In all animal breeding, and dairy cattle are no exception, no new genetic material is created. Rather, it is simply a matter of sorting or rearranging the many factors already present in the male and female gametes. These factors are referred to as genes. They are contained in the chromosomes of the sperm of the male and the egg of the female.
Dairy animals have 30 pairs of chromosomes in each cell. The number of genes per chromosomes is not definitely known; estimates are that there may be as many as 30.000 genes for dairy cattle. These genes are responsible for how the animal looks and produces.
When the sperm and egg unite, the new cell formed contains 30 pairs of chromosomes, or a total of 60 chromosomes, half of which come from the sperm (male) and half from the egg (female). What determines which genes and which chromosomes are to be passed on to the new cell is still a relatively dark secret.
If our self view side of genetic parameters is an animal constructions is an abstraction. Hence, these as a matter of facts, it’s a true and so be clearly visible cause we look at that based of view side an animal skeleton and genetic regeneration. The parents as subject to offering something as contributions of improvement has offspring. Well to know and in according to researchers both parents can given portion should be about 50% respected from there. But, a few researchers said, it’s the truth of the genetic constructions not always 50% respected, sometime we found should be 75% and 25% respected. May be depending on RNA and DNA chains that there are at the both parents. It’s not always the truth a new discuss but it’s really for every an animal parents.
For many years, genetic improvement of the U.S. dairy cattle was focused on identifying and selecting an animal superior (cow's), with little attention given to the evaluation of bulls. As improved methods were developed, dairy producers who used them gained some advantage in rate of genetic improvement over their competitors. In order, the following methods of genetic evaluation were used in the past: (1) lactation record, (2) daughter average, (3) daughter-dam comparison, (4) herdmate comparison, and (5) contemporary comparison. Each of these is briefed in the sections that follow.
The United States dairy industry and consumers have benefited greatly from the national research program on genetic improvement of dairy cattle conducted by the Animal Improvement Programs Laboratory (AIPL), Agricultural Research at the land-grant universities. Genetic evaluation of bulls (Sire Summaries) and cow (Cow indexes) emanating from this research have been the primary source of information for identifying animals with superior genetic merit for yield. We're can look out and comparison, what can do it to repaired and to developed genetic science by researchers from an Indonesia? May be their has good concepts and good procedural to improvement by Artificial Insemination and the first of the way that is selection offspring from superior parents (male or female). They're choosing of Artificial Insemination, as a means of dairy cattle improvement, is now accepted and utilized worldwide. The increased use of outstanding sires to enhance production potential, control certain genital diseases transmitted through natural service, and encourage general mass improvement is well recognized.
The people highly need for information and knowledge especially such as the recently not relevant on new conceptualities and research results. It’s to talk of convenience on especially knowledge conceptualization that’s become fail, very difficult, that is not connected and than we founding only mis-appreciate the facts. The people asked that what meant of the genetic conceptualization? This is a main conceptual that papers theory and the results of the data analysis. That’s true, we must been the conceptual about genetic parameters. But know, the genetic parameter that we know and simple definition “the knowledge is associated by pedigree theoretical”, that is true. More than it is of definition exactly for know that is not easy. Why I say, about these?
Although the majority of selection emphasis in dairy breeding is placed on production, many non-production traits are important in maximizing longevity and reducing losses due to mortality and illness. Unfortunately, many non-production traits are influenced more by environment and less by genetic ability thereby reducing heritabilities of these traits. As well, there is often a maternal genetic effect that complicates evaluation and selection on these traits. Furthermore, genetic variability of health and reproductive traits may contain more non-additive (non-transmittable) genetic components, which further reduce effectiveness of traditional selection for these traits. Regardless, traits such as stillbirths and dystocia do constitute financial losses to the dairy farmer and should be considered in breeding and management programs.
The normal range of heritabilities for stillbirths and associated traits were given by Philipsson et al. (1979). As shown, heritability of stillbirths is very low, particularly for cows (.00 to .02), and therefore, direct selection against stillbirths would be relatively ineffective. Fortunately, genetic correlations with other traits do exist. A particularly strong correlation (0.6 to 0.8) exists between stillbirths and dystocia and a moderate correlation (0.4) exists between stillbirths and birthweight. These associated traits do present other alternatives to selecting directly against stillbirths. For example, selection for calving ease (selecting against dystocia) instead of rate of stillbirths, provides many advantages. Heritability of direct and maternal calving ease is 0.11 and 0.12, respectively (Dwyer, 1984), which is several times higher than heritability for stillbirth rate. Since rate of stillbirths and calving ease are highly correlated, it is more efficient to select indirectly for rate of stillbirths by selecting for calving ease. According to Meijering (1985):
"... it is questionable whether sire evaluation for stillbirths is worth the effort at all in the present situation, considering the extremely small sire variance. For, even if habitability was three times as high as presently estimated, indirect selection through dystocia would be as efficient as direct selection for stillbirth given the present effective progeny group sizes and genetic correlations."
In addition to more effective protection against stillbirths, selection for calving ease also reduces the associated costs of assisted calving, longer days open, and reduced milk production of the dam.
Several non-genetic factors have been examined for their impact on stillbirth rate and calving performance, the most important being the dam's parity, sex of calf, nutritional status of dam, and season of calving. Heifers have been found to have stillbirth rates 2 to 4 time higher than cows (Van Dieten, 1963; Grommers et al., 1965; Laster and Gregory, 1973). Sex of calf is thought to have a significant effect on calving ease, but has little effect on stillbirths (Cloppenburg, 1966; Philipsson, 1976; Hassig and Scholte, 1979). Also, heifers or cows with improper nutritional regimes may experience reduced calving performance and consequently higher stillbirth rates (Arnett et al., 1971; Lowman, 1979). Slightly higher rates of stillbirths have been reported in the summer months (Lindstrom and Vilva (1977), presumably due to lower surveillance rate when animals are in pasture.
In light of the very low heritability of stillbirths and the significant effect of many non-genetic and environmental factors, raw mean stillbirth rates associated with individual sires could be extremely misleading. In most cases, the reasons some sires will appear to have more stillbirths are due to non-genetic factors or by chance. When progeny groups sizes become large (500 daughters) the probability that high numbers of stillbirths are caused by chance are reduced. Simple Chi-squared tests could be used to illustrate the effect of small sample sizes on significance of average number of stillbirths. However, systematic non- genetic factors including parity, season of calving, or breed interactions cannot be ruled out. The proper procedure to evaluate sire differences for stillbirth rate involves careful BLUP sire evaluation techniques, but with a low heritability, as in this case, very large progeny group sizes would be needed to determine any differences between sires. Unfortunately, large progeny group sizes reduce the number of bulls that can be tested and, therefore, reduces the rate of genetic progress for production traits. Furthermore, standard BLUP evaluations assume multivariate normality of data (Henderson, 1973), and with categorical variates such as dystocia and stillbirth, this assumption is not met, there by reducing the probability that animals are correctly ranked (Gianola, 1980; Portnoy, 1982).
Because there is a positive correlation of 0.4 between calf size and stillbirth, the possibility exists that if the female being bred is smaller than average or the calf size is larger than average, the rate of stillbirths could increase. This could be the situation if the dam is a heifer as mentioned above. This could also occur if a significant difference for size exists between breeds. In many populations around the world, North-American Holsteins have been used on smaller varieties of the Friesian breed or other breeds. Because of the size difference between breeds and the effect of heterosis on calf size, initial crosses between breeds should be made carefully. For example, only cows or larger heifers should be considered during the first few generations of introducing the larger Holstein strain. Also, North-American sires are routinely evaluated for calving ease making selection against dystocia possible. Nutrition programs emphasizing rapid growth of heifers may also reduce stillbirths due to calving difficulties. Size has increased in the Canadian Holstein breed over the last 15 years, but better nutrition program for heifers were also emphasized during the same period. As a result, the stillbirth rate for heifers has fluctuated but remained on average below 7%. The stillbirth rate for cows has remained much more constant with an average of 2.9%.
Dairy animals have 30 pairs of chromosomes in each cell. The number of genes per chromosomes is not definitely known; estimates are that there may be as many as 30.000 genes for dairy cattle. These genes are responsible for how the animal looks and produces.
When the sperm and egg unite, the new cell formed contains 30 pairs of chromosomes, or a total of 60 chromosomes, half of which come from the sperm (male) and half from the egg (female). What determines which genes and which chromosomes are to be passed on to the new cell is still a relatively dark secret.
If our self view side of genetic parameters is an animal constructions is an abstraction. Hence, these as a matter of facts, it’s a true and so be clearly visible cause we look at that based of view side an animal skeleton and genetic regeneration. The parents as subject to offering something as contributions of improvement has offspring. Well to know and in according to researchers both parents can given portion should be about 50% respected from there. But, a few researchers said, it’s the truth of the genetic constructions not always 50% respected, sometime we found should be 75% and 25% respected. May be depending on RNA and DNA chains that there are at the both parents. It’s not always the truth a new discuss but it’s really for every an animal parents.
For many years, genetic improvement of the U.S. dairy cattle was focused on identifying and selecting an animal superior (cow's), with little attention given to the evaluation of bulls. As improved methods were developed, dairy producers who used them gained some advantage in rate of genetic improvement over their competitors. In order, the following methods of genetic evaluation were used in the past: (1) lactation record, (2) daughter average, (3) daughter-dam comparison, (4) herdmate comparison, and (5) contemporary comparison. Each of these is briefed in the sections that follow.
The United States dairy industry and consumers have benefited greatly from the national research program on genetic improvement of dairy cattle conducted by the Animal Improvement Programs Laboratory (AIPL), Agricultural Research at the land-grant universities. Genetic evaluation of bulls (Sire Summaries) and cow (Cow indexes) emanating from this research have been the primary source of information for identifying animals with superior genetic merit for yield. We're can look out and comparison, what can do it to repaired and to developed genetic science by researchers from an Indonesia? May be their has good concepts and good procedural to improvement by Artificial Insemination and the first of the way that is selection offspring from superior parents (male or female). They're choosing of Artificial Insemination, as a means of dairy cattle improvement, is now accepted and utilized worldwide. The increased use of outstanding sires to enhance production potential, control certain genital diseases transmitted through natural service, and encourage general mass improvement is well recognized.
The people highly need for information and knowledge especially such as the recently not relevant on new conceptualities and research results. It’s to talk of convenience on especially knowledge conceptualization that’s become fail, very difficult, that is not connected and than we founding only mis-appreciate the facts. The people asked that what meant of the genetic conceptualization? This is a main conceptual that papers theory and the results of the data analysis. That’s true, we must been the conceptual about genetic parameters. But know, the genetic parameter that we know and simple definition “the knowledge is associated by pedigree theoretical”, that is true. More than it is of definition exactly for know that is not easy. Why I say, about these?
Although the majority of selection emphasis in dairy breeding is placed on production, many non-production traits are important in maximizing longevity and reducing losses due to mortality and illness. Unfortunately, many non-production traits are influenced more by environment and less by genetic ability thereby reducing heritabilities of these traits. As well, there is often a maternal genetic effect that complicates evaluation and selection on these traits. Furthermore, genetic variability of health and reproductive traits may contain more non-additive (non-transmittable) genetic components, which further reduce effectiveness of traditional selection for these traits. Regardless, traits such as stillbirths and dystocia do constitute financial losses to the dairy farmer and should be considered in breeding and management programs.
The normal range of heritabilities for stillbirths and associated traits were given by Philipsson et al. (1979). As shown, heritability of stillbirths is very low, particularly for cows (.00 to .02), and therefore, direct selection against stillbirths would be relatively ineffective. Fortunately, genetic correlations with other traits do exist. A particularly strong correlation (0.6 to 0.8) exists between stillbirths and dystocia and a moderate correlation (0.4) exists between stillbirths and birthweight. These associated traits do present other alternatives to selecting directly against stillbirths. For example, selection for calving ease (selecting against dystocia) instead of rate of stillbirths, provides many advantages. Heritability of direct and maternal calving ease is 0.11 and 0.12, respectively (Dwyer, 1984), which is several times higher than heritability for stillbirth rate. Since rate of stillbirths and calving ease are highly correlated, it is more efficient to select indirectly for rate of stillbirths by selecting for calving ease. According to Meijering (1985):
"... it is questionable whether sire evaluation for stillbirths is worth the effort at all in the present situation, considering the extremely small sire variance. For, even if habitability was three times as high as presently estimated, indirect selection through dystocia would be as efficient as direct selection for stillbirth given the present effective progeny group sizes and genetic correlations."
In addition to more effective protection against stillbirths, selection for calving ease also reduces the associated costs of assisted calving, longer days open, and reduced milk production of the dam.
Several non-genetic factors have been examined for their impact on stillbirth rate and calving performance, the most important being the dam's parity, sex of calf, nutritional status of dam, and season of calving. Heifers have been found to have stillbirth rates 2 to 4 time higher than cows (Van Dieten, 1963; Grommers et al., 1965; Laster and Gregory, 1973). Sex of calf is thought to have a significant effect on calving ease, but has little effect on stillbirths (Cloppenburg, 1966; Philipsson, 1976; Hassig and Scholte, 1979). Also, heifers or cows with improper nutritional regimes may experience reduced calving performance and consequently higher stillbirth rates (Arnett et al., 1971; Lowman, 1979). Slightly higher rates of stillbirths have been reported in the summer months (Lindstrom and Vilva (1977), presumably due to lower surveillance rate when animals are in pasture.
In light of the very low heritability of stillbirths and the significant effect of many non-genetic and environmental factors, raw mean stillbirth rates associated with individual sires could be extremely misleading. In most cases, the reasons some sires will appear to have more stillbirths are due to non-genetic factors or by chance. When progeny groups sizes become large (500 daughters) the probability that high numbers of stillbirths are caused by chance are reduced. Simple Chi-squared tests could be used to illustrate the effect of small sample sizes on significance of average number of stillbirths. However, systematic non- genetic factors including parity, season of calving, or breed interactions cannot be ruled out. The proper procedure to evaluate sire differences for stillbirth rate involves careful BLUP sire evaluation techniques, but with a low heritability, as in this case, very large progeny group sizes would be needed to determine any differences between sires. Unfortunately, large progeny group sizes reduce the number of bulls that can be tested and, therefore, reduces the rate of genetic progress for production traits. Furthermore, standard BLUP evaluations assume multivariate normality of data (Henderson, 1973), and with categorical variates such as dystocia and stillbirth, this assumption is not met, there by reducing the probability that animals are correctly ranked (Gianola, 1980; Portnoy, 1982).
Because there is a positive correlation of 0.4 between calf size and stillbirth, the possibility exists that if the female being bred is smaller than average or the calf size is larger than average, the rate of stillbirths could increase. This could be the situation if the dam is a heifer as mentioned above. This could also occur if a significant difference for size exists between breeds. In many populations around the world, North-American Holsteins have been used on smaller varieties of the Friesian breed or other breeds. Because of the size difference between breeds and the effect of heterosis on calf size, initial crosses between breeds should be made carefully. For example, only cows or larger heifers should be considered during the first few generations of introducing the larger Holstein strain. Also, North-American sires are routinely evaluated for calving ease making selection against dystocia possible. Nutrition programs emphasizing rapid growth of heifers may also reduce stillbirths due to calving difficulties. Size has increased in the Canadian Holstein breed over the last 15 years, but better nutrition program for heifers were also emphasized during the same period. As a result, the stillbirth rate for heifers has fluctuated but remained on average below 7%. The stillbirth rate for cows has remained much more constant with an average of 2.9%.
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