Cows that are cycling normally, with no clinical abnormalities, which have failed to conceive after at least three successive inseminations.
In practice, some will have been inseminated at the wrong time, others may have pathological changes in the bursa or oviduct that are difficult to palpate, or undiagnosed uterine infections.
Repeat breeders can be divided into two groups:
Cows that come into heat within 17-24 days after AI.
In these animals the luteal function has been shorter than normal or typical for the physiological oestrus cycle in non bred cow. In these cows the most probable event is either failure of fertilisation (delayed ovulation, poor semen quality etc.) or early embryonic death (delayed ovulation, poor embryo quality, unfavourable uterine environment, precocious luteolysis)
2. Late repeats
Cows that come into heat later than 25 days after AI.
In these animals the luteal function was maintained for longer than the physiological luteal phase in non bred cows. Fertilisation and initial recognition of pregnancy probably took place but for some reason (inadequate luteal function, inadequate embryo signalling, infectious diseases, induced luteolysis) luteolysis was induced and pregnancy lost.
Treatment of Repeat breeders
Repeat breeders should be carefully evaluated in order to define the most probable reason for the failure to conceive (early repeats) or failure in pregnancy maintenance (early and late repeats).
Principles of treating a Repeat Breeding Cow includes
- Ccorrecting the nutritional defeciency
- Correcting the uterine infections
- Correcting the hormonal defeciencies
- Use of assisted reproduction techniques
- Better heat detection and proper AI
1. Nutritional treatments
- Diets containing higher concentration of inorganic iodine from 8-12 days before estrus improve the stimulation of the pituitary gland
- Deficiencies of Copper and magnesium have been associated with infertility, anemia or immune suppression.
- Beta-carotene, precursor of vitamin A, has recently been investigated for its involvement in the formation and function of CL, it is suggested that beta-carotene improves the progesterone synthesis and reduces the luteal hypofunction
- Deficiencies of phosphorus and zinc are linked to low levels of progesterone, which could be the cause of failures in fertilization or early embryonic death.
In conclusion, it is important to consider the nutritional imbalance in Repeat Breeding Cows, However, it is not practical to analyze the mineral or chemical composition in blood. It is better to administer 50g of mineral mixture/cow/pay orally in order to avoid disruptions to the reproductive function.
2. Intrauterine treatment
It is considered that between 36 and 89% of Repeat Breeding Cows show uterine diseases but are often difficult to detect in field conditions.
- Prophylactic intra uterine administration of antiseptic solutions (lugols Iodine) 24 h. after mating/AI, although fertility results are poor.
- Studies on bacteriology and histology of the uterus concluded that the non-specific genital infection is one of the main causes of Repeat Breeding Cows, and it is suggested that antimicrobial treatments (chloramphenicol, gentamicin, enrofloxacin, tetracycline, or nitrofurantine) could improve the reproductive indexes.
3. Hormonal treatments
i .Progesterone (Pg)
- Administration of progesterone as of 3 to 5 days after insemination and for 2-3 weeks (or more) improves conception rates in Repeat Breeding Cows.
- Repeat Breeding Cow has been administered 250 mg of retard progesterone on days 4, 14, 24, 34, 44 and 54 after insemination, the pregnancy rate was 96% versus 20% in control cows.
- Insertion of intravaginal devices (PRID) for 14 days in Repeat Breeding Cows improved the ovulation and shortened the calving-conception interval.
- The delayed formation of the CL induces estrus repetition, and then suggest that progesterone therapy should be started on 4-5th day after insemination.
ii. GnRH (gonadotrophin-releasing hormone)
- The administration of GnRH around the insemination time aims to accelerate and ensure ovulation in cows, acting directly on the pituitary, stimulating the secretion and release of gonadotrophins, such as LH and FSH, and promoting the preovulatory LH peak, which is essential for follicular dehiscence. In many cases, Repeat Breeding syndrome is associated with ovulatory defects, as anovulation, delayed ovulation or gonadotrophin release failure.
- If luteal deficiency is suspected as reproductive failure in cows, GnRH (100 µg) could be used on day 5 post-AI It has also been combined with intrauterine antibiotic (infusion of 30-50 ml containing 300000 IU penicillin and 0,5 g streptomycin), increasing fertility in RBCs. This treatment could be more appropriate when abnormal vulvar conformation is present.
- Administration of GnRH at the time of AI may be beneficial for improving fertility in these cows, It is also suggested that pregnancy rates can be improved by increasing the insemination frequency.
iii. Exogenous gonadotrophin
- These hormones have been used in Repeat Breeding Cows to induce ovulation and exert the luteotrophic effect on the CL.
- Intramuscular administration of pregnant mare serum (PMS) on day 15 or 16 of the estrous cycle, obtaining a conception rate of 73,9% in Repeat Breeding Cows compared with 44,4% of control cows.
- However, HCG is the most used exogenous gonadotrophin for treating RBC syndrome, treatment with hCG on day 5 after insemination can achieve higher levels of progesterone for at least 2 weeks, due to the development of accessory CL.
- In this case the luteolytic effect of prostaglandins has been used to treat Repeat Breeding Cows, treatment aims to achieve better heat detection and to increase the number of cows in heat.
- Two PGF2alpha injections apart 11 days and insemination 80 hours later, Intravenous PGF2alpha (0,2 ml cloprostenol) has also been reported in Repeat Breeding Cowss at AI time. However,
- The most frequent use of this hormone has been combined with other substances, serving as a pretreatment and with the ultimate goal of improving the reproductive management.
4. Use of Assisted Reproduction Techniques:
- Abnormal implantation and transport of gametes are associated with endometrial defects, resulting in Repeat Breeding Cow syndrome, In this case following assisted reproduction techniques may be used.
- Intraperitoneal insemination could be an alternative procedure to the normal deposition of semen in the genital tract of the cow. A bypass from vagina to peritoneal area (around the ovary) is possible to avoid the negative effects of altered uterine environment on the sperm quality.
- The majority of embryonic abnormalities occur in the oviducts, but are not apparent until 6-7 days post-breeding. Then, oocytes of RBCs are competent to reach the blastocyst stage. IVM, IVF, IVC and ET techniques are proposed to improve the reproductive success in these animals.
5. Better heat detection and proper Artificial Insemination
Vets are requested to add your valuable points in the comments section