02554naa a2200229 a 450000100080000000500110000800800410001902400550006010000240011524500720013926000090021152019040022065000180212470000210214270000170216370000300218070000180221070000190222870000170224770000170226477300430228121334882021-08-12       2020    bl uuuu     u00u1 u    #d7 ahttps://doi.org/ 10.1371/journal.pone.02356192DOI1 aSGUIZZATO, A. L. L.  aEnergy requirements for pregnant dairy cows.h[electronic resource]  c2020  aThis study aimed to estimate energy requirements of pregnant Holstein × Gyr cows. Different planes of nutrition were established by two feeding regimens: ad libitum or maintenance. Sixty-two nonlactating cows with average body weight of 480 ± 10.1 kg and an age of 5 ± 0.5 years were used. Cows were divided into three groups: pregnant (n = 44), non-pregnant (n=12), and baseline reference (n = 6). The 56 pregnant and non-pregnant cows were randomly allocated into a feeding regimen: ad libitum or maintenance. To evaluate the effects of days of pregnancy, pregnant and non-pregnant animals were slaughtered at 140, 200, 240, and 270 days of pregnancy. Energy requirements for maintenance differed between pregnant and non-pregnant cows, thus two equations were developed. Net energy and metabolizable energy requirements for maintenance of non-pregnant cows were 82 kcal/kg empty body weight0.75/day and 132 kcal/kg empty body weight0.75/day, respectively. The efficiency of use of metabolizable energy for maintenance of non-pregnant cows was 62.4%. Net energy and metabolizable energy for maintenance of pregnant cows were 86 kcal/kg empty body weight0.75/day and 137 kcal/kg empty body weight0.75/day, respectively. Efficiency of use of metabolizable energy for maintenance of pregnant cows was 62.5%. The efficiency of use of metabolizable energy for gain was 41.9%. The efficiency of use of metabolizable energy for pregnancy was 14.1%. Furthermore, net energy requirement for pregnancy was different from zero from day 70 of pregnancy onwards. In conclusion, net energy and metabolizable energy requirements for maintenance of non-pregnant cows are different from pregnant cows. Furthermore, we believe that the proposed non-linear equations to estimate net energy requirements for pregnancy are more adequate than current NRC equation, and should be recommended for Holstein × Gyr cows.  aGado Leiteiro1 aMARCONDES, M. I.1 aDIJKSTRA, J.1 aVALADARES FILHO, S. de C.1 aCAMPOS, M. M.1 aMACHADO, F. S.1 aSILVA, B. C.1 aROTTA, P. P.  tPLoS Onegv. 15, n. 7, e0235619, 2020.