial design, which is a subset or a fraction of a full factorial design, is an alternative. The Taguchi method has been proposed for simplifying and standardising fractional factorial designs. 2. An experiment was conducted to evaluate the applicability of the Taguchi method to optimise in vitro intrinsic phytase activity (IPA) of rye, wheat and barley under different culture conditions. 3. In order to have a solid base for judging the suitability of the Taguchi method, the results of the Taguchi method were compared with those of an experiment that was conducted as a 34 full factorial arrangement with three feed ingredients (rye, wheat and barley), three temperatures (20 degrees C, 38 degrees C and 55 degrees C), three pH values (3.0, 5.5 and 8.0) and three incubation times (30, 60 and 120 min), with two replicates per treatment. 4. After data collection, a Taguchi L 9 (3(4)) orthogonal array was used to estimate the effects of different factors on the IPA, based on a subset of only 9 instead of 81 treatments. The data were analysed with both Taguchi and full factorial methods and the main effects and the optimal combinations of these 4 factors were obtained for each method. 5. The results indicated that according to both the full factorial experimental design and the Taguchi method, the optimal culture conditions were obtained with the following combination: rye, pH = 3, temperature = 20 degrees C and time of incubation = 30 min. The comparison between the Taguchi and full factorial results showed that the Taguchi method is a sufficient and resource saving alternative to the full factorial design in poultry science.

The aim of this study, comprising two experiments, was (1) to determine in Experiment 1 the relationship of incremental dietary P (phosphorus) content on precaecal digestible P in male broilers and (2) to determine in Experiment 2 the precaecal P digestibility of various inorganic P sources at marginal levels of P supply.In Experiment 1, a total of 260 male Ross 308 broilers were divided into groups of 10 birds per pen resulting in 8 replicates for treatment 1 and 6 replicates for treatments 2–4. Experimental diets were formulated to contain 4 incremental concentrations of digestible P by means of increasing concentrations of monocalcium phosphate (MCP). In the second experiment, 480-d-old male Ross 308 broilers were divided in groups of 12 birds per pen resulting in 16 replicates for the basal diet and 6 replicates for each test diet. A total of 4 inorganic P sources, MCP, monodicalcium phosphate (MDCP), dicalcium phosphate (DCP) and defluorinated phosphate (DFP) were added to the basal diet to determine the precaecal P digestibility. Three of the 4 inorganic P sources (MCP, MDCP and DCP) represented a mix of batches from different producers. At the end of both experiments, the chyme of the posterior part of the small intestine was collected. Digestibility of P and Ca was determined using titanium dioxide as indigestible marker.In Experiment 1, a reduction in precaecal digestibility of P was observed above an estimated precaecal digestible dietary P concentration of 4.8 g/kg.The precaecal P digestibility of the tested inorganic P sources in Experiment 2 was 78.3% for MCP, 59.0% for DCP, 70.7% for MDCP and 31.5% for DFP.

Sustainable livestock production systems are needed to feed the larger, more urban, richer and older world population in 2050. Quantitative information about the sustainability performance of existing livestock production systems can aid the debate of which actions could be developed and implemented. Strong points of conventional and organic dairy cattle, beef cattle, pig, laying hen, and broiler production systems were identified in peer-reviewed literature for a limited number of sustainability indicators within the subjects of economy, productivity, environment, animal welfare, and public health. This study aims to identify lessons learned for sustainable livestock production.

The purpose of this experiment was to evaluate the effects of five nutritional interventions, provided during d 14 – 28, including inclusion of a plant extract (quercetin); an insoluble fiber (oat hulls); a prebiotic (β- glucan); an anti-microbial protein (lysozyme), and ω-3 fatty acids from fish oil, on growth performance, composition of the intestinal microbiota, and morphology and gene expression of small intestine of broilers. Despite the different types of interventions, parameters related to immune competence were only marginally affected by the tested products. It seemed that in this study inclusion of oat hulls, and probably β-glucans, had perspective to improve immune competence. It is recommended to revaluate some of the tested interventions, especially dietary inclusion of oat hulls and β-glucans, in broilers starting from day-old onward.

1. The objective of this experiment was to study the influences of xylanase and citric acid on the performance, nutrient digestibility, digesta viscosity, duodenal histology, and gut microflora of broilers fed on a wheat based diet. 2. The experiment was carried out as a 2 × 3 factorial arrangement with two concentrations of xylanase (0 and 200 mg/kg) and three concentrations of citric acid (0, 20 and 40 g/kg). A total of 408 one-day-old chickens with similar body weight were distributed into 24 pens with 17 birds/pen. Each dietary treatment was given to 4 replicate pens from 0 to 24 d of age. To determine the apparent nutrient digestibility, chromic oxide (3 g/kg) was added to the diets as an indigestible marker. 3. Xylanase significantly increased body weight gain at 24 d of age by 1·4% and improved gain-to-feed (G:F) by 3·6%. The inclusion of 40 g/kg citric acid decreased feed intake and body weight gain by 15·4% and 11·8%, respectively. The inclusion of 20 g/kg of citric acid decreased feed intake, but it did not affect body weight gain of broilers at 24 d of age. The inclusion of 20 and 40 g/kg citric acid improved G:F by 3·8 and 4·3% respectively. Xylanase significantly decreased the viscosity of digesta and improved retention of DM, CP, and energy. 4. Xylanase and citric acid did not have any effect on the histo-morphology of the duodenum and intestinal microbial population. 5. In conclusion, citric acid at 20 g/kg decreased feed intake, did not have a negative effect on body weight gain, and improved G:F. Xylanase decreased digesta viscosity, increased nutrient retention and consequently improved performance of broilers fed on a wheat based diet.

An experiment was performed to investigate the effect of animal versus vegetable protein sources in the diet on the development of behavior in laying hens. A diet containing protein sources of only vegetable origin was compared with four diets, each containing one of four processed animal proteins (PAPs). Two PAPs (Daka-58 and Sonac-60) were classified as meat meals, whereas the remaining ones (Daka-40 and Sonac-50) were classified as meat and bone meals. The impact of a control diet (without PAP) versus four PAP diets (50 g/kg CP of animal origin) on behavior was determined. All diets were isocaloric (AME n = 11.8 MJ/kg) and isonitrogenous (dig. lysine = 6.8 g/kg). Hens were housed in 40 floor pens (12 hens/pen, 8 pens/treatment) from 20 to 40 weeks of age. Supplementation of PAPs did not generally reduce feather pecking behavior. Nevertheless, Daka-40 and Sonac-50 fed hens showed a delay in the development of feather damage and, simultaneously, an increase in litter condition, foraging and walking behavior, and floor pecks compared to hens fed Sonac-60. These shifts seemed to be partly related with the intake of digestible glycine, available phosphorus, calcium, potassium, and sodium.

Organic and many ‘low input’ production standards for pigs require outdoor access, and as a consequence expose the animals to a wide range of potential endo- and ectoparasite infection sources. Conventional anthelmintics are used to control parasitic infections, but their preventive use is banned by the organic standards. The present paper investigates the potential of prevention of infection through better hygiene. Attempts were made to break the infection cycle through thorough pen cleaning 10 weeks after the pigs had been introduced to the pen. Although pen fouling can be reduced, the level of roundworm (Ascaris suum) infection was not reduced. Regular deworming with conventional medication is still required in addition to good hygiene.

1. The main dietary challenge in organic laying hen production is to fulfil the digestible methionine (MET) requirement in a diet consisting of ingredients of organic origin only. 2. The aim of the present experiment was to determine the response of organic housed laying hens (26-34 weeks of age) to dietary energy and MET during a summer and winter trial. Per trial, a total of 128 17-week-old Brown Nick hens were allotted to 16 pens, which were connected to an outdoor run. Each experiment comprised 8 dietary treatments according to a 4 × 2 factorial design. The factors were AFD MET level (2.3, 2.7, 3.1 and 3.5 g/kg) and energy content (10.9 and 12.1 MJ). 3. Dietary energy content did not affect energy intake (1361 kJ/d) in summer, whereas energy intake in winter was increased in hens that were fed on the 12.1-MJ diets (1514 vs. 1421 kJ/d). Maximal egg mass in summer was achieved if a diet with 3.5 g/kg MET was given, corresponding to a digestible MET intake of 421 mg/d. During winter, maximal egg mass was achieved with a digestible MET intake of 360 mg/d, which was already realised with a MET content of 2.7 g/kg. 4. Because digestible MET content for maximal egg performance differed between the summer and winter trial, dietary energy to MET ratio might be adjusted to seasonal conditions.

The objective of this study was to determine the effects of different growth patterns and dietary crude protein levels during rearing in broiler breeder females on fertility, hatchability, embryonic mortality, and offspring performance. A 2 × 3 factorial arrangement of treatments was used, with 2 growth patterns to reach a target body weight at 20¿wk of age of 2,200 g (standard = standard growth pattern) or 2,400 g (high = high growth pattern), and 3 dietary protein levels (high = crude protein, high), (medium = crude protein, medium), and low = crude protein, low). Fresh egg composition and organ development in hatchlings were determined. Offspring of the different groups were reared until an age of 34 d and feed intake, body weight gain, mortality, and carcass composition were determined. In 29-wk-old high growth pattern breeders compared to standard growth pattern breeders, fertility and hatchability of set eggs were increased; embryonic mortality between d 1 and 9 was decreased whereas hatchability of fertile eggs was not affected. Breeders fed the medium crude protein diet showed a decreased hatchability of fertile eggs caused by an increased embryonic mortality between d 18 and 21 compared to breeders fed the high crude protein and low crude protein diets. Offspring of 29-wk-old high growth pattern breeders tended (P = 0.059) to have a higher body weight at d 34 than offspring of standard growth pattern breeders, which was achieved by a tendency to a higher body weight gain (P = 0.057). Offspring of breeders fed the medium and low crude protein diet showed a higher feed intake between d 18 and 27 and during the total growth period, as compared to offspring of high crude protein breeders. Male broilers of low crude protein breeders had higher breast meat yield than male broilers of high crude protein breeders, while breast meat yield of female broilers was not affected by dietary protein levels. This experiment showed that a higher growth pattern during the rearing period increased fertility, decreased embryonic mortality, and improved offspring performance in young breeders, whereas decreased dietary protein level had no or less pronounced effects on these traits.

High growth rates in modern-day broilers require diets concentrated in digestible protein and energy. In addition to affecting feed conversion efficiency, it is important to prevent surplus dietary protein because of greater amounts of undigested protein entering the hindgut that may be fermented by the resident microbiota. The latter may result in increased formation of a wide range of protein-derived compounds including ammonia, amines, indoles and phenols, in addition to secondary products (lactate, succinate) and gases such as methane, hydrogen and carbon dioxide. In poultry, studies have shown the presence of protein fermentation products such as biogenic amines and branched chain fatty acids (BCFA) in the ileal and caecal digesta. The production and metabolism of nitrogenous waste products (as a result of protein fermentation) such as uric acid and ammonia may lead to a burden on the organism and cause additional energy losses. Although biogenic amines are important for normal gut development, greater concentrations may cause gizzard erosion, mortality and depressed growth rate in broilers. A decrease in indigestible protein reduces hindgut protein fermentation. In broilers, feeding diets with coarse particles (between 600 to 900 µm) and/or using feed additives, such as pre- and probiotics and organic acids, especially butyric acid, may improve protein digestion, thereby, potentially reducing hindgut protein fermentation. Studies are therefore needed to determine the extent and importance of hindgut protein fermentation on performance and gut health in broilers.

In the near future EU-legislation will ban the use of conventional battery cages, while national legislation in some countries in Western Europe will ban beak trimming as well. The ban on battery cages and beak trimming causes an increased risk of feather pecking and cannibalism in laying hens. Many factors influence feather pecking behaviour, but this paper focuses on nutritional factors. Nutritional factors can have positive and negative effects on feather pecking behaviour in laying hens. Severe feather pecking has been demonstrated in birds that were fed a too low mineral level in the diet, a too low protein level or a too low amino acid level (methionine, arginine). Sometimes somewhat more feather pecking was found when layers were fed diets with mainly vegetable protein sources as compared with diets with protein from animal origin. Also more feather pecking may occur when the diets were fed restrictedly, fed coarsely ground, or fed as pellets. Feeding high-fibre diets, low energy diets, or roughages reduced feather pecking. Providing additional grain or straw in the litter during rearing could result in lower levels of feather pecking behaviour in adult stages. Some of these positive effects on feather pecking seem to be related to the time birds spend on feed intake and foraging. This paper gives an overview of the relationships between the occurrence of feather pecking behaviour and nutritional factors, such as diet composition and feeding strategies in laying hens.

Free range and organic systems expose the laying hen more to unexpected events and adverse climatic conditions than barn and cage systems. In France, The Netherlands and Switzerland the requirements for a hen suitable to produce in free range and organic systems were discussed with farmers. The farmers preferred for these systems a more ‘robust’ hen, more specifically defined as a heavier hen with good eating capacity. Benchmarking of flocks in a web-based management program in The Netherlands from layer flocks finished in 2008 – 2013 indicated that in earlier years indeed mortality among organic and to a lesser extent free range hens was higher than among barn or cage hens. Feed conversion (kg feed/kg eggs) is higher, but the gap is closing. Improvements in management of the hens during rearing and in the layer phase in free range and organic systems seem to be important. Breeding companies take behaviour and performance in non-cage systems into account in their selection programs. Heavier hens need a diet with a lower protein to energy ratio. From model calculations we concluded that in organic systems a heavier hen might be economically profitable, as total feed costs are lower for the heavier hen then for a hen with a lower body weight requiring a diet with a high protein content. For conventional free range hens this is not the case as then the protein content can be adapted by synthetic amino acids. Field studies and cooperation between farmers and breeding organisations will have to show if a strain of heavier hens will be successful in the rather small organic market.

The objective of this research was to assess the potential to reduce the integral ecological impact (i.e. impact along the egg production chain per kg egg) of Dutch organic egg production by replacing currently used imported diet ingredients with Dutch diet ingredients. We realized this objective by comparing the life cycle assessments (LCA) of current Dutch organic egg production, i.e. base situation (B) with different scenarios. In each scenario, one imported diet ingredient was replaced with a diet ingredient produced in the Netherlands. Finally, we formulated a scenario in which several ingredients, that individually resulted in the lowest mean change in ecological impact along the organic egg production chain, were replaced simultaneously. We included differences between production chains in cultivation (i.e. field operation, manure application and yield), transport, feed intake, egg production and N excretion. Replacement of Ukrainian wheat with Dutch triticale, and of Brazilian soybeans, Italian sunflower seed expeller and German peas with Dutch rapeseed expeller reduced the integral ecological impact compared with current organic egg production. Simultaneous replacement of these ingredients (scenario MU) resulted in an overall lower and more balanced reduction of the different ecological impacts (41–101%) than single replacement of these ingredients (41–215%). Compared with B ecological impact of scenario MU decreased for global warming potential (91%), energy use (79%), land occupation (68%), acidification potential (99%), N deficit (85%), P deficit (41%) and P surplus (81%), but slightly increased for N surplus (101%). The low ecological impact of MU was explained by (1) a relative small increase in feed conversion ratio (from 2.32 for B to 2.37 for MU), (2) a reduction of the transport distance of 44.4% of the diet ingredients, (3) replacement of the currently used crops with crops that have a higher yield in combination with a balanced applied amount of N and P in manure, and (4) use of expeller instead of whole ingredients.

Three experiments were conducted to evaluate the effects of temperature ( T ), pH, time of incubation and pepsin on the stability of intrinsic phytase of different cereals. Experiment one was conducted as a 3×4×3×3 factorial arrangement with three feed ingredients (rye, wheat and barley), four T (20, 38, 55 and 80 °C), three pH levels (3.0, 5.5 and 8.0) and three incubation times (30, 60 and 120 min), with two replicates per treatment. Stability was calculated as the ratio of the residual phytase activity of a treated sample to the non-treated (reference sample) times 100. Phytase activity of the reference samples of rye, wheat and barley was 3.14, 1.77 and 0.66 FTU/g, respectively. Overall, rye showed the highest and barley the lowest stability (0.58 vs. 0.47, P T to 0.07 at 80 °C across ingredients, pH levels and time of incubation (P vs. 0.34 across ingredients, T and time of incubation, P 0.90). Wheat and rye phytases were stable at pH 3.0 and 5.5 (20 and 38 °C). In experiment two, the effect of shorter period of time (10 and 30 min) was assessed on the stability of cereal phytases. Barley phytase showed the highest residual phytase activity among cereals at 65 °C. In experiment three, stability of intrinsic phytase of these feed ingredients was determined after incubation in different concentrations of pepsin (0, 5 and 10 mg/mL) at pH 2.0. Intrinsic phytases of wheat and rye were resistant to pepsin, but barley phytase was susceptible to pepsin and its stability decreased to 0.57 after pre-incubation for 60 min in 5 mg pepsin/mL. This knowledge regarding the effect of T , incubation time and pH on stability of cereal intrinsic phytases may contribute to optimize available P contents of diets, thereby reducing phosphorus excretion of monogastrics.

An experiment was conducted with 768 non-cage-housed ISA Brown pullets, of which 576 hens were followed during the laying period, to investigate the separate effects of dietary energy dilution and non-starch polysaccharides (NSP) concentration (oat hulls as NSP source) on eating behavior and feather damage. Day-old pullets were allotted to 1 of 6 dietary treatments according to a 3 x 2 factorial arrangement (3 dilution and 2 NSP levels), with 8 replicates (pens) per treatment. At 17 wk of age, pens with hens were allotted to 1 of 8 dietary treatments according to a 4 x 2 factorial arrangement (4 dilution and 2 NSP levels), with 6 replicates per treatment. Compared with 0% dilution level, feed intake of laying hens of 10, 15, and 20% dilution levels increased by 8.4% (9.5 g/hen per d), 16.5% (18.1 g/hen per d), and 20.9% (23.6 g/hen per d), respectively. The ME(n) intake was similar for all dilution levels. Hens fed standard-NSP laying diets had similar insoluble NSP intake for all dilution levels (9.3 g/hen per d). Insoluble NSP intake of hens fed high-NSP laying diets increased from 15.6 g/hen per day (0% dilution) to 18.9 g/hen per day (20% dilution). Providing high- vs. standard-NSP layer diet decreased relative proventriculus contents (1.1 vs. 0.3 g/kg of BW) and increased empty gizzard weight (14.3 vs. 24.4 g/kg of BW). Hens that were fed standard-NSP diets had more feather damage compared with hens fed high-NSP diets (0.58 vs. 0.30 arbitrary units). Increasing the insoluble NSP intake resulted in decreased proventricular weight and increased gizzard weight and its contents, which are indicators of improved functioning of the gut, thereby linearly reducing feather damage. Providing diluted rearing diets increased feed intake from the first weeks of life onwards. It was hypothesized that pullets were increasingly "imprinted" on feed as pecking substrate if dilution level increased. This may decrease feather pecking and could explain the improved feather condition at 49 wk of age when 15% diluted rearing diet was fed.

International audience; 1. The aim of this study was to assess the feasibility of 100% organic feed for organic broilers by comparing it with 80% organic feed (situation at the time of the experiment; 2004) and 95% organic feed (alternative). 2. Diets were optimised for nutritional value, allowing a maximum 10% increase in feed price when using 100% organic feedstuffs. This could only be achieved at the expense of the methionine content. 3. The broilers were reared from zero to three weeks of age in a broiler house in three groups of 500 broilers each on either an 80-, a 95-, or a 100% organic starter diet. At three weeks of age, the broilers were transferred to 15 pens with an outdoor run. Each treatment group of 500 broilers was divided into five groups of 95 broilers and fed an 80-, a 95, or a 100% organic finisher diet. 4. Broilers that received 100% organic feed reached a lower body weight and grew slower than broilers that received 95% organic feed, caused mainly by a lower feed intake. 5. Broilers that received 95 or 100% organic feed had a higher incidence of breast blisters than broilers that received 80% organic feed. 6. The cost price for meat from broilers that received 80% organic feed was € 1.83 per kg live weight. The cost prices for broilers that received 95 and 100% organic feed were € 1.84 (+0.8%) and € 1.93 (+5.4%) per kg live weight respectively. 7. In conclusion, 95% organic feed led to a better performance than 100% organic feed in this study. Probably, the lower methionine content in the 100% organic feed negatively affected performance. The results for 95% organic feed were similar to 80% organic feed, except for a higher incidence of breast blisters.

An experiment was conducted with 504 non-cage-housed ISA Brown laying hens from 18 to 40 wk of age to investigate the separate effects of dietary energy concentration, nonstarch polysaccharide (NSP) concentration, and particle sizes of added NSP source on the eating behavior, feather-pecking behavior, and hen performance of laying hens. Hens were allotted to 1 of 6 dietary treatments according to a 2 x 3 factorial arrangement, with 7 replicates per treatment. The factors were control and low energy concentration (2,825 vs. 2,540 kcal/kg), control and high NSP concentration (133 vs. 195 g/kg), and fine vs. coarse particle size of the added NSP source in the high-NSP diets. We hypothesized that eating time would be increased by feeding low-energy diets or coarsely ground, high-NSP diets, or both, resulting in reduced feather-pecking behavior, without negatively affecting hen performance. Energy reduction, NSP addition, and coarse grinding of NSP increased eating time by 14.2% (P = 0.001), 17.2% (P < 0.001), and 7.9% (P = 0.075), respectively, compared with the control level of these factors. Addition of NSP decreased eating rate (g/min) by 21.0% (P = 0.010). Layers already performed gentle feather-pecking behavior during the fifth week of the rearing period. Dietary treatments did not affect the maximal level of feather condition scores, but arise of feather damage was delayed by 10 wk in hens fed low-energy, coarsely ground, NSP-rich diets compared with hens fed control diets. Hens fed the control NSP diets showed reduced culling rates, because of less cannibalistic pecking, when energy concentration was decreased (44.1 vs. 13.1%), whereas in the high-NSP diets, culling rate decreased slightly when hens were fed the low-energy diets (31.6 vs. 28.6%; P = 0.071). Hens that were fed the low-energy diets compensated for the 10% reduction in energy concentration by a 9.3% higher maximal feed intake (143.0 vs. 130.8 g/d). Hen performance and BW gain of the hens were not affected by dietary treatments. We concluded that hens that were fed low-energy or high (coarsely ground)-NSP diets spend more time on feed intake, compared with hens that were fed the control diets. As a result, hens in some treatments showed less feather-pecking behavior.

1. An experiment with 480 ISA Brown layers was conducted to measure the effect of dietary energy ( 11.8, 11.2 and 10.6 MJ/kg) and non-starch polysaccharides ( NSP) ( 128, 146 and 207 g/kg) concentration, soluble NSP content ( 64 and 85 g/kg), particle size distribution of the NSP fraction ( fine and coarse) and feed form ( mash and crumble) on feed intake, eating time and egg performance of laying hens in early lay ( from 18 to 26 weeks of age). Twelve experimental diets were tested, each replicated 4 times. 2. Laying hens in early lay that were fed low- or high-NSP diets were able to compensate for 10% dietary dilution by 9.5 and 4.9% higher feed intakes, respectively. Feeding crumble or coarsely ground mash did not affect feed intake. 3. Eating time of the hens fed the undiluted diets increased over the experimental period from 16.4 to 24.6% of the observation period, but was not affected by sand or grit addition, particle size distribution or feed form. Feeding high-NSP diets increased eating time by 22%. 4. Egg performance and body weight gain of the hens that were fed low- NSP or high-NSP diets were similar or better compared to the undiluted diets, whereas coarse grinding of the diets showed 7 to 10% lower egg performance and weight gain. Egg performance and weight gain were not affected by feed form. 5. It is concluded that hens in early lay, fed energy-diluted diets, by adding sand or grit ( low-NSP) or NSP-rich raw materials ( high-NSP) to the control diet, were able to increase their feed intake, resulting in energy intake and egg performance comparable to the control group. Supplementing diets with insoluble NSP also decreased eating rate. Prolonged eating time using insoluble NSP could be useful in reducing feather pecking behaviour.

Improving dietary phosphorus (P) absorption and retention has been intensively studied in pig and poultry due to the low digestibility of inositol phosphate (IP), global mineral P scarcity and increasing public concerns over environment pollution. The main aim of this thesis was to provide novel insights into calcium (Ca) and P absorption, metabolism and retention in pigs and poultry.The impact of dietary Ca content with or without microbial phytase supplementation on Ca and P absorption/solubilization in different digestive tract segments was studied in pigs. Increasing dietary Ca content reduced apparent P digestibility in all digestive tract posterior to stomach, and this impact was greater for the phytase supplemented diets in the distal ileum. Moreover, incremental dietary Ca content reduced P solubility, accompanied with a reduced IP6 degradation in the distal ileum. Thus dietary Ca reduced P absorption via reducing IP6 degradation and precipitation of P, which was more pronounced in microbial phytase included diets. Furthermore, a high dietary Ca content reduced mRNA expression of Ca-related transporters in the colon and jejunum, while it increased mRNA expression of Ca-related claudins in the jejunum. These results indicated that increasing dietary Ca supply switched Ca absorption from transcellular to paracellular pathway. In addition to that, dietary Ca reduced mRNA expression of Ca-related transporters and claudins in the kidney, suggesting that kidney played a central role in Ca and P homeostasis.In contrast to pigs, the negative impact of dietary Ca on P absorption was less pronounced in broilers fed diets supplemented with microbial phytase. Microbial phytase supplementation also increased Ca absorption particularly in the low-Ca diets. However, this positive impact was insufficient to restore the negative effect of Ca deficiency on growth performance or tibia breaking strength. Moreover, incremental dietary Ca supply reduced mRNA expression of both Ca-related transporters and claudin in the duodenum, while upregulated their expression in the kidney. These results suggested that kidney might not play a central role in Ca and P homeostasis.The impact of limestone particle size and inclusion level on Ca and P absorption was studied in broilers. Fine was more digestible than coarse limestone in the jejunum, but this difference disappeared in the ileum particularly at a low Ca intake. Irrespective of limestone particle size, minimal requirement of Ca/P was 1.00-1.25 to optimize Ca and P digestibility without compromising tibia breaking strength. Moreover, P digestibility in the ileum was gradually decreased with incremental Ca intake. The P solubility in the crop, gizzard and jejunum, however, was not affected by limestone particle size or inclusion level. Furthermore, mRNA expression of P-related transporter in both duodenum and jejunum was downregulated with increasing Ca intake. Thus Ca-induced downregulation of P transporter was an important mechanism by which dietary Ca reduced P absorption. Apart from that, mRNA expression of Ca- and P-related transporters in the duodenum was downregulated by dietary Ca intake in a limestone particle size dependent manner.In conclusion, in pigs incremental dietary Ca content reduces intestinal P absorption via hampering IP degradation and precipitation of P, with a larger impact in microbial phytase-supplemented diets. Increasing dietary Ca content shifts intestinal Ca absorption from transcellular to paracellular pathway, and kidney plays a central role in whole body Ca homeostasis. By contrast, in broilers incremental dietary Ca content reduces intestinal P absorption, which was more pronounced in phytase-free diets. Furthermore, Ca-induced downregulation of P transporters is an important mechanism by which dietary Ca reduces intestinal P absorption. Overall, insights obtained in poultry studies cannot be extrapolated to pigs and vice verse when it comes to Ca and P homeostasis.