J APPL POULT RES 2006. 15:579-583
© 2006 Poultry Science Association
Influence of the Laying Date on the Fertility and Hatchability of Red-Legged Partridge (Alectoris rufa) Eggs
P. González-Redondo1
Departamento de Ciencias Agroforestales, Escuela Universitaria de Ingeniería Técnica Agrícola, Universidad de Sevilla, 41013 Sevilla, Spain
1 Corresponding author: pedro{at}us.es
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SUMMARY
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In several countries, there is a well-developed market for Red-Legged partridge (Alectoris rufa) eggs for incubation. Although Red-Legged partridge eggs produced at game farms are sold with a guaranteed average hatchability, there is a marked seasonal variation in fertility and hatchability. Therefore, an average incubating hatchability value cannot be generalized across the whole breeding season. In this research, the influence that the laying date has upon the fertility and hatchability of incubated eggs and the hatchability of the fertile eggs incubated at a farm of Red-Legged partridge was analyzed. It was found that the laying date did indeed influence the fertility and hatchability of the incubated eggs. Fertility and hatchability were greater in the eggs set in the incubator between mid February and late March than those of the eggs set in late April and early May. Hatchability of fertile eggs was greater in the eggs set in the incubator in mid March and lower in the eggs set in late April. The higher values obtained during the middle of the laying period and the lower ones obtained at the end of the laying period cause the game farms’ need to inform their potential customers of the eggs’ expected hatchability as a function of their laying date.
Key Words: Red-Legged partridge • Alectoris rufa • incubation • hatchability • fertility
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DESCRIPTION OF PROBLEM
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The Red-Legged partridge (Alectoris rufa) is a game species raised in farms in countries such as Spain, France, Portugal, England, Italy, and others, with their hatching eggs being one of the commercial products of such game farms. These eggs are sold with a guaranteed average hatchability, something well known to the breeders by their previous experience [1]. In spite of the fact that there is a well-established market for hatching eggs, there are a lack of studies concerning the Red-Legged partridge eggs’ fertility and hatchability on game farms. The Red-Legged partridge’s reproductive performance varies greatly due to its remarkable reproductive seasonality, this being more intense under a natural photoperiod [2, 3] than under artificial photoperiod supplementation [2, 4]. The reproductive performance also varies in relation to the different production systems used, varying from the more intense systems in which breeding occurs in flat-deck cages [2, 3] to the less intensive large-pen systems [5, 6]. To fully inform breeders and game managers buying eggs for incubation, reference values of the fertility and hatchability of farm-laid Red-Legged partridge eggs are necessary. The aim of the present study was to measure and report the fertility and hatchability values of the Red-Legged partridge eggs, paying special attention to the differences observed due to laying date.
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MATERIALS AND METHODS
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A total of 4,710 incubated eggs from a Red-Legged partridge farm in La Roda (province of Seville; Southern Spain) were used. The breeding partridges, with ages ranging from 1 to 4 yr old, were fed with commercial feed (20% CP) and were lodged in pairs in outdoor cages measuring 40 x 110 cm. The partridges were initially subjected to natural lighting, but from December 1st, when the photoperiod was 10 h of light, artificial lighting was added, increasing the photoperiod by 0.5 h in wk 1 and 1.5 h during each of the successive weeks until the first week of January, when a complete photoperiod (natural light + artificial light) of 16 h of light was reached. This lighting program was maintained until May 8th, when artificial light was removed because the partridges’ laying rate significantly declined. Egg laying commenced during the first week of January. From January 15th onward, the eggs were collected on a daily basis and were kept at 12°C and 80% RH. Twelve hours before being loaded in the incubator, the eggs were prewarmed at 22 to 24°C by maintaining them in the room where the incubator itself was located. Loading of the eggs into the incubator was done on the following dates of the same year: batch 1, January 31st; batch 2, February 14th; batch 3, February 28th; batch 4, March 13th; batch 5, March 27th; batch 6, April 10th; batch 7, April 24th; and batch 8, May 8th. In each new batch, all of the hatching eggs laid by the partridges since the date of the previous incubator loading were incubated. This prolonged storage time occurs frequently in small-scale Red-Legged partridge farming [5] and usually does not have any negative effects upon the Alectoris species eggs hatchability [7]. The eggs were incubated at 37.8°C and 55% RH. After the 24-d incubation period, the number of hatched chicks and unhatched eggs was recorded. Non-hatched eggs were analyzed via breakout examination to determine their fertility [8].
Statistical differences in the fertility and hatchability of the incubated eggs and the hatch-ability of the fertile eggs were analyzed using contingency tables on which Pearson’s 
2 tests were performed, and the standardized residuals were calculated. In the interpretation of the standardized residuals, 1.96 was considered to be the discriminant value for a confidence level of 95%. A regression analysis was performed to describe the link between hatchability of the incubated eggs and fertility. The analyses were conducted using SPSS 9.0 software [9].
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RESULTS AND DISCUSSION
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The number of incubated eggs, fertile eggs, and hatched eggs; the fertility and hatchability of the incubated eggs; as well as the hatchability of the fertile eggs, grouped by incubation batch, are shown in Table 1
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The average fertility of the eggs recorded in this work (81%) was within the range of values cited in the literature, being a little higher than those found by Paci et al. [10] in Red-Legged partridges kept in colonies (73.5 to 80.1%) and similar to those described by Bagliacca et al. [4] in Red-Legged partridges kept in pairs outdoors and provided with an artificial supplementation of the photoperiod (81.6%), as in our case. The average hatchability of the total of the incubated eggs that we observed (67.5%) was greater than that recorded by Paci et al. [10] in Red-Legged partridges kept in colonies (53.4 to 58.7%) but lower than that recorded in farm Red-Legged partridges kept under artificial photoperiod supplementation (83 to 84.1%) by Mori et al. [11]. The observed hatchability was also lower than that observed in Red-Legged partridges kept under a natural photoperiod (77.9%) by González-Redondo et al. [3] at a farm in the same province as the one used in this research. The average hatchability of the fertile eggs we recorded (83.3%) showed an intermediate value between those described by Paci et al. [10] in Red-Legged partridges kept in colonies (72.6 to 73.3%) and that recorded by Bagliacca et al. [4] in Red-Legged partridges kept outdoors in pairs under an artificial supplementation of the photoperiod (91.6%).
Highly significant differences were found in the fertility (2 = 297.97, df = 7, P < 0.001) and in the total hatchability of the incubated eggs (2 = 183.02, df = 7, P < 0.001) according to the incubation batch. The eggs in batches 2 (February 14th) to 5 (March 27th) showed greater fertility and hatchability, whereas the eggs in batches 7 (April 24th) and 8 (May 8th) presented lower fertility and hatchability. Depending on the incubation batch, the hatchability of the fertile eggs presented significant differences (2 = 16.31, df = 7, P = 0.022). In batch 4 (March 13th), the hatchability of the fertile eggs was greater, whereas in batch 7 (April 24th), it was lower.
Previous reports have not evaluated the variation in fertility and hatchability of the Red-Legged partridge eggs in relation to the laying date. However, the pattern of variation in the parameters that we recorded, in the sense that the fertility and the hatchability of the incubated eggs increased as the breeding season progressed and decreased as it approached its end (Table 1
), matches well with the seasonal character of the Red-Legged partridge’s reproductive pattern occurring under farm conditions and at any latitude [2, 3, 4, 11, 12, 13]. The fertility and hatchability of the Red-Legged partridge eggs that we observed followed a trend that has been reported in other poultry species including quail [14], turkeys [15], and broilers [16].
At the beginning of the laying period, the fertility and the hatchability of the incubated eggs and the hatchability of the fertile eggs were close to the average values of these parameters for the whole laying period. These values increased as the season progressed, reaching their maximum between late February and mid March, with a sharp decline occurring at the end of the laying period. Indeed, the hatchability of the incubated eggs and their fertility reached maximum values that were 13.5 and 11.4% greater, respectively, than the average for the whole laying period. At the end of the laying period, the values of these parameters had declined to one-third lower than the average values of the whole laying period. Furthermore, depending on their laying date, the fertile eggs’ hatchability presented significant differences, although, compared with the other 2 parameters, the variation range of this particular parameter is lower. The great variations of the hatchability of the incubated eggs to be found in this research were mainly caused by the great variations occurring in fertility during the reproductive season, as illustrated by the exponential function fitted to the data (R2 = 0.982, P < 0.001): hatchability of the incubated eggs = 19.0339 x exp (0.0155 x fertility).
The great variations in the parameters recorded in the present study occurred in spite of the artificial photoperiod supplementation program, which was the classical one used in partridges [2, 4, 11]. One aim of artificial photoperiod supplementation is to bring forward the commencement of laying by approximately 2 mo, to January [4, 11], as was the case in this study, instead of March, as would be the case under the natural photoperiod [2, 3]. Artificial supplementation of the photoperiod also increases the number of eggs laid by the partridges [2, 12]. However, the use of artificial light supplementation programs such as the one used here does not always make it possible to achieve an increase in hatchability. Instead, the partridges demonstrate an earlier reproductive activity [11] with a higher laying intensity [12]. This, however, does not usually enable the reproductive season to be extended beyond the date in which it might stop under a natural photoperiod, a phenomenon occurring in July [2, 13] or early August [3]. The exhaustion of sexual activity could therefore be the main reason for the sharp decline observed in the eggs’ fertility and hatchability. In fact, it has been stated that in the Red-Legged partridge, the plasmatic levels of luteinizing hormone [4, 13] and estradiol [13] diminish progressively as the laying period continues. Also, it may be that the sperm storage tubules, reported in many related species [17], are not so efficient at the end of the reproductive season. It is known that hens inseminated weekly underwent declines in fertility throughout the time [18]. In addition, at the end of the reproductive season we observed a reduction in the copulatory behavior of the males, as typically occurs in this species [2]. All these effects led to the reduction we observed of the fertility and hatchability of the incubated eggs at the end of the reproductive season.
No attempt was made in our study to assess the effect of the breeders’ age and nutritional status in relation to their reproductive performance. It is well known that the reproductive performance of the Red-Legged partridge varies with age [19], but in our study, the age of the breeders was within the interval for which the reproductive viability under farm conditions is optimum [2]. Moreover, as the breeders were fed with a specific commercial feed for partridges, all of the breeders had a nutritional status that was both highly similar and at an optimum level.
Of the 3 reproductive parameters analyzed in this work, the one with the greatest commercial importance for Red-Legged partridge game farms is the incubated eggs’ hatchability; in various countries there is a booming market in hatching eggs, such eggs being commercialized, with farms guaranteeing average hatchability—this knowledge usually being based upon previous experience [1]. Nevertheless, because there is a noticeable variation in fertility and hatchability of the incubated eggs according to the date when the eggs are purchased within the reproductive season, it can be concluded that the breeders need to guarantee an agreed hatchability according to the date that the eggs were laid, because a generalized average hatchability value applicable to the complete reproductive season has no validity.
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CONCLUSIONS AND APPLICATIONS
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- In Red-Legged partridges bred on game farms, the incubated eggs’ fertility and hatchability present a large seasonal variation, both parameters being higher in midbreeding season and lower at the commencement and end of the said season.
- Because of the seasonal variation of the above parameters, Red-Legged partridge farms selling eggs for incubation should inform their clients of the eggs’ expected fertility and hatchability as a function of the date that the eggs were laid.
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REFERENCES AND NOTES
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- González-Redondo, P., M. Delgado, and M. Reina. 2003. Caracterización de la puesta y su viabilidad en una granja cinegética de perdiz roja (Alectoris rufa). Pages 182–183 in Proc. 2nd Jornadas Ibér. Razas Autóctonas Prod. Tradic.: Ganaderia Ecol., Sevilla, Spain. Ganadería Ecol. Consejería Agric., Pesca, Junta de Andalucía, Seville, Spain.
- Bagliacca, M., B. Mori, and L. Gualterio. 1988. Egg laying under artificial photo-regulation in the red partridge. Pages 657–659 in Proc. 18th World’s Poult. Congr., Nagoya, Japan. Jap. Poult. Sci. Assoc., Nagoya, Japan.
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