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Chantier qualité GA; International audience; This study aimed to compare the growth performances and carcass characteristics of tropical-breed steers reared in 2 contrasted feeding systems (indoor vs. pasture) and slaughtered at different ages (early vs. late). A total of 309 Creole steers (growing at an initial BW of 173 +/- 3 kg and an initial age of 252 +/- 4 d) were used over a continuous 12-yr study. Indoor steers were housed in a cattle shed, fed fresh-cut grass plus concentrate, and slaughtered at 14.5 or 17.1 +/- 0.1 mo of age. Pasture steers were pasture grazed without supplemental feed, and slaughtered at 17.6 and 21.2 +/- 0.1 mo of age. Indoor-fed steers had a greater ADG (786 vs. 517 +/- 29 g.d(-1); P < 0.0001) and more carcass fat (164 vs. 145 +/- 4.5 g.kg(-1); P = 0.001) than pasture-fed steers. Late-slaughtered steers had decreased ADG (630 vs. 673 +/- 27 g.d(-1); P = 0.001) but greater dressing percentages (hot dressing percentage = 55.7 vs. 54.7 +/- 0.34%; chilled dressing percentage = 54.5 vs. 53.4 +/- 0.34%; P < 0.0001) than early-slaughtered steers. The interaction between feeding system and slaughter age was significant for carcass tissue composition. Whole-carcass muscle content was greater in late-slaughtered steers than early-slaughtered steers, especially in pasture-fed steers (720 vs. 698 +/- 6.0 g.kg(-1); P < 0.0001), but less so in indoor-fed steers (707 vs. 700 +/- 5.9 g.kg(-1); P = 0.046). Furthermore, increasing slaughter age had no effect on carcass fat in indoor-fed steers (162 vs. 166 +/- 4.8 g.kg(-1); P = 0.342), but decreased carcass fat in pasture-fed steers (150 vs. 140 +/- 5.0 g.kg(-1); P = 0.014). The results showed that slaughter age and feeding system are 2 major factors that independently affect most of the growth and carcass traits of tropical-breed steers but jointly influence tissue deposition. Our study found that in tropical-breed steers that are grazing, late slaughtering grazing steers increased carcass muscle content without extra fat, thus yielding a carcass quality better suited to consumer choices.

International audience

International audience

International audience

International audience

International audience; Genetic by environment interactions for post weaning traits were studied in a local breed of cattle, well adapted to tropical conditions. After weaning, 444 beef calves of both sexes were separated within two management systems, either in intensive fattening or at pasture. The traits analysed included weights at standard age, of 365 days (W12), 455 days (W15) and 545 days (W18), and post weaning growth rates from weaning until 15 months (PWG15) or 18 months (PWG18). (Co)variance components for all characters were analysed using restricted maximum likelihood (REML) methodology. Different bi-variate animal models were studied, involving separate traits measured one in intensive fattening and the other at pasture. Very low correlations between growth traits obtained in both management systems were observed. These results indicates that there exists an important interaction between genetic merit and environment for post weaning growth traits, and indicate that it may necessary to take into account the real management conditions for the selection on such traits in tropical conditions.

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