Abstract
The aim of this study was to determine the energy metabolism and partition of lactating Gyr and F1 Holstein x Gyr (F1 HxG) cows in different planes of nutrition. Six F1 HxG and six Gyr cows with 130 days in milking (DIM) fed corn silage and concentrate were evaluated. The experiment consisted of four periods with different levels of feeding: 1st ad libitum dry matter intake (DMI) and the others with 5, 10 and 20% restricted DMI, related to the first one. An apparent digestibility assay was performed before measurements in the respiration chamber. Total feces were collected for three days. The cows were confined for 24h in the chamber in each period to determine methane and heat production (HP). F1 HxG had higher gross energy intake (GEI), metabolisable energy intake (MEI) and digestible energy intake (DEI). GE lost in feces was higher in F1 HxG (23.7% GEI) than in Gyr (20.5%) cows. Energy lost as methane and urine was similar between the groups. The metabolisability (q) was 0.67, and the efficiency of converting ME to NE (k) was 0.56. There was no difference in the energy requirements for maintenance between breeds (426.6 MJ/kg BW0,75 average value). The energy requirements for lactation were higher in F1 HxG animals due to the higher volume of milk produced, since there was no difference in energy requirements for production of one kg of milk.
Highlights
Zebus and their crossbreed with Bos taurus animals represent more than 70% of Brazil’s dairy cows
The procedures adopted in this research were approved by the Ethics Committee and Animal Experimentation of the Federal University of Minas Gerais (Permit number 184–2015)
The experiment was conducted at the Metabolism and Calorimetry Laboratory of the Animal Science Department at the Veterinary School of the Federal University of Minas Gerais, located in Belo Horizonte, Brazil
Summary
Zebus and their crossbreed with Bos taurus animals represent more than 70% of Brazil’s dairy cows. The main breed used to cross with Holstein (H) animals is Gyr (G). F1 HxG cows have benefits from heterosis, while combining the main features of each breed. They have good milk production and are adapted to tropical conditions. Zebus and their crossbreeds are the basis of the Brazilian dairy herd, and milk production in Brazil has been increasing. Has been showing a significant increase in milk production.
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