Background and Aim: In repeat breeding, a sexually mature cow fails to conceive even after three or more consecutive inseminations despite being without any clinically detectable reproductive anomalies. This is a major cause of economic loss in livestock farms, particularly in developing countries, where humans and livestock directly compete for food, and the mineral content of animal feed is rarely checked. This study investigated the association between systemic iron, phosphorus, and total protein and estrous cyclicity in crossbred Holstein Friesian cows.

Materials and Methods: Blood samples were collected from 10 normal cyclic and 10 repeat breeder cows 12 h after the onset of estrus. Serum was separated, and iron, phosphorus, and total protein were quantified with spectrophotometry, using standard controls for all three measurement parameters (iron, phosphorus, and total protein).

Results: Iron and phosphorus levels were significantly (p<0.05) lower in the repeat breeders group than in the normocyclic group, but no significant differences were found in total protein levels.

Conclusion: Repeat breeding is associated with systemic iron and phosphorus levels but is independent of total protein level.

Keywords: crossbred cows, estrous cyclicity, normocyclic, repeat breeder/breeding.