Evaluation of analytical and statistical approaches for predicting in vitro nitrogen solubility and in vivo pre-caecal crude protein digestibility of cereal grains in growing pigs.

Different analytical (enzyme system and near-infrared spectroscopy (NIRS)) and statistical (single and multiple regressions) approaches were used to predict in vivo standardized pre-caecal digestibility (PCD) of crude protein (CP) and amino acids (AA) in cereal grains for growing pigs as well as in vitro nitrogen (N) solubility. Furthermore, different chemical and physical characteristics were categorized (e.g. crude nutrients, AA, minerals, fibre components or combinations of these) and used for generating prediction equations. There were strong linear relationships (p < .05) between in vivo PCD of CP and essential AA and in vitro N solubility when grain species was considered as covariate in the model. Predicting in vivo PCD values using various chemical and physical characteristics produced inconsistent results among different grain species and AA and could therefore not be used for predicting PCD. It is possible to predict in vitro N solubility from chemical and physical characteristics for some grain species. However, the relationships between some of these categories and the in vitro N solubility were not consistent and not always causative or physiologically explainable. The R2 of NIRS for predicting in vitro N solubility was at a relatively high level (up to R2  = 0.80). This level of R2 indicates that a classification of the grain samples in, for example, high, medium and low in vitro N solubility levels is possible, but it does not allow for a quantitative prediction of the in vitro N solubility. In conclusion, the present database can be used for establishing a ranking of different cereal grain species for PCD of CP and essential AA values. However, it was not possible to create clear prediction equations for in vivo or in vitro digestibility values. Therefore, greater variation within grain species, for example due to different growing and harvesting conditions, is warranted for predicting PCD values of individual grain samples.

Methodological impact of starch determination on starch content and ileal digestibility of starch in grain legumes for growing pigs.

BACKGROUND: Grain legumes represent a valuable energy source in pig diets due to their high starch content. The present study was conducted to determine the content and apparent ileal digestibility (AID) of starch in different grain legume cultivars for pigs by means of both a polarimetric and enzymatic method for starch determination. METHODS: Three experiments were conducted with six barrows each which were fitted with ileal T-cannulas. In total, 18 diets including six different cultivars of faba beans (Vicia faba L.) and peas (Pisum sativum L.), five different cultivars of lupins (Lupinus luteus L., Lupinus angustifolius L.), and one diet with a soybean meal (SBM) were fed. RESULTS: The starch content of faba beans and peas was greater (P < 0.05) when determined polarimetrically than enzymatically (438 vs. 345 g/kg dry matter (DM) in faba beans and 509 vs. 390 g/kg DM in peas, respectively). Considerable lower starch contents were obtained in lupins and SBM, with 82 and 48 g/kg DM (analyzed polarimetrically) and <1.1 and 3 g/kg DM (analyzed enzymatically), respectively. Mean values for contents of neutral detergent fiber (NDF) and acid detergent fiber (ADF) in grain legumes ranged from 111 and 79 g/kg DM in peas to 248 and 207 g/kg DM in lupins, respectively. Contents of condensed tannins in the colored flowered faba bean cultivars ranged from 2.1 to 7.4 g/kg DM. The AID of starch was greater (P < 0.05) in pea than in faba bean cultivars, and using the polarimetric starch determination method resulted in greater (P < 0.05) digestibility values than using enzymatic starch analysis (84 vs. 80% in faba beans and 86 vs. 83% in peas). Moreover, AID of starch differed (P < 0.05) within pea cultivars and starch digestibility in faba beans decreased linearly (P < 0.05) as the content of condensed tannins increased. However, there was no relationship between contents of NDF and ADF and AID of starch in pea and faba bean cultivars. CONCLUSION: Both contents and AID of starch in grain legumes can vary as influenced by the analytical method used for starch determination. Generally, starch digestibility is greater when measured by polarimetric rather than enzymatic methods.

Effect of the desolventizing/toasting process on chemical composition and protein quality of rapeseed meal.

BACKGROUND: During processing in a desolventizer/toaster (DT), rapeseed meal (RSM) is heated to evaporate the hexane and to reduce the level of heat-labile anti-nutritional factors such as glucosinolates (GSL). However, excessive heat treatment may reduce amino acid (AA) content in addition to lower AA digestibility and availability in RSM. The objective of the present study was to produce from one batch of a 00-rapeseed variety (17 µmol GSL/g dry matter (DM), seed grade quality) five differently processed RSM under standardized and defined conditions in a pilot plant, and to determine the impact of these different treatments on protein solubility and chemical composition, in particular with regard to contents of AA including reactive Lys (rLys) and levels of total and individual GSL. METHODS: Four RSM were exposed to wet toasting conditions (WetTC) with increasing residence time in the DT of 48, 64, 76, and 93 min. A blend of these four RSM was further processed, starting with saturated steam processing (< 100 °C) and followed by exposure to dry toasting conditions (DryTC) to further reduce the GSL content in this RSM. RESULTS: The contents of neutral detergent fiber and neutral detergent fiber bound crude protein (CP) increased linearly (P < 0.05), as residence time of RSM in the DT increased from 48 to 93 min, whereas contents of total and most individual GSL and those of Lys, rLys, Cys, and the calculated ratio of Lys:CP and rLys:CP decreased linearly (P ≤ 0.05). The combination of wet heating and DryTC resulted in the lowest GSL content compared to RSM produced under WetTC, but was associated with lowest protein solubility. CONCLUSIONS: It can be concluded that by increasing residence time in the DT or using alternative processing conditions such as wet heating combined with DryTC, contents of total and individual GSL in RSM can be substantially reduced. Further in vivo studies are warranted to elucidate if and to which extent the observed differences in protein quality and GSL content between RSM may affect digestibility and bioavailability of AA in monogastric animals.

Novel insights into RNP granules by employing the trypanosome's microtubule skeleton as a molecular sieve.

RNP granules are ribonucleoprotein assemblies that regulate the post-transcriptional fate of mRNAs in all eukaryotes. Their exact function remains poorly understood, one reason for this is that RNP granule purification has not yet been achieved. We have exploited a unique feature of trypanosomes to prepare a cellular fraction highly enriched in starvation stress granules. First, granules remain trapped within the cage-like, subpellicular microtubule array of the trypanosome cytoskeleton while soluble proteins are washed away. Second, the microtubules are depolymerized and the granules are released. RNA sequencing combined with single molecule mRNA FISH identified the short and highly abundant mRNAs encoding ribosomal mRNAs as being excluded from granules. By mass spectrometry we have identified 463 stress granule candidate proteins. For 17/49 proteins tested by eYFP tagging we have confirmed the localization to granules, including one phosphatase, one methyltransferase and two proteins with a function in trypanosome life-cycle regulation. The novel method presented here enables the unbiased identification of novel RNP granule components, paving the way towards an understanding of RNP granule function.

Effect of dietary protein supply originating from soybean meal or casein on the intestinal microbiota of piglets.

Dietary composition is a major factor influencing the intestinal microbial ecosystem of pigs. To alleviate weaning-associated disorders, variations in dietary protein supply may beneficially affect microbial composition in the gastrointestinal tract of piglets. A total of 48 piglets, fitted with simple ileal T-cannulas, was used to examine the effect of protein supply of either highly digestible casein or less digestible, fiber-rich soybean meal (SBM) on the composition of the intestinal microbiota. Gene copies of 7 bacteria groups were determined by real-time PCR in ileal digesta and feces. Ileal counts of total eubacteria, the Bacteroides-Prevotella-Porphyromonas group, Enterobacteriaceae and Clostridium Cluster XIVa were higher (P < 0.001) in the casein-based diets. Fecal counts of all analyzed bacterial groups were higher for the SBM-based diets (P < 0.001), apart from Enterobacteriaceae (P < 0.05) which were higher in the casein-based diets. Ileal counts of lactobacilli linearly increased as the crude protein level was increased up to 335 g/kg (P < 0.01). The Bacteroides-Prevotella-Porphyromonas group linearly decreased in ileal samples (P < 0.01) and increased in fecal samples (P < 0.05) as the crude protein level in the SBM-based diet was increased. Both, protein level and protein source may affect intestinal microbial balance. Higher dietary protein levels in combination with diets low in fiber contents might stimulate proliferation of protein fermenting bacteria in piglet's large intestine. Further studies are warranted to clarify, whether this would be associated with intestinal disturbances.

Effect of feed intake level on ileal digestibilities of crude protein and amino acids in diets for piglets.

BACKGROUND: The study was conducted to determine the effect of graded levels of feed intake on apparent (AID) and standardized (SID) ileal digestibilities of crude protein (CP) and amino acids (AA) in diets for piglets. The piglets were surgically fitted with simple T-cannulas at the distal ileum. The cornstarch-casein-soybean meal-based diets were fed at three graded levels of feed intake corresponding to 30, 45 and 60 g kg(-1) body weight (BW) per day. RESULTS: The AID and SID of most AA were quadratically affected by the feed intake level (P≤0.05). Initially, both AID and SID of most AA increased up to 1.9 percentage units as the feed intake level was increased from 30 to 45 g kg(-1) BW. Thereafter, these AID and SID values decreased by 2.6 and 2.7 percentage units, respectively, as the feed intake level was further increased from 45 to 60 g kg(-1) BW. CONCLUSION: Because the voluntary feed intake is highly variable in piglets after weaning, comparison of ileal AA digestibilities between and within studies may be confounded by variations in feed intake level. Thus, when designing digestibility studies with piglets, a standardization of feed intake should be taken into consideration.

The role of dietary nucleotides in single-stomached animals.

The transition from liquid to solid feed during weaning results in morphological, histological and microbial changes in the young animal's intestinal tract and often is associated with diarrhoea. The ban of in-feed antibiotics in pig production in the European Union has led to increasing interest in alternatives to overcome weaning-associated problems. Among others, nucleotides may have the potential to alleviate health impairments due to weaning. Nucleotides are natural components of the non-protein fraction of milk and have important effects on the maintenance of health in young animals. Nucleotides and their related metabolic products play key roles in many biological processes and become essential dietary components when endogenous supply is insufficient for normal function. The present review summarises nucleotide composition of milk from different species, the biology of nucleotides and possible effects of dietary nucleotides on intestinal morphology and function, intestinal microbiota, immune function, nutrient metabolism, hepatic morphology and function as well as growth performance. Special attention is given to data available for pigs, and suggestions are made for inclusion of nucleotides in the diet to benefit piglets' health and reduce the consequences accompanying early weaning.

Standardised ileal crude protein and amino acid digestibilities in protein supplements for piglets.

Standardised ileal digestibilities (SID) of crude protein and amino acids (AA) originating from 24 different feed ingredients, including 11 feed ingredients produced from soybeans, seven by-products of starch processing, four whey products and two fish meals, were determined in piglets by means of the difference method. For the indispensable AA, the highest SID values were obtained in three out of four whey proteins (SID ≥90% for most indispensable AA), one out of two fish meals (SID ≥86%), soy protein concentrate, hydrolysed soy protein isolate (SID ≥86% for most indispensable AA), and by-products of starch processing (SID ≥84% for most indispensable AA). The lowest SID values were obtained in extruded soybeans and microbially fermented soy protein (SID ≤78% for most indispensable AA), whereas the SID values for high-protein soybean meal were intermediate (SID 80-89% for indispensable AA except for Thr). The SID values in the three enzymatically fermented soy proteins (SID 80-94% for most indispensable AA) were similar to those in high-protein soybean meal and soy protein concentrate. The results of the present study indicate that SID values of AA in feed ingredients for piglets differ considerably from those reported for grower-finisher pigs, thus there may be a need for separate feed tables for piglets.

Effects of betaine, organic acids and inulin as single feed additives or in combination on bacterial populations in the gastrointestinal tract of weaned pigs.

A study was carried out to investigate whether blends of betaine, organic acids and inulin may improve their efficacy to modulate intestinal bacterial populations in weaned pigs compared with the single application of these additives. Moreover, potential postprandial diurnal variations in ileal bacterial numbers were determined in piglets fed the control diet. Twenty-four piglets in two consecutive experiments received a wheat-barley-soybean meal control diet (Con) or the Con diet supplemented with betaine (BET; 0.2%), an organic acid blend (AC; 0.4%) or inulin (IN; 0.2%) as single additives or in combination. Ileal bacterial numbers of total bacteria, lactobacilli, bifidobacteria (p < 0.05) and enterobacteria (p < 0.10) showed a postprandial diurnal variation, thus spot sampling of ileal digesta for the determination of bacterial numbers may not be representative. There were only small effects of BET, AC and IN on ileal and faecal bacterial populations. BET + AC increased total ileal bacterial numbers compared to the Con and AC treatments. BET reduced lactobacilli numbers in faeces, whereas BET + IN increased ileal numbers of bifidobacteria compared to AC and IN. There is evidence that BET, AC, IN and their combinations may affect proliferation of beneficial bacterial populations, although this has to be confirmed in further studies.