Milk yield performance in KiwiCross x Holstein crossbred dairy cows under rotational grazing conditions in the Andean high-tropics

Reduced milk yield remains a major constraint in grazing dairy systems under high tropical conditions, particularly when crossbreeding strategies are not adequately aligned with nutritional management. This study aimed to identify factors associated with reduced milk yield in non-supplemented KiwiCross crossbred grazing dairy cattle managed under high tropical conditions. Time-series analysis was used to characterize lactation curve patterns across genetic crossbreeding groups, a linear mixed model was fitted to evaluate the effects of genetic group, age, parity, and calving-related covariates on longitudinal milk yield, accounting for random effects associated with parity and temporal variability, and multivariable logistic regression models were used to assess the association between genetic composition and the probability of achieving an average milk yield greater than 10 L per cow per day. Time series analysis and mixed modeling consistently showed higher milk yields for Holstein cows and KiwiCross × Holstein F1 crossbreds, whereas F2 and F3 crossbreds exhibited significantly lower production. Logistic regression indicated that cows with 88% KiwiCross genetics had a markedly reduced odds of achieving average milk yields above 10 L after controlling for parity and calving season. Lactation curve analysis revealed the absence of a defined lactation peak and poor persistency during the first 100 days postpartum across all genetic groups, which could reflect low energy supplementation. Findings highlight the critical interaction between crossbreeding strategy and nutritional management in high tropical grazing dairy systems and provide practical insights to improve productivity in similar production environments.