No carry over of unmetabolised deoxynivalenol in milk of dairy cows fed high concentrate proportions

To examine the carry over of deoxynivalenol (DON) and its metabolite de-epoxy DON (DOM-1) in milk, lactating German Holstein cows (n = 13) were fed an isoenergetic total mixed ration in Period 1 with 50% concentrates and 5.3 mg DON/kg dry matter (DM) over 11 wk and were compared with control cows (n = 14). In Period 2 (18 wk), an elevated concentrate proportion was compared to a low concentrate ration by dividing the cows into four Groups (n = 8): Control-30 (30% concentrates), Myco-30 (30% concentrates, 4.4 mg DON/kg DM), Control-60 (60% concentrates) and Myco-60 (60% concentrates, 4.6 mg DON/kg DM). Taken both periods together, no unmetabolised DON was detected in milk samples using the HPLC-UV method. DOM-1 concentrations ranged between below the LOD and 3.2 microg/kg milk in mycotoxin fed cows, while control cows did not excrete any measurable amounts of DOM-1. Regarding the concentrate effects, the carry over of DON as DOM-1 in milk was negligible (between 0.0001 and 0.0011) but significantly higher in Group Myco-30 than in Group Myco-60. This effect may result from an altered bioavailability of DON from maize silage which made up a higher proportion of the daily ration.     

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 microg ZON kg(-1) dry matter (DM)) was replaced by the control wheat (0.25 mg DON kg(-1) and 51 microg 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 microg ZON kg(-1) DM. Feed intakes were adjusted to the current performance of the individual cows. The ZON metabolites alpha-zearalenol (alpha-ZOL) and beta-zearalenol (beta-ZOL) were recovered at the duodenum beside the parent toxin ZON. The recovery of ingested ZON as ZON plus alpha-ZOL plus beta-ZOL at the duodenum ranged between 19 and 247%. The portion of ZON (ranging from 29 to 99%) of the ZON plus alpha-ZOL plus beta-ZOL flow at the duodenum increased significantly with increasing ZON feed intake, whereas the portion of beta-ZOL (up to 57%) decreased significantly. In contrast, portions of ZON in faeces (32-100%), alpha-ZOL (up to 39%) and beta-ZOL (up to 43%) of ZON plus alpha-ZOL plus beta-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, alpha-ZOL and beta-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 microg and 5.6 and 20.5 kg day(-1), respectively, and milk yields (fat corrected milk, FCM) between 10 and 42 kg day(-1).     

Annual variation of deoxynivalenol in Danish wheat flour 1998-2003 and estimated daily intake by the Danish population

The occurrence of deoxynivalenol (DON) in Danish wheat flour was studied during the period 1998-2003 by either capillary gas chromatography with electron capture detection and liquid chromatography coupled to an ion trap mass spectrophotometer. A total of 151 samples were collected from mills and the retail market in Denmark. Contamination levels varied considerably from year-to-year with the highest concentrations occurring in samples from the 2002 harvest with mean and median concentrations of 255 and 300 µg kg^-1, respectively. Compared to other harvest years, 2002 had the highest amount of precipitation around flowering time, i.e. from the end of June to the beginning of July covering weeks 25-27. The lowest average levels were found in samples from the 2001 harvest, where weeks 25-27 were dry compared with other harvest years. The highest value (705 µg kg^-1) was obtained in a flour sample from the 2002 harvest, but none of the tested samples exceeded the maximum limit of 750 µg kg^-1, which has been recently introduced by the European Commission for DON in flour used as raw materials in food products. Calculation of chronic or usual intake by a deterministic approach showed that intake did not exceed the TDI of 1 µg kg^-1 bw day^-1 either for the whole population or for children. A probabilistic approach also showed that intake in general was below the TDI, but intake for children in the 99% percentile amounted to more than 75% of the TDI. The highest intake is calculated to be 2.5 µg kg^-1 bw day^-1.     

Effects of increasing amounts of dietary wheat on performance and ruminal fermentation of Holstein cows

Twelve second-lactation Holstein cows were used in a replicated Latin square design to examine the effects of dietary wheat on lactation performance, ruminal fermentation, and whole-tract nutrient digestibility. Cows were randomly assigned to 1 of 3 diets containing 0, 10, and 20% steam-rolled wheat on a dry matter basis at the expense of steam-rolled barley. Cows were fed and milked twice daily. Six of the cows were ruminally cannulated, and rumen fluid samples were obtained from these cows 18 times during the last 2 d of each period. Treatment did not affect dry matter intake (20.9 kg/d) or yields of milk (36.1 kg/d) or milk components (1.25, 1.10, and 1.67 kg/d for fat, protein, and lactose, respectively). Fat percentage was not different among the treatments but protein content of the milk was reduced by the wheat treatments, and was lower when 10% wheat was included in the diet versus 20%. Cows fed wheat had lower ruminal pH (6.36 vs. 6.44) and greater NH₃-N (11.49 vs. 8.10 mg/dL) and total volatile fatty acids (121 vs. 113 mM) concentrations than cows not fed wheat. The acetate:propionate ratio was lower for cows fed wheat than for those not fed wheat (3.21 vs. 3.36), but was not different between cows fed 10% versus 20% wheat. Wheat feeding did not alter whole-tract apparent digestibility of dry matter, crude protein, acid detergent fiber, and neutral detergent fiber. Results of this study show that up to 20% steam-rolled wheat can be included in the diet of dairy cows without compromising production or causing subacute ruminal acidosis if adequate fiber is provided and the diets are properly formulated and mixed.     

Adaptation responses in milk fat yield and methane emissions of dairy cows when wheat was included in their diet for 16 weeks

Short-term studies have shown that feeding dairy cows diets containing a high proportion (>40%) of wheat may result in reduced milk fat concentration and reduced CH₄ emissions (g of CH₄/cow per d), but no long-term studies have been done on these responses. This study compared the milk production and CH₄ responses when 24 dairy cows were fed diets containing high proportions of either wheat or corn over 16 wk. Cows were assigned to 2 groups and offered a diet (CRN) containing 10.0 kg of dry matter/d of crushed corn grain, 1.8 kg of dry matter/d of canola meal, 0.2 kg of dry matter/d of minerals, and 11.0 kg of dry matter/d of chopped alfalfa hay or a similar diet (WHT) in which wheat replaced the corn. Dry matter intake and milk yields of individual cows were measured daily. Methane emissions from individual cows were measured using controlled climate respiration chambers over 2 consecutive days during each of wk 4, 10, and 16. Milk composition was measured on the 2 d when cows were in chambers during wk 4, 10, and 16. Over the 16-wk experimental period, total dry matter intake remained relatively constant and similar for the 2 dietary treatment groups. At wk 4, CH₄ emission, CH₄ yield (g of CH₄/kg of dry matter intake), milk fat yield, and milk fat concentration were substantially less in cows fed the WHT diet compared with the same metrics in cows fed the CRN diet; but these differences were not apparent at wk 10 and 16. The responses over time in these metrics were not similar in all cows. In 4 cows fed the WHT diet, CH₄ yield, milk fat concentration, and milk fat yield remained relatively constant from wk 4 to 16, whereas for 5 fed the WHT diet, their CH₄ emissions, milk fat yields, and milk fat concentrations almost doubled between wk 4 and 16. In the short term (4 wk), the inclusion of approximately 45% wheat instead of corn in the diet of cows resulted in reductions of 39% in CH₄ yield, 35% in milk fat concentration, and 40% in milk fat yield. However, these reductions did not persist to wk 10 or beyond. Our data indicate that cows do not all respond in the same way with some “adaptive” cows showing a marked increase in CH₄ yield, milk fat concentration, and milk fat yield after wk 4, whereas in other “nonadaptive” cows, these metrics were persistently inhibited to 16 wk. This research shows that short-term studies on dietary interventions to mitigate enteric CH₄ emissions may not always predict the long-term effects of such interventions.     

Effect of electron-beam irradiation on the safety and quality of Fusarium-infected malting barley

Utilization of Fusarium-infected barley for malting may lead to mycotoxin production during malting and decreased malt quality. Electron-beam irradiation may prevent safety and quality defects and allow use of otherwise good quality barley. We evaluated electron-beam irradiation for preventing Fusarium growth and mycotoxin production while maintaining barley-malt quality characteristics. Four barley lots with varying deoxynivalenol (DON) concentrations were irradiated at 0, 2, 4, 6, 8, and 10 kGy. Treated barley was malted in a pilot-scale malting unit. Barley and malt were analyzed for Fusarium infection (FI), germinative energy (GE), aerobic plate counts (APC), mold and yeast counts (MYC), and DON. Malt quality parameters included malt extract, soluble protein, wort color, wort viscosity, free amino nitrogen, alpha-amylase, and diastatic power. FI, APC, and MYC decreased in barley with an increase in dosage. The APC and MYC for malts from barley exposed to 8–10 kGy were slightly higher than in other malted samples indicating that irradiation-resistant microflora could flourish during malting. Barley GE significantly decreased (3–15%) at 8–10 kGy. Although irradiation had no effect on DON in raw barley, DON decreased significantly (60–100%) in finished malts prepared from treated barley (6–10 kGy). Malt quality parameters were slightly affected by electron-beam radiation. The results suggest 6–8 kGy may be effective for reducing FI in barley and DON in malt with minimal effects on malt quality.     

Effect of dietary fat supplementation on methane emissions from dairy cows fed wheat or corn

Diets that contain high proportions of either wheat or supplementary fat have been individually reported to reduce enteric methane production. The objective of this research was to determine the effect of dietary fat supplementation on methane emissions and milk yield from cows fed diets containing either corn or wheat grains. It was hypothesized that cows fed a diet containing wheat would produce less methane and have lower methane yield (methane per kg of dry matter intake; MY) than cows fed a diet containing corn and that methane mitigation from fat supplementation would occur irrespective of the type of grain in the basal diet. The experiment involved 32 Holstein-Friesian dairy cows allocated to 1 of 4 treatment groups (n = 8) and individually fed different diets restricted to approximately 90% of their mean ad libitum intake measured during a covariate period. All animals were offered 11.5 kg of dry matter/d of alfalfa hay, 1.8 kg of dry matter/d of solvent-extracted canola meal, and 1 of 4 dietary supplements. Dietary supplements were 8 kg of dry matter/d of either corn or wheat, or these same treatments with the addition of 0.8 kg of canola oil. In this 5-wk experiment, d 1 to 7 served as the covariate period, d 8 to 14 as the transition period, d 15 to 28 as the adaptation period, and d 29 to 35 as the experimental period. Cows were fed their full treatment diets from d 15 to 35 during which time milk production and feed intake were measured daily. During d 29 to 35, methane production was measured for individual cows daily using the sulfur hexafluoride tracer method. The resulting averages for milk production and feed intake were analyzed by analysis of covariance with factorial grain by fat as treatment structure, animal as the unit within blocks, and the corresponding milk production or feed intake covariate averages as principal covariate. Data on milk fatty acids, ruminal fluid data on pH, ammonia, volatile fatty acids, protozoa, and methane were analyzed by ANOVA using the same treatment and blocking structures excluding the principal covariate. Cows fed a diet containing wheat had greater MY than cows fed a diet containing corn. Irrespective of the type of grain in the diet, increasing the fat concentration from 2 to 6% dry matter reduced MY. It is concluded that the grain component in the basal diet does not affect the mitigating effects of dietary fat supplements on MY.     

Effects of feedborne Fusarium mycotoxins on the performance, metabolism, and immunity of dairy cows

Little is known about the effects of feedborne Fusarium mycotoxins on the performance, metabolism, and immunity of dairy cattle. A total mixed ration (TMR) containing a blend of feedstuffs naturally contaminated with Fusarium mycotoxins was fed for 56 d to 18 midlactation Holstein cows (average milk production, 33 kg/d) in a completely randomized design with repeated measures that included 3 treatments: 1) a control diet, 2) a contaminated diet, and 3) a contaminated diet + 0.2% polymeric glucomannan mycotoxin adsorbent (GMA). Wheat, corn, and hay were the contaminated feedstuffs used in the study. Deoxynivalenol was the major contaminant and was found in the TMR at levels of up to 3.6 μg/g of dry matter. Body weight, body condition score, dry matter intake, net energy balance, milk production, milk composition, somatic cell count, blood serum chemistry, hematology, serum Ig concentrations, and coagulation profile were measured. Dry matter intake and body weight, as well as milk production, milk composition, and SCC, were not affected by diet. Total serum protein and globulin levels increased significantly in cows fed the contaminated TMR compared with cows fed the control diet at 42 d, whereas the albumin:globulin ratio decreased. Serum urea concentrations were significantly elevated throughout the experiment in cows fed the contaminated diet compared with those fed the control diet. Serum IgA concentrations decreased significantly in cows fed the contaminated TMR at 36 d of feeding. Feeding GMA prevented these effects. Serum sodium concentration and osmolality levels were increased throughout the experiment in all cows fed the contaminated diets. We concluded that feed naturally contaminated with Fusarium mycotoxins can affect the metabolic parameters and immunity of dairy cows and that GMA can prevent some of these effects.     

Comparison of full-fat corn germ, whole cottonseed, and tallow as fat sources for lactating dairy cattle

Twenty-four multiparous Holstein cows (124 ± 39 d in milk; 682 ± 72 kg of body weight) were used in 6 simultaneous 4 × 4 Latin squares to evaluate full-fat corn germ as a fat source for lactating dairy cows. Experimental diets were a control (containing 28% ground corn, 23% alfalfa hay, 19% wet corn gluten feed, and 10% corn silage, dry matter basis), and 3 diets with either whole cottonseed (WCS), tallow (TAL), or full-fat corn germ (FFCG) added to provide 1.6% supplemental fat. Cows were fed twice daily for ad libitum intake. Dry matter intake, milk yield, and energy-corrected milk did not differ among diets. Efficiency of milk production (energy-corrected milk/dry matter intake) was greater for cows fed WCS than for cows fed the control, TAL, or FFCG. Milk fat percentage from cows fed FFCG was less than that of cows fed WCS or the control, but was similar to that of cows fed TAL. Milk protein percentage was less for cows fed FFCG than for those fed the control. Total saturated fatty acids were less in milk from cows fed fat sources, and cows fed WCS and TAL had greater saturated fatty acids in milk than did cows fed FFCG. Unsaturated fatty acids were greater in milk from cows fed FFCG than in milk from cows fed the control, WCS, or TAL. The cis-9, trans-11 conjugated linoleic acid content was greater in milk from cows fed WCS, TAL, and FFCG than from cows fed the control, and it was greater in milk from cows fed FFCG than in milk from cows fed WCS or TAL. These results indicate that FFCG can be used effectively as a fat source in diets for lactating dairy cattle.     

Effects of neutral detergent fiber and roughage source on dry matter intake and milk yield and composition of dairy cows

Data were from 20 experiments that utilized early to midlactation Holstein cows fed complete mixed diets or fed at constant forage:concentrate ratios. Within-cow diet comparisons (1688 cow-periods) were analyzed by least squares analysis of variance; mathematical model included experiment, cow in experiment, period, body weight, and source of roughage. Objectives were to determine relationships between neutral detergent fiber content of diet and milk yield and dry matter intake. Roughages and number of cow-periods were: sugarcane bagasse/silage (507), cottonseed hulls (504), corn silage (268), ground corrugated boxes (170), alfalfa/peanut hay (132), and others (107). Dry matter intake and estimated net energy intake had linear effects on milk yield and explained 21.6 and 24.0% of its residual variation; milk yield had curvilinear (quadratic) effect and explained 22.4% of dry matter intake residual variation. Interaction between neutral detergent fiber and source of roughage on milk yield, 4% fat-corrected milk, and dry matter intake resulted in reductions of 5.6, 5.6, and 13% in residual variations. Results suggest neutral detergent (% of dry matter) has greater effect on dry matter intake than on milk yield and its use in formulating diets for dairy cows will be within roughage source.     

Impact of mechanical shelling and dehulling on Fusarium infection and fumonisin contamination in maize

Mechanical shelling and dehulling methods were tested to evaluate their impact on Fusarium infection and fumonisin contamination in maize. All shelling methods which were tested were found to damage the grains. The IITA® sheller caused the highest level (up to 3.5%) of damage. Fusarium populations were higher on damaged grains, the highest being recorded from grains damaged by the IITA® sheller (2533.3 cfu g^-1). Fumonisin levels were higher in damaged grains, the highest being in maize shelled with the IITA® sheller (2.2 mg kg^-1). Fumonisin levels were positively and significantly correlated with the percentage of damage caused by the shelling methods, and with the number of Fusarium colonies in maize. Mechanical dehulling methods significantly reduced fumonisin levels in maize, resulting in a mean reduction of 62% for Mini-PRL, 65% for Engelberg, and 57% for the attrition disc mill. It is important for farmers to choose appropriate shelling methods to reduce mycotoxin contamination. Dehulling should be widely promoted for the reduction of mycotoxins in maize.     

Characterization and application of isotope-substituted (13C15)-deoxynivalenol (DON) as an internal standard for the determination of DON

The powerful combination of liquid chromatography and mass spectrometry (MS) is often limited by matrix effects during ionization in the MS ion source. The use of fully isotope-substituted (¹³C₁₅)-deoxynivalenol ((¹³C₁₅)-DON) as an internal standard (IS) corrects matrix effects and improves the accuracy of analytical methods using mass spectrometry for the quantitative determination of the Fusarium mycotoxin deoxynivalenol (DON). The IS was characterized with respect to its chromatographic purity by liquid chromatography-ultraviolet light and its isotope distribution by time-of-flight mass spectrometry. Its low-energy collision-induced dissociation behaviour was compared with DON. Moreover, this work describes the successful application of (¹³C₁₅)-DON as IS for the determination of DON in maize using high-performance liquid chromatography (HPLC) electrospray (ESI) with tandem mass spectrometry. The results demonstrate that the IS can successfully correct for fluctuations during extraction and clean-up of the sample as well as the ionization of DON in the MS ion source. Random variations in ionization affect the IS in the same way as the analyte. Recoveries for DON in maize of 76% ± 1.9% (external calibration) or 101% ± 2.4% (internal calibration) were reached, respectively, after sample clean-up.     

Effect of whole and expanded-expelled cottonseed on milk yield and blood gossypol

Thirty-two primiparous and 12 multiparous Holstein cows were randomly assigned at calving to treatments to determine the effects of type and amount of cottonseed product on plasma gossypol, milk production, and composition, and conjugated linoleic acid concentration in milk fat. Rations consisted of corn silage, corn grain, soybean meal, and cottonseed hulls, and contained on average 16.8% crude protein and 25.3% acid detergent fiber on a dry matter basis. On a dry matter basis, diets contained one of the following: 1) 14% whole cottonseed; 2) 14% expanded-expelled cottonseed; 3) 21% expanded-expelled cottonseed; or 4) 28% expanded-expelled cottonseed. Cows remained on treatment from 30 through 120 d in milk. Dry matter intakes were not significantly different, but intakes of crude protein, acid detergent fiber, and fat were higher for multiparous cows fed whole cottonseed. Multiparous cows fed whole cottonseed had higher yields of milk, fat-corrected milk, crude protein, fat and solids-not-fat than those fed any level of expanded-expelled cottonseed. Concentrations of milk fat, protein, and SNF were not affected by treatment. Although there were treatment differences in fat intake, there were no production differences in primiparous cows. Milk production efficiency (fat-corrected milk/dry matter intake) was not affected by treatment for either multiparous or primiparous cows. Cows fed 14% whole or 14% expanded-expelled cottonseed had similar levels of total plasma gossypol and plasma levels of the negative isomer of gossypol. Increasing the level of expanded-expelled cottonseed in the diet increased both total plasma gossypol and the negative isomer. In this experiment, multiparous but not primiparous cows fed whole cottonseed produced more milk than those fed expanded-expelled cottonseed at 14 to 28% of the diet dry matter, however, feed efficiencies were similar for all treatments.     

Fibrolytic enzyme supplements for dairy cows in early lactation.

Twenty multiparous lactating Holstein cows in early lactation were used to investigate effects of exogenous fibrolytic enzyme supplementation on dry matter intake, milk production, and digestibility. Cows were blocked according to parity, expected calving date, and milk yield in the previous lactation, and then randomly assigned after calving to two treatments: control or enzyme. The enzyme mixture, which contained mainly xylanase and cellulase activities (Pro-Mote, Biovance Technol. Inc., Omaha, NE), was added to the concentrate to supply 1.3 g/kg of total mixed ration (dry matter basis). The total mixed rations contained 24% corn silage, 15% alfalfa hay, and 61% barley concentrate (dry matter basis) and were offered for ad libitum intake. Enzyme addition did not affect dry matter intake. However, total digestibility of nutrients, determined using Cr2O3, was dramatically increased by enzyme treatment (dry matter, 61.7 vs. 69.1%; neutral detergent fiber, 42.5 vs. 51.0%; acid detergent fiber, 31.7 vs. 41.9%; crude protein, 61.7 vs. 69.8%). Consequently, milk yield tended to increase (35.9 vs. 39.5 kg/d). Percentage of milk fat was lower, and percentages of milk protein tended to be lower for cows fed a diet supplemented with enzymes, such that component yields were similar for cows fed either diet. Energy deficiency was numerically lower for cows fed a diet supplemented with enzymes than for cows fed the control diet (-3.62 vs. -3.33 Mcal/d). Supplementing dairy cow diets with a fibrolytic enzyme mixture has the potential to enhance milk yield and nutrient digestibility of cows in early lactation without changing feed intake.     

Influence of a reduced-starch diet with or without exogenous amylase on lactation performance by dairy cows

The objective of this trial was to determine lactation performance responses in high-producing dairy cows to a reduced-starch versus a normal-starch diet and to the addition of exogenous amylase to the reduced-starch diet. Forty-five multiparous Holstein cows, 68 ± 29 d in milk and 696 ± 62 kg of body weight (BW) at trial initiation, were randomly assigned to 1 of 3 treatments in a completely randomized design; a 2-wk covariate adjustment period with cows fed the normal-starch diet was followed by a 10-wk treatment period with cows fed their assigned treatment diets. The normal-starch total mixed ration did not contain exogenous amylase (NS−). The reduced-starch diets, formulated by partially replacing corn grain and soybean meal with whole cottonseed and wheat middlings, were fed without (RS−) and with (RS+) exogenous amylase addition to the total mixed ration. All diets contained 50% forage and 19.8% forage neutral detergent fiber (dry matter basis). Starch and neutral detergent fiber concentrations averaged 27.0 and 30.9%, 22.1 and 35.0%, and 21.2 and 35.3% (dry matter basis) for the NS−, RS−, and RS+ diets, respectively. Expressed as a percentage of BW, dry matter intake was greater for cows fed RS− than for cows fed NS− or RS+. Intake of neutral detergent fiber ranged from 1.09 to 1.30% of BW among the treatments, with that of RS− being 21% greater than that of NS−. Milk yield tended to be greater for cows fed NS− compared with the RS diets. Milk fat content and yield were unaffected by treatment. Milk protein content and yield were greater for cows fed NS− compared with the RS diets. Concentrations of milk urea nitrogen were greater for cows fed RS diets compared with the NS− diet. Body weight, BW change, and body condition score were unaffected by treatment. Feed conversion (kg of milk/kg of dry matter intake) was 10% greater on average for cows fed NS− than for cows fed the RS diets, and tended to be 6% greater for cows fed RS+ compared with RS−. Feeding a reduced-starch diet formulated by partially replacing corn grain and soybean meal with a wheat middlings and whole cottonseed mixture compared with a normal-starch diet without addition of exogenous amylase to either diet reduced milk and component-corrected feed conversions. Addition of exogenous amylase to a reduced-starch diet was of minimal benefit in this study.     

Effects of feeding synthetic zeolite A during the prepartum period on serum mineral concentration,oxidant status,and performance of multiparous Holstein cows

The objective of this study was to determine the effects of feeding synthetic zeolite A for 3 wk before expected calving on peripartal serum mineral concentrations, hypocalcemia, oxidant status, and performance. Holstein cows (n = 55) entering their second or greater lactations were assigned randomly to 1 of 2 dietary treatments starting 21 d before expected calving: control (CON: 40% corn silage, 33% wheat straw, and 27% concentrate; n = 29) or experimental [EXP: CON plus zeolite A (X-Zelit, Protekta Inc., Lucknow, ON, Canada/Vilofoss, Graasten, Denmark; n = 26) at an inclusion rate of 3.3% of dry matter, targeting 500 g/d as-fed]. Cows were fed the same postpartum diet and housed in individual tiestalls through 28 d in milk. Cows fed EXP had higher serum Ca concentrations as parturition approached and during the immediate postpartum period. Serum P concentrations were lower for the EXP-fed cows during the prepartum period and the first 2 d of lactation, whereas serum Mg concentrations were lower than those of the CON-fed cows only during the immediate periparturient period. Cows fed EXP had decreased prevalence of subclinical hypocalcemia (SCH) from d −1 through 3 relative to day of parturition, with the largest difference occurring within the first day postpartum. Prepartum dry matter intake tended to be decreased and rumination was decreased in cows fed EXP; however; postpartum dry matter intake, rumination, milk yield, milk component yield, and colostrum measurements did not differ between treatments. Cows fed EXP tended to have increased hazard of pregnancy by 150 d in milk when controlling for parity compared with CON-fed cows; potential reproductive benefits merit further study. This study demonstrated that zeolite A supplementation during the prepartum period results in markedly improved serum Ca concentrations around parturition and similar postpartum performance compared with controls and is effective at decreasing hypocalcemia in multiparous Holstein cows.     

Acrylamide-occurrence in mixed concentrate feed for dairy cows and carry-over into milk

During the preparation of cooked foods acrylamide is formed from asparagine and reducing sugars at high temperatures. By-products of oil, starch and sugar production, which may be found in animal feed, partially result from processing steps using heat treatment that are similarly likely to form acrylamide. Possibly, pelletizing during the processing of mixed concentrates may also be involved in acrylamide formation. Thus the occurrence of acrylamide in animal feed and the potential for carry-over into animal products should be tested. Independently of the feed matrix, 1.5 g per day of acrylamide was fed to a cow for ten days resulting in a mean concentration of 175 µg/kg of acrylamide in the milk. From the data obtained the mean carry-over was found to be 0.24%, and a mean half-life time of 2.8 h was estimated. This means acrylamide was rapidly transformed in the cow. The acrylamide concentrations in three commercial mixed concentrates were respectively 180, 145 and 140 µg/kg feed. To test the possible effect of pelletizing, the peripheral zones were separately analysed. No difference in concentration was observed. Based on the carry-over rate estimated in this study, a maximum concentration of approx. 0.2 µg/kg of acrylamide would be expected in milk from cows fed with such feeds.     

The effect of the forage-to-concentrate ratio of the partial mixed ration and the quantity of concentrate in an automatic milking system for lactating Holstein cows

This study was conducted to evaluate the effects of the forage-to-concentrate ratio of the partial mixed ration (PMR) and the quantity of concentrate offered in an automated milking system (AMS), in a feed-first guided-flow barn, on the behavior and performance of dairy cows. Eight ruminally cannulated multiparous Holstein cows were used in a replicated 4 × 4 Latin square balanced for carry-over effects. Treatments were arranged in a 2 × 2 factorial consisting of a PMR that contained (dry matter basis) either a low (54:46; L-FOR) or a high (64:36; H-FOR) forage-to-concentrate ratio and AMS concentrate provision to achieve low (2 kg/d; L-AMS) or high (6 kg/d; H-AMS) intake. Each period consisted of 28 d with 6 d for dietary transition, 13 d for adaptation, and 9 d of collection. The first 4 d of data and sample collection were used to evaluate behavioral data (milking frequency, feeding behavior, and standing and lying behavior) and ruminal pH. Subsequently, a sampling device removal day was provided, and the last 4 d were used to evaluate ruminal fermentation and apparent total-tract digestibility. All 9 d were used for milk yield measurement, and the 8 d were used for dry matter intake measurement. Cows fed the H-AMS consumed 3.5 kg/d less PMR while consuming 4.2 kg/d more AMS concentrate, but total dry matter intake (PMR+AMS) was not affected by treatments averaging 27.3 kg/d. Although cows fed H-AMS had greater concentrate intake, they also had greater variability for AMS concentrate intake among days (0.85 vs. 0.25 kg/d, respectively). The number of PMR meals and PMR eating behavior were not affected by the PMR or AMS treatments. Feeding H-AMS did not affect milking frequency averaging 3.63 milkings/d, but tended to increase milk yield by 1.25 kg/d relative to L-AMS. Likewise, cows fed the L-FOR tended to have greater milk yield relative to H-FOR (39.3 vs 37.9 kg/d, respectively), but had greater holding area time. Minimum ruminal pH tended to be lower for cows fed L-FOR compared with cows fed H-FOR but was not affected by the AMS concentrate treatment. When fed the L-FOR, feeding the H-AMS increased total short-chain fatty acid concentration in the rumen relative to cows fed L-AMS, whereas the response for H-FOR was not affected by the AMS concentrate. These data suggest that feeding H-AMS may improve milk yield, but also increases the day-to-day variability in AMS concentrate consumption. Feeding a L-FOR PMR may increase milk yield without affecting variability in AMS concentrate consumption; however, it may reduce ruminal pH and increase the time spent in the holding area compared with cows fed a H-FOR PMR.     

Influence of a novel bm3 corn silage hybrid with floury kernel genetics on lactational performance and feed efficiency of Holstein cows

Dry matter intake, lactation performance, and chewing behavior of multiparous Holstein cows (n = 15) fed diets containing a novel bm3 corn silage hybrid with floury kernel genetics were compared with cows fed diets containing commercially available conventional and bm3 hybrids using a replicated 3 × 3 Latin square design with 28-d periods. Cows were housed in tiestalls, milked 3 times/d, and fed a total mixed ration containing 49.0% (dry matter basis) of (1) a conventional corn silage hybrid (CONV); (2) a brown midrib bm3 hybrid (BMR); or (3) a bm3 hybrid with floury kernel genetics (BMRFL). All diets contained 6.3% hay crop silage and 44.7% concentrate. Dietary nutrient composition averaged 32.7% neutral detergent fiber (NDF) and 26.3 starch (% of dry matter). Data were analyzed by ANOVA using the MIXED procedure in SAS (SAS Institute Inc., Cary, NC). The dry matter intake was greater for cows fed BMR (28.0 kg/d) compared with CONV (26.8 kg/d), whereas dry matter intake for cows fed BMRFL was intermediate (27.6 kg/d). Energy-corrected milk (ECM) yield was greater for cows fed BMR (50.3 kg/d) and BMRFL (51.8 kg/d) compared with CONV (47.2 kg/d). Milk fat yield was higher for cows fed BMRFL (1.87 kg/d) compared with CONV (1.74 kg/d) and BMR (1.80 kg/d). Milk protein yield was greater for cows fed BMR (1.49 kg/d) and BMRFL (1.54 kg/d) compared with CONV (1.36 kg/d). Milk urea-N was reduced for cows fed BMR (11.61 mg/dL) and BMRFL (11.16 mg/dL) compared with CONV (13.60 mg/dL). Feed efficiency (ECM/dry matter intake) was higher for cows fed BMRFL (1.87) compared with CONV (1.76) and BMR (1.79). Milk N efficiency was greatest for cows fed BMRFL (40.4%) followed by BMR (38.1%) and finally CONV (35.3%). Cows fed CONV chewed 5 min more per kilograms of NDF consumed than cows fed either of the BMR hybrids. No differences were observed among diets in apparent total-tract digestibility of NDF (58.1%) or starch (99.3%). Overall lactational performance was enhanced for cows fed diets containing both BMR and BMRFL hybrids versus CONV. In addition, feeding the BMRFL corn silage improved efficiency of component-corrected milk production and milk N efficiency compared with the CONV and BMR silages.     

Effects of feeding a high-fiber byproduct feedstuff as a substitute for barley grain on rumen fermentation and productivity of dairy cows in early lactation

The objective of the study was to evaluate effects of partial substitution of dietary grain with wheat dried distillers grains with solubles (DDGS) on dry matter intake (DMI), sorting behavior, rumen fermentation, apparent total-tract nutrient digestibility, plasma metabolites, and milk production of dairy cows in early lactation. Sixty-one Holstein cows, including 13 ruminally cannulated cows, were blocked by parity and calving date and assigned to 1 of 2 experimental diets immediately after calving until 12 wk in lactation. The control (CON) diet contained 43% barley silage, 17.3% dry-rolled barley grain, and 39.7% concentrate mix on a dry matter basis, and wheat DDGS replaced dry-rolled barley grain in the DDGS diet. Dietary starch content was 29.2 and 19.1% for CON and DDGS diets, respectively. Despite the 10-percentage-unit difference in dietary starch content, cows fed the DDGS diet did not increase ruminal pH. A significant treatment by parity interaction was observed for DMI; feeding the DDGS diet decreased DMI of multiparous cows compared with CON (20.1 vs. 21.3 kg/d) but increased that of primiparous cows (16.2 vs. 14.7 kg/d). Although milk yield was not affected by treatment, cows fed the DDGS diet had lower apparent total-tract digestibility of starch compared with CON (81.9 vs. 91.2%) and tended to have higher plasma concentrations of nonesterified fatty acids (173 vs. 143 mEq/L). High-fiber byproduct feedstuffs such as wheat DDGS can be used as a partial substitute for grains in diets of dairy cows in early lactation but the substitution may not mitigate rumen acidosis problems and may decrease energy intake of multiparous cows in early lactation.