Effects Of Dietary Protein Concentration Research Articles

The Effect of Dietary Protein Concentration on the Fecal Microbiome and Serum Concentrations of Gut-Derived Uremic Toxins in Healthy Adult Cats.

The purpose of this study was to evaluate the effect of feeding healthy adult cats with foods containing variable protein concentrations on the fecal microbiome and serum concentrations of the gut-derived uremic toxins indoxyl sulfate, p-cresol sulfate (pCS), and trimethylamine-n-oxide. Twenty healthy young adult cats were randomized into two groups and fed either a low-protein diet (LPD; 7.4 g/100 kcal ME) or a high-protein diet (HPD; 11.0 g/100 kcal ME) for a 12-week period. Serum uremic toxin concentrations were measured via liquid chromatography tandem mass spectrometry, and the fecal microbiome was characterized using shallow sequence shotgun metagenomics. Cats that consumed the HPD had higher pCS concentrations at 8 weeks (p = 0.028) when compared to baseline. After 12 weeks, cats fed the HPD had higher fecal alpha diversity indices at both the taxonomic and functional levels and lower fecal Bifidobacterium relative abundance compared to those cats fed the LPD. In conclusion, a change in diet and dietary protein concentration shifted the fecal microbial community and microbial function. Feeding cats a high amount of protein increased serum concentrations of the uremic toxin pCS; however, the effect was short-lived.

Effects of dietary protein concentration and degradability on performance, carcass characteristics, net energy utilization, and metabolizable protein balance of finishing beef heifers receiving 0 or 400 mg of ractopamine hydrochloride

This study evaluated the effects of feeding beef cattle finishing diets with greater than 14.0% dietary CP and with or without ractopamine hydrochloride (RH) on growth performance, carcass merit, net energy utilization, and metabolizable protein balance. Heifers (n = 525) were assigned to 48 pens in a generalized complete block design, and pens of cattle were assigned randomly to 0 or 400 mg of RH/animal per day and 3 CP treatments in a 2 × 3 factorial arrangement (n = 8 pens/treatment) fed for 35 d before slaughter. Dietary protein treatments were steamflaked corn-based diets containing 13.9% CP, 8.9% RDP, and 5.1% RUP (CON); 20.9% CP, 14.4% RDP, and 6.5% RUP (High RDP); or 20.9% CP, 9.7% RDP, and 11.2% RUP (High RUP) on a DM basis. No RH × CP interactions were observed. Final BW, ADG, water disappearance, DMI, and G:F were not different among CP treatments. Dressing percentage was greater for cattle fed High RDP than for those fed High RUP, but other carcass outcomes did not differ. The MP balance was greatest for High RUP, intermediate for High RDP, and least for CON. Cattle receiving 400 mg of RH had greater final BW, ADG, G:F, and hot carcass weight. The LM area was greater and KPH was less for 400 versus 0 mg of RH. Carcass-adjusted final BW, ADG, and G:F were greater for cattle consuming 400 mg of RH. Cattle fed 400 mg of RH had greater performance-adjusted and observed:expected NEm and NEg. The MP balance was less for 400 versus 0 mg of RH. Dietary CP requirements were greater for cattle fed 400 compared with 0 mg of RH but did not exceed the CP supplied by CON, High RDP, or High RUP. Feeding greater than 14.0% CP does not negatively affect performance or carcass characteristics of finishing cattle, and the absence of interactions between CP and RH suggests that RH does not increase CP requirements above those provided in a typical finishing cattle diet.

Effects of dietary protein concentration on growth and anti-oxidant capacity of coho salmon Oncorhynchus kisutch (Walbaum, 1792) alevins

Effects of dietary protein concentration on growth and anti-oxidant capacity of coho salmon Oncorhynchus kisutch (Walbaum, 1792) alevins

Effects of Dietary Protein Concentration on Lipid Metabolism Gene Expression and Fatty Acid Composition in 18-23-Month-Old Hanwoo Steers.

Simple SummaryIntramuscular fat or fatty acids content was regarded as a quality index of meat as it increases meat tenderness and flavor. In Korea, commercial Hanwoo farms have been supplying concentrate feeds that are 2–3% higher in crude protein (CP) content rather than conventional feeds throughout the entire program and have tried to shorten the feeding period to less than 28 months of age. This has led to a probable stability in lean-to-fat ratio in Hanwoo steers from 19 to 21 months of age. This stability could be linked to the regulation of the gene expression mediating lipogenesis during this phase. However, there is a lack of data regarding the effects of the protein level in isoenergetic concentrate diets on transcriptional activity of such genes at this phase. The conventional feeding program and the current one with relatively higher CP content were compared in two groups of twenty Hanwoo steers. Results showed that higher CP endorsement during the growing phase increased the expression of intramuscular PPARα (p < 0.1) and LPL (p < 0.05) and decreased the genes, such as VLCAD (p < 0.01), GPAT1 (p = 0.001), and DGAT2 (p = 0.016), which are involved in lipogenesis and fatty acid esterification. This may result in a relatively lower lipid turnover which could be responsible for shortening the feeding period.The present study evaluated the influence of dietary protein level on growth performance, fatty acid composition, and the expression of lipid metabolic genes in intramuscular adipose tissues from 18- to 23-month-old Hanwoo steers, representing the switching point of the lean-to-fat ratio. Forty steers with an initial live weight of 486 ± 37 kg were assigned to one of two treatment groups fed either a concentrate diet with 14.5% CP and or with 17% CP for 6 months. Biopsy samples of intramuscular tissue were collected to analyze the fatty acid composition and gene expression at 23 months of age. Throughout the entire experimental period, all steers were restrained twice daily to allow individual feeding. Growth performance, blood metabolites, and carcass traits, according to ultrasonic measurements, were not affected by the experimental diets. The high-protein diet significantly increased the expression of intramuscular PPARα (p < 0.1) and LPL (p < 0.05) but did not affect genes involved in fatty acid uptake (CD36 and FABP4) nor lipogenesis (ACACA, FASN, and SCD). In addition, it downregulated intramuscular VLCAD (p < 0.01) related to lipogenesis but also GPAT1 (p = 0.001), DGAT2 (p = 0.016), and SNAP23 (p = 0.057), which are involved in fatty acid esterification and adipocyte size. Hanwoo steers fed a high-protein diet at 18–23 months of age resulted in a relatively lower lipid turnover rate than steers fed a low-protein diet, which could be responsible for shortening the feeding period.

Higher dietary protein increases growth performance, anti-oxidative enzymes activity and transcription of heat shock protein 70 in the juvenile sea urchin (Strongylocentrotus intermedius) under a heat stress

This study was conducted to investigate the effect of dietary protein concentration (12%, 18%, 24%, 30% and 36%) on the growth performance, activity of anti-oxidative enzymes and heat shock protein 70 (HSP70) transcription in the sea urchin (Strongylocentrotus intermedius) under a heat stress. After 112 days of feeding trial the sea urchins were heat stressed (26 °C) and the coelomic fluid and intestine sampled at time 0 and 15 min, 2 h and 6 h. The results showed that an increase in dietary protein (12%–24%), significantly increased (p < 0.05) the sea urchin weight gain rate (WGR). As dietary protein increased (from 18% to 36%), the gonadosomatic index (GI) of juvenile sea urchins also significantly increased (p < 0.05) from 18.0% to 22.6%. Superoxide dismutase (SOD) activity increased with dietary protein increase (12%–30%) and the enzyme activity was significantly higher (p < 0.05) in the coelomic fluid of sea urchins that were fed with 30% protein diets when compared to 12% and 36% protein diets at all time points after the heat stress. Catalase (CAT) activity showed a similar tendency with the increase in dietary protein concentration at time 0 and 15 min after the heat stress (p < 0.05). Transcription of HSP70 in the intestine also showed a similar trend to SOD and was highest in the animals that were fed with 30% protein diets (p < 0.05). Our results suggest that 24% protein diets could meet the requirements for growth performance but a 30% protein diet resulted in improved gonad development and anti-heat stress capacity in this sea urchin species.

Interactive effects of dietary protein concentration, a mono-component exogenous protease and ascorbic acid on broiler performance, nutritional status and gut health

A total of 640 male Ross 308 broiler chickens were used to explore the interactive effects of diet nutrient density, exogenous protease and ascorbic acid on performance, nutrient digestibility and various gut health metrics. A total of eight dietary treatments were arranged as a 2 × 2 × 2 factorial with the factors being adequate or reduced (~4%) crude protein and amino acids, without or with exogenous protease and without or with supplemental ascorbic acid. Over the 35-day experimental period, birds that received the adequate diet had higher (P &lt; 0.01) bodyweight gain and lower (P &lt; 0.001) feed conversion ratio (FCR) than birds that received the diet with reduced protein and amino acid density. Supplemental protease reduced (P &lt; 0.001) FCR and this influence was more apparent in birds fed the diet with reduced protein concentration. Gut tensile strength tended to be increased by protease (P = 0.09) and ascorbic acid (P = 0.06) supplementation. Supplemental protease reduced (P &lt; 0.001) jejunal goblet cell numbers and epithelial thickness and increased (P &lt; 0.05) villus height compared with unsupplemented diets. Ascorbic acid tended (P = 0.05) to increase sialic acid concentration in ileal digesta. Protease increased (P &lt; 0.01) the coefficients of apparent ileal digestibility for all amino acids other than methionine and this effect tended (P = 0.07 to 0.09) to be more pronounced in the low protein diet for aspartic acid, histidine and arginine. The concentration of taurine in ileal digesta was reduced (P &lt; 0.01) by protease whereas hydroxyproline concentrations tended (P = 0.09) to increase by ascorbic acid addition. These results confirm previous reports on the effectiveness of exogenous protease in diets reduced in crude protein and digestible amino acids. Furthermore, both protease and ascorbic acid may influence gut health through promotion of tensile strength, epithelial morphology and endogenous protein flow. The interaction between exogenous protease and ascorbic acid on gut health with an emphasis on collagen structure and tight junction integrity is an area for future study.

Interactive effects of dietary protein concentration and aflatoxin B1 on performance, nutrient digestibility, and gut health in broiler chicks

A 20-day trial was conducted to determine the impact of aflatoxin B1 (AFB1) and dietary protein concentration on performance, nutrient digestibility, and gut health in broiler chicks. The 6 dietary treatments were arranged in a 2 × 3 factorial with 3 crude protein (CP) concentrations (16, 22, and 26%) with or without 1.5 mg/kg AFB1. Each diet was fed to 6 replicate cages (6 chicks per cage) from zero to 20 d of age. Endogenous N and amino acid loss were estimated from birds fed a N-free diet with or without 1.5 mg/kg AFB1. A significant interaction between AFB1 and CP concentration was observed for growth performance, where reduction of BW gain, feed intake, gain:feed ratio, and breast muscle weight by AFB1 were most profound in birds fed the 16%-CP diet, and were completely eliminated when birds were fed the 26%-CP diet (AFB1 by CP interaction; P ≤ 0.023). Similarly, AFB1 reduced serum albumin, total protein, and globulin concentrations in birds fed 16 and 22% CP diets, but not in those fed the 26%-CP (AFB1 by CP interaction; P ≤ 0.071). Gut permeability was increased in birds fed AFB1-contamiated diets as measured by serum lactulose/rhamnose ratio (main effect; P = 0.04). Additionally, AFB1 tended to increase endogenous N loss (P = 0.09), and significantly reduced apparent ileal digestible energy and standardized ileal N and amino acid digestibility in birds fed the 16%-CP diet, while birds fed higher dietary CP were not affected (AFB1 by CP interaction; P ≤ 0.01). Further, AFB1 increased the translation initiation factor 4E-binding protein (4EBP1), claudin1, and multiple jejunal amino acid transporters expression (main effect; P ≤ 0.04). Results from this study indicate that a 1.5 mg AFB1/kg diet significantly impairs growth, major serum biochemistry measures, gut barrier, endogenous loss, and energy and amino acid digestibility. Aflatoxicosis can be augmented by low dietary CP, while higher dietary CP completely eliminated the impairment of performance, serum proteins, and nutrient digestibility from aflatoxicosis in zero to 20 d broiler chicks.

Effects of dietary protein concentration and ractopamine hydrochloride on performance and carcass characteristics of finishing beef steers.

Ractopamine hydrochloride (RAC) is used in the feedlot industry to increase daily gain, improve feed efficiency, and increase HCW. However, little work has been done to determine whether additional protein is needed in the diet to maximize the benefit of RAC in beef cattle. Objectives of our experiment were to determine if feeding additional CP in conjunction with RAC would improve animal performance and carcass characteristics. Therefore, an experiment was conducted using finishing diets containing 13.5 or 17.5% CP with 0 or 300 mg of RAC for 30 to 33 d at the end of the finishing period. Beef steers ( = 438; 387.8 ± 1.9 kg initial BW) were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement (16 pens total, 4 pens/treatment). No interactions between feeding RAC and CP level were detected ( > 0.19) for animal performance or carcass traits. Final BW did not differ among treatment ( = 0.37); however, final BW had a tendency to be 2% greater ( = 0.07) when the 13.5% CP diet was fed. Dry matter intake was not different between steers fed 0 or 300 mg/d of RAC ( = 0.20), yet DMI was 12% greater for cattle fed the 13.5% CP compared with steers fed the 17.5% CP diet ( < 0.01). Daily gain did not differ for cattle fed different levels of RAC or CP ( > 0.16). The G:F was 3.6% greater for cattle fed 300 vs. 0 mg/d of RAC ( = 0.04). The G:F was 8.7% greater for cattle fed the 17.5% diet vs. the 13.5% CP diet ( < 0.01), which can be attributed to the decreased DMI for cattle fed the 17.5% CP diet. Hot carcass weight was not different for steers fed 0 or 300 mg/d of RAC ( = 0.36) or for steers fed the 13.5% diet vs. 17.5% CP diet ( = 0.93). Dressing percentage was 1.5% greater for cattle fed 300 vs. 0 mg/d of RAC ( = 0.05) but was not different between cattle fed the different CP levels in the diet ( = 0.16). Longissimus area, adjusted 12th-rib fat, and marbling score did not differ across RAC or CP treatments ( > 0.26). Additionally, no differences in USDA yield grade or percentage of cattle grading USDA Choice were detected for RAC or CP treatments ( > 0.26), which also supports the idea that quality grade of cattle fed RAC at the same level of fatness is not impacted. Our data indicate excess protein did not enhance the response to RAC, and furthermore, the improved performance from RAC reported by others was not observed other than a small increase in G:F.

Effects of dietary protein concentration on performance and nutrient digestibility in Pekin ducks during aflatoxicosis

A 14-d study was conducted to determine the impact of dietary crude protein concentration on performance, serum biochemistry, and nutrient digestive functions in Pekin ducklings during aflatoxicosis. A total of 144 male Pekin ducklings were randomly allotted to 4 dietary treatments arranged in a 2×2 factorial with 2 crude protein (CP) (20 and 24% on an analyzed basis) with or without 0.2 mg/kg aflatoxin B1 (AFB1) (0.21 mg/kg analyzed). The AFB1 reduced BW gain, feed intake, and breast muscle weight by 33 to 43% (P<0.0001). Serum concentration of protein, glucose, and Ca were also decreased by AFB1 (P≤0.0015), while pancreatic activities of amylase and lipase were increased by AFB1 (P<0.005). Apparent N digestibility was not affected by dietary treatment, whereas apparent ileal digestible energy was reduced 7.6% by AFB1 (P=0.0003). Higher dietary CP improved BW gain, gain:feed ratio, and breast muscle weight (P≤0.021), and tended to improve feed intake (P=0.094), but did not improve serum measures, digestive enzyme activity, or nutrient digestibility. No statistical interaction of AFB1 by CP was observed for any measures. Results from the current study suggest that AFB1 at low concentration can significantly impair performance of Pekin ducklings primarily through inhibited feed intake, as well as influence nutrient digestion processes (jejunum morphology, digestive enzyme activity, and apparent energy digestibility). Higher dietary CP can improve growth performance of ducklings regardless of AF exposure, but did not interact with dietary AFB1 on performance, serum biochemistry, or nutrient digestion in Pekin ducklings from hatch to 14 d.

Signaling Pathways Related to Protein Synthesis and Amino Acid Concentration in Pig Skeletal Muscles Depend on the Dietary Protein Level, Genotype and Developmental Stages.

Muscle growth is regulated by the homeostatic balance of the biosynthesis and degradation of muscle proteins. To elucidate the molecular interactions among diet, pig genotype, and physiological stage, we examined the effect of dietary protein concentration, pig genotype, and physiological stages on amino acid (AA) pools, protein deposition, and related signaling pathways in different types of skeletal muscles. The study used 48 Landrace pigs and 48 pure-bred Bama mini-pigs assigned to each of 2 dietary treatments: lower/GB (Chinese conventional diet)- or higher/NRC (National Research Council)-protein diet. Diets were fed from 5 weeks of age to respective market weights of each genotype. Samples of biceps femoris muscle (BFM, type I) and longissimus dorsi muscle (LDM, type II) were collected at nursery, growing, and finishing phases according to the physiological stage of each genotype, to determine the AA concentrations, mRNA levels for growth-related genes in muscles, and protein abundances of mechanistic target of rapamycin (mTOR) signaling pathway. Our data showed that the concentrations of most AAs in LDM and BFM of pigs increased (P<0.05) gradually with increasing age. Bama mini-pigs had generally higher (P<0.05) muscle concentrations of flavor-related AA, including Met, Phe, Tyr, Pro, and Ser, compared with Landrace pigs. The mRNA levels for myogenic determining factor, myogenin, myocyte-specific enhancer binding factor 2 A, and myostatin of Bama mini-pigs were higher (P<0.05) than those of Landrace pigs, while total and phosphorylated protein levels for protein kinase B, mTOR, and p70 ribosomal protein S6 kinases (p70S6K), and ratios of p-mTOR/mTOR, p-AKT/AKT, and p-p70S6K/p70S6K were lower (P<0.05). There was a significant pig genotype-dependent effect of dietary protein on the levels for mTOR and p70S6K. When compared with the higher protein-NRC diet, the lower protein-GB diet increased (P<0.05) the levels for mTOR and p70S6K in Bama mini-pigs, but repressed (P<0.05) the level for p70S6K in Landrace pigs. The higher protein-NRC diet increased ratio of p-mTOR/mTOR in Landrace pigs. These findings indicated that the dynamic consequences of AA profile and protein deposition in muscle tissues are the concerted effort of distinctive genotype, nutrient status, age, and muscle type. Our results provide valuable information for animal feeding strategy.

Spatial distribution of digestive proteinases in the midgut of the Pacific white shrimp (Litopenaeus vannamei) indicates the existence of endo-ectoperitrophic circulation in Crustacea.

The effect of dietary protein concentration on the spatial distribution of digestive proteinases in the shrimp Litopenaeus vannamei indicates the existence of endo-ectoperitrophic enzyme circulation in this species. Samples recovered from the midgut gland tissues, stomach contents, three different portions of the midgut and feces were used for quantitative and qualitative analyses of the composition and distribution of the digestive proteinases. Animals were divided into three different groups: (1) animals (controls) fed with a commercial 35% protein diet, (2) animals fed with a commercial diet supplemented with ovalbumin to a final protein concentration of 60%; (3) animals fed with an 80% protein diet. Quantitative determinations using different substrates and zymograms showed that increasing protein concentration in the diet alters the distribution of proteinases along the digestive tract. Composition of proteinases in the midgut gland, stomach contents, midgut sections and feces were similar, but not identical. Chymotrypsin and trypsin paralogues were identified in all enzyme sources in a concentration gradient along the midgut in the control shrimp, the expected distribution supporting the existence of a recycling mechanism. The occurrence of a peritrophic membrane in other Decapoda suggests that endo-ectoperitrophic circulation of digestive enzymes and nutrients may also occur in other crustaceans and also extends beyond the Insecta.

Effects of dietary protein concentration on ammonia volatilization, nitrate leaching, and plant nitrogen uptake from dairy manure applied to lysimeters.

This lysimeter experiment was designed to investigate the effects of dietary crude protein (CP) concentration on nitrate-N (NO-N) and ammonia (NH) losses from dairy manure applied to soil and manure N used for plant growth. Lactating dairy cows were fed diets with 16.7% CP (HighCP) or 14.8% CP (LowCP) content. Feces and urine were labeled with N by ruminal pulse-doses of NHCl. Unlabeled and N-labeled feces and urine were used to produce manure for a study with 21 lysimeters in a greenhouse. Manure application rate was 277 kg N ha. Ammonia emissions were measured at 3, 8, 23, 28, 54, and 100 h after manure application. Manure was incorporated into the soil, and a leaching event was simulated. Spring barley was planted (387 plants per m) 7 d after the leaching event and harvested at senescence. Ammonia emission rates and the contribution of urinary N to NO-N were on average about 100% greater for HighCP vs. LowCP manures. With both LowCP and HighCP manures, a greater proportion of urinary vs. fecal N was recovered in leachate NO-N. There was no difference in whole-crop barley N yields between LowCP and HighCP manures, but barley kernel N yield tended to be greater ( = 0.09) for lysimeters treated with HighCP manures. Using a unique labeling approach, this lysimeter experiment demonstrated that when applied at equal soil N application rates, manure from cows fed the HighCP diet resulted in markedly greater NH emissions and urinary N losses with leachate NO-N than manure from cows fed the LowCP diet.

Effect of dietary protein concentration on ammonia and greenhouse gas emitting potential of dairy manure

Two experiments were conducted to investigate the effect of dietary crude protein concentration on ammonia (NH3) and greenhouse gas (GHG; nitrous oxide, methane, and carbon dioxide) emissions from fresh dairy cow manure incubated in a controlled environment (experiment 1) and from manure-amended soil (experiment 2). Manure was prepared from feces and urine collected from lactating Holstein cows fed diets with 16.7% (DM basis; HCP) or 14.8% CP (LCP). High-CP manure had higher N content and proportion of NH3- and urea-N in total manure N than LCP manure (DM basis: 4.4 vs. 2.8% and 51.4 vs. 30.5%, respectively). In experiment 1, NH3 emitting potential (EP) was greater for HCP compared with LCP manure (9.20 vs. 4.88mg/m2 per min, respectively). The 122-h cumulative NH3 emission tended to be decreased 47% (P=0.09) using LCP compared with HCP manure. The EP and cumulative emissions of GHG were not different between HCP and LCP manure. In experiment 2, urine and feces from cows fed LCP or HCP diets were mixed and immediately applied to lysimeters (61×61×61cm; Hagerstown silt loam; fine, mixed, mesic Typic Hapludalf) at 277kg of N/ha application rate. The average NH3 EP (1.53 vs. 1.03mg/m2 per min, respectively) and the area under the EP curve were greater for lysimeters amended with HCP than with LCP manure. The largest difference in the NH3 EP occurred approximately 24h after manure application (approximately 3.5 times greater for HCP than LCP manure). The 100-h cumulative NH3 emission was 98% greater for HCP compared with LCP manure (7,415 vs. 3,745mg/m2, respectively). The EP of methane was increased and that of carbon dioxide tended to be increased by LCP compared with HCP manure. The cumulative methane emission was not different between treatments, whereas the cumulative carbon dioxide emission was increased with manure from the LCP diet. Nitrous oxide emissions were low in this experiment and did not differ between treatments. In the conditions of these experiments, fresh manure from dairy cows fed a LCP diet had substantially lower NH3 EP, compared with manure from cows fed a HCP diet. The LCP manure increased soil methane EP due to a larger mass of manure added to meet plant N requirements compared with HCP manure. These results represent effects of dietary protein on NH3 and GHG EP of manure in controlled laboratory conditions and do not account for environmental factors affecting gaseous emissions from manure on the farm.

Growth-dependent effects of dietary protein concentration and quality on the biomechanical properties of the diaphyseal rat femur

ObjectivesThis study compares the effects of feeding growing rats with increasing concentra-tions of casein (C) and wheat gluten (G), proteins that show different biological qualities, on the morphometrical and biomechanical properties of the femoral diaphysis. Materials and methodsFemale rats were fed with one of ten diets containing different con-centrations (5–30%) of C and G between the 30th and 90th days of life (Control = C-20%). Biomechanical structural properties of the right femur middiaphysis were estimated using a 3-point bending mechanical test with calculation of some indicators of bone material properties. ResultsBody weight and length were affected by treatments, values being highest in rats fed the C-20% diet. G diets affected negatively both parameters. Changes in cross-sectional geome-try (mid-diaphyseal cross-sectional and cortical areas, femoral volume, and rectangular moment of inertia) were positively related to the C content of the diet, while they were severely and negatively affected by G diets. Similar behaviors were observed in the bone structural properties (fracture load, yielding load, diaphyseal stiffness and elastic energy absorption). When values of strength and stiffness were normalized for body weight, the differences disappeared. The bone material quality indicators (elastic modulus, yielding stress, elastic energy absorption/volume) did not differ significantly among all studied groups. Femoral calcium concentration in ashes was not significantly different among groups. ConclusionThe clear differences in strength and stiffness of bone beams induced by dietary protein concentration and quality seemed to be the result of an induced subnormal gain in bone structural properties as a consequence of a correlative subnormal gain in bone growth and mass, yet not in bone material properties.

Growth-dependent effects of dietary protein concentration and quality on the biomechanical properties of the diaphyseal rat femur

Objectives This study compares the effects of feeding growing rats with increasing concentrations of casein (C) and wheat gluten (G), proteins that show different biological qualities, on the morphometrical and biomechanical properties of the femoral diaphysis. Materials and methods Female rats were fed with one of ten diets containing different concentrations (5–30%) of C and G between the 30th and 90th days of life (Control = C-20%). Biomechanical structural properties of the right femur middiaphysis were estimated using a 3-point bending mechanical test with calculation of some indicators of bone material properties. Results Body weight and length were affected by treatments, values being highest in rats fed the C-20% diet. G diets affected negatively both parameters. Changes in cross-sectional geometry (mid-diaphyseal cross-sectional and cortical areas, femoral volume, and rectangular moment of inertia) were positively related to the C content of the diet, while they were severely and negatively affected by G diets. Similar behaviors were observed in the bone structural properties (fracture load, yielding load, diaphyseal stiffness and elastic energy absorption). When values of strength and stiffness were normalized for body weight, the differences disappeared. The bone material quality indicators (elastic modulus, yielding stress, elastic energy absorption/volume) did not differ significantly among all studied groups. Femoral calcium concentration in ashes was not significantly different among groups. Conclusion The clear differences in strength and stiffness of bone beams induced by dietary protein concentration and quality seemed to be the result of an induced subnormal gain in bone structural properties as a consequence of a correlative subnormal gain in bone growth and mass, yet not in bone material properties.

Effects of dietary protein concentration and coconut oil supplementation on nitrogen utilization and production in dairy cows

The objective of this study was to investigate the effect of metabolizable protein (MP) deficiency and coconut oil supplementation on N utilization and production in lactating dairy cows. The hypothesis of the study was that a decrease in ruminal protozoal counts with coconut oil would increase microbial protein synthesis in the rumen, thus compensating for potential MP deficiency. The experiment was conducted for 10 wk with 36 cows (13 primiparous and 23 multiparous), including 6 ruminally cannulated cows. The experimental period, 6 wk, was preceded by 2-wk adaptation and 2-wk covariate periods. Cows were blocked by parity, days in milk, milk yield, and rumen cannulation and randomly assigned to one of the following diets: a diet with a positive MP balance (+44g/d) and 16.7% dietary crude protein (CP) concentration (AMP); a diet deficient in MP (−156g/d) and 14.8% CP concentration (DMP); or DMP supplemented with approximately 500g of coconut oil/head per day (DMPCO). Ruminal ammonia tended to be greater and plasma urea N (20.1, 12.8, and 13.1mg/dL, for AMP, DMP, and DMPCO diets, respectively) and milk urea N (12.5, 8.3, and 9.5mg/dL, respectively) were greater for AMP compared with DMP and DMPCO. The DMPCO diet decreased total protozoa counts (by 60%) compared with DMP, but had no effect on the methanogens profile in the rumen. Total tract apparent digestibility of dry matter and CP was decreased by DMP compared with AMP. Fiber digestibility was lower for both DMP and DMPCO compared with AMP. Urinary N excretion was decreased (by 37%) by both DMP and DMPCO compared with AMP. The DMP and DMPCO diets resulted in greater milk N efficiency compared with AMP (32.0 and 35.1 vs. 27.6%, respectively). Milk yield was decreased by both DMP and DMPCO compared with AMP (36.2, 34.4, and 39.3kg/d, respectively) and coconut oil supplementation suppressed feed intake and caused milk fat depression. Coconut oil supplementation decreased short-chain fatty acid (C4:0, C6:0, and C8:0) concentration and increased medium-chain (C12:0 and C14:0) and total trans fatty acids in milk. Overall, the MP-deficient diets decreased N losses, but could not sustain milk production in this study. Coconut oil decreased feed intake and similar to DMP, suppressed fiber digestibility. Despite decreased protozoal counts, coconut oil had no effect on the methanogen population in the rumen.

Effects of dietary protein concentration and balance of absorbable amino acids on productive responses of dairy cows fed corn silage-based diets

A cyclical changeover design experiment (3-wk periods; 12-wk total) was conducted to evaluate whether improving the balance of absorbable AA would allow the feeding of less crude protein (CP) without compromising production, thereby reducing the potential environmental pollution from dairy farms. Sixteen multiparous Holstein cows were assigned to 1 of 8 dietary treatments as total mixed rations (TMR) containing [dry matter (DM) basis] 45% corn silage, 5% coarsely chopped wheat straw, and 50% concentrate mixture. The 8 treatments were formulated to differ in dietary CP (14 and 16%; DM basis) and in the balance of absorbable AA achieved by changing the main protein source (MPS) of the concentrate mixtures [replacing soybean meal (SBM) with corn byproducts (CBP), dried corn distillers grains (DDG), and some corn gluten meal], and by adding a mixture of rumen-protected Lys and Met (RPLM). Feeding lactating dairy cows corn silage-based diets with 16% CP promoted significantly higher DM intakes and milk yields, and lower feed N-use efficiency than feeding diets with 14% CP. Replacing SBM with CBP significantly increased milk yields and decreased milk fat and protein concentrations, but had no effect on the efficiency of conversion of feed N into milk N. With 16% CP diets, the addition of RPLM decreased feed N use efficiency. A significant effect was observed for the MPS × RPLM interaction on milk protein concentrations. Plasma Lys concentration was lower with diets based on CBP, and plasma Met increased with RPLM. We did not find clear benefits of RPLM in facilitating a reduction of dietary protein without loss of production.

A meta-analysis of the effects of dietary protein concentration and degradability on milk protein yield and milk N efficiency in dairy cows

Data sets from North American (NA, 739 diets) and North European (NE, 998 diets) feeding trials with dairy cows were evaluated to investigate the effects of dietary crude protein (CP) intake and ruminal degradability on milk protein yield (MPY) and efficiency of N utilization for milk protein synthesis (MNE; milk N ÷ N intake) in dairy cows. The NA diets were based on corn silage, alfalfa silage and hay, corn and barley grains, and soybean meal. The NE diets were based on grass silage, barley and oats grains, and soybean and rapeseed meals. Diets were evaluated for rumen-degradable and undegradable protein (RDP and RUP, respectively) concentrations according to NRC (2001). A mixed model regression analysis with random study effect was used to evaluate relationships between dietary CP concentration and degradability and MPY and MNE. In both data sets, CP intake alone predicted MPY reasonably well. Addition of CP degradability to the models slightly improved prediction. Models based on metabolizable protein (MP) intake predicted MPY better than the CP or the CP-CP degradability models. The best prediction models were based on total digestible nutrients (TDN) and CP intakes. Similar to the MPY models, inclusion of CP degradability in the CP (intake or concentration) models only slightly improved prediction of MNE in both data sets. Concentration of dietary CP was a better predictor of MNE than CP intake. Compared with the CP models, prediction of MNE was improved by inclusion of TDN intake or concentration. Milk yield alone was a poor predictor of MNE. The models developed from one data set were validated using the other data set. The MNE models based on TDN and CP intake performed well as indicated by small mean and slope bias. This meta-analysis demonstrated that CP concentration is the most important dietary factor influencing MNE. Ruminal CP degradability as predicted by NRC (2001) does not appear to be a significant factor in predicting MPY or MNE. Data also indicated that increasing milk yield will increase MNE provided that dietary CP concentration is not increased, but the effect is considerably smaller than the effect of reducing CP intake.

Effect of dietary protein concentration and degradability on response to rumen-protected methionine in lactating dairy cows

An incomplete 8×8 Latin square trial (4-wk periods; 12 wk total) using 32 multiparous and 16 primiparous Holstein cows was conducted to assess the production response to crude protein (CP), digestible rumen-undegraded protein (RUP), and rumen-protected Met (RPM; fed as Mepron; Degussa Corp., Kennesaw, GA). Diets contained [dry matter (DM) basis] 21% alfalfa silage, 34% corn silage, 22 to 26% high-moisture corn, 10 to 14% soybean meal, 4% soyhulls, 2% added fat, 1.3% minerals and vitamins, and 27 to 28% neutral detergent fiber. Treatments were a 2×2×2 factorial arrangement of the following main effects: 15.8 or 17.1% dietary CP, with or without supplemental rumen-undegraded protein (RUP) from expeller soybean meal, and 0 or 9g of RPM/d. None of the 2- or 3-way interactions was significant. Higher dietary CP increased DM intake 1.1kg/d and yield of milk 1.7kg/d, 3.5% fat-corrected milk (FCM) 2.2kg/d, fat 0.10kg/d, and true protein 0.05kg/d, and improved apparent N balance and DM and fiber digestibility. However, milk urea N and estimated urinary excretion of urea-N and total-N also increased, and apparent N efficiency (milk-N/N-intake) fell from 33 to 30% when cows consumed higher dietary CP. Positive effects of feeding more RUP were increased feed efficiency and milk fat content plus 1.8kg/d greater FCM and 0.08kg/d greater fat, but milk protein content was lower and milk urea N and urinary urea excretion were elevated. Supplementation with RPM increased DM intake 0.7kg/d and FCM and fat yield by 1.4 and 0.06kg/d, and tended to increase milk fat content and yield of milk and protein.

Effects of dietary protein concentration on energetic efficiency and methane emission in lactating dairy cows

A series of studies have been undertaken to examine effects of dietary protein source and concentration on milk production, energy and nitrogen (N) utilisation efficiencies and fertility in dairy cows. The present study evaluated effects of dietary crude protein (CP) concentration on energetic efficiency and methane emission in lactating dairy cows.