Eficiência alimentar em vacas em lactação primíparas e multíparas

Abstract

Food efficiency is understood as the animal's ability to convert ingested food into products and can be affected by different factors related to the animal, diet, and environment. In this context, the objective was to evaluate the feed efficiency of primiparous and multiparous lactating cows in confinement. The experiment was conducted at the experimental farm of Glória of the Federal University of Uberlândia (UFU) in the Dairy Cattle Sector (SEBOL), belonging to the Faculty of Veterinary Medicine and Animal Science (FMVZ).. Fifty-four lactating cows were used, distributed in two batches, housed in confinement on a dirt floor, located 500 meters from the milking parlor. The diet of the animals consisted of corn silage, Tifton 85 grass hay, ground corn, wet brewery residue, and protein concentrate with mineral core and additives. The diet was provided twice a day after the morning and afternoon milking. Dry matter intake was measured by weighing the total diet offered and leftovers, with dry matter content measured in a microwave. On the same day as the intake measurement, individual milk yield was also weighed in the milking parlor at two times, in the morning (7:00 AM) and afternoon (3:30 PM). To determine the gross feed efficiency (GFE) and the feed efficiency corrected for 3.5% fat (FE3.5%F), the following equations were used: GFE = MY/DMI and FE3.5%F = 3.5%F MY/DMI. The 3.5% fat-corrected milk yield (3.5%F MY) was calculated using the equation: 3.5%F MY = Milk Kg0.432 + Fat Kg16.216. For primiparous cows, feed efficiency considering the energy expenditure for growth (FEgrowth) was determined. FEgrowth = 3.5%F MY considering growth/DMI, with 3.5%F MY considering growth = 3.5%F MY + 1.44. The feed efficiency standardized for 150 days in milk (FE150DIM) was also calculated = ((deviation*0.001 + 1). For evaluating milk fat content, milk samples from individual animals were collected and sent to the Milk Clinic (Piracicaba-SP). A completely randomized design with repeated measures over time was used. Treatment means were compared using Tukey's test at a 5% probability level for type I error. The measured variables were also correlated using Pearson's correlation. Multiparous cows had higher dry matter intake, higher milk production, 3.5% fat-corrected milk production, and gross feed efficiency (GFE) compared to primiparous cows (P<0.05). Primiparous cows, even using the equation that corrects for growth energy expenditure, had lower FE3.5% growth compared to multiparous cows (P<0.05). There was a positive and significant correlation (P<0.05) between DMI and MY (r=0.69), between DMI and 3.5% fatcorrected MY (r=0.69), between FE and MY (r=0.71), and between 3.5% fatcorrected MY (r=0.71). However, there was no significant correlation between DMI and gross or growth-corrected FE and 150 DIM (P<0.05), showing that the greatest effect on feed efficiency is from milk production. Multiparous lactating cows have greater feed efficiency compared to primiparous cows due to higher energy requirements for growth.