After milk production, reproduction is the most economically important trait in dairy animals. Therefore, the maintenance of high fertility rate is basic to the success of any dairy farming enterprise. The practices adopted for the breeding management of dairy cows and buffaloes should aim at bringing about higher breeding efficiency.
The breeding efficiency is the measure of the capacity of an adult cow or buffalo to reproduce. It can be measured in terms of number of services taken by a cow or buffalo per conception, length of calving interval, percentage of non-returns and percentage of pregnancies in a breedable period.
i. Sexual Maturity and onset of Estrus Cycle
a) Puberty and sexual maturity: The stage of life in which animals become sexually mature and the secondary sexual characteristics first become clearly visible is known as “puberty.” In cow and buffalo heifers, this is the stage of first estrus (heat), and in the bull calf it is the stage when it starts giving semen with viable sperms. The term “sexual maturity” means that the heifers arecapable of reproduction. At this stage, reproductive organs undergo a marked increase in size.
Puberty occurs before mature body size is attained. Under good feeding, a calf attains puberty approximately at 66 per cent of adult body size. Breed, genotype,climate and level of feeding influence the age at puberty. The time of onset of puberty appears to be a function more of body size than of age. The sudden increase in size and weight of reproductive tract associated with puberty involves hormonal action.
b) Estrus cycle: Every 21±3days from the time of puberty, the cow prepares for a pregnancy. A mature ovum is liberated from the ovary, the cervix becomes receptive to the spermatozoa, the female exhibits behavioural adjustment and attraction to receive the male in copulation, the uterus and fallopian tubes produce the secretions which are conducive to the transport of ovum and sperms and the endometrial lining of the uterus prepares to receive and nourish a fertilized ovum. The events listed above in sum total are known as “estrus cycle.”
The estrus cycle has two major phases viz. estrogenic phase and progestational phase. The estrogenic phase or the period of follicle includes the proestrus and estrus and lasts for about 4 days of the cycle. The progestational phase or the lutealphase includes the metestrus and the diestrus and lasts for about 17 days.
ii. Symptoms of Heat and Heat Detection
The estrus or the heat is the period in which the animal exhibits sexual desire. The length of estrus period is between 8 to 24 hours in cows with an average of 18 hours. In buffaloes, the estrus period varies between 5 to 27 hours with an average of 20 hours. During summer the buffaloes have very short estrus period.
a) Symptoms of Heat: The cows in early stages of heat will show activities like smelling other cows, attempting to mount other cows and bellowing. They will be restless and their vulva will be moist, red and slightly swollen. After a time lapse of 6 to 8 hours, the heat will become more pronounced. The cow will stand to be mounted by other cows or bulls. Due to this, this period is termed as ‘standing heat’. This extends for 14 to 16 hours and shows other symptoms like bellowing, nervousness, anorexia, reduction in milk yield, clear mucus discharge and dilated pupil of eye.
b) Detection of Cows in Heat: The heat detection work may be carried out twice daily, once early in the morning and once in the evening. Disturbances like noise, visitors or other activities on the farm may be avoided at the time of detecting heat. Use of heat detection chart and breeding history of the cow should always be made while detecting heat. Parading of a teaser (vasectomized) bull amongst the cows in early morning and evening hours by a skilled person will greatly enhance the heat detection rate. Also keenly observing the expected cows and buffaloes while milking and while leaving the milking barn can improve heat detection rate. The other aids suggested to improve heat detection include the use of chin ball markers, heat mount detectors and pedometers.
iii. Artificial Insemination (AI) and Time of Breeding
a) Artifical Insemination: AI is the technique in which semen with living sperms is collected from the male animals and introduced into the female genital tract at proper time by mechanical means. The semen is collected from the bulls commonly by the artificial vagina technique. Then it is examined to judge its suitability for insemination by physical, microscopic, chemical and bacteriological tests. The good quality semen is extended further with an appropriate diluent to increase its utility in fertilizing more females. The freshly diluted liquid semen is then used for inseminating the cows and buffaloes in heat or preserved in frozen state for future use.
Advantages of AI: The AI technique offers many advantages over natural mating. It enables an individual bull to sire a large number of progeny. This reduces the number of bulls required for breeding purpose. The services of superior bulls are greatly extended allowing for the genetic evaluation of bulls through progeny testing. It is a major aid in crossbreeding work and in preventing the spread of genital diseases. Due to economic reasons, small farmers may not be in a position to maintain a bull. They can avail AI services at nominal cost.
b) Time of breeding: The time of breeding cows naturally or by AI is very important as it greatly influences the conception rate. The best time to breed cattle is from the middle of standing heat and six hours following that. Three or four hours perceeding or succeeding this excellent period also gives good results. As a routine practice, if a cow is seen showing early heat in the morning, it may be inseminated in the evening. If heat signs are first manifested in the evening, the cow may be bred next day morning. A cow is expected to show heat in 30-40 days after calving. Cows that fail to show heat even after 50 days have generally some problems and need examination.
The breeding efficiency is the measure of the capacity of an adult cow or buffalo to reproduce. It can be measured in terms of number of services taken by a cow or buffalo per conception, length of calving interval, percentage of non-returns and percentage of pregnancies in a breedable period.
i. Sexual Maturity and onset of Estrus Cycle
a) Puberty and sexual maturity: The stage of life in which animals become sexually mature and the secondary sexual characteristics first become clearly visible is known as “puberty.” In cow and buffalo heifers, this is the stage of first estrus (heat), and in the bull calf it is the stage when it starts giving semen with viable sperms. The term “sexual maturity” means that the heifers arecapable of reproduction. At this stage, reproductive organs undergo a marked increase in size.
Puberty occurs before mature body size is attained. Under good feeding, a calf attains puberty approximately at 66 per cent of adult body size. Breed, genotype,climate and level of feeding influence the age at puberty. The time of onset of puberty appears to be a function more of body size than of age. The sudden increase in size and weight of reproductive tract associated with puberty involves hormonal action.
b) Estrus cycle: Every 21±3days from the time of puberty, the cow prepares for a pregnancy. A mature ovum is liberated from the ovary, the cervix becomes receptive to the spermatozoa, the female exhibits behavioural adjustment and attraction to receive the male in copulation, the uterus and fallopian tubes produce the secretions which are conducive to the transport of ovum and sperms and the endometrial lining of the uterus prepares to receive and nourish a fertilized ovum. The events listed above in sum total are known as “estrus cycle.”
The estrus cycle has two major phases viz. estrogenic phase and progestational phase. The estrogenic phase or the period of follicle includes the proestrus and estrus and lasts for about 4 days of the cycle. The progestational phase or the lutealphase includes the metestrus and the diestrus and lasts for about 17 days.
ii. Symptoms of Heat and Heat Detection
The estrus or the heat is the period in which the animal exhibits sexual desire. The length of estrus period is between 8 to 24 hours in cows with an average of 18 hours. In buffaloes, the estrus period varies between 5 to 27 hours with an average of 20 hours. During summer the buffaloes have very short estrus period.
a) Symptoms of Heat: The cows in early stages of heat will show activities like smelling other cows, attempting to mount other cows and bellowing. They will be restless and their vulva will be moist, red and slightly swollen. After a time lapse of 6 to 8 hours, the heat will become more pronounced. The cow will stand to be mounted by other cows or bulls. Due to this, this period is termed as ‘standing heat’. This extends for 14 to 16 hours and shows other symptoms like bellowing, nervousness, anorexia, reduction in milk yield, clear mucus discharge and dilated pupil of eye.
b) Detection of Cows in Heat: The heat detection work may be carried out twice daily, once early in the morning and once in the evening. Disturbances like noise, visitors or other activities on the farm may be avoided at the time of detecting heat. Use of heat detection chart and breeding history of the cow should always be made while detecting heat. Parading of a teaser (vasectomized) bull amongst the cows in early morning and evening hours by a skilled person will greatly enhance the heat detection rate. Also keenly observing the expected cows and buffaloes while milking and while leaving the milking barn can improve heat detection rate. The other aids suggested to improve heat detection include the use of chin ball markers, heat mount detectors and pedometers.
iii. Artificial Insemination (AI) and Time of Breeding
a) Artifical Insemination: AI is the technique in which semen with living sperms is collected from the male animals and introduced into the female genital tract at proper time by mechanical means. The semen is collected from the bulls commonly by the artificial vagina technique. Then it is examined to judge its suitability for insemination by physical, microscopic, chemical and bacteriological tests. The good quality semen is extended further with an appropriate diluent to increase its utility in fertilizing more females. The freshly diluted liquid semen is then used for inseminating the cows and buffaloes in heat or preserved in frozen state for future use.
Advantages of AI: The AI technique offers many advantages over natural mating. It enables an individual bull to sire a large number of progeny. This reduces the number of bulls required for breeding purpose. The services of superior bulls are greatly extended allowing for the genetic evaluation of bulls through progeny testing. It is a major aid in crossbreeding work and in preventing the spread of genital diseases. Due to economic reasons, small farmers may not be in a position to maintain a bull. They can avail AI services at nominal cost.
b) Time of breeding: The time of breeding cows naturally or by AI is very important as it greatly influences the conception rate. The best time to breed cattle is from the middle of standing heat and six hours following that. Three or four hours perceeding or succeeding this excellent period also gives good results. As a routine practice, if a cow is seen showing early heat in the morning, it may be inseminated in the evening. If heat signs are first manifested in the evening, the cow may be bred next day morning. A cow is expected to show heat in 30-40 days after calving. Cows that fail to show heat even after 50 days have generally some problems and need examination.
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.