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PubMed1994

Inclusion of semen price of the sire in an animal model to account for preferential treatment.

Histories of semen price for AI bulls used from 1970 to 1991 were collected and merged with first lactation milk and fat records of Ontario Holstein cows calving from 1970 through 1990. Data were analyzed with two animal models, both of which included herd-year-season and animal additive genetic effects. The second model included a fixed effect for semen price group. Cows that did not have a semen price for their sire were assigned to a separate group. Both models were used for milk and fat yields, and the second model was used separately for the semen price group of the sire at the time of daughter's conception, birth, and first calving. Hypothesis testing of group differences for semen price (excluding the group without a price match) resulted in significant effects of price group at first calving for milk and fat yields. The changes in estimated breeding values for cows and sires were summarized for cows by year of calving and for sires by Canadian versus US. Very few animals were affected by the inclusion of semen price groups in the model. Inclusion of effects of semen price group in an animal model did not significantly improve the accuracy of animal evaluations.

Animal Husbandry↗

PubMed1994

Effects of feeding practices on milk fat concentration for dairy cows.

Thirty-seven dairy farms, using high producing (7500 kg/yr per cow on average) Montbéliarde cows that were fed hay-based rations, were included in a detailed survey involving the structure of the farm and the herd, the quality of forage, the feeding practices in winter and summer, and genetic characteristics of the cows (breeding values and herd effects). These data were used to analyze variation in milk fat concentration among farms, particularly variation linked to environmental factors, as assessed by the herd effect. When farms were ranked according to herd effect of fat concentration, farms with the highest herd effects fed concentrate to cows in rolled form, distributed forage before or with the concentrate, and provided hay in the trough in summer. The effects of such practices on digestive phenomena in the rumen are discussed. This study supported the use of herd effects to identify factors related to variation in dairy cow performance.

Animal Feed↗

PubMed1994

Deaths and disposals in lines selected for milk yield and control lines of Jersey cattle.

Deaths and disposals of Jerseys from birth to 120 d of first lactation during a selection experiment were summarized. Cows were randomly assigned to the high milk yield and young sire lines. Service sires were bulls with the highest estimated breeding value for milk for the high milk line and a collection of all young unproven bulls available in AI in 1967. Cattle that were unsuitable for conditions of normal herd management were candidates for culling. Culling of uncalved heifers and of lactating cows was also permitted to maintain group sizes. Culling for herd reduction was random. Culling for low milk yield was permitted after cows reached 120 d of first lactation. Death and disposal data were analyzed through 120 d of first lactation. By 120 d of first lactation, 29.6% of females born to the young sire line had died or been involuntarily removed compared with 29.8% born to the high milk yield line. Deaths were 54.8% of total losses for the high milk yield line compared with 58.4% for the young sire line. Stillbirths were a larger proportion of total losses for animals in the high milk yield line (21.4%) than for those in the young sire line (15.3%). The most frequent cause of death was scours and pneumonia during 1st mo of life for animals in both lines. Selection of sires for high milk yield does not decrease total survival rates through the early first lactation.

Animal Husbandry↗

PubMed1995

Association of alleles for the class I bovine lymphocyte antigens with conformation, semen traits, and growth rate of young bulls.

The 279 Norwegian bulls that were performance tested during 1988 and 1989 were typed for bovine lymphocyte antigens of class I, and relationships with performance test results of these bulls were investigated. A single-trait animal model was used to estimate the gene substitution effects of bovine lymphocyte antigens on conformation as well as semen volume, density, and quality; a fixed linear model was also applied to the breeding values of growth rate. Allelic frequencies ranged from .2 to 28%; alleles w16 (28%), A2 (15%), A10(w50) (12%), and A8 (10%) were the most frequent. Allele A12(A30) was significantly associated with decreased semen density and decreased growth rate, and allele A10(w50) was significantly associated with increased growth rate. No antigen showed a significant association with conformation, semen density, or semen quality. Heterozygosity at the locus for bovine lymphocyte antigen of class I did not show significant advantage in any of the traits. The bovine lymphocyte antigens appeared to be potential markers for quantitative trait loci controlling semen density and growth rate; however, further research is necessary to confirm these findings.

Alleles↗

PubMed1995

Mastitis of periparturient Holstein cattle: a phenotypic and genetic study.

Environmental and genetic factors affecting somatic cell scores, clinical mastitis, and IMI by minor and major pathogens were studied on 137 periparturient Holstein cows selected for milk production. Environmental effects were obtained by generalized least squares and logistic regression. Genetic parameters were from BLUP and threshold animal models. Lactation number affected the number of quarters with clinical mastitis and the number of quarters infected with minor pathogens. The DIM affected somatic cell score and number of quarters infected with major pathogens. Heritabilities for all mastitis indicators averaged 10%, but differences occurred among the indicators. Correlations between breeding values of the number of quarters infected with minor pathogens and the number infected with major pathogens were antagonistic and statistically significant.

Animals↗

PubMed1996

Effects of days dry, previous days open, and current days open on milk yields of cows in Zimbabwe and North Carolina.

Effects of days dry and previous and current days open on milk yields during the first three lactations were determined for Holsteins from Zimbabwe and North Carolina. The animal models used included animal; permanent environmental effects of cows for herd-year, month of calving, age, current days open, and DIM; and the inverse of additive numerator genetic relationships. Model 1 for first lactations included only these effects, but Model 2, the animal model for later lactations, included these effects plus previous days open, previous days dry, and previous milk yield. The dependent variable in both models was unadjusted milk yield for the lactation. Current and previous days open, previous days dry, and DIM were also fitted as dependent variables with Models 1 and 2, except for previous milk yield, when appropriate. As current days open increased, milk yield rose, regardless of milk yield during prior lactations. Milk yields were reduced for lactations following < 60 d dry and showed little advantage for longer dry periods. The effects of previous days open are real but are overestimated unless permanent environmental effects of cows are considered simultaneously. The heritabilities and repeatabilities of current and previous days open and previous days dry were higher for cows in Zimbabwe than for those in North Carolina. Results suggest that, to obtain unbiased estimates of breeding values of sires and cows, yield data should be adjusted for the environmental effects of days dry as well as those of previous and current days open.

Animals↗

PubMed1997

Estimation of variance of maternal lineage effects among Canadian Holsteins.

Bayesian posterior estimates of variances of maternal lineage effects were obtained with a procedure that used Gibbs sampling. Data were records of yield during first parity from 245,510 Holstein cows that calved in Canada between 1990 and 1994. Maternal lineages were defined by tracing the maternal ancestry of cows to common female ancestors. Traits were standardized yields of milk, fat, and protein and percentages of fat and protein. Estimates of maternal lineage variance were < 0.5% of the total variance for all traits. Effects of this size hardly affected the cow rankings for estimated breeding value. Another analysis defined maternal lineages by establishing groups of dams and their daughters in an attempt to maximize the variance of environmental effects associated with maternal lineages, but only 1.1% of the variance in milk yield was associated with effects of the dam and daughter groups. Analyses of simulated data indicated that positive estimates of maternal lineage effects were not a result of restriction of estimates to positive values and that estimates of maternal lineage variance were biased slightly downward because of incomplete pedigree information. The partitioning of maternal lineage and additive genetic variance was correct when pedigree information was complete, according to results from simulation.

Animals↗

PubMed1998

Effect of monensin on milk production by Holstein and Jersey cows.

Effects of the administration of monensin via concentrates to dairy cows were studied in two trials. In one trial, 64 Holstein cows were assigned to four groups that received 0, 150, 300, or 450 mg/d of monensin from 5 to 24 wk postpartum. Milk production tended to increase (4.0, 3.3, and 5.4%, respectively) for the three groups of treated cows. Fat content was decreased by 0.09, 1.89, and 4.09 g/kg, respectively, for these same three groups. The effect on protein content was small and nonsignificant. Feed intake was reduced in treated cows, although not significantly, and feed efficiency was improved by monensin. In a confirmatory trial, 58 Holstein and 22 Jersey cows were allocated either to a control group or to a treatment group that received 300 mg/d of monensin from 5 to 36 wk postpartum during the first lactation and from 2 wk before calving to 36 wk postpartum during a subsequent lactation. During the first lactation, cows in the treatment group showed a 7% increase in milk production, a relative decrease (1.4 g/kg) in milk fat content, and equal protein content compared with cows in the control group. Body weight gain and body condition scores near the end of the treatment period were higher for cows in the treatment group. A decrease in blood ketone concentrations was found between 7 and 56 d of lactation. Treatment effects on milk production differed between breeds and within genetic lines. Jersey cows were less responsive than were Holstein cows, and Holstein cows with a high ratio of breeding values for protein and fat showed larger milk production responses. Results from the second lactation showed similar differences between the two groups as did those from the first lactation.

3-Hydroxybutyric Acid↗

PubMed1999

Effect of genetic merit and concentrate feeding on reproduction of grazing dairy cows in a subtropical environment.

This study was conducted to determine the effects of genetic merit for milk production and concentrate feeding on the intervals to the onset of postpartum cyclic ovarian activity, first insemination, and establishment of pregnancy. Other factors considered included biochemical measures of energy balance, liveweight, and measures of production. A farmlet study was conducted with two lines of cattle that differed in Australian Breeding Value by 735 L milk and 47 kg of fat plus protein that were fed 300 or 2000 kg of concentrate per cow per year in a subtropical grazing system based on ryegrass, clover, and kikuyu pasture. Milk yield was higher in cows fed 2000 kg of concentrate per cow per year (23.6 L/d) than those fed 300 kg/cow per year (18.2 L/d), and cows of medium genetic merit (19.6 L/d) produced less milk than those of high genetic merit (22.2 L/d). Plasma glucose concentration was lower in the cows of high genetic merit (3.11 mmol/L), than in the cows of medium genetic merit (3.39 mmol/L). The cumulative probabilities of ovulation, insemination, and establishment of pregnancy by any day postpartum were determined by a Weibull distribution. Medium genetic merit cows in winter were more likely to ovulate by any day postpartum than in summer and more likely than high genetic merit cows in either summer or winter. The cumulative probability of insemination was lower in primipara than multipara and in summer than in winter. Primiparous cattle had a lower cumulative probability of pregnancy by any day postpartum.

Animal Feed↗

PubMed2026

Validation of a national genetic evaluation for methane emission in Holstein cattle.

Lactanet Canada launched a genomic evaluation for methane efficiency for Holsteins in April 2023, utilizing milk mid-infrared-predicted methane (CH4) emissions (CH4MIR) as a proxy. This study validated the methane efficiency genomic evaluation using genotyped cows with CH4MIR and CH4 records from GreenFeed systems (CH4GF), along with relative breeding values (RBV) for methane production and methane efficiency from the April 2023 evaluation. In Lactanet's methane efficiency evaluation, a higher RBV indicates more desirable, lower-emitting animals. For the validation, RBV were categorized into quintiles for the CH4MIR dataset and tertiles for the CH4GF dataset to evaluate trends across the RBV distribution. Mean CH4MIR decreased progressively across RBV quintiles for both traits, with all pairwise comparisons among quintiles significantly different. Similarly, CH4GF emissions declined across RBV tertiles, with significant differences observed between the lowest and highest tertiles. Additional analyses using RBV threshold categories confirmed that cows with the highest RBV consistently exhibited lower methane emissions. Linear regression analyses further demonstrated a negative relationship between RBV and methane emissions, supporting the predictive ability of the genomic evaluation. These findings confirm that Canada's genomic evaluation for methane efficiency effectively differentiates cows by methane emission potential, reinforcing its potential as a tool for genetic selection to reduce methane emissions in dairy cattle.

Journal Article↗

PubMed1993

Effect of divergent selection for immune responsiveness and of major histocompatibility complex on resistance to Marek's disease in chickens.

Lines of chickens selected for nine generations for high (H) or low (L) antibody response to SRBC, a randombred control (C) line, and an F1 cross between H and L lines were challenged for resistance to Marek's disease (MD). Hens only were challenged at day-old by contact with virulent MD Strain K. Birds were serologically typed for MHC erythrocyte antigens. Chicks from the L and H lines died earlier and later, respectively, than the C chicks, whereas time of death did not differ between F1 birds and the L chicks. Mortality in the L line (70.1%) was higher than in the C line (42.8%), but mortality in the H line (40.9%) was not lower than in the C line or the F1 cross (47.5%). Effects of MHC genotypes and haplotypes on mortality from MD were estimated within lines with a logistic regression model. Effect of MHC was moderate in the H line (P < .10) and highly significant in the C line (P < .005). Effects of MHC genotypes were similar in the H and C line but differed in the L and F1. Heritability of mortality from MD estimated with a threshold model including relationships between individuals was .40 when all lines were grouped together, whereas heritability estimated for each line separately was .45, .51, and .78 in the H, C, and L lines, respectively. Correlations between estimated breeding values for antibody response to SRBC and mortality from MD varied between lines and sexes. Correlations also were affected by whether or not the MHC effect was taken into account.

Animals↗

PubMed1994

Direct and correlated responses to multitrait, divergent selection for immunocompetence.

Leghorn lines had been selected for an immunocompetence index based on four traits: antibody production to Mycoplasma gallisepticum (MG) and Pasteurella multocida (PM) vaccines, reticuloendothelial clearance of colloidal carbon (CCA), and cell-mediated, wing web response to phytohemagglutinin (PHA). The purpose of this study was to produce replicated lines of chickens with divergent levels of multitrait immunocompetence by index selection. The objectives of analyses of Generations 5 to 7 of this study was to characterize these lines with respect to immune-response traits, correlations among these traits, and correlated responses in other important production traits. Differences (P < .05) existed between the lines selected for high or low immune response and between the two replicates in mean breeding values and in individual immune-response traits. Averages of heritability estimates, weighted by number of offspring and pooled across three generations (two cycles of selection), estimated by using sire variance components and parent-offspring correlations were, respectively, .16 and .09 for the index, .31 and .08 for MG, .21 and -.02 for PM, .06 and .05 for CCA, and .08 and .12 for PHA. Realized heritabilities (response divided by effective selection differential) pooled across the two selection cycles, were .19 and .11 for the index, .06 and -.01 for MG, .44 and .32 for PM, 1.52 and -1.21 for CCA, and .48 and .15 for PHA, for Replicates 1 and 2, respectively. Phenotypic correlations among traits were generally small, and several estimates were negative. Estimates of genetic correlation varied widely. Juvenile and adult body weights, age of first egg, 32-wk egg weight, and rate of egg production were analyzed to evaluate effects of selection on these traits of direct economic importance. Very few differences were noted.

Age Factors↗

PubMed2000

[Study of mapping QTLs for milk traits on the German dairy cattle].

A total of 1,130 bulls belonging to 20 half-sib families of German dairy cattle were genotyped for 229 microsatellite markers on 30 chromosomes. The data were used in an attempt to map quantitative trait loci applying regression as multiple-marker regression. For association analysis with a granddaughter design, the estimated breeding values for 3 milk traits were used: milk production, fat production and protein production. The empirical values of significance thresholds were determined by using a permutation test on the experimental data. Several significant QTLs were found on some chromosomes, especially on the chromosome 14. The results give a strong support for the experiments of Coppieters et al. and Ron et al.

Animals↗

PubMed2000

Preliminary results on embryo rescue for circumventing hybridization barriers in Asparagus.

Garden asparagus, Asparagus officinalis, is reproductively isolated from a related ornamental species with potential breeding value, Asparagus densiflorus cv. Sprengeri, by pre- and post-zygotic barriers. The latter barrier operates at the endosperm level five days after pollination in A. officinalis x A. densiflorus crosses. To try to circumvent this barrier, in vitro embryo rescue using ovule and ovary cultures was tested. Controlled interspecific crosses were made and 2,032 ovules and 826 ovaries were cultured three days after pollination under various culture media and incubation conditions. Ovaries cultured for 60 days became red (similar to mature fruits), but seed formation was incomplete. Transfer of ovules to other media was necessary to promote embryo development. The interspecific embryos increased their length from 35 microns at the initiation of culture to 1,900 microns after 120 days of culture, but seedlings were not obtained. Histological studies revealed differentiation of protoderm only. The possible causes of the failure of the embryos to complete differentiation and morphogenesis are discussed.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2001

[Influences on the occurrence of abomasal displacements in German Holstein cows].

The objectives of this study were to analyse risk factors for the prevalence of abomasal displacement in German Holstein cows. In the period from 02/01/1999 to 01/31/2000 five veterinary surgeons in Northern Lower Saxony registered all cases of abomasal displacement in German Holstein cows being under the official milk recording scheme. In total, the investigation included 160 farms and 9315 cows. An abomasal displacement was registered in 151 German Holstein cows, corresponding to a frequency of 1.6%. More than 75% of the abomasal displacements appeared during the first 30 days after calving. The left abomasal displacement (74.8%) was recorded more often than the right abomasal displacement (25.2%). Milk recording and pedigree data were supplied by the VIT (Vereinigte Informationssystem Tierhaltung), Verden, and merged with the own recordings. The influences of the calving month, the lactation number, the age at calving, the inbreeding coefficient, calving performance, duration of pregnancy, breed of calf sire, calf sire and the breeding values for the milk performance did not explain a significant part of the variation of the frequency of the abomasal displacement. Significant effects of the sire, birth of twins or even more calves and the herd were obtained for the leftsided abomasal displacement. For the rightsided abomasal displacement and for all abomasal displacements the herd effect was not significant. Heritability estimates using bivariate linear REML models were h2 = 0.043 +/- 0.012 for the leftsided abomasal displacement, and h2 = 0.007 +/- 0.004 for the rightsided abomasal displacement, respectively. Using the threshold model the heritabilities yielded estimates of h2 = 0.51 for the left abomasal displacement, and for the right abomasal displacement of h2 = 0.19, respectively.

Abomasum↗

PubMed2001

Potential accuracy of genetic evaluation for calving difficulty with incomplete data on calving difficulty and/or birth weight using a bivariate threshold-linear animal model.

The purpose of this study was to evaluate the potential loss of accuracy in direct and maternal predicted breeding values (PBV) for calving difficulty (CD) with different levels of missing records of CD and/or birth weight (BW), using a bivariate threshold-linear animal model. Data obtained from the American Gelbvieh Association included 84,420 first-parity records with both CD and BW available. The final pedigree file included 178,858 animals. The model included fixed calf-sex-dam-age, random herd-year-season, and animal direct and maternal effects. Different levels of missing observations for CD and BW were obtained by randomly deleting 0, 25, 50, 75, and 100% of records for both traits in various combinations. Correlation estimates between PBV for CD obtained with complete and incomplete data were used to measure the changes in PBV for different levels of missing records. Reported correlations are means of three replicates. The results suggest that the information on direct and maternal PBV provided by CD records is more reliable than the information provided by BW records. The difference was especially large when a high proportion of CD records were missing. Correlations above 0.96 and 0.95 for direct and maternal PBV, respectively, when missing 25% or 0% of the CD or BW records suggest that small changes would be predicted with a low proportion incomplete data. For genetic prediction of popular sires (with > 100 pogeny), a higher proportion of missing records could be tolerated. The results suggest that the bivariate threshold-linear animal model is useful for routine genetic evaluation of CD with incomplete field data.

Journal Article↗

PubMed2003

[Genetic and epidemiological investigation of a birth cohort of boxers].

The aim of this project, which ran from 1 January 1994 to 1 January 1999 (and which will be continued up to 2004), was to study mortality, disease incidence, and risk factors in a birth cohort of purebred boxer dogs born between January 1994 and February 1995 in the Netherlands (n = 2629). The ancestry of the boxer dogs in the cohort was considered a major risk factor. Special attention was given to genetic disorders, because a system for genetic counselling was being planned; however, non-genetic risk factors were also studied. Participation by breeders and owners of boxer dogs was very high. Pup mortality was 22% and was mainly caused by individual pup factors. Between 2 months and 4 years of age, 123 (7.5%) dogs died; the survival rate was 92.5%. The main causes of death were epilepsy (n = 23), heart disease (n = 22), and traffic injury (n = 13). Over the same age range, on average a boxer dog suffered about 4.25 times from a non-serious disease, mainly of the gastro-intestinal tract, upper respiratory tract, or locomotion system, but 20% had a serious, chronic disease. A relatively high heritability estimate (h2) was found for four diseases: cheilo-palatoschisis (h2 = 0.27), cryptorchism (h2 = 0.24), lesions of cruciate ligaments and menisci (h2 = 0.28), epilepsy (h2 = 0.36). Selection by means of genetic counselling, according to a programme developed on the basis of the results of this study, can reduce the frequency of these genetic diseases in purebred populations of boxer dogs. This genetic counselling programme will also be effective in other breeds of dog because it is based on linking specific pedigree and health information with a generally applicable method of estimating breeding values.

Animals↗

PubMed2004

Climatic and temporal effects on the expression of secondary sexual characters: genetic and environmental components.

Despite great interest in sexual selection, relatively little is known in detail about the genetic and environmental determinants of secondary sexual characters in natural populations. Such information is important for determining the way in which populations may respond to sexual selection. We report analyses of genetic and large-scale environmental components of phenotypic variation of two secondary sexual plumage characters (forehead and wing patch size) in the collared flycatcher Ficedula albicollis over a 22-year period. We found significant heritability for both characters but little genetic covariance between the two. We found a positive association between forehead patch size and a large-scale climatic index, the North Atlantic Oscillation (NAO) index, but not for wing patch. This pattern was observed in both cross-sectional and longitudinal data suggesting that the population response to NAO index can be explained as the result of phenotypic plasticity. Heritability of forehead patch size for old males, calculated under favorable conditions (NAO index > or = median), was greater than that under unfavorable conditions (NAO index < median). These changes occurred because there were opposing changes in additive genetic variance (VA) and residual variance (VR) under favorable and unfavorable conditions, with VA increasing and VR decreasing in good environments. However, no such effect was detected for young birds, or for wing patch size in either age class. In addition to these environmental effects on both phenotypic and genetic variances, we found evidence for a significant decrease of forehead patch size over time in older birds. This change appears to be caused by a change in the sign of viability selection on forehead patch size, which is associated with a decline in the breeding value of multiple breeders. Our data thus reveal complex patterns of environmental influence on the expression of secondary sexual characters, which may have important implications for understanding selection and evolution of these characters.

Age Factors↗