Abstract
The specialized herds of the high tropics of Nariño are characterized by semi-intensive breeding models, that is, feeding based on grazing and supplementation. The objective was to analyze the milk production of grazing Holstein cows under conditions of the high tropics, taking into account the energetic and protein metabolites, and their relationship with the dry matter intake (CMS/Kg/d), the body condition (BC), and the reproductive variables. Three periods of lactation were evaluated, thus, between 4-10 days (P1), 45-55 days (P2), and between 185-200 days (P3). The investigation was carried out in four dairy production farms. The forage supply consisted of a mixture of Lolium hybridum, Cenchrus clandestinus Hoschst ex Chiov, Holcus lanatus and Trifolium repens, plus commercial concentrate. A total of 24 Holstein animals (six per productive system) from three births onwards were used, from which blood samples were obtained to determine: non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), triglycerides, cholesterol, glucose, total protein (PT), and blood urea nitrogen (BUN). The results showed that milk production during P1 is influenced by CC and body weight (Kg) by +0.04 liters of milk per unit of change in this variable. In P2, the positive incidence variables were PT, BUN, glucose, NEFA, BHB, triglycerides, and cholesterol, and in P3, the increase in CMS made it possible to show that as lactation progresses in more than 180 days, the animals substantially improve their body condition; likewise the NEFA and BHB indicators are related to a better reproductive response.