Dietary Crude Protein Levels Research Articles

Effects of dietary crude protein level and sodium butyrate protected by medium-chain fatty acid salts on performance and gut health in weaned piglets.

To reduce the use of antibiotics, research into nutritional strategies designed to improve the gut health of weaned pigs is underway. This study sought to examine the effects of reducing dietary crude protein (CP) and/or supplementing the feed with sodium butyrate protected by the sodium salts of medium-chain fatty acids on the growth performance and gut health of weaned piglets. Ninety-six weaned piglets (Landrace × large white, 21 days of age) were allotted to four experimental treatments for 14 d. The experimental design was factorial with 2 CP levels and 2 feed-additive doses (0 vs. 1 kg/t). Results showed that reducing CP from 22.2% to 18.8% diet had no effect on piglet growth performance parameters during the first post-weaning week (P > 0.05), but did compromise growth in the second week (P = 0.011), impacting overall growth performance results (P = 0.019). Nonetheless, dietary CP level reduction led reducing crypt depth (P = 0.03657). In addition, Lactobacillus counts that were increased in the ileum (P = 0.032) and reduced in the colon (P = 0.032). Furthermore, apparent ileal digestibility of organic matter (P = 0.026) and fecal consistency (P < 0.05) were improved throughout the experiment. Moreover, in piglets fed diets containing 22.2% CP, the use of the feed-additive tended to improve the gain-to-feed ratio (P = 0.091) compared to those fed supplemented diets containing 18.8% CP. In addition, feed supplementation increased ileal numbers of goblet cells (P = 0.036), as well as apparent ileal digestibility of dry matter (P = 0.057) and organic matter (P = 0.003). Supplementation also had beneficial effects on the microbiota of the colon, increasing Lactobacillus counts (P = 0.006) and diminishing Enterobacteriaceae counts (P = 0.003), as well as affecting microbial metabolite profiles in that acetic acid concentrations tended to be increased (P = 0.088) and valeric acid concentrations were reduced (P = 0.002). These findings support the use of both strategies can improve the gut health of weaned piglets and prompt further research into the possible benefits of combining these two nutritional strategies on gut health and growth performance.

Effects of Dietary Crude Protein and Protease Levels on Performance, Immunity Capacity, and AA Digestibility of Broilers

Exogenous proteases are promising to stimulate the application of low-protein diets for broilers. A total of 540 1-day-old Arbor Acres male broilers were randomly assigned to 9 groups with 6 replicates of 10 birds. A 3 × 3 factorial, completely randomized arrangement was used to evaluate the effects of dietary crude protein (CP) and protease levels on growth and slaughter performance, immunity capacity, and apparent ileal digestibility (AID) of amino acids (AA). Dietary CP levels were 20.0%, 19.5%, or 19.0% during the starter phase, and 18.0%, 17.5%, or 17.0% during the finisher phase. Protease levels were 0, 250, or 500 mg/kg in diets throughout the trial. The trial lasted for 42 days. Weight gain and feed efficiency of broilers decreased as dietary CP lowered, but improved with protease supplementation. Dietary CP and protease levels had few effects and interactions on carcass characteristics, immune organ indexes, and immunoglobulin concentrations. The AID of most AA was improved by dietary CP decrease or protease supplementation. In conclusion, reducing dietary CP decreased the performance and immune capacity of broilers but increased the AID of AA. Almost independent of dietary CP level, dietary protease addition improved the performance of broilers, probably through the enhancement of AA digestibility, and had no effect on carcass traits.

Exploring the growing forest musk deer (Moschus berezovskii) dietary protein requirement based on gut microbiome.

It is necessary to assess the appropriate dietary protein level of the forest musk deer (FMD), as nutritional needs are unclear. The microbiome in gastrointestinal tracts plays an important role in regulating nutrient utilization, absorption and host growth or development. Thus, we aimed to evaluate growth performance, nutrient digestibility and fecal microbiome of growing FMD supplied with different protein levels of diets. Eighteen 6-month-old male FMD with an initial weight 5.0 ± 0.2 kg were used in a 62-day trial. The animals were randomly distributed to three groups, the dietary crude protein (CP) level was 11.51% (L), 13.37% (M), and 15.48% (H). The results showed that the CP digestibility decreased as dietary CP level increased (p < 0.01). Compared with group L and H, FMD in M group has higher average daily gain, feed efficiency and neutral detergent fiber digestibility. For the fecal bacterial community, the percentage of Firmicutes was increased, Bacteroidetes was decreased and the diversity of microbiota significantly reduced (p < 0.05) with the increasing of dietary protein. The proportion of Ruminococcaceae_005, Ruminococcaceae_UCG-014 and uncultured_bacterium_f_Lachnospiraceae were significantly increased wtih rising CP, the proportions of Bacteroides and Rikenellaceae_RC9_gut_group were significantly decrease nevertheless at the genus level. The higher abundance of f_Prevotellaceae and g_Prevotellaceae_UCG_004 were found at M group by LEfSe analysis. The relative abundance of uncultured_bacterium_f_Ruminococcaceae was positively correlated with the average daily gain and feed conversion ratio (p < 0.05), whereas Family_XIII_AD3011_group was negatively correlated with feed conversion ratio (p < 0.05). The UPGMA tree showed L and M groups were closer in clustering relationship, while H group was clustered separately into a branch, which indicated that the bacterial structure had changed greatly with protein level increased from 13.37 to 15.48%. Overall, our results indicated that the optimum dietary CP for the growing FMD was 13.37%.

Effects of different levels of dietary crude protein on growth performance, blood profiles, diarrhea incidence, nutrient digestibility, and odor emission in weaning pigs.

This experiment was conducted to evaluate the effects of different levels of dietary crude protein (CP) on growth performance, blood profiles, diarrhea incidence, nutrient digestibility, and odor emission in weaning pigs. A total of 240 weaning ([Yorkshire×Landrace]×Duroc) pigs (8.25±0.050 kg body weight [BW]) were assigned to six treatments based on sex and initial BW, with five replicates of eight pigs per pen in a randomized complete block design. Experimental diets with different crude protein levels for early and late weaning phases were as follows: i) CP16, corn‒soybean-based diet containing 16%/15% CP; ii) CP17, corn‒soybean-based diet containing 17%/16% CP; iii) CP18, corn‒soybean-based diet containing 18%/17% CP; iv) CP19, corn‒soybean-based diet containing 19%/18% CP; v) CP20, corn‒soybean-based diet containing 20%/19% CP; and vi) CP21, corn‒soybean-based diet containing 21%/20% CP. In the early weaning period, average daily feed intake increased when the dietary CP level decreased (linear, p<0.05). During the entire experimental period, average daily gain and the gain to feed ratio decreased when the dietary CP level increased (linear, p< 0.01). Additionally, a decrease in dietary CP level resulted in a linear increase in final BW (linear, p<0.05). In the early and late weaning periods, blood urea nitrogen (BUN) decreased when the dietary CP level decreased (linear, p<0.01). There were no significant differences in creatinine, glucose, total protein, triglyceride or insulin-like factor-1 levels over the experimental period. The concentrations of immunoglobulin A (IgA) and IgG were not significantly affected by dietary CP levels during the experimental period. In the early weaning period, fecal and urine N decreased when the dietary CP level decreased (linear, p<0.01). No differences in nutrient digestibility among the treatments during the early weaning period were found. Throughout the whole experimental period, when the dietary CP level decreased in the weaning pig diet, the diarrhea incidence decreased linearly (linear, p<0.01). Throughout the whole experimental period, when the dietary CP level decreased in the weaning pig diet, ammonia, amines and hydrogen sulfide decreased linearly (linear, p<0.01). Reducing dietary CP could decrease diarrhea incidence, the concentration of BUN in serum and odor emission in manure. Furthermore, it could improve N excretion in feces and urine and growth performance in weaning pigs.

Dietary Protein Requirement of Juvenile Dotted Gizzard Shad Konosirus punctatus Based on the Variation of Fish Meal.

An 8-week feeding trial was conducted to investigate the effects of dietary protein levels on growth performance, feed utilization, and energy retention of juvenile dotted gizzard shad Konosirus punctatus based on the variation of fish meal. Fish meal was used as the sole protein source; five semi-purified diets were formulated with varying crude protein (CP) levels of 22.52%, 28.69%, 34.85%, 38.84%, 45.78% (CP1-CP5 diets). A total of 300 uniform juveniles with initial body weight 3.61 ± 0.20 g fish-1 were randomly divided into five groups with three replicates in each group. The results showed that different CP levels did not significantly affect the survival of juvenile K. punctatus (p > 0.05). The values of weight gain (WG) and specific growth ratio (SGR) showed a general enhancing trend and then weakened with increasing dietary CP levels (p > 0.05). Feed utilization also improved with increasing dietary CP levels (p > 0.05), and the optimal feed conversion ratio (FCR) value was found in fish fed the diet with CP3 (p > 0.05). The rise of dietary CP from 22.52% to 45.78% enhanced the daily feed intake (DFI) and protein efficiency ratio (PER) values of K. punctatus (p < 0.05). With the increase of dietary CP levels, daily nitrogen intake (DNI), energy retention (ER), and lipid retention (LR) elevated, while retention (NR), daily energy intake (DEI), and daily lipid intake (DLI) reduced (p < 0.05). No statistical differences in the content of water, crude protein, and crude lipid were observed among different treatments (p > 0.05). The activity of lipase in CP3 and CP4 diets was significantly higher than that of the CP1 diet (p < 0.05). Fish fed CP2 and CP3 diets had significantly higher amylase activity than that of the CP5 diet (p < 0.05). The levels of alanine aminotransferase (GPT) first enhanced and then decreased as dietary CP levels raised. The second-order polynomial regression model analysis of the WG and FCR indicated that the optimal dietary protein level for K. punctatus is about 31.75-33.82% based on the variation of fish meal.

Dietary Crude Protein Changes Rapidly Alter Metabolism and Plasma Insulin-Like Growth Factor I Concentrations in Broiler Chickens

Although changes in dietary crude protein levels change metabolism in broiler chickens, there is little information concerning the time course of the process of adaptation. Therefore, male Indian River broiler chickens were fed diets containing either 120 or 210 g protein/kg from 7 to 28 d of age and then were fed the other level for an additional 12 d. Birds were bled and killed at 0, 2, 5, 7, 9 and 12 d following the reversals. Measurements taken at these intervals included in vitro lipogenesis, growth and feed consumption, hepatic enzyme activities and plasma metabolites and metabolites. Birds fed the lower level of crude protein were smaller and less efficient in growth from 7 to 28 d. Feeding these birds a higher protein diet from 28 to 40 d improved both growth and feed efficiency. Lipogenesis was also greater and plasma insulin-like growth factor-I (IGF-I) less in birds fed the lower protein diet. Switching dietary treatments increased and decreased lipogenesis as birds were switched from high to low protein and from low to high protein diets, respectively. Half-maximal changes were observed 4 d after the reversal and maximal changes 7 d after the reversal. In contrast, switching dietary treatments decreased and increased plasma IGF-I as birds were switched from high to low protein and from low to high protein diets, respectively. Half-maximal changes were observed 2 d after the reversal. Of the three hepatic enzymes monitored, malic enzyme activity most closely followed the rapid changes in in vitro lipogenesis. Plasma IGF-I may be a more sensitive indicator of changes in dietary protein than changes in intermediary metabolism.

Impacts of Dietary Lysine and Crude Protein on Performance, Hepatic and Renal Functions, Biochemical Parameters, and Histomorphology of Small Intestine, Liver, and Kidney in Broiler Chickens

The present study aimed to investigate the effects of increasing dietary lysine (Lys) levels with an adequate dietary crude protein (CP) content, as well as the effects of a reduction in dietary CP content with the recommended amino acid (AAs) level, on the performance, blood biochemical parameters, and histomorphology of the duodenum, liver, and kidney in broiler chickens. A total of 500 broiler chickens were randomly distributed into five dietary treatment groups, following a completely randomized design, where, at the beginning, the control group (C) was fed a diet containing the standard CP and Lys levels: 23% CP with 1.44% Lys during the starter period; 21.5% CP with 1.29% Lys during the growing period; and 19.5% CP with 1.16% Lys during the finishing period. The Lys content was increased by 10% above the recommended control basal requirements in the second group (Gr1) and by 20% in the third group (Gr2), while using the same recommended CP percentage as the C group. The fourth group (Gr3) had a 1% lower CP content and the fifth group had a 2% lower CP content than the C group, with the same recommended AA level as the C group. Increasing the Lys content in the Gr1 group improved the broilers' weight gains (p < 0.05) during the starter, growing, and finishing periods. Decreasing dietary CP with the standard AA levels (Gr3 and Gr4) did not significantly affect (p > 0.05) the live weight gain, feed intake, or feed conversion ratio (FCR) of the broilers compared with those fed with the C diet. Blood total bilirubin, direct and indirect bilirubin, triglycerides, cholesterol, low-density lipoprotein (LDL), and very LDL were not different among the experimental groups. However, blood aspartate aminotransferase levels were increased (p < 0.05) in the Gr1 and Gr3 groups compared with the other treatment groups. All dietary treatments decreased the serum creatinine levels (p < 0.05) compared with the C group. The Gr2 broilers had greater serum total protein and globulin (p < 0.05) than those receiving the other treatments. Increasing dietary Lys levels resulted in a significant improvement in duodenum villus height and width (p < 0.05), while the low-CP diets resulted in shorter villi length and width, along with degenerated areas and lymphocytic infiltration. Low dietary CP content induced hepatocyte disorganization and moderate degeneration, along with vacuolated hepatic cells, excessive connective tissue, and lymphocytic infiltration. The cortical regions of the kidney exhibited obvious alterations in the Gr3 and Gr4 groups and large interstitial spaces were found between tubules. Renal tubules in the Gr3 and Gr4 groups were smaller in size and some of these tubules were atrophied. In conclusion, reducing dietary CP levels to 1% or 2% lower than the recommended level did not negatively affect growth performance, inducing minimal influence on the blood metabolic indicators of health status, and resulting in moderate alterations to the histomorphology of the duodenum, liver, and kidney. Furthermore, increasing the Lys content by 10% above the recommended level improved the growth performance, health status, and histomorphology of the duodenum, liver, and kidney in broiler chickens.

Multiple amino acid supplementations to reduce dietary protein for pigs during early and late finisher periods under commercial conditions.

With the easy availability and competitive prices of crystalline amino acids (AAs), the reduction of dietary crude protein (CP) for pigs during early and late finisher periods is possible under commercial conditions. Two experiments were conducted to assess the growth efficiency of early and late-finishing pigs fed with protein-restricted diets supplemented with Lys, Met, Thr, Trp, Val, Ile and His. In Experiment 1, 840 early finishing pigs were allocated to four dietary treatments with CP levels designed at 150, 142, 134, and 126 g kg-1 diet. In Experiment 2, 768 late-finishing pigs were allotted to four dietary treatments providing CP levels at 140, 130, 120, and 110 g kg-1 diet. In Experiment 1, the data showed that CP levels could be decreased from 150 to 126 g kg-1 without adversely affecting performance of early finishing pigs as no significant difference was observed for final bodyweight, average daily gain (ADG), feed to gain ratio (F:G), or average daily feed intake (ADFI). In Experiment 2, late-finishing pigs consuming 120 g kg-1 CP tended to have the highest ADG and lowest F:G whereas those fed the 110 g kg-1 CP diet showed the opposite trend. Based on quadratic analysis, the optimum CP levels to maximize ADG and minimize F:G were 126 and 127 g kg-1 , respectively. These findings showed that dietary CP levels could be decreased to 126 g kg-1 for early finishing pigs while improved performance was noted in late-finishing pigs consuming 120 g kg-1 CP. © 2023 Society of Chemical Industry.

Effect of Reduced Crude Protein Level on Fecal Nitrogen Excretion and Blood Profile in Finishing Pigs

The purpose of this experiment was to evaluate the effects of a low-protein diet on the selected variables of protein and energy metabolism in the blood serum as well as on the indicators of fermentation in the faeces (fecal crude protein, ammonia, pH, volatile fatty acids, and dry matter). Twelve finishing pigs (initial body weight: 64.6 ± 3.35 kg) were randomly divided into two groups and fed basal diets with crude protein (CP) levels of 13.6% and 15.4%, respectively. The Lysine, Methionine, Threonine, and Tryptophan levels in the 13.6% CP group were the same as those in the 15.4% CP group after the addition of four crystalline amino acids—Lysine, Methionine, Threonine, and Tryptophan to the diet. The blood and faeces samples were taken from the cranial vena cava and from the rectum at the end of the study period (44 days). The results showed that with the decrease in dietary CP level from 15.4% to 13.6% (a decrease of 1.8%), the fecal crude protein, the fecal ammonia, as well as the blood urea level decreased in the experimental group compared to the control group (P&lt; 0.05 and 0.01, respectively).

Growth performance and carcass traits of indigenous Nigerian guinea fowl fed on different dietary protein levels.

This work examined the results of different dietary protein levels on indigenous Nigerian guinea fowl growth performance and carcass yield. One hundred and eight unsexed indigenous keets were randomly assigned to three treatments with experimental diets containing 22%, 24%, and 26% crude protein (CP) in a completely randomized design, with 3 replicates with 12 keets in each replicate. The parameters were measured, including proximate composition, feed intake, growth rate, feed conversion ratio (FCR), and carcass yield. The birds fed diets containing 24% CP gained the most body weight at 619.83 gm and had the highest FCR of 3.45. The presence of CP had an impact that was significant (p < 0.05) on most carcass traits and prime cuts but not on gastrointestinal tract weight, head weight, dress percentage, or organ yield. The study concluded that the dietary CP level of 24% was optimal for body weight gain and carcass yield.

Effect of age and dietary crude protein level on nitrogen excretion in Holstein bull calves

The aim of the present study was to investigate the effect of age and dietary crude protein (CP) level on nitrogen (N) excretion in Holstein bull calves. Thirty-six Danish Holstein bull calves were divided into 4 age groups; 12, 22, 32, and 42 weeks old (W12, W22, W32, and W42), respectively, with 9 animals per group. Within age group, calves were blocked in groups of 3 according to age and weight, and randomly assigned to the dietary treatments in a 3 × 3 Latin square design. The dietary treatments consisted of 4 diets in total, with CP concentrations of 10.9, 14.1, 16.9, and 20.2%, of which the 3 diets with the highest CP concentrations (i.e. 14.1, 16.9, and 20.2%) were provided to W12 and W22 calves, whereas the 3 diets with the lowest CP concentrations (i.e. 10.9, 14.1, and 16.9%) were provided to W32 and W42 calves. The experiment was divided into 3 periods, all lasting for 2 weeks in which the first 11 days were used as adaptation, while the last 3 days were used for sampling and recording. Feed and water intake were recorded daily, and feces and urine samples were collected and analyzed for chemical composition. Intake of DM increased for all age groups with greater dietary CP level (P < 0.01), and was greatest in the oldest bull calves (P < 0.01). Urinary N excretion was positively correlated with N intake (P < 0.01) and age of the calves (P < 0.01). Fecal output of N increased with increasing dietary CP level (P = 0.05), but might mainly be explained by the greater feed intake observed with increasing CP level in the diet. When increasing the dietary CP level, the proportion of N intake excreted in urine increased (P < 0.01), whereas the proportion of N intake excreted in feces decreased (P < 0.01). In addition, the proportion of N intake excreted in urine was greatest in the oldest bull calves (P < 0.01). Furthermore, simple prediction equations for N excretion in urine and feces, respectively, were established and considered reliable proxies for N excretion in Holstein bull calves for application on farm.

In Vitro Rumen Fermentation and Post-Ruminal Digestibility of Sorghum-Soybean Forage as Affected by Ensiling Length, Storage Temperature, and Its Interactions with Crude Protein Levels.

The study aimed to evaluate the effects of ensiling length, storage temperature, and its interaction with crude protein (CP) levels in sorghum−soybean forage mixtures on in vitro rumen fermentation and post-ruminal digestibility of nutrients. The dietary treatments consisted of fresh forages (d 0) and silages of sorghum and soybean stored indoors or outdoors for 75 and 180 d with additional ingredients to make two dietary CP levels, 90 and 130 g/kg dry matter (DM) and a forage-to-concentrate ratio of 80 to 20. An in vitro procedure was conducted using the ANKOM RF technique to study rumen fermentation. The dietary treatments were incubated in duplicate for 8 and 24 h in three runs. After each incubation time, in vitro rumen fermentation parameters were measured, and the protozoa population was counted using a microscope. Post-ruminal digestibility was determined using the pepsin and pancreatic solubility procedure. Cumulative gas production (GP) increased quadratically with ensiling length (8 h, p < 0.01; 24 h, p = 0.02), and the GP differed between CP levels at both incubation times (p < 0.01). However, total short-chain fatty acid (SCFA) concentrations in rumen inoculum increased quadratically with ensiling length (p < 0.01; for both incubation times), and interaction between ensiling length and CP levels was observed in proportions of acetate and propionate after 24 h of incubation (p < 0.01; for both incubation times). Similarly, an interaction between ensiling length and CP levels was found in the proportion of valerate after 24 h of incubation (p < 0.01). There was a quadratic response to ensiling length in the NH4−N concentration after 8 h (p < 0.01) and 24 h (p < 0.05), and the CP level also differed (p < 0.01) at both incubation times. The ciliate protozoa count after 24 h was higher in low CP diets than in high CP diets (p = 0.04). The amount of CP in the undegraded substrate at both incubation times differed between CP levels (p < 0.01; for both incubation times). An interaction effect between ensiling length and storage temperature after 8 h (p = 0.02) and 24 h (p < 0.01) was observed for intestinal CP digestibility. The effect of CP levels on intestinal CP digestibility differed after 8 h (p < 0.01) and 24 h (p < 0.01). In conclusion, increasing ensiling length beyond 75 d reduced CP digestibility, and additional CP inclusion did not ameliorate this.

Effects of pre-partum dietary crude protein level on colostrum fat globule membrane proteins and the performance of Hu ewes and their offspring.

Dietary proteins play important roles in the growth and reproduction of sheep, and the ewe's demand for proteins increases dramatically during late pregnancy. This research aimed to investigate the effect of dietary crude protein (CP) levels during late pregnancy on colostrum fat globule membrane (MFGM) protein and the growth performance of Hu sheep and their offspring, and provide a reference for the protein intake of ewes during late pregnancy. A total of 108 multiparous Hu sheep (45.6 ± 1.18 kg) were selected for this study, then 60 pregnant ewes confirmed by B-scan ultrasonography were randomly divided into three treatments (20 ewes/treatment) and fed by total mixed ration pellet with CP levels at 9.00% (LP), 12.0% (MP), and 15.0% (HP) during late pregnancy, respectively. The weight and dry matter intake of ewes during late pregnancy were recorded to calculate the average daily gain (ADG) and feed conversion ratio (FCR). Twin lambs were weighed on days 0, 7, 14, 30, 60, and 180 after birth to calculate ADG. Meanwhile, the colostrum of ewes was collected within 12 h after delivery. The colostrum MFGM proteins were identified and quantified by the isobaric tag for relative and absolute quantification (iTRAQ) coupled with liquid chromatography-tandem mass spectrometry methods. In addition, biological functions of differentially expressed proteins (DEPs) were annotated by Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. The results revealed that a 15.0% CP level had significant effects on the BW of lambs on days 0, 7, and 30 (P < 0.05). Notably, a total of 1,529 MFGM proteins were identified and 286 DEPs were found among three treatments. Functional analysis showed that DEPs were mainly involved in cell growth, differentiation, and tissue repair, and involved in metabolic pathways, such as the porphyrin and chlorophyll metabolism pathways. In this study, lambs in HP treatment had better growth performance; moreover, dietary 15.0% CP level also affected the colostrum MFGM proteins composition of Hu ewes. These observations can facilitate future studies on the feeding regimen of ewes during late pregnancy.

Interactive effects of high temperature and crude protein levels on growth performance, nitrogen excretion, and fecal characteristics of broilers.

In the present study, we aimed to explore the interactive effects of high temperature (HT) and dietary crude protein (CP) levels on nitrogen (N) excretion, fecal characteristics, and growth performance of broilers. A total of 288 broilers (Arbor Acres) were divided into six groups with eight replicates (six broilers per replicate). Two temperatures (ambient temperature: AT, 23°C; HT: 28 ~ 32 ~ 28°C) and three diets (CP: 14.90%, 18.18%, or 21.19%, with equal amounts of essential amino acids) were examined in a 2 × 3 factorial design. The experiment arrangement was from 4 to 6weeks of age. The results showed that HT led to a significant decrease in the N excretion (P < 0.0001), average daily feed intake (P < 0.0001), and weight gain of broilers (P < 0.0001), while it markedly increased the fecal pH (P = 0.015), fecal moisture (P = 0.0014), uric acid (UA) contents (P = 0.0018), and feed/gain ratio (P < 0.0001). A low CP diet significantly decreased the N excretion (P < 0.001), fecal pH (P = 0.016), fecal moisture (P < 0.0001), and UA contents (P < 0.0001), while it markedly increased the feed/gain ratio (P < 0.001). In conclusion, HT had a negative impact on the fecal characteristics and growth performance of broilers but showed positive effects on N excretion. Moreover, decreased CP levels had a positive effect on the N excretion and fecal characteristics in broilers.

Dietary metabolizable energy and crude protein levels affect pectoral muscle composition and gut microbiota in native growing chickens

The experiment aimed to study effects of dietary metabolizable energy (ME) and crude protein (CP) levels alone and in interaction on performance, pectoral muscle composition and gut microbiota in native growing chickens. A total of 648 10-wks-old Beijing-You Chicken (BYC) female chickens were randomly allocated to 9 groups with 6 replicates per group and 12 chickens per replicate, and the chickens were fed with a 3×3 factorial diets (3 levels of dietary ME: 11.31 MJ/kg, 11.51 MJ/kg, 11.71 MJ/kg; and 3 levels of dietary CP: 14%, 15%, 16%). The results showed that dietary ME and CP levels didn't affect average feed intake (AFI), body weight gain, feed gain ratio (P > 0.05), but ME level significantly affected the AFI (P < 0.05); mortality rate of 11.31 MJ/kg group was the highest (P < 0.05). Dietary ME, CP levels, and the interaction significantly affected pectoral CP and crude fat (CF) content of the growing chickens (P < 0.01). Dietary CP level had opposite effects on pectoral CP and CF content (P < 0.01). The 16% CP increased the pectoral CF content, which may have a negative impact on meat flavor. Dietary ME level affected 11 types of pectoral free amino acids (FAA) contents, including aspartic acid, L-threonine (P < 0.05), also amino acid classification, for example, total amino acid (TAA) and essential amino acid (EAA) content (P < 0.05). The 11.51 MJ/kg group had the highest TAA, EAA, delicious amino acid (DAA) content and EAA percentage (P < 0.05), while 11.31 MJ/kg group had the lowest bitter amino acid (BAA) content and BAA percentage and the highest fresh and sweet amino acid (FSAA) percentage (P < 0.05). Dietary CP level significantly affected glutamine and tyrosine content (P < 0.05). The interaction of dietary ME and CP level affected C20:3n6 content, saturated fatty acid (SFA), and unsaturated fatty acid (UFA) percentage (P < 0.05). The CP level significantly affected SFA percentage (P < 0.05). The 16% CP level increased the diversity of gut microbiota, but at the same time increased the relative abundance of Proteobacteria (P < 0.05), which is a sign of microbiota disorder. The increase of dietary ME level resulted in a gradual decrease in the diversity and relative abundance of gut microbiota. In conclusion, the present study suggested that the medium dietary ME (11.51 MJ/kg) and low CP (14-15%) levels can be helpful for enhancing pectoral muscle composition, increase meat quality such as flavor and nutritional value, and benefit for gut microbiota in native growing chickens.

Comparison of nano-capsulated thyme essential oils on intestinal microbial population and anti-oxidation status of broilers

This study was conducted to evaluate the effects of non and nano-capsulated thyme essential oils with saturated and unsaturated lipids (tallow and canola oil) and two levels of diet crude protein (standard and low than standard) on intestinal microbial population and anti-oxidation status of broilers. In this study, 384 Ross-308 broiler chickens in a factorial engagement of 2×2×2 (2 medicinal plant essential oils, two sources of vegetable oils, and 2 levels of diet crude protein) were used in a completely randomized design with 8 treatments, 4 replicates, and 12 bird in each replicate for 42 days. Experimental periods included starter (1-10 days), grower (11-24 days), and finisher (25-42 days). Canola oil significantly reduced the intestinal coliforms population. In contrast, tallow increased them (P&lt;0.05), a similar effect was observed with thyme forms, so the lowest coliform population blogged to the nano-capsulated form of thyme. In contrast, the highest coliform population resulted in non-capsulated thyme essential oil (P&lt;0.05). In an interaction between thyme essential oil form and diet crude protein level, the lowest coliform population was observed with diet contained nano-capsulated thyme essential oil and low level of diet crude protein (P&lt;0.05). Regarding antioxidant status, reducing the diet crude protein increased MDA and GPX (P&lt;0.05). In an interaction between diet crude protein and thyme form, a diet with low crude protein and capsulated thyme increased the level of SOD (P&lt;0.05). In general, results of the current experiment indicated that in Ross-308, broiler chickens using capsulated thyme essential oil with canola oil and low crude protein improves intestine microbial population and antioxidant status of broilers.

PSX-A-2 Effects of Dietary Crude Protein Level and Corn Grain Processing on Whole-Body Urea Kinetics and in-Vitro Urea Secretion Into the Rumen of Sheep

Abstract In ruminants, urea-N salvaging allows secretion of endogenously-produced urea (UER) into the rumen, where it can provide N for microbial growth. Our objective was to determine the effects of dietary crude protein content and corn grain processing on whole-body urea kinetics and in vitro serosal-to-mucosal urea flux (Jsm-urea) across ruminal epithelia. Thirty-two Rideau-Arcott ram lambs were blocked by BW into groups of 4 and then randomly allocated within block to one of 4 dietary treatments (n = 8) in a 2 × 2 factorial design. Dietary factors were crude protein content (10.9% [LP] vs. 15.8% [HP]) and corn grain processing (whole-shelled [WSC] vs. steam-flaked [SFC]). Feeding SFC was expected to provide more ruminally-fermentable energy than WSC. Four blocks of animals (n = 4) were used in 4-d continuous infusions of 15N-15N with concurrent collections of urine and feces to determine whole-body urea kinetics. After 23 d of dietary exposure, lambs were killed to collect ruminal epithelia which were mounted in Ussing chambers to determine Jsm-urea. Lambs fed HP had greater N intake (P = 0.01) and total N excretion (P = 0.002) than those fed LP; however, retained N (g/d or % of N intake) was similar between the 2 groups. When expressed as absolute amounts, urea-N secreted into the gut (GER) and urea-N used for anabolic purposes (UUA) were similar across diets; however, lambs fed the LP diet had a greater GER/UER ratio (P = 0.02) and tended to have a greater UUA/GER ratio (P = 0.05) than lambs fed the HP diet. Diet had no effect on ruminal Jsm-urea. Grain processing had no effects on GER, UUA and Jsm-urea. These results suggest ruminants fed protein-restricted diets have a greater dependence on urea secretion into the gut to provide N for anabolic use.

Rearing broilers as mixed or single-sex: relevance to performance, coefficient of variation, and flock uniformity

With known variation in performance between male and female broilers and the fact that sourcing single-sex birds for use in research is becoming increasingly difficult, it becomes important to determine the effect of rearing method with male and female broilers on between-pen variation and body weight (BW) uniformity. We evaluated the performance response of broilers reared as single or mixed-sex to standard and reduced crude protein (CP) diets. The study was designed as a 2 × 3 factorial arrangement of treatments consisting of 672 Cobb-500 broilers assigned to 48 floor pens with 6 treatments, 8 replicates, and 14 birds per pen. The factors were rearing method (male single-sex, female single-sex, or equally mixed-sex) and dietary CP level (standard or reduced). For the overall period of the trial (d 0–35) there was a significant effect (P < 0.001) of rearing method and CP level on feed intake (FI) and feed conversion ratio (FCR). There was also a significant interaction between rearing method and CP level for BWG during d 0 to 35 (P < 0.01). There was a significant interaction between CP level and sex on d 34 BW (P < 0.01) where the reduced CP diet decreased the BW of both males and females, but to a greater extent the BW of the female birds. Dietary CP level had a significant effect on relative breast and drumstick weights with birds fed the reduced CP diet having significantly lower breast weights (P < 0.001) and higher drumstick weights (P < 0.01).This study suggests that male and female broilers have different CP requirements, and rearing birds as equally mixed-sex results in the lowest CV% for performance parameters and best BW uniformity compared to single-sex birds. Furthermore, when low CP diets are fed to broilers, they will prioritize the growth of more important body parts such as the legs.

Effect of age and dietary crude protein level on nitrogen excretion in dairy heifers

The aim of this study was to examine the effect of age and dietary crude protein (CP) level on nitrogen (N) excretion in dairy heifers and to develop simple models to predict N excretion on farm based on nutrient intake parameters. Thirty-six Danish Holstein heifers were divided into 4 age groups; 8, 12, 16, and 20 months old (M8, M12, M16, and M20), respectively, with 9 animals per group. Heifers within age groups were blocked in groups of 3 according to age and pregnancy stage and were randomly assigned to dietary treatments in a 3 × 3 Latin square design. The dietary treatments consisted of 4 diets in total with CP concentrations of 9.8, 12.2, 14.6, and 17.0%, respectively, of which the 3 diets with the highest CP concentrations (i.e. 12.2, 14.6, and 17.0%) were provided to M8 and M12 heifers, and the 3 diets with the lowest CP concentrations (i.e. 9.8, 12.2, and 14.6%) were provided to M16 and M20 heifers. The experiment was divided into 3 periods, each period lasting for 2 weeks of which the first 11 days were used as adaptation and the last 3 days were used for sampling and recording. Feed and water intake were recorded daily, and feces (n = 6, pooled) and urine samples (n = 2, pooled) were collected and analyzed for chemical composition. Fecal output of N increased with increased dietary CP level, and this was probably due to the increase in dry matter intake (DMI) and N intake observed when increasing dietary CP level. Urinary N excretion increased with increased CP level in the diet, and was greatest in older heifers. Thus, for dairy heifers, urinary N output appeared to be strongly correlated with dietary N intake and seemed to increase with age. A dietary CP level of 12.2% seemed sufficient for heifers in all age groups to maintain adequate rumen microbial digestion, underpinning the potential of reducing urinary N by dietary manipulation. However, due to the short experimental periods, this study cannot state whether this CP level fulfills the N requirement for growth during the whole rearing period of dairy heifers. Furthermore, a simple prediction equation was established for N excretion in feces: N feces (g/d) = 0.054 × N intake + 6.52 × DMI and was considered a reliable proxy for N excretion in replacement heifers for application on farm.

Effects of an emulsifier blend supplementation on growth performance, nutrient digestibility, intestinal morphology, and muscle fatty acid profile of broiler chickens fed with different levels of energy and protein

The effects of emulsifier blend (EB) supplementation of diets with various levels of metabolizable energy (ME) and crude protein (CP) on broiler performance, digestibility, gut morphology, and muscle fatty acid profile were investigated over a 42-d period. Diets were arranged factorially (2 × 2 × 3) and consisted of 2 levels of ME (normal [commercially recommended levels] and low [100 kcal/kg reduction in dietary ME]), 2 levels of CP and limiting amino acids (normal [commercially recommended levels] and low [95% of the normal CP level]), and 3 levels of EB supplementation (0, 1, and 2 g/kg of diet). A total of 1,200 one-day-old male broiler chickens (Ross 308) were randomly assigned to 12 treatment groups (5 pens/treatment with 20 birds/pen). Supplemental EB linearly improved (P < 0.05) final body weight, overall average daily gain, and feed conversion ratio, but the magnitude of the responses was greater in low-ME and low-CP treatments, resulting in significant ME × CP × EB interactions. Similarly, the inclusion of EB in the diet, particularly at 2 g/kg, increased the ileal digestibility of crude protein and crude fat, as well as the AMEn value (P < 0.05), but the response was greater at lower ME concentration, indicating significant ME × EB interactions. Additionally, there were CP × EB interactions (P < 0.05) for duodenal villus height and villus height/crypt depth ratio, indicating that the effect of EB on these responses was more marked at lower dietary CP levels. An increase in dietary EB levels was accompanied by a linear increase in the concentration of total saturated fatty acids and a linear decrease (P < 0.05) in the concentrations of total polyunsaturated fatty acids in both breast and thigh meat. In conclusion, the positive effects of EB supplementation, particularly at a dietary inclusion level of 2 g/kg, were clearly evident in broiler chickens fed with low nutrient diets (−100 Kcal/kg ME and/or −5% CP and limiting amino acids) in terms of growth performance, nutrient digestibility, and gut morphology.