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      Effect of dietary energy and stocking density on the performance and sensible heat loss of broilers reared under tropical winter conditions

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          Abstract

          The objective of the present study was to evaluate the effects of different dietary energy levels and stocking densities on the thermoregulating parameters, live performance, and carcass traits of broilers reared under tropical winter conditions at different times of the day. In total, 1,312 one-d-old male broilers were used. Birds were allotted to three different stocking densities (10, 14 or 18 birds/m²) and two dietary energy levels (2900 or 3200 kcal ME/kg). The following parameters were evaluated:radiant heat load (RHL), rectal temperature (RT), feed intake (FI), weight gain (WG), feed conversion ratio (FCR), livability (L), production of live weight per area (WA), and carcass yield. Stocking density did not affect sensible heat loss (SRL) or rectal temperature (RT); however, as expected, sensible heat loss (SRL) and RT were influenced by time of the day, with higher values in the morning and in the afternoon, respectively. There was no effect of treatment (p>0.05) on carcass or parts yield. Feed intake was reduced in 3%, whereas weight gain and feed conversion ratio improved in 8 and 10%, respectively, as dietary energy level increased. On the other hand, stocking density did not influence live performance or carcass traits. Based on the present results, it is concluded that sensible heat loss depends on dietary energy levels and particularly on time of the day. Therefore, environmental house management is suggested during tropical winters in order to reduce differences between broiler skin and environmental temperatures in the morning and in the afternoon.

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          Carcass composition and yield of 1957 versus 2001 broilers when fed representative 1957 and 2001 broiler diets.

          The yield of carcass parts as well as levels of carcass fat, moisture, and ash were measured in the 1957 Athens-Canadian Randombred Control (ACRBC) and in the Ross 308 commercial broiler, when fed diets that were representative of those being fed during 1957 and 2001. The Ross 308 was used to represent 2001 commercial broilers. Comparisons of carcass weights of the Ross 308 on the 2001 diet versus the ACRBC on the 1957 diet showed they were 6.0, 5.9, 5.2, and 4.6 times heavier than the ACRBC at 43, 57, 71, and 85 d of age, respectively. Yields of hot carcass without giblets (fat pad included) were 12.3, 13.6, 12.2, and 11.1 percentage points higher for the Ross 308 than for the ACRBC at those ages. The yields of total breast meat for the Ross 308 were 20.0, 21.3, 21.9, and 22.2% and were 8.4, 9.9, 10.3, and 9.8 percentage points higher than for the ACRBC at those ages. Yields of saddle and legs for the Ross 308 broiler were approximately 31 to 32% over the four ages and were about 1.5 to 2% higher than for the ACRBC at the different ages. The Ross 308 averaged 13.7, 15.0, 18.6, and 18.5% whole carcass fat versus 8.5, 10.6, 12.7, and 14.0% for the ACRBC at the four ages. In conjunction with previous studies, the current data show that yield of broiler carcass parts has continued to increase over time and that genetics has been the major contributor to changes in yield.
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            Growth, livability, and feed conversion of 1957 versus 2001 broilers when fed representative 1957 and 2001 broiler diets

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              Density allowances for broilers: where to set the limits?

              I Estevez (2007)
              Stocking density has critical implications for the broiler industry because higher returns can be obtained as the number of birds per unit space increases. Assigned densities have been primarily driven by cost-benefit analysis, but economic profit may come at the cost of reduced bird performance, health, and welfare if densities are excessive. These negative consequences are the primary reason for the increasing demands for guidelines that limit density allowances, even through legislation. Current recommended densities are rather variable, and therefore it is critical if guidelines are to be established that they be based on sound science. Published research consistently indicates that the health and welfare of broilers is compromised if space allowances drop below 0.0625 to 0.07 m2/bird (equivalent to about 34 to 38 kg/m2 depending on final BW). Negative consequences include reduced final BW, feed intake and food conversion, and greater incidence of foot-pad dermatitis, scratches, bruising, poorer feathering, and condemnations. A few studies have also found higher mortalities, tibial dischondroplasia, and some evidence of physiological stress. At the behavioral level, most studies indicate a reduction in space use and movement and higher frequencies of disturbances, which has been linked with a higher frequency of scratches and decline in carcass quality. Other main behavioral categories remain largely unchanged. However, results overwhelmingly suggest that while stocking density has major consequences for the health and welfare of broilers, the quality of the environment, which has been largely underestimated, is far more relevant. Advances in broiler welfare will be difficult to achieve unless some criteria for environmental quality are also established. The implications of this are that the welfare of broilers can be ensured at a range of (reasonable) densities, as long as the requirements for environmental quality are fulfilled. It is also essential for industry to realize that returns per unit of space in broiler production do tend to plateau if density is excessive, a result of the reduction in bird performance. In this paper I suggest a model that may be used to maximize productivity, health, and welfare.
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                Author and article information

                Journal
                rbca
                Brazilian Journal of Poultry Science
                Braz. J. Poult. Sci.
                Fundação APINCO de Ciência e Tecnologia Avícolas (Campinas, SP, Brazil )
                1516-635X
                1806-9061
                March 2013
                : 15
                : 1
                : 53-57
                Affiliations
                [01] São Paulo orgnameUNESP orgdiv1Faculdade de CiênciasAgrárias e Veterinárias orgdiv2Department of Animal Morphology and Physiology Brazil
                Article
                S1516-635X2013000100009 S1516-635X(13)01500100009
                10.1590/S1516-635X2013000100009
                ff037656-ce0c-481b-8c87-978472fd44b5

                This work is licensed under a Creative Commons Attribution 4.0 International License.

                History
                : January 2013
                : November 2012
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 22, Pages: 5
                Product

                SciELO Brazil


                production capacity,Housing environment,radiation,broiler,sensible heat

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