What are the reasons for low conception rates in dairy cattle breeding?
Analysis of possible reasons for low conception rates in dairy cattle breeding
The issue of conception rates in artificial insemination of dairy cattle is something that every technician and manager takes very seriously. It sounds simple enough, but if it were really that simple, your conception rate would not be stuck where it is! Some of the views in this post come from reference materials, some from personal experience, and some are conjectures. I have roughly outlined the following possible reasons:
1. Reasons related to artificial insemination technique and handling.
2. Reasons related to ovulation and the egg in the cow.
3. Reasons related to semen.
4. Reasons related to reproductive diseases.
5. Reasons related to early embryonic death.
Before analyzing the above five aspects in detail, let us first clarify three concepts:
1、Estrous cycle Refers to the interval from the beginning of one estrus to the beginning of the next estrus. The estrous cycle of a cow is 18-24 days, with an average of 21 days. The estrous cycle is generally divided into four stages: proestrus, estrus, metestrus and diestrus.
2、Estrus period Also called the duration of estrus, refers to the period with obvious signs of estrus. In cows, there is expression of sexual desire, the vulva becomes congested and gradually more so, the uterus becomes congested and contractions increase, mucus flows out, the cervical canal relaxes, and the follicle develops rapidly. For multiparous cows it lasts 12-30 hours, and for maiden heifers 10-20 hours.
3、Conception rate per estrusRefers to the percentage of pregnant cows out of the number of estrous periods bred. To a certain extent, it better reflects the conception result and the breeding level. The conception rate per estrus can be divided into first-service conception rate per estrus and overall conception rate per estrus.
To be continued. I will continue posting after the post is reviewed. Some content still needs more thought. Feedback is welcome!
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1. Possible reasons related to artificial insemination technique and handling
1. Inaccurate estrus observation. Once we understand the concept of the duration of estrus, we realize that in estrus observation we can only observe the duration of estrus. The most important thing is to observe the time when the cow starts estrus, that is, the time when she begins to stand firmly to be mounted. Because some cows start estrus at night, and some show silent estrus, it is somewhat difficult to accurately determine the time when a cow starts estrus, so sometimes we have to judge from the degree of swelling of the cow's vulva and the thinness of the mucus.
2. Insemination too early or too late. Generally, the insemination time is 12 hours after the cow begins to stand firmly to be mounted for the first insemination, and 24 hours for the second insemination. For multiparous cows, 24 hours is the key, while for some maiden heifers, 12 hours is the key. This is because multiparous cows ovulate 10-12 hours after the end of estrus, and maiden heifers ovulate earlier. Sperm reaches the fertilization site in 30 minutes, and sperm and egg still need time for capacitation. The optimal insemination time should be the time when estrus is ending, which from external appearance is when the cow has already begun not to accept mounting, and the mucus is absent or very thick.
3. Operate as aseptically as possible and be sure to pay attention to hygiene. When the cow defecates, feces will more or less stick to the vulva. Some people reuse one sheath repeatedly, making asepsis very difficult. Some people remove the sheath too early, allowing bacteria from the air to be picked up. Too many inseminations can also infect the uterus. So dirty work still has to be done cleanly.
4. Semen backflow. Sometimes semen backflows because the insemination gun and sheath do not match or the sheath is not fastened tightly. After insemination, check carefully.
5. When injecting semen, using too much force causes sperm death.
6. The insemination gun reaches the uterine body, the gun body tilts upward, and semen flows onto the sheath and is carried back with the gun. Think about it, there is only 0.25 ml. So the gun should be tilted downward as much as possible, and while injecting, withdraw slightly backward.
7. Movements too stiff and unskilled, causing injury and bleeding to the vagina, cervix and uterine mucosa.
8. Sperm rapidly die from low temperature, high temperature, vibration, ultraviolet light and other insults.
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2. Reasons related to ovulation and the fertilizing ability of the egg in cows
1. In multiparous cows it generally occurs 10-12 hours after the end of estrus, and in maiden heifers it is relatively earlier. Some cows often ovulate later because of improper feeding and management. These cows often have normal estrous cycles, and their eggs also have normal fertilizing ability, so they cannot be considered diseased; adjusting the insemination time can solve the problem.
2. Some references indicate that the eggs released by maiden heifers at puberty have no fertilizing ability, and the low conception rate of multiparous cows at the first estrus after calving is also a problem of the fertilizing ability of the egg.
3. I conjecture that endocrine disorders caused by improper feeding and management (nutrition, exercise, concentrate-to-roughage ratio, milk let-down promotion, etc.) will also affect the conception rate. Endocrine disorders cause the egg to fail to undergo normal capacitation, that is, it has no fertilizing ability. On the other hand, endocrine disorders cause abnormal contractions of the reproductive tract, so the egg cannot reach the fertilization site normally or stays in the ampulla of the oviduct for too short a time, and sperm and egg cannot unite.
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3. Possible reasons related to semen
1. Almost everyone pays attention to how low semen motility and low density affect the conception rate. With semen motility of 0.3 or 0.4, the number of effective sperm does not necessarily reach 10 million; besides the influence of density, there is also the issue of acrosome integrity rate.
2. Storage of semen. After semen is thawed, keep it at as constant a temperature as possible, and protect it as much as possible from low temperature, high temperature, vibration, sunlight and ultraviolet light and other insults. The shorter the storage time outside the body, the better; no matter how good the external environment is, it cannot compare with the environment of the cow's reproductive tract.
3. The effect of sperm survival time on the conception rate.
Raw semen survives in the cow's body for more than 72 hours. According to national standards, thawed semen is required to be kept in a constant-temperature incubator at 37°C for more than 4 hours. Due to the influence of extender preparation, dilution ratio and processing technology, there are great differences in the survival time of thawed semen outside the body and inside the body. If the survival time is short, the conception rate is low.
--------------------------------------
Bookmarked, thanks OP
--------------------------------------
Sperm rapidly die from low temperature, high temperature, vibration, ultraviolet light and other insults
--------------------------------------
4. Reproductive diseases plague dairy cattle farming
1. Endometritis
Endometritis is a common disease of dairy cows. Cows with mild endometritis have normal estrus and normal ovulation, but remain infertile after repeated breeding. Its harm is that on the one hand it blocks the normal movement of sperm, and on the other hand it prevents the embryo from implanting. Causes include poor disinfection during calving assistance, poor barn hygiene, poor disinfection during breeding, too many inseminations, poor feeding and management leading to reduced body resistance, and certain infectious diseases. In practice, it can generally be diagnosed based on the color of the mucus. During rectal examination, if the cow shows a pain response, the contraction response is not obvious, and the cow strains severely, endometritis should be considered.
2. Follicular cyst
Follicular cyst manifests as prolonged duration of estrus and irregular estrous cycles in the cow. On rectal examination, the cow's tail base is raised, the cervical opening is enlarged, the uterine contraction response is not obvious, and the ovary is as large as a chicken egg.
3. Delayed ovulation or alternating follicle development
The cow has a normal estrous cycle, but the duration of estrus is prolonged. Judgment can only be made through multiple rectal examinations.
4. Brucellosis
Everyone in animal husbandry knows brucellosis. The main symptom is abortion at 5-8 months. Its effect on the conception rate is mainly inflammation of the reproductive system and infertility after repeated breeding. Because this disease is a class of zoonotic infectious disease with a wide distribution, once brucellosis is found, it must be culled according to legal provisions. The animal husbandry functional departments are also in a difficult position: if they cull the animals, they have to compensate the owners, and the government cannot come up with that much money, so they can only conceal it and not report it. Technicians newly entering the animal husbandry industry must attach importance to brucellosis, both for the sake of production and for the sake of their own and their families' health!
In practice, I have summarized a rough diagnostic method for brucellosis under conditions without a laboratory: when the cow is in estrus, put plastic film gloves on both hands, insert one hand deep into the cow's rectum and massage the uterus to keep the cow calm; if the discharged mucus is gray, use the other hand to open the vulva and observe the vaginal mucosa; if there are pink nodules smaller than a millet grain, then it is most likely brucellosis. In cows not in estrus, pink nodules can also be seen, sometimes white.
5. Campylobacteriosis
This disease manifests as temporary infertility and abortion, prolonged duration of estrus, and clear mucus.
I have not seen cases of this disease myself, so I will not say much.
6. Infectious bovine rhinotracheitis, reproductive form
I have not seen cases either, so I will not say much.
7. Bovine trichomoniasis
According to an old veterinarian, cows with this disease show severe itching.
8. Oophoritis and salpingitis, oviduct obstruction
1. Reasons related to artificial insemination technique and handling.
2. Reasons related to ovulation and the egg in the cow.
3. Reasons related to semen.
4. Reasons related to reproductive diseases.
5. Reasons related to early embryonic death.
Before analyzing the above five aspects in detail, let us first clarify three concepts:
1、Estrous cycle Refers to the interval from the beginning of one estrus to the beginning of the next estrus. The estrous cycle of a cow is 18-24 days, with an average of 21 days. The estrous cycle is generally divided into four stages: proestrus, estrus, metestrus and diestrus.
2、Estrus period Also called the duration of estrus, refers to the period with obvious signs of estrus. In cows, there is expression of sexual desire, the vulva becomes congested and gradually more so, the uterus becomes congested and contractions increase, mucus flows out, the cervical canal relaxes, and the follicle develops rapidly. For multiparous cows it lasts 12-30 hours, and for maiden heifers 10-20 hours.
3、Conception rate per estrusRefers to the percentage of pregnant cows out of the number of estrous periods bred. To a certain extent, it better reflects the conception result and the breeding level. The conception rate per estrus can be divided into first-service conception rate per estrus and overall conception rate per estrus.
To be continued. I will continue posting after the post is reviewed. Some content still needs more thought. Feedback is welcome!
--------------------------------------
1. Possible reasons related to artificial insemination technique and handling
1. Inaccurate estrus observation. Once we understand the concept of the duration of estrus, we realize that in estrus observation we can only observe the duration of estrus. The most important thing is to observe the time when the cow starts estrus, that is, the time when she begins to stand firmly to be mounted. Because some cows start estrus at night, and some show silent estrus, it is somewhat difficult to accurately determine the time when a cow starts estrus, so sometimes we have to judge from the degree of swelling of the cow's vulva and the thinness of the mucus.
2. Insemination too early or too late. Generally, the insemination time is 12 hours after the cow begins to stand firmly to be mounted for the first insemination, and 24 hours for the second insemination. For multiparous cows, 24 hours is the key, while for some maiden heifers, 12 hours is the key. This is because multiparous cows ovulate 10-12 hours after the end of estrus, and maiden heifers ovulate earlier. Sperm reaches the fertilization site in 30 minutes, and sperm and egg still need time for capacitation. The optimal insemination time should be the time when estrus is ending, which from external appearance is when the cow has already begun not to accept mounting, and the mucus is absent or very thick.
3. Operate as aseptically as possible and be sure to pay attention to hygiene. When the cow defecates, feces will more or less stick to the vulva. Some people reuse one sheath repeatedly, making asepsis very difficult. Some people remove the sheath too early, allowing bacteria from the air to be picked up. Too many inseminations can also infect the uterus. So dirty work still has to be done cleanly.
4. Semen backflow. Sometimes semen backflows because the insemination gun and sheath do not match or the sheath is not fastened tightly. After insemination, check carefully.
5. When injecting semen, using too much force causes sperm death.
6. The insemination gun reaches the uterine body, the gun body tilts upward, and semen flows onto the sheath and is carried back with the gun. Think about it, there is only 0.25 ml. So the gun should be tilted downward as much as possible, and while injecting, withdraw slightly backward.
7. Movements too stiff and unskilled, causing injury and bleeding to the vagina, cervix and uterine mucosa.
8. Sperm rapidly die from low temperature, high temperature, vibration, ultraviolet light and other insults.
--------------------------------------
2. Reasons related to ovulation and the fertilizing ability of the egg in cows
1. In multiparous cows it generally occurs 10-12 hours after the end of estrus, and in maiden heifers it is relatively earlier. Some cows often ovulate later because of improper feeding and management. These cows often have normal estrous cycles, and their eggs also have normal fertilizing ability, so they cannot be considered diseased; adjusting the insemination time can solve the problem.
2. Some references indicate that the eggs released by maiden heifers at puberty have no fertilizing ability, and the low conception rate of multiparous cows at the first estrus after calving is also a problem of the fertilizing ability of the egg.
3. I conjecture that endocrine disorders caused by improper feeding and management (nutrition, exercise, concentrate-to-roughage ratio, milk let-down promotion, etc.) will also affect the conception rate. Endocrine disorders cause the egg to fail to undergo normal capacitation, that is, it has no fertilizing ability. On the other hand, endocrine disorders cause abnormal contractions of the reproductive tract, so the egg cannot reach the fertilization site normally or stays in the ampulla of the oviduct for too short a time, and sperm and egg cannot unite.
--------------------------------------
3. Possible reasons related to semen
1. Almost everyone pays attention to how low semen motility and low density affect the conception rate. With semen motility of 0.3 or 0.4, the number of effective sperm does not necessarily reach 10 million; besides the influence of density, there is also the issue of acrosome integrity rate.
2. Storage of semen. After semen is thawed, keep it at as constant a temperature as possible, and protect it as much as possible from low temperature, high temperature, vibration, sunlight and ultraviolet light and other insults. The shorter the storage time outside the body, the better; no matter how good the external environment is, it cannot compare with the environment of the cow's reproductive tract.
3. The effect of sperm survival time on the conception rate.
Raw semen survives in the cow's body for more than 72 hours. According to national standards, thawed semen is required to be kept in a constant-temperature incubator at 37°C for more than 4 hours. Due to the influence of extender preparation, dilution ratio and processing technology, there are great differences in the survival time of thawed semen outside the body and inside the body. If the survival time is short, the conception rate is low.
--------------------------------------
Bookmarked, thanks OP
--------------------------------------
Sperm rapidly die from low temperature, high temperature, vibration, ultraviolet light and other insults
--------------------------------------
4. Reproductive diseases plague dairy cattle farming
1. Endometritis
Endometritis is a common disease of dairy cows. Cows with mild endometritis have normal estrus and normal ovulation, but remain infertile after repeated breeding. Its harm is that on the one hand it blocks the normal movement of sperm, and on the other hand it prevents the embryo from implanting. Causes include poor disinfection during calving assistance, poor barn hygiene, poor disinfection during breeding, too many inseminations, poor feeding and management leading to reduced body resistance, and certain infectious diseases. In practice, it can generally be diagnosed based on the color of the mucus. During rectal examination, if the cow shows a pain response, the contraction response is not obvious, and the cow strains severely, endometritis should be considered.
2. Follicular cyst
Follicular cyst manifests as prolonged duration of estrus and irregular estrous cycles in the cow. On rectal examination, the cow's tail base is raised, the cervical opening is enlarged, the uterine contraction response is not obvious, and the ovary is as large as a chicken egg.
3. Delayed ovulation or alternating follicle development
The cow has a normal estrous cycle, but the duration of estrus is prolonged. Judgment can only be made through multiple rectal examinations.
4. Brucellosis
Everyone in animal husbandry knows brucellosis. The main symptom is abortion at 5-8 months. Its effect on the conception rate is mainly inflammation of the reproductive system and infertility after repeated breeding. Because this disease is a class of zoonotic infectious disease with a wide distribution, once brucellosis is found, it must be culled according to legal provisions. The animal husbandry functional departments are also in a difficult position: if they cull the animals, they have to compensate the owners, and the government cannot come up with that much money, so they can only conceal it and not report it. Technicians newly entering the animal husbandry industry must attach importance to brucellosis, both for the sake of production and for the sake of their own and their families' health!
In practice, I have summarized a rough diagnostic method for brucellosis under conditions without a laboratory: when the cow is in estrus, put plastic film gloves on both hands, insert one hand deep into the cow's rectum and massage the uterus to keep the cow calm; if the discharged mucus is gray, use the other hand to open the vulva and observe the vaginal mucosa; if there are pink nodules smaller than a millet grain, then it is most likely brucellosis. In cows not in estrus, pink nodules can also be seen, sometimes white.
5. Campylobacteriosis
This disease manifests as temporary infertility and abortion, prolonged duration of estrus, and clear mucus.
I have not seen cases of this disease myself, so I will not say much.
6. Infectious bovine rhinotracheitis, reproductive form
I have not seen cases either, so I will not say much.
7. Bovine trichomoniasis
According to an old veterinarian, cows with this disease show severe itching.
8. Oophoritis and salpingitis, oviduct obstruction