Effects of breed and region on longevity traits through five years of age in Brown Swiss, Holstein, and Jersey cows in the United States

The objective of this study was to assess breed, and breed × region interactions for several longevity-related traits, measured up to 5 yr of age in Brown Swiss, Holstein, and Jersey cows in 7 regions of the United States. Data were analyzed using logistic, poisson, and linear models, and survival analyses. The traits were stayability (yes/no survived to 5 yr of age), number of completed lactations, days lived, herd-life, and days in milk (DIM) to 5 yr of age. Probable lifetime DIM were also estimated using data from the first 5 yr of age of the cows. Herd-life was defined as the days lived up to 5 yr of age minus the age at first calving. Days in milk consisted of herd-life up to 5 yr of age minus the dry periods. Three data files were analyzed: herds with one breed of cows, herds with Holstein and Brown Swiss, and herds with Holstein and Jersey cows. Breed × region interaction was usually significant, with larger effects for the southern regions. Jerseys obtained largest values for the ratio of DIM to days lived, and for the number of completed lactations to 5 yr of age. Brown Swiss had the largest probabilities of surviving to 5 yr of age (stayabilities) in all regions. For the other traits, the results for Brown Swiss were inconsistent, but usually the cows of this breed had shorter herd-life and DIM to 5 yr of age than Holsteins. Brown Swiss cows were expected to have more total DIM in their lifetime in the Southeast than Holsteins. Survival analysis gave the most readily interpretable information, although the linear, poisson, and logistic analyses answered slightly different questions. Adjustment for herd size did not modify the results.     

Effect of Holstein Friesian and Brown Swiss breeds on quality of milk and cheese

In Italy, more than 75% of milk is used for cheese making. For this reason, milk composition and coagulation traits and cheese quality represent the most important tools for the economic development of the dairy sector. In particular, cheese quality varies in relation to cheese-making technology and breed of cow. The aim of this study was to investigate the effect of 3 types of milk, originating from Holstein-Friesian (HF), Brown Swiss (BS), and mixed of both breeds, on vat milk characteristics, cheese yield, and quality in 3 different typical Italian cheese-making conditions (Casolet, Vezzena, and Grana Trentino). One hundred forty-four cows (66 HF and 78 BS) were involved, and a total of 24 vats of milk were evaluated. At maturity, 30, 21, and 16 wheels of Casolet, Vezzena, and Grana Trentino cheese were analyzed. Brown Swiss cows yielded 9% less milk per day than HF cows, but milk showed greater contents of protein, casein, titratable acidity, and better rennet coagulation time and curd firmness than HF milk. The chemical composition and cholesterol content of the 3 types of cheese were similar between breeds, whereas the cheese made with BS milk showed greater contents of monounsaturated and polyunsaturated fatty acids. Cheese made with BS milk had greater b* (yellow component) than HF. Cheese yield, recorded at different ripening times, demonstrated that BS milk yielded more cheese than HF. Mixed milk showed values, on average, intermediate to HF and BS milk characteristics, and this trend was confirmed in cheese yield at different ripening times.     

Response of Holstein and Brown Swiss cows fed alfalfa hay-based diets to supplemental methionine at two stages of lactation

In this study, we evaluated the effects of dietary supplementation at two stages of lactation with various levels of Mepron85 (M85) and M85 plus DL-methionine (DL-Met) on milk production and composition of Holstein and Brown Swiss cows fed an alfalfa-hay and corn grain-based diet. In experiment 1, control diets were formulated to supplement, in early lactation [days in milk (DIM) = 73.2], concentrations of metabolizable methionine at 104% of the estimated requirements based on the Cornell Net Carbohydrate and Protein System. Treatment groups were fed the control diet plus 10, 20, or 30 g/d of M85 at 116, 128, or 139% of the estimated requirements for metabolizable methionine. The supplementation with 10 g/d in Brown Swiss and 30 g/d of M85 in Holstein cows increased milk yields and fat percentage, but had no effects on protein percentage. These data suggested that the estimated postruminal supply of metabolizable methionine in the control ration was limiting for maximum milk fat synthesis. Conversely, in experiment 2, the cosupplementation with M85 (15 g/d) plus DL-Met (15 g/d) to cows in midlactation (DIM = 140.5) did not influence fat percentage, but increased protein yield and percentage (+0.1%) in both Holstein and Brown Swiss, and lactose percentage (+0.18%) in Holstein cows. The supplementation with 15 g/d of M85 reduced milk and protein yields, whereas 15 g/d of DL-Met reduced protein percentage in four of the five experimental weeks for Holstein cows. We conclude that supplementation with M85, alone or in combination with DL-Met, may be used to influence milk composition, but these effects are influenced by dosage and type of supplemental methionine, breed, and stage of lactation.     

Composition of the milks of dairy cattle. II. Ash, calcium, magnesium, and phosphorus.

Milks from commercial dairy herds in Southeastern Pennsylvania were analyzed for ash, calcium, magnesium, and phosphorus. Milk samples were from single milkings of 151 healthy purebred cows in midlactation. The data represent market milk composition. Average values for all animals were ash .78%, calcium 1.25 g/liter, magnesium .11 g/liter, and phosphorus 1.14 g/liter. The data also were grouped and analyzed by breed and beta-lactoglobulin phenotype. Breeds differed in all inorganic components with 18 to 33 cows per breed. No differences in ash, calcium, magnesium, or phosphorus were significant when the data were grouped by beta-lactoglobulin phenotype.     

Effects of age, parity, season of calving, and sire on milk yield of Carora cows in Venezuela

Age-parity-season of calving, mature equivalent factors were developed for the Carora breed of Venezuela from more than 13,000 244-d milk yield records from the Venezuelan milk recording program from 1975 to 1986. Age-parity-season interactions with parity-age were most important for young cows and seasonal effects most important for old cows. Multiplicative factors were verified as useful to adjust milk yields of Carora and Brown Swiss crossbred cows. Repeatabilities for mature equivalent adjusted milk were .47, .36, and .38 between pairs of repeated records through fourth lactation. Heritability of milk in first lactation by REML procedures was 12% based on 44 Carora sires with 14 effective daughters per sire. Small population size for Carora cattle hinders usefulness and cost effectiveness of progeny testing as the primary investment in genetic gain. Greater potential economy is likely from exploiting the dams of sires genetic pathway.     

Detailed macro- and micromineral profile of milk: Effects of herd productivity,parity, and stage of lactation of cows of 6 dairy and dual-purpose breeds

The aim of this study was to quantify the major sources of variation in the levels of 15 minerals in individual milk samples collected from cows raised in multibreed dairy herds. The herds (n = 27) were classified into 2 categories, according to milk productivity. Milk productivity was based on the net energy of lactating cows' average daily milk yield. Milk samples were collected from 240 cows of 6 different breeds: 3 specialized dairy (Holstein-Friesian, Brown Swiss, and Jersey) and 3 dual-purpose (Simmental, Rendena, and Alpine Grey). The samples were analyzed for macro-elements (Na, Mg, P, S, K, and Ca), essential micro-elements (Mn, Fe, Cu, Zn, and Se), and environmental micro-elements (B, Si, Sr, and Sn), using inductively coupled plasma–optical emission spectrometry. Data were analyzed using a linear mixed model that included fixed effects of days in milk (DIM), parity, breed, and herd productivity, and a random effect of herd-date within productivity level. Results showed that the effect of herd-date varied across minerals. It was especially large for environmental minerals (ranging from 47 to 91% of total variance) and ranged from 11 to 61% for macrominerals and essential microminerals. Milk samples collected from farms with a high level of herd productivity had a richer mineral profile than samples from low-productivity herds. Parity only influenced macrominerals, with the exception of S and Ca, while DIM influenced almost all minerals, with a few exceptions among the environmental elements. Differences in mineral profile were small between specialized and dual-purpose breeds, but they were large within the group of the specialized cows. These breed differences were reduced after adjusting for milk quality and yield, particularly in the case of milk Mg, S, Ca, Mn, and Zn levels. Milk samples from the Jersey and Brown Swiss cows had higher mineral levels (Sn excluded) than milk from the Holstein-Friesian cows; the other breeds of Alpine origin produced milk of intermediate quality. Our findings suggest that breed has a stronger effect on macrominerals and some of the essential microminerals than herd productivity, parity, and DIM. The modification of the mineral profile in milk seems possible for many minerals, but it likely depends on genetics (e.g., breed, selection) and on environmental and management factors in variable proportions according to the mineral considered.     

Genetic parameters for yield,fitness, and type traits in US Brown Swiss dairy cattle

The objective of this research was to evaluate heritabilities and genetic correlations among yield, fitness, and type traits for US Brown Swiss cattle born in 2000 and later. The data set used consisted of 108,633 first through fifth lactation records from 45,464 cows for yield, somatic cell score (SCS), days open, and productive life. Approximately half of the records had observations for 17 type traits and 41,074 had observations for milking speed. These data were analyzed using a series of 3 trait models. Heritability estimates of each trait were similar to previously reported values for both Holsteins, and Brown Swiss in other countries. Milk, fat, and protein yield had strong positive genetic correlations with productive life (0.67 to 0.71), whereas days open and SCS had strong negative correlations with productive life (?0.60 and ?0.69, respectively). Days open was more unfavorably correlated with dairy form (angularity) than with yield. The genetic correlation of udder depth and milk yield was unfavorable (?0.40), whereas rear udder height (0.20) and width (0.48) were favorably correlated with milk yield. Udder depth had a favorable genetic correlation with SCS (?0.26). Type traits with the strongest genetic correlations with productive life were fore udder attachment, mobility, and final score (0.44, 0.50, and 0.57, respectively). These updated genetic parameters will allow for improved genetic selection within the Brown Swiss breed.     

Effects of casein haplotypes on milk production traits in Italian Holstein and Brown Swiss cattle

The objective of this study was to estimate the effects of different haplotypes of the casein genes on milk production traits in Italian dairy cattle. Traits of interest were yields of milk, fat, and protein, and percentages of fat and protein in milk. The data included 728 multiparous records from 347 Holsteins and 773 records from 298 Brown Swiss cows. Records were preadjusted for effects of age and parity, season of calving, and region, and expressed as deviations from herdmate averages. Twenty half-sib families were represented in each breed. Haplotype probabilities were estimated for each animal and phenotypes were regressed on these probabilities. Nine haplotypes were observed in Holsteins and 17 were identified among the Brown Swiss. For Holsteins, significant effects were observed for protein percentage, with some indication of an effect for fat percentage. For the Brown Swiss, effects of haplotypes were significant for milk yield and fat and protein percentages. Effects were strongest for protein percentage. Correlation coefficients of solutions across breeds tended to be strong and positive, indicating that the same haplotypes had similar estimated effects in the 2 breeds. Although the data were limited (<350 cows in each study), this latter result may suggest that genes in the casein complex itself are responsible for the effects observed, rather than loci that are physically linked on either side of the casein cluster.     

Effects of pasture allowance on the yield and composition of milk from cows of different beta-lactoglobulin phenotypes

The objective of this study was to determine whether the differences in the composition of milk from cows of different beta-lactoglobulin beta-LG) phenotypes are affected by the amount of pasture available and, hence, pasture dry matter intake. Twenty-two Friesian cows of each of the AA and BB variants of the beta-LG phenotype were subjected to ad libitum grazing or restricted grazing in crossover experiments during spring (early lactation, approximately 60 d in milk) and summer (mid to late lactation, approximately 180 d in milk). Milk samples were collected from each cow at the end of each 8-d treatment period and analyzed for composition. Cows of the AA variant of the beta-LG phenotype had higher concentrations of whey protein and beta-LG, but lower concentrations of casein (CN), alpha-CN, kappa-CN (summer only), and BSA, than cows of the BB variant. Compared with cows with a restricted allowance, cows grazing ad libitum had higher milk yields and concentrations of protein, casein, whey protein, and all individual proteins except BSA and immunoglobulin. There were no interactions between effects of pasture allowance and phenotype on milk yield or composition. The data show that having adequate pasture for grazing cows is important not only to maximize milk yield, but also to optimize concentrations of protein and casein, and hence the manufacturing potential of milk. Further, the differences in composition of milk from cows of differing beta-LG phenotypes persisted during short-term restrictions in pasture allowance, and between spring and summer.     

Milk, fat, protein, somatic cell score, and days open among Holstein, Brown Swiss, and their crosses

The objectives of this study were to compare Holstein (HO), Brown Swiss (BS), and their crosses for milk, fat, and protein yields, somatic cell score (SCS), days open (DO), and age at first calving (AFC), and to estimate the effects of heterosis and recombination. First through fifth lactation records were obtained from 19 herds milking crosses among BS and HO. The edited data set included 6,534 lactation records from 3,473 cows of the following breed combinations: 2,125 pure HO, 926 pure BS, 256 BS sire × HO dam (SH), 105 backcrosses to BS (SX), 18 HO sire × BS dam, and 43 backcrosses to HO. Least squares means for daily milk, fat, and protein yields, mature-equivalent milk, fat, and protein yields, SCS, DO, and AFC were calculated for breed combinations with a model that included fixed effects of age within parity (except for AFC), days in milk for daily yield and SCS, herd-year-season of calving, and breed combination. Cow and error were random effects. Breed combination was replaced with regressions on coefficients for heterosis and recombination in a second analysis. Last, data were analyzed with a 5-trait animal model that included a single pedigree file for both breeds and coefficients for heterosis and recombination. The least squares means for fat production were 1.21, 1.15, 1.27, and 1.16 kg for HO, BS, SH, and SX, respectively, which corresponds to a heterosis estimate of 7.30% and a recombination estimate of −3.76%. Heterosis and recombination estimates for protein production were 5.63% and −3.31%, respectively. Heterosis estimates increased for fat yield (10.38%) and protein yield (7.07%) when maternal grandsire identification from a known artificial insemination sire was required. Regression coefficients indicated an 11.44-d reduction in DO due to heterosis. Heterosis estimates for SCS were inconsistent. Regression on heterosis for SCS was significant and favorable (−0.22) when the breed of sire was BS, but nonsignificant and unfavorable when sire breed was HO (0.43). Heterosis estimates were favorable for all traits, whereas recombination effects tended to be unfavorable for yield traits. Reduced performance of future generations did not appear to be the result of inseminating crossbred cows with inferior sires. Results indicated that first-generation crosses among BS and HO compared favorably with HO. Yield in subsequent generations was somewhat below expectations, perhaps due to recombination loss in HO.     

Crossbred and purebred dairy cattle in warm and cool seasons

This study was to determine if breed groups ranked differently in warm (May to August) and cool (November to February) seasons of calving and to determine if heterosis was more important in the warm season. A total of 719 records of cows in first lactation in four herds in the southeastern United States were used. Breeds were Holsteins, Brown Swiss, and Jerseys and the crosses among them. Milk and milk fat yields were greater in the cool season than in the warm season. Holsteins exceeded other breeds for milk and milk fat yield in both seasons, but their superiority was less among cows calving from May through August. Days open were longer for Holsteins, particularly in the warm season. In the cool season only the 3/4 Holstein X 1/4 Swiss group exceeded Holsteins for milk, but two groups--1/2 Holsteins X 1/2 Swiss and 5/8 Holstein X 1/4 Swiss-1/8 Jersey--were higher in the warm season. In the cool season three crossbred groups--1) 1/2 Holstein X 1/2 Swiss (Holstein sires), 2) 3/4 Holstein X 1/4 Swiss, and 3) 1/2 Holstein X 1/4 Swiss-1/4 Jersey--had greater milk fat yields than Holsteins, and a fourth--1/2 Holstein X 1/2 Jersey--yielded an equal amount. In the warm season six of the eight crossbred groups had greater milk fat yields than Holsteins. More crossbreds exceeded Holsteins in the warm than in the cool season, suggesting interactions for yields. There was slightly more heterosis in warm than in cool seasons for all traits.     

Fertility traits of Holstein,Brown Swiss,Simmental, and Alpine Grey cows are differently affected by herd productivity and milk yield of individual cows

Milk yield has a strong effect on fertility, but it may vary across different herds and individual cows. Therefore, the aim of this study was to assess the effects of breed and its interaction with level of milk production at the herd level (Herd-L) and at a cow-within-herd level (Cow-L) on fertility traits in dairy cattle. Data were gathered from Holstein (n = 17,688), Brown Swiss (n = 32,697), Simmental (n = 27,791), and Alpine Grey (n = 13,689) cows in northeastern Italy. The analysis was based on records from the first 3 lactations in the years 2011 to 2014. A mixed model was fitted to establish milk production levels of the various herds (Herd-L) and individual cows (Cow-L) using milk as a response variable. The interval fertility traits were interval from calving to first service, interval from first service to conception, and number of days open. The success traits were nonreturn rate at 56 d after first service, pregnancy rate at first service, and the number of inseminations. The interval from calving to first service, interval from first service to conception, and number of days open were analyzed using a Cox's proportional hazards model. The nonreturn rate at 56 d after first service, pregnancy rate at first service, and the number of inseminations were analyzed using logistic regression. There was a strong interaction between breed and productivity class at both Herd-L and Cow-L on all traits. The effects of herd and cow productivity differed from each other and differed among breeds. The dual-purpose Simmental and Alpine Grey breeds had better fertility than the specialized Holstein and Brown Swiss dairy cows; this difference is only partly attributable to different milk yields. Greater herd productivity can result in higher fertility in cows, whereas higher milk yield of individual cows within a herd results in lower fertility. These effects at both Herd-L and Cow-L are curvilinear and are stronger in dual-purpose breeds, which was more evident from low to intermediate milk yield levels than from central to high productivity classes. Disentangling the effects of milk productivity on fertility at Herd-L and Cow-L and taking the nonlinearity of response into account could lead to better modeling of populations within breed. It could also help with management—for example, in precision dairy farming of dairy and dual-purpose cattle. Moreover, assessing the fertility of various breeds and their different responses to herd and individual productivity levels could be useful in devising more profitable crossbreeding programs in different dairy systems.     

Differences in body temperature regulation during heat stress and seasonal depression in milk yield between Holstein,Brown Swiss,and crossbred cows

It is not clear whether cattle that are genetically superior in regulation of body temperature during heat stress are also better able to sustain milk production during hot conditions. Objectives were to evaluate differences in body temperature regulation during heat stress between Holstein, Brown Swiss, and crossbred cows under semi-tropical conditions and test whether the seasonal depression in milk yield was greater for genetic groups less able to regulate body temperature. For the first objective, conducted during heat stress, vaginal temperature was measured at 15-min intervals for 5 d in 133 pregnant lactating cows. Vaginal temperatures were affected by time and interaction between genetic group and time. Vaginal temperatures were higher for Holsteins for most times of the day. Moreover, the maximum daily vaginal temperature was higher for Holstein (39.8 ± 0.1°C) than for Brown Swiss (39.3 ± 0.2°C) or crossbreds (39.2 ± 0.1°C). For the second objective, 6,179 lactation records from 2,976 cows were analyzed to determine effects of genetic group and season of calving (cool season = Oct to March; warm season = April to Sept) on 305-d milk yield. Milk yield was affected by genetic group and season but not by the interaction of genetic group and season. The difference in average 305-d milk yield between cows calving in cool versus hot weather was 310 kg (4% decrease) for Holstein, 480 kg (7% decrease) for Brown Swiss, and 420 kg (6% decrease) for crossbreds. In conclusion, Brown Swiss and crossbreds regulated body temperature during heat stress better than Holsteins but these breeds were not more resistant to heat stress with respect to milk yield. Thus, genetic differences in thermotolerance are likely to exist that are independent of regulation of body temperature.     

Growth and reproduction characteristics of purebred and crossbred dairy cattle in first lactation

Breed additive, maternal, and heterozygotic effects on 11 monthly postpartum body weights, average size, weight gain, age at first calving, and days open were estimated by linear regression analyses from records of 680 purebred and crossbred animals. Calving year, age, and milk yield were significant environmental effects. Positive regressions of age on body weights indicated late calving cows were heaviest postpartum and had most days open. Negative regressions of milk yield on weight gain and postpartum weight showed greatest losses of weight associated with highest yields. There were breed differences in growth; purebreds highest to lowest were Brown Swiss, Holstein, Red Dane, Jersey, and Ayrshire and for weight gain, Brown Swiss, Ayrshire, and for weight gain, Brown Swiss, Ayrshire, Jersey, Holsteins, and Red Dane. Crosses were superior to purebreds in these traits. Additive effects of Holstein were greater than Ayrshire, Jersey, and Red Dane for postpartum body weights and average size. All constants for heterozygotic effect combinations were significant for postpartum weights and average size. Heterozygosity effects increased in magnitude with advancing lactation. Generally, age at first calving and postpartum interval to conception reflected little heterozygotic or maternal effects. There was some indication of breed differences in mean and additive effects for age at first calving.     

Associations between casein haplotypes and milk production traits of Swiss Brown cattle

Effects of casein haplotypes and beta-lactoglobulin (LG) genotypes on milk protein fractions and on daughter yield deviations for milk performance traits were estimated from a daughter design. Offspring of seven Swiss Brown sires with the haplotypes B-A-B-A and B-A-B-B for alpha s1-, alpha s2-, beta-, and kappa-caseins were selected. The milk of daughter groups with paternal haplotype B-A-B-A was associated with lower casein content and higher whey protein content compared with B-A-B-B. Because of these contrary effects, the true protein content was not affected by the paternal haplotypes. The effects of maternal haplotypes were significant on true protein and casein content but not on whey protein content. The beta-LG genotypes had highly significant effects on casein and whey protein content. The effect of beta-LG BB was positive on casein and negative on whey protein content compared with beta-LG AA; the effect of beta-LG AB was intermediate. No significant effects of paternal haplotypes were found for daughter yield deviation on kilograms of milk, fat, and protein or percentages of fat and protein. The effects of the beta-LG genotypes were, independent of the parental haplotypes, close to significant on daughter yield deviation for percentage of protein. The beta-LG BB tended to be associated with a higher protein content compared with beta-LG AA. The effects for beta-LG genotypes showed additive gene effects. The analysis of paternal haplotypes within sires revealed a contrary effect of haplotypes for two of the seven sires for casein content. The paternal haplotypes within sire showed, although not significant, that haplotypes of the two sires had a contrary effect on daughter yield deviation for percentage of protein as well.     

Production and reproduction of Fleckvieh,Brown Swiss,and 2 strains of Holstein-Friesian cows in a pasture-based,seasonal-calving dairy system

The first objective of this study was to compare the productive and reproductive performance of Holstein-Friesian (CH HF), Fleckvieh (CH FV), and Brown Swiss (CH BS) cows of Swiss origin with New Zealand Holstein-Friesian (NZ HF) cows in pasture-based compact-calving systems; NZ HF cows were chosen as the reference population for such grazing systems. The second objective was to analyze the relationships within and between breeds regarding reproductive performance, milk yield, and body condition score (BCS) dynamics. On 15 commercial Swiss farms, NZ HF cows were paired with Swiss cows over 3 yr. Overall, the study involved 259 complete lactations from 134 cows: 131 from 58 NZ HF, 40 from 24 CH HF, 43 from 27 CH FV, and 45 from 25 CH BS cows. All production parameters were affected by cow breed. Milk and energy-corrected milk yield over 270 d of lactation differed by 1,000 kg between the 2 extreme groups; CH HF having the highest yield and CH BS the lowest. The NZ HF cows had the greatest milk fat and protein concentrations over the lactation and exhibited the highest lactation persistency. Body weight differed by 90 kg between extreme groups; NZ HF and CH BS being the lightest and CH HF and CH FV the heaviest. As a result, the 2 HF strains achieved the highest milk production efficiency (270-d energy-corrected milk/body weight^0.75). Although less efficient at milk production, CH FV had a high 21-d submission rate (86%) and a high conception rate within 2 inseminations (89%), achieving high pregnancy rates within the first 3 and 6 wk of the breeding period (65 and 81%, respectively). Conversely, poorer reproductive performance was recorded for CH HF cows, with NZ HF and CH BS being intermediate. Both BCS at nadir and at 100 d postpartum had a positive effect on the 6-wk pregnancy rate, even when breed was included in the model. The BCS at 100 d of lactation also positively affected first service conception rate. In conclusion, despite their high milk production efficiency, even in low-input systems, CH HF were not suited to pasture-based seasonal-calving production systems due to poor reproductive performance. On the contrary, CH FV fulfilled the compact-calving reproduction objectives and deserve further consideration in seasonal calving systems, despite their lower milk production potential.     

Effects of dietary protein supply on caseins, whey proteins, proteolysis and renneting properties in milk from cows grazing clover or N fertilized grass.

The objective of this work was to examine whether variation in the amino acid supply to cows could be a reason for the reduced casein content and poorer renneting properties of milk that often occur in late summer, or whether these effects are related to proteolysis in the raw milk. In a 2 x 2 x 2 factorial design, we investigated the effects of sward (clover v. rye-grass) and supplementary feed with a high or low level of rumen-soluble N or of rumen undegradable protein on milk protein composition during the grazing season. A total of 32 Danish Holstein cows were included in the experiment. Milk protein and casein contents and the ratios casein N:total N and casein:true protein were at a minimum in late summer, whereas the contents of urea, non-protein N and whey protein were higher during this period. These seasonal effects were unrelated to either the type of supplementary feed or the type of sward; neither were they clearly related to proteolysis, although casein: true protein was related to the proteose peptone content. The results indicated that whey proteins other than alpha-lactalbumin or beta-lactoglobulin accounted for the higher proportion or concentration of whey protein in late summer. Based on a principal component analysis including variables such as citric acid, lactose and non-protein N, we suggest that the cows' energy supply during this period may be a critical factor in determining the milk protein composition, although our results were not conclusive. There was an interaction between the supplement of rumen undegradable protein and type of sward. When clover was grazed, a high supplement increased the concentrations of protein and casein in milk and the kappa-casein: total casein ratio. When rye-grass was grazed, the opposite response was found, and overall milk protein yield was not affected. The very low N content of clover in early summer reduced milk protein and casein protein during this period.     

Economic merit of crossbred and purebred US dairy cattle

Heterosis and breed differences were estimated for milk yield traits, somatic cell score (SCS), and productive life (PL), a measure of longevity. Yield trait data were from 10,442 crossbreds and 140,421 purebreds born since 1990 in 572 herds. Productive life data were from 41,131 crossbred cows and 726,344 purebreds born from 1960 through 1991. The model for test-day yields and SCS included effects of herd-year-season, age, lactation stage, regression on sire's predicted transmitting ability, additive breed effects, heterosis, and recombination. The model for PL included herd-year-season, breed effects, and general heterosis. All effects were assumed to be additive, but estimates of heterosis were converted to a percentage of the parent breed average for reporting. Estimates of general heterosis were 3.4% for milk yield, 4.4% for fat yield, and 4.1% for protein yield. A coefficient of general recombination was derived for multiple-breed crosses, but recombination effects were not well estimated and small gains, not losses, were observed for yield traits in later generations. Heterosis for SCS was not significant. Estimated heterosis for PL was 1.2% of mean productive life and remained constant across the range of birth years. Protein yield of Brown Swiss x Holstein crossbreds (0.94 kg/d) equaled protein yield of purebred Holsteins. Fat yields of Jersey x Holstein and Brown Swiss x Holstein crossbreds (1.14 and 1.13 kg/d, respectively) slightly exceeded that of Holsteins (1.12 kg/d). With cheese yield pricing and with all traits considered, profit from these crosses exceeded that of Holsteins for matings at breed bases. For elite matings, Holsteins were favored because the range of evaluations is smaller and genetic progress is slower in breeds other than Holstein, in part because fewer bulls are sampled. A combined national evaluation of data for all breeds and crossbreds may be desirable but would require an extensive programming effort. Animals should receive credit for heterosis when considered as mates for another breed.     

Composition, coagulation properties and Parmigiano-Reggiano cheese yield of Italian Brown and Italian Friesian herd milks

The authors report the results of a study aimed at the comparison of the basic chemical composition, the main protein fractions distribution, rennet coagulation properties and Parmigiano-Reggiano cheese yield of vat milk from Italian Brown and Italian Friesian herds. Parmigiano-Reggiano cheese factories which manufacture milk separately from Italian Brown herds and Italian Friesian herds were used in the study. Thirteen cheesemaking trials were performed at 10 different commercial cheese factories. The study was carried out from March to October 2003. For each cheesemaking trial in each factory, approximately 1100 kg milk from Italian Brown cows and from Italian Friesian cows were processed in parallel. The animals involved in the study came from farms with comparable management practices, size, location, number of lactation and days in milking. Each vat contained milk obtained by combining milk collected during the evening milking (partially skimmed milk by natural creaming) and the following morning milking (full-cream milk), from at least 2 dairy herds. Milk from Italian Brown cows is characterised by a higher casein content (27.1 v. 23.7 g/kg; P < or = 0.0001) than Italian Friesian cows' milk. Curd firming time (k20) of Italian Brown cows' milk was markedly lower than that of Italian Friesian cows' milk (6.6 v. 10.0 min; P < or = 0.001). This implies a higher rate of aggregation of para-casein micelles for Italian Brown cows' milk. The coagulum of Italian Brown cows' milk had better rheological properties and lower losses of fat in the cheese whey. Parmigiano-Reggiano cheese yield at 24 h was also higher for Italian Brown cows' milk, + 0.99 kg cheese for every 100 kg vat milk.     

Effects of breed,farm intensiveness,and cow productivity level on cheese-making ability predicted using infrared spectral data at the population level

Fourier-transform infrared (FTIR) spectra collected during milk recording schemes at population level can be used for predicting novel traits of interest for farm management, cows' genetic improvement, and milk payment systems. The aims of this study were as follows. (1) To predict cheese yield traits using FTIR spectra from routine milk recordings exploiting previously developed calibration equations. (2) To compare the predicted cheese-making abilities of different dairy and dual-purpose breeds. (3) To analyze the effects of herds' level of intensiveness (HL) and of the cow's level of productivity (CL). (4) To compare the patterns of predicted cheese yields with the patterns of milk composition in different breeds to discern the drivers of cheese-making efficiency. The major sources of variation of FTIR predictions of cheese yield ability (fresh cheese or cheese solids produced per unit milk) of individual milk samples were studied on 115,819 cows of 4 breeds (2 specialized dairy breeds, Holstein and Brown Swiss, and 2 dual-purpose breeds, Simmental and Alpine Grey) from 6,430 herds and exploiting 1,759,706 FTIR test-day spectra collected over 7 yr of milk sampling. Calibration equations used were previously developed on 1,264 individual laboratory model cheese procedures (cross-validation R² 0.85 and 0.95 for fresh and solids cheese yields, respectively). The linear model used for statistical analysis included the effects of parity, lactation stage, year of calving, month of sampling, HL, CL, breed of cow, and the interactions breed × HL and breed × CL. The HL and CL stratifications (5 classes each) were based on average daily secretion of milk net energy per cow. All effects were highly significant. The major conclusions were as follows. (1) The FTIR-based prediction of cheese yield of milk goes beyond the knowledge of fat and protein content, partially explaining differences in cheese-making ability in different cows, breeds and herds. (2) Differences in cheese yields of different breeds are only partially explained by milk fat and protein composition, and less productive breeds are characterized by a higher milk nutrient content as well as a higher recovery of nutrients in the cheese. (3) High-intensive herds not only produce much more milk, but the milk has a higher nutrient content and a higher cheese yield, whereas within herds, compared with less productive cows, the more productive cows have a much greater milk yield, milk with a greater content of fat but not of protein, and a moderate improvement in cheese yield, differing little from expectations based on milk composition. Finally, (4) the effects of HL and CL on milk quality and cheese-making ability are similar but not identical in different breeds, the less productive ones having some advantage in terms of cheese-making ability. We can obtain FTIR-based prediction of cheese yield from individual milk samples retrospectively at population level, which seems to go beyond the simple knowledge of milk composition, incorporating information on nutrient retention ability in cheese, with possible advantages for management of farms, genetic improvement of dairy cows, and milk payment systems.