Use of near-infrared reflectance spectroscopy for the estimation of the microbial portion of non-ammonia-nitrogen in the duodenum of dairy cows

Ability of three dairy feed evaluation systems to predict postruminal outflows of nitrogenous compounds in dairy cows: A meta-analysis

Adequate prediction of postruminal outflow of protein fractions is the starting point for the determination of metabolizable protein supply in dairy cows. The objective of this meta-analysis was to compare the performance of 3 dairy feed evaluation systems (National Research Council [NRC], Cornell Net Protein and Carbohydrate System [CNCPS], and National Academies of Sciences, Engineering and Medicine [NASEM]) to predict outflows (g/d) of nonammonia nitrogren (NAN), microbial N (MiN), and nonammonia nonmicrobial N (NANMN). Predictions of rumen degradabilities (% of nutrient) of protein (RDP), NDF, and starch were also evaluated. The data set included 1,294 treatment means from 312 digesta flow studies. The 3 feed evaluation systems were compared using the concordance correlation coefficient (CCC), the ratio of root mean square prediction error (RMSPE) on standard deviation of observed values (RSR), and the slope between observed and predicted values. Mean and linear biases were deemed biologically relevant and are discussed if higher than a threshold of 5% of the mean of observed values. The comparisons were done on observed values adjusted or not for the study effect; the adjustment had a small effect on the mean bias but the linear bias reflected a response to a dietary change rather than absolute predictions. For the absolute predictions of NAN and MiN, CNCPS had the best-fit statistics (8% greater CCC; 6% lower RMSPE) without any bias; NRC and NASEM underpredicted NAN and MiN, and NASEM had an additional linear bias indicating that the underprediction of MiN increased at increased predictions. For NANMN, fit statistics were similar among the 3 feed evaluation systems with no mean bias; however, the linear bias with NRC and CNCPS indicated underprediction at low predictions and overprediction at elevated predictions. On average, the CCC were smaller and RSR ratios were greater for MiN versus NAN indicating increased prediction errors for MiN. For NAN responses to a dietary change, CNCPS also had the best predictions, although the mean bias with NASEM was not biologically relevant and the 3 feed evaluation systems did not present a linear bias. However, CNCPS, but not the 2 other feed evaluation systems, presented a linear bias for MiN, with responses being overpredicted at increased predictions. For NANMN, responses were overpredicted at increased predictions for the 3 feed evaluation systems, but to a lesser extent with NASEM. The site of sampling had an effect on the mean bias of MiN and NANMN in the 3 feed evaluation systems. The mean bias of MiN was higher in omasal than duodenal studies in the 3 feed evaluation systems (from 55 to 61 g/d) and this mean bias was twice as large when 15N labeling was used as a microbial marker compared with purines. Such a difference was not observed for duodenal studies. The reasons underlying these systematic differences are not clear as the type of measurements used in the current meta-analysis does not allow to delineate if one site or one microbial marker is yielding the "true" postruminal N outflows. Rumen degradabilities of protein was underpredicted with CNCPS, and RDP responses to a dietary change was underpredicted by the 3 feed evaluation systems with increased RDP predictions. Rumen degradability of NDF was underpredicted and had poor fit statistics for NASEM compared with CNCPS. Fit statistics were similar between CNCPS and NASEM for rumen degradability of starch, but with an underprediction of the response with NASEM and absolute values being overpredicted with CNCPS. Multivariate regression analyses showed that diet characteristics were correlated with prediction errors of N outflows in each feed evaluation system. Globally, compared with NAN and NANMN, residuals of MiN were correlated with several moderators in the 3 feed evaluation systems reflecting the complexity to measure and model this outflow. In addition, residuals of NANMN were correlated positively with RDP suggesting an overestimation of this parameter. In conclusion, although progress is still to be made to improve equations predicting postruminal N outflows, the current feed evaluation systems provide sufficient precision and accuracy to predict postruminal outflows of N fractions.

Effects of Different Concentrate Feed Proportions on Ruminal Ph Parameters, Duodenal Nutrient Flows and Efficiency of Microbial Crude Protein Synthesis in Dairy Cows During Early Lactation

The aim of the study was to examine different pH parameters, such as variations throughout the day, depending on differing concentrate feed proportions. Moreover, special attention was payed to individual variation in microbial efficiencies (microbial crude protein/fermented organic matter) and their relation to ruminal pH, nutrient flows and digestibilities. For this, cows were grouped according to microbial efficiency (more, n = 5, vs. less efficient cows, n = 4). After calving, thirteen ruminally cannulated pluriparous cows, including nine duodenally cannulated animals, were divided into groups offered rations with a lower (35% on dry matter basis, n = 7) or a higher (60% on dry matter basis, n = 6) concentrate feed proportion. Ruminal pH parameters were assessed continuously by using intraruminal probes. Nutrient flows, nutrient digestibility and microbial efficiency were determined for duodenally cannulated cows. For most ruminal pH parameters it seemed that individual variability was higher than the treatment effect. However, a positive relationship between actual concentrate intake and diurnal pH fluctuations was found. Besides, the effect of individually different microbial efficiencies was assessed. Again, there were no group differences for pH parameters. However, nutrient flows were significantly higher in more efficient cows, whereas digestibilities were lower in in more efficient cows.

Influence of vitamin E on organic matter fermentation, ruminal protein and fatty acid metabolism, protozoa concentrations and transfer of fatty acids

Vitamin E (Vit. E) is discussed to influence ruminal biohydrogenation. The objective of this study was to investigate the influence of a Vit. E supplementation on rumen fermentation characteristics, ruminal microbial protein synthesis as well as ruminal organic matter fermentation. Furthermore, we aimed to investigate the influence of Vit. E supplementation on short-chain fatty acids (SCFA) and protozoa concentrations in the rumen and, in addition, on transfer rates of middle-chain and long-chain fatty acids into the duodenum in lactating dairy cows. Eight rumen and duodenum fistulated German Holstein cows were assigned to either a group receiving 2,327 IU/d Vit. E (138.6 IU/kg DM DL-α-tocopherylacetate; n = 4) or a control group (23.1 IU/kg DM; n = 4). Neither ruminal protein synthesis nor organic matter fermentation was influenced by treatment. Vit. E did not act on the concentrations of short-chain fatty acids and protozoa in rumen fluid. Duodenal flow of C13:0 (1.3 versus 0.2 g/d, p = 0.014) and iso-C14:0 (1.0 versus 0.5 g/d, p = 0.050) was higher in the Vit. E group. We observed a trend for higher duodenal flows for C12:0 (1.6 versus 0.9 g/d, p = 0.095) and anteiso-C15:0 (12.2 versus 8.9 g/d, p = 0.084). Transfer rate of C12:0 tended to be higher in the Vit. E group (125.61 versus 73.96, p = 0.082). No other transfer rates were affected by treatment. Further studies are necessary to investigate the influence of Vit. E on rumen microbiota and their fatty acid production as well as on the impact of different doses of Vit. E supplementation on variables of protein synthesis efficiency.

Effects of the level of feed intake and ergot contaminated concentrate on ruminal fermentation and on physiological parameters in cows

The aim of the present study was to examine the effects of ergot contaminated feed concentrate at differing levels of feed intake on ruminal fermentation, and on various physiological parameters of dairy cows. Twelve double fistulated (in the rumen and the proximal duodenum) Holstein Friesian cows were fed either a control diet (on a dry matter (DM) base: 60% maize silage, 40% concentrate) or a diet containing ergot alkaloids (concentrate contained 2.25% ergot resulting in an ergot alkaloid concentration of the daily ration between 505 and 620 (μg/kg DM) over a period of four weeks. Daily feed amounts were adjusted to the current performance which resulted in a dry matter intake (DMI) variation between 6.0 and 18.5 kg/day. The resulting ergot alkaloid intake varied between 4.1 and 16.3 (μg/kg body weight when the ergot contaminated concentrate was fed.Concentrations of isovalerate, propionate and ammonia nitrogen in the rumen fluid were significantly influenced by ergot feeding, and the amount of ruminally undegraded protein, as well as the fermentation of neutral detergent fibre, tended to increase with the ergot supplementation at higher levels of feed intake, which might indicate a shift in the microbial population. Other parameters of ruminal fermentation such as ruminai pH, fermented organic matter as a percentage of intake, or the amount of non-ammonia nitrogen measured at the duodenum were not significantly influenced by ergot feeding. The activities of liver enzymes (aspartate aminotransferase, γ-glutamyltransferase, glutamate dehydrogenase, creatine kinase) in the serum were not affected by ergot feeding. The rectal measured body temperature of the cows significantly increased after ergot administration (p=0.019). Thus, body temperature can be regarded as a sensitive parameter to indicate ergot exposure of dairy cows.

Effect of niacin supplementation on rumen fermentation characteristics and nutrient flow at the duodenum in lactating dairy cows fed a diet with a negative rumen nitrogen balance

The aim of the present experiment was to ascertain if a daily niacin supplementation of 6 g/cow to lactating dairy cow diets can compensate for the decrease in rumen microbial fermentation due to a negative rumen nitrogen balance (RNB). A total of nine ruminally and duodenally fistulated lactating multiparous German Holstein cows was used. The diets consisted of 10 kg dry matter (DM) maize silage and 7 kg DM concentrate and differed as follows: (i) Diet RNB- (n = 6) with energy and utilisable crude protein (CP) at the duodenum (uCP) according to the average requirement of the animals, but with a negative RNB (-0.41 g N/MJ metabolisable energy [ME]); (ii) Diet RNB0 (n = 7) with energy, uCP, and RNB (0.08 g N/MJ ME) according to the average requirement of the animals; and (iii) Diet NA (nicotinic acid; n = 5), which was the same diet as RNB-, but supplemented with 6 g niacin/d. The negative RNB affected the rumen fermentation pattern and reduced ammonia content in rumen fluid and the daily duodenal flows of microbial CP (MP) and uCP. Niacin supplementation increased the apparent ruminal digestibility of neutral detergent fibre. The efficiency of microbial protein synthesis per unit of rumen degradable CP was higher, whereby the amount of MP reaching the duodenum was unaffected by niacin supplementation. The number of protozoa in rumen fluid was higher in NA treatment. The results indicated a more efficient use of rumen degradable N due to changes in the microbial population in the rumen when niacin was supplemented to diets deficient in RNB for lactating dairy cows.

Effect of Fusarium toxin-contaminated triticale and forage-to-concentrate ratio on fermentation and microbial protein synthesis in the rumen

In this study, the effect of Fusarium toxin-contaminated triticale (FUS) at high (60%) and low (30%) concentrate proportion in ruminant rations on ruminal fermentation, microbial protein synthesis and digestibility was investigated, using in vivo and in vitro methods. Significant effects of the forage-to-concentrate ratio on ruminal degradation and digestibility of crude nutrients and detergent fibre fractions as well as on the pH value and the concentration of short chain fatty acids (SCFA) in rumen fluid were found. The production of SCFA was affected, and the degradation of crude fibre and neutral detergent fibre in the rumen was reduced by the inclusion of FUS at high concentrate proportion. The efficiency of microbial crude protein synthesis was higher in diets with 60% than in diets with 30% concentrates, but was impaired in the presence of FUS in vitro at the high concentrate level. Marginal effects of FUS on the amino acid pattern of microbial protein were detected. It was concluded that the use of FUS in high concentrate diets can influence ruminal fermentation and microbial protein synthesis at a dietary deoxynivalenol concentration below 5 mg/kg dry matter.

Effects of folic acid supplementation to rations differing in the concentrate to roughage ratio on ruminal fermentation, nutrient flow at the duodenum, and on serum and milk variables of dairy cows

The present study was undertaken to determine the effects of dietary folic acid (FOL) supplementation on ruminal fermentation, duodenal nutrient flow, serum and milk variables, and on B-vitamin concentration in serum. The study was divided into two experiments: in Exp. 1 the forage to concentrate (F:C) ratio of the diet (DM basis) was 34:66 (high concentrate, HC), while in Exp. 2 the F:C ratio was 66:34 (high forage, HF). In addition, the cows received 0 or 1 g FOL/d. In Exp. 1, two German Holstein cows equipped with cannulas in the dorsal sac of the rumen and in the proximal duodenum were dry and five were lactating (186 +/- 144 days in milk); in Exp. 2 four cows were dry and four were lactating (165 +/- 57 days in milk). In cows fed the HC diet, FOL supplementation decreased the ruminally-fermented organic matter. Thus, less energy was available for ruminal microorganisms, which resulted in a reduced microbial crude protein flow at the duodenum. Feeding the HF diet, FOL supplementation only increased the apparent ruminal digestibility of acid detergent fibre (ADF). With the HF diet, FOL had no influence on the serum levels of glucose, non-esterified fatty acids, beta-hydroxybutyrate, urea, thiamine, riboflavin, pyridoxal-5'-phosphate, pyridoxic acid, pyridoxal, pyridoxine, pyridoxamine, pantothenic acid, nicotinamide or nicotinic acid, whereas supplementing FOL to the HC diet lowered the serum glucose and riboflavin levels. In both experiments, the supplementation of FOL had no effects on milk composition. Folic acid supplementation to both diets increased the concentrations of serum 5-methyl-tetrahydrofolate. However, no beneficial effects to dairy cows were obvious. Therefore, to achieve certain results, studies with a higher number of non-fistulated cows would be necessary.

Investigations on the effect of the ruminal N-balance on rumen metabolism, urea content in blood serum and milk as well as some liver parameters of lactating cows

Seven dairy cows fitted with ruminal and duodenal cannulae were used to investigate the influence of the amount of ruminally available N (Ruminal N-Balance, RNB) on the rumen metabolism and to answer the question on the lowest N-amount in the rumen, without negative effects on the fermentation. Animals were fed a ration on the basis of 7.9 kg corn silage and 7.2 kg concentrates related to dry matter, intended to meet the animals mean NEL and protein requirements. RNB amounted to -0.6 g/MJ ME in the basis ration. The other 3 rations were adjusted to RNB-values of -0.3, 0 and + 0.3 g/MJ ME by urea supplements in the concentrates. The increase in RNB resulted in higher NH3-N concentrations in the rumen fluid and in the duodenal digesta and higher urea concentrations in the blood and milk. The significantly highest amount of protein at the duodenum was detected when RNB showed an equilibrium (RNB = 0). The efficiency of microbial protein (MP) synthesis (gMP/kg fermented organic matter) was the same, g MP/d and g MP/MJ ME were significantly lower with RNB = -0.6g/MJ ME as compared to RNB = 0. The group with thelowest RNB showed the highest level of feedprotein degradation as well as the lowest organic matter, NDF and ADF fermentation. An effect on cholesterol, total bilirubin and gammaGT due to different RNB was not detected. The activities of GLDH and AST were highest when the RNB was -0.6 g/MJ ME. From the results, it can be concluded that significantly negative effects on rumen fermentation occur when RNB-values are below -0.3 g/MJ ME. However, a positive RNB did not increase t he degradation and synthesis capacity of the rumen micro-organisms as compared to RNB = 0.

Effects of level of feed intake and Fusarium toxin-contaminated wheat on rumen fermentation as well as on blood and milk parameters in cows

The aims of this study were to examine the effects of and possible interactions between dry matter (DM) intake and feeding Fusarium toxin-contaminated wheat on ruminal fermentation, serum chemical parameters and milk yield of dairy cows. Fourteen dairy cows equipped with ruminal and duodenal cannulas were analysed. All animals were fed the same ration, the daily feed amounts being adjusted to current performance. On DM basis, the ration consisted of 60% concentrate including 55% wheat [Fusarium-contaminated wheat (mycotoxin period) or control wheat (control period)] and was completed with 40% maize and grass silage. Each cow was fed the contaminated wheat [deoxynivalenol (DON), 8.21 mg/kg DM and zearalenone (ZON), 0.09 mg/kg DM] and the control wheat (0.25 mg DON/kg DM and 51 microg ZON/kg DM). As expected, a higher organic matter (OM) intake decreased the amounts of fermented crude nutrients related to the respective intakes. An increased amount of crude protein degraded (p < 0.05) and a lower molar percentage of propionate in the rumen fluid were observed when feeding the Fusarium toxin-contaminated wheat at increased OM intakes in comparison with the control wheat. The activities of serum aspartate aminotransferase (ASAT; p < 0.001), glutamate dehydrogenase (GLDH; p < 0.01) and gamma glutamyl transferase (gamma-GT; p < 0.01) increased with increasing OM intake and were not related to the mycotoxin contamination of the wheat.

Studies on the biotin flow at the duodenum of dairy cows fed diets with different concentrate levels and types of forages

Biotin is involved in many vital metabolic pathways and must be provided for an efficient fermentation in the rumen, as well as for the intermediary metabolism of the host animal. Factors influencing ruminal biotin metabolism and output are widely unknown at present. Therefore, dairy cows fitted with permanent cannulas in the dorsal rumen and in the proximal duodenum were fed differently composed diets, and the biotin flow at the proximal duodenum was measured. The diets (on DM basis) consisted of 8.9 kg grass hay (Diet 1), 8.9 kg corn silage plus 2.0 kg concentrate (Diet 2), or 7.3 and 7.4 kg grass silage plus 10.0kg concentrate (Diets 3 and 4). The concentrate in Diets 3 and 4 contained 87% wheat and corn grain, respectively. The cows were pre-fed the rations for 21 days. Thereafter duodenal digesta was sampled every two h for 5 days. Cr2O3 served as a flow marker and the microbial proportion of total nitrogen at the duodenum was estimated by near infrared spectroscopy (NIRS). The duodenal flow of biotin was not related to biotin intake, but to the amount of fermented organic matter (FOM) and the amount of microbial protein (Biotin [mg/d] = 0.518 kg FOM - 0.300; r=0.85 and biotin [mg/d] = 0.012 x g microbial protein + 1.478; r = 0.84), irrespective of the composition of the diet fed. Mean daily biotin flow was 0.48 +/- 0.11 mg/kg FOM without any systematic effect of diet composition. The ruminal biotin balance, calculated as the difference between biotin flow at the duodenum and biotin intake, was positive (1.4 - 2.0 mg/d) in cows fed the mixed roughage/concentrate diets and negative (-0.71 mg/d) when the pure hay diet was fed.

Effects of Fusarium toxin-contaminated wheat grain on nutrient turnover, microbial protein synthesis and metabolism of deoxynivalenol and zearalenone in the rumen of dairy cows

The aim of the present study was to examine the effects of feeding Fusarium toxin-contaminated wheat to dairy cows on nutrient utilization in the rumen and on duodenal flow of deoxynivalenol (DON), zearalenone (ZON) and their metabolites. Six dairy cows fitted with a large rumen cannula and a simple T-shaped cannula at the proximal duodenum was used in two experiments. The experiments included a control period in which the uncontaminated control wheat was fed and a period in which the control wheat was replaced by the Fusarium toxin-contaminated wheat (8.05 and 7.15 mg DON/kg and 0.26 and 0.1 mg ZON/kg in Expts 1 and 2 respectively). The wheat portion of the daily ration amounted to 50% on a dry matter (DM) basis and rations were completed with hay or grass silage. Five of the six cows were non-lactating and the total daily DM-intake ranged between 4 and 12 kg. The pH-values and the concentration of volatile fatty acids in ruminal fluid were not significantly influenced by feeding the contaminated wheat. In contrast, the postprandial ammonia concentration was consistently higher when the mycotoxin-contaminated wheat was fed. Moreover, the flow of microbial protein and utilizable protein at the duodenum were reduced at the same time. The concentrations of DON and ZON and of their metabolites in freeze-dried duodenal digesta were either not detectable or negligible during the control periods whereas distinct concentrations were measured during the periods where the contaminated wheat was fed. DON was nearly completely metabolized to de-epoxy-DON and the flow at the duodenum ranged between 4% and 28% of DON-intake. The ZON metabolites alpha-zearalenol (ZOL) and beta-ZOL were recovered at the duodenum beside the parent toxin ZON. Their recovery as a percentage of ZON-intake ranged between 43% and 132%. In conclusion, feeding of Fusarium toxin-contaminated wheat altered the ruminal protein utilization. The question of whether this effect was a result of the mycotoxin being present in the rumen or of Fusarium growth-related structural (cell wall) changes of the wheat grain needs to be clarified. The low recovery of DON at the duodenum would indicate either a nearly complete degradation of the molecule in the rumen or an absorption by the mucosa of the rumen, whereas the higher ZON recovery would suggest a lower degradation of the parent toxin in the rumen and/or recovery of some bile-originating entero-hepatic cycling ZON/metabolites.