Martínez-Benavides, Javier A.

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    Aclimatación precoz y suplementación dietética con vitamina e y zinc como alternativas para el manejo del estrés calórico en pollos de engorde
    (2008) Martínez-Benavides, Javier A.; Santiago-Anadón, Héctor L.; College of Agricultural Sciences; Latorre Acevedo, José R.; Riquelme Villagrán, Ernesto O.; Department of Animal Science; Román Paoli, Elvin
    The production of broiler chickens in open houses with minimal control of the environment typically takes place in areas of high temperatures causing bird stress and negative effects on the industry. There are diverse procedures to mitigate these effects, such as diet alteration and changes in husbandry practices. Among these alternatives are the early thermal conditioning, the dietary addition of vitamin E and zinc, with the main objective of strengthening the birds immune system in a direct or indirect manner. Experiment 1: The purpose of this investigation was to evaluate the effect of the application of early thermal conditioning (ETC) and the dietary addition of vitamin E and zinc on broiler chicken performance. A total of 600 day-old broilers were raised in a poultry house equipped with 40 floor pens until 42 d of age. A completely randomized design with a factorial arrangement of 2 x 2 x 2 was used where the main effects were: the application of ETC (ETC and without ETC), and the dietary addition of vitamin E (0 and 250 mg/kg) and zinc (0 and 40 mg/kg) for a total of 8 treatments with 5 replicas. The ETC consisted in submitting the birds to a temperature of 41 o C for 6 h at the third d of age. Birds and feed were weighed weekly to determine body weight (BW), feed intake (FI), feed conversion (FC), and mortality. In addition, body temperature (BT) was monitored weekly on 15 birds per treatment measuring the rectal temperature with a digital thermometer. At the end of the rearing period, 25 birds per treatment were randomly selected, slaughtered, and processed to evaluate carcass composition. The yield of hot carcass (HCY), chilled carcass (CCY), breast muscle (BMY), tender muscle (TMY), and fat pad (FPY) expressed as a percentage of live weight. No significant differences among the main effects were found for BW, FI, FC, BT, HCY, CCY, FPY, BMY and TMY. The addition of vitamin E at 250 mg/kg of feed increased bird mortality and reduced carcass FPY. The addition of 250 mg/kg of vitamin E and 40 mg/kg of zinc improved FC of birds when compared to the other treatments, but the differences did not reach statistical significance. In conclusion, the application of ETC, the addition of vitamin E and zinc in the feed at the levels evaluated did not provide any advantages in most of the variables studied. However, the addition of 250 mg/kg of vitamin E and 40 mg/kg of zinc had a positive effect on FC that could justify its commercial utilization. Experiment 2: The purpose of this investigation was to evaluate the most appropriate time for the application of early thermal conditioning (ETC) and its effect on productive performance of broiler chickens raised in a tropical environment. A total of 540 day-old birds were randomly assigned to three treatments and raised until market age (42 d) in an open house with 18 floor pens equipped with tube feeders and nipple drinkers. A completely randomized design with three (3) treatments and six (6) replicas was used in the study. Birds and feed were weighed weekly to determine body weight (BW), feed intake (FI), feed conversion (FC), and mortality. Body temperature (BT) was obtained by measuring the rectal temperature of 18 birds per treatment at the end of each week. At 42 d, a random sample of 36 birds per treatment was chosen for processing and determination of yields and carcass composition. The yield of hot carcass (HCY), chilled carcass (CCY), breast muscle (BMY), tender muscle (TMY), and fat pad (FPY) expressed as a percentage of the birds live weight. No significant differences among treatments were found for BW, FI, FC, BT, HCY , CCY , FPY , BMY , and TMY . The application of ETC at the first d of live resulted in a higher percentage of mortality at the end of the rearing period, while the application of ETC at the third d of life resulted in a lower mortality. In conclusion, the effects on all broiler productive performance parameters except mortality rates were not significantly affected by the application of ETC at any of the days evaluated in this study.