Digestion dynamics in broilers fed rapeseed meal.

Rapeseed proteins are described to be poorly digestible in chickens. To further identify some molecular locks that may limit their use in poultry nutrition, we conducted a proteomic study on the various chicken digestive contents and proposed an integrative view of the proteins recruited in the crop, proventriculus/gizzard, duodenum, jejunum, and ileum for digestion of rapeseed by-products. Twenty-seven distinct rapeseed proteins were identified in the hydrosoluble fraction of the feed prior ingestion. The number of rapeseed proteins identified in digestive contents decreases throughout the digestion process while some are progressively solubilized in the most distal digestive segment, likely due to a combined effect of pH and activity of specific hydrolytic enzymes. Fifteen chicken proteins were identified in the hydrosoluble proventriculus/gizzard content, including chymotrypsin-like elastase and pepsin. Interestingly, on the 69 distinct proteins identified in duodenum, only 9 were proteolytic enzymes, whereas the others were associated with homeostasis, and carbohydrate, lipid, vitamin and hormone metabolisms. In contrast, chicken proteins identified in jejunal and ileal contents were mostly proteases and peptidases. The present work highlights the relevance of using integrative proteomics applied to the entire digestive tract to better appreciate the protein profile and functions of each digestive segment.

Effects of rapeseed meal fiber content on phosphorus and calcium digestibility in growing pigs fed diets without or with microbial phytase.

The optimization of dietary phosphorus (P) and calcium (Ca) supply requires a better understanding of the effect of dietary fiber content of co-products on the digestive utilization of minerals. This study was designed to evaluate the effects of dietary fiber content from 00-rapeseed meal (RSM) on P and Ca digestibility throughout the gastrointestinal tract in growing pigs fed diets without or with microbial phytase. In total, 48 castrated male pigs (initial BW=36.1±0.4 kg) were housed in metabolic crates for 29 days. After an 8-day adaptation period, pigs were allocated to one of the eight treatments. The impact of dietary fiber was modulated by adding whole RSM (wRSM), dehulled RSM (dRSM) or dRSM supplemented with 4.5% or 9.0% rapeseed hulls (dRSMh1 and dRSMh2). Diets contained 0 or 500 phytase unit of microbial phytase per kg. From day 14 to day 23, feces and urine were collected separately to determine apparent total tract digestibility (ATTD) and apparent retention (AR) of P and Ca. At the end of the experiment, femurs and digestive contents were sampled. No effect of variables of interest was observed on growth performance. Microbial phytase increased ATTD and AR of P (P<0.001) but the P equivalency with the wRSM diet was lower than expected. Moreover, stomach inorganic P (iP) solubility was improved by microbial phytase (P<0.001). The ATTD of Ca was not affected by microbial phytase which increased AR of Ca and femur characteristics (P<0.05). Ileal recovery of P was not affected by microbial phytase but cecal recovery was considerably reduced by microbial phytase (P<0.001). The decrease in digesta pH between the distal ileum and cecum (7.6 v. 5.9) enhanced the solubility of iP and may have improved its absorption, as supported by the negative relationship between soluble iP and pH (R 2=0.40, P<0.001 without microbial phytase and R 2=0.24, P=0.026 with microbial phytase). The inclusion of hulls improved the solubility of iP (P<0.05). In conclusion, dehulling does not largely increase nutrient digestibility although dRSM seems to improve the efficacy of microbial phytase in releasing phosphate in the stomach. Moreover, dietary fiber may affect solubilization process in the cecum which potentiates the effect of microbial phytase on P digestibility.

Exploring the in vivo digestion of plant proteins in broiler chickens.

The use of various protein sources (industry by-products, proteaginous) in poultry diets requires a greater understanding of protein digestion mechanisms. The aim of this study was to characterize the molecular actors required for protein digestion in broilers fed 4 different diets containing soybean meal, rapeseed meal, pea, or corn distiller's dried grain with solubles as the only protein source. The digesta of the digestive tract segments were collected and soluble proteins were analyzed by SDS-PAGE. SDS-PAGE analyses revealed 5 ubiquitous bands in digesta of all digestive tract segments regardless of the diet, whereas 3 bands were diet-specific. The digesta of the jejunum were further submitted to proteomic analysis. Forty-two proteins of chicken origin and 17 plant proteins were identified in digesta samples by mass spectrometry. Fifteen proteins of chicken origin were specific to one diet and 18 were common to all diets. By homology with mammals, these proteins are thought to be involved in protein, lipid, carbohydrate, and nucleic acid metabolism and also in intestinal homeostasis. Some of the 17 plant proteins were found to be not fully digested (soybean meal, rapeseed meal, and pea diets) and others were identified as protease inhibitors (soybean meal and pea diets). This study provides a comprehensive analysis of the physiological proteins involved in the digestion of 4 protein sources used in broiler diets. Such an approach, combined with the analysis of insoluble components of these different protein sources, would contribute to define whether these protein sources could be more largely used in poultry nutrition. It also would allow identifying ways to improve their digestibility in broiler chickens (feed additives such as exogenous proteases or processing to inactivate anti-nutritional factors, for instance).

Subcutaneous body lipids affect cyclicity and estrus behavior in primiparous Charolais cows.

Conception rate and the calving interval of beef cows are known to be influenced by body reserves at calving and subsequent postpartum changes. However, few studies have focused on the effect of body reserve dynamics on both postpartum cyclicity and estrus expression. Two successive similar experiments (Year 1: n=14; Year 2: n=16) were carried out on primiparous Charolais cows reared indoors during winter to quantify the effects of adipose cell diameter at calving (ACDca) and their postpartum changes (ACDch) on cyclicity and estrus behavior. Cows were managed to calve with a body condition score (BCS, scale 0-5) of 2.5 (Year 1) and 1.5 (Year 2). After calving cows were assigned to a Low vs. a High energy level diet until turn out to pasture in May. Within years ACDca was similar between Low and High groups whereas calving to turnout changes of body weight (BW), BCS and adipose cell diameter differed (P<0.0001). The interval between calving and resumption of luteal activity was negatively correlated with ACDca (P=0.001). Estrus duration (interval between first and last standing to be mounted (STBM)) was longer in Low than in High groups (P=0.02). Number of STMB was higher in Low than in High cows. Adipose cell diameter at calving and postpartum changes had distinct effects on the components of reproductive performance; emphasizing the need to consider both amounts and changes of body lipids to predict relationships between nutrition and reproduction in cows.