COMPARISON OF TWO MATHEMATICAL MODELS IN FITTING LACTATION CURVES FOR PURELINE AND CROSSLINE DAIRY COWS

1986 ◽  
Vol 66 (2) ◽  
pp. 405-414 ◽  
Author(s):  
T. R. BATRA
Keyword(s):  
Genetic Variation ◽  
Dairy Cows ◽  
Genetic Improvement ◽  
Polynomial Function ◽  
Genetic Effects ◽  
Polynomial Functions ◽  
Lactation Curve ◽  
Open Line ◽  
Days Open ◽  
Effect Of Age

Weekly milk yield of 2066 first, 1407 second, and 755 third lactation pureline and crossline cows was used to study environmental and genetic effects on the coefficients of the lactation curves derived by modified gamma and inverse polynomial functions. The inverse polynomial function provided a better fit than the modified gamma function based on comparison of R2 values. Coefficients of the two models were analyzed to evaluate environmental and genetic effects on the shape of the lactation curve. The model included station, year of calving, month of calving, age at calving, days open, line of sire, line of dam, interaction of line of sire with line of dam, and sires within line of sire. In addition, coefficients of the lactation curve were analyzed by another model which included station, year of calving, month of calving, age at calving, days open, breed additive, maternal, and heterosis effects. Effects of station, year of calving, month of calving, and days open were mostly significant (P < 0.05); however the effect of age at calving was not significant on the coefficients of the lactation curves. Significant (P < 0.05) line of sire and line of dam effects on the level of initial yield suggest that genetic improvement of this trait could be achieved through selection. Breed additive and maternal effects were mostly nonsignificant on the coefficients of the lactation curves indicating shape of the lactation curve could not be changed by selection. There was very little evidence of nonadditive genetic variation associated with the coefficients of lactation curves. Key words: Lactation curves, pureline, crossline, dairy cows

scholarly journals The expression of additive and nonadditive genetic variation under stress.

Genetics ◽  
1995 ◽  
Vol 140 (3) ◽  
pp. 1149-1159
Author(s):  
M W Blows ◽  
M B Sokolowski
Keyword(s):  
Genetic Variation ◽  
Development Time ◽  
Genetic Effects ◽  
Hybrid Breakdown ◽  
Bristle Number ◽  
Gene Complexes ◽  
General Expectation ◽  
Faster Development ◽  
Seven Generations ◽  
Additive Genetic Effects

Abstract Experimental lines of Drosophila melanogaster derived from a natural population, which had been isolated in the laboratory for approximately 70 generations, were crossed to determine if the expression of additive, dominance and epistatic genetic variation in development time and viability was associated with the environment. No association was found between the level of additive genetic effects and environmental value for either trait, but nonadditive genetic effects increased at both extremes of the environmental range for development time. The expression of high levels of dominance and epistatic genetic variation at environmental extremes may be a general expectation for some traits. The disruption of the epistatic gene complexes in the parental lines resulted in hybrid breakdown toward faster development and there was some indication of hybrid breakdown toward higher viability. A combination of genetic drift and natural selection had therefore resulted in different epistatic gene complexes being selected after approximately 70 generations from a common genetic base. After crossing, the hybrid populations were observed for 10 generations. Epistasis contributed on average 12 hr in development time. Fluctuating asymmetry in sternopleural bristle number also evolved in the hybrid populations, decreasing by &gt; 18% in the first seven generations after hybridization.

Estimating the heritability of butterfat production

1961 ◽  
Vol 57 (3) ◽  
pp. 289-294 ◽  
Author(s):  
S. R. Searle
Keyword(s):  
Genetic Variation ◽  
New Zealand ◽  
Dairy Cows ◽  
Total Variance ◽  
Additive Effects ◽  
Narrow Sense ◽  
Sampling Errors ◽  
Gene Effects ◽  
Additive Gene Effects ◽  
Additive Gene

Part of the variation among butterfat yields in dairy cows arises from genetic differences among the animals. The proportion which this bears to the total variance is known as heritability. In the ‘narrow’ sense it is defined (Lush, 1940), as the proportion of the total variance that is due to additive gene effects; the ‘broad’ sense definition includes genetic variation arising from non-additive gene effects as well as that due to additive effects. Since related animals have a proportion of their genes in common the covariance among their production records can be used for estimating genetic variation and hence heritability. This paper discusses three groups of related animals most frequently used for this purpose, twins, daughter-dam pairs and paternal half-sibs, and presents the results of analysing production records of artificially bred heifers in New Zealand, including evidence of the magnitude of the sampling errors of the heritability estimates.

scholarly journals On designing the average lactation curve at the ascending phase

1962 ◽  
Vol 34 (1) ◽  
pp. 162-168
Author(s):  
Aarne Mäkelä
Keyword(s):  
Dairy Cows ◽  
Milk Yield ◽  
Lactation Period ◽  
Lactation Curve ◽  
The Mean ◽  
The Individual ◽  
Daily Milk Yield ◽  
Daily Milk

Comparisons are made between different methods to find the peak production (maximum daily milk yield) and methods to design the average lactation curve at the ascending phase in dairy cows. It was noted that in order to determine the height and location of the maximal producing capacity of a cow in a known lactation period, it is preferable to choose the peak production as a mean of three subsequent best days. It was also noted that the usual methods for drawing the average lactation curves do not give a true picture of the height and location of the peak. The author suggests a method for determining the average lactation curve at the ascending phase by using the averages of both milk productions and times involved in reaching the peak and known fractions (e.g. 1/8, 1/4, 1/2, 3/4, and 5/4) of it. In this lactation curve the peak production is the mean of the peaks of individual cows, and the time involved in reaching it is the mean of the durations of the ascending phases of the individual cows.

scholarly journals Evaluating indirect genetic effects of siblings using singletons

2021 ◽  
Author(s):  
Laurence Howe ◽  
David Evans ◽  
Gibran Hemani ◽  
George Davey Smith ◽  
Neil Martin Davies
Keyword(s):  
Genetic Variation ◽  
Educational Attainment ◽  
Family Environment ◽  
Phenotypic Variation ◽  
Molecular Genetic ◽  
Genetic Effects ◽  
Polygenic Risk Score ◽  
Indirect Genetic Effects ◽  
Molecular Genetic Evidence ◽  
Older Siblings

Estimating effects of parental and sibling genotypes (indirect genetic effects) can provide insight into how the family environment influences phenotypic variation. There is growing molecular genetic evidence for effects of parental phenotypes on their offspring (e.g. parental educational attainment), but the extent to which siblings affect each other is currently unclear.Here we used data from samples of unrelated individuals, without (singletons) and with biological full-siblings (non-singletons), to investigate and estimate sibling effects. Indirect genetic effects of siblings increase (or decrease) the covariance between genetic variation and a phenotype. It follows that differences in genetic association estimates between singletons and non-singletons could indicate indirect genetic effects of siblings.We used UK Biobank data to estimate polygenic risk score (PRS) associations for height, BMI and educational attainment in singletons (N = 50,143) and non-singletons (N = 328,549). The educational attainment PRS association estimate was 12% larger (95% C.I. 3%, 21%) in the non-singleton sample than in the singleton sample, but the height and BMI PRS associations were consistent. Birth order data suggested that the difference in educational attainment PRS associations was driven by individuals with older siblings rather than firstborns. The relationship between number of siblings and educational attainment PRS associations was non-linear; PRS associations were 24% smaller in individuals with 6 or more siblings compared to the rest of the sample (95% C.I. 11%, 38%). We estimate that a 1 SD increase in sibling educational attainment PRS corresponds to a 0.025 year increase in the index individual’s years in schooling (95% C.I. 0.013, 0.036).Our results suggest that older siblings influence the educational attainment of younger siblings, adding to the growing evidence that effects of the environment on phenotypic variation partially reflect social effects of germline genetic variation in relatives.

scholarly journals Association between days open and milk spectral data in dairy cows

2021 ◽  
Author(s):  
H. Toledo-Alvarado ◽  
M.A. Pérez-Cabal ◽  
R.J. Tempelman ◽  
A. Cecchinato ◽  
G. Bittante ◽  
...  
Keyword(s):  
Dairy Cows ◽  
Spectral Data ◽  
Days Open

scholarly journals The Analysis of Reproduction in Population of the Slovak Spotted Dairy Cows

2019 ◽  
Vol 67 (6) ◽  
pp. 1419-1426
Author(s):  
Jozef Bujko ◽  
Juraj Candrák ◽  
Peter Strapák ◽  
Július Žitný ◽  
Cyril Hrnčár ◽  
...  
Keyword(s):  
Dairy Cows ◽  
Fixed Effects ◽  
Linear Models ◽  
Correlation Coefficients ◽  
Calving Interval ◽  
Factors Affecting ◽  
Actual Computation ◽  
Reproduction Traits ◽  
Days Open ◽  
Basic Statistical Analysis

The aim of study was to analyse the reproduction and factors affecting on reproduction traits of dairy cows in population of Slovak Spotted cattle from 2007 to 2016 the results for 37,274 dairy cows: days to first service (DFS), days open (DO), number of inseminations per conception (NIC), age of first calving (AFC) and calving interval (CI). The basic statistical analysis were analysed using the SAS version 9.3. For the actual computation a linear models with fixed effects was used: For the actual computation a linear models with fixed effects was used: yijklm = μ + HYSi + BTj+ Fk+ Bl +eijklm. The linear model represents coefficients determination R2 = 0.452117% (P < 0.001) for DFS, R2 = 0.377715% (P < 0.001) for DO, R2 = 0.348442% (P < 0.001) for NIC and R2 = 0.317128% (P < 0.001) for CI with all fixed effects. Correlation coefficients among DFS with DO, NIC, AFC and CI were r = 0.37275, r = -0.06881, r = 0.06493 and r = 0.08348. These coefficients were highly statistically significant (P < 0.001).

scholarly journals Genetic variation in the feeding value of alfalfa genotypes evaluated from experiments with dairy cows

Agronomie ◽  
1997 ◽  
Vol 17 (2) ◽  
pp. 119-125 ◽  
Author(s):  
J. C. Émile ◽  
M. Mauries ◽  
G. Allard ◽  
P. Guy
Keyword(s):  
Genetic Variation ◽  
Dairy Cows ◽  
Feeding Value

scholarly journals Artificial selection and maintenance of genetic variance in the global dairy cow population

2005 ◽  
Vol 360 (1459) ◽  
pp. 1479-1488 ◽  
Author(s):  
S Brotherstone ◽  
M Goddard
Keyword(s):  
Genetic Variation ◽  
Genetic Improvement ◽  
Breeding Value ◽  
Payment Systems ◽  
Frozen Semen ◽  
Best Linear Unbiased ◽  
The Uk ◽  
Selection Algorithms ◽  
Global Population

Genetic improvement of dairy cows, which has increased the milk yield of cows in the UK by 1200 kg per lactation in 12 years, is an excellent example of the application of quantitative genetics to agriculture. The most important traits of dairy cattle are expressed only in females, but the main opportunity for selection is in males. Despite this, genetic improvement was achieved by the invention of a new statistical methodology, called ‘best linear unbiased prediction’ to estimate the breeding value of bulls. Intense selection of the best bulls, combined with the worldwide use of these bulls through artificial insemination and frozen semen, has created a global population and caused concern that the genetic variation available in the future will be reduced. Maintenance of genetic variation and long-term genetic gains would be aided by rational payment systems, use of crossbreeding where profitable, inclusion of all economically important traits in the breeding objective, recognition of genotype by environment interactions and the use of selection algorithms that balance estimated breeding value against the average relationship among the selected animals. Fortunately, all of these things are happening to some degree.

Effect of age and stage of lactation on whey protein content in milk of cows of different breeds

2013 ◽  
Vol 16 (2) ◽  
pp. 395-397 ◽  
Author(s):  
J. Król ◽  
A. Brodziak ◽  
Z. Litwińczuk ◽  
A. Litwińczuk
Keyword(s):  
Dairy Cows ◽  
Protein Content ◽  
Whey Protein ◽  
Stage Of Lactation ◽  
Effect Of Age

Abstract The aim of the study was to determine the effect of age of cows, i.e. subsequent lactation and stage of lactation, on bioactive whey protein content in milk of dairy cows of six primary breeds kept in Poland. In all cases the significant correlations between lactoferrin concentration in milk and stage of lactation was stated. Its content gradually increased with the course of lactation but the changes in the content of this protein were highly dependent on breed of cows, what was indicated also by high interactions between breed and stage of lactation.

Effect of first 60-day cumulative milk yield on days open in Holstein dairy cows in Iran

2007 ◽  
Vol 2007 ◽  
pp. 148-148
Author(s):  
A. Heravi Moussavi ◽  
M. Danesh Mesgaran ◽  
T. Vafa
Keyword(s):  
Dairy Cattle ◽  
Dairy Cows ◽  
Milk Production ◽  
Milk Yield ◽  
Dairy Farm ◽  
Reproductive Efficiency ◽  
Root Cause ◽  
Principal Factors ◽  
Days Open ◽  
Holstein Dairy Cows

Reproduction and milk production are the principal factors that are influencing dairy farm profitability. The dairy industry in Iran has changed dramatically in the last decade. The shift toward more productive cows and larger herds in Iran is associated with a decrease reproductive efficiency (Heravi Moussavi et al., 2004). Increased knowledge about the principal causes of reduced fertility is essential. The root cause of the declining fertility is probably a combination of a variety of physiological and management factors that have an additive effect on reproductive efficiency. Dairy cattle are inseminated and pregnancy is established while dairy cows are lactating. Based on the analyses of large datasets, there is clearly an antagonistic relationship between milk production and reproduction in dairy cattle (Lucy, 2001). It was shown that the hazard ratio for cumulative first 60-day milk yield and conception in high producer cows was 8 percent less than the others and also high milk yield was a risk factor for several reproductive disorders (Grohn and Rajala-Schultz, 2000). The objective of this study was to evaluate the effect of first 60-day cumulative milk yield on days open in Iranian Holstein dairy cows.

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