Abstract
The feeding of Co lactate (Co), an essential oil blend (EO; oregano), or a combination of Co and EO (EOC) may improve nutrient digestion of corn silage-based rations. In four separate studies, Co, EO, or EOC was fed at 0, 4, and 7 g/days to nine rumen fistulated rams arranged in a replicated 3 × 3 Latin square design. The fourth study evaluated the carrier at 0, 4, and 7 g/day. In each ram, fresh ensiled corn silage, leaf, and husk were placed in individual nylon bags inserted through the ruminal cannula and removed after 48 h. Rams fed increasing carrier rates demonstrated similar (P > 0.10) nutrient digestibilities and ruminal pH and volatile fatty acid concentrations. Feeding Co at 4 and 7 g/day increased (P < 0.05) digestibility of DM (59.4, 63.9, and 62.4% for 0, 4, and 7 g/day, respectively), NDF (59.4, 63.9, and 62.4%), and hemicellulose (HC; 56.2, 63.6, and 65.9%) compared with rams fed 0 g/day, while CP digestibility (46.4, 49.9, and 57.8%) was improved (P < 0.05) in rams fed 7 g/day compared with those fed 0 and 4 g/day. Rams fed 4 g/day EO digested greater (P < 0.05) HC (64.1, 71.4, and 69.1%) than rams fed 0 g/day, while rams fed 7 g/day were intermediate and similar (P > 0.10). Rams fed the EOC combination at 4 and 7 g/day demonstrated greater (P < 0.05) digestibilities of DM (57.7, 60.0, and 60.0%), NDF (21.4, 28.8, and 27.7%), and ADF (24.3, 33.3, and 34.4%) than rams fed 0 g/day. The SEM and SM techniques visually demonstrated minor evidence of husk and leaf digestibility in rams across the three experiments when fed 0 g/day of Co, EO, or EOC; rams fed 4 g/day of Co, EO, or EOC exhibited varying visual signs of leaf digestion with some palisade tissue, spongy tissue, and whole vein structure remaining, while in rams fed 7 g/day, only the vein structure remained. Results demonstrated that feeding Co, EO, or EOC at 4 or 7 g/day enhanced ruminal nutrient digestion and fermentation parameters, which was visually confirmed via SEM and SM.
Highlights
China has a large agricultural economy with nearly 400 million ha of grassland, but overgrazing has resulted in significant amounts of confinement feeding using poorly digestible mature forages and crop residues, i.e., corn stalks, straw, etc
Miscommunication/misunderstanding among the coauthors resulted in the need to conduct a later separate experiment evaluating CARR impact on nutrient digestibility and ruminal fermentation
neutral detergent fiber digestibility (NDFD) and HCD increased with 4 g of cobalt lactate (Co), while acid detergent fiber digestibility (ADFD) was similar among all Co inclusion rates, demonstrating that supplementing 4 g was optimal for fiber degradation. These results are similar to the results reported by Liu et al [36] in rabbits demonstrating that daily gain and feed efficiency were improved with a moderate Co inclusion rate, but a larger Co inclusion rate resulted in poorer body weight (BW) gain and feed efficiency
Summary
China has a large agricultural economy with nearly 400 million ha of grassland, but overgrazing has resulted in significant amounts of confinement feeding using poorly digestible mature forages and crop residues, i.e., corn stalks, straw, etc. Various technologies exist to enhance nutrient and fiber digestibility among forage and crop residues having a wide digestibility range, but two promising technologies are feeding cobalt lactate (Co) and essential oils (EOs). Initial EO ruminal fermentation studies demonstrated an inhibition of gas production [10, 11], and later studies reported altered ruminal fermentation by improving protein metabolism, volatile fatty acid (VFA) production, fiber digestion, and microbial community alteration [8, 12, 13], which altered milk composition [14,15,16]
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