Collaboratrices et collaborateurs

Compensatory growth (CG) occurs along refeeding after a period of feed restriction, and is characterized by high feed intake. Aim was to study feeding behavior, enteric methane (CH4) emission and digestibility during CG in beef-on-dairy crossbreeds. Heifers [♀ Brown Swiss × ♂ Angus (AN), Limousin (LI) or Simmental (SI), n=66] were used from 271 to 527 kg body weight (BW). Thirty-three grew discontinuously (DI), 111 d on mountain pasture, followed by refeeding 80 d at barn (65:20:8:7 grass silage/hay/maize silage and concentrates, DM basis). The remaining 33 were fed continuously the barn-diet (CO). Individual intake and feeding behavior were obtained using automatic weighing troughs. Enteric CH4 emission was measured with greenfeed system and digestibility over 5 d using insoluble ashes as indigestible marker. Individual means were computed over refeeding, for ANOVA analysis (package GLM, RStudio 4.1.3) with fixed effects of dietary treatment, crossbreed and their interaction, and pen as random effect. Correlations between variables were explored (package RCORR). During CG, DI had higher DM intake (DMI) than CO heifers (0.025 vs 0.019 kg DMI d-1 kg BW-1, P<0.001) with concomitant increases in meal duration and DMI per meal (P≤0.05). Nevertheless, DI had a lower organic matter digestibility (dMO) than CO (79.8 vs 81.9 %, P<0.05). DI had higher CH4 emission (g d-1 kg BW-1) than CO (P<0.01) but tended to have lower CH4 (g d-1 kg DMI-1) than CO (P<0.1). Compared to LI and SI, AN heifers had higher DMI but lower dMO (P≤0.01). Methane (g d-1 kg BW-1) was higher for AN than LI (P<0.05), but no difference on CH4 (g d-1 kg DMI-1) between crosses (P≥0.1). Methane (g d-1) was positively correlated with DMI and DMI per meal (|r|=+0.60, +0.39, respectively; P≤0.05) and negatively with dMO (|r|=-0.42, P<0.01). The dMO was also negatively correlated with DMI (|r|=-0.50, P<0.001). Such correlations vanished for (P>0.10) when DI and CO groups are considered seperately. This trial highlights broad adaptive processes in feeding behavior, concomitant with increase in feed intake along CG, with further consequences on CH4 emission and digestibility.