03021naa a2200265 a 450000100080000000500110000800800410001902400310006010000170009124501070010826000090021552022620022465000200248665000160250665000150252265000180253765300150255565300230257065300160259370000220260970000180263170000190264970000200266877300670268814171162023-03-15       2009    bl uuuu     u00u1 u    #d7 a10.2527/jas.2007-07592DOI1 aCALEGARE, L.  aCow/calf preweaning efficiency of Nellore and Bos taurus x Bos indicus crosses.h[electronic resource]  c2009  aThe objectives of this study were to determine if percentage Bos taurus (0 or 50%) of the cow had an effect on ME requirements and milk production, and to compare cow/calf efficiency among 3 mating systems. Metabolizable energy requirements were estimated during a feeding trial that encompassed a gestation and lactation feeding trial for each of 2 groups of cows. Cows were 0 or 50% Bos taurus (100 or 50% Nellore) breed type: Nellore cows (NL; n = 10) mated to Nellore bulls, NL cows (n = 9) mated to Angus bulls, Angus x Nellore (ANL; n = 10) and Simmental x Nellore (SNL; n = 10) cows mated to Canchim (5/8 Charolais 3/8 Zebu) bulls. Cows were individually fed a total mixed diet that contained 11.3% CP and 2.23 Mcal of ME/kg of DM. At 14-d intervals, cows and calves were weighed and the amount of DM was adjusted to keep shrunk BW and BCS of cows constant. Beginning at 38 d of age, corn silage was available to calves ad libitum. Milk production at 42, 98, 126, and 180 d postpartum was measured using the weigh-suckle-weigh technique. At 190 d of age, calves were slaughtered and body composition estimated using 9-10-11th?rib section to obtain energy deposition. Regression of BW change on daily ME intake (MEI) was used to estimate MEI at zero BW change. Increase in percentage Bos taurus had a significant effect on daily ME requirements (Mcal/d) during pregnancy (P &lt 0.01) and lactation (P &lt 0.01). Percentage Bos taurus had a positive linear effect on maintenance requirements of pregnant (P = 0.07) and lactating (P &lt 0.01) cows; during pregnancy, the ME requirements were 91 and 86% of those in lactation (131 ± 3.5 vs. 145 ± 3.4 Mcal·kg?0.75·d?1) for the 0 and 50% B. taurus groups, respectively. The 50% B. taurus cows, ANL and SNL, suckling crossbred calves had greater total MEI (4,319 ± 61 Mcal; P &lt 0.01) than 0% B. taurus cows suckling NL (3,484 ± 86 Mcal) or ANL calves (3,600 ± 91 Mcal). The 0% B. taurus cows suckling ANL calves were more efficient (45.3 ± 1.6 g/Mcal; P = 0.03) than straightbred NL (35.1 ± 1.5 g/Mcal) and ANL or SNL pairs (41.0 ± 1.0 g/Mcal). Under the conditions of this study, crossbreeding improved cow/ calf efficiency and showed an advantage for cows that have lower energy requirements.  aMilk production  aBos indicus  aBos taurus  aGado de corte  aBreed type  aEnergy requirement  aMaintenance1 aALENCAR, M. M. de1 aPACKER, I. U.1 aFERRELL, C. L.1 aLANNA, D. P. D.  tJournal of Animal Sciencegv. 87, n. 2, p. 740-747, feb. 2009.