Effects of dietary metabolizable energy and crude protein content on the activities of digestive enzymes in jejunal fluid of Peking ducks

Comparison of the characteristics of small intestinal fluid from white-feathered and yellow-feathered broilers

The objective of this study was to compare the properties of small intestinal fluid (SIF) from white- and yellow-feathered broilers fed variable dietary CP to test the hypothesis that digestive enzymes sourced from the SIF of yellow-feathered broilers could serve as a viable alternative for preparing in vitro SIF specifically for white-feathered broilers. Ten Arbor Acres Plus broilers (32 days of age) and 20 Chinese yellow chickens (51 days of age) were fitted with jejunal cannulas and assigned to dietary treatments as follows: 1) white-feathered broilers (BW of 4.08 ± 0.39 kg) fed diet 1 with CP of 19.88 %, 2) yellow-feathered broilers (BW of 2.89 ± 0.27 kg) fed diet 1, and 3) yellow-feathered broilers (BW of 2.84 ± 0.20 kg) fed diet 2 with CP of 16.32 %. Each treatment contained 10 replicates with 1 broiler in each replicate. Digestive enzyme activities, ion concentrations, pH, 16 amino acid (AA, excluding Tyr and Trp) contents, molecular weight distribution (MWD) of protein, hydrolysis rates on wheat starch, corn starch, casein, and soybean protein concentrate, and in vitro digestible energy of corn, soybean meal, and corn gluten meal were evaluated for SIF. Activities of chymotrypsin and amylase, pH, concentrations (mg/mL) of total amino acid (TAA) and 13 AA (excluding Pro, Cys, and Glu), and hydrolysis rates in casein or soybean protein concentrate were greater (P < 0.05), whereas MWD of protein from 19 to 23 kDa was lower (P < 0.05) in the SIF of yellow compared to white-feathered broilers fed diet 1. Furthermore, activities of chymotrypsin and amylase, concentrations of Na+, and Cl-, MWD of protein from 15 to 18 kDa were greater, while concentrations of K+ were lower in the SIF of yellow-feathered broilers fed diet 2 compared to white feathered broilers fed diet 1. Activities of chymotrypsin and amylase, K+ concentration, pH, TAA and 13 AA (excluding Pro, Cys, and Glu), hydrolysis rates in casein or soybean protein concentrate increased (P < 0.05), while concentrations of Na+ and Cl- (P < 0.05) decreased with dietary CP in SIF from yellow-feathered broilers. This experiment demonstrated diet composition and breed modulate digestive enzyme activities, ions (Na+, K+, Cl-), pH, and AA concentrations in the SIF. Our findings revealed no substantial difference in the hydrolytic characteristics of SIF from white-feathered broilers fed diet 1 and yellow-feathered broilers fed diet 2. Consequently, it is feasible to use digestive enzymes extracted from the SIF of yellow-feathered broilers to prepare simulated SIF for in vitro digestion of white-feathered broilers.

Refining dietary metabolisable energy and crude protein levels in relation to duck performance and behaviour

1. The study evaluated the effect of dietary metabolisable energy (ME) content and crude protein (CP) level on the growth performance and behaviour of ducks.2. A total of 720, Cherry Valley ducks were allocated to 36 pens in groups of 20 birds. For the initial period, from 1 to 21 d age, six diets, containing a standard (SME), low (LME) and high (HME) ME of 12.14, 11.93 and 12.35 MJ/kg, and standard (SCP) or high (HCP) CP contents of 210 or 220 g/kg diet, respectively, were mixed. For the period from 22 to 42 d age, the diets contained ME of 12.98 (SME), 12.77 (LME), 13.19 (HME) MJ/kg and the levels of CP were 170 (SCP) or 180 (HCP) g/kg, respectively.3. An ME by CP interaction was seen from 1 to 21 d age in ducks fed HME + HCP diet, which had greater weight gain than those fed LME + SCP (P < 0.05). Compared to LME + SCP, dietary HME decrease feeding but increased walking behaviour compared to LME + SCP and SME + SCP (P < 0.05). High CP in LME and SME diets increased drinking behaviour (P < 0.05), but there was no change in HME diet. Compared to LME, feeding HME reduced ground pecking (P < 0.05). Feeding HME reduced feeding behaviour (P < 0.05) from 22 to 42 d age. During the same period, standing behaviour was reduced in HCP + LME (P < 0.05). Drinking was reduced in LME + SCP compared to SME + HCP and HME + HCP (P < 0.05).4. A diet formulated with HME and HCP is effective for enhancing growth performance of ducks aged 1-21 d and saving time for feeding or ground pecking, which may induce spending more time on other activities.

Improvement in growth performance and digestive function from amniotic injections of N-acetylglutamate in broiler chickens

BACKGROUND

N-acetylglutamate (NAG) is the initial and essectial substrate in the process of de novo arginine synthesis, plays an important role in intestinal development. The aim of this study was to determine the effects of in ovo feeding of NAG, 1.5 mg/egg at 17.5 days of incubation (DOI) via amnion, on hatching performance, early intestinal histomorphometry, jejunal barrier, digestive function, and growth performance of broiler chickens between 1 and 14 days of age.

RESULTS

Amniotic injection of NAG had no significant effect on hatching characteristics compared with the non-injected control group (NC group). Birds in the NAG solution-injected group (NAG group) exhibited lower average daily feed intake and better feed efficiency during a period of 1-14 days. In comparison with the NC group, the NAG group had decreased crypt depth (CD) in the ileum and increased villus height (VH) / CD in the jejunum at 7 days, and decreased CD in duodenum and significantly increased VH in the jejunum at 14 days. However, the effects of in ovo supplementation with NAG on the density of goblet cells, and gene expression of mucin 2 and alkaline phosphatase were not significant. Chicks in the NAG group had a significantly higher mRNA expression level of trypsin and maltase in jejunum at 7 days than the NC group but not at 14 days.

CONCLUSION

Amniotic injections of NAG (1.5 mg/egg) at 17.5 DOI could improve early growth performance of broilers during 1-14 days after hatching by accelerating the development of the intestine and enhancing jejunal digestive function. © 2023 Society of Chemical Industry.

Research Note: The comparative study of energy utilization in feedstuffs for Muscovy ducks between in vivo and in vitro

Our study was aimed to investigate the effects of dietary metabolizable energy (ME) and crude protein (CP) levels on the digestive physiology in the jejunal fluid of Muscovy ducks to provide digestive parameters for in vitro digestion. There were 6 ME levels (11.0, 11.5, 12.0, 12.5, 13.0, and 13.5 MJ/kg; Exp. 1) and six CP levels (140, 155, 170, 185, 200, and 215 g/kg; Exp. 2) and each treatment included 6 replicates with 3 ducks each replicate. In Exp. 3, the comparison of energy utilization was investigated between in vivo and in vitro using the digestion parameters obtained from Exp. 1 and 2. As dietary ME was increased, the chymotrypsin activity was increased linearly (P < 0.05), and the concentrations of Ca²⁺, K⁺, and Mg²⁺ were increased quadratically (P < 0.05) in the jejunal fluid. As dietary CP was increased, amylase activity was increased linearly (P < 0.05), whereas trypsin and chymotrypsin activities and Ca²⁺ concentration were increased quadratically (P < 0.05). The pH values were decreased quadratically with the increased dietary ME or CP levels (P < 0.05). The optimal digestion parameters for energy feedstuffs with 307.26 U/mL amylase, 54.68 U/mL trypsin, 24.90 U/mL chymotrypsin, 104.39 mmol/L Na⁺, 51.25 mmol/L Cl^-, and pH 7.79; for protein feedstuffs with 381.88 U/mL amylase, 72.84 U/mL trypsin, 11.98 U/mL chymotrypsin, 93.53 mmol/L Na⁺, 46.25 mmol/L Cl^-, and pH 7.80, respectively. Using the optimal digestion parameters for in vitro digestion, energy utilization in vitro reflected the degree of the apparent energy utilization of corn, sorghum, and barley as well as true energy utilization of soybean meal, rapeseed meal, and cottonseed meal in vivo and the variation of digestion was lower in vitro than in vivo.

Effects of graded levels of microbial fermented or enzymatically treated dried brewer's grains on growth, digestive and nutrient transporter genes expression and cost effectiveness in broiler chickens

BACKGROUND

Poultry feed consists mainly of conventional grains and protein supplements, however, using treated unconventional agro-industrial by-products as replacements of corn soybean-based diet can minimize production costs and improve productivity. Therefore, in this study, the effects of fermented or enzymatically treated dried brewer grains (DBG) on growth, expression of digestive enzymes and nutrient transporters genes and the profitability of the rations were evaluated. A total of 1600 one-day-old Ross 308 broiler chicks were randomly distributed in 2 × 4 factorial arrangement (eight treatments with ten replicates, 20 birds/replicate). Experimental diets included two controls; negative control (basal corn-soybean diet; NC) and positive control (basal corn-soybean diet with exogenous enzymes; PC), and six diets in which basal diet was replaced by three levels of fermented DBG (FDBG; 5, 10 or 15%), or enzyme-treated DBG (DBG 5, 10 or 15%+Enz), for 38 days.

RESULTS

The results described that feeding FDBG (three levels) or DBG5%+Enz improved (P < 0.05) BW gain and feed efficiency of broilers. Also, feeding FDBG10% yielded the best improvement in weight gain (10%), compared to NC group. Increasing the inclusion levels of DBG either fermented or enzymatically treated up-regulated (p < 0.01) expression of digestive-genes in proventriculus (PGC and PGA5, range 1.4-1.8 fold), pancreas (AMY2A, PNLIP, CELA1, and CCK; range 1.2-2.3 fold) and duodenum (CAT1, CAT2, GLUT1, GLUT2, LAT1, Pep1; range 1.3-3 fold) when compared to NC group. Feeding treated DBG significantly increased (p < 0.05, range 4.5-13.6%) gizzard relative weight compared to NC and PC groups. An additional benefit was lower (p < 0.01) cholesterol content from 66.9 mg/100 mg (NC) to 62.8 mg/100 mg (FDBG5 or 10%) in thigh meat. Furthermore, the least cost feed/kg body gain was achieved in FDBG10% and DBG5%+Enz groups, with approx. 16% reduction compared to NC cost, leading to increasing the income gross margin by 47% and 40% in FDBG10% and DBG5%+Enz groups, respectively.

CONCLUSIONS

Substitution of corn-soybean based diet with 10% FDBG or 5% DBG+Enz resulted in better growth and higher economic efficiency of broilers chickens.

Effects of dietary crude protein level and N-carbamylglutamate supplementation on nutrient digestibility and digestive enzyme activity of jejunum in growing pigs

Three experiments were conducted to investigate the effects of dietary crude protein (CP) level and N-carbamylglutamate (NCG) supplementation on apparent total tract digestibility (ATTD) and ileal digestibility of nutrients and digestive enzyme activity of jejunum in growing pigs. In experiment 1, 10 Duroc × Landrace × Yorkshire barrows (initial BW: 48.7 kg) were allotted to a three-period switchback design with five experimental diets and two replicate pigs per diet in each period. Diets were categorized as high CP (HP, 18% CP), moderate low CP (MLP, 15% CP), very low CP (VLP, 12% CP), and MLP and VLP with 0.1% NCG supplementation. Feces and urine were collected from day 6 to day 11 after a 5-d adaptation period. The DE, ME, and ATTD of GE, OM, CP, NDF, ADF, and P decreased (P < 0.01) with a reduction of dietary CP, but no effect of dietary treatments on pig daily N retention was detected. The NCG supplementation increased (P < 0.01) DE and ATTD of ADF of the VLP diet. In experiment 2, 10 jejunal-cannulated Duroc × Landrace × Yorkshire barrows (initial BW: 44.5 kg) were fed five diets for three periods as experiment 1. Jejunal fluid was collected on days 6 and 8 after a 5-d adaptation period. The digestive enzymes activity was not affected by dietary CP level, except for α-amylase, for which there was a decrease (P < 0.01) in pigs fed VLP diets compared to HP and MLP diets. In experiment 3, 12 ileal-cannulated Duroc × Landrace × Yorkshire barrows (initial BW: 46.7 kg) were allotted to a three-period switchback design with six diets and two replicate pigs per diet in each period. The six experimental diets consisted of five experimental diets as experiment 1 and one N-free diet. Ileal digesta was collected from day 6 to day 8 after a 5-d adaptation period. Results indicated that apparent ileal digestibility (AID) of CP and P and ileal digestibility of Arg, His, Ile, Leu, Phe, and all dispensable AA, except Pro, decreased (P < 0.01) in pigs fed VLP diet compared to HP and MLP diets, but AID of GE, OM, EE, NDF, and ADF were not affected. The supplementation of NCG in the VLP diet increased (P < 0.01) the AID of CP and ileal digestibility of Arg, His, Leu, Phe, Val, Ser, and Tyr. In conclusion, reducing dietary CP level decreased nutrient digestibility, but improved the efficiency of dietary N utilization and reduced N emission. Moderate reduction of dietary CP level had a minimal effect on nutrient digestibility and digestive enzyme activity. Additionally, NCG supplementation plays a beneficial effect on nutrient digestion only if the dietary CP level is extremely lowered.

Effect of Corn Particle Size on the Particle Size of Intestinal Digesta or Feces and Nutrient Digestibility of Corn–Soybean Meal Diets for Growing Pigs

This study was conducted to evaluate the effect of corn particle size on the particle size of intestinal digesta or feces and nutrient digestibility of corn–soybean meal diets. Twenty-four growing barrows (initial BW: 21.9 ± 1.62 kg) were randomly divided into 4 groups of 6 pigs. A T-cannula was surgically placed in the anterior duodenum (about 50 cm from pylorus) of pigs in Groups 1 and 2 or in the distal ileum of pigs in Groups 3 and 4. Corn used to formulate diets had mean particle size (MPS) of 365 µm (Corn 1) or 682 µm (Corn 2), resulting in diets with MPS of 390 µm (Diet 1) or 511 μm (Diet 2). Diet 1 or 2 were randomly assigned within pig Groups 1 or 2 and 3 or 4. The digestive enzyme activities of duodenal fluid, particle size of intestinal digesta and feces, as well as nutrient digestibility, were determined for each pig as the experiment unit. The MPS of duodenal digesta (181 vs. 287 µm, p < 0.01), ileal digesta (253 vs. 331 µm, p < 0.01), and feces (195 vs. 293 µm, p < 0.01) was significantly reduced for pigs fed Diet 1 vs. Diet 2, respectively. Compared with Diet 2, Diet 1 significantly reduced the proportion of particles above 0.5 mm, but significantly increased the proportion of particles between 0.072 and 0.5 mm (p < 0.01) in digesta and feces (p < 0.01). Diet 1 significantly increased solubles percentage (<0.072 mm) in duodenal digesta (p < 0.05) but did not affect solubles percentage in ileal digesta and feces. The MPS of diet did not affect the activities of amylase, trypsin, and chymotrypsin in the duodenal fluid and the apparent total tract digestibility (ATTD) of dry matter, gross energy, crude protein, ether extract, neutral detergent fiber (NDF) and acid detergent fiber (ADF) in pigs offered Diet 1 compared to Diet 2. The in vitro digestible energy (IVDE) (3706 vs. 3641 kcal/kg; p = 0.03) was greater for Corn 1 vs. Corn 2. However, no significant difference was observed in IVDE (3574 vs. 3561 kcal/kg; p = 0.47) for Diet 1 vs. Diet 2. In conclusion, the particle size of digesta and feces was dependent on the dietary particle size. However, the digestive enzyme activities of duodenal fluid and ATTD of energy and nutrients were not affected by reducing dietary MPS from 511 to 390 µm.

Effects of dietary energy and protein content and lipid source on growth performance and carcass traits in Pekin ducks

The present study was conducted to determine the impact of dietary energy and protein concentrations and lipid sources on growth performance and carcass traits of Pekin ducks. In Exp. 1, 15-day-old ducks (6 replicate pens, 60 ducks/pen) were randomly assigned to 4 dietary treatments with different metabolizable energy (ME) and crude protein (CP) concentrations (2,850 kcal/kg and 16%, 2,950 kcal/kg and 16.5%, 3,050 kcal/kg and 17.0%, and 3,150 kcal/kg and 17.5%) based on body weight (BW). In Exp. 2, 20-day-old ducks (4 replicate pens, 60 ducks/pen) were randomly allotted to 3 dietary fat sources (soybean oil, lard, and palm oil) with or without emulsifier in a 3 × 2 factorial arrangement. In Exp. 1, increasing ME and CP level improved (P < 0.05) body weight gain (BWG) and cost-to-gain ratio linearly, but reduced (P < 0.05) feed intake (FI) and feed-to-gain ratio (F/G) linearly. Breast skin thickness and liver redness (a*) value increased (P < 0.05) linearly with the increasing ME and CP level. In Exp. 2, no interactions between fat sources and emulsifier were observed. Feeding lard and palm oil diets increased (P < 0.05) final BW and BWG compared to soybean oil. Birds fed soybean oil and palm oil diets had lower (P < 0.05) FI compared to those fed lard diet. F/G in soybean oil and lard groups was higher (P < 0.05) compared to palm oil group. Birds in palm oil and lard groups had higher (P < 0.05) European production efficiency factor than those in soybean oil group. The addition of emulsifier increased (P < 0.05) BWG. In summary, the optimal ME and CP level for roasting was 2,950 kcal/kg ME and 16.5% CP and the palm oil was better than soybean oil and lard in Pekin ducks from 15 to 40 D of age.

Validation of in vitro digestion using simulated small intestinal fluid with specific digestive activity to predict the metabolizable energy of feed ingredients for duck

Two experiments were conducted to validate a method to prepare simulated small intestinal fluid (SSIF) for in vitro digestion in ducks. Experiment 1 compared the in vitro digestible energy (IVDE) of SSIF to endogenous small intestinal fluid (ESIF) on four feeds. The ESIF 1 or 2 obtained from two groups of jejunal cannulated ducks offered diet 1 (3,050 kcal/kg of ME and 19.95% of CP) or 2 (2,801 kcal/kg of ME and 14.90% of CP) was purified into raw enzyme power (REP) 1 or 2. SSIF 1 to 3 or 4 to 6 were prepared to mimic ESIF 1 or 2, respectively. The enzyme sources were REP 1 for SSIF 1 and 4, REP 2 for SSIF 2 and 5 or reagent enzymes for SSIF 3 and 6, respectively. The IVDE of each feed was determined with SSIF or ESIF. Experiment 2 was to validate whether REP 1 was more effective than only reagent enzymes to prepare SSIF. Ten feeds were determined with pepsin following SSIF 1 or 3 for IVDE 1 or 2, respectively. The accuracy of prediction model of true metabolizable energy (TME) from IVDE 1 or 2 was evaluated to validate the efficacy of SSIF. In experiment 1, higher activities of amylase, trypsin and chymotrypsin were observed in ESIF 1 than ESIF 2 (P < 0.05). The IVDE determined with SSIF 1 and 2 or 3 and 4 were more comparable to that of ESIF 1 or 2 than determinations with SSIF 3 or 6. In experiment 2, the mean IVDE 1 or 2 was 97.22% or 96.23% relative to TME, respectively, and both were highly correlated with TME (P < 0.01; R2 ≥ 0.98). However, the residual SD of TME prediction model with IVDE 1 was less than that generated with IVDE 2 (55 vs. 71 kcal/kg). In conclusion, the IVDE determined with in vitro digestion of pepsin following SSIF prepared with REP can predict accurately TME of feed for ducks.

Nutrient density of prestarter diets from 1 to 10 days of age affects intestinal morphometry, enzyme activity, serum indices and performance of broiler chickens

A total of 480 day-old Cobb 500 broilers were used to investigate the effects of different levels of digestible amino acids (DAA; 100%, 107% and 114% of Cobb recommendations) and ME (3,000 or 2,900 kcal/kg) of prestarter diet on mixed sex broilers performance, enzyme activity, small intestine morphology, and serum metabolites. Broilers were randomly allotted to 6 treatments, where each treatment applied to 4 pens with 20 birds in each. The birds were subjected to their respective treatment diets from 1 to 10 days of age. This was followed by feeding common starter and finisher diets for the last 29 days. The enzyme activity of the pancreas was measured at 10 days of age. Morphometric indexes of jejunum were measured at 10 days of age and the end of the feeding period. Our results showed that the body weight (BW) increased as the DAA density of the prestarter diet increased from 100% to 114% over the first 10 days and the entire period of the study. Birds fed 114% DAA presented a better feed conversion ratio on day 10 (P < 0.05). At day 39, carcass weight and breast yield increased as the DAA levels increased from 100% to 114% (P < 0.05). The whole intestine length, small intestine length, and weights of the pancreas were lower in birds fed 100% DAA-diets at 10 days of age (P < 0.05). Increasing the dietary DAA and ME did not affect serum amylase, lipase, and protease concentrations and pancreatic amylase and lipase activity (P > 0.05); however, the activity of pancreatic protease increased as the DAA level increased from 100% to 114% (P < 0.05). The villus width and villus surface area (VSA) increased as the DAA level increased from 100% to 114% on day 10 (P < 0.05). At 10 days of age, crypt depth was the lowest in the birds fed plenty DAA prestarter diets (P < 0.05). It was found that dietary treatments at 39 days of age did not affect intestinal morphology. The results of the present work indicate that DAA level of 114% of Cobb recommendations and energy level of 2,900 kcal/kg diet may be recommended for starting broiler chicks.

Effect of dietary threonine on laying performance and intestinal immunity of laying hens fed low-crude-protein diets during the peak production period

Threonine (Thr) may be a limiting amino acid for laying hens fed diets with lowered protein level. An experiment was conducted to examine laying performance, and the intestinal immune function of laying hens provided diets varying in digestible Thr levels. Lohmann Brown laying hens (n = 480), 28 weeks of age, were allocated to six dietary treatments, each of which included five replicates of 16 hens. Dietary crude protein (CP) 16.18% diet was offered as the positive control diet. L-Thr was added to the negative diet (14.16% CP) by 0, 1.0, 2.0, 3.0 and 4.0 g/kg, corresponding 0.44%, 0.43%, 0.49%, 0.57%, 0.66% and 0.74% digestible Thr. At 40 weeks, a reduction in CP level decreased laying performance (p < 0.05). In the low CP, increasing dietary Thr increased (p < 0.05) egg production and egg mass and rose to a plateau between 0.57% and 0.66%. The hens fed 0.66% Thr showed the lowest value (p < 0.05) of feed conversion ratio (FCR). Serum level of uric acid showed the lowest values (p < 0.05) at 0.57-0.66%. In addition, serum-free Thr maximized (p < 0.05) between 0.66% and 0.74%. Digestive trypsin activity decreased (p < 0.05) when hens fed the low-CP diet compared with hens fed CP (16.18%) and hens fed 0.57-0.66%. Expressions of ileal MUC2 mRNA maximized (p < 0.05) at 0.66% Thr. Occludin mRNA increased with increasing Thr level (p < 0.05). sIgA mRNA reached to the maximum level (p < 0.05) at 0.66% and 0.74% Thr. INF-γ mRNA reached to the lowest level (p < 0.05) at 0.65%. Expressions of ileal IL-2, IL-6, IL-1β mRNA decreased with increasing Thr level (p < 0.05). In conclusion, Thr supplementation resulting in optimal laying performance and stimulated the mucosal immune system, suggesting that it is a limiting amino acid in the low-crude-protein diet of laying hens during the peak production period.

Effects of dietary protein and energy levels on digestive enzyme activities and electrolyte composition in the small intestinal fluid of geese

The present study was conducted to evaluate the effects of dietary protein and energy levels on digestive enzymes and electrolyte composition in jejunum of geese. A 3×3 factorial and completely randomized design was adopted with three protein levels and three energy levels. The experiment included four replicates for each treatment, and three geese for each replicate. Isovolumetric supernate from centrifugal jejuna fluid were mixed in each replicate. Activities of digestive enzymes and ions were analyzed. The results showed trypsin and chymotrypsin activities were significantly increased with increasing of dietary protein and energy levels (P<0.05). The concentrations of Ca²⁺ and pH value were significantly decreased by increased dietary protein and energy levels. However, no significant differences were found for the activities of amylase and cellulase, as well as the concentration of Na⁺ among groups with different protein and energy levels. In conclusion, digesta enzymes and electrolytes in the small intestine adapted to the protein and energy levels. The activities of protease, rather than amylase and cellulase were induced with increasing of protein and energy levels. The imbalance of positive and negative ions was possibly adjusted by the fluctuant concentrations of K⁺ , Cl^- and Ca²⁺ for maintaining normal physiological function.

Effect of age and diet composition on activity of pancreatic enzymes in birds

Digestive enzymes produced by the pancreas and intestinal epithelium cooperate closely during food hydrolysis. Therefore, activities of pancreatic and intestinal enzymes processing the same substrate can be hypothesized to change together in unison, as well as to be adjusted to the concentration of their substrate in the diet. However, our knowledge of ontogenetic and diet-related changes in the digestive enzymes of birds is limited mainly to intestinal enzymes; it is largely unknown whether they are accompanied by changes in activities of enzymes produced by the pancreas. Here, we analyzed age- and diet-related changes in activities of pancreatic enzymes in five passerine and galloanserine species, and compared them with simultaneous changes in activities of intestinal enzymes. Mass-specific activity of pancreatic amylase increased with age in young house sparrows but not in zebra finches, in agreement with changes in typical dietary starch content and activity of intestinal maltase. However, we found little evidence for the presence of adaptive, diet-related modulation of pancreatic enzymes in both passerine and galloanserine species, even though in several cases the same birds adaptively modulated activities of their intestinal enzymes. In general, diet-related changes in mass-specific activities of pancreatic and intestinal enzymes were not correlated. We conclude that activity of pancreatic enzymes in birds is under strong genetic control, which enables evolutionary adjustment to typical diet composition but is less adept for short term, diet-related flexibility.

Effects of dietary protein source on the digestive enzyme activities and electrolyte composition in the small intestinal fluid of chickens

An experiment was conducted to investigate the effects of dietary protein source on the digestive enzymes and electrolyte composition of digesta fluid in the duodenum, jejunum, and ileum of chickens. A 2 × 3 factorial and completely randomized design that used 2 types of diets that differed only in their protein source [a corn-soybean meal-miscellaneous meal diet (CSMD) and a corn-miscellaneous meal diet (CMD)] and 3 types of cannulated roosters (duodenal, jejunal, and ileal cannulations) was adopted. The experiments included 5 replicates for each of the 6 treatments, and each replicate involved 3 cannulated chickens. The digesta samples were collected for 1 h every 4 h between 09:30 and 18:30 h on d 31, 33, and 35 of the experiment. The amylase, lipase, trypsin, and chymotrypsin activities and the electrolyte composition in the duodenal, jejunal, and ileal fluid were determined. In general, no significant differences between the 2 dietary groups were observed for the mean of duodenal, jejuna, and ileal amylase, trypsin, chymotrypsin, and lipase, respectively. However, the duodenal amylase activity was lower in the CMD group than the CSMD group (P < 0.05), which was probably related to the lower duodenal pH value that was observed in this group (P < 0.01). A higher jejunal Mg(2+) concentration was observed in chickens that were fed the CMD (P < 0.05), whereas the differences in the Na(+), K(+), Cl(-), and Ca(2+) concentrations in the small intestine were not significant between the 2 diets (P > 0.05). In conclusion, the digestive enzymes and electrolytes in the small intestinal fluid of chickens adapted to the protein source of the diet, and each segment of the small intestine displayed different modifications.