Eficiência alimentar de vacas em lactação primíparas e multíparas criadas em sistema de compost barn

Abstract

Feed efficiency in dairy cows was defined as the ability to convert consumed feed into milk, which could be influenced by various factors related to the animal, diet, and environment. The aim of the experiment was to evaluate feed efficiency in primiparous and multiparous cows. The study was conducted at the Glória Experimental Farm of the Universidade Federal de Uberlândia (UFU), in the Dairy Cattle Sector (SEBOL) of the Faculdade de Medicina Veterinária e Zootecnia (FMVZ). A total of 46 cows were used, divided into two groups: 19 primiparous and 27 multiparous. The animals’ diet was provided twice a day after milking and consisted of corn silage, protein concentrate, ground corn, wet brewery waste (barley), cottonseed, and Tifton 85 grass hay. Dry matter intake and milk production were measured daily during the experimental period. For the determination of gross feed efficiency (GFE) and feed efficiency corrected for 3.5% fat, the following equations were used: EAB = PL/CMS and EA3.5%G = PLCG3.5%/CMS. The milk production corrected for 3.5% fat (PLCG3.5) was calculated using the equation: PLCG3.5% = Kg Milk * 0.432 + Kg fat * 16.216. For primiparous cows, feed efficiency was determined considering the energy expenditure for growth (EAcresc), where EAcresc = PLCG3.5% considering growth / CMS, and PLCG3.5% considering growth = PLCG3.5% + 1.44. Feed efficiency standardized for 150 days in lactation (EA150del) was calculated as (deviation * 0.001 + 1). To obtain the milk fat content, individual milk samples were collected from the animals and sent to the Clínica do Leite in Piracicaba-SP. The design used was a completely randomized design with repeated measures over time. The treatment means were analyzed with respect to the assumptions of normality and homogeneity of variances. For the variables that met these assumptions, analysis of variance was performed, followed by a mean comparison test at a 5% significance level for type I error. Primiparous cows consumed less dry matter, ash, and crude protein than multiparous cows (P<0.05). Primiparous cows selected in favor of ash and crude protein (P<0.05). Despite producing less milk, primiparous cows showed greater feed efficiency when corrections for fat, growth, and days in milk were considered (P<0.05). Primiparous cows exhibit higher feed efficiency when milk production is corrected for fat, growth, and days in milk, since they select more nutrients from the offered diet.