Genetic Relationship between Lactation Curve Traits in Dairy Cattle

Abstract

Dairy cattle selection strategy in Kenya prefers cows with good 305-day lactation milk yield (TMY) in previous parity. This has improved milk production although increased incidences of physiological disorders and reduced fertility have been reported in herds. Records on functional traits are scarce. Properties of lactation curves could indirectly explain reproductive efficiency in cows. This study assesses relationship between lactation curve traits, to evaluate effects of selection for TMY on lactation curve properties, to explain reduced physiological efficiency and fertility. Genetic correlations between peak milk yield (MYmax) and persistency (S), MYmax and Days in milk at peak (DIMP), TMY and DIMP were negative. Genetic correlations were positive between DIMP and S, TMY and MYmax implying that selection for high TMY increases MYmax and reduces DIMP. This shifts production pressure to early lactation aggravating negative energy balance thus compromising physiological integrity of cows