| Etiology Causative Agent |
The aetiology of RB appears to be multi-factorial. The reason may be genetic, environmental, infections, altered ovarian activity. All these etiological factors ultimately results into either failure in fertilization or embryonic death that leads to repeat breeding. The major reasons for repeat breeding are:
Genetics : Chromosomal or genetic abnormalities of parent and those defects that occur during the differentiation process may negatively affect fertility. For example Repeat Breeding has been noticed in cows with chromosomal abnormalities as translocation 1/29 or trisomy X (Roberts, 1971; Lafi & Kaneene, 1988; Bruyas et al., 1993). Factors like inbreeding, aged gamete also may provoke genetic defects leading to repeat breeding. There also exists breed difference in occurrence of repeat breeding in cattle. The incidence of repeat breeding is mostly prevalent in Jersey and Holstein cross bred cattle in our country.
Age : Effect of age on fertility is commonly reported as negative (Hodel et al., 1995). Higher incidences of repeat breeding have been seen in old cows (Hewett, 1968). It is observed that fertility in dairy cows get better after the 1st or 2nd parturition, and then declines from the 4th and 5th (Dominguez, 1989).
Uterine infection and repeat oestrous cycles : The uterine environment encourages the normal embryonic development. Hence, any disorder or defects like uterine infections, endometritis, pyometra, metritis etc adversely affects the survival of the embryo causing embryonic death which is also one of the major reasons for repeat breeding. Uterine infections negatively influence the uterine and cervical postpartum involution, follicular development, causes embryo mortality and repeat estrus rates (Lewis, 1997, Santana et al., 1998).
Anatomical defects of the genital tract : The reproductive tract of cow offers a appropriate atmosphere for oocyte growth, sperm transport, fertilization and implantation. Anatomical or functional alterations of these structures can compel gestational failure and repeat breeding.
Improper ovarian function : The problem of ovarian cysts in dairy cows is a serious reason of reproduction failure. Cystic ovarian degeneration (COD) is a cause of repeat breeding in cattle. Delayed ovulation, anoestrus are also linked with this problem. Luteal inadequacy resulting into progesterone deficiency may provoke repeat breeding syndrome.
Nutritional causes : The conception of the cows is associated with body weight. Mandatory weight which cows should achieve before breeding is for indigenous and jersey cross heifer 240-275 kg and for HF cross heifer 260-290 kg. Underweight animals show poor rates of conception. Balanced feeding (energy, fat, protein, vitamins and minerals) is the solution for this. The trace minerals particularly copper, cobalt, iron etc. are requisite for steroidogensis. Supplementing trace minerals and Vitamins A, D3and E, can assist in treating the problem of anoestrus/repeat breeding dairy animals (Garg et al., 2008).
Artificial insemination : Any disorder at any action involving bull preparation, artificial vagina preparation, semen collection, semen processing, storage, thawing, post-thaw handling of semen, incorrect insemination in relation to stage of oestrus may result into repeat breeding. If animals are not inseminated at accurate time, it may cause conception failure. We should inseminate the indigenous cows according to AM.-P.M. rule i.e. if a cow comes in heat in morning, she should be inseminated in the same day evening and if came to heat on evening she should be inseminated on next day morning. The exotic/crossbred should be inseminated in mid to late heat. It is better to give double insemination should always be done with the gap of 12-24 hours after first AI in crossbreds.
The aetiology of RB appears to be multi-factorial. The reason may be genetic, environmental, infections, altered ovarian activity. All these etiological factors ultimately results into either failure in fertilization or embryonic death that leads to repeat breeding. T
The major reasons for repeat breeding are:
Genetics : Chromosomal or genetic abnormalities of parent and those defects that occur during the differentiation process may negatively affect fertility. For example Repeat Breeding has been noticed in cows with chromosomal abnormalities as translocation 1/29 or trisomy X (Roberts, 1971; Lafi & Kaneene, 1988; Bruyas et al., 1993). Factors like inbreeding, aged gamete also may provoke genetic defects leading to repeat breeding. There also exists breed difference in occurrence of repeat breeding in cattle. The incidence of repeat breeding is mostly prevalent in Jersey and Holstein cross bred cattle in our country.
Age : Effect of age on fertility is commonly reported as negative (Hodel et al., 1995). Higher incidences of repeat breeding have been seen in old cows (Hewett, 1968). It is observed that fertility in dairy cows get better after the 1st or 2nd parturition, and then declines from the 4th and 5th (Dominguez, 1989).
Uterine infection and repeat oestrous cycles : The uterine environment encourages the normal embryonic development. Hence, any disorder or defects like uterine infections, endometritis, pyometra, metritis etc adversely affects the survival of the embryo causing embryonic death which is also one of the major reasons for repeat breeding. Francos (1979) noticed that from 3.5 to 5.7% of cows suffering from metritis had repeat estrus. Uterine infections negatively influence the uterine and cervical postpartum involution, follicular development, causes embryo mortality and repeat estrus rates (Lewis, 1997, Santana et al., 1998).
Anatomical defects of the genital tract : The reproductive tract of cow offers a appropriate atmosphere for oocyte growth, sperm transport, fertilization and implantation. Anatomical or functional alterations of these structures can compel gestational failure and repeat breeding.
Improper ovarian function : The problem of ovarian cysts in dairy cows is a serious reason of reproduction failure. Cystic ovarian degeneration (COD) is a cause of repeat breeding in cattle. Delayed ovulation, anoestrus are also linked with this problem. Luteal inadequacy resulting into progesterone deficiency may provoke repeat breeding syndrome.
Nutritional causes : The conception of the cows is associated with body weight. Mandatory weight which cows should achieve before breeding is for indigenous and jersey cross heifer 240-275 kg and for HF cross heifer 260-290 kg. Underweight animals show poor rates of conception. Balanced feeding (energy, fat, protein, vitamins and minerals) is the solution for this. Supplementing trace minerals and Vitamins A, D3 and E, can assist in treating the problem of anoestrus/repeat breeding dairy animals (Garg et al., 2008).
Artificial insemination : Any disorder at any action involving bull preparation, artificial vagina preparation, semen collection, semen processing, storage, thawing, post-thaw handling of semen, incorrect insemination in relation to stage of oestrus may result into repeat breeding. If animals are not inseminated at accurate time, it may cause conception failure. We should inseminate the indigenous cows according to AM.-P.M. rule i.e. if a cow comes in heat in morning, she should be inseminated in the same day evening and if came to heat on evening she should be inseminated on next day morning. The exotic/crossbred should be inseminated in mid to late heat. It is better to give double insemination should always be done with the gap of 12-24 hours after first AI in crossbreds |
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