Interest in changing the milk fatty acid profile is growing. However, little is known about the genetic variability of milk fatty acids in the US Holstein population. Therefore, genetic parameters for milk fatty acids were estimated using a single-trait, mixed, linear animal model on 592 individual milk samples from 233 daughters of 53 sires in a cow herd genetically representative of the US Holstein population. Heritability (h(2)) and repeatability (r) estimates +/- standard errors for yields of individual fatty acids ranged from 0.00 +/- 0.08 (C4:0) to 0.43 +/- 0.13 (C12:0) for heritabilities and from 0.21 +/- 0.05 (C18:1) to 0.43 +/- 0.05 (C12:0) for repeatabilities. Saturated (h(2) = 0.23 +/- 0.12; r = 0.36 +/- 0.05) and de novo synthesized fatty acids (C6:0 to C14:0; h(2) = 0.30 +/- 0.13; r = 0.40 +/- 0.05) had numerically higher estimates than did monounsaturated (h(2) = 0.09 +/- 0.09; r = 0.22 +/- 0.05) and polyunsaturated fatty acids (h(2) = 0.08 +/- 0.09; r = 0.27 +/- 0.05). For relative proportions of individual fatty acids, the greatest heritability and repeatability estimates were obtained for C8:0 (h(2) = 0.18 +/- 0.12; r = 0.36 +/- 0.05), C10:0 (h(2) = 0.22 +/- 0.13; r = 0.46 +/- 0.05), C12:0 (h(2) = 0.18 +/- 0.12; r = 0.46 +/- 0.05), C16:0 (h(2) = 0.09 +/- 0.12; r = 0.48 +/- 0.05), C16:1 (h(2) = 0.49 +/- 0.13; r = 0.49 +/- 0.05), and C18:0 (h(2) = 0.24 +/- 0.11; r = 0.39 +/- 0.05). Our results suggest the existence of genetic variability of milk fatty acids, in particular of medium-and long-chain fatty acids (C8:0 to C18:0), which could be used to improve the nutritional and textural properties of milk fat by selective breeding.

Changing the composition of milk protein and of milk fatty acids alters nutritional and physical properties of dairy products and their consumer appeal. Genetic selection for milk yield decreases concentrations of milk protein and of milk fat. Little is known, however, about how the decrease affects composition of milk protein and milk fatty acids. The objective of this study was to quantify changes in composition of milk protein and of milk fatty acids in cows differing in genetic merit for milk production. Three measures of genetic merit for milk production were used for each cow: genetic line, parent average predicted transmitting ability (PTA) for milk, and cow milk PTA. Composition of milk protein and milk fatty acids were compared in 448 milk samples from 178 cows representing 2 divergent lines of Holsteins that were bred for high or average PTA for milk and combined milk protein and fat yield. High-line cows (n = 97) produced more milk that contained less fat and had higher proportions of alphaS1-casein in milk protein than did average-line cows (n = 81). We additionally obtained from 233 cows (178 cows representing the 2 genetic lines and 55 cows with ancestors from both genetic lines) the parent average milk PTA and cow milk PTA and compared composition of milk protein and of milk fatty acids in 592 milk samples. Cows whose parent average milk PTA was above or equal to the median of the 233 cows produced more milk that contained less protein and less fat and that tended to have greater proportions of alphaS1-casein in milk protein than cows whose average milk PTA was below the median. Similarly, cows with above or equal median milk PTA of the 233 cows produced more milk that contained less protein and less fat and had greater proportions of alphaS1-casein in milk protein than did cows with below-median milk PTA. Milk fatty acid composition was not consistently different between groups. Therefore, selection for milk yield decreased concentrations of milk protein and milk fat but had little effect on composition of milk protein and milk fatty acids.

Health data collected from 1996 to 1999 from 177 herds in Minnesota and Wisconsin were analyzed to establish genetic basis for infectious and noninfectious diseases. Three types of health traits were targeted. First, available infectious conditions were used to identify animals that are superior in their general immunity (including innate immunity) for infectious diseases. Generalized immunity may be thought of as a combination of immune responses to a variety of immune system challenges. Second, single infectious and noninfectious diseases were analyzed separately. Third, infectious reproductive diseases as one category of related conditions, and cystic ovary disease as one category of 3 related noninfectious ovary disorders were studied. Data were analyzed using a threshold model that included herd, calving year, season of calving, and parity as cross-classified fixed factors; and sire and cow within sires as random effects. Days at risk and days in milk at the beginning of a record were included by fitting the days as continuous covariates in the model. A heritability value of 0.202 +/- 0.083 was estimated for generalized immunity. Heritability values of 0.141 and 0.161 were estimated for uterine infection and mastitis, respectively. Heritability of single noninfectious disorders ranged from 0.087 to 0.349. The amount of additive genetic variance recovered in the underlying scale of noninfectious disorders tended to zero when combining multiple conditions. The study supports combining infectious diseases into categories of interest but we do not recommend the same approach for noninfectious disorders.

To compare the milk fatty acid composition of cows with different milk protein phenotypes, 592 milk samples from 233 Holstein cows were analyzed for kappa-casein and beta-lactoglobulin phenotypes and for fatty acid composition. Milk fat from cows with kappa-casein BB had the highest concentrations of 12:0 and lowest concentrations of 18:0, and milk fat of cows with kappa-casein AB had the lowest concentrations of 16:0. The B variant of P-lactoglobulin was associated linearly with greater concentrations of 14:0, 16:0, and 16:1 and lower concentrations of 18:0 and 18:1 in milk fat in comparison to the A allele. The results suggest that the B variants of kappa-casein and beta-lactoglobulin are associated with higher concentrations of de novo synthesized fatty acids at the expense of 18:0 in milk fat, which has implications on texture and sensory properties of dairy products. Therefore, genetic selection for the B variants of kappa-casein and beta-lactoglobulin could be used as an aid to manufacture dairy products with more desirable characteristics.

The objective of this study was to determine whether bovine mononuclear leukocytes exhibit genetic variability prior to and after a glucocorticoid hormone challenge in vivo. Test animals included 60 pedigreed Holstein bulls treated on 3 consecutive days with dexamethasone and 5 untreated control bulls. Eight indicator traits of leukocyte responsiveness to dexamethasone included the percentages of circulating B cells, T cells (CD4, CD8, and workshop cluster 1 molecule expressed by bovine gammadelta T cell), major histocompatibility complex (MHC) I and II expressing cells, and mean expressions of surface MHC I and MHC II on circulating cells. Blood for this work was collected from each test bull 10 times before, during, and after dexamethasone administration, with corresponding samples taken for control bulls. Random regression models with treatment-specific serial correlation were applied to the leukocyte data sets to estimate genetic and nongenetic sources of variation in baseline and recovery aspects of the traits. All traits responded predictably to glucocorticoid challenge. Genetic variation was observed in baseline measurements of all traits, with heritability estimates ranging from 0.21 +/- 0.03 to 0.60 +/- 0.06. Genetic variation in linear recovery from nadir values following dexamethasone administration was significant only for percentage CD4, percentage CD8, and for surface expression of MHC II. The genetic covariance between basal and linear recovery was positive and significant for percentage CD4, percentage CD8, and MHC II expression. The bovine lymphocyte antigen DRB3.2 locus accounted for significant proportions of total variation in percentage MHC II cells and MHC I expression. These results suggest that genetic variability exists for important basal and glucocorticoid-modified phenotypes of bovine mononuclear leukocytes, implying that immunocompetence traits impacted by this stress hormone may be enhanced by genetic selection.

Genetic selection programs for dairy cattle in many countries are reviewed, breeding goals are compared, and the degree of uniformity that exists and is required for international genetic programs for health traits is discussed. The most prevalent health disorders in dairy cattle are mastitis, infertility, lameness, milk fever, ketosis, metritis, and displaced abomasums. The manifestation of these disorders can be partly attributed to management and environmental factors, but there is evidence that each also has a genetic component. Health traits are genetically correlated with traits for which international genetic evaluations are routinely available from Interbull, including milk production, conformation, and udder health traits. Evaluations for longevity (length of herd life) are expected this summer. Genetic evaluations for female fertility traits are available in many countries and international evaluations are imminent. Effective selection using quantitative genetic approaches requires measurement and recording of phenotypes and frequent evaluation of candidates for selection. Producers use many different definitions to record health data and do not use a standardized format in on-farm or DHIA databases. Change will require significant time and effort by many people. Direct genotyping using DNA technologies offers potential for direct selection for genes causing health problems, but this is likely to be a slow and incomplete solution. Potential exists for genetic improvement of health in dairy cattle. Economic, social, and political forces will shape the changes that occur.

The objectives of this study were to estimate genetic correlations among body condition scores (BCS) from various sources, dairy form, and measures of cow health. Body condition score and dairy form evaluated during routine type appraisal was obtained from the Holstein Association USA, Inc. A second set of BCS was obtained from Dairy Records Managements Systems (DRMS) and was recorded by producers that use PCDART dairy management software. Disease observations were obtained from recorded veterinarian treatments in several dairy herds in the United States. Estimated breeding values for diseases in Denmark were also obtained. Genetic correlations among BCS, dairy form, and cow health traits in the United States were generated with sire models. Models included fixed effects for age, DIM, and contemporary group. Random effects included sire, permanent environment, herd-year season for health traits, and error. Predicted transmitting abilities (PTA) for BCS and dairy form were correlated with estimated breeding values for disease in Denmark. The genetic correlation estimate between BCS from DRMS and BCS from the Holstein Association USA, Inc., was 0.85. The genetic correlation estimate between BCS and a composite of all diseases in the United States was -0.79, and PTA for BCS was favorably correlated with an index of resistance to disease other than mastitis in Denmark (0.27). Dairy form was positively correlated with a composite of all diseases in the United States (0.85) and was unfavorably correlated with an index for resistance to disease other than mastitis in Denmark (-0.29). Adjustment for protein yield PTA had a minimal affect on correlations between PTA for BCS or dairy form and disease in Denmark. Selection for higher body condition or lower dairy form with continued selection for yield may slow deterioration in cow health as a correlated response to selection for increased yield.

Dairy products from milk of cows fed diets rich in polyunsaturated fatty acids have a more health-promoting fatty acid composition and are softer but often have oxidized flavors. Dairy products made from cow's milk that has more- or less-unsaturated fatty acid compositions were tested for differences in texture and flavor from those made from bulk-tank milk. The milk was manufactured into butter, vanilla ice cream, yogurt, Provolone cheese, and Cheddar cheese. The products were analyzed for fatty acid composition, physical properties, and flavor. Milk of cows with a more monounsaturated fatty acid composition yielded products with a more monounsaturated fatty acid composition that were softer and had a satisfactory flavor. Thus, selection of cows for milk fatty acid composition can be used to produce dairy products that are probably more healthful and have a softer texture.

Scant information is available on the levels of gene expression in the digestive system of cattle. A study was conducted to characterize transcript profiles in rumen, large intestine, small intestine and reference samples. The absolute intensities obtained from cDNA microarrays that included 7653 cattle and control sequences were used as indicators of the transcript levels. The experimental design included dye-swaps totaling six arrays and sequences were duplicated within array. Data normalization included a LOWESS fit to remove dependencies between tissue effect and average expression level. The remaining variation was analyzed using a linear mixed effects model including the effects of array, dye, gene, and gene by tissue. A total of 218 sequences were significant at P< 10 to the -6 power, of which 28 were significant at P< 10 to the -9 power. The 99.9% bootstrap confidence interval limits of tissue contrasts indicated that 625 genes were expressed at different levels between large and small intestines, 448 were different between the large intestine and rumen, and 401 were different between the small intestine and rumen. Multiple sequences associated with fatty acid metabolism were over expressed in the rumen with respect to the small and large intestines. This result is consistent with the high fatty acid absorbance that occurs in the wall of the rumen. In agreement with the high cell turnover rate of the intestinal epithelium, some Caspase genes were significantly under-expressed in the rumen, when compared to small and large intestines. These results augment the understanding of the gastrointestinal tract development, differentiation, and function and can be used in nutritional programs to optimize feed efficiency and metabolism.

The advantage of using the genotype of a quantitative trait locus (QTL) in selection schemes of dairy cattle was quantified using stochastic simulation. Three selection plans were studied. In the first plan, young bulls waited for 3 yr until their sisters completed a lactation and then were evaluated and selected based on an animal model. In a second plan, young bulls waited for 5 yr until their daughters completed a lactation. An intermediate 4-yr waiting plan was also studied. Simulation was for 16 yr with overlapping generations. Population and model parameters were proportional to the U.S. Holstein population. The advantage of using a QTL was quantified as the percentage of superiority of QTL-assisted over QTL-free selection using cumulative genetic response. Percentage of superiority was reported for four selection pathways: active sires, young bulls, bull dams, and first lactation cows. A general trend was observed: low superiority in early years of selection that increased to a plateau in later years and then decreased. The superiority of the QTL information was greatest in the 3-yr waiting plan and least in the 4-yr waiting plan. Superiority at plateau for selection pathways ranged from 16 to 26% for the 3-yr waiting plan, from 3 to 12% for the 4-yr waiting plan, and from 5 to 13% for the 5-yr waiting plan. The contribution to selection response attributed to the QTL and the polygenes was quantified. The rate at which the favorable allele approached fixation and the accuracy of predicting breeding values on the percentage of superiority were studied.

The atherogenic index (AI), defined as AI = [%C12:0 + 4 × %C14:0 + %C16:0] ÷ [Σ%unsaturated fatty acids], characterizes the atherogenicity of dietary fats. Fats with higher AI-values are assumed to be more detrimental to the human health. Previously, we demonstrated that properties of butter differ between cows on the same diet that produce milk fat with high and low AI. Butter from low AI milk fat was more spreadable. The objective of this experiment was to determine whether the difference in properties of butter as well as the production and composition of milk of cows with high and low AI can be affected differently by feeding additional dietary fish oil and soy oil. These diets have been shown previously to decrease the AI of milk fat. A 3×3 latin square design with one replication in summer and one in fall was used. Holstein cows (60-200 days in milk) that produced before the treatment period milk fat with low AI (n=6) and high AI (n=6) were fed for three 3-week feeding periods with either a control diet (3.66% fat) or diets that contained additionally 1% fish oil and 1% soy oil as roasted beans, respectively. Feed intake and milk production was recorded during the third week on each diet. Milk samples were collected twice during the third week and analyzed for milk fat, protein, lactose, total solids, somatic cell count, and fatty acid composition. Furthermore, butter was made and analyzed for penetration distance and creep. Cows preselected for a low AI of milk fat maintained a lower AI than did cows with a high AI (P ≤ 0.05). Feeding additional soy oil decreased the AI and increased the penetration distance in comparison to the control diet (P ≤ 0.05), whereas feeding additional fish oil had no significant effect (P ≥ 0.05). Feeding additional soy oil and fish oil increased numerically the difference in the response of AI and penetration distance, but the interactions were not statistically significant (P ≥ 0.05). Dry matter intake, milk production, and milk composition were not affected by AI or diet (P ≥ 0.05). We conclude that feeding additional soy oil and selecting cows with low AI act additively to produce a lower saturated milkfat that can be used to produce a more spreadable butter.

Changing the milk fatty acid composition can improve the nutritional and physical properties of dairy products and their acceptability to consumers. A more healthful milk fatty acid composition can be achieved by altering the cow's diet, for example, by feeding supplemental fish oil (FO) or roasted soybeans (RSB), or by selecting cows with a more unsaturated milk fatty acid composition. We examined whether feeding supplemental FO or RSB to cows that had a more unsaturated milk fatty acid composition acted additively to produce butter with improved fatty acid composition and texture. Using a 3 x 3 Latin square design with 2 replications, we fed diets to multiparous Holstein cows (60 to 200 DIM) chosen for producing either more or less unsaturated milk fatty acid composition (n = 6 for each group) for three 3-wk periods. The control diet contained 3.7% crude fat and the 2 experimental diets contained, on a dry matter basis, 0.8% of additional lipids in the form of 0.9% of FO or 5% of RSB. The milk, collected in the third week of feeding, was used to make butter, which was analyzed for its fatty acid composition and physical properties. Dry matter intake, milk yield, and milk composition were not significantly affected by cow diet or by cow selection. Cows that produced a more unsaturated and healthful milk fat prior to the feeding study, according to a "health-promoting index" [HPI = (sum of % of unsaturated fatty acids)/ (%12:0 + 4 x %14:0 + %16:0)], maintained a higher HPI in their butter during the feeding study than did cows with a low HPI. Milk from cows fed supplemental FO or RSB yielded more unsaturated butters with a higher HPI. This butter also was softer when the cows were fed RSB. Feeding RSB to cows chosen for their high milk HPI yielded the most unsaturated butter with the highest HPI and softest texture. Thus, selecting cows with a more health-promoting milk fatty acid composition and feeding supplemental RSB can be used in combination to produce butter that has a consumer-friendly texture and a healthful fatty acid profile.

Blood neutrophils use CD62L and CD18 adhesion molecules to contact and migrate rapidly through blood vessels in defense against infections in underlying tissues. Previous work showed that glucocorticoid hormones repress expression of CD62L and CD18, causing neutrophilia and increased mastitis susceptibility in dairy cows. The aim of this study was to determine whether bovine neutrophil sensitivity to glucocorticoids exhibits genetic variability. Test animals included 60 pedigreed Holstein bulls treated on 3 consecutive days with a synthetic glucocorticoid (dexamethasone) and five untreated control bulls. Five indicator traits of neutrophil glucocorticoid sensitivity were monitored, including circulating neutrophil counts and two measures on each of CD62L and CD18 expression. Random regression models with treatment-specific serial correlation were used to estimate genetic and non-genetic sources of variation before, during and after glucocorticoid administration. Significant genetic variation was observed for neutrophil CD18 expression, with longitudinal heritability estimates ranging from 0.10 to 0.54 and influenced by dexamethasone. Significant genetic variation was also observed for blood neutrophil counts (heritability estimates ranging from 0.11 to 0.24) but was not influenced by dexamethasone administration. Estimated genetic correlations between circulating neutrophil counts and various indicators of CD62L and CD18 expression were large and negative (-0.44 to - 0.78). These results imply significant genetic variability and pleiotropic effects for neutrophil traits that are important for stress-induced disease susceptibility in dairy cattle and might be exploited by genetic selection.

The superiority of selection schemes employing information about a known quantitative trait locus (QTL) over conventional schemes is examined for dairy cattle breeding schemes. Stochastic simulation of a dairy cattle population with selection practices, structures, and parameters similar to the US Holstein population was implemented. Additive genetic effects were estimated by an animal model. Two schemes were compared: a QTL-assisted selection scheme in which the genotype of a known QTL was accounted for in the animal model as a fixed factor, and a QTL-free selection scheme in which the QTL was simulated but was not fit separately in the animal model. Under the QTL-assisted selection scheme, all animals in the mixed model were assumed to be genotyped for the QTL.The effect of using QTL information on the genetic response, the frequency of the favorable QTL allele, and the accuracy of evaluation were examined. Moreover, the effect was studied in four distinct paths of selection: active sires, proven young bulls, bull dams, and first-lactation cows. Average superiority values of 4.6, 7.6, 11.7, and 1.1% for genetic response were observed over 16 yr of selection for active sires, young bulls, bull dams, and first-lactation cows, respectively. Frequency of the favorable QTL allele changed faster in bull dams than males, and was the slowest in first-lactation cows. Finally, accuracy of evaluation under the QTL-assisted selection scheme was higher than under the QTL-free selection scheme. Young bulls of the QTL-assisted selection scheme on average had 0.049 higher accuracy, and first-lactation cows had on average 0.185 higher accuracy than corresponding animals of the QTL-free selection scheme.

Teat-end shapes were categorized for 1443 Holstein cows with 3582 lactations, in the Iowa State University herd at Ankeny, approximately 40 d postpartum between 1970 and 1995.Frequencies of teat-end shapes were as follows: round, 52.2%; prolapsed, 0.8%; flat, 14.2%; plate, 3.4%; funnel, 8.9%; and mixed, 20.5%.Cows were coded as mixed if all four teat-end shapes were not the same.Heritability estimates were obtained with an animal model with pedigrees traced back to registration numbers roughly conforming to birth year 1955.The heritability estimates for first, second, and third and later lactations were 34, 21, and 13%, respectively.Lactation averages for linear somatic cell scores were adjusted for days in milk, and month and age at calving, and were available for 255 cows with 431 lactations categorized from 1992 to 1995.Frequencies of teat-end shape on the 255 cows were as follows: round, 58%; prolapsed, 3%; flat, 11%; plate, 2%; funnel, 6%; and mixed, 20%.Least-squares means of somatic cell score for categories of teat-end shape were computed from a mixed model that included year, parity, and teatend shape as fixed effects and cow as a random effect.Teat-end shape did not significantly affect somatic cell score.

Measurement of direct and correlated responses to single-trait selection for milk yield was the major objective of regional project NC-2.The NC-2 Technical Committee included representatives from Alaska, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Nebraska, South Dakota, Wisconsin, and the USDA.All representatives, except Illinois, Kansas and Nebraska, maintained a selection line formed by using AI sires selected for high estimated transmitting abilities for milk and a second line that served as some type of a control.Stations varied in criteria for selection of bulls for control lines.Farms were managed similarly, including feeding and management of selection and control lines as one herd, random mating within line, and restricted culling policies.Selection for milk yield effectively increased milk production.All selection lines increased milk and net income per lactation more than control lines.Realized gains matched or exceeded gains expected from estimates of breeding values.Yields of milk components increased, but component percentages decreased appreciably for selection lines.Reproduction of nulliparous animals was not affected, but days open for lactating selection cows increased in some of the individual projects.Selected cows tended to have larger health costs, specifically for mammary treatment.Udder and conformation traits did not deteriorate for selection lines, although control lines with selection of sires on genetic evaluations for type received higher type scores.There should be few reservations about undesirable responses correlated with selection for milk yield.

Measurement of direct and correlated responses to single-trait selection for milk yield was the major objective of regional project NC-2. The NC-2 Technical Committee included representatives from Alaska, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Nebraska, South Dakota, Wisconsin, and the USDA. All representatives, except Illinois, Kansas and Nebraska, maintained a selection line formed by using AI sires selected for high estimated transmitting abilities for milk and a second line that served as some type of a control. Stations varied in criteria for selection of bulls for control lines. Farms were managed similarly, including feeding and management of selection and control lines as one herd, random mating within line, and restricted culling policies. Selection for milk yield effectively increased milk production. All selection lines increased milk and net income per lactation more than control lines. Realized gains matched or exceeded gains expected from estimates of breeding values. Yields of milk components increased, but component percentages decreased appreciably for selection lines. Reproduction of nulliparous animals was not affected, but days open for lactating selection cows increased in some of the individual projects. Selected cows tended to have larger health costs, specifically for mammary treatment. Udder and conformation traits did not deteriorate for selection lines, although control lines with selection of sires on genetic evaluations for type received higher type scores. There should be few reservations about undesirable responses correlated with selection for milk yield.

A mitochondrial DNA (mtDNA) fragment containing the D-loop, phenylalanine tRNA, valine tRNA, and 12S and 16 rRNA genes was cloned and sequenced from 36 cows of 18 maternal lineages to identify the polymorphic sites within those regions and to detect the existence of heteroplasmic mtDNA in cows. Seventeen variable sites were observed within the D-loop and rRNA coding regions of bovine mtDNA within a 2.5-kb span. The hypervariable sites in the D-loop and rRNA coding regions were identified at nucleotide positions 169, 216, and 1594. Heteroplasmic mtDNA (variable mtDNA within a tissue) existed extensively in cows and was detected within the above regions in 11 of 36 cows sequenced. The insertion, deletion, and nucleotide transversion polymorphisms were found only in homopolymer regions. Heteroplasmy was observed frequently and seemingly is persistent in cattle. Though heteroplasmy was demonstrated, most lineages and mtDNA sites showed no heteroplasmy.

Phagocytosis and oxidative burst activity of polymorphonuclear neutrophil leukocytes (PMN) isolated from blood and pregnancy-associated glycoprotein (bPAG) concentrations in plasma were evaluated in two longitudinal studies in dairy cows from 3 weeks before until 5 weeks after calving, carried out in the United States and in Europe. Ingestion of Staphylococcus aureus by blood PMN increased during the first week after calving and normalised 3 weeks post-partum. Phagocytosis of Escherichia coli did not change in the early post-partum period. In both studies, a significant decrease in oxidative burst activity of PMN was observed between 1 and 3 weeks after calving. In all cows, a very significant increase in plasma bPAG concentration was found between 1 week before and 2 weeks after calving. The peak of bPAG concentration in plasma immediately preceded the alterations of blood PMN functions. These results suggest that bPAG may be associated with inhibition of PMN function of dairy cows during the early post-partum period.