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1.
    
In this study, the effects of breed composition and predictor dimensionality on the accuracy of direct genomic values (DGV) in a multiple breed (MB) cattle population were investigated. A total of 3559 bulls of three breeds were genotyped at 54 001 single nucleotide polymorphisms: 2093 Holstein (H), 749 Brown Swiss (B) and 717 Simmental (S). DGV were calculated using a principal component (PC) approach for either single (SB) or MB scenarios. Moreover, DGV were computed using all SNP genotypes simultaneously with SNPBLUP model as comparison. A total of seven data sets were used: three with a SB each, three with different pairs of breeds (HB, HS and BS), and one with all the three breeds together (HBS), respectively. Editing was performed separately for each scenario. Reference populations differed in breed composition, whereas the validation bulls were the same for all scenarios. The number of SNPs retained after data editing ranged from 36 521 to 41 360. PCs were extracted from actual genotypes. The total number of retained PCs ranged from 4029 to 7284 in Brown Swiss and HBS respectively, reducing the number of predictors by about 85% (from 82% to 89%). In all, three traits were considered: milk, fat and protein yield. Correlations between deregressed proofs and DGV were used to assess prediction accuracy in validation animals. In the SB scenarios, average DGV accuracy did not substantially change when either SNPBLUP or PC were used. Improvement of DGV accuracy were observed for some traits in Brown Swiss, only when MB reference populations and PC approach were used instead of SB-SNPBLUP (+10% HBS, +16%HB for milk yield and +3% HBS and +7% HB for protein yield, respectively). With the exclusion of the abovementioned cases, similar accuracies were observed using MB reference population, under the PC or SNPBLUP models. Random variation owing to sampling effect or size and composition of the reference population may explain the difficulty in finding a defined pattern in the results.  相似文献   

2.
    
Small reference populations limit the accuracy of genomic prediction in numerically small breeds, such like Danish Jersey. The objective of this study was to investigate two approaches to improve genomic prediction by increasing size of reference population in Danish Jersey. The first approach was to include North American Jersey bulls in Danish Jersey reference population. The second was to genotype cows and use them as reference animals. The validation of genomic prediction was carried out on bulls and cows, respectively. In validation on bulls, about 300 Danish bulls (depending on traits) born in 2005 and later were used as validation data, and the reference populations were: (1) about 1050 Danish bulls, (2) about 1050 Danish bulls and about 1150 US bulls. In validation on cows, about 3000 Danish cows from 87 young half-sib families were used as validation data, and the reference populations were: (1) about 1250 Danish bulls, (2) about 1250 Danish bulls and about 1150 US bulls, (3) about 1250 Danish bulls and about 4800 cows, (4) about 1250 Danish bulls, 1150 US bulls and 4800 Danish cows. Genomic best linear unbiased prediction model was used to predict breeding values. De-regressed proofs were used as response variables. In the validation on bulls for eight traits, the joint DK-US bull reference population led to higher reliability of genomic prediction than the DK bull reference population for six traits, but not for fertility and longevity. Averaged over the eight traits, the gain was 3 percentage points. In the validation on cows for six traits (fertility and longevity were not available), the gain from inclusion of US bull in reference population was 6.6 percentage points in average over the six traits, and the gain from inclusion of cows was 8.2 percentage points. However, the gains from cows and US bulls were not accumulative. The total gain of including both US bulls and Danish cows was 10.5 percentage points. The results indicate that sharing reference data and including cows in reference population are efficient approaches to increase reliability of genomic prediction. Therefore, genomic selection is promising for numerically small population.  相似文献   

3.
    
This study evaluated the dependence of reliability and prediction bias on the prediction method, the contribution of including animals (bulls or cows), and the genetic relatedness, when including genotyped cows in the progeny-tested bull reference population. We performed genomic evaluation using a Japanese Holstein population, and assessed the accuracy of genomic enhanced breeding value (GEBV) for three production traits and 13 linear conformation traits. A total of 4564 animals for production traits and 4172 animals for conformation traits were genotyped using Illumina BovineSNP50 array. Single- and multi-step methods were compared for predicting GEBV in genotyped bull-only and genotyped bull-cow reference populations. No large differences in realized reliability and regression coefficient were found between the two reference populations; however, a slight difference was found between the two methods for production traits. The accuracy of GEBV determined by single-step method increased slightly when genotyped cows were included in the bull reference population, but decreased slightly by multi-step method. A validation study was used to evaluate the accuracy of GEBV when 800 additional genotyped bulls (POPbull) or cows (POPcow) were included in the base reference population composed of 2000 genotyped bulls. The realized reliabilities of POPbull were higher than those of POPcow for all traits. For the gain of realized reliability over the base reference population, the average ratios of POPbull gain to POPcow gain for production traits and conformation traits were 2.6 and 7.2, respectively, and the ratios depended on heritabilities of the traits. For regression coefficient, no large differences were found between the results for POPbull and POPcow. Another validation study was performed to investigate the effect of genetic relatedness between cows and bulls in the reference and test populations. The effect of genetic relationship among bulls in the reference population was also assessed. The results showed that it is important to account for relatedness among bulls in the reference population. Our studies indicate that the prediction method, the contribution ratio of including animals, and genetic relatedness could affect the prediction accuracy in genomic evaluation of Holstein cattle, when including genotyped cows in the reference population.  相似文献   

4.
    
Today, almost all reference populations consist of progeny tested bulls. However, older progeny tested bulls do not have reliable estimated breeding values (EBV) for new traits. Thus, to be able to select for these new traits, it is necessary to build a reference population. We used a deterministic prediction model to test the hypothesis that the value of cows in reference populations depends on the availability of phenotypic records. To test the hypothesis, we investigated different strategies of building a reference population for a new functional trait over a 10-year period. The trait was either recorded on a large scale (30 000 cows per year) or on a small scale (2000 cows per year). For large-scale recording, we compared four scenarios where the reference population consisted of 30 sires; 30 sires and 170 test bulls; 30 sires and 2000 cows; or 30 sires, 2000 cows and 170 test bulls in the first year with measurements of the new functional trait. In addition to varying the make-up of the reference population, we also varied the heritability of the trait (h2 = 0.05 v. 0.15). The results showed that a reference population of test bulls, cows and sires results in the highest accuracy of the direct genomic values (DGV) for a new functional trait, regardless of its heritability. For small-scale recording, we compared two scenarios where the reference population consisted of the 2000 cows with phenotypic records or the 30 sires of these cows in the first year with measurements of the new functional trait. The results showed that a reference population of cows results in the highest accuracy of the DGV whether the heritability is 0.05 or 0.15, because variation is lost when phenotypic data on cows are summarized in EBV of their sires. The main conclusions from this study are: (i) the fewer phenotypic records, the larger effect of including cows in the reference population; (ii) for small-scale recording, the accuracy of the DGV will continue to increase for several years, whereas the increases in the accuracy of the DGV quickly decrease with large-scale recording; (iii) it is possible to achieve accuracies of the DGV that enable selection for new functional traits recorded on a large scale within 3 years from commencement of recording; and (iv) a higher heritability benefits a reference population of cows more than a reference population of bulls.  相似文献   

5.
    
Summary The effects of procedures generally used to reduce variation of lactation length on the efficiency of selection for milk yield are examined applying existing theory to a set of average literature estimates of heritabilities and correlations between lactation yield and length. Adjustment of milk yield for lactation length should be expected to remove more genetic than phenotypic variation, thus reducing selection efficiency in relation to unadjusted yield. Selecting individuals on an optimum index of lactation yield and length would be more efficient for improving yield than selecting on yield alone, while both criteria would have practically the same efficiency for selection on progeny test. This result could be applied to reduce milk recording frequency without losing selection accuracy. Culling on lactation length before selecting on yield would have little effect on individual selection efficiency. However, excluding short lactation records should be expected to reduce both selection accuracy of the progeny test and genetic variation in yield.  相似文献   

6.
    
Bulls frequently display male-male mounts, with consequences in the incidence of injuries, and possibly affecting the reproductive performance of the bulls. This behavior is known as the “buller syndrome” when appears in steers, with several individuals mounting one or a few penmates. The study aimed to collect information on the incidence of bull-bull mounts, the possible associated factors, the productive consequences, and management applied by distributing a survey to Holstein bull breeders in Uruguay. A survey was applied and responded by most Holstein breeders in Uruguay (30/33). Nineteen of the 30 breeders observed mounting behavior among bulls, and 15 of them considered it as a relevant problem. The breeders that observed the behavior had a greater number of bulls than those that did not observe it (P = 0.002). All of them observed that mounts were persistently directed towards the same individual (considering a specific period, while it remained in the group). Of these, 11 (58%) considered that this stopped only when the “buller” bull was removed from the group, mentioning that the behavior was frequently redirected to another individual. The mounts between bulls are a major problem in the breeding of Holstein bulls, with important consequences on weight gain and animal health, reproductive problems such as low libido and seminal quality, and even provoking the death of animals. Although not all breeders reported the existence of the problem, those with the bigger herds did. While some management and/or environmental conditions seem to influence (higher density, regrouping, managements that involve movement of animals, and spring) the incidence of bull-bull mounts, there are no standardized managements to avoid this behavior. Considering that most breeders were interested in including practices to minimize this problem if available, it would be essential to understand better the causes and predisposing factors to decrease its negative impacts.  相似文献   

7.
    
A total of 1922 first generation crossbred cows born between 2005 and 2012 produced by inseminating purebred Israeli Holstein cows with Norwegian Red semen, and 7487 purebred Israeli Holstein cows of the same age in the same 50 herds were analyzed for production, calving traits, fertility, calving diseases, body condition score, abortion rate and survival under intensive commercial management conditions. Holstein cows were higher than crossbreds for 305-day milk, fat and protein production. Differences were 764, 1244, 1231 for kg milk; 23.4, 37.4, 35.6 for kg fat, and 16.7, 29.8, 29.8 for kg protein; for parities 1 through 3. Differences for fat concentration were not significant; while crossbred cows were higher for protein concentration by 0.06% to 0.08%. Differences for somatic cells counts were not significant. Milk production persistency was higher for Holstein cows by 5, 8.3 and 8% in parities 1 through 3. Crossbred cows were higher for conception status by 3.1, 3.6 and 4.7% in parities 1 through 3. Rates of metritis for Holsteins were higher than the crossbred cows by 7.8, 4.6 and 3.4% in parities 1 to 3. Differences for incidence of abortion, dystocia, ketosis and milk fever were not significant. Holstein cows were lower than crossbred cows for body condition score for all three parities, with differences of 0.2 to 0.4 units. Contrary to comparisons in other countries, herd-life was higher for Holsteins by 79 days. A total of 6321 Holstein cows born between 2007 and 2011 were higher than 765 progeny of crossbred cows backcrossed to Israeli Holsteins of the same ages for milk, fat and protein production. Differences were 279, 537, 542 kg milk; 10.5, 17.7, 17.0 kg fat and 6.2, 12.9, 13.2 kg protein for parities 1 through 3. Differences for fat concentration were not significant, while backcross cows were higher for protein percentage by 0.02% to 0.04%. The differences for somatic cell score, conception rate, and calving diseases other than metritis, were not significant. Holstein cows were lower than backcross cows by 1.5% to 2.5% for conception status in parities 1 to 3 and lower for body condition score for parities 1 and 2, with differences in the range of 0.06 to 0.09 units. Culling rates were higher, and herd-life lower for the crossbred cows. The gains obtained in secondary traits for crossbred cows did not compensate for the major reduction in production.  相似文献   

8.
A number of cattle breeds have become highly specialized for milk or beef production, following strong artificial selection for these traits. In this paper, we compare allele frequencies from 9323 single nucleotide polymorphism (SNP) markers genotyped in dairy and beef cattle breeds averaged in sliding windows across the genome, with the aim of identifying divergently selected regions of the genome between the production types. The value of the method for identifying selection signatures was validated by four sources of evidence. First, differences in allele frequencies between dairy and beef cattle at individual SNPs were correlated with the effects of those SNPs on production traits. Secondly, large differences in allele frequencies generally occurred in the same location for two independent data sets (correlation 0.45) between sliding window averages. Thirdly, the largest differences in sliding window average difference in allele frequencies were found on chromosome 20 in the region of the growth hormone receptor gene, which carries a mutation known to have an effect on milk production traits in a number of dairy populations. Finally, for the chromosome tested, the location of selection signatures between dairy and beef cattle was correlated with the location of selection signatures within dairy cattle.  相似文献   

9.
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10.
Morphologically normal embryos were transferred surgically into uteri of normal and repeat-breeder cows at seven days post-estrus to compare embryo survival rates in the two kinds of cows. All cows were less than ten years of age and had no abnormal genital discharges, cystic ovarian follicles, or anatomical abnormalities of the reproductive tract. Normal cows had not been inseminated after last calving. Repeat-breeders had at least four infertile services within the past six months (average of 6.2 services after calving). To test fertility of repeat-breeders at synchronized estrus, 22 anatomically-normal repeat-breeders were treated by intramuscular (i.m.) injection with prostaglandin F(2)alpha (PGF(2)alpha) on day 11 of an estrous cycle (estrus = day 0) and inseminated at induced estrus; 11 cows (50%) had a normal fetus at necropsy on day 60. Twenty-three repeat-breeders and 23 normal cows were assigned as embryo recipients and treated i.m. with PGF(2)alpha to synchronize estrus. All embryo donors were normal cows. Donors were treated with FSH and PGF(2)alpha and inseminated at estrus. On day 7 after estrus, embryos were recovered nonsurgically from donors and one embryo was transferred through a flank incision to the anterior end of the uterine horn adjacent to the corpus luteum of each recipient. Recipients that did not return to estrus were necropsied at day 60. Of 28 normal and 23 repeat-breeder recipients, 23 normal cows (82%) and 16 repeat breeders (70%) were pregnant at day 60 (P=0.235). Thus, at seven days post-estrus, the maternal environment of most of these repeat-breeders was satisfactory for maintaining pregnancy.  相似文献   

11.
日粮能量水平对奶牛生殖激素分泌的研究   总被引：1，自引：0，他引：1  
选择发情周期为21天、产后9天~63天的第一胎中国荷斯坦奶牛24头,分为三组,设置三个能量水平,研究对奶牛生殖激素分泌的影响。结果表明:母牛的能量状况与促乳素的相关系数r=-0.9618(P<0.01),与生长激素的相关系数r=-0.7435,在能量负平衡阶段,能量状况与胰岛素值为负相关,在能量正平衡阶段,能量状况与胰岛素值为正相关。发情持续期前第7周的能量值与雌二醇浓度相关系数r=0.9675(P<0.01),与孕酮的相关系数r=-0.7129,黄体期前第7周和第8周的能量值与雌二醇的相关系数分别为0.8099和0.5775,与孕酮的相关系数分别为0.8263和0.6502,因此,在分娩前2周提高日粮能量水平,不仅会提高发情鉴定率,更能提高受胎率,对于高产奶牛,同时控制产后2周泌乳量,可有效缓解能量负平衡,达到提高发情鉴定率和受胎率的目的。  相似文献   

12.
  总被引：1，自引：0，他引：1  
The objective of this study was to quantify the genetic association of body energy assessed throughout lactation with a cow's fertility. Nine direct and indirect body energy traits were defined at different stages of lactation. Four were daily records of energy balance, energy content, cumulative effective energy (CEE) and body condition score (BCS) calculated between lactation days 4 and 311. The other five traits included duration of negative energy balance (DNEB), rate of recovery during DNEB (RNEB), sum of negative energy balance (SNEB), nadir of energy content (NEC) and number of days from calving to NEC. Of these traits, energy balance, DNEB, RNEB and SNEB were primarily based on individual cow feed intake and milk yield, and considered direct measures of body energy. The other traits were calculated from body lipid and protein changes, predicted from BCS and live weight profiles, and were considered indirect measures of body energy. Fertility was defined by number of days between calving and commencement of luteal activity (DLA), first observed oestrus (DH) and conception (DC), and number of services per conception. A total of 957 cows in their first four lactations were considered in the study. Genetic models fitted cubic splines to define longitudinal traits (energy balance, energy content, CEE and BCS) and calculate heritability and genetic correlation with fertility. Daily heritability estimate ranges were 0.10 to 0.34, 0.35 to 0.61, 0.32 to 0.53 and 0.24 to 0.56 for energy balance, energy content, CEE and BCS, respectively, and, in most cases, tended to increase towards the middle of lactation and remain relatively stable thereafter. Of the other body energy traits, heritability of NEC (0.44) was the most notable. Statistically significant (P < 0.05) genetic correlations of DH with daily energy balance, energy content, CEE and BCS ranged from -0.16 to -0.28, -0.35 to -0.48, -0.16 to -0.26 and -0.37 to -0.44, respectively. For DC, respective estimates were -0.28 to -0.64, -0.37 to -0.60, -0.30 to -0.48 and -0.29 to -0.53. For DLA, they ranged from -0.47 to -0.56 with energy content and from -0.50 to -0.74 with BCS. Of special interest was the genetic correlation of NEC with DH (-0.54) and DC (-0.48). Results suggest that indirect measures of body energy have the strongest genetic association with cow fertility. NEC and early lactation (circa day 50) BCS and energy content are the most useful traits for selection in terms of the correlated improvement in a cow's capacity to resume her reproductive activity post partum.  相似文献   

13.
    
There is increasing interest in the use of continuous housing systems for dairy cows, with various reasons put forward to advocate such systems. However, the welfare of dairy cows is typically perceived to be better within pasture-based systems, although such judgements are often not scientifically based. The aim of this review was to interrogate the existing scientific literature to compare the welfare, including health, of dairy cows in continuously housed and pasture-based systems. Although summarising existing work, knowledge gaps and directions for future research are also identified. The scope of the review is broad, examining relevant topics under three main headings; health, behaviour and physiology. Regarding health, cows on pasture-based systems had lower levels of lameness, hoof pathologies, hock lesions, mastitis, uterine disease and mortality compared with cows on continuously housed systems. Pasture access also had benefits for dairy cow behaviour, in terms of grazing, improved lying/resting times and lower levels of aggression. Moreover, when given the choice between pasture and indoor housing, cows showed an overall preference for pasture, particularly at night. However, the review highlighted the need for a deeper understanding of cow preference and behaviour. Potential areas for concern within pasture-based systems included physiological indicators of more severe negative energy balance, and in some situations, the potential for compromised welfare with exposure to unpredictable weather conditions. In summary, the results from this review highlight that there remain considerable animal welfare benefits from incorporating pasture access into dairy production systems.  相似文献   

14.
    
In order to describe the temporal evolution of milk yield (MY) and composition in extended lactations, 21 658 lactations of Italian Holstein cows were analyzed. Six empirical mathematical models currently used to fit 305 standard lactations (Wood, Wilmink, Legendre, Ali and Schaeffer, quadratic and cubic splines) and one function developed specifically for extended lactations (a modification of the Dijkstra model) were tested to identify a suitable function for describing patterns until 1000 days in milk (DIM). Comparison was performed on individual patterns and on average curves grouped according to parity (primiparous and multiparous) and lactation length (standard ⩽305 days, and extended from 600 to 1000 days). For average patterns, polynomial models showed better fitting performances when compared with the three or four parameters models. However, LEG and spline regression, showed poor prediction ability at the extremes of the lactation trajectory. The Ali and Schaeffer polynomial and Dijkstra function were effective in modelling average curves for MY and protein percentage, whereas a reduced fitting ability was observed for fat percentage and somatic cell score. When individual patterns were fitted, polynomial models outperformed nonlinear functions. No detectable differences were observed between standard and extended patterns in the initial phase of lactation, with similar values of peak production and time at peak. A considerable difference in persistency was observed between 200 and 305 DIM. Such a difference resulted in an estimated difference between standard and extended cycle of about 7 and 9 kg/day for daily yield at 305 DIM and of 463 and 677 kg of cumulated milk production at 305 DIM for the first- and second-parity groups, respectively. For first and later lactation animals, peak yield estimates were nearly 31 and 38 kg, respectively, and occurred at around 65 and 40 days. The asymptotic level of production was around 9 kg for multiparous cows, whereas the estimate was negative for first parity.  相似文献   

15.
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16.
    
This paper reviews strategies and methods to improve accuracies of genomic predictions from the perspective of a numerically small population. Improvements are realized by influencing one or both of the main factors: (1) improve or increase genomic connections to phenotypic records in training data. (2) Models and strategies to focus genomic predictions on markers closer to the causative variants. Combining populations into a joint reference population results in high improvements when combining populations of the same breed and diminishes as the genetic distance between populations increases. For distantly related breeds sophisticated Bayesian variable selection models in combination with denser markers sets or functional subsets of markers is needed. This is expected to be further improved by the efficient use of sequence information. In addition predictions can be improved by the use of phenotypes of genotyped and non-genotyped cows directly. For a small population the optimal approach will combine the above components.  相似文献   

17.
AIMS: To examine factors affecting faecal shedding of the foodborne pathogens Escherichia coli O157:H7 and Salmonella in dairy cattle and evaluate antimicrobial susceptibility of these isolates. METHODS: Faecal samples were obtained in replicate from lactating (LAC; n = 60) and non-lactating (NLAC; n = 60) Holstein cattle to determine influence of heat stress, parity, lactation status (LAC vs NLAC) and stage of lactation [60 days in milk (DIM)] and cultured for E. coli O157:H7 and Salmonella. A portion of the recovered isolates were examined for antimicrobial susceptibility using the broth microdilution technique. RESULTS: No effects of heat stress were observed. Lactating cows shed more (P < 0.01) E. coli O157:H7 than NLAC cows (43% vs 32%, respectively). Multiparous LAC cows tended to shed more (P = 0.06) Salmonella than primiparous LAC cows (39% vs 27%, respectively). Parity did not influence (P > 0.10) bacterial shedding in NLAC cows. Cows 60 DIM. Seventeen Salmonella serotypes were identified with the most prevalent being Senftenberg (18%), Newport (17%) and Anatum (15%). Seventy-nine of the Salmonella isolates were resistant to at least one of the seven antibiotics. Escherichia coli O157:H7 isolates were resistant to 11 different antibiotics with multiple resistance to nine or more antibiotics observed in five isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated differences in the shedding patterns of foodborne pathogens due to the stage of the milk production cycle and may help identify times when on-farm pathogen control would be the most effective.  相似文献   

18.
Aims:  The aim of this study was to determine variation of prevalence throughout a year, colonization levels and genotypes of Campylobacter jejuni in Finnish dairy cattle herds.
Methods and Results:  Faecal samples and tank milk samples from three dairy cattle herds were taken five times, and swab samples from drinking troughs once during a 1-year sampling period. The samples were enriched in Bolton broth and subsequently spread on mCCDA. Isolates were then subtyped by pulsed-field gel electrophoresis using SmaI. Campylobacter jejuni was detected in 169 of the 340 faecal samples and in one drinking trough sample. Prevalences between herds and sampling times varied widely. The faecal levels of C. jejuni were mainly low. Between one and four SmaI subtypes were identified from each herd per sampling. Two SmaI subtypes persisted in two of the herds throughout the study.
Conclusions:  Dairy cattle can be a long-term reservoir of C. jejuni subtypes similar to clinical isolates. Differences in the colonization potential among C. jejuni strains as well as in the resistance to campylobacter colonization among animals are possible.
Significance and Impact of the Study:  The study provides data on contamination dynamics, colonization levels and the persistence of C. jejuni in dairy cattle.  相似文献   

19.
    
The objective of this study was to estimate heritabilities for and genetic correlations among different pathogen-specific mastitis traits. The traits were unspecific mastitis, which is all mastitis treatments regardless of the causative pathogen as well as mastitis caused by Streptococcus dysgalactiae, Escherichia coli, coagulase-negative staphylococci (CNS), Staphylococcus aureus and Streptococcus uberis. Also groups of pathogens were investigated, Gram-negative v. Gram-positive and contagious v. environmental pathogens. Data from 168 158 Danish Holstein cows calving first time between 1998 and 2006 were used in the analyses. Variances and covariances were estimated using uni- and bivariate threshold models via Gibbs sampling. Posterior means of heritabilities of pathogen-specific mastitis were lower than the heritability of unspecific mastitis, ranging from 0.035 to 0.076 for S. aureus and S. uberis, respectively. The heritabilities of groups of pathogen ranged from 0.053 to 0.087. Genetic correlations among the pathogen-specific mastitis traits ranged from 0.45 to 0.77. These estimates tended to be lowest for bacteria eliciting very different immune responses, which can be considered as the overall pleiotropic effect of genes affecting resistance to a specific pathogen, and highest for bacteria sharing characteristics regarding immune response. The genetic correlations between the groups of pathogens were high, 0.73 and 0.83. Results showed that the pathogen-specific traits used in this study should be considered as different traits. Genetic evaluation for pathogen-specific mastitis resistance may be beneficial despite lower heritabilities than unspecific mastitis because a pathogen-specific mastitis trait is a direct measure of an udder infection, and because the cost of a mastitis case caused by different pathogens has been shown to differ greatly. Sampling bias may be present because there were not pathogen information on all mastitis treatments and because some farms do not record pathogen information. Therefore, improved recording of pathogen information and mastitis treatments in general is critical for a successful genetic evaluation of udder health. Also, economic values have to be specified for each pathogen-specific trait separately.  相似文献   

20.
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