Heifers
As efficient reproductive performance is essential for economic livestock production, the female calves must grow rapidly to attain sexual maturity, ovulate and be mated by fertile males or inseminated with quality semen to optimize conception and production. Indian livestock suffer from slow growth rate and delayed puberty. Buffaloes in particular, display sexual maturity at a very advanced age. Despite optimum feeding, the Murrah buffalo – perhaps the best known buffalo milch breed- has been shown to attain puberty at an age of 33 months . Delayed sexual maturity generally results from underfeeding energy or protein and ecto- and endo-parasitic infestation. Heat stress under tropical environmental conditions also delays puberty attainment. Under rural conditions the incidence of delayed sexual maturity is alarming extending even upto 60 months of age. Anemia from parasitic infestation or faulty nutrition (low protein, selenium, phosphorous, vitamins A,D and E or iron), plays a major role in extending the age at puberty. Genital abnormalities viz. a small percentage of heifers (< 1%) suffer from free martinism -failure of reproductive tract to develop, closed cervix or blocked oviduct. Since age at sexual maturity is better correlated with body weight than chronological age, nutrition of young stock becomes important. Ideally, developing heifers should achieve between 65and 70% of their adult weight at breeding, approximately at 14to 15 months (exotic and crossbred) and 20 to 25 months (indigenous cattle and buffaloes) of age. Under different studies conducted at National Dairy Research Institute the age at puberty for crossbred cows (Karan Swiss and Karan Fries) was about 2 years despite optimum feeding. It is quite obvious that climatic influences also contribute towards late occurrence of sexual maturity in dairy livestock.
Health care management apart from good nutrition is very useful in helping enhancement of pubertal age. Specifically, timely deworming schedule should be followed to rid the young stock of endo-parasites / helminthes present in the gastro- intestinal tract that compete with the hosts for nutrients in addition to the possibility of causing diseases. Ecto-parasiticides may be used as and when required. Additionally, following a vaccination schedule should not be ignored as it is required to boost the immunity of young animals due to the reduction in the levels of immunoglobulins obtained from the colostrum.
Cows/buffaloes
Infertility remains a major economic problem and its incidence is rising; the advancements made in controlling reproductive disorders remains equivocal. As the size of dairy herd increases, more intensive management systems are needed to maximize milk production, and overall herd fertility often decreases. High levels of milk production in dairy cattle can have negative side effects on health and fertility traits. Majority of cattle and buffaloes (18 to 40%) are culled and reach slaughterhouse primarily due to infertility. Slaughterhouse studies revealed the incidence of reproductive disorders in buffaloes alone to be about 37.5%. At any given point of time animals with reproductive problems should not exceed 10%.