Levels Of Rumen Degradable Protein Research Articles

Nutrient digestibility, characteristics of rumen fermentation, and microbial protein synthesis from Pesisir cattle diet containing non-fiber carbohydrate to rumen degradable protein ratio and sulfur supplement.

To achieve optimal feed efficiency in ruminants, especially Pesisir cattle, it is necessary to maintain a harmonious equilibrium between energy and protein levels within the rumen. Sulfur supplementation can potentially escalate the energy-protein balance in the rumen. The aim of this study was to explore the formulation of ruminant diets by synchronizing rumen degradable protein (RDP) and non-fiber carbohydrate (NFC) while adding sulfur minerals at different levels. Nutrient digestibility, NH3 concentration, volatile fatty acids (VFA) production, microbial protein synthesis (MPS), and methane gas production were assessed. We employed a randomized block design with a 2 × 2 × 3 factorial arrangement and examined diverse incubation periods of 6, 24, and 48 h. Treatment consisted of RDP (60% and 65%), NFC (35% and 40%), and sulfur (0%, 0.15%, and 0.3%) levels. In this study, the Tilley and Terry in vitro technique, which used Pesisir cattle's rumen fluid, was employed to assess the digestibility of dry matter, organic matter, acid detergent fiber, neutral detergent fiber, and RDP-Rumen undegradable protein. In addition, it measures various rumen fluid attributes, including pH, NH3, VFA, MPS, and methane gas production. Treatment with a coordinated combination of 65% RDP and 40% NFC combined with 0.15% sulfur supplement yielded significantly improved digestibility and notably reduced methane gas production (p < 0.05). The enhancement in digestibility and reduction in methane gas emissions can be attributed to the interaction of RDP, NFC, and sulfur. Feed digestibility was increased in the 65% RDP treatment with 40% NFC and 0.15% sulfur, along with a decrease in methane gas production.

Rumen degradable protein levels on fatty acid profile of rumen bacteria and milk fat of dairy cows supplemented with calcium salts of fatty acids.

This study aimed to evaluate the effects of calcium salts of fatty acids (CSFA) from soybean oil in diets with different levels of rumen degradable protein (RDP) on bio-hydrogenation extent, and fatty acid (FA) profile intake, omasal digesta, rumen bacteria, and milk fat. Eight Holstein lactating cows were used in a replicated 4 × 4 Latin square design. Treatments were arranged in a 2 × 2 factorial design with two CSFA levels (0 or 33.2g/kg DM of CSFA) and two RDP levels (98.0 or 110 g/kg DM). There was RDP and CSFA interaction effect on the omasal flow of total FA and some specific FA. Only in -CSFA diets, the higher RDP level increased omasal flow of total FA. Dietary RDP levels did not affect the FA profile of bacteria and milk fat. Feeding CSFA reduced or tended to reduce the bacterial proportion of C15:0, C16:0, C16:1, C17:0, and C18:0 FA and decreased the concentrations of short- and medium-chain FA (<18C) and increased the concentrations of unsaturated and long-chain FA (≥18C) in milk fat. Feeding CSFA of soybean oil increases the intake and omasal flow of FA and augments unsaturated FA content in bacteria pellets and milk fat.

Characterization of rumen microbiota in lactating Holstein cows fed molasses versus corn grain at two levels of rumen-degradable protein

We evaluated the influence of diets differing in non-fiber carbohydrates and rumen-degradable protein (RDP) levels on changes in the ruminal bacterial populations in lactating Holstein cows. In all, 12 ruminally cannulated cows were assigned to diets with high or low RDP levels. Within each RDP level, molasses was substituted for corn grain at a concentration of 0%, 5.25%, or 10.5% of diet dry matter in a replicated 3 × 3 Latin square design with 28-day periods. Liquid and solid rumen digesta fractions collected at the end of each period underwent 16S rRNA gene sequencing to identify operational taxonomic units and were analyzed for short-chain fatty acids. Protein degradability affected 6 bacterial genera, whereas carbohydrate alteration impacted 13 genera (p &amp;lt; 0.05). Of the 30 genera with the highest relative abundance, 26 differed by digesta fraction (p &amp;lt; 0.05), with Bacteroidetes genera showing a greater abundance in solids and Firmicutes genera demonstrating a greater prevalence in liquids. Regarding relative abundances, with increasing molasses, Succiniclasticum decreased in liquid (p &amp;lt; 0.05), and CF231, YRC22, Clostridium, Desulfovibrio, BF311, and Oscillospira increased in solids (p &amp;lt; 0.05). In contrast, at higher RDP levels, Succiniclasticum increased while YRC22 and Pseudobutyrivibrio decreased in solids (p &amp;lt; 0.05). Genera with abundances found to be correlated with fermentation products in the liquid included Shuttleworthia, Treponema, Lachnospira, and Schwartzia, which typically have lower relative abundances, showing strong positive correlations with molar proportions (mol%) of propionate, butyrate, and valerate (p &amp;lt; 0.05), and negative correlations with pH and acetate mol% (p &amp;lt; 0.05). Fibrobacter was positively correlated with lactate mol% (p &amp;lt; 0.05). Butyrate mol% exhibited a quadratic increase as molasses increased (p = 0.017), and lactate mol% rose with increased RDP levels (p = 0.042). No treatment effects were detected for pH propionate and valerate mol%; however, we observed a tendency (p = 0.075) for a quadratic effect of molasses treatment on the mol% of acetate. These findings substantiate the pivotal role of diet in shaping rumen microbiota and metabolism, elucidating a nuanced relationship between dietary components, bacterial community structure, and metabolic output. This offers a more detailed understanding of rumen function and the potential for high-precision dietary management in lactating cows.

Substitution of cane molasses for corn grain at two levels of degradable protein. I. Lactating cow performance, nutrition model predictions, and potential basis for butterfat and intake responses

Little data is presently available on our ability to predict the combined effect of modifying diets with feeds rich in sugars or starch (ST) and rumen-degradable protein (RDP) on the performance of high-producing dairy cows. The objective of this study was to compare responses of 59 lactating Holstein cows to substitution of cane molasses (Mol) for dry corn grain (CG) at 3 levels of Mol and 2 levels of RDP (+RDP or -RDP) in a randomized complete block design with a 3 × 2 factorial arrangement of treatments. Also, lactation responses predicted by 2 nutritional models were compared with observed responses, with Mol composition entered so that nonnutritive materials in Mol were not counted as potentially digestible carbohydrate. We hypothesized that dry matter (DM) intake and milk fat percentage responses would increase with increasing Mol and would potentially be greater with +RDP. For evaluation of the nutritional models, we adopted the null hypothesis that observed and predicted lactation performance would not differ. Cows were individually fed a common diet during a 2-wk covariate period followed by 8 wk on experimental diets. Diets were formulated to be isonitrogenous and provide similar amounts of ST and water-soluble carbohydrates. Experimental diets contained, on a DM basis, 35% corn silage, 20% alfalfa silage, and 16.6% crude protein. The 0, 5.25, and 10.5% Mol diets respectively contained 19.0, 14.5, and 10.0% CG; 28, 25, and 22% ST; and 5.5, 8.5, and 11.5% water-soluble carbohydrates. At 10 wk on study, cows averaged 45.5 kg of energy-corrected milk (ECM). The DM intake (DMI), and yields of milk, milk protein, and ECM, and milk N/intake N declined linearly with increasing Mol. Differences among diets were not detected for milk fat yield and ECM/DMI. No RDP or interaction effects were detected for these measures. That milk production efficiency did not differ across diets suggests that DMI was a primary driver of performance. The similar ECM/DMI and maintenance of milk fat yield would not have been predicted based on Mol and CG composition but may relate to differences in fermentation rates and products. As explanation for these results, we hypothesize that more rapid ruminal evolution of volatile fatty acids post-ingestion with Mol compared with CG may have provided masses of acetate and butyrate in excess of existing energy and synthetic needs that were shunted to milk fat production, and of propionate that depressed intake. The 2001 Dairy National Research Council model and the Cornell Net Carbohydrate and Protein System 6.55 in Nutritional Dynamic System Professional (2021) estimates of metabolizable protein-allowable ECM underestimated actual ECM for +RDP diets by 4.5 and 2.3 kg, respectively, and came close or overestimated for -RDP diets by 0.25 and 5.0 kg, respectively. Prediction discrepancies suggest issues with valuation of dietary protein based on degradability. Improved understanding of factors mediating these results would likely enhance our ability to predict animal responses.

Effects of sampling time on internal markers concentration and fecal recovery in dairy cows

We aimed to evaluate the effects of sampling time points on fecal contents of indigestible DM, NDF, and ADF, fecal recovery, and apparent digestibility in cows fed different levels of rumen degradable protein (RDP) without or with supplementation of calcium salts of fatty acids (CSFA). Eight multiparous Holstein cows (207 ± 23.6 days in milk, 618 ± 39.0 kg body weight; mean ± SD) were randomly allocated into a 4 × 4 Latin square design with 21 days of experimental period. A 2 × 2 factorial treatment arrangement was used in this study to evaluate the effects of calcium salts of fatty acids [CSFA: -CS, basal diet without fat supplementation; and +CS, with 33.2 g CSFA/kg DM] and rumen degradable protein (RDP) levels [LP: low RDP, 98.0 g/kg DM; and HP: high RDP, 110 g/kg DM]. Cows were fed twice daily, and total collection of feces was carried out for 72 h (from D15 8:00 to D18 8:00 h). In addition, spot samples were collected every nine hours, from D15 09:00 until D18 00:00 h. Samples of each sampling time were analyzed for iDM, iNDF, and iADF content. Internal markers showed a partial fecal recovery and, consequently, overestimated fecal excretion, and underestimated total-tract apparent digestibility. Indigestible NDF showed lower fecal recovery than iADF (855 vs. 935 g/kg). An interaction effect between marker and CSFA was observed for marker recovery where fat supplementation had greater influence on iADF recovery compared with iDM recovery. In addition, the fecal concentration of internal markers was affected by sampling time where the lowest concentrations of iDM were observed at 9:00 and the highest concentrations were detected between 15:00 and 00:00. Thus, experimental procedures need to consider diurnal variation of internal markers excretion. Internal markers, especially iDM, show partial fecal recovery.

Розчинність протеїну кормів як індикатор перетравності і доступності поживних речовин в раціонах бугайців

The research was conducted on steppe red bulls with duodenal and ileocecal anastomoses when feeding isoenergetic, isoprotein hay-concentrate diets with different levels of soluble protein (SP) and rumen degradable protein (RDP). We studied the transformation of dry matter (DM), organic matter (OM), crude protein (CP), crude ash (CA), crude fat (CF), crude fiber (CF) and nitrogen-free extractives (NFE) separately in a complex stomach, small (SI) and large (LI) parts of the intestine. Assimilation of protein by animals was assessed by the amount of it digested in SI, and unproductive costs — by the part of nitrogen in the urine. Diets consisted of hay, peas and mineral supplements. Different amounts of SP in the diets were achieved by feeding natural pea (control) or pea grilled at a temperature of +105°C (experiment). When feeding a diet with a reduced level of SP and RDP, the apparent intensity of digestion decreased, which was manifested in a slightly smaller amount of feed consumed, and in a smaller number of duodenal and ileocecal chyme. In a complex stomach, the CP digestibility of the experimental diet with a reduced level of SP was 10% lower. In the control diet with a high level of SP, more CP was degraded in rumen and more ammonium nitrogen was supplied to SI. The availability of CP for digestion in SI on the experimental diet was 5.8% higher, against control, with 8–10% higher digestibility of DM, OM and CP, but lower digestibility of CA and CF. In LI, the digestibility of nutrients in the studied diets was multidirectional. A significant amount of dietary protein was depreciated in the control diet with a high level of SP due to a 40% increase in urinary nitrogen excretion.

Effect of calcium salts of fatty acids and level of rumen degradable protein on nitrogen metabolism and performance of dairy cows fed corn silage-based diets

This experiment was designed to evaluate the effects of combining calcium salts of soybean oil fatty acids (CSFA) and two rumen degradable protein (RDP) levels on feed intake, ruminal fermentation, N metabolism, and performance of lactating cows fed corn silage-based diets containing 164 g/kg of crude protein and 6.72 MJ/kg of net energy. Eight rumen cannulated Holstein cows (207 ± 23.6 days in milk and 33.4 ± 2.45 kg/d of milk yield) were used in a 4 × 4 Latin square design with a 2 × 2 factorial treatment structure. Treatments consisted of diets with or without CSFA at 33.2 g/kg dry matter (DM) combined with either low (98 g/kg DM) or high level (110 g/kg DM) of RDP. Microbial protein synthesis was evaluated using the omasal sampling technique along with the triple marker system of digesta flow and 15N as a microbial marker. There was no interaction effect (P ≥ 0.15) between CSFA and RDP for all variables analyzed. Fat supplementation reduced (P ≤ 0.010) intake of nutrients (except ether extract), tended to increase (P = 0.076) rumination time, and increased (P = 0.015) ruminal pH. Calcium salts of fatty acids decreased (P ≤ 0.014) DM and organic matter ruminal digestibility and tended to reduce (P = 0.096) neutral detergent fiber ruminal digestibility. Dietary CSFA did not affect (P ≥ 0.32) ruminal flows of total non-ammonia N and microbial non-ammonia N, but increased (P = 0.022) microbial protein synthesis efficiency. Cows fed CSFA had greater (P ≤ 0.043) milk yield, feed efficiency, and N secreted in milk (g/kg N intake), and lower (P < 0.001) milk fat content in comparison with counterparts. Cows fed the diets with low RDP tended to have greater (P = 0.096) crude protein (CP) intake in comparison with cows fed diets with high RDP. Cows fed low RDP tended to exhibit greater (P = 0.057) ruminal acetate to propionate ratio than those fed high RDP. Low RDP decreased (P ≤ 0.048) starch total tract digestibility and ruminal protein degradation, tended to increase (P = 0.055) milk yield, and reduced (P = 0.002) milk protein content, but did not affect (P = 0.76) microbial protein synthesis efficiency compared to high RDP. Thus, lower RDP increased non-microbial non-ammonia nitrogen and reduced urinary losses of N, whereas CSFA decreased feed intake and improved microbial protein synthesis efficiency in mid-lactating cows. However, RDP level and CSFA association shows no interaction effect.

Reformulation of dairy cow diets based on rumen degradable protein and total digestible nutrient with varying levels on in vitro fermentability and digestibility

Rumen degradable protein (RDP) needs to be balanced with the adequacy of rumen undegradable protein (RUP) and energy for optimal microbial growth. Therefore, this study aimed to determine the optimal level of the RDP:RUP ratio and the energy level of dairy cattle rations using the in vitro method. The rumen inoculum used to carry out this research, was obtained from two bull rumen fistulated of Friesian Holstein. The treatments consisted of 3 levels of RDP:RUP ratio, namely 50:50, 55:45 and 60:40, while the energy levels consisted of total digestible nutrient (TDN) levels of 65.6% and 68.6%. The experimental design was a factorial randomized block, while data were analyzed using ANOVA and Duncan multi range’s test. The result showed the ratio of RDP:RUP had an effect on DMD, OMD, NH3, and rumen microbe. Furthermore, the higher TDN content increased significantly DMD, OMD, total VFA, and partial VFA. The increase in the microbial population was associated with a rise in total VFA and NH3 concentrations. This research concluded, the rations with RDP:RUP (60:40) ratio increased the population of bacteria and protozoa, while the availability of ammonia in the rumen, and the high level of TDN provided a higher supply of VFA, DMD, and OMD.

Effects of rumen-degradable-to-undegradable protein ratio in ruminant diet on in vitro digestibility, rumen fermentation, and microbial protein synthesis.

Background and Aim:Feeding ruminants must notice the degradability of feed, especially protein. Microbial rumen requires ammonia from rumen degradable protein (RDP) beside that ruminant require bypass protein or rumen undegradable protein (RUP) and microbial crude protein. The aim of the study was to discover the best RDP:RUP ratio in beef cattle diets commonly used by Indonesian farmers using an in vitro methodology.Materials and Methods:Samples of Pennisetum purpureum, Leucaena leucocephala, Indigofera zollingeriana, cassava, maize, palm kernel cake, rice bran, and tofu waste were formulated into dietary treatments (dry matter [DM] basis). All experiments were carried out using a 3×3×2 factorial, randomized block design with three replications. Treatments consisted of three protein levels (12%, 14%, and 16%), two energy levels (65% and 70%), and three RDP:RUP ratio levels (55:45, 60:40, and 65:35). The experimental diets were incubated in vitro using buffered rumen fluid for 48 h at 39°C. After incubation, the supernatants were analyzed to determine pH, ammonia concentration, total volatile fatty acid (VFA), and microbial protein synthesis. The residues were analyzed to determine DM, organic matter, protein, and RUP digestibility.Results:Increased protein, energy, and RDP levels increased digestibility, ammonia concentrations, total VFAs, and microbial protein synthesis (p<0.05), while rations with 16% protein lowered these parameters (p<0.05).Conclusion:Increased dietary protein (from 12% to 14% DM), energy (from 65% to 70% DM), and RDP (from 55% to 65% crude protein [CP]) levels increased nutrient digestibility, ammonia concentration, total VFA levels, and microbial protein synthesis. The diet containing 14% DM dietary protein and 70% DM energy, which contained 55%, 60%, or 65% CP RDP optimally increased nutrient digestibility, ammonia concentration, total VFA levels, and microbial protein synthesis. Thus, feed based on these RDP:RUP ratios can optimize ruminant productivity.

EFFECT DEGRADABLE PROTEIN LEVEL G/MJ METABOLIZABLE ENERGY THROUGH DIFFERENT STAGES OF LACTATION ON MILK YIELD AND COMPOSITION OF AWASSI EWES

This study investigated the effect of feeding two levels of rumen degradable protein in the rations during different stages of lactation on milk yield and components , twenty four cross breed Awassi ewes (Turkish Awassi × Iraqi Awassi) were used with their single lambs after birth aged 3-5 years, ewes were divided into two groups with average body weights 66.00 ± 2.32 kg and 67.10 ± 2.62 kg respectively, first group was control fed adequate level of degradable protein (10 g / Mj metabolizable energy) and second group fed high level of degradable protein (12.5 g / Mj metablizable energy) , Lactation period had been divided into three stages (early, 1-50 day ), ( mid , 51-100 day) and (late , 101-150 day), ewes were fed twice daily with restricted amount 2 kg in the early and mid and 1.5 kg in late lactation . Results showed that feeding adequate level of rumen degradable protein led to significant ( P&lt; 0.05) increase in milk yield 785 g/day and lactose 5.81% as compared with high level 619 g/day and 5.58% respectively, also milk yield decreased ( P&lt; 0.05) while milk fat increased ( P&lt; 0.05) with advance milk period. Blood parameters were not affected significantly by feeding degradable protein while serum glucose, total protein and albumin decreased (P&lt; 0.05) at late stage of milk production. Best results of interaction for rumen degradable protein and milk stages in milk yield and components yield were noted with feeding adequate level of rumen degradable protein in the early lactation.

Levels and degradability of crude protein in digestive metabolism and performance of dairy cows

Two experiments were conducted to evaluate the effect of the level and degradability of crude protein (CP) on the digestive metabolism and productive performance of dairy cows. In both experiments, 15 Holstein cows with 585 ± 40 kg of body weight were distributed in a Latin square design with five contemporary squares, three periods of 21 days and three treatments. In experiment 1, treatments consisted of three CP levels (130, 160 or 180 g CP/kg DM), while in experiment 2, the treatments consisted of three levels of rumen degradable protein (RDP; 80, 100 or 120 g RDP/kg DM) in diets with average of 163 g CP/kg DM. Variables evaluated in both experiments were dry matter intake (DMI), total apparent digestibility, milk yield (MY) and composition, ruminal fermentation and N balance. In experiment 1, the increase of CP from 130 to 180 linearly increased the organic matter, CP, neutral detergent fiber (NDF) and acid detergent fiber (ADF) intake (kg) and the apparent total digestibility coefficient of DM and CP. In addition, a linear increase of MY, fat corrected milk (FCM) and daily production of fat, protein, lactose, casein and total solids was observed. A linear increase in ruminal ammoniacal nitrogen (NH3-N) concentration and nitrogen excretion in milk, feces and urine was also observed. However, there was no observed effect on SCFA concentration. In experiment 2, the increase of the RDP from 80 to 120 increased the DMI, MY, FCM, milk protein content and digestibility coefficient of the NDF, ADF and ethereal extract. Additionally, there was an increase in NH3-N concentration and milk nitrogen excretion. The studies indicated that the increase of CP content up to 100 g RDP/kg DM increased the DMI and the productive performance of the cows, but also increased urine N. Thus, it is desirable that the increase of the CP through the increase of the RDP is carried out up to 100 g of RDP/kg DM, since there is elimination of nitrogen, decrease of milk yield and decrease of propionic acid in values above that level.

Evaluation of 15N and purine bases as microbial markers to estimate ruminal bacterial nitrogen outflow in dairy cows

The present study aimed to evaluate 15N and purine bases (PB) as markers for ruminal bacterial nitrogen (N) outflow in dairy cows. Additionally, the effects of calcium salts of fatty acids (CSFA) in diets with different levels of rumen degradable protein (RDP) on PB omasal flow, urinary recovery of purine derivatives (PD), and endogenous excretion of PD were evaluated. Eight ruminal cannulated Holstein cows, with 207 ± 23.6 (mean ± SD) days in milk, 618 ± 39.0 kg of body weight, and 33.4 ± 2.45 kg/d of milk yield were used in a replicated 4 × 4 Latin square design. Four treatments were arranged in a 2 × 2 factorial design to evaluate the following factors: CSFA addition [-CS: basal diet without CSFA; and + CS: with 33.2 g/kg dry matter (DM) of CSFA]; and the level of RDP (LRDP: low RDP, with 98 g/kg DM of RDP; and HRDP: high RDP, with 110 g/kg DM of RDP). Particle-associated bacteria (PAB) showed lower (P ≤ 0.008) 15N enrichment and purine N to total bacterial N ratio than liquid associated bacteria (LAB). Increasing RDP concentration reduced (P = 0.007) 15N enrichment and tended (P ≤ 0.095) to reduce PB concentration in bacterial pellets. Purine bases overestimated (P ≤ 0.002) LAB-NAN and total microbial flow but, regarding PAB-NAN flow, there was a trend of interaction (P = 0.067) between marker and fat supplementation effects. In the absence of fat supplementation, PB underestimated (P ≤ 0.05) the flow of PAB-NAN compared to 15N and failed to detect the negative effect of fat supplementation evidenced by 15N labeling. Omasal PB flow tended to increase (P = 0.061) in low protein degradability diets, but PD excretion was constant (322 ± 5,9 mmol/d, mean ± SE) regardless of diet and, as a result, urinary recovery of PB decreased (P = 0.007). Daily excretion of creatinine and endogenous PD was also unaffected by the diet and averaged 0.262 mmol/kg BW and 0.640 mmol/kg BW0.75, respectively. In conclusion, the response of PB and its urinary derivatives to variation in diet composition compared to 15N reveals their weaknesses in the estimation of microbial synthesis.

EFFECT OF RATIONS CONTENT OF DEGRADABLE PROTEIN AND BARLEY GRAIN (STARCH) IN MILK PRODUCTION , COMPONENTS AND SOME BIOCHEMICAL BLOOD PARAMETERS OF AWASSI EWES

This study was conducted in Al-Rashidiya animal breeding station, using 32 Awassi ewes (3-5 yrs old) with average body weight of 66.59 kg with their single born lambs. The ewes were divided randomly into 4 groups, the first (T1) and second (T2) groups fed on rations consist of 35% barley and contained two levels of rumen degradable protein (RDP) 10 and 13 g/ MJ metabolizable energy. while barley grain raised to 62% in the ration of third and fourth groups (T3 and T4) to increase the starch ratio with observance of the same level of RDP 10 and 13 g/ MJ respectively , and all the rations were iso calorie. Results indicated that RDP and starch levels had no significant effect on milk yield which were 968 , 1067 , 1127 ,and 867 g/ day, milk composition and yield with exception milk urea concentration were decreased (p<0.05) in T3 11.67 mg/ dl as compared with T2 21.14 mg/ dl, also milk urea concentration was increased significantly with RDP increase from 10 to 13 g/ MJ , but decreased (p<0.05) with increasing starch level. Ammonia concentration in rumen liquor decreased (p<0.05) after 2hrs of feeding in T1 4.57 mmol/ dl as compared with to T2 6.34 , T3 6.53 and T4 6.46 mmol/ dl. It was noted that treatments had no significant effect on body weight change in ewes , average daily gain in lambs and also in blood metabolites with exception the significant decrease (p<0.05) in the concentration of triglyceride in T3 14.67 mg/ dl as compared to other treatments were 20.19, 22.91 and 24.35 mg/ dl , also the increase in RDP level led to significant increased (p<0.05) in triglyceride concentration.

Starch and dextrose at 2 levels of rumen-degradable protein in iso-nitrogenous diets: Effects on lactation performance, ruminal measurements, methane emission, digestibility, and nitrogen balance of dairy cows

Our objectives were to determine the effects of readily rumen-available carbohydrate source (refined starch vs. dextrose), the level of rumen-degradable protein (RDP), and their interaction on lactation performance, ruminal measurements, enteric methane (CH4) emission, nutrient digestibility, and nitrogen (N) balance in lactating dairy cows. Eighteen mid-lactation multiparous Holstein cows were used in this split-plot study. The main plots were created by randomly assigning 9 cows to diets of 11 or 9% RDP obtained by altering the percentage of soybean meal, expeller soybean meal, and blood meal in the diet. All diets included 16.4% crude protein. In the subplots, the effects of 0:10, 5:5, and 10:0 refined starch:dextrose ratio (% of dietary dry matter) were determined in three 3 × 3 Latin squares by randomly assigning the 9 cows in each RDP level into squares. Each period lasted 4 wk, with the last 2 wk allotted for sample collection. Carbohydrate source × RDP level interaction tended to influence dry matter intake (DMI), the concentration of urinary N, and urinary urea-N. Replacing refined starch with dextrose increased DMI, the molar percentage of ruminal butyrate and valerate, daily CH4 production (g/d), and fecal N and decreased the molar percentage of ruminal branched-chain volatile fatty acids, feed efficiency (fat- and protein-corrected milk/DMI), and N use efficiency (milk N/intake N) but did not influence nutrient digestibility. Enteric CH4 production was negatively related to the molar percentage of ruminal propionate but positively related to the molar percentage of ruminal butyrate. Treatments did not influence milk production responses, but cows fed 9% RDP diets had lower ruminal ammonia concentration (7.2 vs. 12.3 mg/dL) and tended to excrete less urinary purine derivatives (428 vs. 493 mmol/d) compared with cows fed 11% RDP diets, suggesting lower ruminal synthesis of microbial protein. Reducing the level of RDP in iso-nitrogenous diets had no effect on nutrient apparent total-tract digestibility, manure excretion and composition, N balance, and CH4 production. In this study, treatments did not affect yield (20.0 g of CH4/kg of DMI) or intensity (13.1 g of CH4/kg of fat- and protein-corrected milk), but methane production (g of CH4/d) was 7.0% lower and N use efficiency (conversion of intake N into milk protein) was 7.8% higher for cows fed a diet of 28.1% starch and 4.6% water-soluble carbohydrate compared with diets with lower starch and higher water-soluble carbohydrate contents.

Nitrogen source and concentration affect utilization of glucose by mixed ruminal microbes in vitro

The availability of rumen-degradable protein (RDP) changes the use of carbohydrates by ruminal microbes. However, the effects of RDP on the simultaneous use of carbohydrate and formation of microbial products are not well described, although such information is needed to understand the potential effect on nutrient supplies for ruminants. The objective of this in vitro study was to compare the effects of different levels of RDP (0.15, 0.31, 0.46 g of N/L) from tryptone (Tryp) or urea (Ur) on product formation from glucose in fermentations with mixed ruminal microbes. The study had a randomized complete block design with 2 replicated fermentation runs and destructive sampling at 0, 0.5, 1, 2, 3, 4, and 5 h. All rates given are first-order rate constants. Glucose disappearance rates and organic acid carbon (C) production rates tended to be or were greater for Tryp (0.64 and 0.58 h-1) than for Ur (0.51 and 0.22 h-1), respectively, but did not differ by N level. Maximum detected microbial N production was 67% greater for Tryp (2.35 mg) than for Ur (1.41 mg), which did not differ from the basal medium (1.47 mg). The pattern of glycogen accumulation over time tended to differ between Tryp and Ur: glycogen peaked and declined earlier in the fermentations with Tryp, resulting in less glycogen remaining at 5 h with Tryp (7.2 mg) than with Ur (11.0 mg). At the point of maximum microbial N accumulation, Tryp and Ur did not differ in the amount of glucose C used (29.4 and 28.9 mg), but did differ in the amounts of cell C (10.1 and 6.0 mg), organic acid C (17.4 and 13.8 mg), glycogen C (3.81 and 6.07 mg), and total microbial product C (35.4 and 29.6 mg) present. This resulted in increased efficiency for Tryp compared with Ur for cell C produced per used glucose C, corrected for glycogen C (0.40 and 0.27 mg/mg), and it resulted in a tendency for increased yield of cell C per organic acid C (0.59 and 0.44 mg/mg). Total product C exceeded used glucose C for Tryp, likely because of incorporation or fermentation of C from the provided AA. Overall, RDP source altered the temporal patterns of glucose use and the patterns and amounts of microbial product formation.

0729 Effect of dextrose and purified starch at two levels of rumen degradable protein on lactation performance and enteric methane emission in dairy cows

0729 Effect of dextrose and purified starch at two levels of rumen degradable protein on lactation performance and enteric methane emission in dairy cows

Effects of Degradable Protein and Non-Fibre Carbohydrates on Microbial Growth and Fermentation in the Rumen Simulating Fermenter (Rusitec)

A rumen simulation technique (Rusitec) apparatus with eight 800 ml fermentation vessels was used to investigate the effects of rumen degradable protein (RDP) level and non-fibre carbohydrate (NFC) type on ruminal fermentation, microbial growth, and populations of ruminal cellulolytic bacteria. Treatments consisted of two NFC types (starch and pectin) supplemented with 0 g/d (low RDP) or 1.56 g/d (high RDP) sodium caseinate. Apparent disappearance of dry matter and organic matter was greater for pectin than for starch treatment (P<0.01) with low or high RDP. A NFC × RDP interaction was observed for neutral detergent fibre disappearance (P=0.01), which was lower for pectin than for starch only under low RDP conditions. Compared with starch, pectin treatment increased the copy numbers of Ruminococcus albus (P≤0.01) and Ruminococcus flavefaciens (P≤0.09), the molar proportion of acetate (P<0.01), the acetate:propionate ratio (P<0.01), and methane production (P<0.01), but reduced the propionate proportion (P<0.01). Increasing dietary RDP increased the production of total VFA (P=0.01), methane (P<0.01), ammonia N (P<0.01), and microbial N (P<0.01). Significant NFC × RDP interaction and interaction tendency were observed for ammonia N production (P=0.01) and daily N flow of total microorganisms (P=0.07), which did not differ under low RDP conditions, but pectin produced greater microbial N and less ammonia N than starch with increased RDP. Results showed NFC type, RDP level, and their interaction affected ruminal fermentation and microbial growth, and under sufficient ruminal degradable N pectin had greater advantage in microbial N synthesis than starch in vitro.

Interaction between Live Yeast and Dietary Rumen Degradable Protein Level: Effects on Diet Utilization in Early-Lactating Dairy Cows

Four early lactating Holstein cows were used to study the effect of live yeast (LY, Actisaf® CNCM I-4407, Lesaffre Feed Additives, Marcq en Baroeul, France) supplementation on diet digestive utilization of dairy cows receiving concentrated corn silage-based diets with two rumen-degradable protein (RDP) levels. For a 33 d period, cows were fed a total mixed ration (TMR) containing an adequate level (AL) of RDP or a low level (LL, 30% below AL) by using soybean meal or tanned soybean meal, respectively: for 21 d with no LY addition followed by 12 d during which LY was added to the diet. The pH and redox potential (Eh) were recorded and ruminal fluid samples were collected over 3 consecutive days. Feces were collected individually over 48 h and individual dry matter intake (DMI) was measured for determining apparent nutrient digestibility. The effective degradability of individual feed ingredients composing both diets was evaluated with nylon bags technique. Structure of the ruminal bacterial community was studied and diversity index was calculated. Digestibility of organic matter (OM) and crude protein (CP) were lower for LL than those for AL. With LY, digestibility of OM and CP was increased: +2.4 and +0.8 points, for AL, and +3.7 and +5.9 points for LL, respectively. Live yeast reduced dietary N ruminal degradation with both AL and LL. Ruminal pH and Eh were lower with AL compared to LL: 5.95 and –167 mV vs. 6.13 and –144 mV. Live yeast increased ruminal total volatile fatty acids (VFA) (+8.6%), C2 (+10%), and C4 (+35%) contents for LL and decreased that of C3 (?9.8%) for AL. Neither the structure of bacterial populations of the rumen nor the diversity index (Shannon) was altered by treatments. Those results suggested a specific interest in using LY in RDP deficient diets for early lactating cows.

Effects of decreasing metabolizable protein and rumen-undegradable protein on milk production and composition and blood metabolites of Holstein dairy cows in early lactation

This study was conducted to evaluate the effects of decreasing dietary protein and rumen-undegradable protein (RUP) on production performance, nitrogen retention, and nutrient digestibility in high-producing Holstein cows in early lactation. Twelve multiparous Holstein lactating cows (2 lactations; 50±7 d in milk; 47 kg/d of milk production) were used in a Latin square design with 4 treatments and 3 replicates (cows). Treatments 1 to 4 consisted of diets containing 18, 17.2, 16.4, and 15.6% crude protein (CP), respectively, with the 18% CP diet considered the control group. Rumen-degradable protein levels were constant across the treatments (approximately 10.9% on a dry matter basis), whereas RUP was gradually decreased. All diets were calculated to supply a postruminal Lys:Met ratio of about 3:1. Dietary CP had no significant effects on milk production or milk composition. In fact, 16.4% dietary CP compared with 18% dietary CP led to higher milk production; however, this effect was not significant. Feed intake was higher for 16.4% CP than for 18% CP (25.7 vs. 24.3 kg/d). Control cows had greater CP and RUP intakes, which resulted in higher concentrations of plasma urea nitrogen and milk urea nitrogen; cows receiving 16.4 and 15.6% CP, respectively, exhibited lower concentrations of milk urea nitrogen (15.2 and 15.1 vs. 17.3 mg/dL). The control diet had a significant effect on predicted urinary N. Higher CP digestibility was recorded for 18% CP compared with the other diets. Decreasing CP and RUP to 15.6 and 4.6% of dietary dry matter, respectively, had no negative effects on milk production or composition when the amounts of Lys and Met and the Lys:Met ratio were balanced. Furthermore, decreasing CP and RUP to 16.4 and 5.4%, respectively, increased dry matter intake.

Technical note: Nitrogen isotopic fractionation can be used to predict nitrogen-use efficiency in dairy cows fed temperate pasture1

The objective of this study was to investigate the relationship between nitrogen isotopic fractionation (δ(15)N) and nitrogen-use efficiency (milk nitrogen/nitrogen intake; NUE) in pasture-fed dairy cows supplemented with increasing levels of urea to mimic high rumen degradable protein pastures in spring. Fifteen cows were randomly assigned to freshly cut pasture and either supplemented with 0, 250, or 336 g urea/d. Feed, milk, and plasma were analyzed for δ(15)N, milk and plasma for urea nitrogen concentration, and plasma for ammonia concentration. Treatment effects were tested using ANOVA and relationships between variables were established by linear regression. Lower dry matter intake (P = 0.002) and milk yield (P = 0.002) occurred with the highest urea supplementation (336 g urea/d) compared with the other two treatments. There was a strong linear relationship between milk δ(15)N - feed δ(15)N and NUE: [NUE (%) = 58.9 - 10.17 × milk δ(15)N - feed δ(15)N (‰) (r(2) = 0.83, P < 0.001, SE = 1.67)] and between plasma δ(15)N - feed δ(15)N and NUE: [NUE (%) = 52.4 - 8.61 × plasma δ(15)N - feed δ(15)N (‰) (r(2) = 0.85, P < 0.001, SE = 1.56)] . This study confirmed the potential use of δ(15)N to predict NUE in cows consuming different levels of rumen degradable protein.