Data/hora: 08/06/2024 06:45:01

Biblioteca(s): 	Embrapa Gado de Leite.	
Data corrente: 	12/04/2024	
Data da última atualização: 	12/04/2024	
Autoria: 	SACRAMENTO, J. P.; OLIVEIRA, A. S.; LEÃO, A. E.; FONSECA, A. P.; COELHO, S. G.; TOMICH, T. R.; MACHADO, F. S.; FERREIRA, A. L.; CAMPOS, M. M.; SILVI, R. R.; ROWNTREE, J. E.; RODRIGUES, J. R. P.; PEREIRA, L. G. R.	
Afiliação: 	UNIVERSIDADE FEDERAL DE SÃO JOÃO DEL-REI; UNIVERSIDADE FEDERAL DO MATO GROSSO; UNIVERSIDADE FEDERAL DE MINAS GERAIS; UNIVERSIDADE FEDERAL DE MINAS GERAIS; UNIVERSIDADE FEDERAL DE MINAS GERAIS; THIERRY RIBEIRO TOMICH, CNPGL; FERNANDA SAMARINI MACHADO, CNPGL; MARIANA MAGALHAES CAMPOS, CNPGL; UNIVERSIDADE ESTADUAL DE SANTA CRUZ; MICHIGAN STATE UNIVERSITY; UNIVERSIDADE FEDERAL RURAL DO RIO DE JANEIRO; LUIZ GUSTAVO RIBEIRO PEREIRA, CNPGL.	
Título: 	Energy requirement for primiparous Holstein × Gyr crossbred dairy cows.	
Ano de publicação: 	2024	
Fonte/Imprenta: 	Journal of Dairy Science, 2024.	
DOI: 	https://doi.org/10.3168/jds.2023-24393	
Idioma: 	Inglês	
Conteúdo: 	Our objective was to estimate the requirements of metabolizable energy (ME) and net energy for the maintenance (NEm) of lactating and dry cows, the efficiency of ME utilization for milk production (kl) and tissue gain (kg), and the use of body energy mobilization for milk production (kt) throughout the lactation of primiparous crossbred Holstein × Gyr cows, using open-circuit respiration chambers. Twenty-nine primiparous Holstein × Gyr crossbred cows with an initial BW averaging 563 ± 40.1 kg and 2.5 ± 0.09 years old were used throughout lactation and dry periods. The cows were kept non-pregnant throughout the study to eliminate possible confounding factors. Apparent digestibility assays, followed by calorimeter measurements, were performed 6 times throughout the lactation period. In the dry-off period, the cows were also evaluated but fed with restricted intake (DMI = 1.1% BW/d) to achieve heat production close to maintenance. After 21 d of diet adaptation, an apparent digestibility assay followed by calorimeter measurements was performed. Parameter estimates for lactation period were obtained by mixed models including lactation stage as repeated measures. For restricted feeding at dry-off and fasting period assays, the requirements were estimated by exponential regression. For whole lactation, the values of MEm and NEm were 0.588 and 0.395 MJ/BW0.75, respectively. The efficiencies kl kg kt were 0.672, 0.771, and 0.814, respectively. However, MEm and NEm were higher in early and mid-lactation than late, while kl was higher in early than other lactation stages. Dry and non-pregnant cows had MEm of 0.434 MJ/BW0.75 and NEm of 0.351 MJ/BW0.75 for maintenance level, and MEm of 0.396 MJ/BW0.75 and NEm of 0.345 MJ/BW0.75 for fasting metabolism level and efficiency of ME utilization for maintenance was 0.80. Our findings confirmed that F1 crossbred Holstein × Gyr dairy cows have differences in energy requirement and efficiency throughout the lactation stages, suggesting the use of different values in each stage. The estimated values of energy requirement for maintenance and efficiencies for primiparous lactating crossbred Holstein × Gyr were similar to those reported in the literature in specific studies and requirements systems. Keywords: efficiency, maintenance, metabolizable energy, net energy.	
Thesagro: 	Gado Gir; Gado Holandês; Gado Leiteiro.	
Categoria do assunto: 	L Ciência Animal e Produtos de Origem Animal	
Registro original: 	Embrapa Gado de Leite (CNPGL)	
Exemplares: 	CNPGL - (26312-1) - UPC - AP - DD -  -  -  - DIS