Influence of turning duration during incubation on slaughter characteristics of broiler chickens

Introduction

The Indian poultry industry is one of the fastest-growing livestock sectors, producing nearly 4.995 million tonnes of broiler meat annually, per capita availability (7.39 kg) remains below the ICMR recommendation of 11 kg (Basic Animal Husbandry Statistics, 2023) [2] . Hatchery management plays a crucial role in determining the quality and performance of broilers raised for slaughter. Turning of hatching eggs during incubation remains essential for supporting normal embryonic development. Egg turning provides multiple benefits, including minimizing embryo malpositioning (Robertson, 1961) [7] and preventing abnormal adhesion of the embryo to the shell membrane (New, 1957) [5] . These effects are associated with improved embryonic development, such as protein accumulation in the amniotic fluid, growth of the area vasculosa, enhanced gas exchange (Deeming, 1989, Pearson et al., 1996; Tona et al., 2003) [3,6,9] and modulation of thyroid hormone levels (Tona et al., 2003) [9] . Variations in turning duration can improve the chick quality, early growth potential, and subsequent carcass characteristics. Slaughter characteristics such as dressing percentage, organ weights, and abdominal fat deposition are directly influenced by embryonic developmental conditions, positioning incubation practices as key determinants of final carcass quality. While extensive research exists on turning frequency and angle, limited information is available on how the duration of turning affects slaughter characteristics of broilers. Understanding these effects is vital for optimizing hatchery protocols, improving carcass yield, and enhancing overall economic returns. This study focuses on examining how different turning durations during incubation influence slaughter performance in broiler chickens.

Materials and Methods

A total of 840 eggs laid by commercial broiler breeder hens at the age of 33.5 th week were received to study the effect of hatching-eggs turning duration on hatchery performances. The fresh hatching eggs received from the breeder farm were stored in egg storage room for 3 days at a temperature of 18 °C with relative humidity of 75 percent. Total 840 eggs were randomly divided into seven treatment groups of 120 eggs per treatment with three replicates per treatment (40 eggs per replicate). The treatment eggs were incubated in forced-draft type incubator and the group of eggs were turned once in one hour from day one to 18.5 days (444 hours) of incubation (T 1Control), 17.5 days of incubation (T 2 ), 16.5 days of incubation (T 3 ), 15.5 days of incubation (T 4 ), 14.5 days of incubation (T 5 ), 13.5 days of incubation (T 6 ) and 12.5 days of incubation (T 7 ) in setter compartment. A total of 30 chicks (15 male and 15 female chicks) from each treatment group were randomly selected, divided into three replicates with five males and five females per replicate (totally 210 chicks for seven treatments), weighed, wingbanded, and placed in their respective treatment partitions for assessing slaughter characteristics. The detail of experiment is presented in Table 1. All the birds were reared in open-sided deep litter system with standard and uniform feeding and management conditions for 35 days. Where, * dressed weight = New York dressed weight -weight of viscera, head, legs, others offal's and giblet.

C) Organs weight

Organ yield (%) = Weight of the organ* (g) × 100 Pre slaughter live weight (g) Where, *Gizzard, liver, heart, small intestine, abdominal fat

Results and Discussion

Slaughter characteristics

The influence of turning duration during incubation on slaughter characteristics of broiler chickens is presented in Table 2, The result showed that New York dressing yield (%) did not differ significantly among the treatment groups, ranging from 92.11% (T 3 ) to 92.64% (T 2 and T 7 ). T 6 showed a significantly higher (p<0.05) dressed weight percentage (73.76%) compared to all other treatment groups, while T1 (70.70%) recorded the lowest dressed weight. The giblet, heart, gizzard and small intestine weights (%) showed no significant differences among treatment groups. T 6 (8.26%) recorded a slightly higher giblet yield while T 2 (4.91%) had the lowest. Heart weight ranged from 0.54% (T 3 ) to 0.61% (T 4 ) and small intestine weight varied from 5.99% (T 4 ) to 6.91% (T 1 ), indicating uniform organ development across treatments. A significant difference (p<0.05) was observed for both liver weight and abdominal fat weight among treatments. The highest liver weight (%) was recorded in T 7 (2.51%), followed by T 2 (2.25%) and T 3 (2.22%), while the lowest weight observed in T 4 (2.07%) and T 6 (2.08%). Similarly, abdominal fat percentage differed significantly (p<0.05), with T 1 and T 7 (1.13%) showing the highest and T 4 (0.74%) the lowest. Overall, birds in T 6 exhibited slightly better carcass yield performance, while those in T 4 showed leaner carcasses with lower abdominal fat deposition and smaller intestinal weights. The literature concerning the influence of turning duration during incubation on New York dressing yield, dressed weight, giblet weight, heart weight, liver weight, gizzard weight, abdominal fat percentage and small intestine weight of broilers was not traceable. Value in each cell is the mean of 6 observations Mean within a column bearing different superscripts differ significantly NS-Non significant, *Significant (p<0.05)

Conclusion

This study concluded that T 6 exhibited highest dressed weight percentage and overall superior carcass performance. New York dressing yield (%) remained similar across treatments, indicating consistent processing efficiency. Liver and abdominal fat percentages showed variation, with T 7 exhibiting the highest liver weight and T 1 and T 7 showing higher abdominal fat deposition. However, the Eggs turned during incubation from 0 hour to 13.5 days (T 6 ) emerged as the best treatment, effectively enhancing dressed yield and maintaining desirable carcass traits without adversely affecting other slaughter parameters.

References

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