A model of phosphorus digestion and metabolism in the lactating dairy cow

A dynamic, mechanistic, compartmental model of phosphorus (P) digestion and metabolism was constructed in the Advanced Continuous Simulation Language using conservation of mass principles and mass action kinetics. Phosphorus was assumed to exist in 3 forms: inorganic (Pi), phytic acid (Pp), and organic (excluding phytic acid; Po). All 3 forms were assumed to be present in the digestive tract with absorption of Pi into blood. Inputs to the model were total P intake; Pp, Po, and Pi as proportions of total P; milk yield; rate of salivation (fixed at 239 L/d); and rate of liquid passage from the rumen (fixed at 198 L/d). The model was fitted to 2 experiments from the literature. Derived parameters were well defined by the data. With a mean observed P intake of 75 g/d, total tract P digestibility was 38%. Phytic acid P digestibility in the rumen was 74%, with no additional Pp digestion in the lower tract. Inorganic P and Po digestibility in the lower tract were 48 and 89%, respectively. Flows of Po and Pi from the rumen were 2.4 and 3.0 times greater than intake, respectively. The increase in Po was apparently due to microbial growth. The increase in Pi arose primarily from secretion of Pi into the rumen via salivation where 65% of absorbed P was recycled to the rumen. Milk synthesis used 30% of absorbed Pi, and 1% was excreted in urine. This research suggested that the primary regulation points for maintaining blood P were bone deposition and resorption and absorption from the intestine. However, because bone P balance was related to both dietary P intake and ruminal phytase activity, it is critical to achieve a better understanding of phytate digestibility across several feeds if dietary P is to be reduced below current requirements.     

抗性淀粉对糖、脂以及肠道代谢影响的研究进展

综述了近年来国内外对抗性淀粉及其生理功能的研究动态;介绍了抗性淀粉的定义、分类及其生理功能;阐明了抗性淀粉对血糖、血脂及肠道代谢的影响和作用机理。抗性淀粉是一种新型的膳食纤维,在小肠中不被消化吸收, 但在大肠中能被肠道菌群发酵分解。它作为一种低热量、高纤维含量的功能性食品成分,越来越被人们所认识和重视。     

波谱特性与淀粉消化行为的关系

通过不同的加热方式,以普通玉米淀粉和高直链玉米淀粉为原料制备结构不同的系列淀粉样品,然后采用傅里叶变换衰减全反射红外光谱法(ATR-FTIR)分析技术,测定了不同淀粉样品的波谱图特征吸收峰,结果表明高直链玉米淀粉在热处理过程中其特征吸收峰只发生细微变化,而普通玉米淀粉的波谱图变化显著,其在最高吸收峰处由左低右高形态转变为左高右低形态.综合各特征吸收峰在淀粉结构中的表达含义,提出了淀粉结构因子指数这一概念.该值愈高,则说明淀粉分子排列的有序性愈好.通过测定各个淀粉的消化率,统计显示,淀粉结构因子指数与消化率呈良好线性相关性,进一步说明淀粉颗粒结构是调控淀粉消化性质的决定性因素.     

Enzymes of the small intestine of the calf: effect of dietary protein source on the activities of some enzymes in the small intestinal mucosa and digesta

The objective of this study was to examine the effect of dietary protein source on the morphology and enzyme activities in the small intestinal mucosa and digesta of preruminant calves. The control diet contained skim milk powder. Plant proteins from soy concentrate (unhydrolysed or partially hydrolysed) and potato concentrate were incorporated into experimental diets. Duodenal, jejunal and ileal mucosal biopsies and digesta were collected from calves fitted with simple cannulae and continuously infused with milk replacers into the abomasum. Biopsies were used for morphology measurements. The activity of dipeptidylpeptidase IV, aminopeptidases, lactase and alkaline phosphatase was estimated in biopsies and digesta. Incorporating plant protein had a limited effect on the intestinal mucosa. A partial villus atrophy and crypt hyperplasia were noted with the soy concentrate only. Decreases in the activity of dipeptidylpeptidase IV with the potato concentrate diet and of aminopeptidase N and lactase with the hydrolysed soy concentrate diet, were also observed in ileal biopsies. Mucosal enzymes were released in the lumen and most of them accumulated in digesta of the distal small intestine. The activity of aminopeptidase N and lactase in ileal digesta was higher in calves fed the soy and potato concentrate diets than in those fed the control diet. © 2002 Society of Chemical Industry     

Evaluation of Molly model predictions of ruminal fermentation,nutrient digestion,and performance by dairy cows consuming ryegrass-based diets

Several studies have been conducted to improve grazing management and supplementation in pasture-based systems. However, it is necessary to develop tools that integrate the available information linking the representation of biological processes with animal performance for use in decision making. The objective of this study was to evaluate the precision and accuracy of the Molly cow model predictions of ruminal fermentation, nutrient digestion, and animal performance by cows consuming pasture-based diets to identify model strengths and weaknesses, and to derive new digestive parameters when relevant. Model modifications for adipose tissue, protein synthesis in lean body mass and viscera representation were included. Data used for model evaluations were collected from 25 publications containing 115 treatment means sourced from studies conducted with lactating dairy cattle. The inclusion criteria were that diets contained ≥45% perennial ryegrass (Lolium perenne L.), and that dry matter intake, dietary ingredient composition, and nutrient digestion observations were reported. Animal performance and N excretion variables were also included if they were reported. Model performance was assessed before and after model reparameterization of selected digestive parameters, global sensitivity analysis was conducted after reparameterization, and a 5-fold cross evaluation was performed. Although rumen fermentation predictions were not significantly improved, rumen volatile fatty acids absorption rates were recalculated, which improved the concordance correlation coefficient (CCC) for rumen propionate and ammonia concentration predictions but decreased CCC for acetate predictions. Similar degradation rates of crude protein were observed for grass and total mixed ration diets, but rumen-undegradable protein predictions seemed to be affected by the solubility of the protein source as was the intestinal digestibility coefficient. Ruminal fiber degradation was greater after reparameterization, driven primarily by hemicellulose degradation. Predictions of ruminal and fecal outflow of neutral detergent fiber and acid detergent fiber, as well as total fecal output predictions, improved significantly after reparameterization. Blood urea N and urinary N excretion predictions resulted in similar accuracy using both sets of model parameters, whereas fecal N excretion predictions were significantly improved after reparameterization. Body weight and body condition score predictions were greatly improved after model modifications and reparameterization. Before reparameterization, yield predictions for daily milk, milk fat, milk protein, and milk lactose were greatly overestimated (mean bias of 61.0, 58.7, 73.7, and 64.6% of mean squared error, respectively). Although this problem was partially addressed by model modifications and reparameterization (mean bias of 3.2, 1.1, 1.7, and 0.4% of mean squared error, respectively), CCC values were still small. The ability of the model to predict grass digestion and animal performance in dairy cows consuming pasture-based diets was improved, demonstrating the applicability of this model to these productive systems. However, the failure to predict grass digestion based on standard model inputs without reparameterization indicates there are still fundamental challenges in characterizing feeds for this model.     

Amylase addition increases starch ruminal digestion in first-lactation cows fed high and low starch diets

The objective of this study was to evaluate the effect of an exogenous amylase preparation on digestion of low- and high-starch diets in dairy cattle. Rumen and total-tract nutrient digestibility were measured in a 4 × 4 Latin square design with 28-d periods using 4 first-lactation cows cannulated at the rumen and duodenum. Corn silage-based diets had 20 or 30% starch, attained by changing the composition of concentrate, with or without addition of an exogenous amylase preparation. Effects of the enzyme additive were observed on ruminal digestibility but not at the total-tract level. Ruminal digestibility of starch increased from 75% in control to 81% with amylase supplementation. This difference in ruminal starch digestion was compensated postruminally, so that the total-tract digestibility of starch was almost complete and did not differ between treatments. The amylase supplement also increased the true ruminal digestibility of organic matter but did not affect microbial N flow to the duodenum. Amylase supplement reduced the proportion of acetate and butyrate and increased that of propionate, particularly in the high-starch diet, where it tended to increase the concentration of total volatile fatty acids in the rumen. Other effects were a higher amylase activity in the solid-associated microbial community and a tendency for lower numbers of protozoa. In contrast, we observed no changes in intake, production, dry matter and fiber (neutral detergent fiber and acid detergent fiber) digestibility, or ruminal digestion, and no or small changes on selected fibrolytic and amylolytic bacteria and on the microbial community in general. We conclude that the exogenous amylase improved starch digestion in the rumen in first-lactation cows with moderate intake and production levels.     

馕制品中淀粉消化特性及生物活性物质的研究

本文以新疆馕和新疆馒头为样品,主要通过模拟体外消化系统来研究馕的淀粉消化特性,并与馒头的淀粉消化特性进行比较。研究结果如下：馕中的游离葡萄糖和总淀粉含量都略高于馒头,淀粉水解曲线走向大致相似,在肠道消化的前20min淀粉水解率迅速升高,而后逐渐趋于平缓;从总体的淀粉水解速率来看,馒头的淀粉水解率显著高于馕;馕的快消化淀粉率（RDS）明显低于馒头,慢消化淀粉率(SDS)略高于馒头,抗性淀粉（RS）明显高于馒头;馕的淀粉水解指数、血糖生成指数和总类胡萝卜素的含量低于馒头;馕中多酚和黄酮含量高于馒头;总体来说,馕淀粉消化率低于馒头,且馕中生物活性物质更加丰富。     

Modelling starch digestion in sweetpotato with biphasic digestograms

The kinetics of starch digestion in 20 sweetpotato samples obtained from Papua New Guinea were investigated using an in vitro procedure based on glucometry. Irrespective of the cultivars (3-mun, Carot kaukau, Wahgi besta, Nillgai, Baiyer kaukau, and 1-mun), provinces, farmers and locations, the samples exhibited biphasic digestograms, possibly due to initial impediments to amylolysis and/or transport of digestion products by non-starch components (e.g. plant cell walls). The biphasic digestograms were segmented into two monophasic digestograms using a second-order polynomial (average r² = 0.723; p < 0.001), and a modified first-order kinetic model adequately described the digestograms (average r² = 0.984, p < 0.001; mean relative deviation modulus, MRDM, =8). Generally, the digestion rate constants (initial, K_i = 3.2-5.2 × 10⁻³ min⁻¹; final, K_f = 3.8-18.4 × 10⁻³ min⁻¹) indicated faster digestion during the final segment after the initial impediments to digestion had possibly been overcome. K_i was significantly (p < 0.05) different among the samples, which did not significantly (p < 0.05) differ in K_f. A logistic model, which treated each digestogram as a single process, also adequately described the biphasic behaviours (average r² = 0.994, p < 0.001; mean relative deviation modulus, MRDM, =15). The digestion parameters from the segment and logistic approaches significantly (p < 0.05) differed among the sweetpotato samples. The rate of digestion from the logistic model was significantly (p < 0.05) related to the initial and final rates of digestion from the segment approach (K = 3.99 K_i + 0.65 K_f; r² = 0.456; p < 0.001). Irrespective of the approach, maximum starch digestion was less than 100% in some samples to indicate the presence of resistant starch type 1, 2 or both. The present study is the first to model biphasic starch digestograms.     

Effect of corn particle size on site and extent of starch digestion in lactating dairy cows

Two experiments were conducted to determine the effects of corn particle size (CPS) on site and extent of starch digestion in lactating dairy cows. Animals were fitted with ruminal, duodenal, and ileal cannulas. Dry corn grain accounted for 36% of dry matter intake. In experiment 1, 6 cows were used in a duplicate 3 x 3 Latin square design. Semiflint corn was used. Corn processing methods were grinding, medium rolling, and coarse rolling. The mean particle size of the processed corn was 730, 1807, and 3668 microm, respectively. Rumen digestibility of starch linearly decreased from 59% with ground corn to 36% with coarsely rolled corn. Similarly, small intestine digestibility linearly decreased with increased CPS, and consequently, the amount of starch digested in the small intestine was not affected by corn processing. In experiment 2, 4 cows were used in a 2 x 2 crossover design. Dent corn was used. Corn processing methods were grinding and coarse rolling. The mean particle size of the processed corn was 568 and 3458 microm, respectively. Rumen digestibility of starch decreased from 70% with ground corn to 54% with coarsely rolled corn. Small intestine digestibility of starch was not significantly affected by CPS, and the amount of starch digested in the small intestine tended to be greater for rolled than for ground corn. In both experiments, starch total tract digestibility decreased with increased CPS. In conclusion, CPS is an efficient tool to manipulate rumen degradability of cornstarch. In midlactation cows, the decrease in the amount of starch digested in the rumen between grinding and coarse rolling is partly compensated for by an increase in the amount of starch digested in the small intestine with dent genotype, but with semiflint genotype postruminal digestion is not increased and rumen escape starch is not utilized by the animal.     

Synthesis and in vitro digestion of resistant starch type III from enzymatically hydrolysed cassava starch

Resistant starch type III (RS III) was synthesised from cassava starch by autoclaving followed by debranching with pullulanase, at varied concentrations (0.4–12 U g^?1) and times (2–8 h), and recrystallisation (?18 to 90 °C for 1–16 h). The highest RS III yield (22 g/100 g) was obtained at an enzyme concentration of 4 U g^?1 after 8 h incubation, followed by recrystallisation at 25 °C for 16 h. Varying the recrystallisation conditions indicated that higher RS III yields (30–35 g/100 g) could be obtained at 90 °C within 2 h. Thinning cassava starch using α‐amylase prior to debranching using pullulanase did not further increase the RS III content. In vitro digestion data showed that whereas 44% RS III was digested after 6 h, the corresponding value for cassava starch was 89%.     

菊糖对马铃薯淀粉糊流变特性及体外消化的影响

为了研究菊糖对马铃薯淀粉糊流变特性及体外消化的影响,以马铃薯淀粉为原料,通过流变仪测试和体外酶解等方法测定菊糖-马铃薯淀粉共混体系的特性变化。流变仪测试结果表明:在试验的菊糖添加量范围内,菊糖-马铃薯淀粉共混糊的流变学特性均符合幂率模型,为假塑性流体;菊糖的添加在一定程度上降低了淀粉糊黏度,且随着添加量的增加,这一趋势加大。体外酶解结果表明:菊糖可以在一定程度上抑制马铃薯淀粉的水解速度及程度,且随着菊糖添加量的增加其抑制程度也相应增加;水解指数HI及预测血糖值e GI均随着菊糖添加量的增加而逐渐降低;在菊糖最大添加量时(菊糖与淀粉配比为1∶5),菊糖-淀粉共混体系的水解率、HI和e GI值分别由原淀粉的70%、57.87和71.48降至50%、42.74和63.17。研究结果提示适量的菊糖不仅可以改善马铃薯淀粉糊的流变性能,还可以降低其血糖指数。     

An evaluation of Molly cow model predictions of ruminal metabolism and nutrient digestion for dairy and beef diets

Model evaluation, as a critical process of model advancement, is necessary to identify adequacy and consistency of model predictions. The objectives of this study were (1) to evaluate the accuracy of Molly cow model predictions of ruminal metabolism and nutrient digestion when simulating dairy and beef cattle diets; and (2) to identify deficiencies in representations of the biology that could be used to direct further model improvements. A total of 229 studies (n = 938 treatments) including dairy and beef cattle data, published from 1972 through 2016, were collected from the literature. Root mean squared errors (RMSE) and concordance correlation coefficients (CCC) were calculated to assess model accuracy and precision. Ruminal pH was very poorly represented in the model with a RMSE of 4.6% and a CCC of 0.0. Although volatile fatty acid concentrations had negligible mean (2.5% of mean squared error) and slope (6.8% of mean squared error) bias, the CCC was 0.28, implying that further modifications with respect to volatile fatty acid production and absorption are required to improve model precision. The RMSE was greater than 50% for ruminal ammonia and blood urea-N concentrations with high proportions of error as slope bias, indicating that mechanisms driving ruminal urea N recycling are not properly simulated in the model. Only slight mean and slope bias were exhibited for ruminal outflow of neutral detergent fiber, starch, lipid, total N, and nonammonia N, and for fecal output of protein, neutral detergent fiber, lipid, and starch, indicating the mechanisms encoded in the model relative to ruminal and total-tract nutrient digestion are properly represented. All variables related to ruminal metabolism and nutrient digestion were more precisely predicted for dairy cattle than for beef cattle. This difference in precision was mostly related to the model's inability to simulate low forage diets included in the beef studies. Overall, ruminal pH was poorly simulated and contributed to problems in ruminal nutrient degradation and volatile fatty acid production predictions. Residual analyses suggested ruminal ammonia concentrations need to be considered in the ruminal pH equation, and therefore the inaccuracies in predicting ruminal urea N recycling must also be addressed. These modifications to model structure will likely improve model performance across a wider array of dietary inputs and cattle type.     

浸泡和超高压预处理对米饭中淀粉消化特性的影响

采用体外模拟消化实验,通过测定米饭中快速消化淀粉(RDS)、慢速消化淀粉(SDS)和抗性淀粉(RS)相对含量的变化,对浸泡(水、0.4%柠檬酸溶液)和超高压(200～600MPa)预处理对米饭消化特性的影响进行了研究。结果表明:浸泡和超高压预处理能提高米饭淀粉中快速消化淀粉和慢速消化淀粉的含量,降低抗性淀粉的含量,提高米饭的消化特性。      

In vitro starch digestion and technological properties of spaghetti fortified with lupin protein isolate

Spaghetti commonly made with durum wheat, typically lacks essential amino acids and with low fibre. Legumes offer potential to improve these properties and lupin is a good choice because it is cheaper with fewer antinutritional compounds than other legumes. Spaghetti was prepared with 0%, 5%, 17% and 30% lupin protein isolate (LPI) using both single-screw (SSEP) and twin-screw extrusion (TSEP). LPI increased protein up to 129%, reduced cooking time, water absorption and cooked firmness while stickiness and cooking loss were increased, especially using TSEP. LPI made the dried pasta more red and yellow and decreased brightness. The percentage of starch digested under in vitro conditions was reduced using 17%LPI with TSEP and 30%LPI with SSEP compared vs. control. Microscopy revealed changes in structure by LPI which may explain impacts on technological properties and digestion. Inclusion of LPI in pasta represents a potential approach for a low-cost improvement of nutritional value of spaghetti and potentially reducing its starch digestibility.     

Effect of supplemental yeast culture and dietary starch content on rumen fermentation and digestion in dairy cows

The objectives of this experiment were to evaluate the effect of feeding a culture of Saccharomyces cerevisiae on rumen metabolism and digestibility when cows are fed diets varying in starch content. Four lactating Holstein cows were assigned to a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Treatments were low starch (LS; 23% of diet DM) and no yeast culture (YC; LS-control), LS and 15 g of YC/d (LS-YC), high starch (HS; 29% of diet DM) and no YC (HS-control), and HS and 15 g of YC/d (HS-YC). Periods lasted 28 d, with the last 9 d for data collection. Days 20 to 24 were used to determine production, nutrient flow, and digestibility. On d 25, 3 kg of corn grain DM was placed in the rumen 1 h before the morning feeding, and yields of milk and milk components were measured after the challenge. Blood was sampled −1, 3, 7, and 11 h relative to the morning feeding on d 24 and 25. Rumen pH was measured continuously on d 24 and 25. Rumen papillae were collected on d 24 and 28 to quantify mRNA expression of select genes. Supplementing YC increased yields of milk (26.3 vs. 29.6 kg/d), energy-corrected milk (ECM; 26.5 vs. 30.3 kg/d), fat (0.94 vs. 1.08 kg/d), true protein (0.84 vs. 0.96 kg/d), and ECM/dry matter intake (1.15 vs. 1.30) compared with the control but did not affect dry matter intake (22.6 vs. 22.9 kg/d). Cows fed HS had increased milk true protein percentage (3.18 vs. 3.31%) and yield (0.87 vs. 0.94 kg/d) compared with cows fed LS. Feeding HS-YC increased the proportion of dietary N incorporated into milk true protein from 24.9% in the other 3 treatments to 29.6%. Feeding HS increased the concentration of propionate (21.7 vs. 32.3 mM) and reduced that of NH₃-N (8.3 vs. 6.7 mg/dL) in rumen fluid compared with the control, and combining HS with YC in HS-YC tended to increase microbial N synthesis compared with LS-YC (275 vs. 322 g/d). Supplementing YC to cows fed HS reduced plasma haptoglobin and rumen lactate concentrations, increased mean rumen pH, reduced the time with pH <6.0, and prevented the decrease in rumen neutral detergent fiber digestion caused by HS. Cows fed HS had less total-tract digestion of organic matter (73.9 vs. 72.4%) because of reduced acid detergent fiber (57.6 vs. 51.7%) and neutral detergent fiber (60.9 vs. 56.7%) digestibility. Production performance after the challenge was similar to that before the challenge, and YC improved yield of ECM. After the challenge, supplementing YC tended to reduce rumen lactate concentration compared with the control and reduced haptoglobin in cows fed HS. Feeding HS but not YC increased expression in rumen papillae of genes for receptors (FFAR2 and FFAR3) and transporter (SLC16A3) of short-chain fatty acids but did not affect genes involved in transport of Na⁺/H⁺ or water or in inflammatory response. Supplementing YC to dairy cows improved lactation performance in diets containing low or high starch, and mechanisms might be partially attributed to improvements in rumen pH, digestion of fiber, microbial N synthesis, and reduction in acute phase response.     

Prebiotic effect of resistant starch from Vigna unguiculata (L.) Walp. (cowpea) using an in vitro simulated digestion model

There has been growing interest in the use of resistant starch (RS) as a prebiotic for physiological benefits and to reduce the risk of chronic diseases. In this study, RS was isolated from samples of five cowpea cultivars (DT129-4, TVU 11424, PAN 311, Fahari and Bechuana White) seeds to determine their potential prebiotic effects, and proximate and mineral composition. Results obtained showed samples of five cowpea cultivars to be high in protein (18.0–28.7%) and carbohydrates (54.9–66.0%) and low in fat (0.6–3.7%). The RS from cowpea samples ranged between 9.3 and 12.1% with cultivar DT129-4 having the highest amount. Fermentation of RS using mixed and pure cultures was done, and bacterial growth was monitored over a 24-h period. Resistant starch isolated from all cowpea samples fulfilled the criteria to be classified as a prebiotic which have a wide range of beneficial effects on the host, with cultivar DT129-4 showing the most prebiotic potential amongst cowpea samples tested.     

茶多酚对黑色冲调粉抗氧化及淀粉消化特性的影响

通过DPPH自由基清除率、总抗氧化、总还原力、淀粉水解曲线探讨茶多酚对黑色冲调粉抗氧化和消化特性的影响及其变化。研究结果表明:茶多酚的添加使黑色冲调粉的指标发生显著性变化(P0.05),增强了DPPH自由基清除能力、总还原力、总抗氧化,降低了淀粉水解率。当茶多酚添加量为0.040%时,黑色冲调粉的DPPH自由基清除能力、总还原力的吸光度和总抗氧化能力分别增加了4.6%,0.58,8.83U/g,黑色冲调粉的淀粉水解率下降了24.98%。     

银川市2015~2020年市售淀粉镉含量检测及消解方法优化

分析银川市2015~2020年售淀粉中镉含量,选择全自动消解仪消解代替传统电热板加热法预处理实验样品,电感耦合等离子体原子发射光谱法测定淀粉中镉的含量。结果表明,该方法在标线范围中标准曲线线性较好,检出限为0.0063 mg/L,定量限为0.001 mg/L,RSD和回收率分别为2.198%,99.16%~107.3%,准确度及精密度较高,与《食品安全国家标准食品中镉的测定》(GB 5009.15—2014)方法检测结果一致,且本方法精密度更优,可以满足使用需求。采集的淀粉样品254份中,重金属镉检出份数为224份,总检出率为88.2%;重金属镉的总检出范围为0.0097~0.1644 mg/kg,均值为0.0631 mg/kg;相较于《食品安全国家标准食品中污染物限量》(GB 2762—2017)中对重金属镉元素的限值0.1 mg/kg,总超标份数为25份,其总超标率为9.4%。