Modelling phosphorus intake,digestion, retention and excretion in growing and finishing pigs: model description

Low phosphorus (P) digestibility combined with intensive pig production can increase P diffuse pollution and environmental load. The aim of this paper was to develop a deterministic, dynamic model able to represent P digestion, retention and ultimately excretion in growing and finishing pigs of different genotypes, offered access to diets of different composition. The model represented the limited ability of pig endogenous phytase activity to dephosphorylate phytate as a linear function of dietary calcium (Ca). Phytate dephosphorylation in the stomach by exogenous microbial phytase enzymes was expressed by a first order kinetics relationship. The absorption of non-phytate P from the lumen of the small intestine into the blood stream was set at 0.8 and the dephosphorylated phytate from the large intestine was assumed to be indigestible. The net efficiency of using digested P was set at 0.94 and assumed to be independent of BW, and constant across genotype and sex. P requirements for both maintenance and growth were made simple functions of body protein mass, and hence functions of animal genotype. Undigested P was assumed to be excreted in the feaces in both soluble and insoluble forms. If digestible P exceeded the requirements for P then the excess digestible P was excreted through the urinary flow; thus the model represented both forms of P excretion (soluble and insoluble) into the environment. Using a UK industry standard diet, model behaviour was investigated for its predictions of P digestibility, retention and excretion under different levels of inclusion of microbial phytase and dietary Ca, and different non-phytate P : phytate ratios in the diet, thus covering a broad space of potential diet compositions. Model predictions were consistent with our understanding of P digestion, metabolism and excretion. Uncertainties associated with the underlying assumptions of the model were identified. Their consequences on model predictions, as well as the model evaluation are assessed in a companion paper.     

Meta-analysis of phosphorus utilization by growing pigs: effect of dietary phosphorus,calcium and exogenous phytase

Optimizing phosphorus (P) utilization in pigs requires improving our capacity to predict the amount of P absorbed and retained, with the main modulating factors taken into account, as well as precisely determining the P requirements of the animals. Given the large amount of published data on P utilization in pigs, a meta-analysis was performed to quantify the impact of the different dietary P forms, calcium (Ca) and exogenous phytases on the digestive and metabolic utilization criteria for dietary P in growing pigs. Accordingly, the amount of phytate P (PP) leading to digestible P (g/kg) was estimated to be 21%, compared with 73% for non-phytate P (NPP) from plant ingredients and 80% for NPP from mineral and animal ingredients (P < 0.001). The increase in total digestible dietary P following the addition of microbial phytase (PhytM) from Aspergillus niger (P < 0.001) was curvilinear and about two times higher than the increase following the addition of plant phytase, which leads to a linear response (P < 0.001). The response of digestible P to PhytM also depends on the amount of substrate, PP (PhytM² × PP, P < 0.001). The digestibility of dietary P decreased with dietary Ca concentration (P < 0.01) independently of phytase but increased with body weight (BW, P < 0.05). Although total digestible dietary P increased linearly with total NPP concentration (P < 0.001), retained P (g/kg), average daily gain (ADG, g/day) and average daily feed intake (ADFI, g/day) increased curvilinearly (P < 0.001). Interestingly, whereas dietary Ca negatively affected P digestibility, the effect of dietary Ca on retained P, ADG and ADFI depended on total dietary NPP (NPP × Ca, P < 0.01, P < 0.05 and P < 0.01, respectively). Increasing dietary Ca reduced retained P, ADG and ADFI at low NPP levels, but at higher NPP concentrations it had no effect on ADG and ADFI despite a positive effect on retained P. Although the curvilinear effect of PhytM on digestible P increased with PP (P < 0.001), this effect was lessened by total NPP for ADG and ADFI (PhytM × NPP and PhytM² × NPP, P < 0.05) and depended on both total NPP and Ca for retained P (PhytM² × NPP × Ca, P < 0.01). This meta-analysis improves our understanding of P utilization, with major modulating factors taken into account. The information generated will be useful for the development of robust models to formulate environmentally friendly diets for growing pigs.     

The role of fish in distribution and germination of seeds of the submerged macrophytes Najas marina L. and Ruppia maritima L.

Summary The effects of three species of fish (tilapia, grass carp and common carp) on the seeds of Najas marina L. and of Ruppia maritima L. were investigated. Practically all the seeds that were injested by the common carp were digested. The two other fish were less affective: they digested seeds with soft seed-coats but excreted a good portion of the hard ones. Germination of the excreted seeds was improved. Seeds have been retained in the digestion tracts of the fish for up to 65 h. It is thus suggested that tilapias and grass-carps play a role in the distribution and the improvement of reproduction of Najas and Ruppia.     

Quantifying the consequences of nutritional strategies aimed at decreasing phosphorus excretion from pig populations: a modeling approach

There is a global imperative to reduce phosphorous (P) excretion from pig systems. In this study, a previously validated deterministic model was modified to be stochastic, in order to investigate the consequences of different management strategies on P excretion by a group of growing pigs. The model predicts P digestion, retention and excretion from feed composition and growth parameters that describe a specified pig phenotype. Stochasticity was achieved by introducing random variation in the latter. The strategies investigated were: (1) changing feed composition frequently in order to match more closely pig digestible P (digP) requirements to feed composition (phase feeding) and (2) grouping pigs into light and heavy groups and feeding each group according to the requirements of their group average BW (sorting). Phase feeding reduced P excretion as the number of feeding phases increased. The effect was most pronounced as feeding phases increased from 1 to 2, with a 7.5% decrease achieved; the increase in phases from 2 to 3 was associated with a further 2.0% reduction. Similarly, the effect was more pronounced when the feed targeted the population requirements for digP at the average BW of the first third, rather than the average requirements at the mid-point BW of each feeding sequence plan. Increasing the number of feeding phases increased the percentage of pigs that met their digP requirements during the early stages of growth and reduced the percentage of pigs that were supplied <85% of their digP requirements at any stage of their growth; the latter may have welfare implications. Sorting of pigs reduced P excretion to a lesser extent; the reduction was greater as the percentage of pigs in the light group increased from 10% to 30% (from 1.5% to 3.0% reduction, respectively). This resulted from an increase in the P excreted by the light group, accompanied by a decrease in the P excreted by the remaining pigs. Sorting increased the percentage of light pigs that met their dig P requirements, but only slightly decreased the percentage of heavy pigs that met these requirements at any point of their growth. Exactly the converse was the case as far as the percentage of pigs that were supplied <85% of their digP requirements were concerned. The developed model is flexible and can be used to investigate the effectiveness of other management strategies in reducing P excretion from groups of pigs, including precision livestock feeding.     

True phosphorus digestibility and the endogenous phosphorus outputs associated with brown rice for weanling pigs measured by the simple linear regression analysis technique

The objectives of this study were to determine true phosphorus (P) digestibility, degradability of phytate-P complex and the endogenous P outputs associated with brown rice feeding in weanling pigs by using the simple linear regression analysis technique. Six barrows with an average initial body weight of 12.5 kg were fitted with a T-cannula and fed six diets according to a 6 × 6 Latin-square design. Six maize starch-based diets, containing six levels of P at 0.80, 1.36, 1.93, 2.49, 3.04, and 3.61 g/kg per kg dry-matter (DM) intake (DMI), were formulated with brown rice. Each experimental period lasted 10 days. After a 7-day adaptation, all faecal samples were collected on days 8 and 9. Ileal digesta samples were collected for a total of 24 h on day 10. The apparent ileal and faecal P digestibility values of brown rice were affected ( P < 0.01) by the P contents in the assay diets. The apparent ileal and faecal P digestibility values increased from − 48.0 to 36.7% and from − 35.6 to 40.0%, respectively, as P content increased from 0.80 to 3.61 g/kg DMI. Linear relationships ( P < 0.05), expressed as g/kg DMI, between the apparent ileal and faecal digestible P and dietary levels of P, suggested that true P digestibility and the endogenous P outputs associated with brown rice feeding could be determined by using the simple regression analysis technique. There were no differences ( P>0.05) in true P digestibility values (57.7 ± 5.4 v. 58.2 ± 5.9%), phytate P degradability (76.4 ± 6.7 v. 79.0 ± 4.4%) and the endogenous P outputs (0.812 ± 0..096 v. 0.725 ± 0.083 g/kg DMI) between the ileal and the faecal levels. The endogenous faecal P output represented 14 and 25% of the National Research Council (1998) recommended daily total and available P requirements in the weanling pig, respectively. About 58% of the total P in brown rice could be digested and absorbed by the weanling pig. Our results suggest that the large intestine of the weanling pigs does not play a significant role in the digestion of P in brown rice. Diet formulation on the basis of total or apparent P digestibility with brown rice may lead to P overfeeding and excessive P excretion in pigs.     

Influence of dietary fibre on nutrient digestibility and energy utilisation in growing pigs fed diets varying in soluble and insoluble fibres from co-products

The co-products from the industry are used to reduce costs in pig diets. However, the co-products used in pig diets are limited because of a high fibre content which is not digested by endogenous enzymes and is resistant to degradation in the small and large intestines. The aim of this study was to investigate digestibility of nutrients and energy, and energy utilisation in pigs fed diets with various soluble and insoluble dietary fibre (DF) from co-products. The experiment was performed as a 4 × 4 Latin square design (four diets and four periods) using four growing pigs (66.2 ± 7.8 kg) surgically fitted with a T-cannula in the end of the small intestine. The pigs were fed four experimental diets: low-fibre control (LF), high-fibre control (HF), high-soluble fibre (HFS) and high-insoluble fibre (HFI) diets. The apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of ash, organic matter, CP, fat, carbohydrates, starch and non-starch polysaccharides (NSP) divided into cellulose and soluble and insoluble non-cellulosic polysaccharide residues were measured using chromic oxide as marker. The recovery of total solid materials, organic matter and total carbohydrates in ileal digesta in pigs fed the HF and HFS diets was higher than in pigs fed LF and HFI, whereas recovery of organic matter and total carbohydrates in faecal materials in the HFS diet was lowest (P < 0.05). AID of organic matter, total carbohydrates and starch was lowest for HFS diet (P < 0.05). ATTD of organic matter and CP was higher for LF diet compared with other diets (P < 0.05), whereas total NSP, cellulose and non-cellulosic polysaccharides residues were highest for HFS diet (P < 0.05). Lactic acid in ileal digesta was influenced by dietary composition (P < 0.05) whereas neither type nor level of DF affected short chain fatty acids. The digestible energy, metabolisable energy, net energy and retained energy intake were similar among diets without influence of DF inclusion (P > 0.05). The metabolisable energy:digestible energy ratio was lower when feeding the HFS diet because of a higher fermentative methane loss. Faecal nitrogen and carbon were positively correlated with DM intake and insoluble DF in the diets (P < 0.05), but nitrogen and carbon (% of intake) were similar among diets. The present findings suggest that high-DF co-products can be used as ingredients of pig diets when features of DF are considered.     

Fish oil diets alter the phospholipid balance, fatty acid composition, and steroid hormone concentrations in testes of adult pigs

The objective was to determine the effect of long-term dietary supplementation of two types of fish oil on lipid composition and steroidogenesis in adult pig testis. Twenty-four Duroc boars, aged 204.5 ± 9.4 d (body weight 128.1 ± 16.7 kg) received daily 2.5 kg of an iso-caloric basal diet supplemented with: 1) 62 g of hydrogenated animal fat (AF); 2) 60 g of menhaden oil (MO) containing 16% of eicosapentaenoic acid (EPA) and 18% of docosahexaenoic acid (DHA); or 3) 60 g of tuna oil (TO) containing 7% of EPA and 33% of DHA. After these diets were consumed for 7 mo, testicular hormones, phospholipid content, and fatty acid composition of individual phospholipids in testis were determined. Body and reproductive organ weights were not significantly affected by dietary treatments. Testicular tissue from boars fed a TO diet, followed by those receiving MO and AF diets, had the lowest level of phosphatidylethanolamine (TO < MO < AF; P < 0.01) but the highest sphingomyelin (TO > MO > AF; P < 0.01). For each phospholipid, boars fed either the MO or TO diet had increased total omega-3 fatty acids, particularly DHA (P < 0.01), by reciprocal replacement of total omega-6 fatty acids (20:4n-6, 22:5n-6). The MO diet increased EPA more than the other diets. Testicular concentrations of testosterone and estradiol were lower in boars fed a TO diet than a MO diet (P < 0.02). In conclusion, long-term dietary supplementation of fish oil, regardless of the EPA/DHA ratio, modified the fatty acid compositions in testis and affected steroid production of healthy adult boars, which may represent a promising models for future studies on fertility.     

Quantification of Bt-protein digestion and excretion by the primary decomposer Porcellio scaber,fed with two Bt-corn varieties

Despite increasing use and fabrication of new transgenic plants, there are still concerns about a potential accumulation of Bt-proteins in the soils. Even previous studies have revealed that some phytophagous animals ingest and excrete Bt-protein. Neither the digested proportion of Bt-protein nor the potential amount of an insecticidal activity of the feces excreted by soil arthropods is known. For a period of 15?days, we fed the primary decomposer woodlouse Porcellio scaber (Latreille) with leaves of two transgenic Bt-corn varieties (N4640Bt and Max88Bt) and one non-transgenic control variety (N4640). The Bt-protein in the leaves and in feces was quantified using ELISA. The Bt-protein digestion rate was obtained as a ratio of the Bt-protein ingested to the Bt-protein excreted. Additionally we quantified the naturally occurring Bt-protein dissipation in the leaves of the two transgenic corn varieties over a period of 15 days. Finally bioassays using the susceptible species Ostrinia nubilalis (Hübner) (Lepidoptera, Pyralidae) were carried out to determine if the Bt-protein in the decomposer feces is still active. We calculated that P. scaber feeding on N4640Bt corn leaves digests a mean of 61.1±16.8% of the Bt-protein they ingest, while P. scaber feeding on Max88Bt corn leaves digests 80.5±14.4%, which is significantly more (P<0.05). At an average temperature of 18.3°C, the Bt-protein concentration in the leaves shows a rapid and constant Bt-protein decrease of approximately 40±15% per 3?days in both transgenic corn plants. This accumulates to a Bt-protein loss of more than 90% after 15?days. The bioassays indicate that the Bt-protein excreted with the feces is still insecticidally active. Our study suggests that a part of the Bt-protein taken up by primary decomposers is not digested and is released in its active form into the soils. Under the much cooler field conditions in autumn and winter, it stays active and remains available to soil organisms until the next field season.     

Estimation of calcium requirements for optimal productive and reproductive performance,eggshell and tibial quality in egg-type duck breeders

Optimizing the dietary calcium (Ca) level is essential to maximize the eggshell quality, egg production and bone formation in poultry. This study aimed to establish the Ca requirements of egg-type duck breeders from 23 to 57 weeks of age on egg production, eggshell, incubation, tibial, plasma and ovary-related indices, as well as the expression of matrix protein-related genes. Totally, 450 Longyan duck breeders aged 21 weeks of age were allotted randomly into five treatments, each with six replicates of 15 individually caged birds. The data collection started from 23 weeks of age and continued over the following 35 weeks. The five groups corresponded to five dietary treatments containing either 2.8%, 3.2%, 3.6%, 4.0% or 4.4% Ca. The tested dietary Ca levels increased (linear, P <0.01) egg production and egg mass, and linearly improved (P <0.01) the feed conversion ratio (FCR). Increasing the dietary Ca levels from 2.8% to 4.4% increased (P <0.01) the eggshell thickness and eggshell content. The tested Ca levels showed a quadratic effect on eggshell thickness and ovarian weight (P <0.01); the highest values were obtained with the Ca levels 4.0% and 3.6%, respectively. Dietary Ca levels affected the small yellow follicles (SYF) number and SYF weight/ovarian weight, and the linear response (P <0.01) was significant vis-à-vis SYF number. In addition, dietary Ca levels increased (P <0.05) the tibial dry weight, breaking strength, mineral density and ash content. Plasma and tibial phosphorus concentration exhibited a quadratic (P <0.01) response to dietary Ca levels. Plasma calcitonin concentration linearly (P <0.01) increased as dietary Ca levels increased. The relative expression of carbonic anhydrase 2 in the uterus rose (P <0.01) with the increment of dietary Ca levels, and the highest value was obtained with 3.2% Ca. In conclusion, Longyan duck breeders fed a diet with 4.0% Ca had superior eggshell and tibial quality, while those fed a diet with 3.6% Ca had the heaviest ovarian weights. The regression model indicated that the dietary Ca levels 3.86%, 3.48% and 4.00% are optimal levels to obtain maximum eggshell thickness, ovarian weight and tibial mineral density, respectively.     

The welfare of growing pigs in five different production systems: assessment of feeding and housing

Ninety-one farms were visited over a 2-year period to assess the welfare of growing pigs in five different production systems found either in France or in Spain using the Welfare Quality® protocol. This study focused on animal-based measures as indicators of ‘good feeding’ and ‘good housing’. Multiple Generalized Linear Mixed Models were performed for each measure to evaluate the differences between production systems and to detect possible causal factors. Pigs in the conventional system presented the lowest prevalence of poor body condition, whereas extensive Mallorcan Black pigs and extensive Iberian pigs were associated with a decreased prevalence of bursitis and pig dirtiness. The straw-bedded system presented a lower prevalence of bursitis, but poorer hygiene and more susceptibility of poor body condition than the conventional system. The age of the animals had a significant effect on the appearance of bursitis in the three intensive systems studied. The type of floor was a significant causal factor of bursitis and pig dirtiness in the conventional system and among intensive Iberian pigs. The feeding system was another causal factor of pig dirtiness on more than 50% of the body in the conventional system, whereas pig dirtiness on less than 50% of the body was influenced by the age of the animals. The prevalence of huddling animals in the conventional system was associated with the highest stocking densities and the lowest environmental temperatures. The results indicate that there were important differences between production systems based on animal-based indicators of the good feeding and housing principles. The recording of the age of the animals, type of floor, feeding system, stocking density and environmental temperature can be useful to predict the appearance of a given welfare measure of ‘good housing’ on a farm.     

The effect of CP concentration in the diet on urea kinetics and microbial usage of recycled urea in cattle: a meta-analysis

In ruminants, urea recycling is considered an evolutionary advantage. The amount of urea recycled mainly depends of the nitrogen (N) intake and the amount of organic matter (OM) digested in the rumen. Because recycled N contributes to meeting microbial N requirements, accurate estimates of urea recycling can improve the understanding of efficiency of N utilization and N losses to the environment. The objective of this study was to evaluate urea kinetics and microbial usage of recycled urea N in ruminants using a meta-analytical approach. Treatment mean values were compiled from 25 studies with ruminants (beef cattle, dairy cows and sheep) which were published from 2001 to 2016, totalling 107 treatment means. The data set was analyzed according to meta-analysis techniques using linear or non-linear mixed models, taking into account the random variations among experiments. Urea N synthesized in the liver (UER) and urea N recycled to the gut (GER) linearly increased (P<0.001) as N intake (g/BW^0.75) increased, with increases corresponding to 71.5% and 35.2% of N intake, respectively. The UER was positively associated (P<0.05) with dietary CP concentration and the ratio of CP to digestible OM (CP:DOM). Maximum curvature analyses identified 17% dietary CP as the point where there was a prominent increase in hepatic synthesis of urea N, likely due to an excess of dietary N leading to greater ammonia absorption. The GER:UER decreased with increasing dietary CP concentration (P<0.05). At dietary CP⩾19%, GER:UER reached near minimal values. The fraction of UER eliminated as urinary urea N and the contribution of urea N to total urinary N were positively associated with dietary CP (P<0.05), both reaching values near the plateau when dietary CP was 17%. The fractions of GER excreted in the feces and utilized for anabolism decreased, whereas the fraction of GER returned to the ornithine cycle increased with dietary CP concentration (P<0.05). Recycled urea N assimilated by ruminal microbes (as a fraction of GER) decreased as dietary CP and CP:DOM increased (P<0.05). The efficiency of microbial assimilation of recycled urea N was near plateau values at 194 g CP/kg DOM. The models obtained in this study contribute to the knowledge on N utilization, and they could be used in feeding models to predict urea recycling and thus to improve formulation of diets to reduce N losses that contribute to air and water pollution.     

An optimal dietary non-phytate phosphorus level of broilers fed a conventional corn–soybean meal diet from 4 to 6 weeks of age

It is imperative to evaluate precise nutrient requirements of animals in order to optimize productivity and minimize feed cost and nutrient excretions. The current non-phytate phosphorus (NPP) recommendation for broilers is based on the papers published 30 years ago. However, today’s commercial birds are quite different from those before 30 years. Therefore, the present experiment was conducted with growing male broiler chickens to evaluate an optimal dietary NPP level of broiler chickens fed a conventional corn–soybean meal diet from 4 to 6 weeks of age. The 1-day-old chicks were fed corn–soybean meal diet containing 0.39% NPP from 1 to 3 weeks of age. At 22 days of age, 360 birds were selected and randomly allotted by BW to one of 10 dietary treatments with six replicate cages of six birds per cage for each treatment. Birds were fed the P-unsupplemented corn–soybean meal basal diet and the basal diet supplemented with inorganic P as CaHPO₄·H₂O ranging from 0.00% to 0.45% with 0.05% increment from 4 to 6 weeks of age. The dietary NPP levels were 0.09%, 0.14%, 0.20%, 0.24%, 0.30%, 0.34%, 0.38%, 0.45%, 0.49% and 0.54%, respectively, and the dietary Ca level was fixed at 0.90% for all treatments. The results showed that average daily gain, serum inorganic P concentration, tibia bone strength, tibia ash percentage and P percentage, tibia bone mineral content (BMC) and density (BMD), middle toe ash percentage and P percentage, middle toe BMC, total body BMC and BMD were affected (P<0.0001) by dietary NPP level, and increased linearly (P<0.0001) and quadratically (P<0.003) as dietary NPP levels increased. Optimal dietary NPP levels estimated based on fitted broken-line models (P<0.0001) of the above indices are 0.21%, 0.29%, 0.29%, 0.29%, 0.29%, 0.31%, 0.29%, 0.30%, 0.27%, 0.29% and 0.28%, respectively. It is suggested that the total body BMC and BMD, and middle toe ash P and BMC might be new, sensitive and non-invasive criteria to evaluate the dietary NPP requirements of broilers. The optimal dietary NPP level would be 0.31% for broiler chickens fed a conventional corn–soybean meal diet from 4 to 6 weeks of age.     

Dietary P regulates phosphate transporter expression,phosphatase activity,and effluent P partitioning in trout culture

Phosphate utilization by fish is an important issue because of its critical roles in fish growth and aquatic environmental pollution. High dietary phosphorus (P) levels typically decrease the efficiency of P utilization, thereby increasing the amount of P excreted as metabolic waste in effluents emanating from rainbow trout aquaculture. In mammals, vitamin D₃ is a known regulator of P utilization but in fish, its regulatory role is unclear. Moreover, the effects of dietary P and vitamin D₃ on expression of enzymatic and transport systems potentially involved in phosphate utilization are little known. We therefore monitored production of effluent P, levels of plasma vitamin D₃ metabolites, as well as expression of phosphatases and the sodium phosphate cotransporter (NaPi2) in trout fed semipu diets that varied in dietary P and vitamin D₃ levels. Mean soluble P concentrations varied markedly with dietary P but not with vitamin D₃, and constituted 40–70% of total effluent P production by trout. Particulate P concentrations accounted for 25–50% of effluent P production, but did not vary with dietary P or vitamin D₃. P in settleable wastes accounted for <10% of effluent P. The stronger effect of dietary P on effluent P levels is paralleled by its striking effects on phosphatases and NaPi2. The mRNA abundance of the intestinal and renal sodium phosphate transporters increased in fish fed low dietary P; vitamin D₃ had no effect. Low-P diets reduced plasma phosphate concentrations. Intracellular phytase activity increased but brushborder alkaline phosphatase activity decreased in the intestine, pyloric caeca, and gills of trout fed diets containing low dietary P. Vitamin D₃ had no effect on enzyme activities. Moreover, plasma concentrations of 25-hydroxyvitamin D₃ and of 1,25-dihydroxyvitamin D₃ were unaffected by dietary P and vitamin D₃ levels. The major regulator of P metabolism, and ultimately of levels of P in the effluent from trout culture, is dietary P.Communicated by: C.-H. Wang     

Bacterial protein meal in diets for pigs and minks: comparative studies on protein turnover rate and urinary excretion of purine base derivatives

The effect of increasing the dietary content of bacterial protein meal (BPM) on protein turnover rate, and on nucleic acid and creatinine metabolism in growing minks and pigs was investigated in two experiments. In each experiment, 16 animals were allocated to four experimental diets. The diets containing no BPM served as controls, i.e. for minks diet M1, for pigs P1; the experimental diets contained increasing levels of BPM to replace fish meal (minks) or soybean meal (pigs), so that up to 17% (P2), 20% (M2), 35% (P3), 40% (M3), 52% (P4), and 60% (M4) of digestible N was BPM derived. Protein turnover rate was measured by means of the end-product method using [15N]glycine as tracer and urinary nitrogen as end-product. In minks, protein flux, synthesis, and breakdown increased significantly with increasing dietary BPM. In pigs, diet had no observed effect on protein turnover rate. The intake of nucleic acid nitrogen (NAN) increased from 0.15 g/kg W0.75 on M1 to 0.26 g/kg W0.75 on M3 and M4 in the mink experiment, and from 0.08 g/kg W0.75 on P1 to 0.33 g/kg W0.75 on P4 in the pig experiment. Increased NAN intake led, in both experiments, to increased allantoin excretion. Analysis of species effects showed that minks excreted 1.72 mmol/ kg W0.75 of allantoin, significantly more than the 0.95 mmol/kg W0.75 excreted by pigs. In minks, approximately 96% of the excreted purine base derivatives consisted of allantoin, whereas in pigs approximately 93% did. Thus, increasing the dietary content of BPM increased protein turnover rate in minks but not in pigs, and allantoin excretion increased with increasing dietary BPM although it seemed that mink decomposed purine bases to their end-product more completely than pigs did. Collectively these data show that BPM is a suitable protein source for pigs and mink, and recorded differences between species were to a large extent due to differences in protein retention capacity and muscle mass.     

Low degradable protein supply to increase nitrogen efficiency in lactating dairy cows and reduce environmental impacts at barn level

Generally, <30% of dairy cattle’s nitrogen intake is retained in milk. Large amounts of nitrogen are excreted in manure, especially in urine, with damaging impacts on the environment. This study explores the effect of lowering dietary degradable nitrogen supplies – while maintaining metabolisable protein – on dairy cows’ performance, nitrogen use efficiency and gas emissions (NH₃, N₂O, CH₄) at barn level with tied animals. Two dietary N concentrations (CP: 12% DM for LowN; 18% DM for HighN) were offered to two groups of three lactating dairy cows in a split-plot design over four periods of 2 weeks. Diets were formulated to provide similar metabolisable protein supply, with degradable N either in deficit or in excess (PDIN of 84 and 114 g/kg DM for LowN and HighN, respectively). Cows ingested 0.8 kg DM/day less on the LowN diet, which was also 2.5% less digestible. Milk yield and composition were not significantly affected. N exported in milk was 5% lower (LowN: 129 g N/day; HighN: 136 g N/day; P<0.001) but milk protein yield was not significantly affected (LowN: 801 g/day; HighN: 823 g/day; P=0.10). Cows logically ingested less nitrogen on the LowN diet (LowN: 415 g N/day; HighN: 626 g N/day; P<0.001) resulting in a higher N use efficiency (N milk/N intake; LowN: 0.31; HighN: 0.22; P<0.001). N excreted in urine was almost four times lower on the LowN diet (LowN: 65 g N/day; HighN: 243 g N/day; P<0.001) while urinary urea N concentration was eightfold lower (LowN: 4.6 g/l; HighN: 22.9 g/l; P<0.001). Ammonia emission (expressed in g/h in order to remove periods of the day with potential interferences with volatile molecules from feed) was also lower on the LowN diet (LowN: 1.03 g/h per cow; HighN: 1.25 g/h per cow; P<0.05). Greenhouse gas emissions (N₂O and CH₄) at barn level were not significantly affected by the amount of dietary N. Offering low amounts of degradable protein with suitable metabolisable protein amounts to cattle improved nitrogen use efficiency and lowered ammonia emissions at barn level. This strategy would, however, need to be validated for longer periods, other housing systems (free stall barns) and at farm level including all stages of manure management.     

Gender-specific prandial response to dietary restriction and oxidative stress in Drosophila melanogaster

Drosophila melanogaster is ideal for studying lifespan modulated by dietary restriction (DR) and oxidative stress, and also for screening prolongevity compounds. It is critical to measure food intake in the aforementioned studies. Current methods, however, overlook the amount of the food excreted out of the flies as feces or deposited in eggs. Here we describe a feeding method using a radioactive tracer to measure gender-specific food intake, retention and excretion in response to DR and oxidative stress to account for all the ingested food. Flies were fed a full, restricted or paraquat-containing diet. The radioactivity values of the food in fly bodies, feces and eggs were measured separately after a 24-hr feeding. Food intake was calculated as the sum of these measurements. We found that most of the tracer in the ingested food was retained in the fly bodies and &lt; 8% of the tracer was excreted out of the flies as feces and eggs in the case of females during a 24-hr feeding. Under a DR condition, flies increased food intake in volume to compensate for the reduction of calorie content in the diet and also slightly increased excretion. Under an oxidative stress condition, flies reduced both food intake and excretion. Under all the tested dietary conditions, males ingested and excreted 3-5 fold less food than females. This study describes an accurate method to measure food intake and provides a basis to further investigate prandial response to DR and prolongevity interventions in invertebrates.     

Speciation and dietary specialization in Drupa,a genus of predatory marine snails (Gastropoda: Muricidae)

Claremont, M., Reid, D.G. & Williams, S.T. (2012) Speciation and dietary specialization in Drupa, a genus of predatory marine snails (Gastropoda: Muricidae). —Zoologica Scripta, 41, 137–149. We test the competing predictions of allopatric speciation and of ecological speciation by dietary specialization in Drupa, an Indo‐Pacific genus of carnivorous marine gastropods in the family Muricidae. We use a well‐resolved molecular phylogeny (reconstructed from one nuclear and two mitochondrial genes) to show the validity of the traditional species D. elegans, D. rubusidaeus, D. clathrata, D. morum and D. speciosa.‘Drupa ricinus’ is shown to consist of three species: D. ricinus s. s., D. albolabris and a new species, possibly endemic to Japan. ‘Purpura’aperta is transferred to Drupa. Despite potential widespread dispersal and a high degree of range overlap among sister species, range sizes between sister species are highly asymmetric, suggesting that speciation has been predominately peripatric. The exception is the sister pair D. ricinus s. s. and D. albolabris, which have symmetric range sizes and are sympatric over broad Indo‐Pacific ranges. Such symmetry and extensive sympatry are contrary to the predictions of the (peripatric) allopatric model of speciation. Nevertheless, contrary to the predictions of an ecological speciation model based upon dietary specialization, broad dietary range appears to be identical between the species. Small differences in microhabitat preferences (or hypothetical dietary specialization at a fine taxonomic scale) may have been significant in the speciation process or, if initial divergence was allopatric, in permitting subsequent sympatry. Broad dietary shifts appear to have accompanied more ancient divergences within the genus Drupa.     

Bacterial protein meal in diets for pigs and minks: Comparative studies on protein turnover rate and urinary excretion of purine base derivatives

Abstract

The effect of increasing the dietary content of bacterial protein meal (BPM) on protein turnover rate, and on nucleic acid and creatinine metabolism in growing minks and pigs was investigated in two experiments. In each experiment, 16 animals were allocated to four experimental diets. The diets containing no BPM served as controls, i.e. for minks diet M1, for pigs P1; the experimental diets contained increasing levels of BPM to replace fish meal (minks) or soybean meal (pigs), so that up to 17% (P2), 20% (M2), 35% (P3), 40% (M3), 52% (P4), and 60% (M4) of digestible N was BPM derived. Protein turnover rate was measured by means of the end-product method using [¹⁵N]glycine as tracer and urinary nitrogen as end-product. In minks, protein flux, synthesis, and breakdown increased significantly with increasing dietary BPM. In pigs, diet had no observed effect on protein turnover rate. The intake of nucleic acid nitrogen (NAN) increased from 0.15 g/kg W^0.75 on M1 to 0.26 g/kg W^0.75 on M3 and M4 in the mink experiment, and from 0.08 g/kg W^0.75 on P1 to 0.33 g/kg W^0.75 on P4 in the pig experiment. Increased NAN intake led, in both experiments, to increased allantoin excretion. Analysis of species effects showed that minks excreted 1.72 mmol/kg W^0.75 of allantoin, significantly more than the 0.95 mmol/kg W^0.75 excreted by pigs. In minks, approximately 96% of the excreted purine base derivatives consisted of allantoin, whereas in pigs approximately 93% did. Thus, increasing the dietary content of BPM increased protein turnover rate in minks but not in pigs, and allantoin excretion increased with increasing dietary BPM although it seemed that mink decomposed purine bases to their end-product more completely than pigs did. Collectively these data show that BPM is a suitable protein source for pigs and mink, and recorded differences between species were to a large extent due to differences in protein retention capacity and muscle mass.     

Energy metabolism and protein balance in growing rats fed different levels of dietary fibre and protein

A study was performed to investigate the effect of different levels of dietary fibre (DF) and dietary protein on visceral organ size, digestibility, nitrogen balance and energy metabolism in rats. Thirty-six male Wistar rats, initial body weight about 76 g, were used in a factorial design consisting of three levels of DF (low, 100 g/kg DM; medium, 250 g/kg DM and high, 290 g/kg DM) and two levels of dietary protein (low, 120 g/kg DM and high, 223 g/kg DM). The added fibre source was soybean hulls and Danish fish meal was used as sole source of dietary protein. Measurements of gas-exchange were done on six rats (one group) while urine and faeces were collected individually. The ratio of food/empty body gain increased (P < 0.05) with increasing DF and decreasing levels of dietary protein. The weight of the digestive tract was larger (P < 0.05) in rats fed the high fibre diet than in those fed the low fibre diet. The digestibility of nutrients and energy decreased linearly with increasing level of soybean fibre (P < 0.05). An increased intake of DF was associated with a concomitant loss of protein and energy to faeces. The microbial degradation of NSP and other unabsorbed carbohydrates caused considerably changes in N metabolism of the colon. In rats fed the low protein diets increased levels of DF decreased N excretion in urine and increased N excretion in faeces, while the ratio of retained/digested protein remained constant. When rats were fed the high protein diet protein retention dropped in response to DF both absolute and relative to digested amount, indicating that energy intake could be a limiting factor. Heat production as a percentage of metabolizable energy (HP/ME) was higher (P < 0.05) in rats fed the low protein diet than in rats fed the high protein diet, but no significant difference was found among DF levels.     

Escherichia coli produces a cytoplasmic alpha-amylase, AmyA.

In the gap between two closely linked flagellar gene clusters on the Escherichia coli and Salmonella typhimurium chromosomes (at about 42 to 43 min on the E. coli map), we found an open reading frame whose sequence suggested that it encoded an alpha-amylase; the deduced amino acid sequences in the two species were 87% identical. The strongest similarities to other alpha-amylases were to the excreted liquefying alpha-amylases of bacilli, with > 40% amino acid identity; the N-terminal sequence of the mature bacillar protein (after signal peptide cleavage) aligned with the N-terminal sequence of the E. coli or S. typhimurium protein (without assuming signal peptide cleavage). Minicell experiments identified the product of the E. coli gene as a 56-kDa protein, in agreement with the size predicted from the sequence. The protein was retained by spheroplasts rather than being released with the periplasmic fraction; cells transformed with plasmids containing the gene did not digest extracellular starch unless they were lysed; and the protein, when overproduced, was found in the soluble fraction. We conclude that the protein is cytoplasmic, as predicted by its sequence. The purified protein rapidly digested amylose, starch, amylopectin, and maltodextrins of size G6 or larger; it also digested glycogen, but much more slowly. It was specific for the alpha-anomeric linkage, being unable to digest cellulose. The principal products of starch digestion included maltotriose and maltotetraose as well as maltose, verifying that the protein was an alpha-amylase rather than a beta-amylase. The newly discovered gene has been named amyA. The natural physiological role of the AmyA protein is not yet evident.