When dairy cow or buffalo after insemination does not fall pregnant or express heat after every 21 days it is repeat breeding. It is a big problem for dairy animals. With advancement of lactation length milk production is reduced and you are losing a calf. The cow should be calving once a year. So, every year in same month it should give calve if not, you will loss milk and calf.
It is necessary for dairy animal that they start exhibiting heat after a month of calving and then they should repeated heat on every 21 days. It should be express heat after a 12 month of age or when it attains half of its adult weight which is 200 to 250 kg.
The reproduction is function of season, environment, temperature, nutrition and photo-period, of that photo-period that governs the reproduction. At equator the photo-period is same but in northern or southern hemisphere the photo-period is different in winter and summer. When you import animals you should bear in mind that the country (India) when you imported cow they are from Canada, Australia, Brazil or Israel. If you are imported semen it should be noted that it is from ABS India. Because these companies (ABS India), selected different bulls for semen for India.
Holstein is also two type, one Holstein is selected for snow covered area and other for desert like Arabic India Israel or Brazil. So, if you will use semen from Canada or North America, it may not work here, India has imported bulls from Germany, America or Australia or we have imported embryos or we have imported from Canada. It may not work in India. Particularly it is hot and dry in the most part of India. However it may work in hills of northern India. Punjab has used ABS India semen from about 20 years. So, there may not much in problem, same may true for Bangalore. In my personal opinion as environment physiologist I strongly feel that we should not use importuned bulls particularly when they come as a gift from Europe or Australia. Brazilian or Israel breeds, some will work because there are same environmental conditions as in India.
Said the above let use come to the seasonal aspect of reproduction. If exotic cows are inseminated in November and December, than it expected it calve in July, August. These are very stressful month because relative humidity is 90% and temperature is near 40°C. Further the cow is in transition period 20 days before and 20 days after calving so it will suffer of retention of placenta, matritis, and mastitis etc. In fact I have visited a farm in Haryana when they do not take up artificially insemination from 15 August to 26 January they were telling that in Holstein you suffer less loss in milk, calf and death of cow.
Many cows, 30% of cow inseminated come in heat. So, for second insemination the semen should be left on the mouth of cervix. Now due to new technology (Immunises and detection of easily pregnancy affecter) you can detect pregnancy on 17th days of insemination. But cow not coming in heat is also not a sure sign of pregnancy. So, pregnancy diagnosis is must after AI. It is usually done at 60 days but expert veteran may do this at 35 days too.
The environmental temperature outside is above body temperature then the rectal in exotic cow will go above 39°C. At this rectal temperature exotic cow will not conceive. So, get your cow inseminated after 6 pm and give less feed for 2 days. The 6 hours after insemination and 6 days after, are very critical. The cow should be housed below 20°C.
In buffalo the environment temperature is not an issue. Buffalo breeds in winter. And the length its estrous cycle is long. Buffaloes remain in heat for several days. Some pregnant buffaloes also exhibit heat. Buffaloes and cows may always remain in heat for in case of cystic ovary these are treated with GnRh. Consult your veteran. Sometimes there is luteal cyst this can be treated by Postaglandin (PG Alfa two). Consult your Veteran. The above conditions are rare but in a heart of 20 cows you may have one or two cows of cysytic type. For better conception GnRh, in market is available in the name of PROGULATE (Virback) or Receptal (MSD), consult your veteran.