Resumen

LOPEZ ORDAZ, Rufino et al. Optimum level of net energy in feed intake and milk yield at early lactation in Holstein-Friesian cows in confined conditions. Rev. mex. de cienc. pecuarias [online]. 2011, vol.2, n.1, pp.101-115. ISSN 2448-6698.

Optimun level of net energy of lactaction (NE_L, Mcal) in Holstein-Friesian cows under confined conditions was determined based on body weight (BW, kg) changes, dry matter intake (DMI, kg), milk yield (MY), and milk yield efficiency (MYE). Thirty cows (BW = 708.8 ± 26 kg; of second or more lactations) were stratified by BW and randomly assigned to one of three treatments: 1.46, 1.77 and 2.10 Mcal of NE_L/kg DM, for low (LO), medium (ME), and high (HI), respectively, during the first 15 wk of lactation. Dietary energy influenced (P<0.05) on DMI and DMI/100 kg of BW. Cows fed HI and ME levels had 35.0 and 19.3 % higher DMI than the LO treatment (36.8, and 49.4 vs 73.5 kg, respectively); also they had consumed 48.0 and 33.0 % more net energy. In parallel, HI and ME cows had lower BW changes than others (36.80 and 49.40 vs 73.50 kg of BW, respectively); however, we did not found any effects on final BW between ME and HI cows. Cows fed HI level produced 7.0 kg/d more milk than cows fed ME levels and 15.3 kg/d more (P<0.05) than cows fed LO diets; they also were 10.0 % more efficient in the conversion of feed into milk than cows fed ME levels, and 21.0 % more than cows in LO diets. In conclusion, diets containing 1.77 a 2.10 Mcal de EN_L exhibited the most positive milk yield performance and cow's production at early lactation.

Palabras llave : Energy; Milk yield; Body weight.

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