Effects of the time to change from incubation to hatching temperature on the artificial incubation of red-legged partridge (Alectoris rufa) eggs

This study investigates, in red-legged partridge (Alectoris rufa), the effects of the time to change from incubation to hatching temperature on egg weight loss, hatchability, chick weight at hatch, incubation length, and development stage at embryonic mortality. Five batches of 80 eggs each were incubated at 37.8°C during the first 18, 19, 20, 21 or 22 d of incubation, and subsequently at 37.5°C until hatching. Hatchability, development stage at embryonic mortality and chick weight at hatch were not affected by the time of temperature change (p > 0.05). However, incubation length and egg weight loss after 21 d of incubation as representative of that of developed embryos were influenced by the incubation treatment (p < 0.001 and p < 0.05, respectively). Thus, eggs maintained at the incubation temperature of 37.8°C for 22 d not only hatched earlier (23.04 d) but also with lower dispersion than eggs from the other treatments. As hatching may start around day 22 of incubation, to improve hatching synchrony we could recommend to move A. rufa eggs from the incubator, set at 37.8°C, to the hatcher on the 21 d of incubation keeping the temperature unchanged, and reduce it to 37.5°C on the 22 d. Nevertheless, further research should be carried out to study the effect of this temperature scheduling on chick growth and performance. Additional key words: egg weight loss; game farming; hatchability; incubation length. * Corresponding author: [email protected] Received: 27-05-13. Accepted: 03-06-14. Abbreviations used: EA (early abortion); FWD (fertile without development); LA (late abortion); P (pipped but not out of shell); PD (positive development); RH (relative humidity). Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) Spanish Journal of Agricultural Research 2014 12(3): 727-731 http://dx.doi.org/10.5424/sjar/2014123-4543 ISSN: 1695-971X eISSN: 2171-9292 SHORT COMMUNICATION OPEN ACCESS 728 P. Gomez-de-Travecedo et al. / Span J Agric Res (2014) 12(3): 727-731 them to the hatcher, where temperature is lowered to 37.5°C, until hatching on day 23-24 (García Martín & Dalmau, 2003; González-Redondo et al., 2012). The reason for reducing the temperature at the end of the incubation is that some studies on hen eggs report that the temperature of the embryo at the end of its development is almost 2°C higher than at its beginning, due to the extra heat caused by the movement and metabolic activity of the embryos. As a consequence, heating needs are different at this late stage (Romijn & Lokhorst, 1956; Decuypere & Michels, 1992). However, hatching temperature scheduling has not yet been contrasted in red-legged partridge by scientific studies. Therefore, the present study aimed to investigate the effects of the time when the temperature is lowered from the incubation to the hatcher temperature, on hatchability, weight loss, incubation length and embryonic mortality of red-legged partridge eggs. A total of 400 hatching eggs were collected from a game farm located in the province of Seville (Spain). The breeding partridges, aged between 2 and 3 years, were fed with commercial feed (2,775 kcal kg metabolizable energy, 200 g kg crude protein, 42.5 g kg crude fat, 40 g kg crude f ibre and 30 g kg Ca; Avipacsa A-78, Sanders, Dos Hermanas, Spain) and were housed in pairs in outdoor cages measuring 50 × 65 cm. The partridges were initially subjected to natural lighting but, from December, artificial lighting was added, increasing the photoperiod by a quarter of an hour every day until 16 h of light (natural + artificial) were reached per day by January. Egg laying started in mid January. Eggs used in this trial were laid and collected between 23 and 25 March. On March 25, the eggs were randomly distributed in five batches of 80 eggs each. Twelve hours before being loaded in the incubator, all batches were pre-warmed at 23°C and 43% relative humidity (RH) by maintaining them in the room where the incubator itself was located. Then, all batches were loaded into the incubator (Masalles HS25, Masalles, Ripollet, Spain) on the same date (March 26). The incubator was set at 37.8°C and 55% RH, and eggs were turned 45° every hour. Egg batches were transferred to the hatcher (Maino Incubators 2630 XHM, Maino Enrico-Adriano S.n.c., Oltrona di San Mamette, Italy) on days 18, 19, 20, 21 or 22 from the beginning of the incubation, respectively. The hatcher temperature was 37.5°C. To maintain identical the other incubation parameters across batches, the hatcher was at 55% RH from the beginning of the incubation until day 21, and eggs went on being turned 45° every hour. On day 21 of incubation, RH was increased to 80% and the turning of eggs was stopped in all the experimental batches. All eggs were weighed before incubation and on day 21 of incubation as the time at which the embryos can be considered developed, since in this species hatching can start on day 21.5 under farming conditions (González-Redondo et al., 2012). Weight losses after 21 d of incubation were calculated for each egg, as a percentage of the initial weight. After the incubation period, the number of hatched chicks and unhatched eggs were recorded. Unhatched eggs were opened to determine macroscopically infertility or the following stages of embryonic mortality: fertile without development (FWD) when the blastodisc still had the characteristic shape and size of a fertile one but its outline was deteriorated, positive development (PD) when the blastoderm had further developed but there was still absence of blood formation, early abortion (EA) when blood rings or dead embryos at early stages were observed, late abortion (LA) in case of chicks fully formed but dead without pipping, or pipped but not out of shell (P) (Juárez-Caratachea & Ortiz, 2001; Ernst et al., 2004). The length of the incubation period was measured as the difference between the incubator loading and hatching dates, which were determined through hatching controls carried out every 12 hours. All the chicks were weighed at hatching. Statistical differences in the fertility, hatchability of the incubated eggs, as well as hatchability and embryonic mortality of the fertile eggs, as a function of the time of change (days 18, 19, 20, 21 or 22 of incubation) of the incubation temperature (37.8°C) to the hatching temperature (37.5°C), were analysed using contingency tables on which Pearson’s χ tests were performed. Statistical differences in the initial and final weights, weight losses of the fertile eggs during the first 21 d of the incubation period, chick weight at hatch and incubation length, as a function of the time of change in temperature during incubation, were analysed by one-way analysis of variance. When differences among time of change of temperature treatments were significant, means were separated using Duncan’s multiple range tests at the 0.05 level of significance. All results of the quantitative variables are expressed as mean ± standard error of the mean. The descriptive statistics maximum, minimum, coefficient of variation, and skewness and kurtosis coefficients were calculated for the variable incubation length. Differences in the variance Short communication. Hatching temperature scheduling in partridge 729 of the incubation length among treatments were also analysed. The analyses were conducted using SPSS 15.0 (SPSS Inc., Chicago, IL, USA). Average fertility (50.8%; Table 1) and hatchability of the total of the incubated eggs (44.5%; Table 1) were lower than in previous reports on A. rufa under farming conditions (73.5 to 89.7% and 53.4 to 86.4%, respectively; Paci et al., 1992; González-Redondo, 2010; Mourão et al., 2010) or in the wild (93% in hatchability; Tavares et al., 2001) and did not differ among treatments (χ4,400 = 5.661, p = 0.226 and χ4,400 = 7.450, p = 0.114, respectively). The breeding partridges had a similar age, characterised by the maximum fertility (Mourão et al., 2010), and eggs were collected in the middle of the reproductive season, when laying rate and fertility of red-legged partridge peaks (Fernandes Barbosa, 2009). Thus, differences between the fertility obtained in this research and the mean values found in the literature could be due to other farming conditions such as differences of the fertility selection in the breeding flocks, housing type or kind of feed used (King’ori, 2011). The low hatchability of the eggs set was subsequently caused by the low fertility. Hatchability of the fertile eggs (87.7%; Table 1) matched with values described for captive-bred redlegged partridges (72.6 to 91.6%; Bagliacca et al., 1988; Paci et al., 1992) and did not differ among experimental batches (χ4,203 = 4.896, p = 0.301). Furthermore, no differences were found among treatments in the mortality at each embryonic development phase, whose mean values were 0% in FWD, 2.5% in PD, 5.4% in EA, 3.9% in LA, and 0.5% in P phase (Table 1, χ16,203 = 13,656, p = 0.624). Chick weight at hatch was 14.27 ± 0.08 g, in agreement with values described for A. rufa under similar conditions (Beer & Jenkinson, 1981), and it was not influenced by the time of change from the incubation to the hatching temperature (Table 1, F4,173 = 0.393, p = 0.813). The average weight of the fertile eggs before incubation was 19.84 ± 0.09 g, regardless of treatment (Table 2; F4,395 = 1.015, p = 0.911) and, after 21 d of incubation, the average weight loss of the fertile eggs was 10.22 ± 0.12% of their initial weight. Both values matched with those previously described for A. rufa under similar conditions (Beer & Jenkinson, 1981; Mourão et al., 2010). Differences were found among treatments in the egg weight loss during incubation (F4,395 = 1.239, p = 0.036). Thus, although there was not a linear progression, eggs whose incubation temperature was reduced from 37.8 to 37.5°C on the 20 or 22 d of incubation lost more weight than eggs whose temperature was reduced on the 19 d (Table 2). The average incubation period lasted 23.39 ± 0.03 d, within the range of values described for this species (González-Redondo et al., 2012). Incubation length was highly influenced by the incubation treatment (F4,173 = 10.175, p < 0.001), being shortened as the change of the incubation to hatcher temperature delayed (Table 2). Thus, eggs whose temperature was Table 1. Fertility, hatchability, embryonic mortality and chick weight at hatch of red-legged partridge eggs according to the time of change from incubation temperature (37.8°C) to hatching temperature (37.5°C) Time of Eggs Hatchability Embryonic mortality5 Chick weight temperature incubated Fertility2 Hatchability3 of the (% of the fertile eggs) at hatch change1 (No.) (%) (%) fertile eggs4 (g) (mean ± (d) (%) FWD PD EA LA P SEM) 18 80 48.800 38.800 79.500 0.000 5.100 10.300 5.100 0.000 14.36 ± 0.17 19 80 47.500 43.800 92.100 0.000 0.000 5.300 2.600 0.000 14.36 ± 0.16 20 80 58.800 55.000 93.600 0.000 0.000 2.100 4.300 0.000 14.21 ± 0.16 21 80 42.500 36.300 85.300 0.000 2.900 2.900 5.900 2.900 14.36 ± 0.21 22 80 56.300 48.800 86.700 0.000 4.400 6.700 2.200 0.000 14.13 ± 0.20 χ 5.661 7.450 4.896 — 4.067 3.320 1.019 4.995