Growth performance, carcass and meat quality, bone strength, and immune response of broilers fed low-calcium diets supplemented with marine mineral complex and phytase.

Influence of marine mineral complex (CeltiCal) as a partial substitute for limestone on growth efficiency, carcass traits, meat quality, bone strength, calcium (Ca) retention, and immune response was investigated in broilers fed low-Ca diets with or without phytase (PHY) addition for a 35-d trial period. A total of 300 one-day-old Ross 308 straight-run broilers were randomly allocated to: T1 (positive control), recommended Ca levels + PHY; T2 (negative control), 0.2% below the recommended Ca levels + PHY; T3, 0.1% below the recommended Ca levels + 0.2% CeltiCal + PHY; T4, 0.2% below the recommended Ca levels + 0.4% CeltiCal + PHY; T5, 0.2% below the recommended Ca levels + 0.4% CeltiCal. PHY was added at 500 phytase units/kg diets. Each dietary treatment had 10 replications of 6 chicks each. Results revealed that production efficiency factor was greater for T4 compared to T2 and T5 during 22-35 d and for T1, T3, and T4 compared to T2 during 0 to 35 d (P < 0.05). Feed conversion ratio was lower for T3 and T4 compared to T2 and T5 during 0 to 35 d (P < 0.05). T4 had a greater (P < 0.05) dressing percentage than T2, which had a lighter (P < 0.01) small intestinal relative weight than all other treatments. Breast meat temperature at 15 min postmortem was highest for T1 and lowest for T3 (P < 0.001). Breast meat pH was greater for T1 compared to T5 at 15 min postmortem and for T3 compared to T4 at 24 h postmortem (P < 0.05). T5 had a lower breast meat redness than all other treatments at 15 min postmortem and then T1 and T3 at 24 h postmortem (P < 0.01). Tibia and femur weights were greater (P < 0.05) for T3, T4, and T5 compared to T2, which had the lowest tibia ash content (P < 0.05) and femur geometric properties (P < 0.001). Greater antibodies to infectious bronchitis virus (P < 0.01) and Ca retention (P < 0.001) were observed for T3 and T4 in comparison to T2. Based on the findings of this research, CeltiCal can adequately replace a considerable portion of limestone in broiler reduced-Ca diets containing PHY.

Adaptation of fuel selection to acute decrease in voluntary energy expenditure is governed by dietary macronutrient composition in mice.

In humans, exercise-induced thermogenesis is a markedly variable component of total energy expenditure, which had been acutely affected worldwide by COVID-19 pandemic-related lockdowns. We hypothesized that dietary macronutrient composition may affect metabolic adaptation/fuel selection in response to an acute decrease in voluntary activity. Using mice fed short-term high-fat diet (HFD) compared to low-fat diet (LFD)-fed mice, we evaluated whole-body fuel utilization by metabolic cages before and 3 days after omitting a voluntary running wheel in the cage. Short-term (24-48 h) HFD was sufficient to increase energy intake, fat oxidation, and decrease carbohydrate oxidation. Running wheel omission did not change energy intake, but resulted in a significant 50% decrease in total activity and a ~20% in energy expenditure in the active phase (night-time), compared to the period with wheel, irrespective of the dietary composition, resulting in significant weight gain. Yet, while in LFD wheel omission significantly decreased active phase fat oxidation, thereby trending to increase respiratory exchange ratio (RER), in HFD it diminished active phase carbohydrate oxidation. In conclusion, acute decrease in voluntary activity resulted in positive energy balance in mice on both diets, and decreased oxidation of the minor energy (macronutrient) fuel source, demonstrating that dietary macronutrient composition determines fuel utilization choices under conditions of acute changes in energetic demand.