Danish Jersey Cows Research Articles

Feeding up to 91% concentrate to Holstein and Jersey dairy cows: Effects on enteric methane emission, rumen fermentation and bacterial community, digestibility, production, and feeding behavior.

Due to climate change, periods of drought might be longer and occur more frequently, which challenges roughage production and requires changed feeding of dairy cattle by increasing the grain content of the diet. This study investigated the effect of diets with concentrate proportions up to 91% of dry matter on dry matter intake (DMI), milk production, enteric methane emission, rumen fermentation, rumen bacterial community structure, nutrient digestibility, and feeding behavior of Holstein and Jersey dairy cows. Twelve Danish Holstein and 12 Danish Jersey cows were fed ad libitum with one of 3 total mixed rations differing in concentrate proportion in a continuous design with staggered approach over 19 to 29 d. Dietary concentrate proportions were 49% (C49), 70% (C70), and 91% (C91) on dry matter basis, and were based on increasing proportions of chopped barley straw, dried beet pulp, barley, NaOH-treated wheat, dried distillers grain, and rapeseed cake at the expense of grass/clover silage, corn silage and soybean meal. Cows were adapted to the diets over a 12- to 19-d period, before rumination activity was measured over 3 d. Subsequently, spot samples of feces were collected for digestibility determination over 2 d, and gas exchange was measured on the last 3 d of the experimental period. Shortly after chamber stay, rumen liquid was collected using an oro-ruminal device. Dry matter intake was higher for Holstein than Jersey. Methane emissions (all expressions) were affected by the interaction between breed and diet. Methane per kilogram of DMI was lowered by 18 and 48% for Holstein fed C70 and C91, respectively, compared with C49, whereas this was 17 and 22% respectively for Jersey. Rumen propionate molar proportion increased more, rumen bacterial community was less diverse, and rumination time and rumination chews relative to DMI reduced less for Holstein than for Jersey cows with increasing concentrate level. In conclusion, Holstein dairy cows responded stronger to increased dietary concentrate level regarding methane mitigation, changes in rumen VFA profile, and effect on the rumen bacterial community structure than Jersey cows, whereas Jersey cows responded stronger with regard to rumination time and rumination chews (per kilogram of DMI and per kilogram of neutral detergent fiber intake) than Holstein cows. Thus, diets high in concentrates are a less effective methane mitigation strategy for Jersey than for Holstein.

Effect of lameness on feeding behavior of zero grazed Jersey dairy cows.

The dairy industry faces major challenges with high levels of lameness, in parallel to an increased consumer focus on animal welfare. This encourages farmers to consider more robust breeds, such as Jersey cows. As little is known about the behavior of this breed under loose housing conditions, the present study sought to describe the feeding behavior of lame and non-lame Jersey cows in different parities. Such breed-specific information of behavioral changes is needed for breed-specific herd management decisions and may contribute to identifying animals that are susceptible to developing lameness in the future, thus reducing impacts on the welfare and production of cows. Feeding data from 116 Danish Jersey cows were collected using automatic feeders, and lameness status was assessed by technicians every second week. The cows were kept in a loose housing system, with cubicles, a slatted concrete floor, and automatic milking robots. Eating time per visit and per day, the number of visits per day, and intervals between meals were analyzed using generalized linear mixed effects models. The effect of lameness was not significant for any variable. Primiparous Jersey cows had significantly longer eating times per day, shorter meal intervals, and a lower number of visits per day than older Jersey cows. Week in lactation affected the eating time per visit and per day, the number of visits, and between-meal intervals. In conclusion, we found no differences between lame and non-lame Jersey cows but between parities, which disagree with previous research on other breeds, suggesting that Jersey cows not just differ in size and looks but also in their behavioral reaction when lame. Although data from only one herd of a research center were used, this study has demonstrated the need for further research about breed-specific differences and their implications for the health and welfare of the animals.

Genetic analysis on infrared-predicted milk minerals for Danish dairy cattle

A group of milk components that has shown potential to be predicted with milk spectra is milk minerals. Milk minerals are important for human health and cow health. Having an inexpensive and fast way to measure milk mineral concentrations would open doors for research, herd management, and selective breeding. The first aim of this study was to predict milk minerals with infrared milk spectra. Additionally, milk minerals were predicted with infrared-predicted fat, protein, and lactose content. The second aim was to perform a genetic analysis on infrared-predicted milk minerals, to identify QTL, and estimate variance components. For training and validating a multibreed prediction model for individual milk minerals, 264 Danish Jersey cows and 254 Danish Holstein cows were used. Partial least square regression prediction models were built for Ca, Cu, Fe, K, Mg, Mn, Na, P, Se, and Zn based on 80% of the cows, selected randomly. Prediction models were externally validated with 8 herds based on the remaining 20% of the cows. The prediction models were applied on a population of approximately 1,400 Danish Holstein cows with 5,600 infrared spectral records and 1,700 Danish Jersey cows with 7,200 infrared spectral records. Cows from this population had 50k imputed genotypes. Prediction accuracy was good for P and Ca, with external R2 ≥ 0.80 and a relative prediction error of 5.4% for P and 6.3% for Ca. Prediction was moderately good for Na with an external R2 of 0.63, and a relative error of 18.8%. Prediction accuracies of milk minerals based on infrared-predicted fat, protein, and lactose content were considerably lower than those based on the infrared milk spectra. This shows that the milk infrared spectrum contains valuable information on milk minerals, which is currently not used. Heritability for infrared-predicted Ca, Na, and P varied from low (0.13) to moderate (0.36). Several QTL for infrared-predicted milk minerals were observed that have been associated with gold standard milk minerals previously. In conclusion, this study has shown infrared milk spectra were good at predicting Ca, Na, and P in milk. Infrared-predicted Ca, Na, and P had low to moderate heritability estimates.

Genetic analysis of orotic acid predicted with Fourier transform infrared milk spectra

Fourier transform infrared spectral analysis is a cheap and fast method to predict milk composition. A not very well studied milk component is orotic acid. Orotic acid is an intermediate in the biosynthesis pathway of pyrimidine nucleotides and is an indicator for the metabolic cattle disorder deficiency of uridine monophosphate synthase. The function of orotic acid in milk and its effect on calf health, health of humans consuming milk or milk products, manufacturing properties of milk, and its potential as an indicator trait are largely unknown. The aims of this study were to determine if milk orotic acid can be predicted from infrared milk spectra and to perform a large-scale phenotypic and genetic analysis of infrared-predicted milk orotic acid. An infrared prediction model for orotic acid was built using a training population of 292 Danish Holstein and 299 Danish Jersey cows, and a validation population of 381 Danish Holstein cows. Milk orotic acid concentration was determined with nuclear magnetic resonance spectroscopy. For genetic analysis of infrared orotic acid, 3 study populations were used: 3,210 Danish Holstein cows, 3,360 Danish Jersey cows, and 1,349 Dutch Holstein Friesian cows. Using partial least square regression, a prediction model for orotic acid was built with 18 latent variables. The error of the prediction for the infrared model varied from 1.0 to 3.2 mg/L, and the accuracy varied from 0.68 to 0.86. Heritability of infrared orotic acid predicted with the standardized prediction model was 0.18 for Danish Holstein, 0.09 for Danish Jersey, and 0.37 for Dutch Holstein Friesian. We conclude that milk orotic acid can be predicted with moderate to good accuracy based on infrared milk spectra and that infrared-predicted orotic acid is heritable. The availability of a cheap and fast method to predict milk orotic acid opens up possibilities to study the largely unknown functions of milk orotic acid.

Validation of AfiTagII, a device for automatic measuring of lying behaviour in Holstein and Jersey cows on two different bedding materials

Lying behaviour is important for the welfare of the cow. Therefore, reliable electronic devices may improve the management of the cows, and the devices can be used as a tool in research. However, accelerometer-based devices measure acceleration, and an algorithm is therefore necessary for the calculation of lying behaviour. Thus, validation of such devices is imperative prior to use. The objective of this study was to validate the use of the AfiTagII device for measurements of the lying time and frequency of lying bouts of Danish Holstein (DH) and Danish Jersey (DJ) cows in a loose-house system on two different bedding materials. The validation included correlations and linear regression analyses of data collected by the AfiTagII compared with data collected both by direct observations and recordings from a previously validated device (IceQube). In total, 40 cows were observed directly with primiparous and multiparous DJ and DH cows, equally represented. Furthermore, 21 cows were monitored with both AfiTagII and IceQube devices, and data from both devices were collected simultaneously. The devices were attached to the hind leg of the cow. The estimates of the lying time from the AfiTagII device was highly correlated with the recordings from direct observations (r=0.98), and there was a linear relation between these with an intercept equal to 0 and a slope close to 1. The estimates of the lying time from the AfiTagII device was also highly correlated with the IceQube recordings (r=0.94). However, the intercept deviated from 0. The frequency of lying bouts recorded by the AfiTAgII compared to direct observations showed a positive predictive value of 0.96 for lactating cows on the slatted floor and of 0.85 for the dry cows on the deep bedding. The correlations between frequency of lying bouts recorded with the two devices were high (r=0.94), but the intercept deviated from 0. In conclusion, the AfiTagII has a high accuracy for the measurements of lying behaviour in both DH and DJ cows kept on different bedding materials.

Genetic analysis of Fourier transform infrared milk spectra in Danish Holstein and Danish Jersey

Fourier transform infrared milk spectral data are routinely used for milk quality control and have been revealed to be driven by genetics. This study aimed to (1) estimate heritability for 1,060 wavenumbers in the infrared region from 5,008 to 925 cm-1, (2) estimate genomic correlations between wavenumbers with increased heritability, and (3) compare results between Danish Holstein and Danish Jersey cows. For Danish Holstein, 3,275 cows and 19,656 milk records were available. For Danish Jersey, 3,408 cows and 20,228 milk records were available. We used a hierarchical mixed model, with a Bayesian approach. Heritability of individual wavenumbers ranged from 0.00 to 0.31 in Danish Holstein, and from 0.00 to 0.30 in Danish Jersey. Genomic correlation was calculated between 15 selected wavenumbers, and varied from weak to very strong, in both Danish Holstein and Danish Jersey (0.03 to 0.97, and -0.11 to -0.97). Within the 15 selected wavenumbers, a subdivision into 2 groups of wavenumbers was observed, where genomic correlations were negative between groups, and positive within groups. Heritability and genomic correlations were higher in Danish Holstein compared with Danish Jersey, but followed a similar pattern in both breeds. Breed differences were most pronounced in the mid-infrared region that interacts with lactose and the spectral region that interacts with protein. In conclusion, heritability for individual wavenumbers of Fourier transform milk spectra was moderate, and strong genomic correlations were observed between wavenumbers across the spectrum. Heritability and genomic correlations were higher in Danish Holstein, with the strongest breed differences showing in spectral regions interacting with protein or lactose.

Genetic analysis of predicted fatty acid profiles of milk from Danish Holstein and Danish Jersey cattle populations

The objective of this study was to assess the genetic variability of the detailed fatty acid (FA) profiles of Danish Holstein (DH) and Danish Jersey (DJ) cattle populations. We estimated genetic parameters for 11 FA or groups of FA in milk samples from the Danish milk control system between May 2015 and October 2016. Concentrations of different FA and FA groups in milk samples were measured by mid-infrared spectroscopy. Data used for parameter estimation were from 132,732 first-parity DH cows and 21,966 first-parity DJ cows. We found the highest heritabilities for test day measurements in both populations for short-chain FA (DH = 0.16; DJ = 0.16) and C16:0 (DH = 0.14; DJ = 0.16). In DH, the highest heritabilities were also found for saturated FA and monounsaturated FA (both populations: 0.15). Genetic correlations between the fatty acid traits showed large differences between DH and DJ for especially short-chain FA with the other FA traits measured. Furthermore, genetic correlations of total fat with monounsaturated FA, polyunsaturated FA, short-chain FA, and C16:0 differed markedly between DH and DJ populations. In conclusion, we found genetic variation in the mid-infrared spectroscopy-predicted FA and FA groups of the DH and DJ cattle populations. This finding opens the possibility of using genetic selection to change the FA profiles of dairy cattle.

Herd characteristics influence farmers’ preferences for trait improvements in Danish Red and Danish Jersey cows

ABSTRACTThe aim of this study was to characterize preferences of farmers for breeding goal traits with Danish Red (DR) or Danish Jersey (DJ) cows. A breed-specific survey was established to characterize farmers’ preferences for improvements in 10 traits, by means of pairwise rankings using the online software 1000Minds. These pairwise rankings were based on equal economic worth of trait improvements. The DR survey was filled in by 87 farmers and the DJ survey by 76 farmers. Both DR and DJ farmers gave the highest preference to improvements in mastitis, and the lowest to calving difficulty. By means of a cluster analysis, three distinct clusters of farmers were identified per breed. Comparisons of herd characteristics between clusters suggest that farmers choose to improve traits that are problematic in their herds. This study shows that heterogeneity exists in farmers’ preferences for trait improvements and that herd characteristics influence these preferences in DR and DJ.

Factors influencing degree of glycosylation and phosphorylation of caseins in individual cow milk samples

The aim of this study was to examine variations in posttranslational modifications (PTM) of caseins (CN) in milk from individual cows and determine how these differ between breeds, across lactation, and between variants. Furthermore, we examined the variation of casein PTM in relation to rennet coagulation properties of milk. In total, detailed protein composition of milk from 892 Danish Holstein and Jersey cows was determined by liquid chromatography/electrospray ionization-mass spectrometry. The method measured relative contents of the main milk proteins as well as several variants and PTM. The results showed that the 2 breeds had distinct milk protein composition. Milk from Danish Holstein cows was mainly characterized by higher relative contents of β-CN, α-lactalbumin (α-LA), and β-lactoglobulin, and a higher fraction of glycosylated κ-CN (G κ-CN), whereas milk from Danish Jersey cows was characterized by higher relative contents of κ-CN, αS2-CN, and the less phosphorylated forms of αS1-CN and αS2-CN. Univariate linear models including days in milk and parity as class effects showed variation in the detailed protein profile across and between lactations; in particular, changes in the degree of glycosylation of κ-CN were pronounced, but changes in αS1-CN 8P to total αS1-CN and αS2-CN 11P to αS2-CN were also observed over lactation for both breeds. The phosphorylated forms of αS1-CN and αS2-CN were, to some extent, correlated. Further, the κ-CN BB genotype was associated with higher relative contents of both unglycosylated κ-CN (UG κ-CN) and G κ-CN compared with κ-CN AA; κ-CN AB showed intermediate results in both breeds. The influence of protein composition on rennet coagulation properties was explored based on 4 classes for curd firming rate: noncoagulation, and poor, average, and good coagulation. The results revealed breed differences: Holstein milk, higher relative content of κ-CN to total protein, and higher content of G κ-CN were associated with improved milk coagulation. In contrast, relative content of α-LA was the main component associated with milk coagulation properties in Danish Jerseys and it was shown to affect milk coagulation properties negatively. In addition, variation in phosphorylation degrees of αS1-CN also played a role. This study demonstrates that although the genetic influence of glycosylation seems to be the same in both breeds, nongenetic variation differs, which is further reflected in different associations with milk coagulation properties.

Short communication: Genetic variation of riboflavin content in bovine milk

Riboflavin (vitamin B2) is an essential water-soluble vitamin; elderly people and adolescents in particular can have poor riboflavin status. In Western diets, milk and dairy products are primary sources of riboflavin, but little is known about the natural variation within and among bovine breeds, and how genetic and environmental factors can affect the riboflavin content in milk. As a part of the Danish-Swedish Milk Genomics Initiative, the aim of the study was to quantify milk riboflavin content using reverse-phase HPLC in 2 major Danish dairy breeds. The results showed substantial interbreed differences in milk riboflavin content. Milk from Danish Jersey cows contained significantly higher levels of riboflavin (1.93mg/L of milk) than milk from Danish Holstein cows (1.40mg/L of milk). Furthermore, genetic analyses revealed high heritabilities in both breeds (0.52 for Danish Holstein and 0.31 for Danish Jersey). A genomic association study found 35 significant single nucleotide polymorphisms (false discovery rate<0.10) to be associated with riboflavin content in milk in Jersey cows (all on BTA14 and BTA17), and 511 significant single nucleotide polymorphisms in Holstein cows spread over 25 different autosomes with BTA13 and BTA14 having the most promising quantitative trait loci. The best candidate gene found within the identified quantitative trait loci was SLC52A3, a riboflavin transporter gene, which was among the significant markers on BTA13 in Holstein cows.

Phenotypic and genetic associations of milk traits with milk coagulation properties

The aim of this study was to examine milk composition and rennet-induced coagulation properties of milk from 892 individual Danish Holstein and Danish Jersey cows and determine the genetic influences on these properties by determining heritability and genomic correlations with single nucleotide polymorphisms identified by the bovine HD Beadchip (Illumina Inc., San Diego, CA). Despite no signs of clinical mastitis, milk from cows with somatic cell counts >500,000 cells/mL showed altered milk composition, indicating impaired barrier between the milk and the blood. Curd-firming rate (CFR) and rennet coagulation time (RCT) were used to describe milk coagulation properties (MCP). These traits describe the second phase of milk coagulation and were mutually negatively correlated, but only to some extent associated with the same compositional traits. In both breeds, CFR were highly correlated with protein content, whereas longer RCT were primarily associated with lower milk pH. Estimated heritabilities for milk production and compositional traits ranged from 0.09 for yield to 0.82 for citric acid in Danish Jersey cows, and from 0.21 for yield to 0.59 for citric acid in Danish Holstein cows. Heritabilities for MCP traits varied considerably between breeds, and were estimated to be 0.28 for RCT and 0.75 for CFR in Danish Holstein cows and 0.45 for RCT and 0.15 for CFR in Danish Jersey cows. This difference was further reflected in the genomic correlations between RCT and CFR which was −0.90 in Danish Holstein and 0.06 in Danish Jersey. These data suggest that potential for changing MCP through breeding exists, but the genetic background of the MCP traits might be different in different breeds; therefore, using Danish Holstein as background for Danish Jersey is not trivial. Thereby, the study underlines the need for breed-specific models.

Fluorometric determination of free and total isocitrate in bovine milk

Isocitrate is an intermediate metabolite in the citric acid cycle found both inside the mitochondria as well as outside in the cytosolic shunt. Oxidation of isocitrate is believed to deliver large fractions of energy [i.e., reducing equivalents (NADPH) in the bovine udder] used for fatty acid and cholesterol synthesis. This study describes a new analytical method for determination of free and total isocitrate in bovine milk where time-consuming pretreatment of the sample is not necessary. Methods for estimation of both total isocitrate and free isocitrate are described, the difference being the esterified or even lactonized isocitrate. On average, 20% (6–27%) of cow milk isocitrate was esterified and free isocitrate correlated significantly with total isocitrate (r=0.98). The present fluorometric determination correlated well with the traditional spectrophotometric determination of isocitrate. Milk samples from Danish Holstein cows (984) contained significantly less isocitrate than milk from Danish Jersey cows (760; i.e., 0.134 vs. 0.211mmol/L). Isocitrate in milk is correlated to milk protein, fat, and citrate, and it is speculated, based on biochemistry, former studies, and the present, that isocitrate may reflect the energy situation in the mammary gland. The use of isocitrate as a biomarker of the energy status in the dairy cow is warranted.

Short communication: Heterosis by environment and genotype by environment interactions for protein yield in Danish Jerseys

Crossing of lines or strains within and between breeds has been demonstrated to be beneficial for dairy cattle performance. However, even within breed, differences between strains may also give rise to heterosis. A key question is whether an interaction exists between heterosis and environment (H × E) that is independent of genotype by environment (G × E) interactions. In this study, H × E and G × E interactions were estimated in a population of approximately 300,000 Danish Jersey cows. The cows were a mixture of pure Danish Jerseys and crosses of US and Danish Jerseys. The phenotype studied was protein yield. A reaction norm model where the unknown environmental covariates are inferred simultaneously with the other parameters in the model was used to analyze the data. When H × E, but not G × E, was included in the model, heterosis was estimated to be 3.8% for the intermediate environmental level. However, when both H × E and G × E were included in the model, heterosis was estimated to be 4.1% for the intermediate environmental level. Furthermore, when only H × E was included in the model, the regression on the unknown environmental covariate was estimated to be 0.15, interpreted as meaning that an increase of average herd-year protein yield by 1kg of protein led to an increase in heterosis of 0.15kg above the average heterosis for a first-cross cow. When both H × E and G × E were included in the model, the regression on the unknown environmental covariate was not significantly different from zero, meaning that heterosis was similar in all environments investigated. The genetic correlation of protein yields for different environmental levels ranged from 0.72 to 0.93, which was significantly different from unity, indicating that G × E exist for protein yield.

Effects of breed and casein genetic variants on protein profile in milk from Swedish Red, Danish Holstein, and Danish Jersey cows

In selecting cows for higher milk yields and milk quality, it is important to understand how these traits are affected by the bovine genome. The major milk proteins exhibit genetic polymorphism and these genetic variants can serve as markers for milk composition, milk production traits, and technological properties of milk. The aim of this study was to investigate the relationships between casein (CN) genetic variants and detailed protein composition in Swedish and Danish dairy milk. Milk and DNA samples were collected from approximately 400 individual cows each of 3 Scandinavian dairy breeds: Swedish Red (SR), Danish Holstein (DH), and Danish Jersey (DJ). The protein profile with relative concentrations of α-lactalbumin, β-lactoglobulin, and αS1-, αS2-, κ-, and β-CN was determined for each milk sample using capillary zone electrophoresis. The genetic variants of the αS1- (CSN1S1), β- (CSN2), and κ-CN (CSN3) genes for each cow were determined using TaqMan SNP genotyping assays (Applied Biosystems, Foster City, CA). Univariate statistical models were used to evaluate the effects of composite genetic variants, αS1-β-κ-CN, on the protein profile. The 3 studied Scandinavian breeds differed from each other regarding CN genotypes, with DH and SR having similar genotype frequencies, whereas the genotype frequencies in DJ differed from the other 2 breeds. The similarities in genotype frequencies of SR and DH and differences compared with DJ were also seen in milk production traits, gross milk composition, and protein profile. Frequencies of the most common composite αS1-β-κ-CN genotype BB/A2A2/AA were 30% in DH and 15% in SR, and cows that had this genotype gave milk with lower relative concentrations of κ- and β-CN and higher relative concentrations of αS-CN, than the majority of the other composite genotypes in SR and DH. The effect of composite genotypes on relative concentrations of the milk proteins was not as pronounced in DJ. The present work suggests that a higher frequency of BB/A1A2/AB, together with a decrease in BB/A2A2/AA, could have positive effects on DH and SR milk regarding, for example, the processing of cheese.

The occurrence of noncoagulating milk and the association of bovine milk coagulation properties with genetic variants of the caseins in 3 Scandinavian dairy breeds

Substantial variation in milk coagulation properties has been observed among dairy cows. Consequently, raw milk from individual cows and breeds exhibits distinct coagulation capacities that potentially affect the technological properties and milk processing into cheese. This variation is largely influenced by protein composition, which is in turn affected by underlying genetic polymorphisms in the major milk proteins. In this study, we conducted a large screening on 3 major Scandinavian breeds to resolve the variation in milk coagulation traits and the frequency of milk with impaired coagulation properties (noncoagulation). In total, individual coagulation properties were measured on morning milk collected from 1,299 Danish Holstein (DH), Danish Jersey (DJ), and Swedish Red (SR) cows. The 3 breeds demonstrated notable interbreed differences in coagulation properties, with DJ cows exhibiting superior coagulation compared with the other 2 breeds. In addition, milk samples from 2% of DH and 16% of SR cows were classified as noncoagulating. Furthermore, the cows were genotyped for major genetic variants in the αS1- (CSN1S1), β- (CSN2), and κ-casein (CSN3) genes, revealing distinct differences in variant frequencies among breeds. Allele I of CSN2, which had not formerly been screened in such a high number of cows in these Scandinavian breeds, showed a frequency around 7% in DH and DJ, but was not detected in SR. Genetic polymorphisms were significantly associated with curd firming rate and rennet coagulation time. Thus, CSN1S1 C, CSN2 B, and CSN3 B positively affected milk coagulation, whereas CSN2 A2, in particular, had a negative effect. In addition to the influence of individual casein genes, the effects of CSN1S1-CSN2-CSN3 composite genotypes were also examined, and revealed strong associations in all breeds, which more or less reflected the single gene results. Overall, milk coagulation is under the influence of additive genetic variation. Optimal milk for future cheese production can be ensured by monitoring the frequency of unfavorable variants and thus preventing an increase in the number of cows producing milk with impaired coagulation. Selective breeding for variants associated with superior milk coagulation can potentially increase raw milk quality and cheese yield in all 3 Scandinavian breeds.

Milk production and composition in Danish Holstein, Danish Red, and Danish Jersey cows supplemented with saturated or unsaturated fat

The aim of the experiment was to study the response in milk production and composition of substituting barley with either saturated or unsaturated fat in mixed rations (MR) for dairy cows. The experiment included 35 Danish Holstein (DH), 39 Danish Red (DR), and 31 Danish Jersey (DJ) cows from parturition until week 30 of lactation. Cows were ad libitum fed one of the three MR based on maize and grass/clover silage, barley, soybean meal, and dried sugar beet pulp. In the saturated ration (SFA), C16 rich fat substituted barley on dry matter (DM) basis; in the unsaturated ration (UFA), ground rape and linseed (0.74:0.26 ratio) substituted barley on DM basis; and in the control ration (CO), no barley was substituted. Concentrations of crude fat (CF) of total ration DM was 3.03% in CO, and in diets supplemented to intended similar fat levels 5.65% (SFA) and 5.81% (UFA), respectively. Statistical analyses were performed within breed and random regression was used to test for differences between treatment responses throughout lactations.For all breeds, SFA increased milk fat concentration of C16 whereas UFA increased milk fat concentration of unsaturated as well as saturated C18 fatty acids (FA). For each of the three breeds the following responses were obtained compared to CO. DR: UFA increased the net energy intake (NEI) (P=0.04), but energy corrected milk (ECM) yield was reduced to 30.9kg/d compared to 31.7kg/d for CO (ns). SFA increased milk fat concentration to 4.42% compared to 3.87% for CO (P<0.0001). DH: SFA decreased DM intake (DMI) (P=0.05), but ECM was slightly increased to 34.5kg/d compared to 34.0kg/d for CO (ns). Both SFA and UFA decreased the milk protein concentration to 3.30% compared to 3.49% for CO (P<0.05). Sensory analysis of milk from DH showed only minor differences between treatments. DJ: SFA (P=0.2) and UFA (P=0.07) tended to decrease DMI, and decreased ECM to 28.6kg/d (SFA, P=0.02) and 28.0kg/d (UFA, P=0.01) compared to 31.6kg/d (CO). Furthermore, SFA and UFA tended to increase milk fat.In conclusion, SFA caused a lower protein:fat ratio in milk for all breeds, while UFA only reduced protein:fat ratio for DJ. The minor increased (DH), and the tendency to decreased (DR, DJ) milk yield response to feeding SFA was unexpected, and may be due to a general negative effect of feeding fat in early lactation.

Distinct composition of bovine milk from Jersey and Holstein-Friesian cows with good, poor, or noncoagulation properties as reflected in protein genetic variants and isoforms

The objective of this study was to examine variation in overall milk, protein, and mineral composition of bovine milk in relation to rennet-induced coagulation, with the aim of elucidating the underlying causes of milk with impaired coagulation abilities. On the basis of an initial screening of 892 milk samples from 42 herds with Danish Jersey and Holstein-Friesian cows, a subset of 102 samples was selected to represent milk with good, poor, or noncoagulating properties (i.e., samples that within each breed represented the most extremes in regard to coagulation properties). Milk with good coagulation characteristics was defined as milk forming a strong coagulum based on oscillatory rheology, as indicated by high values for maximum coagulum strength (G′max) and curd firming rate (CFR) and a short rennet coagulation time. Poorly coagulating milk formed a weak coagulum, with a low G′max and CFR and a long rennet coagulation time. Noncoagulating milk was defined as milk that failed to form a coagulum, having G′max and CFR values of zero at measurements taken within 1h after addition of rennet. For both breeds, a lower content of total protein, total casein (CN) and κ-CN, and lower levels of minerals (Ca, P, Mg) were identified in poorly coagulating and noncoagulating milk in comparison with milk with good coagulation properties. Liquid chromatography/electrospray ionization-mass spectrometry revealed the presence of a great variety of genetic variants of the major milk proteins, namely, αS1-CN (variants B and C), αS2-CN (A), β-CN (A1, A2, B, I, and F), κ-CN (A, B, and E), α-lactalbumin (B), and β-lactoglobulin (A, B, and C). In poorly coagulating and noncoagulating milk samples of both breeds, the predominant composite genotype of αS1-, β-, and κ-CN was BB-A2A2-AA, which confirmed a genetic contribution to impaired milk coagulation. Interestingly, subtle variations in posttranslational modification of CN were observed between the coagulation classes in both breeds. Poorly coagulating and noncoagulating milk contained a lower fraction of the least phosphorylated αS1-CN form, αS1-CN 8P, relative to total αS1-CN, along with a lower fraction of glycosylated κ-CN relative to total κ-CN. Thus, apparent variation was observed in the milk and protein composition, in the genetic makeup of the major milk proteins, and in the posttranslational modification level of CN between milk samples with either good or impaired coagulation ability, whereas the composition of poorly coagulating and noncoagulating milk was similar.

The influence of feed and herd on fatty acid composition in 3 dairy breeds (Danish Holstein, Danish Jersey, and Swedish Red)

The composition of milk fat from dairy cows is related to both genetic and environmental factors. Here, the effect of feed and herd was examined in 3 Scandinavian breeds, namely Danish Holstein-Friesian (DH), Danish Jersey (DJ), and Swedish Red (SR). In total, milk samples from 1,298 cows kept in indoor housing systems were collected from 61 conventional dairy herds in Denmark and Sweden. The fatty acid (FA) composition of milk was determined by gas chromatography and the content of α-tocopherol by HPLC. Based on the 17 individual FA determined, distinct FA profiles were observed for all breeds using univariate and multivariate statistics. The DJ cows were characterized by higher levels of saturated short-chain FA; in contrast, DH cows had higher content of unsaturated C18 FA, whereas higher levels of primarily C14:0, C14:1, C18:1 cis-9, and C18:3n-3 were evident in SR cows. This variation in milk fat composition across breeds was further reflected in different desaturase indices, which were generally higher in SR cows. In addition, α-tocopherol differed significantly among breeds, with DJ cows having the highest content. Herd-specific feeding plans were collected, and different feed items were separated into 4 broad feed categories, including grass products, maize silage, grain, and concentrate. The pronounced differences in overall feed composition among breeds were, to a large extent, due to regional differences between countries, with SR receiving higher levels of grain and grass silage compared with the Danish breeds. Within breeds, differences in feeding regimens among herds were furthermore higher in SR. Significant correlations between feed category and individual FA were observed in all breeds. Furthermore, variance components were estimated and used to determine the proportion of phenotypic variation that could be explained by herd. The herd effect for individual FA was generally lower for DH compared with the 2 other breeds. In addition, very low herd effects were shown for C14:1 and C16:1 in all breeds, suggesting that the content of these FA is mainly genetically regulated.

Milk fatty acid composition and production performance of Danish Holstein and Danish Jersey cows fed different amounts of linseed and rapeseed

Fat supplements are used in diets for dairy cows to increase energy intake and milk production and the fatty acid composition of the feed affects milk fatty acid composition. A total of 74 Danish Holstein and 41 Danish Jersey cows were divided into 4 groups and the cows within each group were fed a mixed ration supplemented with 0, 3.5, 6.8, or 10.2% of dry matter of a linseed:rapeseed (1:3) mixture during lactation wk 6 to 30. Milk yield, fat, and lactose contents were not affected by treatments for Danish Holsteins, whereas these parameters increased when increased amounts of oilseeds were fed to Danish Jerseys. For both breeds, milk protein content decreased when increased amounts of oilseeds were fed. The milk fatty acid composition showed higher concentrations of saturated fatty acids and lower concentrations of unsaturated fatty acids in milk fat from Danish Jerseys compared with Danish Holsteins. Increased amounts of oilseeds in feed increased milk fat concentration of all C18 fatty acids except C18:2 n-6, whereas the content of C6 to C14, C11 to C17, and in particular, C16, decreased. This effect was more pronounced for Danish Holsteins than for Danish Jerseys. The apparent recovery of C18:2 n-6 and C18:3 n-3 decreased when increased amounts of oilseeds were fed; however, this was most likely due to increased amounts of fatty acid from feed used for other energy demands than milk production. It was concluded that up to 6.8% of oilseed supplementation can be fed without production problems and, in many cases, with positive production responses, including an improved milk fatty acid profile.

Short communication: Is crossbreeding only beneficial in herds with low management level?

The economic benefit of crossbreeding has been well known for many years within dairy production. However, in most countries with an intensive dairy production, an extended use of systematic crossbreeding has not occurred. This may be due to the myth that heterosis is expressed mainly in low-producing herds. The aim of the study was to investigate the effect of heterosis with different management levels in Danish Jersey herds. More than 300,000 records of 305-d milk, fat, and protein yield from first-lactation Danish Jersey cows with different contributions from original Danish and US Jersey were analyzed using an animal model. The herds were distributed in 5 management groups based on production level. First, the results showed a large increase in additive genetic variance from the herds with lowest production level to the high-producing ones, and second, heterosis for all 3 production traits were lowest within the low-intensity management group and tended to be highest in the intermediate management groups. The results, therefore, support that crossbreeding is a breeding system that should be considered valuable for all management levels.