Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2008
Publication Date: 2/1/2009
Citation: Calegare, L., Alencar, M.M., Packer, I.U., Ferrell, C.L., Lanna, D.P. 2009. Cow/calf preweaning efficiency of Nellore and Bos taurus x Bos indicus crosses. Journal of Animal Science. 87(2):740-747.
Interpretive Summary: Objectives of this study were to determine if Bos taurus percentage had an effect on ME requirements and milk production and to compare cow/calf efficiency among three production systems. ME requirements for zero weight change were estimated during pregnancy and lactation in cows representing 0 or 50% Bos taurus breed type. Nellore (NL) cows mated to NL bulls, NL cows mated to Angus (A) bulls, A x NL and Simmental x NL (SNL) cows mated to Canchim (5/8 Charolais, 3/8 Zebu) bulls were used. Increased percentage Bos taurus resulted in increased maintenance requirements during pregnancy and lactation. Maintenance requirements were 9 (NL) to 14% (50% Bos taurus) higher during lactation than during pregnancy. Total ME intake was greater for crossbred cows nursing crossbred calves (4,319 Mcal), than for NL cows with NL (3,484 Mcal) or ANL (3,600 Mcal) calves. The NL cows nursing ANL calves were more efficient than ANL/SNL cows with Canchim sire calves or NL cows with NL calves. Under the conditions of this study, the most efficient pairs capitalized on the low feed costs of the NL cows, and the higher growth potential of the ANL crossbred calves, whereas the least efficient group was straightbred NL (low input/low output).
Technical Abstract: The objectives of this study were to determine if Bos taurus percentage had an effect on ME requirements and milk production, and to compare cow/calf efficiency among three production systems. Metabolizable energy requirements were estimated in a pregnancy and lactation feeding trial for 2 groups of cows, representing 0 and 50% Bos taurus breed type. Nellore cows (NL; 10) mated to Nellore bulls, NL cows (9) mated to Angus bulls, Angus x Nellore (ANL; 10) and Simmental x Nellore (SNL; 10) cows mated to Canchim (5/8 Charolais 3/8 Zebu) bulls were used. Cows were individually fed with a total mixed diet that contained 11.3% CP and 2.23 Mcal ME/kg 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 their body composition estimated using 9-10-11th-rib section to obtain energy deposition. Daily ME intake (MEI) was estimated by regression considering zero BW change. Increase in Bos taurus percentage had a significant effect on daily ME requirements during pregnancy (Mcal•d-1; P < 0.0001) and lactation (P < 0.0001). Bos taurus percentage had a positive linear effect on maintenance requirements of pregnant (P = 0.07) and lactating (P = 0.007) 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 NL and for 50% B. taurus group, respectively. Crossbred cows suckling crossbred calves had greater total MEI (4319 ± 61 Mcal; P < 0.0001) than NL cows suckling NL (3484 ± 86 Mcal) or ANL calves (3600 ± 91 Mcal). Cow/calf gross efficiency was calculated as grams of calf weight gain/Mcal of MEI by cow/calf pair during lactation. The NL cows suckling crossbred calves were more efficient (45.3 ± 1.6 g/Mcal; P = 0.03) than straightbred (35.1 ± 1.5 g/Mcal) and ANL/SNL pairs (41.0 ± 1.0 g/Mcal). In the conditions of this study, the least efficient group was straightbred NL (low input/low output pair) and the most efficient group was represented by the combination of the lower input from NL cows and the higher output from crossbred calves.