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Summary:Intensive genetic selection has
resulted in modern dairy cow with very high milk yields but reduced fertility,
due mainly to an increase in postpartum clinical problems, poor expression of
oestrus, defective oocytes/embryos and uterine infections. It is a challenge to
get enough food into these cows to meet the high demands of peak milk yields in
early lactation and the animals require considerable veterinary attention in
the early period after calving.The conducted studies show that optimization of
the reproductive ability of cows and the level of their dairy productivity by
increasing the duration of the dry period to 90 days ensures an increase in the
reproductive qualities of animals, and an increase in the period of deadness
prevents postpartum complications and reduces the timing of the involution of
the genital organs compared with the control. The births in these groups of
animals proceeded more quickly and without complications. The blood indicators
of the animals under study reflect a violation of metabolic processes in their
body. Key words: blood, selection,
breed, heifer, uterus, involution.  Introduction:In
dairy farms of the Libya there is a decrease in reproductive function and a
decrease in the yield of calves, which causes great economic damage to the
industry 2, 3, 4, 5, 6. Reproductive quality of imported cattle (Holstein
breed) after the first calving decreased sharply, which is mainly due to the
technology of intensive milk production without taking into account the
physiological condition of cows. In this connection, the development of
technological methods for working with imported livestock in new conditions
requires its permission 7, 8, 9, 10, 11, 12. It is necessary to insert some
correction into the technology of cattle rehabilitation11,12 for rational solving
of the problem of reproduction, rise of cows’ milk productivity and receiving
viable remount cubs. It will provide the increase of the yield of remount
heifers with high genetic potential in productivity. There is some lowering of
reproductive function and decrease of calves’ yield in the farms of the country
on the whole. It economically harms the branch very much. Reproductive
capacities of import cattle (Holstein breed) sharply decrease after the first
calving what is mostly connected with the technology of intensive dairy
production without reference to cows’ physiological state1. That’s why, the
search of biotechnological ways of cattle reproduction for working with
high-productive animals is really necessary.The aim of the research is to
increase the reproductive capacity of cows and their productive longevity in
conditions of intensive milk production technology. On the basis of which the
following tasks were set: – to study the course of childbirth, the postpartum
period and the reproductive ability of cows in experimental groups; – to
determine the parameters of the biochemical composition of blood in correlation
with the duration of physiological periods. Material and methods:The material for research was
the highly productive animals of the Holstein breed of Libyan breeding. To
solve this problem, we have formed three groups of analogue-type spanners (by
age, term of pregnancy, origin), with different duration of the dry period: 60;
80; 90 days. Reproductive capacities of the examined groups of cows were
studied according to the following indices: duration of accouchement course,
postnatal period and recovery of cows’ reproductive capacity after calving.
Biochemical indices of blood were studied according to standard methods for the
control of metabolism state. Blood was taken from caudal vein 1.5-2 hours
before feeding in 5 cows from every group 15 days before calving. Biochemical
blood indices were studied according to generally accepted methods. Digital
material of experimental data was processes by the method of variation
statistics on difference reliability of comparable indices with the usage of
Student’s t-criterion taken in biology and zootechnics, with application of
program complex Microsoft Exel7. Reliability degree of the processed data are
shown by corresponding symbols – p<0.05*; p<0.01**; p<0.001.  Results:In the course of the research, we found that the length of labor is in correlation with the duration of the period of deadness. Thus, in the second and third groups, it is correspondingly smaller by 1.97 and 2.22 h than in the first group, which is apparently the result of the best morph functional state of the genital organs of the cows of the second and third groups of animals. It turned out that the duration of the involution of the uterus largely depends on the duration of the dry period, and also correlates with the duration of labor, which largely depends on the preparedness of the animals for calving. The duration of the end of the involution of the uterus was in the groups: in the first - 28,0 ± 4,2; in the second - 21.6 ± 1.62; in the third - 20.8 ± 1.13 days. Considering postpartum complications as one of the main causes of metabolic processes in the cows, the study of the parameters of hemodynamic changes in the blood of the animals being studied is of interest. To determine the relationship between the frequency of the pathology of the postpartum period and the metabolic processes in the organism of cows with different lengths of physiological periods, we performed a biochemical analysis of the blood of the experimental animals. The content of total protein in the blood serum of cows was in accordance with the norms, with an increase in the dry period, it increased slightly: if in the group of animals with a duration of 60 days of deadness the concentration of total protein in the serumwas 70.31 ± 1.24 g / l, then in the second and third groups it increased by 1.25, respectively; 0.46 g / l. At the same time, the blood sugar content of cows in the post-acute period was at the level of 2.17-2.39 mmol / l, with a significant decrease in blood sugar levels observed in animals with a greater lactation duration (first group). The duration of the dead period affects the reproductive quality of animals, which is confirmed by biochemical blood indicators, the gradient of which is closer to normal in animals with a duration of the dry period 80; 90 days. Fertility of cows in the first insemination was 40.0 in the first group, 60.0 in the second group, 70.0% in the third group. In the first group, 80.0% of the animals were fertilized after 4 inseminations (6-7 cycles after the birth), and 20.0% of cows after 5-6 insemination. Animals of the second and third groups inseminated 100.0% after three inseminations.Conclusion: Thus, the conducted studies show that optimization of the reproductive ability of cows and the level of their milk productivity due to the duration of the dry period provides an increase in the reproductive qualities of animals, prevents postpartum complications and reduces the timing of the involution of the genital organs in comparison with the control, and also improves the biochemical parameters of the blood. Optimization of dairy productivity level and period's duration provide the increase of adaptive properties in animals and high vitality of calves at birth will provide fuller realization of their genetic potential in periods of raising and exploitation.  Summary: Intensive genetic selection has resulted in modern dairy cow with very high milk yields but reduced fertility, due mainly to an increase in postpartum clinical problems, poor expression of oestrus, defective oocytes/embryos and uterine infections. It is a challenge to get enough food into these cows to meet the high demands of peak milk yields in early lactation and the animals require considerable veterinary attention in the early period after calving.The conducted studies show that optimization of the reproductive ability of cows and the level of their dairy productivity by increasing the duration of the dry period to 90 days ensures an increase in the reproductive qualities of animals, and an increase in the period of deadness prevents postpartum complications and reduces the timing of the involution of the genital organs compared with the control. The births in these groups of animals proceeded more quickly and without complications. The blood indicators of the animals under study reflect a violation of metabolic processes in their body.   Key words: blood, selection, breed, heifer, uterus, involution.     Introduction: In dairy farms of the Libya there is a decrease in reproductive function and a decrease in the yield of calves, which causes great economic damage to the industry 2, 3, 4, 5, 6. Reproductive quality of imported cattle (Holstein breed) after the first calving decreased sharply, which is mainly due to the technology of intensive milk production without taking into account the physiological condition of cows. In this connection, the development of technological methods for working with imported livestock in new conditions requires its permission 7, 8, 9, 10, 11, 12. It is necessary to insert some correction into the technology of cattle rehabilitation11,12 for rational solving of the problem of reproduction, rise of cows' milk productivity and receiving viable remount cubs. It will provide the increase of the yield of remount heifers with high genetic potential in productivity. There is some lowering of reproductive function and decrease of calves' yield in the farms of the country on the whole. It economically harms the branch very much. Reproductive capacities of import cattle (Holstein breed) sharply decrease after the first calving what is mostly connected with the technology of intensive dairy production without reference to cows' physiological state1. That's why, the search of biotechnological ways of cattle reproduction for working with high-productive animals is really necessary. The aim of the research is to increase the reproductive capacity of cows and their productive longevity in conditions of intensive milk production technology. On the basis of which the following tasks were set: - to study the course of childbirth, the postpartum period and the reproductive ability of cows in experimental groups; - to determine the parameters of the biochemical composition of blood in correlation with the duration of physiological periods.   Material and methods: The material for research was the highly productive animals of the Holstein breed of Libyan breeding. To solve this problem, we have formed three groups of analogue-type spanners (by age, term of pregnancy, origin), with different duration of the dry period: 60; 80; 90 days. Reproductive capacities of the examined groups of cows were studied according to the following indices: duration of accouchement course, postnatal period and recovery of cows' reproductive capacity after calving. Biochemical indices of blood were studied according to standard methods for the control of metabolism state. Blood was taken from caudal vein 1.5-2 hours before feeding in 5 cows from every group 15 days before calving. Biochemical blood indices were studied according to generally accepted methods. Digital material of experimental data was processes by the method of variation statistics on difference reliability of comparable indices with the usage of Student's t-criterion taken in biology and zootechnics, with application of program complex Microsoft Exel7. Reliability degree of the processed data are shown by corresponding symbols – p<0.05*; p<0.01**; p<0.001.     Results: In the course of the research, we found that the length of labor is in correlation with the duration of the period of deadness. Thus, in the second and third groups, it is correspondingly smaller by 1.97 and 2.22 h than in the first group, which is apparently the result of the best morph functional state of the genital organs of the cows of the second and third groups of animals. It turned out that the duration of the involution of the uterus largely depends on the duration of the dry period, and also correlates with the duration of labor, which largely depends on the preparedness of the animals for calving. The duration of the end of the involution of the uterus was in the groups: in the first - 28,0 ± 4,2; in the second - 21.6 ± 1.62; in the third - 20.8 ± 1.13 days. Considering postpartum complications as one of the main causes of metabolic processes in the cows, the study of the parameters of hemodynamic changes in the blood of the animals being studied is of interest. To determine the relationship between the frequency of the pathology of the postpartum period and the metabolic processes in the organism of cows with different lengths of physiological periods, we performed a biochemical analysis of the blood of the experimental animals. The content of total protein in the blood serum of cows was in accordance with the norms, with an increase in the dry period, it increased slightly: if in the group of animals with a duration of 60 days of deadness the concentration of total protein in the serum was 70.31 ± 1.24 g / l, then in the second and third groups it increased by 1.25, respectively; 0.46 g / l. At the same time, the blood sugar content of cows in the post-acute period was at the level of 2.17-2.39 mmol / l, with a significant decrease in blood sugar levels observed in animals with a greater lactation duration (first group). The duration of the dead period affects the reproductive quality of animals, which is confirmed by biochemical blood indicators, the gradient of which is closer to normal in animals with a duration of the dry period 80; 90 days. Fertility of cows in the first insemination was 40.0 in the first group, 60.0 in the second group, 70.0% in the third group. In the first group, 80.0% of the animals were fertilized after 4 inseminations (6-7 cycles after the birth), and 20.0% of cows after 5-6 insemination. Animals of the second and third groups inseminated 100.0% after three inseminations. Conclusion: Thus, the conducted studies show that optimization of the reproductive ability of cows and the level of their milk productivity due to the duration of the dry period provides an increase in the reproductive qualities of animals, prevents postpartum complications and reduces the timing of the involution of the genital organs in comparison with the control, and also improves the biochemical parameters of the blood. Optimization of dairy productivity level and period's duration provide the increase of adaptive properties in animals and high vitality of calves at birth will provide fuller realization of their genetic potential in periods of raising and exploitation.                    

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