Effects of sex and genotype on performance and yield characteristics of free range broiler chickens

Abstract

The purpose of this work was to evaluate the effect of genotype and sex on the performance characteristics (weight gain, feed conversion and livability) and yields (carcass, breast and legs) of six free-range genotypes: Pesadão Vermelho (GEN1), Carijó (GEN2), Pescoço Pelado 1 (GEN3), Pescoço Pelado 2 (GEN4), Pescoço Pelado 3 (GEN5) and Pescoço Pelado 4 (GEN6). A total of 1584 sexed one day old chicks (792 males and 792 females) were housed in 48 pens, 33 birds per pen. The experimental design was a completely randomized factorial 2 x 6 (six genotypes and two sexes) design, with four replicates each. Diets were based on corn and soybean meal (no animal protein) provided in a feeding program in four phases: pre-starter (1 to 21 days), starter (22 to 42 days), growth (43 to 77 days) and finisher (78 to 91 days). Feed intake, feed conversion and livability were measured at 21, 42, 77 and 91 days of age. There was no genotype x sex interaction. The effect of sex was observed in all ages regarding weight gain, feed conversion (except at 21 days) and yields. For all these characteristics, males performed better than females, except in breast yield, which was higher in females. For the livability and feed conversion at 21 days no effect of sex was found. The effect of genotype was observed only in carcass and breast yields. The fast (GEN1) and intermediate (GEN2, GEN5 and GEN6) growing genotypes showed higher weight gain than the slow growing genotypes (GEN4 and GEN3). Carcass and breast yields of naked neck genotypes (GEN3, GEN4, GEN5 and GEN6) did not differ among themselves, and were higher than the Carijó genotype (GEN2) and are therefore recommended for production systems that sell industrialized birds.Keywords: alternative aviculture, genotype, performance, yields RESUMO A realização deste trabalho buscou avaliar o efeito de genótipo, sexo e sua interação sobre as características de desempenho (ganho de peso, conversão alimentar e viabilidade) e de rendimento (carcaça, peito e pernas) de seis genótipos de frango de corte tipo caipira: Pesadão Vermelho (GEN1), Carijó (GEN2), Pescoço Pelado 1 (GEN3), Pescoço Pelado 2 (GEN4), Pescoço Pelado 3 (GEN5) e Pescoço Pelado 4 (GEN6). Foram utilizados 1584 pintinhos sexados (792 machos e 792 fêmeas), alojados em 48 boxes, sendo 33 aves por boxe. O delineamento experimental foi o inteiramente ao acaso, em esquema fatorial 6 x 2 (seis genótipos e dois sexos), com quatro repetições cada, sendo cada boxe considerado uma unidade experimental. As rações à base de milho e farelo de soja (sem proteínas de origem animal) foram fornecidas em um programa de alimentação de quatro fases:pré-inicial (um a 21 dias), inicial (22 a 42 dias), crescimento (43 a 77 dias) e abate (78 dias até o abate

Effect of the supplementation of biocomplexed minerals in diets for free-range chickens on performance and carcass characteristics

“…In a great part of the works in the literature, males presented higher values of live weight (Mitrovic et al, 2011;Sarica et al, 2014;Cruz et al, 2018) and carcass yield (Del Castilho et al, 2013), which is in agreement with the results observed in the present study. This behavior is related to sexual dimorphism, in which males present a higher growth potential, with greater muscle deposition capacity due to the synthesis of androgen hormones, responsible for protein anabolism, in addition to better developed bone structure (Rondelli et al, 2003).…”

“…Regarding the feed conversion index, males presented better values throughout the production period (1 to 90 days), which indicates that they are more efficient in converting the consumed feed into weight gain. This result is in agreement with those of Santos et al (2005), Faria et al (2011), andDel Castilho et al (2013), who observed better indices of feed conversion for males.…”

“…The results of the present study are in agreement with those of Santos et al (2005), Faria et al (2011), andDel Castilho et al (2013), who observed higher average weight gain for males, and with Santos et al (2005) and Dourado et al (2009), in which males presented higher values of feed intake.…”

“…The fact of that females present higher mean of breast yield and males higher thigh yield and drumstick weight may be related to the effect of sexual dimorphism, and this behavior has been observed in other studies (Dourado et al, 2009;Faria et al, 2011;Del Castilho et al, 2013;Sarica et al, 2014;Cruz et al, 2018). Males presented greater development of the secondary parts of the carcass, such as wing, back, head plus neck, and feet.…”

Growth curves of different free-range chicken lineages by the Gompertz model

“…Alternative production has as a principle the concern for animal welfare since birds conditioned in a semi-intensive system can express their natural behaviors, such as scratch and spreading their wings, which reduces the stress of these animals (Aksoy et al, 2021). This trend has been accompanied by an evolution in the field of genetics, with the emergence of several free-range chicken lineages encompassing characteristics like hardiness and elevated production indices (Del Castilho et al, 2013). However, varying information can be found regarding body growth between these different lineages (Cruz et al, 2018;Ribeiro et al, 2020).…”