Feeding genetically modified maize (MON810) to dairy cows: comparison of gene expression pattern of markers for apoptosis, inflammation and cell cycle

Public concern has been expressed on the use of genetically modified (gm) maize MON810 as animal feed and for human consumption. Several studies have been conducted on potential effects of feeding MON810 to livestock focusing on animal performance, animal health and fate of recombinant DNA or protein. Though, no information on effects of feeding gm maize on the gene expression level is available so far. From 2005 until 2007, a study with 36 lactating dairy cows fed gm maize (N?=?18, MON810) or the near-isogenic counterpart (N?=?18) was carried out, investigating the fate of recombinant DNA and protein. After a period of 25?months, ten cows fed transgenic maize and seven cows fed near-isogenic maize were slaughtered due to operational reasons. In a short follow-up study, tissues of the gastrointestinal tract and samples from liver were used for gene expression analysis of major genes of the inflammation, cell cycle and apoptosis pathways. Statistical analysis of the examined gene expression pattern revealed no significant difference in the gene expression profile of cows fed transgenic or near-isogenic feed ration. Therefore, it can be assumed that compared to near-isogenic feed, gm maize MON810 does not have any effect on major genes involved in apoptosis, inflammation and cell cycle in the gastrointestinal tract and in the liver of dairy cows.     

Effects of feeding rations with genetically modified whole cottonseed to lactating Holstein cows

Two experiments were conducted to evaluate dry matter intake (DMI), milk yield, and milk composition from feeding rations that contained different sources of genetically modified whole cottonseed to Argentinean Holstein dairy cows. Twenty-four lactating multiparous Argentinean Holstein dairy cows were used in 2 experiments with a replicated 4 x 4 Latin square design, with cows averaging 565 kg body weight and 53 d in milk at the beginning of the experiments. Treatments in Experiment 1 were: Bollgard cotton containing the cry1Ac gene, Bollgard II cotton containing cry1Ac and cry2Ab genes, Roundup Ready cotton containing the cp4 epsps gene, and a control nongenetically modified but genetically similar cottonseed. In Experiment 2, two commercial sources, a parental control line, and the transgenic cotton containing both cry1Ac and cp4 epsps genes were used as treatments. All cows received the same total mixed ration but with different whole cottonseed sources. Cottonseed was included to provide 2.50 kg per cow daily (dry matter [DM] basis) or about 10% of the total diet DM. The ingredient composition of the total mixed ration was 32% alfalfa hay, 28% corn silage, 22% corn grain, 17% soybean meal, and 2% minerals and vitamins. In addition, genomic DNA was extracted from a subset of milk samples and analyzed by polymerase chain reaction followed by Southern blot hybridization for small fragments of the cry1Ac transgene and an endogenous cotton gene, acp1. No sample was positive for transgenic or plant DNA fragments at the limits of detection for the assays following detailed data evaluation criteria. The DMI, milk yield, milk composition, body weight, and body condition score did not differ among treatments. Cottonseed from genetically modified varieties used in these studies yielded similar performance in lactating dairy cows when compared to non-transgenic control and reference cottonseed.     

Degradation and possible carry over of feed DNA monitored in pigs and poultry

A possible carry over of foreign food DNA into the body after consumption was examined. After feeding pigs with conventional and recombinant (Bt-) maize, different body samples were investigated using DNA-extraction followed by PCR procedures to detect chloroplast genes of different length (199 bp and 532 bp), a maize-specific gene (zein) and a specific transgene present in Bt-maize (cryIa). Initially, a time-dependent degradation of feed DNA in the gastrointestinal tract of pigs was analysed within the juices from stomach and three parts of the small intestine (duodenum, jejunum, ileum). Subsequently, a possible transfer of residual chloroplast specific DNA as well as recombinant Bt-maize DNA fragments into different pig organs (blood, muscle, liver, spleen and lymph nodes) was examined. The suitability of the introduced DNA extraction procedure was verified through amplification of a universal gene (ubiquitin) demonstrating the successful PCR analysis within a range of 189-417 bp long DNA. Short chloroplast DNA fragments (199 bp) could be successfully amplified from the intestinal juices of pigs up to 12 h after the last feeding. In contrast, chloroplast-specific DNA was not found in any pig organ investigated so far. Specific gene fragments from the transgene maize (Bt-maize) were never detected in any pig sample. A field study examining supermarket poultry samples (leg, breast and wing muscle, stomach) led to frequent detections of the short chloroplast DNA fragment (199 bp). Furthermore, faint signals for the maize specific zein gene fragment were detected in these poultry tissues. Additional PCR examinations using unhatched chicken embryos provided the first indication that neither chloroplast nor maize genes are present endogenously within the wild-type poultry genome. Therefore, a transient transfer of short forage DNA into most poultry organs can be suspected.     

Detection of DNA fragments from wheat in blood of animals

Delivery of foreign DNA is still a very controversial issue, especially in relation to genetically modified organisms. It is not necessary to use genetically modified feed to verify the possible transfer of DNA from food into the body. In this study, we evaluated the possible transfer of DNA from wheat forage (of single component diet) into the blood of three different organisms. DNA isolation kits were used to isolate total DNA from blood and feed. Blood was taken for analysis from rats (after 23 days feeding wheat), broilers (15 days), and carp (34 days). Housekeeping genes were used to verify blood samples (rats: glyceraldehyde-3-phosphate dehydrogenase/GAPDH/, broilers: growth hormone gene/GCH/and carp: small ribosomal subunit/40S/). We used GAPDH and actin to determine whether DNA from wheat was transferred into animal blood. No purple and common wheat DNA fragments were detected in the blood of any animal tested, suggesting no transfer of the tested wheat DNA into the body. Various contents of anthocyanins in the feeding variants had no effect on the transfer of wheat DNA into the blood of animals. Our results correspond to some studies that have not proved transfer DNA from genetically modified feed into the target organism.     

Effect of ethanol in feed on milk flavor and chemical composition

A crossover study was performed using 24 dairy cows to investigate whether pure ethanol in concentrations that could be found in well-fermented silages influenced milk composition or flavor. Cows were fed a standard ration of well-fermented grass silage for ad libitum intake and high moisture barley and a protein concentrate in restricted amounts. A daily dose of ethanol (600 g) was divided into three meals/d and fed with grass silage. When cows received ethanol, milk yields decreased slightly, but milk fat and protein concentrations increased so that energy-corrected milk yield increased by 0.9 kg/d. Milk concentrations of lactose and urea decreased, concentrations of ethanol and acetone increased, concentrations of free fatty acids increased slightly, and alpha-tocopherol concentrations were unaffected. The proportion of palmitic acid in milk fat increased, and the proportion of unsaturated acids decreased. Organoleptic milk quality was reduced because of an increase in milk tainted by feed flavors. The off-flavor could not be attributed solely to the ethanol transmitted to the milk. Precautions should be taken to avoid extensive production of ethanol during fermentation of grass silage and other feeds that are to be fed to dairy cows.     

Detection of feed-derived maize DNA in goat milk and evaluation of the potential of horizontal transfer to bacteria

The presence and the transforming capacity of feed-derived DNA in milk obtained from eight lactating goats fed on maize E176 silage were evaluated. The presence of single- and multi-copy maize genes was monitored by real-time PCR and conventional PCR. Chromosomal and plastid DNA extracted directly from maize flour and silage were readily amplifiable by conventional PCR, however, only chloroplast-specific gene fragments of 199 and 532 bp were detected in about 60 and 20%, respectively, of the milk samples analysed. Quantification by real time PCR yielded 9.5 (±6.7) × 10² plant gene copies/mL of milk sediment. In contrast, all milk samples were negative for the chromosomally located maize zein gene or the E176 specific cry1Ab transgene. The minimum concentration of plant DNA required for detection was 0.01 ng/mL raw milk for the chloroplast-specific fragment and 1 ng/mL for the cry1Ab transgene. The detection limit was determined by spiking milk samples with plant DNA prior to DNA extraction. The transformation capability of DNA in milk was evaluated after constructing a marker rescue system in Acinetobacter baylyi strain BD413 based on recombinational repair of the bla _TEM gene. Two systems were developed that allowed the plant marker gene to recombine with the bacterial chromosome [A. baylyi BD413 (pUC-bla)] or plasmids [A. baylyi BD413 (pBBR1MCS-2Φ)]. The two systems showed the same efficiency of transformation, yielding 10⁻⁵ transformants per recipient cell (t/r) using plasmid pUC18 or a 1,873 bp fragment as donor DNA, and 3.5 × 10⁻¹¹ t/r using DNA isolated from flour (E176). No transformants were detected when exposing the recipient bacterium to DNA extracted from maize (E176) silage or from milk obtained from goats feed maize (E176).     

Feeding concentrates with different protein sources to high-yielding,mid-lactation Norwegian Red cows: Effect on cheese ripening

Soybean meal is one of the most important protein sources in concentrate feeds for dairy cows. The objective of the present study was to provide knowledge on the effects of using a novel yeast microbial protein source (Candida utilis) in concentrate feed for dairy cows on the production and quality of a Gouda-type cheese. Forty-eight Norwegian Red dairy cows in early to mid lactation were fed a basal diet of grass silage, which was supplemented with 3 different concentrate feeds. The protein source of the concentrates was based on conventional soybean meal (SBM), novel yeast (C. utilis; YEA), or barley (BAR; used as negative control because barley has a lower protein content). The experiment was carried out for a period of 10 wk, with the first 2 wk as an adaptation period where all dairy cows were fed grass silage and the SBM concentrate. The cows were then randomly allocated to 1 of the 3 different compound feeds: SBM, yeast, or barley. Cheeses were made during wk 8 and 9 of the experiment, with 4 batches of cheese made from milk from each of the 3 groups. The cheeses made from milk from cows fed SBM concentrate (SBM cheese) had a higher content of dl-pyroglutamic acid and free amino acids than the other cheeses, indicating a faster ripening in the SBM cheeses. Despite these differences, the sensory properties, the microbiota, and the Lactococcus population at 15 wk of ripening were not significantly different between the cheeses. This experiment showed that although the raw materials used in the concentrate feed clearly influenced the ripening of the cheeses, this did not affect cheese quality. Yeast (C. utilis) as a protein source in concentrate feed for dairy cows can be used as a replacement for soybean meal without compromising the quality of Norwegian Gouda-type cheeses.     

Supplying the protein needs of dairy cattle from by-product feeds

Several by-product feeds are relatively high in crude protein and exhibit relatively low ruminal degradability, which make them desirable proteinaceous feeds for dairy cows. Therefore, by-product feeds have been and will continue to be important feeds for dairy cows. Factors are discussed that affect ruminal degradability of protein in distillers grains, distillers grains with solubles, brewers grains, corn gluten feed, corn gluten meal, meat meal, meat and bone meal, blood meal, and fish meal, and the potential of these feeds to provide supplemental amino acids needed by lactating dairy cows. The importance of maximizing synthesis of microbial protein and digestion of organic matter in the rumen is emphasized in relation to total amino acid passage to the small intestine. For these feeds to be used most successfully, they must be available from a dependable source at an economical cost and should supply amino acids that complement other amino acids passing to the small intestine. Benefits that should be realized from the successful use of by-product feeds include increased milk production from feeding proteins that have greater ruminal escape potentials and a reduced cost per unit of milk produced because of decreased use of expensive supplemental protein.     

Polymerase chain reaction (PCR) in the quality and safety assurance of food: Detection of soya in processed meat products

A new method for the specific and sensitive detection of soya (Glycine max) in processed meat products has been developed using polymerase chain reaction (PCR) technology. The presence of soya deoxyribonucleic acid (DNA) from several soya protein concentrates was determined with two pairs of specific oligonucleotides yielding a 414-bp (bp=base pair) fragment and an internal 118-bp fragment amplified from the soya lectinLe1 gene. The test detected DNA from textured soya protein concentrates in meat products at a level of 1% and was confirmed by a commercially available enzyme-linked immunosorbent assay (ELISA).     

植物源食品DNA制备方法的比较研究

目的：探索可用作PCR方法检测和鉴定植物源转基因食品模板的DNA抽提方法。方法：分别用改良CTAB法、SDS法制备黄豆、玉米、土豆和番茄及其加工产品的DNA，PCR扩增叶绿体基因片段及黄豆、玉米的内参照基因lectin和zein10。结果：改良CTAB法所得DNA作为PCR扩增模板，叶绿体基因片段及lectin和zein10均呈阳性，SDS法所得DNA作为模板时，部分样品内参照基因lectin或zein10扩增阴性。结论：PCR方法检测转基因食品时，应用改良CTAB法制备DNA模板。     

Production and economic responses to intensification of pasture-based dairy production systems

Production from pasture-based dairy farms can be increased through using N fertilizer to increase pasture grown, increasing stocking rate, importing feeds from off farm (i.e., supplementary feeds, such as cereal silages, grains, or co-product feeds), or through a combination of these strategies. Increased production can improve profitability, provided the marginal cost of the additional milk produced is less than the milk price received. A multiyear production system experiment was established to investigate the biological and economic responses to intensification on pasture-based dairy farms; 7 experimental farmlets were established and managed independently for 3 yr. Paddocks and cows were randomly allocated to farmlet, such that 3 farmlets had stocking rates of 3.35 cows/ha (LSR) and 4 farmlets had stocking rates of 4.41 cows/ha (HSR). Of the LSR farmlets, 1 treatment received no N fertilizer, whereas the other 2 received either 200 or 400 kg of N/ha per year (200N and 400N, respectively). No feed was imported from off-farm for the LSR farmlets. Of the 4 HSR farmlets, 3 treatments received 200N and the fourth treatment received 400N; cows on 2 of the HSR-200N farmlet treatments also received 1.3 or 1.1 t of DM/cow per year of either cracked corn grain or corn silage, respectively. Data were analyzed for consistency of farmlet response over years using mixed models, with year and farmlet as fixed effects and the interaction of farmlet with year as a random effect. The biological data and financial data extracted from a national economic database were used to model the statement of financial performance for the farmlets and determine the economic implications of increasing milk production/cow and per ha (i.e., farm intensification). Applying 200N or 400N increased pasture grown per hectare and milk production per cow and per hectare, whereas increasing stocking rate did not affect pasture grown or milk production per hectare, but reduced milk production per cow. Importing feed in the HSR farmlets increased milk production per cow and per hectare. Marginal milk production responses to additional feed (i.e., either pasture or imported supplementary feed) were between 0.8 and 1.2 kg of milk/kg of DM offered (73 to 97 g of fat and protein/kg of feed DM) and marginal response differences between feeds were explained by metabolizable energy content differences (0.08 kg of milk/MJ of metabolizable energy offered). The marginal milk production response to additional feed was quadratic, with the greatest milk production generated from the initial investment in feed; 119, 99, and 55 g of fat and protein were produced per kilogram of feed DM by reducing the annual feed deficit from 1.6 to 1.0, 1.0 to 0.5, and 0.5 to 0 t of DM, respectively. Economic modeling indicated that the marginal cost of milk produced from pasture resulting from applied N fertilizer was less than the milk price; therefore, strategic use of N fertilizer to increase pasture grown increased farm operating profit per hectare. In comparison, operating profit declined with purchased feed, despite high marginal milk production responses. The results have implications for the strategic direction of grazing dairy farms, particularly in export-oriented industries, where the prices of milk and feed inputs are subject to the considerable volatility of commodity markets.     

Performance of lactating dairy cows fed silage and grain from a maize hybrid with the cry1F trait versus its nonbiotech counterpart

Effects of feeding grain and maize silage from a non-Bt maize and a variety of Bt maize that contains cry1F (event TC1507, event DAS-Ø15Ø7-1), a gene that provides maize with insect resistance, on the health and performance of dairy cows were evaluated. In a crossover trial, 20 lactating Holstein cows were assigned to each of 2 dietary treatment groups and fed diets containing whole-plant maize silage plus maize grain from TC1507 or its near-isoline counterpart (control). Each period of the crossover trial lasted 28 d and was preceded by a 7-d adjustment period. To minimize variability due to stage of lactation, 2 blocks of 10 cows at 90 to 130 d of lactation at the start of the trial were used. Within each dietary treatment, 10 cows were from each of 2 genetic selection lines (high and average fat plus protein predicted transmitting ability). Diets were formulated to be isocaloric and isonitrogenous. Dry matter intake and daily production of milk, fat, protein, lactose, nonfat solids, and total solids did not differ between cows fed the TC1507 diet and cows fed the control diet. Furthermore, milk from cows in different dietary treatment groups did not differ in milk urea nitrogen concentration or somatic cell count. For milk fat percentage, a significant dietary treatment by genetic group interaction was detected although overall yield of milk and solids-corrected milk did not differ with diet. Physical measures of cow health including body weight, body condition score, temperature, pulse, and respiration rate were collected weekly; dietary treatment group means for these measures were not different. Blood chemistry and hematological analyses were conducted using blood samples collected from cows before the start of the trial and at the end of each period. Overall, the TC1507 and control groups did not differ in any of these indices of health status. Further, hematological profiles for cows in the dietary treatment groups were not different. In summary, no differences were detected in milk production, milk composition, or cow health as indicated by physical measures, blood chemistry, and hematological analyses between dairy cows fed diets containing maize grain plus whole-plant maize silage from TC1507 and dairy cows fed grain plus silage from its near-isoline counterpart.     

Contrasted effects of dietary extruded linseed supplementation on carotenoid and liposoluble vitamin status in lactating Holstein or Montbéliarde cows fed hay or corn silage

Cow milk and dairy products have a good nutritional value that could be improved by increasing the concentrations of several compounds such as carotenoids and liposoluble vitamins A and E. Their concentrations in milk are dependent on their respective dietary intakes, but the transfer from feeds to milk seems to be limited by dietary, digestive, or metabolic factors linked to lipids that could differ between dairy breeds. The effect of dietary fat supplement (provided as extruded linseed) on carotenoid, vitamin E, and vitamin A status as well as their transfer from diet to milk were explored in mid-lactating dairy cows (Holstein or Montbéliarde breed) receiving either corn silage or hay as the main forage. Carotenoid and tocopherol status were higher in cows fed hay than in those fed corn silage, both at the plasma and milk level. The transfer rate for carotenoids was the same regardless of forage, whereas the transfer rate for tocopherols was greater (1.71 vs. 1.20%, respectively) for cows fed hay compared with corn silage. Cows fed extruded linseed had greater plasma concentrations of tocopherols (+25%) compared with those that did not, regardless of forage, but linseed treatment only changed xanthophyll (+35%) concentrations. This would suggest that the lipid supplement increased the availability of xanthophylls and tocopherols for the cows. However, carotenoid transfer into milk remained low and unaffected by the lipid supplement, whatever the forage nature, suggesting a limiting unknown process. Carotenoid status was marginally different between breeds because plasma concentrations were higher in Montbéliarde cows besides lower intakes. In milk, 13-E-β-carotene concentration was also higher for Montbéliarde cows because of a 2-fold higher transfer rate than for Holstein cows. In contrast, Holstein cows had higher transfer rates of α-tocopherol and vitamin A activity, linked to higher milk fat yield. For the first time, this study proposed an evaluation of the transfer rate of lipid micronutrients from diet to milk in cows. The study highlighted that these compounds follow distinct patterns of regulation during their transfer. However, in these experimental conditions, it was not possible to show that a dietary fat supplement could increase the concentration of these compounds in milk fat.     

Nutritional requirements and economics of lowering feed costs

Feed costs are, and will continue to be, the largest single expense for milk production. Gross efficiency of milk production is greater for high-producing cows because a lower proportion of total feed intake is used for maintenance of the cow. High milk production and high feed intake are positively correlated. The challenge for the future is to continue the remarkable progress in milk yield potential and increased feed efficiency realized in the recent past. Some areas of research that show promise for improving our knowledge and ability to feed cows for even greater efficiency include studies of energy metabolism, protein metabolism, voluntary feed intake, ruminal fermentation and fiber requirements, effects of growth hormone on milk production and animal metabolism, mineral nutrition, buffers, and vitamins. Practical studies on treatment and utilization of by-product feeds, manipulation of milk composition through nutrition, and continued development of better computer models for feeding and management decisions will have a significant effect on the efficiency and profitability of the dairy enterprise.     

Rapid detection of cows' milk in sheeps' and goats' milk by a species-specific polymerase chain reaction technique

A polymerase chain reaction (PCR) assay was developed for the specific identification of cows' milk in sheep's and goats' milk by using primers targeting the mitochondrial 12S rRNA gene. The use of a forward primer complementary to a conserved DNA sequence, along with a reverse primer specific for cow, yielded a 223-bp fragment from cows' milk DNA, whereas no amplification signal was obtained in sheep's and goats' milk DNA. The technique was applied to raw, pasteurized, and sterilized milk binary mixtures of cow-sheep and cow-goat, enabling the specific detection of cows' milk with a good sensitivity threshold (0.1%). The proposed PCR assay represents a rapid and straightforward method applicable to the authentication of milk and other dairy products in routine analysis.     

Italian ryegrass silage in winter feeding of organic dairy cows: forage intake, milk yield and composition

BACKGROUND: Organic milk production aims at efficient use of home‐grown feeds, especially forages, to minimise the quantity of purchased feeds. In conventional agriculture, Italian ryegrass (Lolium multiflorum Lam.) is known for its high energy content and palatability, and the aim of the present study was to examine its suitability as feed for organic dairy cows. Therefore a feeding trial was conducted comparing a diet including 50% (of silage dry matter (DM)) of Italian ryegrass silage with a control diet based on grass/clover silage (a mixture of the second cut from permanent grassland and the second cut from a perennial clovergrass ley) alone. RESULTS: Inclusion of Italian ryegrass silage in the diet increased forage intake significantly (14.5 vs 13.4 kg DM in the control group) and concentrate intake did not differ, but milk yield was slightly lower (20.3 vs 21.0 kg) owing to the low energy and protein concentration of Italian ryegrass silage. CONCLUSION: Italian ryegrass was indeed found to be highly palatable, confirming in principle its suitability as feed for organic dairy cows. However, higher energy and protein concentrations in this forage would be necessary to translate the high intakes of Italian ryegrass silage into improved milk production as well. Copyright © 2010 Society of Chemical Industry     

Effects of partial substitution of concentrates with maize silage in organic dairy cow rations on performance and feed efficiency

BACKGROUND: The general goal of organic dairy farming is to minimize purchased concentrate use and focus on milk production from forages. The aim of the present paper is to examine the influence of a partial substitution of purchased concentrates with home‐grown maize silage on feed intake, milk production and feed efficiency in rations for organic dairy cows. In the experimental treatment group (E), two‐thirds of average herd concentrate intake was replaced with 2.7 kg maize silage on a dry matter (DM) basis. RESULTS: In treatment E, total DM, energy and protein intake were significantly reduced compared to the control treatment group (C). Daily milk yield decreased in E by 11% and milk urea content was significantly lower. Calculated milk production from forage was significantly higher (91 versus 71%) in treatment E. Efficiency of dietary nitrogen (N) utilization (calculated as milk N as a percentage of N intake) was slightly improved in E and protein and energy balance (calculated as intake as a percentage of requirements) were closer to zero than in C. CONCLUSION: The present study indicates a potential to reduce levels of concentrates and substitute them with maize silage in organic dairy cow rations at least in the second half of lactation. Copyright © 2007 Society of Chemical Industry     

Modification of the sterol profile in milk through feeding

The fortification of milk with phytosterols is an increasingly common practice to enhance the sterol profile and offer consumers potential health benefits. This study investigated whether cattle feed can influence the profile of phytosterols and cholesterol in the milk produced as an alternative to direct fortification of milk. Five experiments were performed using feeds commonly used by Australian dairy farmers and selected formulated rumen-protected feeds. Statistical significances were observed for some individual plant sterols and cholesterol in milk under these differing feeding regimens compared with the respective controls. In the case of the phytosterols, where the daily recommended consumption is typically 2 g per day, the total phytosterols were <0.12 mg/100 mL of milk. An experiment using a rumen-protected feed with high phytosterol levels suggested a decreased transfer of cholesterol to the milk by as much as 20%, although further work is required to confirm these preliminary results. Overall, the study suggests that different feeding practices have minimal effect on the resulting sterol profile of the milk.     

Relationship between content of crude protein in rations for dairy cows and milk yield,concentration of urea in milk and ammonia emissions

During recent decades, efforts have been made in several countries to diminish the negative environmental influence of dairy production. The main focus has been on nitrogen and phosphorus. Modern dairy production in Western Europe is often based on imported feed-stuffs, mostly protein-rich feeds. In Sweden at least, it is wished that the use of imported feedstuffs in animal production will decrease due to the risk of contamination with Salmonella and the ban of using GMO crops in Swedish dairy production. An experiment was carried out to investigate whether a lower content of crude protein in the diet would decrease the ammonia release from cow manure and whether a well-balanced diet using only feedstuffs of Swedish origin would maintain milk production. Five treatments were arranged in a Latin square design. Two different protein supplements made of ingredients of Swedish origin were each fed at two protein levels, and a fifth imported commercial protein mix was fed at the higher level. The treatments with low protein levels (13.1 to 13.5%) had a significantly lower milk yield, kilograms of ECM, but, on the other hand the net profit, milk income minus feed cost was nearly the same in all treatments except diet C, which had lower feed cost but also lower net profit due to lower milk yield. The content of urea in milk was higher with diets high in crude protein (17%) content. A decreased protein level in the diets did not influence the content of casein or whey protein, but the commercial concentrate showed a tendency to give lower values than the Swedish mixtures. The low protein diets gave significantly lower ammonia release from manure compared with the high protein diets. There were no production differences between the diets of Swedish feeds compared with the imported control. The readily fermentable beet pulp should have helped cows use the higher N diet more efficiently and increased the response. This gives the rumen microbes a possibility to match the inflow of protein with carbohydrates. Income over feed costs shows that it is possible to compile diets using products of Swedish origin and still be competitive. On the other hand, this structure may change quickly due to altered world market prices.