Peter Lebzien

Effects of Fusarium toxin-contaminated wheat and feed intake level on the biotransformation and carry-over of deoxynivalenol in dairy cows

An experiment was carried out to examine the effects of feeding Fusarium toxin-contaminated wheat (8.21 mg deoxynivalenol (DON) and 0.09 mg zearalenone (ZON) per kg dry matter) at different feed intake levels on the biotransformation and carry-over of DON in dairy cows. For this purpose, 14 ruminal and duodenal fistulated dairy cows were fed a diet containing 60% concentrate with a wheat portion of 55% (Fusarium toxin-contaminated wheat (mycotoxin period) or control wheat (control period)) and the ration was completed with maize- and grass silage (50 : 50) on a dry matter basis. Daily DON intakes ranged from 16.6 to 75.6 mg in the mycotoxin period at dry matter intakes of 5.6–20.5 kg. DON was almost completely biotransformed to de-epoxy DON (94–99%) independent of the DON/feed intake, and the flow of DON and de-epoxy DON at the duodenum related to DON intake ranged from 12 to 77% when the Fusarium toxin-contaminated wheat was fed. In the serum samples, de-epoxy DON was detected in the range of 4–28 ng ml−1 in the mycotoxin period, while concentrations of DON were all below the detection limit. The daily excretion of DON and de-epoxy DON in the milk of cows fed the contaminated wheat varied between 1 and 10 µg and between 14 and 104 µg, respectively. The total carry-over rates as the ratio between the daily excretion of DON and de-epoxy DON into milk and DON intake were in the ranges of 0.0001–0.0002 and 0.0004–0.0024, respectively. Total carry-over rates of DON as DON and de-epoxy DON into the milk increased significantly with increasing milk yield. In the urine samples, de-epoxy DON was the predominant substance as compared with DON with a portion of the total DON plus de-epoxy DON concentration to 96% when the Fusarium toxin-contaminated wheat was fed, whereas the total residues of DON plus de-epoxy DON in faeces ranged between 2 and 18% of DON intake in the mycotoxin period. The degree of glucuronidation of de-epoxy DON was found to be approximately 100% in serum. From 33 to 80% of DON and from 73 to 92% of de-epoxy DON, and from 21 to 92% of DON and from 86 to 100% of de-epoxy DON were glucuronidated in the milk and urine, respectively. It is concluded that DON is very rapidly biotransformed to de-epoxy DON in the rumen and only negligible amounts of DON and de-epoxy DON were transmitted into the milk within the range of 5.6–20.5 kg day−1 dry matter intake and milk yields (fat corrected milk) between 10 and 42 kg day−1.

Calculation of utilizable crude protein at the duodenum of cattle by two different approaches

The duodenal flow of utilizable crude protein (crude protein minus endogenous protein) in cows was estimated using dietary parameters, first by multiple regression and secondly by the addition of microbial protein and undegraded feed protein. These estimates were compared with 327 results from experiments conducted with fistulated cows in Braunschweig-Völkenrode and Rostock-Dummerstorf. The regressions and the measurements for microbial protein synthesis as well as feed protein degradation and organic matter fermentation in the rumen were based on the same experimental data set. The prediction of utilizable crude protein (uCP) at the duodenum by regression with digested organic matter (kg DOM) and undegraded feed protein (g UDP) as predicting variables, was more accurate than the value given by microbial protein synthesis and rumen protein degradability. The regression model [g uCP = [188.5-(116.5 (UDP/CP))] DOM + 1.03 UDP] had the highest coefficient of determination (r2 = 0.91) and the lowest coefficient of variation (cv = 8.6); indicating the models superiority over the other method of estimation.

Iodine concentration of milk in a dose-response study with dairy cows and implications for consumer iodine intake.

Most feed is poor in iodine and iodine supplementation of cows diets must guarantee milk iodine concentrations for humans that contribute to prevention of the deficiency and minimize the risk of exceeding an upper limit of iodine intake. Five Holstein cows were fed four iodine doses (via Ca(Iota O(3))(2).6H(2)O). In four sequential 14-d periods, doses of 0.2 (basal diet), 1.3, 5.1, and 10.1 mg iodine kg(-1) diet dry matter (DM) were administered. Samples of milk were collected during each period; blood was also sampled from each cow for each iodine dosage. In an 18-d depletion period, a non-supplemented diet was provided. Iodine was determined by inductively coupled plasma-mass spectrometry. The iodine content of milk and serum reflected the iodine dosages in feed significantly. The levels for the four doses tested in milk were 101+/-32, 343+/-109, 1215+/-222, and 2762+/-852 microg iodine kg(-1). The total amount of iodine in milk per day was 30-40% of ingested supplemental iodine. Omitting additional iodine resulted in a short-term reduction of serum and milk iodine following an exponential decay function. The iodine supplementation of 0.5-1.5 mg kg(-1) diet DM represents the requirement of the cow, resulting in 100-300 microg iodine L(-1) milk, which optimally contributes to human supply. The maximum dietary levels of former and present EU legislations (10 and 5 mg iodine kg(-1) cow feed) increase the risk of iodine excess in humans.

Niacin for dairy cattle : a review

Due to the incorporation of niacin into the coenzymes NAD and NADP, niacin is of great importance for the metabolism of man and animals. Apart from niacin in feed and endogenous formation, microbial niacin synthesis in the rumen is an important source for dairy cows. But the amount synthesised seems to differ greatly, which might be influenced by the ration fed. Many studies revealed a positive impact of a niacin supplementation on rumen protozoa, but microbial protein synthesis or volatile fatty acid production in the rumen showed inconsistent reactions to supplemental niacin. The amount of niacin reaching the duodenum is usually higher when niacin is fed. However, not the whole quantity supplemented reaches the duodenum, indicating degradation or absorption before the duodenal cannula. Furthermore, supplementation of niacin did not always lead to a higher niacin concentration in blood. Effects on other blood parameters have been inconsistent, but might be more obvious when cows are in a tense metabolic situation, for example, ketosis or if high amounts are infused post-ruminally, since ruminal degradation appears to be substantial. The same is valid for milk parameters. In the few studies where blood niacin and milk parameters have been investigated, enhanced niacin concentrations in blood did not necessarily affect milk production or composition. These results are discussed in the present review, gaps of knowledge of niacins mode of action on the metabolism of dairy cows are identified and directions for future research are suggested.

On the effects of Fusarium toxin-contaminated wheat and the feed intake level on the metabolism and carry over of zearalenone in dairy cows.

The aim was to investigate the effect of feeding Fusarium toxin-contaminated wheat to dairy cows on the metabolism and carry over of zearalenone (ZON) and its metabolites at different feed intakes. Fourteen dairy cows equipped with rumen and duodenal fistulae were used. The experiment consisted of a control period in which the uncontaminated wheat was fed and a mycotoxin period in which the Fusarium toxin-contaminated wheat (8.21 mg deoxynivalenol (DON) and 91 µg ZON kg−1 dry matter (DM)) was replaced by the control wheat (0.25 mg DON kg−1 and 51 µg ZON kg−1 DM). The wheat portion of the concentrate fed daily amounted to 55% on a DM basis. The ration was completed with maize and grass silage (50:50), whereby the maize silage contained 62 µg ZON kg−1 DM. Feed intakes were adjusted to the current performance of the individual cows. The ZON metabolites α-zearalenol (α-ZOL) and β-zearalenol (β-ZOL) were recovered at the duodenum beside the parent toxin ZON. The recovery of ingested ZON as ZON plus α-ZOL plus β-ZOL at the duodenum ranged between 19 and 247%. The portion of ZON (ranging from 29 to 99%) of the ZON plus α-ZOL plus β-ZOL flow at the duodenum increased significantly with increasing ZON feed intake, whereas the portion of β-ZOL (up to 57%) decreased significantly. In contrast, portions of ZON in faeces (32–100%), α-ZOL (up to 39%) and β-ZOL (up to 43%) of ZON plus α-ZOL plus β-ZOL were independent of ZON intake. It seems that a lower retention time of the feed and the toxins in the rumen as an effect of the increased feed intake may limit the ruminal metabolization of ZON. The relatively steady recovery of ingested ZON as ZON, α-ZOL and β-ZOL in faeces at the different levels of ZON intake would suggest a further reduction of ZON by intestinal microorganisms. Furthermore, ZON and its metabolites in the milk were lower than the detection limits at daily ZON and DM intakes between 75 and 1125 µg and 5.6 and 20.5 kg day−1, respectively, and milk yields (fat corrected milk, FCM) between 10 and 42 kg day−1.

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

Abstract The analytical potential of near-infrared reflectance spectroscopy (NIRS) was tested for predicting the microbial portion of the total N at the duodenum of lactating cows. Samples and reference data were obtained from animals fitted with rumen cannulae and proximally positioned duodenum cannulae and fed 40 different diets. From a total of 158 individual experiments, the microbial portion of the total N at the duodenum as well as the total flow of microbial-N were satisfactorily estimated by NIRS as compared to 15 N measurements which served as reference. The standard error of predicting the microbial portion of the total N at the duodenum amounted to 3.1% in absolute terms and 4.5% in relative terms. Calculated values for the daily rate of microbial protein synthesis per unit intake of metabolisable energy and daily flow rate of microbial-N at the duodenum showed no relevant difference between the two methods of assessment. The results indicate that NIRS is an interesting tool for estimating the microbial portion of the total N at the duodenum rapidly and at low cost.

Effects of the level of feed intake and ergot contaminated concentrate on ergot alkaloid metabolism and carry over into milk

The aim of the present study was to examine the effects of ergot contaminated concentrate at differing levels of feed intake on ergot alkaloid metabolism and carry over into milk. Twelve double fistulated (in the rumen and the proximal duodenum) Holstein Friesian cows were fed either the control diet (on a dry matter (DM) base: 60% maize silage, 40% concentrate) or the contaminated diet (concentrate contained 2.25% ergot, which caused an alkaloid concentration of the daily ration between 504.9 and 619.5 microg/kg DM) over a period of 4 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 actual alkaloid exposure varied between 4.1 and 16.3 microg/kg body weight when the ergot contaminated concentrate was fed. Approximately 67% of the alkaloids fed were recovered in the duodenal ingesta, and approximately 24% were excreted with the faeces. No alkaloid residues could be detected in the blood or milk samples.

Effect of starch application into the proximal duodenum of ruminants on starch digestibility in the small and total intestine.

Four Slovakian Black‐and‐white bulls (LW 410 ± 12 kg; Exp. 1) and four Slovakian Black‐and‐white non lactating dairy cows (LW 475 ± 14 kg; Exp. 2) with permanent ruminal cannulas, duodenal T‐cannulas and ileal re‐entrant cannulas were used in a 4 × 4 Latin square design to determine the postruminal capacity of starch digestion. In Exp. 1 bulls received 5.4 kg DM from corn silage and 3.6 kg DM from alfalfa hay, in Exp. 2 cows consumed only 2.1 kg DM corn silage and 1.9 kg DM alfalfa hay. Additionally, either 750 or 1500 g (Exp. 1) or resp. 1000 or 2000 g (Exp. 2) gelatinized corn or wheat starch per animal and day were applied as pulse doses or as infusion into the proximal duodenum. In both experiments the duodenal and ileal nutrient flow, as well as the faecal excretion without starch application, were measured in a pre‐period. After starting starch application ileal digesta and faeces were sampled over 120 h after 9 or 23 days of adaptation respectively. Cr2O3 was used as a flow marker. It was shown, that the capacity of starch utilisation in the small intestine was limited. The effect of different doses of bypass‐starch was more pronounced than the effect of different starch sources. Starch digestibility decreased with increasing amounts of starch in the intestine (Exp. 1: corn starch: from 74.3 to 68.0%, P < 0.001; wheat starch: from 76.7 to 67.4%, P <0.001; Exp. 2: corn starch: from 71.4 to 50.3%, P <0.001; wheat starch: from 73.8 to 53.1%, P <0.001). Corn starch was 0.6 to 2.4% units (P <0.05) and 2.4 to 2.8% units (P < 0.001) less digested than wheat starch in Exp. 1 and Exp. 2, respectively. The decreased starch digestibility in the small intestine with increasing amounts of starch at the duodenum was not totally compensated in the large intestine. The starch digestibility in the total intestine for the low and high amounts of applied starch was: 83.7 and 81.0% (P < 0.001, corn starch, Exp. 1), 86.0 and 81.7% (P < 0.001, wheat starch, Exp. 1), 95.5 and 79.1% (P < 0.001, corn starch, Exp. 2), 99.8 and 81.7% (P < 0.001, wheat starch, Exp. 2). Corn starch was 0.7 to 2.3% units (P <0.001) and 2.6 to 4.3% units (P <0.001) less digested than wheat starch in Exp. 1 and Exp. 2, respectively. Model calculations were used to quantify the efficiency of starch utilisation. The recommended maximal amount of bypass‐starch is supposed to be 1.3 to 1.8 kg per animal and day.

Influence of roughage/concentrate ratio and linseed oil on the concentration of trans-fatty acids and conjugated linoleic acid in duodenal chyme and milk fat of late lactating cows.

Abstract The objective of the study was to investigate the influence of two roughage-to-concentrate ratios, with or without linseed oil supplementation, on the flow of fatty acids in the intestinal chyme and the secretion in milk fat in late lactating cows. Seven late lactating cows fitted with cannulae in the dorsal rumen and simple T-shaped cannulae in the proximal duodenum were randomly assigned to four experimental periods applying an incomplete replicated 2×2 Latin square design. The rations consisted of meadow hay and a concentrate mixture given in a ratio of 70 : 30 or 30 : 70 on dry matter basis. The basal rations were fed without or with 200 g linseed oil daily. After three weeks of adaptation, samples from the duodenal chyme were taken to study the flow of fatty acids. Additionally, milk samples were analysed for their milk fat composition. Decreasing roughage/concentrate ratio and linseed oil supplementation significantly increased the flow of monounsaturated fatty acids (MUFA), trans-fatty acids (tFA) and conjugated linoleic acids (CLA) in the duodenum. Furthermore, linseed oil increased the flow of saturated fatty acids (SFA) in the duodenum. Higher concentrate portion (H 30) and linseed oil supplementation significantly decreased the milk fat content. SFA were lower (p < 0.05) and MUFA were higher (p < 0.05) in milk fat after linseed oil supplementation; H 30 resulted in more polyunsaturated fatty acids (PUFA, p < 0.05) in the milk. Linseed oil supplementation significantly increased tFA and CLA in milk fat. The higher CLA content in milk fat as compared to that in the digesta suggests that a substantial endogenous synthesis of CLA in the mammary gland tissue through Δ9-desaturase took place. Between 21% and 48% of duodenal t11-C18:1 were converted into c9, t11-CLA in milk fat.

Effect of niacin supplementation on digestibility, nitrogen utilisation and milk and blood variables in lactating dairy cows fed a diet with a negative rumen nitrogen balance

The aim of the present experiment was to determine if a niacin supplementation of 6 g/d to lactating dairy cow diets can compensate negative effects of a rumen nitrogen balance (RNB) deficit. A total of nine ruminally and duodenally fistulated lactating multiparous German Holstein cows were successively assigned to one of three diets consisting of 10 kg maize silage (dry matter [DM] basis) and7 kg DM concentrate: Diet RNB– (n = 6) with energy and utilisable crude protein 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]); Diet RNB0 (n = 7) with energy, uCP and a RNB (0.08 g N/MJ ME) according to the average requirement of the animals and, finally, Diet NA (n = 5), which was the same diet as RNB–, but supplemented with 6 g niacin/d. Samples of milk were taken on two consecutive days, blood samples were taken on one day pre- and post-feeding and faeces and urine were collected completely over five consecutive days. The negative RNB reduced milk and blood urea content and apparent total tract digestibility of DM, organic matter (OM) and neutral detergent fibre (NDF). Also N excretion with urine, the total N excreted with urine and faeces and the N balance were reduced when the RNB was negative. Supplementation of niacin elevated plasma glucose concentration after feeding and the N balance increased. Supplementing the diet with a negative RNB with niacin led to a more efficient use of dietary N thereby avoiding the negative effects of the negative RNB on the digestibility of DM, OM and NDF.