Evaluation of the productive performance and corporal composition of two genotypes of campero-inta birds

In the early 90s the Poultry Section of the EEA-Pergamino at INTA had the traditional races to make crosses and to get broilers and self-sexing layer hens, but the focus was setting the basis for a population of birds for a less intense productive system.  These birds were called free-ranging broilers and their exploitation was focused on a non-traditional poultry system and on a search for a differentiated product. Colored animals were selected from the base population to differentiate them from the commercial birds and paternal and maternal strains were created to come to a broiler cross. The meat of the free-ranging broiler should be firm and with a pronounced flavor, which is achieved by growing birds genetically different from those grown in standard sites (slow-growth strains)  and with a slaughter age of at least 81 days (Sauveur, 1997).
In 1999 the first program for improving this population was developed based on a pyramid type structure.  In order to get the response from a selection similar to the estimated one, it is critical to know the genetic and phenotypic parameters of economic importance, which will also be used for the prediction of the value of the breeding. Both the final live weight, as well as the in feed intake during the breeding, will contribute to a greater benefit for the grower in terms of income increase and production costs reduction, which has been established by estimating the corresponding economic values (Melo et al., 2003).
Less corporal fat will result in a greater efficiency of the production system, due to savings in the feed costs and higher carcass yield. The abdominal fat pad is a good indicator of the total body fat of the bird (Delpech & Ricard,1965) and it accounts for around 3,5% of the live weight and 15% of the total fat.
The degree of heterosis is expressed in birds resulting from various crosses and it is variable depending on the populations used for the crossing.  In order to justify the crossings, the productive performance of the offspring must be higher than that of the paternal populations.
The objective of this paper was to evaluate the productive response and body composition (live weight, weight gain, feed intake, feed conversion, abdominal fat pad weight, breast weight and the ratio of the latter in connection to the live weight) of two types of birds used for crossings, obtained from different Campero-INTA paternal populations.  

224 Campero-INTA Cross E (with lighter paternal line) genotype birds and 224 Campero-INTA Cross H (with heavier paternal line) genotype birds of two genders were used. The animals were placed in the experimental unit of Genetics of the School of Veterinarian Sciences of the Buenos Aires University. All birds were raised together until day 65 of age under similar conditions of temperature, humidity and management as it done in a regular setting. All animals received the same diet: Pre-starter 0-21 days (PC: 20%, EE: 5,0%), starter 22-47 days (PC: 19%, EE: 5%) and finisher 48-65 days (PC: 18%, EE: 5,0%). Birds were evaluated by two experiments. The first evaluation took place from days 10 to 51 of age, by randomly distributing the chicks by block (side) in 32 5-m² pens, in a Fully Randomized Block Design (FRBD).  The second evaluation took place from days 52 to 65, with a random re-distribution of sexed birds by block (side) in 32 pens in a FRBD. The new distribution was 8 pens per each sex and genotype. The individual live weight of chicks was recorded upon arrival and also at days 10 and every 14 days.  In order to evaluate the feed intake rate, a supply and reject method was used, by measuring feed intake together with each bird's weight, in order to analyze feed conversion rates (feed intake/weight gain).  On day 65, 2 birds per pen were selected randomly for an experimental slaughter in accordance to the regular procedure for commercial slaughter and dissection of abdominal fat pad according to a described technique (Delpech & Ricard, 1965). The abdominal fat pad weight (AFPW) and breast weight (BW) were recorded. The abdominal fat pad ratio was estimated as the AFPW/LW and the breast weight ratio (BWR) as BW/LW. For the statistical analysis, each pen was considered as an experimental unit for the live weight, weight gain, feed intake and feed conversion variables. The slaughter data were analyzed considering each bird as an experimental unit. To analyze the data, a variance analysis was made for a FRBD.  The model of analysis included the fixed effect of the block (side of house) and the fixed effect of the genotype, including the fixed effect of sex on the second experiment. In all cases, the INFOSTAT^® software was used.

In the experiment where birds were not sexed, the live weight was higher (p<0,05) at days 24 and 38 of age among Cross H, as well as weight gain during days of age 11 and 24 (p<0,05). No significant differences (p>0,05) were observed in live weight measurements at days of age 10 and 51, nor in weight gain, feed intake and feed conversion in the remaining periods of the first experiment (Table1).

Table 1. Average of live weight (LW), weight gain (WG), feed intake (FI) and Conversion (CV) of the first experiment (10 - 51 days of age) for each cross

In the second experiment, animals showed significant differences (p<0,05) in live weight at days of age 52 and 65 and in weight gain between those ages. No significant differences (p>0,05) were observed in feed intake and feed conversion variables. Live weight was higher (p<0,05), and so weight gain and feed intake of males, while feed conversion was higher (p<0,05) in females (Table 2).

Table 2. Average of live weight (LW), weight gain (WG), feed intake (Cons) y conversion (CV) of the second experience (52 - 65 days of age) for each cross and sex

In the measurements made during the experimental slaughter, the abdominal fat pad weight, fat ratio and breast weight were higher (p<0,05) in Cross H; no significant differences (p>0,05) were observed in the breast ratio. The effect of sex was significant (p<0,05) for the breast weight and for the fat ratio. No significant differences (p>0,05) were observed in the breast ratio measurements. (Table 3)

Table 3. Average of abdominal fat weight (AFW), breast weight (BW), abdominal fat pad ratio (AFPR) and breast ratio (BR) at 65 days of age for each cross and sex

Under the conditions of these experiments, it was observed that in the early development stages (10 - 24 days), as well as at later stages (52 - 65 days), Cross H would have a higher growth rate than Cross E. However, the greatest weight gain in Cross H, was not achieved with higher efficiency, as there were no significant differences in the conversion feed and Cross E showed a lower abdominal fat pad ratio, which represents a more efficient tissue deposition in this cross. The greater abdominal fat pad ratio expressed in Cross H also represents an undesirable characteristic for this type of birds.

Delpech P & Ricard F. 1965. Relation entre les depots adipeux visceraux et les lipides corporels chez le poulet. Ann.Zootech. 14(2):181-189.

Melo JE, Pruzzo L, Cortes Rondan F, Morao L, Canet Z, Miquel MC. 2003. Economic values of traits used in selection of a free-range broiler strain. Proc. IX World Congress on Animal Production, Ed. Digital.

Sauveur B. 1997. Les critères et facteurs de la qualité des poulets Label Rouge. INRA Prod. Anim. 10:219-226.