Variation of milk ureic nitrogen according to season and days in milk

Objective. Determine the variation of MUN according to the seasons of the year (rainy and dry season) and the days in milk (DIM) of dairy cows from two herds in the Boyacá highlands of Colombia. Materials and methods. A descriptive quantitative study was carried out for convenience. 4,901 milk samples were included from 112 animals located at a height of 2,600 meters above sea level during a period of 24 months, grouping the samples according to the season and the days in milk production. The samples were processed through a spectrophotometric enzymatic methodology for the determination of MUN. An analysis of variance was carried out for the groups by climatic season, while for the days in milk a quantitative description was made. Results. The MUN varied according to the season of the year (p<0.05), the values being higher during the rainy season. The MUN was lower during the first 60 DIM in most of the conformed groups and the peaks appeared from 180 DIM. The lowest MUN values according to the days in milk were determined in the first 60 days in most of the conformed groups, likewise, the main peaks were determined from 180 DIM. Conclusions. The MUN varied according to the season, being higher in rains, the MUN was lower during the first 60 DIM in most of the groups formed and the peaks appeared from 180 DIM