PSVI-1 Additive combinations promoted nutrient metabolic efficiency of calf starter diets.

Abstract Newborn calves are highly vulnerable to pathogenic infections that affect their gastrointestinal and respiratory health. These early-life stressors and inefficiencies limit the metabolic capacity of calves, causing lower digestibility and inefficient nutrient utilization of calf starter feed, ultimately leading to decreased growth performance and immune function. While antibiotics are commonly used for treatment but concerns about antimicrobial resistance have resulted in the FDA regulations that limit their use. The inclusion of natural soluble and palatable additives can promote gut health, stimulate appetite and facilitate the transition to a grain diet. This study hypothesized that commercially produced fermentation products of Lactobacillus acidophilus (RumaCell®), Stand Strong® (SS) and proprietary essential oil blends (EOB) can enhance the metabolic efficiency of calves, improving their ability to utilize grain diets during early rumen development. The study investigated the effects of these RumaCell, EOB and their combination on the in vitro gas production, greenhouse gas emissions, dry matter digestibility and volatile fatty acid (VFA) profile of two calf starter diets (with and without SS). A 24-hour in vitro fermentation procedure was conducted on seven (7) dietary treatments with 8 replicates each, arranged in a completely randomized design. The first 4 treatments contained additives added to starter diets without SS (control, RumaCell, EOB and RumaCell+EOB) while the remaining 3 treatments contained starter diets with SS (SS, RumaCell, and RumaCell+EOB). Data obtained were statistically analyzed using one-way analysis of variance (ANOVA). Results indicated that the inclusion of EOB reduced the total gas and methane gas produced irrespective of feed type. The volume of carbon dioxide was greater (p<0.05) with the addition of RumaCell to SS diet, while the lowest (p<0.05) was obtained with the inclusion of RumaCell and EOB to SS diet. The greatest (p<0.05) DMD was obtained from SS with additives, while the lowest (p<0.05) was recorded with the inclusion of additives to SS diet. Total volatile fatty acids, acetate, butyrate, valerate and iso-valerate were not affected by diet or additives. Propionate concentration was greatest (p<0.05) with the addition of RumaCell and EOB to the control starter, while the acetate:propionate ratio remained unaffected by treatments. It can be concluded that the inclusion of RumaCell and EOB improved the metabolic efficiency of calf starter diets, as evidenced by reduced methane production, changes in dry matter digestibility and shifts in VFA composition that favor improved energy utilization.