Dietary Starch Level Research Articles

Effects of dietary ARA, DHA, and carbohydrates levels on gilthead sea bream liver and intestine oxidative stress, tissue histomorphology, and gut microbiota

The present study aims evaluate the oxidative status, histomorphology of liver and intestine, and intestinal microbiota modulation of gilthead sea bream juveniles (initial body weight = 47.5 g) fed four isoproteic and isolipidic diets (47% protein; 18% lipids) with high or low gelatinized starch levels (20% or 5%; diets HS or LS, respectively) and different dietary ARA or DHA content (2.3/0.3 or 0/2.6, diets ARA or DHA, respectively).ARA-rich diets reduced liver and intestine lipid peroxidation (LPO) circa 12 and 66%, respectively. Dietary ARA also increased liver glutathione redox status (total, reduced (GSH) and oxidized glutathione (GSSG)) circa of 35% but only in the HS diets. Independently of dietary starch level, dietary ARA also reduced GSSG content (80 and 63 nmol g−1 tissue) and oxidative stress index (OSI) (8.7 and 7%) in the intestine. Fish fed DHA diets had increased hepatic superoxide dismutase (SOD) (749.1 and 489.1 U mg protein−1) and glutathione reductase (GR) (3.7 to 1.9 mU mg protein−1) activities. In the intestine, dietary ARA or DHA did not induce alterations in the activity of the antioxidant enzymes. Dietary starch improved liver OSI (1.5%), increased intestinal GSSG (80 and 128 nmol g−1 tissue), and decreased intestinal LPO values (104 nmol MDA g−1 tissue) in fish fed the DHA diets. Fish fed the HS diets had increased hepatic glucose-6-phosphate dehydrogenase (G6PDH) (171.4 and 166 mU mg protein−1), GR (2 and 3.71 mU mg protein−1), and glutathione peroxidase (GPX, only in DHA diets) (63.8 mU mg protein−1) activities, but decreased GR (27.2 and 27.6 mU mg protein−1) and SOD (2089.7 and 2158.8 U mg protein−1) activities in the intestine.Diet composition did not induce major histomorphological alterations in the distal intestine. Nevertheless, the HS diets, especially when combined with DHA, promoted hepatocyte hypertrophy and alterations in nuclei position.Compared to the DHA diets, in fish fed the ARA diets, mucosa bacterial profile had a reduced number of operational taxonomic units (10.3 and 12.0), richness (0.6 and 0.7), and diversity (2.2 and 2.3), and higher similarity between bacterial communities (85.0 and 80.4%).In conclusion, fish fed high dietary ARA presented lower hepatic and intestinal LPO and fewer hepatocyte morphological alterations than fish fed high DHA diets. Furthermore, interactive effects between dietary starch and DHA on liver and intestine GSH metabolism, antioxidant enzymes, LPO susceptibility, and liver histomorphology may be attenuated by a balanced ARA/DHA dietary ratio.

Growth of Pancreas and Intestinal Enzyme Activities in Growing Goats: Influence of a Low-Protein Diet

A dependence between dietary protein and starch levels flowing to the duodenum has been characterized in monogastric animals for optimal enzymatic secretions of the pancreas, but those in ruminants remain unclarified. The present experiment was conveyed to assess the pancreas growth and mRNA expression of the small intestine enzymes in growing goats fed a low-protein diet. Twenty-four Liuyang goats (19.55 ± 3.55 of body weight (BW)) and aged approximately 8 months were randomly assigned to either a control protein diet (NP: 10.77% CP) or a low-protein diet (LP: 5.52% CP) for 70 days. The results show that no statistical differences (p > 0.05) were observed in the pancreas growth indices between the groups. Pancreas and small intestine α-amylase and lipase activities were unaffected (p > 0.05) by the LP diet, while activities of trypsin and chymotrypsin were decreased (p < 0.05). The LP diet reduced (p < 0.05) the mRNA expressions of trypsin and chymotrypsin in the duodenum and jejunum, and had no effects (p > 0.05) on the mRNA expressions of α-amylase and lipase. Goats fed with the LP diet had higher (p < 0.05) concentrations of cholecystokinin and insulin than those fed with the NP diet. In conclusion, feeding an LP diet (5.52% CP) had no profound influence on pancreas growth and digestive enzyme synthesis in goats.

An evaluation of the growth, blood biochemistry, hepatic glucose metabolism and hepatocyte apoptosis in the genetically improved farmed tilapia Oreochromis niloticus fed diets with distinct protein to corn starch ratios

This study was performed to evaluate the effects of dietary distinct protein to starch ratios on the growth, feed utilization, blood biochemistry, hepatic glucose metabolism and hepatocyte apoptosis of Nile tilapia Oreochromis niloticus. Three iso-lipidic (ca 6.56%) diets were formulated with elevated corn starch levels at the cost of protein provision, being designated as diets P40S5 (40.4% protein and 4.62% starch), P30S25 (30.4% protein and 24.2% starch) and P20S50 (19.9% protein and 48.6% starch). Tilapia juveniles (initial mean body weight, 32.0 g/fish) were assigned to 12 rectangular tanks (250 L each) with 20 fish per tank and fed the experimental diets to apparent satiation for 8 weeks. The results showed that either excess (40%) or insufficient (20%) amount of dietary protein impaired the growth of tilapia. Excess dietary protein led to unsatisfactory protein catabolism (lower protein efficiency ratio and protein productive value, and higher mRNA levels of hepatic glutamic-pyruvic transaminase 1 and glutamic-oxaloacetic transaminase paralogs), while insufficient amount of protein resulted in lower whole-body protein percentage. An increase in dietary starch from 5% or 25% to 50% was associated with enhanced lipid and glycogen storages in the liver of tilapia. Consistently, dietary starch reception up to 50% upregulated the expression of hepatic representative genes involved with glycolysis (glucokinase and phosphofructokinase muscle type a) and lipogenesis (acetyl-CoA carboxylase α and fatty acid synthase) while downregulated the expression of the gluconeogenic glucose-6-phosphatase catalytic subunit paralogs. TUNEL staining suggested that stronger apoptosis signal was recorded at the bile duct epithelium of the P20S50 fish. Concomitantly, plasma bile acid level nearly doubled, and an incidence (50%) of ‘green liver’ was observed in this treatment as compared with the P40S5 and P30S25 fish, indicating that bile acid metabolism disorder might be induced. Though plasma glucose (4.66–5.11 mmol/L) was not responsive to different treatments, advanced glycation end-products accumulated in the blood of the P20S50 fish, suggesting that 50% starch reception was probably associated with the progression of diabetes-associated pathologies. The overall results in this study suggested that tilapia might possess capability to tolerate dietary corn starch level up to 50% in a short-term exposure, whereas a long-term exposure might induce detrimental effects on liver functions.

Effects of dietary arachidonic acid and docosahexanoic acid at different carbohydrates levels on gilthead sea bream growth performance and intermediary metabolism

A growth trial was performed to assess the interactive effects of high dietary levels of arachidonic acid (ARA) or docosahexaenoic acid (DHA), and carbohydrates on growth performance, feed utilization, proximate composition, plasma metabolites, and intermediary metabolism. Four isoproteic (47% crude protein) and isolipidic (18% crude lipids) diets were formulated for gilthead sea bream juveniles (47.5 g of initial mean body weight) to include low or high gelatinized starch (5 and 20% starch; LS and HS diets, respectively) and different dietary ARA/DHA content (2.3/0.3 and 0/2.6; ARA and DHA diets, respectively). Dietary ARA/DHA content did not affect growth performance or feed utilization. However, dietary starch inclusion increased feed efficiency, protein efficiency ratio, and energy retention (% intake). Dietary ARA/DHA profile did not affect the whole-body composition, but dietary starch increased whole-body dry matter, lipid, and gross energy content and decreased protein content. Low dietary ARA/DHA ratio increased plasma total protein and total lipids, triglycerides, and very-low-density lipoprotein cholesterol (VLDL) and decreased high-density lipoprotein cholesterol (HDL) and low-density lipoprotein cholesterol (LDL), independently of the dietary starch level. On the other hand, in LS diets, total cholesterol levels were lower in fish fed the diet rich in DHA than those fed with ARA. HS diets increased glucose, total protein and lipids, triglycerides, and VLDL plasmatic values, and decreased HDL. HS diets increased the carbohydrates intermediary metabolism and lipogenic enzymes. ARA and HS increased fatty acid desaturase 2 (FADS2) and decreased elongation of very long-chain fatty acid 5 protein (ELOVL5) in the liver, and only HS decreased ELOVL5 in the intestine. The muscle fatty acid content followed the dietary fatty acid profile, but ARA, EPA, and DHA content were increased in LS diets. In conclusion, few interactions between ARA or DHA and dietary digestible carbohydrates were found. The results indicate that at least in the presence of high ARA levels the n-3 LC-PUFA requirements were fulfilled with 0.5% EPA + DHA and gilthead sea bream tolerates well dietary inclusion of 20% starch.

Molecular characterization and nutritional regulation of sodium-dependent glucose cotransporter 1 (Sglt1) in blunt snout bream (Megalobrama amblycephala)

Fish has poor utilization capacity for glucose metabolism. The possible reasons are related to the core regulatory elements of glucose metabolism: transport proteins. Studies on the species and functions of Sglt1 in aquatic animals are scarce, therefore further studies are needed. In this study, the full length of blunt snout bream (Megalobrama amblycephala) sglt1 (Masglt1) was 2965 bp including 5′-UTR region of 168 bp and a 3′-UTR region of 820 bp. Masglt1 have a highest sequence homology in Cypriniformes fish. MaSglt1 protein was identified as a transmembrane protein with 14 α-helix structures locating plasma membrane by the methods of predicted tertiary structure and immunohistochemical staining. MaSglt1 protein has a hollow channel forms which could be specifically coupled with two Na+ ions to recognize glucose and carry out transmembrane transport. High sglt1 mRNA was found in the intestine and kidney. The mRNA levels of intestinal sglt1 had a positive correlation with dietary starch levels at 3 h after feeding, and the mRNA was significantly higher than that at 24 h, however, the mRNA levels of renal sglt1 presented results opposite to those of intestinal sglt1. The mRNA levels of renal sglt1 had a positive correlation with dietary starch levels at 24 h after feeding, and the expression was significantly higher than that at 3 h. These results confirmed that Masglt11 was mainly found in the intestine and kidney and was located in the cell membrane, playing a role in glucose homeostasis.

Feeding diets varying in starch concentration supplemented with palmitic acid or stearic acid: Effects on performance, milk fatty acid profile, and metabolic parameters of postpartum dairy cows

The objective of this study was to investigate the effects of dietary fat supplement rich in palmitic acid or stearic acid on milk yield and composition, fatty acid profile, energy partitioning, and metabolic parameters of dairy cows fed low or high starch diets from d 1 to 28 of the postpartum period. Forty-four multiparous Holstein cows were used in a complete randomized block (based on parity, and previous 305-d milk yield); 2 × 2 arrangement with two dietary starch levels [high starch (HS); 260 g/kg of diet dry matter (DM) versus low starch (LS); 210 g/kg of diet DM] with either palmitic acid (PA) or stearic acid (SA) supplementation at the level of 15 g/kg of diet DM. A basal close-up diet (6.19 MJ/kg of diet DM, NEL; 200 g/kg starch) was fed to animals prior to calving. Regardless of the fatty acid (FA) type, cows fed HS diets had a higher dry matter and NEL intake, milk protein and lactose content, and a more positive energy balance than cows fed LS diets during the postpartum period. Compared with HS diets, LS diets reduced energy toward body reserves and maintenance as a fraction of the NEL intake. Although there was no main effect of PA or SA supplement on intake and energy balance, the effect of fat supplementation depended on dietary starch levels for milk yields and milk energy as a fraction of the NEL intake. Stearic acid increased milk yield in HS diets while PA tended to increase yield in LS diets. Supplementation of PA partitioned less energy toward milk (and more energy for maintenance) in HS diets than LS diets. Moreover, the C16:0 FA concentration in milk fat was higher, and the polyunsaturated FA (PUFA) and C18:1 cis-9 FA were lower in PA supplemented cows fed HS diets but not cows fed LS diets. High starch rations increased de novo FA concentrations in milk and decreased C18:0 and preformed FA concentrations compared with LS diets. Also, HS diets tended to have higher levels of insulin and lower levels of beta-hydroxybutyrate (BHBA) than LS diets. In conclusion, the HS diet was more beneficial to improving the energy balance (EB) of dairy cows than LS diets during the early postpartum period. Also, interactions between dietary starch levels and FA supplement for the variables measured in the current study (e.g. milk yield or FA profile) indicate that the response to fat supplements rich in specific FA differed on the basis of dietary starch concentrations.

Daily alternation of the dietary starch level in Holstein dairy cows

The aim of this study was to investigate the effect of controlled daily alternations in dietary starch level on changes in rumen environment, blood, urine, and milk metabolites of dairy cows. Six multiparous mid-lactation Holstein cows were used in a replicated 3 × 3 Latin square design with 14-d periods and 3 alternating levels of dietary starch as treatments. Each 14-d period consisted of a 7-d baseline period and 7-d alternating period where diets alternated day to day. During the baseline period, all cows were fed a control diet containing 21% starch (dry matter basis). During the alternating period, the control diet was replaced with 1 of the 3 experimental diets on d 8, 10, 12, and 14. The 3 experimental diets contained 28% (low), 35% (medium), and 42% (high) starch (dry matter basis). At d 7 (baseline), 8 (ALT1), and 14 (ALT4) of each period, rumen fluid, blood, urine, and quarter milk (i.e., back right quarter) samples were collected at -0.5, 1, 2.5, 4, 5.5, and 7 h relative to morning feeding (0800 h). No differences were observed in dry matter intake, milk yield, and milk chemical composition. Rumen medial pH was lower in the high alternation level compared with the low or medium alternation levels at ALT1 but did not differ among starch alternation levels at ALT4. Similarly, the difference between rumen pH in medial and ventral contents was reduced at ALT1 with high alternation level but was not affected at ALT4. Total volatile fatty acid (VFA) concentrations were higher in the rumen medial fluid of the high alternation level at 7 h relative to morning feeding compared with those from the low and medium alternation levels. Similarly, total VFA concentrations constantly increased and were the highest in the ventral rumen fluid at 7 h relative to morning feeding, although no differences were detected among starch alternation levels. In both rumen medial and ventral fluids, the high alternation level showed higher propionate and lower acetate proportions compared with low and medium alternation levels. No differences in blood pH were detected among starch alternation levels. However, glucose concentrations tended to be higher in cows from the high alternation level. l-Lactate concentrations in blood were higher in ALT1 than in ALT4 but were not affected by the starch alternation level. In urine, no differences in pH or l-lactate concentrations were detected among alternation levels (i.e., low, medium, and high). Similarly, no differences in milk pH were detected among alternation levels. According to these results, it seems that the daily dietary starch alternation from 21% up to 42% (dry matter basis) is able to affect the ruminal fluid, especially during the first alternation. However, these changes in rumen fluid did not cause any effect on the variables measured in blood, urine, or milk. This study indicates that cows can cope with day-to-day alternations in type of rumen fermentable organic matter; however, longer-term effects on performance and health should be addressed in future studies.

Dietary starch level and rumen-protected methionine, lysine, and histidine: Effects on milk yield, nitrogen, and energy utilization in dairy cows fed diets low in metabolizable protein

Our objective was to investigate the interactions between starch level and rumen-protected Met, Lys, His (RP-MLH) on milk yield, plasma AA concentration, and nutrient utilization in dairy cows fed low metabolizable protein diets (mean = -119 g/d of metabolizable protein balance). Sixteen multiparous Holstein cows (138 ± 46 d in milk, 46 ± 6 kg/d in milk) were used in a replicated 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. Dietary starch level varied by replacing (dry matter basis) pelleted beet pulp and soyhulls with ground corn resulting in the following treatments: (1) 20% pelleted beet pulp and 10% soyhulls (reduced starch = RS), (2) RS plus RP-MLH (RS+AA), (3) 30% ground corn (high starch = HS), and (4) HS plus RP-MLH (HS+AA). Dietary starch concentrations averaged 12.3 and 34.4% for RS and HS basal diets, respectively. Diets were supplemented with RP-MLH products to supply digestible Met, Lys, and His. Compared with RS and RS+AA diets, HS and HS+AA diets increased yields of milk (37.9 vs. 40.1 kg/d) and milk protein (1.07 vs. 1.16 kg/d) and decreased dry matter intake (25.9 vs. 25.2 kg/d), milk urea N (12.6 vs. 11.0 mg/dL), and plasma urea N (13.3 vs. 11.6 mg/dL). Milk N efficiency was greater in cows fed the HS and HS+AA than RS and RS+AA diets (28.9 vs. 25%), and RP-MLH supplementation improved milk true protein concentration. Starch level × RP-MLH interactions were observed for plasma concentrations of Arg and Lys, with RP-MLH being more effective to increase plasma Arg (+16%) and Lys (+23%) when supplemented to the RS than the HS basal diet. Replacing pelleted beet pulp and soyhulls with ground corn lowered the plasma concentrations of all essential AA except Met and Thr. In addition, the plasma concentrations of His and Met increased with RP-MLH. The apparent total-tract digestibilities of neutral and acid detergent fiber were lower, and those of starch and ether extract greater in cows offered the HS and HS+AA diets than RS and RS+AA diets. Urinary excretion of urea N decreased by replacing pelleted beet pulp and soyhulls with ground corn. Enteric CH4 production, CH4 yield, and CH4 intensity all decreased in the HS and HS+AA versus RS and RS+AA diets. Diets did not affect the intakes of gross energy, metabolizable energy, and net energy of lactation. In contrast, digestible energy intake increased with feeding the RS and RS+AA diets, whereas CH4 energy decreased in cows fed the HS and HS+AA diets. Supplementation with RP-MLH had no effect on energy utilization variables. Overall, the lack of interactions between dietary starch level and RP-MLH supplementation on most variables measured herein showed that the effects of starch intake and RP-MLH were independent or additive.

Effects of dietary starch levels on growth, feed utilization, glucose and lipid metabolism in non-transgenic and transgenic juvenile common carp (Cyprinus carpio L.)

This experiment investigated the effects of dietary starch on growth performance, feed utilization, glucose and lipid metabolism of non-transgenic and growth hormone (GH) transgenic juvenile common carp (Cyprinus carpio L.). Transgenic common carp (TG fish) and non-transgenic (NT fish) were fed diets with five starch levels (0, 10%, 20%, 30%, 40%). After 41 days, TG fish showed higher growth and feed utilization at low-starch diets, while similar growth, lower feeding rate (FR) and slightly higher feed efficiency (FE) was observed at high-starch diets. Lower plasma glucose level and hepatic glycogen content were observed in TG fish, which could be related to the higher glycolysis (high gene expression of hexokinase (hk), p < 0.01) and gluconeogenesis (high gene expression of fructose-1,6-bisphosphatase (fbpase), p < 0.01; glucose-6-phosphatase (g6pase), p < 0.01) of TG fish. Compared to NT fish, weakened fat synthesis (lower gene expression of fatty-acid synthase (fas), p <0.01; acetyl-CoA carboxylase 1 (acc1), p < 0.01; acyl-CoA desaturase 1 (scd1), p = 0.011) and enhanced fatty acid oxidation (high gene expression of hormone-sensitive lipase (hsl), p =0.01; carnitine palmitoyl transferase 1a (cpt-1a), p < 0.01), led to the decrease of body lipid content in TG fish. On the other hand, with increased dietary starch, increased body lipid and hepatic glycogen contents were observed in both TG and NT fish, suggesting that high dietary starch levels promoted glycolysis, fat synthesis and inhibited gluconeogenesis, fatty acid β-oxidation. Overall, TG fish showed higher growth performance at low starch diets, and higher ability of glycolysis, fatty acid oxidation and lower lipid synthesis than the NT fish.

Effects of supplementation of nonforage fiber source in diets with different starch levels on growth performance, rumen fermentation, nutrient digestion, and microbial flora of Hu lambs.

The objectives were to evaluate the effects of fiber source and dietary starch level on growth performance, nutrient digestion, rumen parameters, and rumen bacteria in fattening Hu lambs. A total of 360 Hu lambs (BW = 24.72 ± 0.14 kg, 2 months old) were subjected to a 2 × 3 factorial arrangement. Lambs randomly assigned 6 treatments with 6 repetitions (10 lambs per repetition) of each treatment. Six treatments were formulated to include the fiber sources with three starch levels. The experiment lasted a 63 d. The amount of feed, orts, and total feces were sampled on the 42nd day of the experiment. Rumen fluid samples were collected after 2 h of morning feeding on day 56. Rumen contents were collected last day after the selected lambs were slaughtered. Increasing the starch content decreased the digestibility of neutral detergent fiber (NDF, P = 0.005). Increasing the starch level increased the proportions of propionate (P = 0.002) and valerate (P = 0.001) and decreased the proportion of acetate (P < 0.001) and the ratio of acetate to propionate (P = 0.005). The abundance of Fibrobacter succinogenes was affected by an interaction between the fiber source and the starch level (P < 0.001). Fibrobacter succinogenes tended to be greater in lambs fed SH than in lambs fed BP (P = 0.091), which was greater in lambs fed high starch levels than in lambs fed low starch levels (P = 0.014). Increasing the starch level increased Streptococcus bovis abundance (P = 0.029) and decreased total bacteria (P = 0.025). At the genus level, increasing the starch level reduced the abundance of Butyrivibrio_2 (P = 0.020). Nevertheless, the final body weight (BW) and acid detergent fiber (ADF) digestibility were greater (P < 0.01) in lambs fed soybean hull (SH) than in lambs fed BP. The proportion of butyrate was greater (P = 0.005), while the rumen pH was lower (P = 0.001) in lambs fed beet pulp (BP) than in those fed SH. The abundances of Succiniclasticum, Candidatus_Saccharimonas, Ruminococcus_1, and Christensenellaceae_R-7 were greater in lambs fed SH than in those fed BP (P < 0.050), whereas the abundance of Fibrobacter was lower (P = 0.011). The predominant microbial phyla in all of the groups were Firmicutes, Bacteroidetes, and Fibrobacteres. Changing the starch level for fiber sources mainly changed the rumen community in terms of the phylum and genus abundances. Lambs fed SH with low starch level increased the final BW without affecting total volatile fatty acids (TVFA) concentrations.

High dietary starch impairs intestinal health and microbiota of largemouth bass, Micropterus salmoides

This study focused on the effects of starch levels on growth performance, intestinal dysbiosis and health of Micropterus salmoides. Three isonitrogenous and isolipidic diets containing different corn starch levels (5%, 10%, 15%) were fed to experimental fish (initial body weight: 8.66 ± 0.04g) for 8 weeks, respectively. The results showed that the 15% starch levels suppressed the growth, decreased the height and width of villus and number of goblet cell in midgut compared with the other groups (P < 0.05). Moreover, plasma endotoxin (PE) and diamine oxidase (DAO) increased significantly with dietary starch levels (P < 0.05). Notably, 15% starch diets up-regulated the expression of Claudin-1 and down-regulated the expression of ZO-1, Claudin-4 and Claudin-5 in intestine (P < 0.05). Meanwhile, fish fed 15% starch diets decreased antioxidant enzyme mRNA levels (Nrf2, CAT and SOD) and activities (SOD and CAT) compared to the other groups (P < 0.05). The increased dietary starch levels upregulated the expression of pro-inflammatory cytokines (IL-8, IL-1β and TNFα) and anti-inflammatory cytokines (IL-10 and TGF-β1) (P < 0.05). Additionally, the abundance of intestinal probiotics (such as Lactobacillus) decreased with the increase of dietary starch level (P < 0.05), while abundance of intestinal potentially pathogenic bacteria (such as Brevundimonas and Ralstonia) increased (P < 0.05). Fish fed 15% starch diet had less concentrations of acetate and butyrate in intestinal digesta than the 5% starch group (P < 0.05). These results suggested that 15% starch diets would impair the intestinal health, suppress immune and antioxidant capacity and finally reduced growth of Micropterus salmoides. The imbalances in intestinal microbiota and the reduced production of short-chain fatty acids (SCFA) may be partly responsible for the loss of intestinal function.

Relationship between feed protein content and faeces nitrogen content in early lactation dairy cows

Relationship between feed protein content and faeces nitrogen content in early lactation dairy cows

PSVI-1 Effects of dietary nonforage fiber sources and starch levels on nutrition digestion and rumen fermentation of fattening Hu lambs

Abstract The primary objectives of this experiment were to study the effects of fiber sources [beet pulp (BP) vs. soybean hull (SH)] and dietary starch levels [low = 22% dry matter (DM), medium = 25% DM, and high = 27% DM] on nutrition digestion, rumen parameters and rumen bacteria in fattening Hu lambs. A total of 360 Hu lambs were assigned a 2×3 factorial arrangements, including a 63-day experimental periods. Six diets were formulated to include two fiber sources and three starch levels, and the samples including feed, feces, rumen contents, and rumen fluids were collected in different experimental periods. Analysis of fiber sources and starch levels was performed using two-way ANOVA by SPSS software version 17.0 (IBM, Armonk, NY, United States). The digestibility of neutral detergent fiber (NDF) declined in (P = 0.005) increasing starch contents. Increasing starch levels increased the concentrations of propionate (P = 0.002) and valerate (P = 0.001) and decreased the concentrations of acetate (P &amp;lt; 0.001) and the ratio of acetate/propionate (P = 0.005). At the genus level, increasing starch levels reduced the abundance of Butyrivibrio_2 (P = 0.020). Nevertheless, the ADF digestibility was greater (P &amp;lt; 0.01) in lambs fed SH than lambs fed BP. The concentrations of butyrate were higher (P = 0.005) while the rumen pH was less (P = 0.001) in lambs fed BP than those fed SH. Fiber sources influenced the abundance of Succiniclasticum, Candidatus_Saccharimonas, Ruminococcus_1 and Christensenellaceae_R-7, which were higher in lambs fed SH compared with those fed BP (P &amp;lt; 0.05). In summary, the interaction of fiber sources and starch levels had no differences on growth performance, and lambs fed SH increased final BW compared lambs fed BP. Fiber sources mainly changed the abundance of cellulolytic bacteria in the rumen community.

246 Effect of increasing levels of dietary starch on equine cecal microbiota

Abstract An experiment was conducted with 6 cecally cannulated horses (524 ± 65.5 kg BW) to evaluate effects of increasing dietary starch on equine cecal microbiota. Starch was supplied via corn pellets and was increased by 0.5 g starch/kg BW/meal every 7 d until horses received 3.5 g starch/kg BW/meal. Throughout the experiment, Smooth Bromegrass hay and water were offered ad libitum. Meals were fed every 6 h, starting at 0600 h. On d 7 of each period, cecal digesta was collected every 2 h for 12 h. Within period, cecal samples for each horse were pooled and DNA was extracted for PCR amplification of the 16 S rRNA gene (V3 and V4 regions) and sequencing via Illumina MiSeq. Alpha and beta diversity were measured. Data were analyzed as a randomized complete block with fixed effect of starch level and random effect of horse (SAS version 9.4). If a horse presented with colic, it was removed from the experiment. Parameters when feeding 1.5 g starch/kg BW/meal were compared between horses which completed the trial and those removed using covariate of 0 g starch/kg BW/meal. Feeding 1.5 g starch/kg BW/meal elicited the greatest changes in microbiota, indicated by reduced (P ≤ 0.02) operational taxonomical units and Faith phylogenetic diversity and different (P ≤ 0.017) beta diversity compared to all other treatments. Across treatments, Firmicutes was the most abundant phyla, followed by Bacteroidetes. Feeding 1.5 g starch/kg BW/meal led to lowest (P ≤ 0.0342) relative abundance (RA) of Prevotella, Treponema, Phascolarctobacterium, and [Prevotella]. Horses that persisted throughout the experiment had reduced (P = 0.0163) RA of Ruminococcus and greater RA of Phascolarctobacterium (P = 0.0057) when consuming 1.5 g starch/kg BW/meal compared to those removed. This is the first report describing effects of gradually increasing dietary starch on equine cecal microbiota in vivo.

Varying starch to fat ratios in pelleted diets: II. Effects on intestinal histomorphometry, Clostridium perfringens and short-chain fatty acids in Eimeria-challenged broiler chickens

ABSTRACT 1. The hypothesis behind the study was that a high dietary starch level (HS) would lead to impaired gut health compared to a low-starch diet (LS) in Eimeria-challenged broilers. The effects of two diets with different starch to fat ratios on intestinal histomorphometry, Clostridium perfringens counts and toxin profile, necrotic enteritis prevalence and abundance of short-chain fatty acids (SCFAs) were examined. 2. A total of 1,920 one-day-old Ross 308 broiler chickens were fed one of two isocaloric diets formulated either with high (32:1) or low (2:1) starch to fat ratios from d 10 to 29 of age. Each treatment group had 12 pen replicates containing 80 broilers each. On d 17, the chickens were challenged with Eimeria vaccine strains. Samples were collected on d 16, 21–23 and 29. 3. Whereas villus length increased gradually throughout the study in the HS group, a peak level was reached on d 21–23 in the LS group. On d 29, the HS group had significantly longer villi than the LS group. 4. Caecal SCFA concentrations were higher in the HS group compared to the LS group on d 16. In both groups, the SCFA level peaked on d 21–23, with the most pronounced increase seen in the LS group. 5. The C. perfringens netB:cpa ratio increased from d 16 to 29 in the HS group. C. perfringens counts and necrotic enteritis prevalence were similar between the two groups. 6. Diet affected the dynamics of small intestinal villus length and caecal SCFA abundance. These findings suggest that structural remodelling of the small intestine is an adaptation to different dietary starch levels, and that caecal SCFA abundance is associated with the availability of substrate for the microbiota in the posterior intestinal segments. Chickens adapted to higher levels of dietary starch might be more robust against Eimeria infections due to increased mucosal surface area. Studies with other dietary starch sources are required to clarify the impact of dietary starch levels on intestinal health in Eimeria–challenged broilers.

Varying starch to fat ratios in pelleted diets: I. Effects on nutrient digestibility and production performance in Eimeria–challenged broiler chickens

ABSTRACT 1. The hypothesis was that a diet with a high starch to fat ratio (HS) impairs nutrient digestibility and growth performance, as compared to a diet with a low starch to fat ratio (LS) in Eimeria–challenged broilers. From days 10 to 29, 12 replicate pens of birds were given isocaloric and isonitrogenous steam-pelleted diets with either HS or LS, by replacing the wheat starch in one diet by a mixture of rapeseed oil and inert sand in the other. On d 17, a 10-fold dose of live vaccine strains of Eimeria spp. was administered via drinking water. Ileal samples were collected on days 16 and 29. 2. Starch content in the ileum tended to be higher on d 16 and was significantly higher on d 29 in the HS group. 3. The HS diet did not induce exceedingly high levels of starch in the ileum, suggesting there was no starch overload in the gut. Ileal starch digestibility was improved with increasing dietary starch level from 23% to 45%. This demonstrated the capacity of the broiler chicken to digest high levels of starch regardless of Eimeria spp. infection. Ileal energy digestibility was not affected by the treatments. 4. Weight gain did not differ between treatments; however, birds fed the LS diet were less efficient in feed conversion as compared to those fed the HS diet. 5. The use of isolated starch and the unintended higher extent of starch gelatinisation in the HS diet may have contributed to the higher starch digestibility in birds given the HS diet. Thus, the hypothesis that high ratios of starch to fat in pelleted diets may impair starch digestibility and production performance in Eimeria-challenged broiler chickens was not verified. Further work is required to clarify this research question, taking into consideration the physical form of starch source and the potentially confounding role of feed processing on starch availability.

Glucose and lipid metabolism of broiler chickens fed diets with graded levels of corn resistant starch

ABSTRACT 1. The aim of this study was to investigate the effects of graded levels of dietary corn resistant starch (RS) on glucose and lipid metabolism of broilers. 2. A total of 320 male broiler chicks (Arbor Acres, one-day-old) were randomly allocated to five dietary treatments, including a corn-soybean control diet, a corn-soybean based diet containing 20% corn starch, and three diets containing 4%, 8% and 12% RS by replacing corn starch with 6.67%, 13.33% and 20% Hi-Maize® 260 (identified as control, RS1, RS2, RS3 and RS4, respectively). Each treatment contained eight replicates with eight birds, and the experiment lasted 42 days. 3. Birds fed RS diets showed lower (P < 0.05) concentrations of serum low-density lipoprotein cholesterol and non-esterified fatty acid (NEFA) at d 21 and 42 of age, compared to the control. Lower (P < 0.05) hepatic apolipoprotein B concentration and citrate synthase (CS) activity, as well as a higher (P < 0.05) glycogen synthase (GS) concentration were observed in birds fed RS diets than those in the control group at d 21 of age. Consuming RS diets linearly increased (P < 0.01) serum glucose concentration, and linearly decreased (P < 0.01) NEFA concentrations in broilers at d 21 and 42 of age. Liver GS concentration and activities of hexokinase, pyruvate and CS were linearly increased (P < 0.01) in broilers at d 21 of age, but were linearly decreased (P < 0.05) in birds at d 42 of age in response to the increase of dietary RS levels. Feeding RS diets linearly decreased (P < 0.05) mRNA expressions of PC, PPARα and CPT-1 at d 21 of age and the mRNA expressions of SREBP-1 c, ChREBP, ACC and FAS at d 42 of age, and linearly increased (P < 0.05) the mRNA expressions of PEPCK, PC, LKB1, AMPKα1, PPARα, CPT-1 and L-FABP at d 42 of age. 4. Feeding broilers with diets containing higher concentration of RS promoted hepatic lipolysis and gluconeogenesis through activated AMPK signalling pathway and accelerated whole-body energy expenditures in the grower phase.

Effects of dietary starch and lipid levels on the protein retention and growth of largemouth bass (Micropterus salmoides).

Protein accretion in some fish species is affected by dietary lipids, starch and their interactions, but this aspect of nutrition is largely unknown in largemouth bass (LMB). Therefore, we designed six experimental diets with three starch levels (5%, 10%, and 15%; dry matter basis) and two lipid levels (10% and 12.5%; dry matter basis) to evaluate the effects of dietary starch and lipid levels on the protein retention, growth, feed utilization, and liver histology of LMB. There were three tanks (18 fish per tank, ~ 4.85g per fish) per dietary treatment group and the trial lasted for 8weeks. Fish were fed to apparent satiation twice daily. Results indicated that increasing the dietary starch level from 5 to 15% reduced (P < 0.05) absolute feed intake (AFI; -9.0%, -15% and -14% on days 14-28, 28-42, and 42-56, respectively) and weight gains (-4.4% and -6.5% on days 42 and 56, respectively) of LMB. Increasing the dietary lipid level from 10 to 12.5% reduced (P < 0.05) AFI (-9.7%, -11.7% and -11.9% on days 14-28, 28-42; and 42-56, respectively), weight gains (-4.2%, -5.9% and -6.9% on days 28, 42 and 56, respectively), and survival rate (by a 5.6% unit) of LMB. The retention of dietary protein and some amino acids in the body was affected by dietary starch or lipid levels and their interactions. The viscerosomatic index (VSI), hepatosomatic index (HSI), and intraperitoneal fat ratio (IPFR) increased with increasing the dietary starch level from 5 to 15%. Compared with 10% lipids, 12.5% lipids in diets increased IPFR but had no effect on VSI or HSI. The concentrations of glucose in serum increased with increasing the dietary starch level from 5 to 15% at 4 to 24h after feeding, with the effect of dietary lipids being time-dependent. Compared with a 5%-starch diet, fish fed a diet with 10%- or 15%-starch exhibited an enlarged and pale liver with excessive glycogen. Based on these findings, we recommend dietary lipid and starch levels to be 10% and < 10%, respectively, for juvenile LMB to maximize the retention of dietary protein in their bodies.

Starch in aquafeeds: the benefits of a high amylose to amylopectin ratio and resistant starch content in diets for the carnivorous fish, largemouth bass (Micropterus salmoides).

Aquafeeds for carnivorous species face a nutritional-technological conundrum: containing sufficient starch to meet specific manufacturing requirements for binding, extrusion and expansion, but ideally containing as little starch as possible owing to their limited ability to utilise carbohydrates. The present study evaluated the effects of dietary starch with different amylose to amylopectin ratios and resistant starch contents on growth performance, hepatic glycogen accumulation and glucose metabolism of an important cultured carnivorous finfish, largemouth bass (Micropterus salmoides). A common starch source (α-cassava starch (CS)) was tested as is or after being enzymatically de-branched at three different inclusion levels in diets for largemouth bass. Results showed that the increased dietary starch levels compromised performance and high dietary α-CS content led to obvious liver damage. However, the growth performances of fish fed the diets with de-branched starch (DS) were improved, and no manifest liver damages were observed even at the higher inclusion level. The increasing dietary starch contents significantly increased hepatic glycogen accumulation, but not when DS was used. High dietary starch content, without regard to starch sources, had no effect on the expression of glucose metabolism-related genes, except for down-regulation of insulin receptor expression. However, the use of dietary DS promoted the expression of genes involved in the insulin pathway and glycolysis. In conclusion, this study showed that the use of starch sources with a high amylose to amylopectin ratio and resistant starch in the feed for cultured carnivorous finfish could alleviate the hepatic glycogen deposition through regulating the insulin pathway and glycolysis.

Effects of graded levels of starch on the non-specific immune responses, antioxidant capacities and intestinal health in Chinese mitten crab, Eriocheir inensis

A 9-week feeding trial was conducted to investigate the effects of graded levels of dietary starch (12%, 17%, 22%, 27% and 32%) on growth, non-specific immune responses, antioxidant capacities, immunity genes expression levels and pathogen resistance in Chinese mitten crab, Eriocheir inensis (initial body weight: 10.5 ± 0.5 g). Results showed that the highest weight gain rate of crabs was obtained in group containing 22% dietary starch. The highest activity of acid phosphatase, phenoloxidase and lysozyme in blood was found in crabs fed with 22–27% dietary starch. Additionally, 17%–27% dietary starch significantly increased the activities of superoxide dismutase and glutathione peroxidase, reduced malondinaldehyde content and then increased the total antioxidant capacities in hepatopancreas of crabs. The highest activity of alanine aminotransferase and aspartate aminotransferase was found in crabs fed with 32% dietary starch, indicating that excess starch had a negative effect on the liver function of crabs. With the dietary starch level increased, the transcription factors gene expression of the pro-inflammatory factors were significantly up-regulated, and the highest ILF2, IL-16, Relish and ADAM10 was found in crabs fed with dietary 32% starch, which may potentially promote the inflammatory response in intestines. Moreover, with the dietary starch increased, the activity of phenoloxidase and lysozyme, as well as the gene expression of crustin, were all increased in crabs after challenge against Citrobacter freundii, which demonstrated that additional dietary starch could provide immune-protection and help crabs improve their resistance against pathogens. In conclusion, these results suggest that adequate dietary starch can increase growth, enhance innate immune responses and promote disease resistance, reduce oxidative stress and inflammatory response in E. inensis. Taken together, 22–27% dietary starch (25.9–30.8% dietary carbohydrate) was suggested as a digestible energy source in crabs feed.