Progeny productive performance from different genetic lines of campero-in ta breeding hens

For decades now already in our country, the National Agricultural Technology Institute (INTA, Instituto Nacional de Tecnología Agropecuaria), provides a production backbone of broiler chickens resulting from the crossbreeding of different heavy broiler breeds. The outcome of this process is the so called "Campero-INTA" featured by better production rates than native breeds, although still retaining robustness and adaptability traits of the latter. (Bonino & Canet, 1999).
The existing genetic variations among different commercial heavy broiler breeders can likewise be seen on Campero INTA genetic lines based on the various processes of genetic selection being used (Melnychuk et al., 2004), therefore the technical - productive assessment is justified. In fact, this type of work represents a broad field of research (Finzi, 2000). This work evaluates the productive performance of progeny from two genetic lines of Campero INTA heavy broilers, with the purpose of evaluating the differences between the breeders being used, considering the growth development of its progeny.
Although in broiler chicken production several factors come into play that explain productive performance (feed, health, management, environmental conditions, etc.), the role played by breeding hens in the progeny´s performance must be underscored, since several genetic selection schemes are shown in body weight and livability of newborn chicks. (Arce Menocal et al., 2003).

Experimental trials were conducted in a closed house, divided in 10 sections, 2 sq meters each to hold 20 chickens (10 birds/ sq meter). Productive performance of the progeny coming from two maternal lines, so called E and ES, was analyzed (independent variables), using the same genetic type of male - Campero INTA. A randomized design was used allotting 5 boxes to each experimental group (5 replicates) per treatment.
A comparison was made of chicks hatched on week 31 from breeding hen´s production cycle relative to their productive development starting day 1 until day 42.   Body weight (BW) was recorded at day 1, 7 and 42, whereas feed intake (FI) and feed conversion, although corrected for mortality, were recorded on day 1, 7, and 42.
Throughout the production cycle, commercial balanced feed was supplied ad-libitum in two rations (starter and growing feed). A parametric descriptive statistic was performed to each dependent variable, ordered accordingly to treatments and a variance analysis (VA) was made for a complete random design, evaluating the differences between treatments of dependent variables, considering a 5% significant limit level. (Poole, 1974; Steel & Torrie, 1988).

Average and standard deviation of BW at the beginning and ending of the trial period are shown in Table 1, where significant differences (p<0,05) found for this variable are highlighted at 42 days for chicks coming from Line T.

Table 1. Average and standard deviation of progeny body weight, as per line and age

Means with a common letter are not significantly different (p< 0,05). In the analysis columns comparing treatments are taking into account and not the rows showing it by ages.

Table 2 show results of feed intake by lines, underscoring that line ES showed significant differences at 42 days of the cycle. (p<0,05).

Table 2. Average and standard deviation of feed intake by the progeny, as per line and age.

Finalmente, la conversión alimentaria a los 42 días no presentó diferencias entre origen de línea genética. Estos resultados se presentan en la Tabla 3.

Tabla 3. Promedio y desvío estándar de conversión alimentaria de la progenie, según línea y edad.

Some authors (North, 1993; Gura, 2007) think that there is still enough variability in broiler genetic breeds. Generally speaking, our results reaffirm what has been stated by these authors, since significant variations in body weight and feed intake has been observed by the end of the cycle, which is closely related to the maternal line, although feed conversion did not show significant differences. Coincidentally with our findings, work done at the University of Alberta compared body weight gain of broilers from 4 different breeds (Cobb 500, Avian 24K, Hubbard HiY y Shaver Starbro) were differences were found in body weight of progenies since  day one up until the fourth week of age. Nonetheless from there on and until the end of their life cycle (day 42) such differences were not seen (Thorsteinson, 1999), which means that there are different growth rates associated to the genetic improvement of the various breeds. Neverteheless, in disagreement with our findings, Arce Menocal et al. (2003) underscore that progenies from different breeds have their own growth rates, particularly based on the genetics we are dealing with. For a random design, these authors used 2,800 one-day chicks with a production cycle of 53 days were genetic lines were compared, implementing the same rearing program, taking as response variables body weight, feed intake and feed conversion rates, where no differences were seen between progenies, thus concluding that these differences are not influenced by the type of genetics, and that standardization has been reached in the poultry industry with heavy broilers through genetic improvement.

Despite the duration of the life cycle under study did not allow a BW over 1,200 g, results obtained in feed conversion match those from other authors, who state that slow growing chicken  can reach relatively high body weight values when exceeding 2.500 grams of live weight, the additional feed intake sharply increases feed conversion, generally causing a low feed conversion efficiency (Santomá, 1994). Nonetheless, other existing variables should be taken into account which in some cases justifies higher levels of feed intake and body weight gain, when for example priority is given to produce a regional product with a high value added, given its organoleptic characteristics (issues which entail quality meat).  Context and important variables should be considered such as the rearing system used, consumer´s requirements in the marketplace and the possibility of working with long production cycles (North, 1993; García Marín, 2005). The quality of the finished product (leaner poultry meat with lower percentage of water) are linked to certain genetic type of broilers (generally speaking low growth breeds), reared under  semi closed systems (Silva & Menten, 2002; Hellmeister Filho, 2002; Castelló, 2003; Panno et al., 2004). Based on this principles, some authors (Buxade Carbo, 1988; Almeida & Zuber, 2002) think that the analysis of physical production efficiency should not be solely subject to reach a certain conversion value (although this may be desirable in the beginning) but rather to consider all variables that would eventually determine the best cost - benefit ratio.

Conclusions

Based on results, the crossing of broiler breeder hens which result in Campero broilers show differences in body weight, although the degree of feed efficiency is similar. Furthermore, and since the finished product claim to have different characteristics from those from the poultry industry, there is a high likelihood to achieve appropriate cost - benefit ratios, provided some issues are taken care allowing to reach sufficient amount of production to meet a specific consumer´s market.    
Gratitude

We would like to express our gratitude to Orlando Zlatanoff, Diego Franta and José Maldonado for their support given to this work.

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