Yield and chemical composition of milk of grazing and supplemented Tropical Milking criollo cows

Milk production under grazing conditions is carried out in the intertropical region of hot climates due to its low production cost. The Tropical Milking criollo breed (LT) is characterized by its hardiness in this region, and its high milk quality and cheese yield. Grazing supplementation can increase milk production; however, it can also change its chemical composition. The effect of supplementation with commercial feed in LT cows was evaluated concerning the quantity and physicochemical traits of their milk by lactation. The treatments used were feeding based only on grazing para grass (Brachiaria mutica) and grazing plus 1 kg supplementation with 20 % protein commercial feed for every 5 kg of milk produced daily. The daily milk production per cow increased from 5.82 +/- 0.18 to 7.10 +/- 0.18 kg due to supplementation. Dry matter intake was similar in both treatments. The concentration of fat, protein, lactose, non-fat, and total solids did not suffer modifications (p > 0.05), but the daily production of each component per cow increased in animals supplemented due to the multiplicative effect of the amount of milk. The number of calvings affected milk production, fat, and ureic nitrogen in milk, and somatic cell count (p <= 0.05). It can be concluded that the supplementation used in this study was enough to increase milk production by 22 %, without modifying its chemical composition.