Replacement of soybean meal with camelina meal in diet of fattening lambs: Influence on feed intake, performance and ruminal fermentation parameters

Abstract

This study evaluated the effects of replacing soybean meal (SBM) with different levels of camelina meal (CM) on feed intake, growth performance, nutrient digestibility, ruminal fermentation, and estimated microbial nitrogen synthesis (EMNS) in fattening Grey Shirazi lambs. Thirty-two lambs (95.0 ± 10.0 days old; body weight of 28.5 ± 1.3 kg) were individually housed for 83 days. Experimental diets were Con (control, diet without CM), CM33 (diet containing 33 % DM of CM instead of SBM), CM66 (diet containing 66 % DM of CM instead of SBM) and CM100 (diet containing 100 % DM of CM instead of SBM). The DM, EE, NDFom, ADFom and ADL contents of CM were higher than in SBM and the ash, CP, NFC and ME contents were lower than those of SBM. There was a tendency for increased dry matter intake (DMI) and final BW in lambs nourished with the CM33 diet compared to the control diet (L = 0.053 and Q = 0.013 respectively). The highest values of gain and average daily gain (ADG) were observed in lambs consuming the CM33 diet (Q = 0.012 and Q = 0.0012). The 66 % CM diet enhanced feed conversion ratio (FCR) (Q = 0.041). Lambs fed the 33 % CM diet exhibited greater DM and OM digestibility than other groups (DM: L = 0.014, Q = 0.028; OM: L = 0.109, Q = 0.028). The pH, total VFA, butyrate, isobutyrate, valerate, and isovalerate levels did not differ between lambs fed SBM and different levels of CM (P > 0.05). No significant variation was detected in ruminal NH₃-N production between lambs fed the CM33 or CM66 diets and those receiving the control diet. Lambs fed the 33 % CM diet showed a trend toward lower ruminal NH₃-N compared to those fed the control diet (L = 0.002, Q = 0.024). In lambs fed the 33 % CM diet, acetate concentration (C = 0.037), acetate:propionate ratio (C = 0.028), and methane production (C = 0.024) decreased, while propionate concentration increased (C = 0.022) compared to the control diet. Lambs receiving the CM33 diet exhibited a higher EMNS than those fed the control diet (Q = 0.038 and C = 0.011). Regarding SMB, CM inclusion at varying levels significantly diminished protozoal counts and subfamilies of Entodiniinae and Diplodiniinae (L < 0.0001). The population of Isotricha (L = 0.011) and the subfamily of Ophrioscolecinae (L = 0.002) decreased only in the CM100 diet compared to the control diet. This study demonstrates that CM can replace SBM up to 100 % of dietary DM in lamb diets without compromising performance, with 33 % inclusion yielding optimal improvements in efficiency and sustainability. These findings, coupled with camelina's agronomic advantages in water-limited conditions, suggest that CM represents a sustainable alternative to SBM in ruminant production systems.