Digestibility, ruminal fermentation, ingesta kinetics and nitrogen utilisation in dairy cows fed diets based on silage of a brown midrib or a standard maize hybrid.

The aim of the present experiment was to investigate an experimental brown midrib (Bm) maize hybrid in comparison with a control (Con) non-Bm maize hybrid on ruminal and total tract digestibility, ruminal fermentation, ruminal ingesta kinetics, nitrogen (N) utilisation and microbial efficiency. A total of six ruminally and duodenally cannulated German Holstein cows were used. Animals were fed diets of either 11.5 kg dry matter (DM) of a Con or a Bm maize silage plus 4.1 kg DM of concentrate. Ruminal and total tract digestibility of organic matter, neutral detergent fibre and acid detergent fibre did not differ between hybrids. Short-chain fatty acid concentrations and pH in the rumen were not affected, but ruminal mean retention time was lower for Diet Bm (Con: 45.4 ± 2.39 h; Bm: 40.6 ± 2.39 h; least squares means ± standard error). Cows fed Diet Bm had greater efficiency of N utilisation (Con: 30.1 ± 1.37%; Bm: 33.1 ± 1.37%) and increased flow of microbial crude protein at the duodenum (MCPF) (Con: 7.0 ± 0.37 g/MJ metabolisable energy (ME); Bm: 8.1 ± 0.37 g/MJ ME). Thus, MCPF and utilisable crude protein at the duodenum (uCP) were greater for Diet Bm (MCPF - Con: 1117 ± 52.1 g/d; Bm: 1306 ± 52.1 g/d; uCP - Con: 1594 ± 57.9 g/d; Bm: 1807 ± 57.9 g/d) and ruminal N balance was lower for Diet Bm (Con: 98.7 ± 8.92 g/d; Bm: 65.6 ± 8.92 g/d). The present results show that the Bm maize hybrid might be advantageous for dairy cow nutrition with regard to N utilisation and MCPF. However, further research is necessary to draw more precise conclusions on the potential of Bm maize hybrids in general.

Microbial biomass in faeces of dairy cows affected by a nitrogen deficient diet.

Since more than half of the faecal nitrogen (N) originates from microbial N, the objective of the study was to develop a method for quantitatively detecting microbial biomass and portion of living microorganisms in dairy cattle faeces, including bacteria, fungi and archaea. Three techniques were tested: (1) the chloroform fumigation extraction (CFE) method, (2) detection of the fungal cell-membrane component ergosterol and (3) analysis of the cell wall components fungal glucosamine and bacterial muramic acid. In a second step, an N deficient (ND) and an N balanced (NB) diets were compared with respect to the impacts on faecal C and N fractions, microbial indices and digestibility. The mean values of microbial biomass C and N concentrations averaged around 37 and 4.9 mg g(-1) DM, respectively. Ergosterol, together with fungal glucosamine and bacterial muramic acid, revealed a 25% fungal C in relation to the total microbial C content in dairy cattle faeces. Changes in ruminal N supply showed significant effects on faecal composition. Faecal concentrations of NDF, hemicelluloses and undigested dietary N and the total C/N ratio were significantly higher in ND treatment compared to the NB treatment. N deficiency was reflected also by a higher microbial biomass C/N ratio. It was concluded that the assessment of microbial indices provides valuable information with respect to diet effects on faecal composition and the successive decomposition. Further studies should be conducted to explore the potentials for minimising nutrient losses from faeces.

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 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) and 7 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.

Effect of exogenous fibrolytic enzymes on ruminal fermentation and nutrient digestion in dairy cows.

The aim of the present study was to examine the effects of an exogenous fibrolytic enzyme product applied to a total mixed ration (TMR) prior to feeding on ruminal fermentation, microbial protein synthesis, nutrient digestion, and milk yield and composition. Six multiparous lactating Holstein cows (598 +/- 29 kg initial live weight and 98 +/- 30 days in milk) fitted with rumen and duodenal cannulae were allocated to two treatments in a crossover design over three consecutive 28-d periods. The TMR containing 50% concentrates, 30% corn silage and 20% grass silage on dry matter (DM) basis, was mixed once daily and fed twice a day. Treatments were TMR alone (Control) or TMR with an enzyme product containing primarily cellulase and xylanase activities (9000 U endo-1,4-beta glucanase, 24000 U endo-1,3(4)-beta glucanase and 40000 U 1,4-beta xylanase per ml). The enzyme product was applied at a rate of 6.2 ml/kg TMR (DM basis). It was diluted at a rate of 1:5 with water and applied daily to the TMR. During the control period the cows received a TMR supplemented with 36 ml water/kg TMR on DM basis. Duodenal digesta flow was measured using Cr2O3 as flow marker and microbial protein in the duodenal digesta was estimated by near-infrared spectroscopy (NIRS). There were no significant differences in ruminal pH-values, NH3-N concentrations, total SCFA concentrations and molar proportions of SCFA. No treatment effects on microbial N flow to the duodenum and efficiency of microbial protein synthesis were observed. The apparent ruminal digestibilities of DM, organic matter, NDF and ADF, milk yield and composition were also not affected by the enzyme supplementation. In this study the application of exogenous fibrolytic enzymes fed to dairy cows did not show a significant effect on any parameter tested.

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.

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.

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 cow's 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.

Folic acid in ruminant nutrition: a review.

Folic acid plays an essential role in DNA and methionine metabolism. Micro-organisms in the rumen can synthesise folates, but it has not been verified that these amounts are sufficient to achieve the best efficiency of dairy cows. However, the amount of folates synthesised in the rumen could possibly, to some extent, be affected by the forage:concentrate ratio. Degradation of orally supplemented folic acid in the rumen seems to be very high (about 97%), as supplementation of folic acid hardly increases folate concentrations in the digesta at the duodenum. However, it must be considered that dietary supplements of folic acid higher than 0.5 mg/kg body weight increased serum folate concentrations in all available studies and milk folate concentrations in most studies. Additionally, milk production tended to be increased in some studies. Therefore, degradation of folic acid in the rumen may be overestimated as folates can be absorbed at the proximal duodenum. For future research it is necessary to consider the whole flow and the metabolic pathways of folates from the rumen to duodenum, blood, tissue, milk and transfer to calf to declare requirement values for cows. Consequently, the present review discusses current knowledge and emphasises areas for future research.

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 niacin's mode of action on the metabolism of dairy cows are identified and directions for future research are suggested.

Effect of zeolite A on rumen fermentation and phosphorus metabolism in dairy cows.

The aim of the present study was to determine the effect of zeolite A on several physiological parameters and on mineral metabolism in the rumino-intestinal-tract of cows. Eight double fistulated (rumen and proximal duodenum) cows were fed maize silage, grass silage and concentrate. Zeolite A was added to the ration over a period of three weeks at 0, 10 and 20 g/kg dry matter (DM). The daily feed amounts were adjusted to the current performance and varied between 3.9 and 15.5 kg/d. Rumen fluid, duodenal chyme and faeces were sampled to characterise the nutrient digestibility. Blood samples were taken to analyse the concentration of inorganic phosphate. Zeolite A supplementation led to a significantly reduced ruminal DM digestibility and fermentation of organic matter. The molar proportion of acetate in the rumen increased, and propionate as well as valerate decreased significantly after zeolite A supplementation. The concentration of the total fatty acids and ruminal pH were not affected. No effect on faecal digestion of DM, organic matter nor on calcium and magnesium digestion was observed. Otherwise the phosphorus (P) concentration in rumen fluid correlated negatively with the mean zeolite A intake (r (2) = 0.75; p = 0.0003). Further, the faecal excretion of P increased significantly for cows with the highest zeolite A dosage (36.9 g P/d) compared to the control group (29.9 g P/d). The lower digestibility of P resulted in a significantly decreased concentration of inorganic P in serum from a basal value of 2.05-1.16 mmol/l six days after starting zeolite A supplementation. The zeolite A treated cows showed a significantly higher Al concentration already in rumen fluid (14.31 and 13.84 mmol/l) compared to the control cows (6.33 mmol/l). The Al flow in the duodenum was also higher for zeolite A treated cows.

The influence of an increased cobalt supply on ruminal parameters and microbial vitamin B12 synthesis in the rumen of dairy cows.

The aim of the study was to examine the effects of an elevated dietary cobalt supply to dairy cows on rumen fermentation parameters and microbial vitamin B12 synthesis in the rumen. Five lactating dairy cows fitted with a ruminal and a duodenal cannula were subsequently fed either a ration containing only the native cobalt content (0.17 mg Co/ kg DM) or a ration supplemented with cobalt sulphate (0.29 mg Co/kg DM). The pH-value, the ammonia concentration as well as the concentration and the molar proportions of short chain fatty acids in the rumen were not significantly influenced by feeding the ration with the higher cobalt content. While there was no difference in microbial protein flow, the cobalamin flow at the duodenum was significantly elevated in supplemented animals (3.67 +/- 0.69 vs. 8.63 +/- 2.22 mg B12/d). The efficiency of cobalt utilisation for ruminal vitamin B12 synthesis was calculated to be 7.1 +/- 1.3% for the unsupplemented and 9.5 +/- 2.4% for the supplemented ration. Further investigation has to prove if there are any benefits for cows resulting from the elevated cobalamin synthesis measured, caused by feeding higher amounts of dietary cobalt.

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.

Influence of a Fusarium culmorum inoculation of wheat on the progression of mycotoxin accumulation, ingredient concentrations and ruminal in sacco dry matter degradation of wheat residues.

The Fusarium head blight (FHB)-susceptible winter wheat cv. Ritmo was inoculated with spores of Fusarium culmorum at the beginning of full blossom. Samples of whole wheat plants were taken once weekly from anthesis until harvest and subsequently fractionated into straw, glumes and spindles, which were examined for deoxynivalenol (DON) and zearalenone (ZON). Additionally, the content of crude protein (CP) and non-starch polysaccharides (NSP) was scrutinized. Synthesis of the Fusarium toxins DON and ZON generally differed in terms of date of formation and concentration. Final mean DON concentrations of 37.5, 28.1 and 5.0 mg/kg DM were measured in glumes, spindles and straw, respectively, at the time of harvest. At this time, maximal mean ZON concentrations of 587, 396 and 275 microg/kg DM in spindles, glumes and straw, respectively, were determined. Moreover, Fusarium infected wheat residues contained higher CP but lower NSP contents at the last three sampling dates. In addition, collective samples of wheat straw and chaff were taken to investigate the effect of the Fusarium contamination on their in sacco DM degradation in dairy cows. Samples were analysed for mycotoxins and selected quality parameters. The dried and milled collective samples of straw and chaff were weighed into nylon bags and subjected to ruminal incubation for 4, 8, 16, 24, 48, 72, 96 and 120 h in two dairy cows equipped with a permanent rumen cannula. Marked differences in level of mycotoxin contamination as well as in ingredient composition between the variants of straw and chaff were detected. Moreover, after 120 h rumen incubation the in sacco DM degradation of inoculated straw and chaff were lower compared to the accordant controls. The soluble fraction was increased in inoculated samples, whereas a diminishment in the potentially degradable but insoluble fraction was more pronounced. Thereby, a decrease in the potential degradability was obtained for inoculated straw and even if less pronounced for chaff compared to the non inoculated corresponding controls. In conclusion, infection with F. culmorum of wheat involves an increased risk of mycotoxin contamination in straw. Also, a Fusarium infection may have an impact on chemical composition and may result in Fusarium growth-related modifications of host cell wall components.

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.

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.

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 x 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 A9-desaturase took place. Between 21% and 48% of duodenal t11-C(18:1) were converted into c9, t11-CLA in milk fat.

Feeding value of crambe press cake and extracted meal as well as production responses of growing-finishing pigs and dairy cows fed these by-products.

To analyse the feeding value of crambe press cake (CPC) and crambe extracted meal (CEM), and the incorporation limits in pig diets, a series of balance trials with a total of 12 male castrates was conducted. Additionally, in a feeding trial the effect of 5% and 10% CPC or CEM on growth performance and on pork quality was tested. The CP content of CPC and CEM was 207 and 331 g/kg DM, respectively, and the residual EE 144 and 26 g/kg DM, respectively. The erucic acid concentration amounted to 56% of total fatty acids. Glucosinolate contents were found to be 50 mmol/kg CPC-DM and 70 mmol/kg CEM-DM. The digestibility of OM was 54% for both by-products and the ME contents were 10.6 and 9.3 MJ/kg DM for CPC and CEM, respectively. In the feeding trial, 10% CPC in the diet significantly decreased BWG from 782 g/d (controls) to 742 g/d. Due to glucosinolate intake, the weight of liver, thyroid glands and kidneys was significantly increased. The body fat showed an increased deposition of erucic acid in back fat and intramuscular fat, but changes in sensory properties of the meat were not detected. It is recommended that the incorporation rate of CPC and CEM in diets for growing-finishing pigs should not exceed 5%. The balance experiments, carried out with four wethers each, showed that the OM of CPC and CEM was better digested by ruminants, amounting to 71% or 67%, respectively. The energy content amounted to 7.4 and 6.0 MJ NEL/kg DM, respectively. In the feeding trials with lactating cows, 30% CPC or CEM in the concentrate resulted in a decrease of concentrate intake of about 7%. Due to the high residual fat content of CPC, the milk fat content decreased and the erucic acid content increased. The high glucosinolate intake affected the iodine concentration in the milk. CPC and CEM feeding decreased the iodine content from 271-117 microg/kg and from 182-77 microg, respectively. It is recommended that crambe by-products should not exceed 15% in concentrates or an intake of 1 kg/d for dairy cows.

Effect of glyphosate contaminated feed on rumen fermentation parameters and in sacco degradation of grass hay and corn grain.

Abstract Four rumen fistulated wethers were used to investigate the effect of glyphosate contaminated feed on rumen fermentation. The rations were based on corn silage, urea and a vitamin-mineral premix, either in the absence or presence of 0.77 g glyphosate per kg DM. Furthermore, rations were fed either with or without aromatic amino acid supplementation. During four periods of 28 days, sheep received each of the four dietary treatments according to a Latin square. After 14 days of adaptation rumen fermentation parameters (pH, ammonia, volatile fatty acids) were measured on day 15 over a five-hour period after the morning feeding. The remaining 13 days served for in sacco degradation studies with grass hay and corn grain. Ammonia (NH3) and pH of rumen fluid were within the normal range for all dietary treatments (NH3: 9.1-32.3 mmol x l(- l), pH: 6.2-6.7). Neither rumen fermentation parameters nor in sacco DM and NDF degradation of incubated feedstuffs were significantly affected by glyphosate, with or without aromatic amino acid supplementation. Kinetic profiles of the in sacco dry matter and NDF degradation of grass hay were almost identical for the dietary treatments.

New recommendations for the energy and nutrient supply of dairy cows and heifers in Germany.

In summary, GfE (2001) give not only a view on energy and nutrient requirements, and the official recommendations for supply in Germany established by the Society of Nutrition Physiology, but also a comprehensive literature review on the particular issues. Some gaps of knowledge on requirements of dairy cows and heifers were identified and the need of further research was determined. The derivation of the new recommendations under consideration of physiological aspects has been demonstrated in the paper.