Microbial Protein Yield Research Articles

Effect of phytosterols on rumen fermentation in vitro.

We investigated the effect of phytosterols on rumen fermentation in vitro using gas syringes as incubators. Phytosterols were dissolved in ethyl acetate (8.3%) and added at various concentrations to the common diet in rumen fluid. In vitro gas production (GP) was recorded after 3, 6, 12, 18, and 24 h incubation. Incubation was stopped at 6, 12, and 24 h and the inoculants were then tested for pH, dry matter digestibility (DMD), microbial protein yield (MCP), lactic acid, NH3-N, and volatile fatty acids (VFAs). GP was consistently higher than the control; particularly, treatments at 12, 18, and 24 h reached extremely significant levels (P < 0.01). Compared to the control group, the pH of ruminal fluid was slightly lower after incubation, and DMD and MCP increased with increasing phytosterol level except for the content of MCP at 6 h, which changed only minimally. Lactate was significantly lower after treatment compared to the control at 12 h (P < 0.01) and 24 h (P < 0.05), while NH3-N at 12 h (P < 0.05) and 24 h (P < 0.01) after treatment decreased significantly. Acetate, propionate, butyrate, and total VFA for all treatments were higher than those of the control, particularly for butyrate at 6 h (P < 0.01). These results suggest that phytosterols modify rumen fermentation by inhibiting released harmful products and promoting the release of beneficial product, which may be useful for improving nutrient utilization and animal health.

Rumen microbes and microbial protein synthesis in Thai native beef cattle fed with feed blocks supplemented with a urea–calcium sulphate mixture

The influence ofslow-release urea (urea–calcium sulphate mixture; U–CaS) in feed blocks on rumen micro-organisms, predominant cellulolytic bacteria, microbial protein synthesis and ecology was studied in Thai native beef cattle. Four animals with an initial body weight of 100 ± 3.0 kg were randomly assigned to a 4 × 4 Latin square design with four dietary treatments (U–CaS in iso-nitrogen feed blocks at 0, 120, 150 and 180 g/kg dry matter (DM), respectively; U–CaS replaced urea). After 21 days of experimental feeding, rumen fluid was collected at 0 and 4 h after feeding. The mean intake of feed blocks and other feedstuffs offered (rice straw and concentrates) amounted to 0.3, 2.3 and 0.6 kg DM/day, respectively. Inclusion of U–CaS did not altered pH and temperature in the rumen. However, ruminal NH3–N concentration decreased quadratically (p < 0.05) in response to U–CaS inclusion, with the lowest value at 180 g U–CaS per kg feed block. With inclusion of U–CaS, the populations of rumen bacteria increased quadratically (p < 0.05) and counts of fungal zoospores were linearly enhanced (p < 0.05), being highest at 180 g U–CaS per kg feed block. Supplementation of U–CaS increased the concentration of total bacteria linearly (p < 0.05) and of Fibrobacter succinogenes quadratically (p < 0.05), whereas Ruminococcus flavefaciens and Ruminococcus albus were not affected by dietary treatments. Microbial crude protein yield and efficiency of microbial nitrogen (N) synthesis were linearly increased with different levels of U–CaS addition. Furthermore, current data clearly indicate that inclusion of U–CaS in feed blocks can affect micro-organism diversity and major cellulolytic bacteria.

Nutrient digestion, ruminal fermentation and performance of dairy cows fed pomegranate peel extract

An experiment was carried out to determine the effect of pomegranate peel extract (PPE) on nutrient digestion, ruminal fermentation characteristics, protozoal population and performance of dairy cows. Four Holstein cows were used in a 4×4 Latin square design with 28-d periods and 4 treatments: PPE0 (no extract), PPE400 (400ml PPE/cow/d), PPE800 (800ml PPE/cow/d) and PPE1200 (1200ml PPE/cow/d). Intake of dry matter, milk yield, and digestibility of dry matter, organic matter, crude protein, neutral detergent fiber and acid detergent fiber were measured. Ruminal fermentation characteristics such as ruminal pH, concentration of NH3–N, concentration of VFA, molar proportions of individual VFA, protozoa population and microbial N were also measured. Milk production, 4% FCM yield, milk fat and protein yield (kg/d), and milk efficiency were increased by inclusion of PPE800 in the diet. Percent of milk fat, true protein, and lactose were not affected by PPE supplementation. However, inclusion of PPE decreased NH3–N, total protozoal population, genus Isotricha and Entodinium, but increased microbial N production (g/d). Concentrations of total VFA and molar proportions of individual VFA were not affected by inclusion of PPE in the diet. The results suggested that PPE supplementation has reduced protozoa population, NH3-Nconcentration, and increased microbial protein and milk yield and quality.

Effect of dietary polymer-coated urea and sodium bentonite on digestibility, rumen fermentation, and microbial protein yield in sheep fed high levels of corn stalk

Four ruminally cannulated thin-tailed Han×Dorper crossbreed wethers were used in a 4×4 Latin square design experiment to evaluate the effect of polymer-coated urea (PCU) (Optigen II, Alltech Inc., Nicholasville, KY) and sodium bentonite (SB) on intake, nutrient digestibility, nitrogen retention, rumen fermentation and microbial nitrogen in sheep fed high levels of corn stalk. Four isonitrogenous and isocaloric dietary treatments composed of 60% corn stalk and 40% concentrate (DM basis) were offered twice daily in two equal portions at 7:00 and 19:00 h ad libitum to ensure about 5% ort. The treatments were control (CON), PCU (soybean meal replaced by 1.8% Optigen), SB (CON diet with an additional 2% SB), and PCUSB (PCU diet with an additional 2% SB). Sheep on PCU treatment showed a greater OM digestibility (P<0.05), and nitrogen digestibility (P<0.01) compared to other treatments, but digestibility of other nutrients and dry matter intake (DMI) did not change. SB did not alter nutrient digestibility except for nitrogen. Different treatments did not affect nitrogen intake, or its urinary excretion. Nitrogen retention tended to be higher (P=0.09) in sheep fed Optigen. Moreover, purine derivatives (PD) and microbial nitrogen were not influenced by different treatments. The pH and total VFA were also not influenced by the treatments. Propionate proportions increased (P<0.01) in diets that included Optigen, but an addition of SB to Optigen did not alter the ratios. NH3–N levels in PCU continuously increased, with the highest level achieved 3h after feeding, which were sustained for up to 7h. No differences were discerned in ruminal kinetics of corn stalk DM for different treatments. The PCU improved the effective degradability (ED) of corn stalk DM in 0.02 or 0.04 flow rates out of the rumen compared to both CON and PCUSB (P<0.05), but SB improved ED in 0.06 flow rates out of the rumen compared to CON. Thus, using Optigen as a new source of non-protein nitrogen to replace soybean meal in sheep fed high levels of corn stalk improved the digestibility of OM, nitrogen, and ED. Addition of SB to Optigen had no beneficial effects on nutrient digestibility, nitrogen retention, microbial nitrogen, or rumen fermentation and ED.

Effects of dietary forage sources on rumen microbial protein synthesis and milk performance in early lactating dairy cows

The objective of this study was to evaluate the effects of dietary forage sources on milk performance, rumen microbial protein synthesis, and N utilization in early lactation dairy cows. Twelve primiparous Chinese Holstein dairy cows (45±6.0 DIM) were used in a 3×3 Latin square design. Diets were isonitrogenous and isocaloric, with a forage-to-concentrate ratio of 45:55 [dry matter (DM) basis] and contained similar concentrate mixtures. Different forage sources were then added (on a DM basis): 21% corn silage, 19% corn stover, and 5% alfalfa hay (CS); 19% corn silage, 21% Chinese wild rye hay and 5% alfalfa hay (CWR); or 19% corn silage, 9% Chinese wild rye hay, and 17% alfalfa hay (AH). Each period lasted for 21d, with the first 14d for an adaptation period. Dry matter intake was not affected by the source of dietary forage. Milk yield was higher for cows fed AH than those fed CS, with an intermediate value for CWR. Milk protein content was higher in the cows fed AH compared with CWR (3.02 vs. 2.92%), with CS (2.95%) at an intermediate position. The contents of milk fat and lactose were not different among the treatments. However, milk efficiency (milk yield/DM intake) was higher for cows fed AH than those fed CS, with those fed CWR intermediate. Cows fed AH had higher microbial protein yield and metabolizable protein than those fed CS or CWR. The concentrations of urea N in the urine, blood, and milk were decreased for cows fed AH, indicating an increased N conversion. The results indicated that corn stover could replace Chinese wild rye grass in the diets for lactating cows and that a high proportion of alfalfa hay in the diet is beneficial for milk protein production by increasing microbial protein yield. This can be attributed to the improving the supply of rumen-available energy.

Comparison of ryegrass and red clover on the fermentation pattern, microbial community and efficiency of diet utilisation in the rumen simulation technique (Rusitec)

An in vitro experiment was designed to investigate the effects of incubating two forages with a different energy/nitrogen (N) ratio [perennial ryegrass (GR) vs red clover (RC)] on the efficiency of N utilisation by rumen microbes. Second-cut forages were incubated in artificial rumen fermenters (n = 8). Ryegrass represented a supply of quickly available N and energy for the rumen microorganism which led to a rapid fermentation and bacterial growth 2–4 h after feeding. Ryegrass also promoted greater numbers of anaerobic fungi, methanogens and cellulolytic bacteria, which tended to increase neutral detergent fibre disappearance, gas production, volatile fatty acid and methane production than observed using RC diets. On the contrary, RC provided slowly degradable N and energy, which led to a relatively slow bacterial growth (4–8 h after feeding). In terms of diet utilisation, RC diets promoted a higher N outflow (mainly as undegraded-N) and efficiency of microbial protein synthesis per organic matter disappeared. Even so, microbial protein yield was similar on both diets indicating a better N capture by microorganisms fed GR than in those fed RC diets. The use of 15N-labelled forages demonstrated that this high ammonia incorporation by bacteria-fed GR occurred mainly during the early fermentation coinciding with the highest bacterial growth. In conclusion, this experiment demonstrated that the use of isotopic labelling combined with molecular techniques provided an insight into forage utilisation by the rumen microbes; GR diets led to a better efficiency of N utilisation compared with RC; moreover the lower N outflow on GR diets may be partially compensated for a higher proportion of microbial protein leaving the system and the greater volatile fatty acid production. These findings seem to indicate that RC grazing may increase the N pollution compared with GR without substantial improvements on the rumen function, however this must be confirmed in vivo.

Performance of feedlot Nellore cattle fed with rations containing different corn genotypes

Of the world's maize production, 70% to 85% is used for animal feed and represents a high-quality energy source. The main corn genotypes are flint corn (high vitreous endosperm), semi-flint corn (medium vitreous endosperm), and semi-dent corn (low vitreous endosperm); as the vitreous in the grain increases, starch degradation decreases. The whole grain and intact matrix protein of corn are resistant to digestion by ruminants because rumen bacteria cannot adhere to them. Some studies have shown that starch degradation is better for corn with low vitreous endosperm; however, in Brazil, most of maize produced is flint corn (high vitreous endosperm). Most farmers use corn grain that is ground and incorporated into the concentrate ration for ruminant feeds without consideration of corn genotype or particle size, which influence rumen fermentation, microbial protein yield, and feed efficiency. This trial was conducted to evaluate the performance of beef feedlot cattle that received rations containing different corn genotypes.

Degradation of L-arginine and N-carbamoyl glutamate and their effect on rumen fermentation in vitro

The objective of this experiment was to determine the degradation of L-arginine (ARG) and N-carbamoyl glutamate (NCG) and to examine their effect on rumen fermentation. Rumen fluids were collected from 3 rumen-fistulated cows and then incubated with ARG or NCG at 1 mmol/L in a glass syringe system at 39°C for 24 h. The control treatment was given neither ARG nor NCG. Gas production (GP) was recorded, and pH at 2, 4, 6, 12, and 24 h was also determined. At 12 and 24 h, the measurements were also made for ammonia-nitrogen (N), volatile fatty acids (VFA) and microbial crude protein (MCP) yield on purine quantification basis. At 24 h, the proportion of ARG and NCG degradation in rumen fluid was 100.0 and 17.8%, respectively. Gas production and the acetate to propionate ratio increased in groups treated with ARG and NCG, compared with the control (P<0.01). Ammonia nitrogen concentration was higher (P<0.01) in the ARG group than in the NCG and control groups. Microbial crude protein concentration diminished in ARG and NCG groups, in comparison with the control (P<0.01). In conclusion, the effects of ARG and NCG on rumen fermentation were numerically relatively similar. Rapid degradation of ARG in rumen is a nutritionally wasteful process. Thus, ARG should be spared from rumen degradation, while NCG could be fed to ruminant without need for coating.

Influence of condensed tannin on intake, digestibility, and efficiency of protein utilization in beef steers fed high concentrate diet

This trial was conducted to evaluate if the effect of condensed tannin (CT) is associated with a true protein source on intake, ruminal and total digestibility, ruminal digestion rate, protein efficiency, and microbial efficiency in beef steers fed high concentrate diet (87% of DM). Four Bos indicus steers (407±12kg of BW) fitted with rumen cannula were assigned to a 4×4 Latin square design, arranged in a 2×2 factorial arrangement. Treatments consisted of either inclusion (0.4% of DM) or exclusion of condensed tannin (CT) from quebracho extract (76% of CT) with or without the use of soybean meal (SBM) as source of true protein. The level of inclusion was calculated to provide a daily intake of 1g/10kg of BW of CT. Intake of DM and nutrients was not affected (P>0.10) by CT inclusion. However, there was an effect (P<0.10) of CT inclusion on ether extract digestibility. An interaction (P<0.10) was observed between CT and SBM on ruminal digestibility and digestion rate of crude protein (CP): when mixed with soybean meal, CT decreased the ruminal digestibility and, consequently, reduced the digestion rate of CP. Intake of CP increased (P<0.10) with the inclusion of SBM. No differences in DM passage rate were observed (P>0.10) among treatments. Effects of the interaction (P<0.10) between CT and SBM were observed on flux of rumen undegradable protein (RUP), metabolizable protein (MP), and on the ratio MP:CP. In the presence of soybean meal, the addition of CT increased (P<0.10) the flux of RUP and MP, and improved the ratio MP:CP. The yield of microbial protein on the abomasum and the microbial efficiency did not differ among treatments (P>0.10). There was no difference (P>0.10) on the pH, VFA, and ruminal ammonia (N-NH3) with the addition of condensed tannin. The N-NH3 increased and the ruminal pH decreased with the inclusion of soybean meal (P<0.10). The utilization of condensed tannin as an additive in beef cattle diets with high level of concentrate and soybean meal as a source of true protein implies positive effects on crude protein utilization, decreasing digestion rate and ruminal digestibility of crude protein and consequently increasing the levels of metabolizable protein, with no changes in the ruminal fermentation parameters.

The influence of the grape pomace on the ruminal parameters of sheep

To overcome an animal feed shortage in Iran, the effect of replacing alfalfa with grape ( Vitis vinifera sp.) by-product plus polyethylene glycol (PEG, MW 6000) on the ruminal parameters and retained nitrogen (Nr) of sheep was assessed. In a change-over design experiment 6 sheep with similar live weight (61.8 kg), were used during 3 periods of 28 days. The three dietary treatments, which were iso-caloric and iso-nitrogenous, were; control (alfalfa hay, barley grain, wheat chaff, wheat straw), GP diet (grape pomace, barley grain, wheat chaff and urea) and GP diet + PEG. PEG was used to deactivate tannins in grape pomace. Animals were held in individual metabolism cages. They were adapted to experimental conditions for 21 days, before the commencement of the measurement periods. In each period, the digestibilities of organic matter (OMD), NDF (NDFD), crude protein (CPD) and ruminal parameters (pH, ammonia, bacteria and protozoa population), microbial protein synthesis using urinary purine derivatives and N metabolism in sheep were measured. The concentration of OMD, NDFD and CPD was decreased using grape pomace and the addition of PEG only, improved CPD. The amount of endogenous fecal nitrogen loss and Nr in GP diet were less than control ( P < 0.05), these amounts were increased by the addition of PEG ( P < 0.05). GP diet caused reduction in ruminal parameters (pH, ammonia, cellulolytic and proteolytic bacteria population and protozoa number) and microbial protein yield as compared to the control. The addition of PEG increased those parameters ( P < 0.05). In conclusion, GP diet had a detrimental effect on the rumen parameters and Nr with positive influences of PEG addition on most of these parameters.

Purine derivative excretion and microbial protein synthesis in sheep fed a roughage-based diet supplemented with or without grass silage

In a 3 x 3 Latin square design experiment, urinary excretions of purine derivatives (allantoin N, Uric acid N, Xanthine + Hypoxanthine N) were measured and used to estimate microbial N yield in 9 sheep fed roughage- based diet supplemented with 0, 150 and 300g DM grass silage respectively.&nbsp; Daily urinary excretions of allantoin N, uric acid N, xanthine + hypoxanthine were 3.66, 3.77,4.51, 0.95,1.18,1.24; 1.01,1.21 and 1.34 mmol d-1 for sheep fed roughage-based diet and supplemented with 0,150 and 300g DM silage respectively. Allantoin N, Uric acid N and Xanthine + Hypoxanthine N excretion increased significantly (P&lt;0.01) with increasing amount of silage. Dry matter intake which increased with level of supplementation significantly (P&lt; 0.01) influenced estimated microbial protein yield, which ranged from 4.86 to 6.14g N d-1. The efficiency of conversion of dietary N into microbial N which ranged from 48.17 to 57.22 g N/100g DN was highly significant (P&lt;0.01) as the level of supplementation increased. Microbial N yield per kg of OM fermented (gN/kg DOMR) increased linearly. The results indicate that the amount of microbial N biomass made available to the host animal per unit of feed fermented could be influenced by feed type, level of intake and size of animal. The results also showed that allantoin constituted the highest proportion of purine derivatives excreted. &nbsp;Key Words: Microbial protein, purines, sheep, roughage, silage

Effect of suplemental nitrogen source and feeding frequency on nutrient supply to lambs fed a kikuyu grass ( Pennisetum clandestinum) hay-based diet

Eight castrated male lambs (35 ± 4 kg live weight), fed a basal diet of kikuyu grass hay, were used in a replicated 4 × 4 Latin Square experiment with a 2 × 2 factorial arrangement of treatments to evaluate the effect of supplemental feeding frequency and source of rumen degradable N on intake, digestibility, ruminal fermentation, and microbial protein yield. Treatments were supplementation with cassava meal plus calcium caseinate or cassava meal plus urea offered at a rate of 7 g/kg live weight daily in one or two meals per day. Lambs were fed twice daily in such manner to allow ad libitum comsumption of forage. There was significant feeding frequency by N source interaction on variables of intake. In general, intake of feed components was higher ( P ≤ 0.05) by lambs offered the caseinate-supplement twice daily over intake observed in lambs given the others diet treatments. Digestibility of feed components was neither affected by supplemental N source (DM, P = 0.541; OM, P = 0.585; NDF, P = 0.828) nor by feeding frequency (DM, P = 0.122; OM, P = 0.175; NDF, P = 0.591). Urinary excretion of N increased ( P ≤ 0.05) in lambs supplemented twice daily whereas N retention was similar for all treatments (N source, P = 0.748; feeding frequency, P = 0.418). Microbial protein entering into the small intestine was affected by the interaction between feeding frequency and N source such as an increasing ( P < 0.10) in this variable was observed when lambs received the caseinate but not the urea supplement twice daily. Efficiency of microbial protein synthesis, however, was not affected by treatments (N source, P = 0.588; feeding frequency, P = 0.334). Rumen pH averaged 6.70 and it was neither affected by N source ( P = 0.827) nor by feeding frequency ( P = 0.740). Ruminal concentration of ammonia N was not affected by feeding frequency ( P = 0.144) while it increased ( P < 0.05) when urea rather than caseinate was the supplemental N source (mean of 7.61 mg/dl vs. 6.00 mg/dl). Concentration of sugars in rumen fluid was higher ( P ≤ 0.05) in lambs supplemented once a day compared to twice daily (mean of 49.4 mg/dl vs. 34.4 mg/dl) for both N sources. A significant ( P ≤ 0.05) N source by feeding frequency interaction effect was observed for ruminal concentrations of α-amino N compounds. In urea treatment α-amino N concentration increased ( P ≤ 0.05) in lambs receiving the supplement twice daily compared to once a day (mean of 4.59 mg/dl vs. 3.70 mg/dl) while in caseinate treatment it was higher ( P ≤ 0.05) in lambs offered the supplement in one meal per day compared to twice daily (mean of 5.29 mg/dl vs. 4.07 mg/dl). In conclusion, for ruminants fed a tropical grass-based diet, starch-rich supplement containing non-protein N as N source may be offered only once a day whereas the supply of nutrients may be improved if degradable true protein is included as N source and supplement is offered in two meals per day.

Avaliação nutricional do capim-elefante (Cameroon) em diferentes idades de rebrotação

Objetivou-se determinar o consumo e as digestibilidades aparente total, ruminal e intestinal de matéria seca (MS) e seus componentes: matéria orgânica (MO), proteína bruta (PB), extrato etéreo (EE), fibra em detergente neutro (FDN) e carboidratos não-fibrosos (CNF) do capim-elefante em diferentes idades de rebrotação e quantificar a produção de proteína microbiana. Utilizaram-se quatro novilhos mestiços, fistulados no rúmen e abomaso, alimentados à vontade com capim-elefante e sal mineral. O experimento foi avaliado considerando-se o grupo de animais como uma amostra aleatória simples, sendo os períodos de avaliação correspondentes às idades crescentes de rebrotação (33, 48, 63, 78 e 93 dias) e cada animal como medidas repetidas. Os consumos de matéria seca (MS), nutrientes digestíveis totais (NDT) e as digestibilidades totais dos demais nutrientes diminuíram linearmente com o aumento da idade de rebrotação. Os teores de MO, CNF e FDN apresentaram máximos consumos aos 44,43; 51,05 e 60,50 dias de rebrotação, respectivamente. O mínimo consumo de PB ocorreu aos 94,27 dias de rebrotação do capim. As digestibilidades ruminais da MS e MO aumentaram linearmente com o avanço da idade. Os compostos nitrogenados microbianos sofreram redução linear com o aumento da idade do capim-elefante. Recomenda-se usar o capim-elefante com idade entre 30 e 35 dias de rebrotação, quando se observou maior valor nutritivo da planta.

Effects of formaldehyde treated mustard cake and molasses supplementation on nutrient utilization, microbial protein supply and feed efficiency in growing kids

Twenty healthy growing male kids (Sannen × Beetal and Alpine × Beetal) of 2–3 months of age, weighing 12 ± 0.61 kg, were randomly assigned to one to four dietary treatments in a 2 × 2 factorial design. Two types of isonitrogenous and isocaloric concentrate mixtures were fed to kids in four treatments being: untreated mustard cake, untreated mustard cake with molasses, formaldehyde treated mustard cake and formaldehyde treated mustard cake with molasses. Both concentrate mixtures were similar in composition with the only difference in RDP and UDP due to replacement of untreated mustard cake by formaldehyde (FA) treated mustard cake. Kids were fed concentrate and forage (berseem hay:wheat straw = 2:1) in a 50:50 ratio. A metabolism experiment of 7 days duration was conducted before the end of the experiment. Kids were housed in individual pens and fed experimental diets for 120 days. No differences occurred in digestibility of DM, OM, CP and NDF om, but ether extract digestion in kids fed FA treated mustard cake was higher (P<0.05). Supplementation of molasses increased apparent nutrient digestibility, without influencing digestion of CP and NDF om. Intake of DM, CP and ME did not differ among treatments. The CP content of the diet actually consumed that was supplemented with molasses was lower (P<0.01), with a higher (P<0.01) ME content, without influence of FA treatment on nutritive level of the diet consumed. N balance was higher (P<0.01) in kids fed FA treated MC and supplemental molasses. Microbial protein yield, calculated from purine derivatives excreted in urine, was similar among treatments. The DM intake in the growth experiment was higher by feeding both FA treated MC and molasses. Average daily gain was influenced by feeding FA treated MC, without any effect of supplemental molasses on growth rate of the kids. The higher DM intake and improved growth rate in kids fed FA treated MC resulted better feed efficiency. Higher UDP intake improved growth performance in kids and supplementation of molasses, with or without ruminal escape CP, has no added advantage.

Effect of Dietary Cation-Anion Difference and Dietary Crude Protein on Milk Yield, Acid-Base Chemistry, and Rumen Fermentation

Eight primiparous lactating Holstein cows (47±10 d in milk) fitted with ruminal cannulae were used to determine the effect of dietary cation-anion difference (DCAD) and dietary crude protein (CP) concentration on milk yield and composition, acid-base chemistry, and measures of N metabolism in lactating dairy cows. Treatments were arranged as a 2×2 factorial in a randomized complete block design to provide 15 or 17% CP and DCAD of 25 or 50 mEq (Na + K-Cl)/100g of feed dry matter [15 or 39 mEq (Na + K)-(Cl + S)/100g of feed dry matter]. High DCAD improved dry matter intake, milk yield, and concentrations of milk fat and protein. An interaction of DCAD and CP was observed for uric acid excretion, an indicator of microbial protein yield. Uric acid excretion was higher for high DCAD than for low DCAD in low CP diets and was similar for low and high DCAD with high CP. Serum bicarbonate concentration, urinary bicarbonate excretion, blood pH, and serum Na were elevated for high DCAD compared with low DCAD. Fractional excretion of Na, K, Cl, and Ca increased for high DCAD. Blood urea N and urinary urea N were greater for high than for low CP diets. No differences due to DCAD were observed for these parameters. Results of this study suggest that, in early lactation cows, blood acid-base chemistry is altered by differences in DCAD that range between the high and low ends of the desired DCAD range. Modifications of acid-base chemistry and the corresponding changes in protein metabolism may allow for more efficient feeding of protein and better nutritional management of the lactating dairy cow.

Feasibility of &lt;i&gt;Porphyra haitanensis&lt;/i&gt; as protein source for ruminants

The present study was conducted to investigate the feasibility of Porphyra haitanensis (PH) as protein source for ruminants using in vitro gas test. The PH was inferior to soyabean meal in terms of gas production (GP) and rumen fermentation. When the soyabean meal in the mixed substrates was replaced by PH at levels of 20-100%, GP and volatile fatty acids decreased, while microbial protein yield was not reduced. Inclusion of PH at a level of 30% did not have adverse effect on rumen parameters. It is suggested that PH could be used as protein source to replace soyabean meal.

Apparent Recovery of Duodenal Odd- and Branched-Chain Fatty Acids in Milk of Dairy Cows

This study compared flows of odd- and branched-chain fatty acids (OBCFA) at the duodenum with corresponding yields in milk. Four mid-lactation Holstein-Friesian dairy cows were offered 4 dietary treatments, based on different ratios of ryegrass silage and concentrates (80:20, 65:35, 50:50, and 35:65 on a dry matter basis), in a 4×4 Latin square design experiment with 4-wk periods. Samples of milk and duodenal digesta were collected during the final week of each period and analyzed for fatty acids. Biohydrogenation of linoleic and α-linolenic acids (C18:2 and C18:3) was extensive for all treatments, with a tendency to be lower for C18:3 with increased concentrate feeding. The proportion of duodenal flows of these fatty acids that appeared in milk declined with increasing concentrate feeding. There was little change in the yield of OBCFA in milk in response to increasing level of concentrate inclusion and no significant relationship with the yield of microbial protein at the duodenum. The efficiency of transfer of iso C15:0 and anteiso C15:0 from the duodenum to milk was similar to that for C18:3, with a reduced proportion transferred into milk at higher flows. Yields of C15:0, C17:0, and iso C17:0 in milk were higher than duodenal flows, confirming synthesis in animal tissues.

Effects of fibre and non-fibre carbohydrate and level of intake on microbial protein yield in Sarda sheep

Three studies using Sarda dairy sheep in dry, mid-lactation and late-lactation were carried out. Forty ewes for each physiological stage were fed 8 complete pelleted diets, which differed from each other in NDF and NFC content and source. Based on their main ingredient, diets were denominated: corn meal (CM), wheat middlings (WM), corn flakes (CF), barley meal (BM), corn cobs (CC), beet pulp (BP), alfalfa (AA), and soybean hulls (SH). In each study, rumen microbial protein (MCP) synthesis was estimated measuring urinary purine derivatives. In dry sheep, MCP synthesis was not affected by diet, while in mid- and late-lactation sheep dietary effects were observed. In mid-lactation, the highest MCP production was found for BM and BP (171 and 166 g/d, respectively), while the lowest was observed with AA (63 g/d). In late-lactation, the highest MCP yield (146 g/d) was observed in BP, while the lowest were for SH and CM. MCP synthesis, for each diet, was higher in mid-lactation than in late-lactation, which in turn were higher than in the dry period. Dry matter intake (DMI) was positively associated to MCP. The MCP synthesis was best predicted by dietary energy (NEL) or digestible organic matter intake (dOMI).

Effects of tea saponins on in vitro ruminal fermentation and growth performance in growing Boer goat

Two experiments were conducted to investigate the effects of tea saponins (TS) on in vitro ruminal fermentation and growth performance in growing Boer goats. In Experiment 1, the Reading Pressure Technique (RPT) system was used to investigate the effect of addition of TS (0, 0.2, 0.4 and 0.8 mg/ml) on the ruminal fermentation in vitro. The 24 h gas production and methane emission were significantly decreased when 0.4 or 0.8 mg TS was included, suggesting that the TS could inhibit the release of methane. Compared to the control, the TS had little effect on pH values and the concentration of total volatile fatty acids in the ruminal fluids. However, the fermentation patterns were changed, with lower acetate and higher proportions of propionate when TS was added. Ammonia-N concentration and protozoal counts were significantly reduced, while microbial protein yield was increased by the TS addition, suggesting that the TS could modify the ruminal fermentation. In Experiment 2, 27 growing Boer goats were used to evaluate the effects of the TS addition on growth performance. The animals received the same basal diets, and added TS at levels of 0 (C), 3 g (T1) and 6 g (T2) per day. The experiment lasted for 60 days with the first 15 days for adaptation. Blood samples were obtained by jugular venipuncture before the morning feeding on the final day of the experiment. During the whole periods, dry matter intake, average daily gain and feed efficiency in T1 were higher than in the other two. Serum total protein, albumin, high density lipoprotein cholesterol, Ca and P and alkaline phosphatase levels were higher in group T1 than in C and T2, whereas the blood urea nitrogen, creatinine and total cholesterol were lower in the TS-added groups. The concentrations of glucose, glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase were not affected by the TS. From the results obtained in this study, it is inferred that the TS could modify the ruminal fermentation and that proper doses of TS may have potential in improving the animal growth performance, whereas at high doses, it may have adverse effects on animal production.

Produção de proteína microbiana, concentração plasmática de uréia e excreções de uréia em novilhos alimentados com diferentes níveis de uréia ou casca de algodão

Com o objetivo de avaliar os efeitos dos níveis de uréia ou casca de algodão sobre a produção de proteína microbiana, estimada por meio dos derivados de purinas na urina, a concentração de uréia plasmática (NUP) e as excreções de uréia em novilhos, foram realizados dois experimentos. No primeiro, 24 novilhos mestiços castrados, com peso vivo médio inicial de 300 kg, foram alocados em delineamento inteiramente casualizado, nos quatro tratamentos: 0; 0,65; 1,30 e 1,95% de uréia na base da MS total, em substituição à proteína do farelo de soja. No segundo, 16 novilhos mestiços, com peso vivo médio inicial de 230 kg, foram distribuídos em delineamento inteiramente casualizado, nos quatro tratamentos: 0, 10, 20 e 30% de casca de algodão na base da MS total, em substituição à silagem de capim-elefante. As amostras de urina foram obtidas por meio da coleta de urina spot, na qual foram determinados os derivados de purinas (alantoína e ácido úrico). No soro sanguíneo e na urina, foram analisadas as concentrações de uréia e creatinina. Não houve efeito dos níveis de uréia, tampouco dos de casca de algodão, sobre os derivados de purinas e sobre a eficiência de síntese microbiana. A concentração de NUP e a excreção de uréia não foram influenciadas pelos níveis de uréia das rações. A concentração de NUP decresceu linearmente com a inclusão da casca de algodão na dieta. Tanto a uréia quanto a casca de algodão podem ser utilizadas, até os níveis de 1,95% e 30%, respectivamente, na MS total da dieta de novilhos de origem leiteira, sem afetar a eficiência de síntese microbiana.