Influence of trough versus pasture feeding on average daily gain and carcass characteristics in ruminants: A meta-analysis

Abstract

Quantitative meta-analysis was run on 108 publications featuring 116 experiments and 399 treatments dealing with the effect of trough or pasture feeding environment (FE) on ruminant performances. The objective was to compare the effect of trough or pasture FE on ADG, diet OM digestibility (OMD), various carcass characteristics, and the interaction between FE and complementation modalities. Live weight was adjusted to compare results between species. Results showed that trough-fed animals had higher ADG (+17.89%; P < 0.001), hot carcass yield (HYield; + 2.47%; P < 0.001) and carcass fat content (+ 24.87%; P < 0.001) than pasture-fed animals but lower carcass muscle and bone percentages (-1.60% [P = 0.010] and -7.63% [P = 0.003], respectively). Feeding environment had no effect on diet OMD (P = 0.818), but the number of observations was low. After considering the addition or not of concentrate in the diet (addiCO), FE effect persisted on ADG (P = 0.024) and carcass fat content (P = 0.027) but not on HYield (P = 0.078) or muscle and bone percentages (P = 0.119 and P = 0.581, respectively). After considering the nature of the concentrate (natCO), FE effect persisted on ADG (P < 0.001) and HYield (P = 0.004). Considering the percentage of concentrate in the diet (PCO) erased FE effect on ADG (P = 0.891) and HYield (P = 0.128). In contrast, considering the quantity of concentrate(QCO) erased FE effect on ADG (P = 0.084) but not on HYield (P = 0.006) or on carcass fat and muscle contents (P = 0.040 and P = 0.040, respectively) although the FE effect on carcass bone content persisted (P = 0.550). Animal species and physiological stage had no effect on any of the variables studied (P > 0.05) but experiment did (P ≤ 0.001). The increase in ADG was positively correlated to HYield in cattle (P = 0.002) and small ruminants (P = 0.003) and positively linked to carcass fat content (P = 0.007) but not carcass muscle content, which actually decreased (P = 0.001). Overall, this meta-analysis confirmed previous reports of FE effects and revealed how the differences generally reported result from a confounding effect of FE and nature of the diet. Indeed, in most of the studies used, trough-fed animals were supplemented with concentrate whereas pasture-fed animals were not. This research also highlighted the fact that pasture-fed animals have the potential to achieve the same performances as trough-fed animals when fed a similar diet.