Microbial Protein Yield Research Articles

Effect of supplementing an α-amylase enzyme or a blend of essential oil components on the performance, nutrient digestibility, and nitrogen balance of dairy cows

Lowering dietary protein content is a promising strategy to reduce N excretions in cattle but it requires improved N utilization by the animal. Feed enzymes (e.g., exogenous α-amylase) and plant extracts (e.g., essential oils [EO]) are 2 additives that may enhance rumen function and possibly also microbial protein yield. This may increase fat- and protein-corrected milk yield (MY) and milk nitrogen efficiency and thus lower N losses from dairy cows. Both types of additives were studied in an experiment including 39 Holstein cows that had (average ± SD) 40.7 ± 7.95 kg/d MY, 89 ± 43 DIM, 2.7 ± 1.5 lactations, and 677 ± 68.6 kg of BW, consisting of a covariate (4 wk) and treatment period (5 wk). During the whole experiment cows were fed a typical Benelux diet (CTRL), supplemented with concentrates to meet individual requirements for energy and MP, which were fulfilled for 100% and 101%, respectively. The total diet was low in CP (15.5%) and relatively high in starch (22.6% and 6.6% rumen bypass starch). Cows were balanced for parity, DIM, MY, and roughage intake and randomly assigned to one of 3 groups, which received the following treatments in the treatment period: (1) CTRL (n = 13); (2) CTRL + 14 g/cow per day Ronozyme RumiStar α-amylase enzyme (AMEZ, n = 13; DSM); and (3) CTRL + 2.5 g/cow per day Crina Protect, a blend of EO components (ESOL, n = 13; DSM). Animal performance, ruminal pH, and enteric gas emissions were monitored throughout the experiment. During the last week of the covariate and treatment periods, nitrogen balances were conducted, total-tract nutrient digestibility was determined, and urinary allantoin and uric acid were determined as indicators for microbial N production. The statistical model applied to these variables contained group and DIM during treatment period as fixed effects and the values from the covariate period as covariate. Post hoc Dunnet-corrected comparisons between each treatment group and the control group were explored. The α-amylase enzyme tended to increase apparent total-tract starch digestibility and increased milk lactose concentration. The EO blend tended to increase MY and increased milk N output, milk nitrogen efficiency, and feed efficiency. Therefore, when feeding reduced dietary protein levels, EO have potential to improve the N-use efficiency in cattle, whereas the α-amylase enzyme might increase starch digestibility and milk lactose. However, additional research is necessary to substantiate our findings.

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The current experiment aimed to determine the effects of the growing site on the chemical composition and fermentation parameters of carob pods. Carob pods from ten different trees were hand harvested from seven different growing sites namely; Silifke, Akdeniz, Tarsus, Aydincik, Taşucu, Toroslar and Gülnar in Mersin, Turkey in 2019 and oven dried at 50°C for three days. After drying, the carob pods were ground through a 1 mm-wide sieve for analysis and in vitro gas production (GP) testing. The growing site had a significant effect on the chemical composition, GP, and digestion values of carob pods. The crude ash (CA), crude protein (CP), ether extracts (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF), and condensed tannin (CT) contents of carob pods ranged from 2.49 to 3.51%, 5.58 to 9.14%, 2.88 to 3.38%, 17.67 to 28.03%, 11.17 to 17.94%, and 1.98 to 5.05%, respectively. The GP, methane (CH4 (mL), percentage of CH4, metabolizable energy (ME), and organic matter digestibility (OMD) ranged from 95.66 to 123.0 mL g-1 DM, 16.23 to 20.12 mL g-1 DM, 15.69 to 16.96%, 8.24 to 9.72 MJ kg-1 DM, and 54.53 to 63.40%, respectively. The GP, CH4 production, and ME contents of carob pods obtained from Silifke, Akdeniz, Tarsus, and Tasucu were significantly higher than those from the other growing sites, whereas the OMD of carob pods from Silifke and Tarsus was significantly higher than that from the other sites. The true digestible substrate (TDS), microbial protein yield (MPY), efficiency of microbial protein yield (EMPY), and true substrate digestibility (TSD) of carob pods ranged from 319.54 to 469.62 mg, 109.07 to 207.09 mg, 32.34 to 44.10%, and 68.43 to 96.11%, respectively. The TDS, MPY, EMPY, and TSD of carob pods from Tasucu were significantly higher than those from the other sites. The current study revealed valuable insight regarding the chemical composition and fermentation parameters of carob pods grown at different sites. Carop pods can be used in sheep diets to meet the energy requirement of mature sheep for maintenance and lactation whereas protein supplementation is essential when incorporating carob pods into the diets of lactating sheep to fulfill their dietary requirements.

Fermented cottonseed and rapeseed meals outperform soybean meal in improving performance, rumen fermentation, and bacterial composition in Hu sheep.

This study examined the effects of substituting cottonseed meal (CSM) or rapeseed meal (RSM) for soybean meal (SBM) on Hu sheep performance, rumen fermentation, and bacterial composition. 51 four-month-old indigenous male Hu sheep with starting body weights of 22.51 ± 2.84 kg and similar origins were randomly assigned to three treatments; (1) non-fermented total mixed ration (TMR) with SBM (CK), (2) fermented TMR containing CSM (F-CSM group), and (3) fermented TMR containing RSM (F-RSM group). The three groups' intake of dry matter differed significantly (p < 0.05). In terms of average daily gain, the F-RSM group outperformed the CK and F-CSM groups (p < 0.05). The pH of the rumen was substantially lower in the CK group than in the F-CSM and F-RSM groups (p < 0.05), and the F-CSM group had greater amounts of volatile fatty acids (VFA) than the F-RSM and CK groups. In comparison to the CK group, the microbial crude protein yield was significantly higher in the F-CSM and F-RSM groups (p < 0.05). The F-CSM group significantly outperformed the F-RSM group of pepsin and cellulose enzyme activity (p < 0.05). The relative abundance of Bacteroidetes was greater in the CK and F-RSM groups compared to the F-CSM group (p < 0.05). In comparison to the other groups, Firmicutes were less abundant in the CK group (p < 0.05). Prevotella was present in a higher relative abundance in the F-CSM and F-RSM groups than in the CK group (p < 0.05). Prevotella was greater in relative abundance in the F-CSM and F-RSM groups than in the CK group (p < 0.05). The relative abundances of Veillonellaceae_UCG-001 and Lachnospiraceae_XPB1014 correlated with rumen butyric acid content and NH3-N content (p < 0.05). Gene function prediction revealed that replacing SBM with F-CSM or F-RSM in the diet of Hu sheep can promote glycan biosynthesis and metabolism. The replacement of F-CSM and F-RSM for SBM has an influence on the richness and diversity of rumen bacteria at the phylum and genus levels. Replacement of SBM with F-CSM increased VFA yield and further promoted the performance of Hu sheep.

Evaluating the Effects of Some Selected Medicinal Plant Extracts on Feed Degradability, Microbial Protein Yield, and Total Gas Production In Vitro

This study evaluates the effect of 22 crude ethanolic plant extracts on in vitro rumen fermentation of Themeda triandra hay using monensin sodium as a positive control. The experiment was run independently three times at 16 and 48 h of incubation periods using the in vitro gas production techniques. Fermentation parameters were determined at both hours of incubation. Plant extracts influenced gas production (GP) in a varied way relative to control at both hours of incubation, and GP is consistently highly significant (p < 0.0001) at 16 and 48 h. Microbial protein yield (MY) was not significantly affected at 16 h (p > 0.05), but it was at 48 h (p < 0.01). Higher MY was recorded for all treatments except for A. sativum and C. intybus at the early incubation stage (16 h) relative to 48 h of incubation. Compared to the control group at 48 h, all plant extracts have higher MY. After 48 h of incubation, the result shows that plant extracts have an effect on fermentation parameters determined; ruminal feed degradation, gas production, microbial protein yield, and partitioning factor in varied manners. All the plant extracts improve the MY which is the major source of amino acids to ruminants and has significant importance to animal performance. C. illinoinensis, C. japonica, M. nigra, P. americana, C. papaya, and A. nilotica (pods) were the most promising plant extracts, but further study is recommended to validate the in vitro observation in vivo.

Effects of linseed oil supplementation in Holstein dairy calves received starters based on either corn or barley grain on growth performance and immune response.

This study evaluated the effects of linseed oil (LO) and two-grain sources on growth performance, microbial protein yield (MPY), blood metabolites, and inflammatory markers in Holstein dairy calves. Forty-eight 3-day-old dairy calves (24 males and 24 females) with starting BW of 40.3 ± 1.6 kg were allocated in a completely randomised block design with a 2 × 2 factorial arrangement as follows; (1) Corn grain (CG) with no LO supplementation (CG-NLO), (2) CG with 2.5% LO supplementation (CG-LO), (3) Barley grain (BG) with no LO supplementation (BG-NLO), and (4) BG with 2.5% LO supplementation (BG-LO). The calves were weaned on d 59 but the study lasted for 14 days after weaning (Day 73 of experiment). The results showed that starter feed intake was influenced neither by grain source nor linseed oil. However, average daily gain, BW, hip height, and MPY were improved in calves received BG compared to CG diets. Linseed oil supplementation had no significant effects on growth performance and MPY. During preweaning period, calves fed BG-LO had the greatest feed efficiency and the highest wither height. However, the greatest tumour necrosis factor and serum amyloid A were observed in BG-NLO. Despite, LO supplementation did not influence growth performance of animals per se; however, it reduced circulating inflammatory markers in calves during preweaning period. Based on this study condition, BG is more favourable than CG in dairy calves from the daily gain and microbial protein synthesis perspectives, and supplementing the starters with n-3 FA can be strategy to improve immune performance of calves fed barley-based starter diets.

Integrating Microbial Protein Production and Harvest Systems into Pilot-Scale Recirculating Aquaculture Systems for Sustainable Resource Recovery: Linking Nitrogen Recovery to Microbial Communities.

In aquaculture, it is important to raise the nitrogen recovery efficiency (NRE) to improve sustainability. To achieve this, recovery of microbial protein (RMP), instead of nitrification/denitrification in conventional wastewater treatment, is a promising approach whose microbiological mechanisms must be characterized. Here, periodic RMP was conducted in an in situ biofloc-based aquaculture system (IBAS) and a separating assimilation reactor-based recirculating aquaculture system (SRAS). Kinetic analysis indicated that a microbial biomass level of 3 g L-1 was optimal for inorganic N removal, and excess biomass was harvested to improve the NRE. Unlike the IBAS, the SRAS eliminated the fluctuation in water quality caused by the RMP. Periodic RMP significantly increased the NRE to 44-57% by promoting the filamentous bacterium Herpetosiphon and suppressing anaerobic denitrifiers. Aerobic chemoheterotrophy was the main microbial metabolic process for energy. After RMP, nitrate reductase-encoded functional genes (napA and narG) significantly decreased, while nitrite reductase-encoded functional genes, especially nirK, significantly increased. Co-occurrence networks analysis indicated that the cooperation and competition among organic matter degraders, filamentous bacteria, nitrifiers, and denitrifiers determined the microbial protein yield. These results provide fundamental insights into the influence of the RMP on microbial communities and functions, which is important for realizing sustainable aquaculture.

Forage source (alfalfa hay vs wheat straw) and rumen undegradable to degradable protein ratio: Effects on growth performance, microbial protein yield, digestibility, blood metabolites, and behavior of Holstein dairy calves

Aim of the study: The effects of forage source (alfalfa hay; AH vs. wheat straw; WS) with rumen undegradable to degradable protein ratio [low ratio (LR) = 28:72; high ratio (HR) = 36:64] were evaluated in young dairy calves.Area of study: Arak, Iran.Material and methods: Forty-eight 3-d old female Holstein dairy calves (44.5 kg of BW) were allocated in four treatments: (1) AH with low dietary RUP:RDP ratio (AH-LR); (2) AH with high dietary RUP:RDP ratio (AH-HR); (3) WS with low dietary RUP:RDP ratio (WS-LR); and (4) WS with high dietary RUP:RDP ratio (WS-HR), being RDP and RUP rumen degradable and undegradable proteins, respectively. The calves weaned on d 53 of the experiment and remained in the study until d 73 of age.Main results: The average daily gain and feed efficiency were improved in dairy calves receiving HR diets compared to LR diets during the post-weaning period (p&lt;0.05). The fecal score (p=0.03) and neutral detergent fiber digestibility (p=0.04) were improved when calves fed WS diets compared to AH diets. Feeding HR diets increased allantoin (p=0.04) and microbial protein yield, and reduced blood urea nitrogen concentration (p=0.03) compared to LR diets. Assessing the interaction effects of the experimental factors resulted that the greatest BW, wither height, and blood beta-hydroxybutyrate, and the lowest urinary N concentration were observed in the WS-HR treatment (p&lt;0.05).Research highlights: Feeding WS with high RUP:RDP ratio is recommendable in dairy calves due to the improvement in gain and N efficiency.

Effects of inclusion different level of low-quality forage and ruminal undegradable protein to degradable protein ratio in starter diet on growth performance, ruminal fermentation, and urinary purine derivatives in young lambs

Forty 12-day-old lambs with an average BW of 6.37 kg were allocated in a completely randomized design with a 2 × 2 factorial arrangement to evaluate the effects of wheat straw feeding level (WS; 10% vs. 25%, DM basis) and rumen undegradable to degradable protein ratio [RUP:RDP; low ratio (LR) = 27:73; high ratio (HR) = 38:62] on growth performance, nutrient digestibility, ruminal fermentation, microbial protein yield (MPY), blood metabolites, and liver enzymes. Treatments (10 lambs/each; 5 males and 5 females) were: (1) 10% WS with low RUP:RDP ratio (10WS-LR); (2) 10% WS with high RUP:RDP ratio (10WS-HR); (3) 25% WS with low RUP:RDP ratio (25WS-LR); and (4) 25% WS with high RUP:RDP ratio (25WS-HR). Lambs were weaned on d 82 of the experiment and remained in the study until d 92. Lambs had free access to starter diet throughout the experiment. Results show that starter intake, average daily gain, and feed efficiency did not change among experimental treatments. Organic matter digestibility was reduced in 25WS diets. Greater organic matter digestibility, fibre digestibility (tendency; p = 0.064), wither height (d 82), and urinary allantoin was found in HR compared to LR diets. However, ruminal NH3-N concentration and urinary nitrogen excretion was greater in LR diets indicating lower nitrogen utilization efficiency. The greatest ruminal butyrate concentration as well as the greatest concentration of blood beta-hydroxybutyrate was found for 25WS-HR diet at d 90 of experiment. The blood urea concentration was reduced in HR diets compared to LR diets. In summary, high RUP:RDP ratio is advisable when young lambs received high level of WS in starter diet due to improve nutrient digestibility and nitrogen efficiency.

Studies on Microbial Quality, Protein Yield, and Antioxidant Properties of Some Frozen Edible Insects.

This research investigated the microbial quality and the protein contents of Thai commercial frozen products of silkworm (Bombyx mori), bamboo caterpillar (Omphisa fuscidentalis), and field cricket (Gryllus bimaculatus). Total mesophilic aerobic counts were about 8-8.4 log cfu/g, while lactic acid bacteria numbers were up to 5.2 log cfu/g samples. Yeasts and mold as well as Enterobacteriaceae numbers were found to be no more than 6.3 and 6.6 log cfu/g, respectively, while Clostridium spp. enumeration detected 3.2-3.6 cfu per gram frozen insect samples. The protein content in cases of cricket and bamboo caterpillar after the Soxhlet defatting method and the Folch lipid extraction combined with isoelectric point precipitation were similar when compared at pH 3.5 or pH 4.5. In contrast, the protein yield from silkworm was higher at pH 3.5 in the Soxhlet defatted sample, as opposed to the Folch method treated sample where higher protein yield was obtained at pH 4.5. Furthermore, 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP) of field cricket subcritical water (121 or 135°C for 15 or 30 minutes) hydrolysates were also measured on a pilot basis. These tests revealed higher antioxidant activities in treated samples than in the untreated control. The highest DPPH radical scavenging activity and FRAP values were detected in samples treated at 135°C, while the protein content of these samples was lower than that of the untreated control. These results indicate that hydrolytic compounds of proteins and probably other types of cricket materials are possibly involved in the antioxidant activities of the treated defatted cricket samples.

Effects of linseed processing method (ground versus extruded) and dietary crude protein content on performance, digestibility, ruminal fermentation pattern, and rumen protozoa population in growing lambs

Thirty-six male lambs (averaging BW = 24.4 kg) were assigned in a completely randomised design with the factorial arrangement (nine lambs per each treatment) to assess the effects of linseed processing method (ground vs. extruded) and dietary crude protein content (12% vs. 15%, DM basis) on performance, digestibility, ruminal fermentation, and protozoa population. Treatments were; (1) ground linseed with 12% CP (GLS-12CP), (2) ground linseed with 15% CP (GLS-15CP), (3) extruded linseed with 12% CP (ELS-12CP), and (4) extruded linseed with 15% CP (ELS-15CP). The study lasted 84 d, and the lambs had free access to experimental diets and water. Outcomes showed that dry matter intake, digestibility of organic matter, and crude protein were increased in lambs fed ground linseed compared to extruded linseed. Feeding extruded linseed decreased urinary allantoin concentration, total purine derivatives (PD), the ruminal proportion of propionate, and blood concentration of glucose and HDL-cholesterol compared to ground linseed diets. Regarding dietary protein content, results showed that dry matter intake, urinary concentration of allantoin and total PD were increased in 15CP diets compared to 12CP diets. Considering the interaction, results showed that average daily gain was improved in GLS-15CP treatment compared to other experimental treatments. In conclusion, results show that grinding the linseed is more beneficial compared to its extrusion in lamb nutrition. Moreover, 15CP diets had a beneficial effect when fed with either ground or extruded linseed and seem to compensate, to some extent, the negative effects of extruded linseed on the gain of growing lambs. Highlights Linseed processing methods (ground vs. extruded) and dietary protein content (12 vs. 15%, DM basis) were evaluated in growing lambs Ground linseed increased average daily gain, improved digestibility, and microbial protein yield compared to extruded linseed Ground linseed was more favourable than extruded linseed and 15% CP diet has additional advantages either with the ground or extruded linseed

Nutritive value of ensiled Italian ryegrass and winter cereal mixture

Nutritive value of ensiled Italian ryegrass and winter cereal mixture

The effects of supplementing sweet sorghum with grapeseeds on dry matter intake, average daily gain, feed digestibility and rumen parameters and microbiota in lambs

This study examined the effect of supplementing sweet sorghum with grapeseeds on dry matter intake, average daily gain, feed digestibility and rumen parameters and microbiota in small-tailed Han lambs. A total of 28 lambs (19.1±1.20 kg) were divided randomly into four dietary treatment groups and received alfalfa silage (1% BW on DM basis) and concentrate feed (2% BW on DM basis) plus: 1) sweet sorghum silage (SS); 2) sweet sorghum silage + grapeseeds (SSG); 3) sweet sorghum hay (SH); and 4) sweet sorghum hay + grapeseeds (SHG). Sweet sorghum silage and hay were offered ad libitum and grapeseeds, when offered, were added at 6% DM of concentrate feed, which was equivalent to approximately 2.7 % of total DMI. Grapeseeds did not affect DMI, but DMI of the silage groups were higher than the hay groups (P<0.05) and the ADG of SSG was higher than SH (P<0.05). Grapeseeds had no effect on rumen microbial protein yield, efficiency of microbial protein synthesis and excretion of urine purine derivatives. The SSG group had lower rumen fluid pH and acetate:propionate ratio but higher concentrations of total VFAs, acetate, propionate, butyrate, isovaleric acid and valerate than the other three groups (P<0.05). Supplementary grapeseeds did not affect ruminal bacteria diversity, but increased the relative abundance of Bacteroidetes and Prevotella_1 (P<0.01) and decreased Firmicutes (P<0.05). It was concluded that there was an increase in total VFAs and the relative abundances of ruminal bacteria were altered in lambs when sweet sorghum was supplemented with grapeseeds to the diet.

Effects of Ca-salt of linseed oil supplementation and protein content in diet on performance, ruminal fermentation, microbial protein yield, and blood metabolites in young lambs

To study the effect of Ca-salt of linseed oil (Ca-LSO) supplementation in diets with varying protein content, thirty-six 12-day-old Farahani lambs with an average BW of 8.9 kg were used in a completely randomized block design with a 2 × 2 factorial arrangement as follows: (1) no Ca-salt of linseed oil supplementation and 18 % CP (NLSO-18CP); (2) no Ca-salt of linseed oil supplementation and 21 % CP (NLSO-21CP); (3) starter diet supplemented with Ca-salt of linseed oil and 18 % CP (LSO-18CP); (4) starter diet supplemented with Ca-salt of linseed oil and 21 % CP (LSO-21CP). All lambs were weaned on d 72 but remained in the study until d 92 of age. The results showed that starter intake was similar among the experimental treatments; however, feed efficiency (FE) was improved in lambs supplemented with Ca-LSO during the post-weaning period. Higher concentrations of blood glucose, HDL-cholesterol, and insulin were found in the lambs supplemented with Ca-LSO. The 21CP diets improved FE (tendency) in the post-weaning period. The higher protein content in the starter diet increased ruminal concentrations of branched-chain fatty acid (d 45), ruminal NH3-N concentration (d 90), and improved MPY compared to the 18CP diets. Regarding the interaction effects between Ca-LSO supplementation and starter protein content, there was a higher average daily gain, body weight, and blood insulin concentration (d 46) for the LSO-21CP treatment (P < 0.05). In contrast, the greater blood urea nitrogen concentration (d 46) and urinary N excretion were observed in the NLSO-21CP treatment (P < 0.05). In conclusion, under the conditions of the present experiment, results showed that supplementation of the Ca-LSO with 21CP improved growth performance in lambs reared on an indoor feeding system, which can be attributable to improved N efficiency.

Effectiveness of feed nitrogen use depending on the level of raw protein and the ratio of protein fractions in the rations of cows

Protein nutrition of ruminants as well as other animal species, should be considered as an amino acid nutrition, since not protein as such, but amino acids are the main material for the synthesis of milk proteins, tissues, enzymes, many hormones, neuropeptides and others that play an important role in ensuring the vital functions of the body. Studying the eff ects of diff erent levels of DPR and ratios UPR:DPR with diff erent content of raw protein in rations for nitrogen metabolism, eff ectiveness of feed protein use and dairy productivity of cows is of great scientifi c and practical importance. The purpose of the researches was to determine the optimal levels of undigested protein in rumen (UPR) and digested protein in rumen (DPR) and to determine the possibility of reducing protein consumption in the rations of high-yielding Holstein cows during the early lactation period. It has been found that in rations with 15,7 % crude protein (CP) the optimal ratio was UPR:DPR = 35:65 (UPR – 5,44 %, DPR – 10,3 % DM), which has been confi rmed by the more active formation of free lysine and methionine in the rumen, the yield of microbial protein, higher coeffi cients of digestibility of dry matter, nitrogen, fi ber, higher yield of lysine and methionine in the duodenal chyme, as well as the lowest losses of protein consumed in the process of rumen digestion. Dairy productivity of cows on this ration was at the level of that of cows on rations with 17,7 % CP – 38,7 kg/day when it contains 3,72 % fat and 3,27 % protein. On the ration with the same CP content (15,7 %), but the ratio of UPR:DPR = 50:50 there was a signifi cant decrease in feed consumption (P &lt; 0,01) and the decrease in dairy productivity of cows, which was probably due to the low level of formation of ammonium nitrogen NH3 -N in the rumen.

Effects of corn grain processing method (ground versus steam-flaked) with rumen undegradable to degradable protein ratio on growth performance, ruminal fermentation, and microbial protein yield in Holstein dairy calves

The hypothesis of the current study was that steam-flaking corn grain will increase ruminal available starch, but reduce undegradable protein reaching the small intestine and hence formulating the starter diet with higher undegradable protein content may influence dairy calf performance. The effects of corn processing method (ground corn grain; GC vs. steam-flaked corn grain; SFC) with rumen undegradable to degradable protein ratios [low ratio (LR) = 28:72; high ratio (HR) = 37:63 based on %CP] on growth performance, feeding behavior, nutrients digestibility, ruminal fermentation, urinary purine derivatives and blood metabolites of Holstein dairy calves were evaluated. Forty-eight 3-day-old calves (24 females and 24 males) with a starting BW of 39.5 kg were used in a completely randomized block design with a 2 × 2 factorial arrangement of treatments. Experimental treatments were: (1) ground corn with low RUP:RDP (GC-LR); (2) ground grain with high RUP:RDP (GC-HR); (3) steam-flaked corn with low RUP:RDP (SFC-LR); and (4) steam-flaked corn with high RUP:RDP (SFC-HR). All calves were weaned on d 63 of age and, remained in the study until d 83 to take final measurements. Starter intake was not influenced by the grain processing method nor by dietary RUP:RDP ratio; however, the average daily gain and feed efficiency were improved and final body weight was higher in SFC fed calves. Feeding SFC diet improved the faecal score, increased the time spent on eating and slightly increased ruminating time. The LR diet improved neutral detergent fiber digestibility. Greater ruminal concentrations for total short-chain fatty acids, propionate, and butyrate were obtained when calves fed on SFC diet in pre-weaning period. The greatest heights for both wither and hip among experimental treatments were obtained in SFC-HR treatment. The higher urinary allantoin excretion and microbial protein yield, and lower urinary nitrogen excretion on the other hand, reflected an improved nitrogen efficiency in the SFC diet compared to the GC diet. Blood concentrations for glucose, beta-hydroxybutyrate and insulin were higher, and blood urea nitrogen concentration was lower in calves fed on SFC diet. In conclusion, considering our experimental condition, feeding steam-flaked corn in starter diet of dairy calves is favourable compared to ground corn grain, but RUP:RDP ratio did not influence animal performance per se. Skeletal growth was improved when SFC was fed with greater RUP:RDP ratio in starter diet which may be recommendable in replacement heifer rearing programs.

Microbial protein formation of different carbohydrates in vitro.

The aim of this study was to investigate the microbial protein yield of different pure carbohydrates to contribute to a more precise prediction of the microbial protein formed in the rumen. In a first experiment, sucrose, wheat starch, microcrystalline cellulose and citrus pectin were incubated for 8 and 24hr in the modified Hohenheim gas test (HGT) system (3 runs×2 syringes) including gas production, ammonia and short-chain fatty acid concentration measurements. Ammonia values were used for estimation of the microbial protein formation. In a second experiment, the same substrates were incubated for 96hr in the HGT system (2 runs×3 syringes) and gas production was measured after 2, 4, 6, 8, 12, 16, 24, 30, 36, 48, 60, 72 and 96hr of incubation to obtain the fermentation kinetics and the time of half-maximal gas production (t1/2 ) of the substrates. The substrates differed considerably in their fermentation kinetics, and therefore, comparison on the basis of t1/2 was chosen as the most meaningful. At t1/2 , microbial protein yield [g/kg dry matter] was higher for cellulose than for sucrose and pectin and higher for starch than for sucrose. The microbial protein expressed in g/L gas production was higher for starch and cellulose than for sucrose and pectin at t1/2 . Effects of carbohydrates related to ruminal pH may remain undetected in in vitro trials.

Dietary Energy Level Promotes Rumen Microbial Protein Synthesis by Improving the Energy Productivity of the Ruminal Microbiome.

Improving the yield of rumen microbial protein (MCP) has significant importance in the promotion of animal performance and the reduction of protein feed waste. The amount of energy supplied to rumen microorganisms is an important factor affecting the amount of protein nitrogen incorporated into rumen MCP. Substrate-level phosphorylation (SLP) and electron transport phosphorylation (ETP) are two major mechanisms of energy generation within microbial cells. However, the way that energy and protein levels in the diet impact the energy productivity of the ruminal microbiome and, thereafter, rumen MCP yields is not known yet. In present study, we have investigated, by animal experiments and metagenome shotgun sequencing, the effects of energy-rich and protein-rich diets on rumen MCP yields, as well as SLP-coupled and ETP-coupled energy productivity of the ruminal microbiome. We have found that an energy-rich diet induces a significant increase in rumen MCP yield, whereas a protein-rich diet has no significant impacts on it. Based on 10 reconstructed pathways related to the energy metabolism of the ruminal microbiome, we have determined that the energy-rich diet induces significant increases in the total abundance of SLP enzymes coupled to the nicotinamide adenine dinucleotide (NADH) oxidation in the glucose fermentation and F-type ATPase of the electron transporter chain, whereas the protein-rich diet has no significant impact in the abundance of these enzymes. At the species level, the energy-rich diet induces significant increases in the total abundance of 15 ETP-related genera and 40 genera that have SLP-coupled fermentation pathways, whereas the protein-rich diet has no significant impact on the total abundance of these genera. Our results suggest that an increase in dietary energy levels promotes rumen energy productivity and MCP yield by improving levels of ETP and SLP coupled to glucose fermentation in the ruminal microbiome. But, an increase in dietary protein level has no such effects.

Factors affecting the ruminal microbial composition and methods to determine microbial protein yield. Review

Microbial protein synthesized in the rumen is a major contributor of metabolizable protein. Thus, accurate estimation of microbial protein is essential in ruminant nutrition. The objective of this review is to describe the microbial composition, major factors affecting its yield and methods to estimate microbial protein flow to the intestine. The use of novel molecular techniques to elucidate the ruminal microbiome and improve methods for estimating microbial protein are discussed. Bacteria, protozoa, fungi and archaea compose the ruminal microbiome. Main factors affecting microbial protein synthesis are availability of carbohydrates, ruminally degradable protein, dietary fat, and ruminal pH. Major microbial markers used to estimate microbial protein synthesis are total purines, diaminopimelic acid and labeled nitrogen; in addition, DNA through real-time PCR is being tested for the estimation of bacterial, protozoal and yeast protein separately. The main difficulty in the estimation of microbial protein flow is obtaining representative microbial pellets from the rumen, which are used as reference to establish the ratio of marker/nitrogen. Detailed phylogenetic analysis using High-throughput DNA sequencing has recently revealed drastic taxonomic differences between fluid-associated bacteria and bacteria from whole intestinal digesta contents. For example, ruminal fluid contains less Fibrobacteres and Proteobacteria, but more Firmicutes compared to whole intestinal digesta. This demonstrates the need of developing effective bacterial collection procedures for obtaining representative ruminal microbial reference pellets to prevent bias on the estimation of the contribution of microbial protein to the intestinal supply of metabolizable protein.

Effects of tributyrin supplementation on ruminal microbial protein yield, fermentation characteristics and nutrients degradability in adult Small Tail ewes.

Two trials were conducted to assess the effects of tributyrin (TB) supplementation on ruminal microbial protein yield and fermentation characteristics in adult sheep. In an invitro trial, substrate was made to offer TB at 0, 2, 4, 6, and 8g/kg on a dry matter (DM) basis and incubated for 48hr. In an invivo trial, 45 adult ewes were randomly assigned by initial body weight (55±5kg) to five treatments of nine animals over an 18-day period. Total mixed ration was made to offer TB to ewes at 0, 2, 4, 6, and 8g/kg on a DM basis. The invitro trial showed that TB enhanced apparent degradation of DM (p=.009), crude protein (p<.001), neutral detergent fiber (p=.007) and acid detergent fiber (p=.010) and increased methanogenesis (p<.001), respectively. The invivo trial showed that TB decreased DM intake (p<.001) and enhanced rumen microbial N synthesis (p<.001), respectively. Both invitro and invivo trials showed that TB increased total volatile fatty acid concentration and enhanced fibrolytic enzyme activity. The results indicated that TB might exert positive effects on microbial protein yield and fermentation in the rumen.

Influence of supplementing a methionine derivative, N-acetyl-l-methionine, in dairy diets on production and ruminal fermentation by lactating cows during early to mid lactation

The present study investigated production responses and ruminal fermentation characteristics of lactating dairy cows when supplemented with N-acetyl-l-Met (NALM) as a source of rumen-protected Met in metabolizable protein (MP)-deficient (MPD) or MP-adequate diet (MPA). Eight lactating dairy cows (53 ± 10.4 d in milk, average ± standard deviation) were blocked by parity and days in milk, and the experiment was performed in a replicated 4 × 4 Latin square design. Within each square, cows were randomly assigned to a sequence of 4 diets during each of the four 21-d periods (14 d of treatment adaptation and 7 d of data collection and sampling). A 2 × 2 factorial arrangement was used; MPD or MPA was combined without or with NALM: MPD without NALM, MPD with NALM (MPD+NALM), MPA without NALM, and MPA with NALM (MPA+NALM). A NALM product was supplemented in the MPD+NALM and the MPA+NALM at 30 g/cow per d. Supplementation of NALM did not affect dry matter intake (DMI) and milk yield regardless of MP concentration. In addition, supplementing NALM resulted in a similar milk true protein concentration and yield. In contrast, NALM supplementation increased milk fat concentration and yield and 3.5% fat-corrected milk yield and tended to increase energy-corrected milk yield regardless of MP difference. Additionally, trends were observed for increased 3.5% fat-corrected milk yield/DMI and energy-corrected milk yield/DMI, and the positive effects were greater under the MPA than the MPD diet, resulting in trends toward interactions between MP and NALM. Dietary treatments had similar effects on ruminal fermentation characteristics and microbial protein yield. Plasma concentration of Met increased under the MPD but not the MPA diet, leading to an MP × NALM interaction. Overall results in the current study suggest that NALM exerted a minor influence on ruminal metabolism, but increased milk fat concentration, resulting in increases in milk fat yield and feed efficiency. Yet, potential effects of NALM on intermediary metabolism between the gastrointestinal tract, the liver, and the mammary gland need to be explored to understand utilization efficiency for production of dairy cows.