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L G Christensen

Publications and source records attributed to L G Christensen.

14 recordsLinked to original sources
PubMed2006

A method to define breeding goals for sustainable dairy cattle production.

The objective of this study was to present a method to define breeding goals for sustainable dairy cattle production by adding nonmarket values to market economic values for functional traits in the breeding goal. A nonmarket value can represent the value of improved animal welfare or societal influences for animal production. The nonmarket value for mastitis resistance, conception rate, and stillbirth were derived based on how much farmers or breeding companies were willing to lose in selection response for milk yield to improve functional traits. The desired response for milk yield corresponding to a given percent loss was obtained using desired gain indices. By allowing a 5% loss in the selection response for milk yield, the nonmarket value was found to be 40.4 euro for mastitis resistance, 16.1 euro for conception rate, and 9.7 euro for stillbirth. The nonmarket value increased proportionally with increasing loss in the selection response for milk yield, but the selection response was lower for conception rate than for mastitis resistance because of differences in market economic value and heritability. To increase the response for conception rate, the nonmarket value was also derived for 2 situations, in which the desired responses for milk yield, mastitis resistance, and conception rate were specified. The method can be used to define breeding goals for sustainable production and to increase the response for traits that are at critically low levels. When defining breeding goals for sustainable production, breeding organizations should predict the selection response based on market economic value and add non-market value for traits with unacceptable selection responses.

Animals↗
PubMed2005

Derivation of sustainable breeding goals for dairy cattle using selection index theory.

The objective was to present 2 methods for the derivation of nonmarket values for functional traits in dairy cattle using deterministic simulation and selection index theory. A nonmarket value can be a value representing animal welfare and societal influences for animal production, which can be added to market economic values in the breeding goal to define sustainable breeding goals. The first method was restricted indices. A consequence of adding a nonmarket value to a market economic value for a given functional trait is less selection emphasis on milk yield. In the second method, the loss in selection response in milk resulting from greater emphasis on functional traits was quantified. The 2 methods were demonstrated using a breeding goal for dairy cattle with 4 traits (milk yield, mastitis resistance, conception rate, and stillbirth). Nonmarket values derived separately using restricted indices were 0.4 and 2.6 times the value of market economic values for mastitis resistance and conception rate, respectively. Nonmarket values for mastitis resistance and conception rate were both lower when derived simultaneously than when derived separately. This was due to the positive genetic correlation between mastitis resistance and conception rate, and because both traits are negatively correlated with milk yield. Using the second method and accepting a 5% loss in selection response for milk yield, nonmarket values for mastitis, conception rate, and stillbirth were 0.3, 1.4, and 2.9 times the market economic values. It was concluded that the 2 methods could be used to derive nonmarket values for functional traits in dairy cattle.

Animals↗
PubMed2004

Genetic parameters for stillbirth in Danish Holstein cows using a Bayesian threshold model.

The objective of this study was to make an inference about the direct and maternal genetic variation of stillbirth for first-calving Holstein cows and to estimate the effect of breed and heterosis for original Danish black and white and Holstein-Friesian. A Bayesian threshold model, which included correlated genetic effects of sires and maternal grandsires was used. Marginal posterior distributions of effects were obtained using Gibbs sampling. Point estimates were compared with results from a linear model using REML. Data with and without twins were analyzed and models with and without effects of breed and heterosis were fitted, but estimates of genetic parameters were almost identical. In all the analyses with threshold models, the marginal posterior mean (and standard deviation) was 0.10 (0.014) for the direct heritability, 0.13 (0.015) for the maternal heritability, and 0.05 (0.10) for the genetic correlation between direct and maternal effects. The stillbirth rate tended to increase with a higher proportion of Holstein-Friesian in the calf and in the dam, but no effects of breed and heterosis were significant. Joint sampling of all location parameters was found superior to univariate sampling in terms of much better mixing properties of the fixed effects. Based on the results showing genetic variation for stillbirth at first calving, both the direct and the maternal effect could be included in the breeding program.

Animals↗
PubMed2004

Undesired phenotypic and genetic trend for stillbirth in Danish Holsteins.

The primary aim of this study was to evaluate the phenotypic and genetic trends for stillbirth in Danish Holsteins. Trends of calving difficulty and calf size were also evaluated. The second aim was to compare predicted transmitting abilities (PTA) of sires for stillbirth using a linear and a threshold model. Direct and maternal genetic effects were modeled by fitting correlated additive genetic effects of the sire and the maternal grandsire (MGS). For both the calf and the dam, covariates of breed proportions of Holstein-Friesian (HF) and the heterozygosity between HF and the original Danish Black and White (ODBW) were included. Records from 1.8 million first-calving Danish Holstein cows calving from 1985 to 2002 were used. In this period, the overall frequency of stillbirth increased from 0.071 to 0.090. An unfavorable genetic trend of stillbirth was found for both the direct and maternal effect. The background for the genetic trends was an intense use of HF sires as sires of sons, which increased the proportion of HF genes to 94% in the Danish Holstein calves born in 2002. The effect of the imported HF genes was higher direct effects of calf size, calving difficulty, and stillbirth compared with the ODBW genes. The maternal effect of stillbirth was poorer for HF than for ODBW even though HF had a better maternal calving performance than ODBW. The threshold and the linear models showed almost similar predictions of transmitting abilities of sires.

Animals↗
PubMed2003

Genetic parameters of postnatal mortality in Danish Holstein calves.

The objective of this study was to estimate genetic parameters of postnatal mortality (PM) in dairy cattle. Data originated from 841,921 Danish Holstein calves. Four binary traits of mortality were considered: D1-14, D15-60, D61-180, and D1-180 with numbers indicating the period of risk in days after birth. The unadjusted frequency of D1-14, D15-60, D61-180, and D1-180 were 0.027, 0.018, 0.020, and 0.066, respectively. A linear sire-model was fitted to the data, and average information-REML was used to estimate (co)variance components. Estimates of direct heritabilities for the four mortality traits ranged from 0.001 to 0.008 but were all significant. D61-180 and D1-180 had the highest direct heritabilities. Maternal heritabilities were very low, ranging from 0.0002 to 0.0015 and significant for D1-14 and D1-180 only. The direct genetic correlation between D1-14 and D15-60, between D15-60 and D61-180, and between D1-14 and D61-180 was 0.73, 0.54, and 0.34, respectively. It indicates that different genes are responsible for early PM (D1-14) and late PM (D61-180). When D61-180 was treated as a different trait for females, males not transferred, and transferred males, the direct heritability was 0.004, 0.008, and 0.034, respectively, but the direct genetic correlations between these three traits were very high. If transfers of calves are getting more common, the importance of including PM in a breeding program will increase, as the genetic variation of PM was considerably higher for transferred calves than for calves that were not transferred.

Aging↗
PubMed2003

Bayesian estimates of covariance components between lactation curve parameters and disease liability in Danish Holstein cows.

In the present work, covariance components for milk yield and disease liability were estimated with bivariate random regression test-day sire models using a Bayesian approach and implemented via the Gibbs sampler. The data consist of 8075 first-parity Danish Holstein (DH) cows, from 1259 sires, performing in 57 herds from 1992 to 1997. Treatments associated with five different type of diseases were pooled into a single general disease liability for each cow. Two models were fitted to the data. First, using a bivariate model, milk yield is modeled via a random regression, and disease liability via a repeatablility model. Second, using a bivariate model, both milk yield and disease liability are modeled using random regressions. A comparison based on a Bayes factor provides very strong support for the bivariate random regression model. Posterior means of heritabilities for each of the traits were estimated for five different points in time throughout lactation. Across models, heritabilities for milk yield are lowest in the beginning of the lactation (0.19) and highest at the end of the lactation (0.35). Posterior means of heritabilities of disease liability range from 0.04 to 0.10 for test days, and is equal to 0.20 for the whole lactation. Heritability of persistency measures estimated from the two models are 0.20 and 0.21. Estimates of posterior means of genetic correlations between single test-day milk yield and single test-day disease liability are in the range of 0.31 to 0.57. The estimates of posterior mean and of the 95% posterior interval of the genetic correlation between persistency and (total) disease liability using the model with the highest posterior probability are -0.12 and (-0.44; 0.20), respectively. Even though the largest proportion of the posterior probability mass is spread along negative values of the correlation (indicating that individuals with a flatter lactation curve tend to have lower disease liability), a value of zero of the genetic correlation falls comfortably within the 95% posterior interval. Thus the prospects of reducing incidence of disease by manipulating persistency as defined in this work remain inconclusive.

Animals↗
PubMed2003

Genetic relationship between body condition score, dairy character, mastitis, and diseases other than mastitis in first-parity Danish Holstein cows.

The aim of this study was to explore the possibilities of using body condition score (BCS) or dairy character (DC) as indicators of mastitis and diseases other than mastitis in first-parity Danish Holsteins. The dataset included 28,948 observations on conformation scores and 365,136 disease observations. The analysis was performed using a multitrait linear sire model. Heritability estimates for BCS and DC were moderate (0.25 and 0.22), and heritability estimates for mastitis and diseases other than mastitis were low (0.038 and 0.022). Between BCS and diseases other than mastitis, the genetic correlation was -0.22, whereas the genetic correlation was -0.16 between BCS and mastitis. The genetic correlation between DC and diseases other than mastitis was 0.43, and between DC and mastitis it was 0.27. The genetic correlation between BCS and DC was -0.61. Residual correlations were close to 0, except between BCS and DC (-0.37). Including DC as an indicator of diseases other than mastitis will increase the accuracy of the predicted breeding value for diseases, especially when the progeny group is small. Using BCS as an additional indicator of diseases did not increase the accuracy. Breeding for less DC will increase resistance to diseases.

Animals↗
PubMed2003

Genetic analysis of body condition score in first-parity Danish Holstein cows.

The aim of this study was to test whether genetic components for body condition score (BCS) changed during lactation in first-parity Danish Holsteins. Data were extracted from the national conformation scoring system and consisted of 28,948 records from 3894 herds. Cows were scored once during lactation for BCS on a scale from 1 to 9 with increments of 1. The majority of records were made from d 30 to 150 of lactation. Mean BCS was 4.28 +/- 0.98. Body condition score was lowest in wk 8 to 10 from calving. A multivariate sire model with BCS recordings in six lactation stages treated as different traits was used to analyze the data. In addition, a random regression sire model was used to evaluate the changes in BCS as continuous functions of lactation stage. Estimates of heritability from the multivariate approach ranged from 0.14 to 0.29, and the estimated genetic correlations between BCS at different lactation stages were all higher than 0.82. The random regression model was based on Legendre polynomials (LP) specified on days in milk at scoring. To evaluate the change in mean BCS during lactation, the fixed part of the model included a fifth-order LP on the effect of days in milk at scoring. The highest order of fit used for the sire effect was a third-order LP, but based on likelihood ratio tests this could be reduced to a 0 order, i.e., a model with only the intercept term for the sire effect. This means that the genetic variation is constant over the investigated part of the lactation. Therefore, BCS can be considered the same trait during lactation, and a simple sire model can be used for prediction of breeding values.

Adipose Tissue↗
PubMed2002

Genetic parameters of dairy character, protein yield, clinical mastitis, and other diseases in the Danish Holstein cattle.

The primary aim of this study was to estimate genetic correlations between dairy character, protein yield, clinical mastitis, and other diseases. Data consisted of first lactation records of Danish Holstein cows calving from 1990 to 1999. After editing, the data included records on 934,639 cows, of which 101,853 were assessed for dairy character, 472,421 for diseases, and 834,993 for protein yield. The disease traits were defined as binary traits in the period from 10 d before to 50 d after calving for clinical mastitis, and from 10 d before to 100 d after calving for diseases other than mastitis. Data were analyzed with a linear sire model using the method of AI-REML. Heritabilities were estimated to be 0.265 for protein yield, 0.261 for dairy character, 0.035 for clinical mastitis, and 0.020 for diseases other than mastitis. Estimates of genetic correlations between protein yield and dairy character, protein yield and clinical mastitis, and protein yield and diseases other than mastitis were 0.38, 0.33, and 0.14. Between the two disease traits, the genetic correlation was 0.24. The genetic correlation between dairy character and clinical mastitis was 0.24. Between dairy character and diseases other than mastitis the genetic correlation was 0.41. Thus, cows with high score for dairy character were more prone to diseases. The genetic correlation between dairy character and the disease traits, when both traits were adjusted for protein yield, was 0.13 for clinical mastitis and 0.39 for diseases other than mastitis. These findings suggest that, dairy character should be given a negative rather than a positive weight in the breeding goal.

Animals↗
PubMed2002

Genetic parameters for milk production and persistency for Danish Holsteins estimated in random regression models using REML.

(Co)variance components for milk, fat, and protein yield of 8075 first-parity Danish Holsteins (DH) were estimated in random regression models by REML. For all analyses, the fixed part of the model was held constant, whereas four different functions were applied to model the additive genetic effect and the permanent environment effect. Homogeneous residual variance was assumed throughout lactation. Univariate models were compared using a minimum of -2 ln(restricted likelihood) as the criterion for best fit. Heritabilities as a function of time were calculated from the estimated curve parameters from univariate analyses. Independent of the function applied and the trait in question, heritabilities were lowest in the beginning of the lactation. Heritabilities for persistency of fat yield were slightly higher than heritabilities for persistency of milk and protein yield. Genetic correlations between persistency and 305-d production were higher for protein and milk yield than for fat yield. Bivariate analyses between the production traits were carried out in sire models using the models with the best 3-parameter curve fit in the univariate analyses. Correlations between traits were calculated from covariance components for curve parameters estimated in bivariate analyses. Genetic correlations between milk and protein yield were higher than between milk and fat yield.

Algorithms↗
PubMed1999

Staying good while playing god--the ethics of breeding farm animals.

Modern genetics has given us some very efficient tools with which to alter the characteristics of animals. To date, farm animal breeders have mainly used these tools to increase productivity. Thus, each new generation of farm animals matures faster, yields more milk, or produces more meat or eggs, than the previous one. Despite these apparent benefits, modern farm animal breeding has had severe negative consequences, including effects on the quality of the animals' lives and biodiversity. The aim of this paper is to discuss the goals and consequences of farm animal breeding within an ethical context. First, a description of what has happened to broilers and dairy cattle as breeders have pursued the goal of ever more efficient production is given. Second, the ethical values that ought to underlie future breeding schemes are discussed. It is suggested that there are in fact two very different ethical approaches: the 'quality of life-based' approach and the 'preservationist' approach. A view combining elements from both approaches is advanced. Finally, an example is given of how it is possible, in practice, to pursue an ethically defensible breeding goal without compromising production efficiency.

Animal Welfare↗
PubMed1977

Respiratory diseases in calves. An economic analysis.

From a Danish dairy herd comprising 350 milking cows data were obtained on all (1010) single, liveborn calves dropped over a three year period. Deaths incurred before, during, and immediately after delivery were not included in the study. The mortality rate up to the first few hours after birth was 10% leaving 910 calves to be included in the present study. The overall respiratory disease (r.d.) attack rate among calves from birth up to the end of the sixth month was 23%; the r.d. case fatality rate was 40%; the r.d. mortality rate was 9%. The mortality rate due to ailments other than r.d. was 11%, and the overall mortality rate during the first six months of life was 20%. The economic impact of r.d. in the herd was evaluated using a disease model which, in mathemathical terms, conceptualizes the basic patterns of the disorders within the calf population. The economic implications of various changes in the prevailing herd health status with respect to r.d. are outlined and discussed (Table VII, IX, XI). Also the economic expectations under different sales policies were studied (Table VIII and X). The study clearly demonstrates the versality of health models and how these may be applied to prepare economic forecasts during periods with rapidly changing market and production conditions.

Animals↗