Objective: This study aimed to evaluate the effect of the ad libitum and restricted feeding regimen on fasting heat production (FHP) and body composition.Methods: Twelve Hubbard broilers breeders were selected with the same body weight and submitted in two feeding regimes: Restricted (T1) with feed intake of 150 g/bird/d and ad libitum (T2). The birds were randomly distributed on the treatments in two runs with three replications per treatment (per run). The birds were adapted to the feed regimens for ten days. After that, they were allocated in the open-circuit chambers and kept for three days for adaptation. On the last day, oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured by 30 h under fasting. The respiratory quotient (RQ) was calculated as the VCO2/VO2 ratio, and the heat production (HP) was obtained using the Brower equation (1985). The FHP was estimated throughout the plateau of HP 12 hours after the feed deprivation. The body composition was analyzed by dual-energy X-ray absorptiometry scanning at the end of each period. Data were analyzed for one-way analysis of variance using the Minitab software.Results: The daily feed intake was 30 g higher to T2 (p<0.01) than the T1. Also, the birds of the T2 had significatively (p<0.05) more oxygen consumption (+3.1 L/kg0.75/d) and CO2 production (+2.2 L/kg0.75/d). That resulted in a higher FHP 359±14 kJ/kg0.75/d for T2 than T1 296±17.23 kJ/kg0.75/d. In contrast, the RQ was not different between treatments, with an average of 0.77 for the fasting condition. In addition, protein and fat composition were not affected by the treatment, while a tendency (p<0.1) was shown to higher bone mineral content on the T1.Conclusion: The birds under ad libitum feeding had a higher maintenance energy requirement but their body composition was not affected compared to restricted feeding.
The objective of this study was to evaluate the health status, productive performance and carcass traits of growing rabbits housed in pen with litter and conventional cage. At 35 d, 54 crossbred rabbits (New Zealand White vs. Botucatu) were randomly housed in pen with litter (6 pens, 6 rabbits/pen, 2.3 rabbits/m²) or cage (6 cages, 3 rabbits/cage, 8.3 rabbits/m²) and kept until the age of slaughter at 77 d. To simulate farm conditions, the rabbits that were housed in pen have not been previously adapted to this system. There was greater intensity of dirt and mucus occurrence in the rabbits housed in pens in first period, but the mucus occurrence practically disappeared in the later period. For performance, the rabbits housed in cages had a higher live weight at 56 d (1714 vs. 1506 g; P<0.001), as well as BWG (46.4 vs. 36.7 g/d, P<0.001) and better FC (2.75 vs. 3.33; P<0.05) from 35 to 56 d. However, these animals did not show the best performance (P>0.05) in the posterior period (56 to 77 d). There was no effect (P>0.05) of housing system for carcass yield, dissectible fat and hind leg yield. It may be suggested that rabbits adapt to the floor over time. Therefore, it is indicated the adoption of this system for growing rabbits.
Indirect calorimetry (IC) is a widely used method to study animal energy metabolism by measuring gas exchange. The accuracy of IC depends on detecting variations in signals reflecting the metabolic response, which can be challenging due to measurement noise and external factors. In this study, we propose a methodology to validate IC systems, including an easy-to-use spreadsheet for data computing, to verify accuracy and detect whole-system leaks. We conducted a re-covery test using a simulation of CO2 dynamics in MS Excel and injecting a known CO2 concentration into four respirometry chambers. The clearance rate of CO2 was observed and compared to the expected clearance rate from the simulation. The results from the recovery test in our system show that the proposed methodology is accurate and precise. The proposed methodology and recovery test can be used to standardize the validation of IC systems, providing accurate measurements of animal energy metabolism in different environmental conditions and energy utilization from feeds.
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