Quality assessment chicks from different hatcher temperatures with different scoring methods and prediction of broiler growth performance

Abstract

The aim of the current study was to determine the quality of chicks from different hatcher temperatures for the prediction of broiler growth performance. The hatcher temperatures were applied as follows: control (36.8–37.0°C), acute high hatcher temperature (38.8–39.0°C for 3 hours daily, 36.8–37.0°C in remaining time) and chronic high hatcher temperature (38.8–39.0°C). The chick quality was measured with Tona score, Pasgar score, chick-hatching weight, yolk-free chick weight and chick length. Whereas the chicks of control group were the highest quality with Tona and Pasgar methods, the chicks of the control and acute high temperature groups were better than the chronic high temperature group according to chick weight and yolk-free chick weight as chick quality indicators. Between days1 and 7, the relative growth was the highest in control group with a value of 373.0%. The correlations between chick weight on day 1 and Tona score, Pasgar score, chick weight, yolk-free chick weight and chick length were significant. The correlation between chick quality scoring methods and relative growth between days 1 and 7 was varied among the treatment groups. In conclusion, short- or long-term high hatcher temperatures affected one-day-old chick quality and first-week broiler growth performance.

Keywords:

• hatcher temperature
• chick quality
• Tona
• Pasgar
• chick weight

1. Introduction

The one-day-old chick quality is an important criteria for hatchery success and also profitability of broiler producers. In hatcheries, the essential objective is to maximize hatchability with a great number of high-quality and saleable chicks that are desired by broiler producers for their high viability and slaughter yield (Decuypere and Bruggeman 2007).

In hatcheries, the chick quality is determined by quantitative and qualitative scoring, considering various numerical or observation quality criteria, and these measurements are useful for the estimation of broiler growth performance (Decuypere and Bruggeman 2007). Various quality scoring systems have been developed, considering different quantitative and qualitative parameters such as Tona score and Pasgar score (Boerjan 2002; Tona et al. 2003). The good quality of one-day-old chick can be defined as clean; dry; without dirt, contamination and deformities; and with bright, clear and opened eyes, and clean and completely sealed navel (Deeming 2000; Decuypere et al. 2001). Any yolk sac or dried yolk membranes should protrude from the navel, and no signs of respiratory diseases should be observed (Preez 2007). The whole body of chick and legs should have normal confirmation; there should be no swelling or lesions on hock or skin. The beak and toes should be well formed, firm and straight. The one-day-old chick should be alert, active and interested in its environment, responding to sounds (Tona et al. 2005). In hatcheries, the assessing of chick quality based on subjective parameters requires experience and also it is difficult to repeat. Therefore, some quantitative scoring methods also have been developed to determine chick quality with considerable objective measurements (Raghavan 1999; Deeming 2000; Boerjan 2002; Tona et al. 2003). There are four quantitative methods for scoring chick quality: Tona or Pasgar score, the one-day-old chick weight, yolk-free chick weight and chick length (Meijerhof 2009a).

The first method is Tona or Pasgar score that uses a standardized scoring system with some criteria considering viability, yolk sac uptake, closure of navel and the ability of the chick recovering after being placed on its back (Boerjan 2002; Tona et al. 2003; Preez 2007). The second method is the one-day-old chick weight (Deeming 2000; Decuypere et al. 2002), and the third one is yolk-free body weight (Meijerhof 2009a). The third method is better than second one, because chick-hatching weight includes the actual chick weight and residual yolk sac weight. The last scoring method is the chick length that is measured from the tip of the beak to the middle toe (Deeming 2005; Wolanski et al. 2006). Some researchers found a positive correlation between chick length and body weight at 42 days of age (Hill 2001; Meijerhof 2006; Molenaar et al. 2008).

Incubation factors such as temperature, humidity, turning and ventilation influence day-old chick quality in the way of chick weight, body length, activity, yolk sac uptake, navel closure on hatching day and post-hatch growth performance (Meijerhof 2003; Willemsen et al. 2008). Poor incubation conditions can cause insufficient embryo development and lower hatchability (Meijerhof 2003). Incubation temperature is one of the most important factors to assure optimum chick quality and also for post-hatch broiler performance (Lourens 2003, Willemsen et al. 2008, Ipek et al. 2014). Embryos with high growing rates are sensitive to temperature fluctuations, and small deviations from optimum ranges have negative effects on hatchability and hatchling quality (Molenaar et al. 2010). So fluctuations in setter or hatcher temperatures have negative impacts on chick quality, and it causes major economic losses because of the negative effects on post-hatch performance and slaughter yield (Wilson 1991; Shafey 2004).

In large-scale production, some problems with machine maintenance and temperature settings could result in overheating of embryos especially during late term of incubation. Therefore, some chick quality problems could be seen and their growing period could be negatively affected. So, definition of the day-old chick quality with higher accuracy is an important factor for the prediction of broiler growth performance, especially because it is known that there is relation between chick quality and first-week chick mortalities due to omphalitis and growth rate.

In researches, the effects of various factors such as breeder age, breeder line and egg weight on chick quality have been investigated with the quality scoring methods. It is also known that the most critical factor is incubation temperature during embryonic development. Yet there is a lack of studies about assessment of chick quality with different scoring methods and incubation temperatures. So the aim of the current study was to determine the quality of chicks from different hatcher temperatures with different quality scoring methods for the prediction of broiler growth performance.

2. Materials and methods

The care and use of animals were in accordance with the laws and regulations of Turkey and approved by the Ethical Committee of the Uludağ University (License number 2013-15/01).

A total of 1800 eggs were obtained from a commercial Ross 308 broiler breeder parent stock at 42 weeks of age. The eggs were stored at 18°C and 65% RH for 3 days and warmed to room temperature (22°C) for 8 hours before setting. All eggs were weighed (55–65 g) prior to incubation and then incubated in the same incubator (1800 capacity egg setter; Cimuka Inc., Ankara, Turkey) at full capacity at 37.5°C and a relative humidity of 55–60% during the first 18 days of incubation. On the 18th day of incubation, the eggs were candled and viable eggs were randomly divided into three groups and placed into hatching baskets (7 hatching baskets, 80 eggs per basket and 560 eggs per treatment group). Each hatching basket was considered a replicate. The eggs were therefore transferred to three hatcher cabinets (640 capacity egg hatcher; Cimuka Inc., Ankara, Turkey) for these temperatures: control (36.8–37.0°C), acute high temperature (38.8–39.0°C for 3 hours daily, 36.8–37.0°C in remaining time) and chronic high temperature (38.8–39.0°C).

After hatching process, chicks were subjected to different chick quality measurement methods. The chick quality was measured with Tona score, Pasgar score, chick-hatching weight, yolk-free chick weight and chick length. A total of 90 chicks per treatment group were randomly chosen for scoring with Tona and Pasgar methods. The Tona score was done as previously reported by Tona et al. (2003) with scoring activity, feathering and appearance, condition of eyes, conformation of legs, condition of navel area, remaining yolk sac and status of the yolk membranes. It was expressed as a hedonic scale, and the quality score was calculated by summing up the scores for these characteristics. In the Pasgar score, chicks lose score from a maximum of 10 score when abnormalities are seen for activity, navel condition, confirmation of legs and beak, and status of yolk membranes (Boerjan 2002). Then these chicks were measured for chick weight and length. Chick length was measured from the tip of the beak to the tip of the middle toe by placing the chick face down on a flat surface and straightening the right leg (Hill 2001). Then a total of 40 chicks were randomly chosen and killed by cervical dislocation to determine yolk-free chick weight. The yolk-free chick weight was determined by subtracting residual yolk sac weight from chick weight.

A total of 50 chicks from each treatment group were placed in rearing pens with a surface area of 2.0 × 2.0 m². Wood shaving was used as litter material and was laid at a thickness of 8–10 cm on the floors of the pens. The chicks received a standard pelleted broiler starter diet (22.5% CP and ME 12.8 MJ/kg of diet) between days 1 and 14, and a grower diet (22.0% CP and ME 13.3 MJ/kg of diet) between days 15 and 21. Feed and water were offered ad libitum during the rearing period. The chicks were exposed to 24 hours of light during the first week, and they were exposed to 23 hours of light and 1 hour of darkness until 21 days of age. Room temperature was 33°C at day 1 of age and decreased gradually by 3°C/wk until day 21 of age. All chicks were given an individual wing band. The live weight values were monitored on a weekly basis and relative growth was calculated with a formula reported by Willemsen et al. (2008):

2.1. Statistical analysis

The effects of different hatcher temperatures on chick quality and growth performance were analyzed by one-way analysis of variance using the general linear model procedure (SAS Institute Inc. 1989). Analyses for percentage data were conducted after square root of arcsine transformation of the data. Significant differences among treatment means were determined by Duncan's multiple range test. The correlations between chick quality scoring methods, quality parameters and growth performance were calculated with Pearson's correlation analysis.

3. Results

The effects of different hatcher temperatures on chick quality are presented in Table 1. Chick quality was scored with different scoring systems such as Tona score, Pasgar score, day-old chick weight, yolk-free chick weight and chick length. The chick quality of chicks from different hatcher temperatures was varied according to scoring methods. Tona score was higher with an average score of 90.4 in the control group than in the acute and chronic high temperature groups with an average score of 70.5 and 68.9, respectively (P < 0.01). Similarly, Pasgar score was the highest for chicks in the control group with a score of 8.9 compared to the acute and chronic groups with a score of 7.1 and 8.3, respectively (P < 0.01). The chick weight was higher in the control and acute high temperature groups than in the chronic high temperature group (P < 0.01). It was 44.3 g, 44.5 g and 40.7 g for chicks from the control, acute high temperature and chronic high temperature groups, respectively. Similar differences were observed for yolk-free chick weight; it was higher in the control and acute high temperature groups with a value of 39.3 g and 40.0 g, respectively, compared to the chronic high temperature group with a value of 35.3 g (P < 0.01). The chick length was similar between the treatment groups. Whereas the chicks of the control group were determined as the highest quality with Tona and Pasgar score methods, the chicks of the control and acute high temperature groups were better than the chronic high temperature group when considering chick weight and yolk-free chick weight as indicators of chick quality.

Table 1. Chick quality scores of chicks from different hatcher temperatures with different scoring methods.

	Scoring methods
Groups	Tona score (n = 90)	Pasgar score (n = 90)	Day-old chick weight (n = 90)	Yolk-free chick weight (n = 40)	Chick length (n = 90)
Control group	90.4 ± 1.97^a	8.9 ± 0.18^a	44.3 ± 0.39^a	39.3 ± 0.49^a	20.0 ± 0.09
Acute group	70.5 ± 1.97^b	7.1 ± 0.18^c	44.5 ± 0.39^a	40.0 ± 0.49^a	19.9 ± 0.09
Chronic group	68.9 ± 1.97^b	8.3 ± 0.18^b	40.7 ± 0.39^b	35.3 ± 0.49^b	20.1 ± 0.09
Probabilities	<0.01	<0.01	<0.01	<0.01	0.078

Note: Means ± SEM in row that possess different superscripts differ significantly (P < 0.01; P < 0.05).

The live weights of chicks from different hatcher temperatures during the growing period are presented in Table 2. On day 1 of the growing period, live weights of chicks were higher in the control and acute high temperature groups than in the chronic high temperature group (P < 0.01). From day 1 to day 21 of the growing period, the chicks of the control group were consistently heavier with values of 208.5 g, 543.8 g and 1083.2 g on days 7, 14 and 21, respectively, compared to the chicks of the acute and chronic high temperature groups (P < 0.01).

Table 2. Live weights of chicks from different hatcher temperatures during the growing period (n = 50 chicks/group).

	Live weight (g)
Groups	Day 1	Day 7	Day 14	Day 21
Control group	44.2 ± 0.52^a	208.5 ± 1.48^a	543.8 ± 9.72^a	1083.2 ± 13.13^a
Acute group	44.6 ± 0.52^a	192.0 ± 1.48^b	463.3 ± 9.72^b	992.8 ± 13.13^b
Chronic group	40.5 ± 0.52^b	165.6 ± 1.48^c	449.6 ± 9.72^b	930.2 ± 13.13^c
Probabilities	<0.01	<0.01	<0.01	<0.01

Note: Means ± SEM in row that possess different superscripts differ significantly (P < 0.01; P < 0.05).

The relative growth of the chicks from different hatcher temperatures during the growing period are presented in Table 3. Between days 1 and 7 of the growing period, the relative growth was the highest in the control group with a value of 373.0%, compared to the acute and chronic high temperature groups with a value of 331.5% and 307.9%, respectively. The higher relative growth between days 7 and 14 was observed in the control and acute high temperature groups with a value of 160.9% and 172.3%, respectively, than in the chronic high temperature group with a value of 141.5%. Between days 14 and 21, the highest growth rate with a value of 113.9% was in the acute high temperature group compared to the control and chronic high temperature groups (P < 0.01).

Table 3. Relative growth (%) of chicks from different hatcher temperatures during the growing period (n = 50 chicks).

	Relative growth (%)
Groups	Days 1–7	Days 7–14	Days 14–21
Control group	373.0 ± 6.28^a	160.9 ± 5.30^a	102.2 ± 3.60^b
Acute group	331.5 ± 6.28^b	172.3 ± 5.30^a	113.9 ± 3.60^a
Chronic group	307.9 ± 6.28^c	141.5 ± 5.30^b	107.0 ± 3.60^ab
Probabilities	<0.01	<0.01	<0.01

Note: Means ± SEM in row that possess different superscripts differ significantly (P < 0.01; P < 0.05).

The correlations between chick quality scoring methods in different hatcher temperatures are presented in Table 4. The correlation between Tona score and Pasgar score was significant for chicks from the control, acute and chronic high temperature groups. The correlation was positive in the control (r = 0.358) and acute high temperature (r = 0.594) groups, whereas correlation was negative in the chronic high temperature (r = –0.687) group. Tona score was negatively correlated with chick weight in the control (r = –0.284) and acute high temperature (r = –0.275) groups. The correlation between Tona score and yolk-free chick weight was not significant for all treatment groups; the correlation between Tona score and chick length was significant for the control (r = 0.340), acute (r = 0.339) and chronic high temperature (r = 0.312) groups.

Table 4. Correlations between different chick quality scoring methods in different hatcher temperatures.

		Scoring methods
Groups	Methods	Tona score	Pasgar score	One-day chick weight	Yolk-free chick weight
Control group	Pasgar	0.358**	–	–	–
	Chick weight	–0.284*	–0.390**	–	–
	Yolk-free chick weight	–0.122	–0.364**	0.958**	–
	Chick length	0.340**	0.070	–0.144	0.045
Acute group	Pasgar	0.594**	–	–	–
	Chick weight	–0.275*	–0.383**	–	–
	Yolk-free chick weight	–0.074	–0.154	0.895**	–
	Chick length	0.339**	0.068	0.362**	0.555**
Chronic group	Pasgar	–0.867**	–	–	–
	Chick weight	0.008	–0.062	–	–
	Yolk-free chick weight	0.050	–0.152	0.385**	–
	Chick length	0.312**	–0.321**	–0.482**	0.092

*P < 0.05; **P < 0.01.

The correlation between Pasgar score and chick weight was significant and negative in the control (r = –0.390) and acute high temperature (r = –0.383) groups. It was found that Pasgar score was negatively correlated with yolk-free chick weight only in the control group (r = 0.364). In the chronic high temperature group, the correlation between Pasgar score and chick length was significant (r = –0.321).

It was found that chick weight was positively correlated with yolk-free chick weight in the control, acute and chronic high temperature groups. However, the correlation was relatively higher in the control (r = 0.958) and acute high temperature (r = 0.895) groups compared to the chronic high temperature (r = 0.385) group. The correlation between chick weight and chick length was significant in the acute (r = 0.362) and chronic high temperature (r = –0.482) groups. In the acute temperature group, it was a positive correlation between yolk-free chick weigh and chick length (r = 0.555).

The correlations between chick quality and first-week growth performance of chicks from different hatcher temperatures are presented in Table 5. In the control group, the correlations between chick weight on day 1 and Tona score (r = –0.284), Pasgar score (r = –0.390), chick weight (r = 1.00) and yolk-free chick weight (r = 0.958) were significant. The correlations between chick weight on day 1 and Tona score (r = –0.240), Pasgar score(r = –0.354), chick weight (r = 0.903), yolk-free chick weight (r = 0.791) and chick length (r = 0.366) were significant in the acute high temperature group. However, in the chronic high temperature group, significant correlations were found between chick weight on day 1 and chick weight (r = 0.543), and chick weight and yolk-free chick weight (r = 0.269). On day 7, significant correlation was only between live weight on day 7 and chick length (r = 0.267) in the acute high temperature group.

Table 5. Correlations between chick quality and first-week growth performance of chicks from different hatcher temperatures.

		Growth performance
Groups	Methods	Day 1	Day 7	Relative growth (%)
Control group	Tona	–0.284*	0.058	0.295*
	Pasgar	–0.390**	–0.137	0.332**
	Chick weight	1.000**	0.024	–0.937**
	Yolk-free chick weight	0.958**	0.117	–0.862**
	Chick length	–0.144	–0.188	0.070
Acute group	Tona	–0.240*	–0.135	–0.016
	Pasgar	–0.354**	–0.195	0.005
	Chick weight	0.903**	0.158	–0.357**
	Yolk-free chick weight	0.791**	0.129	–0.320**
	Chick length	0.366**	0.267*	0.043
Chronic group	Tona	0.105	–0.008	–0.076
	Pasgar	–0.182	0.145	0.249*
	Chick weight	0.543**	–0.112	–0.438**
	Yolk-free chick weight	0.269*	–0.119	–0.279*
	Chick length	–0.176	–0.086	0.028

*P < 0.05; **P < 0.01.

The correlation between chick quality scoring methods and relative growth between days 1 and 7 was varied among the treatment groups. In the control group, the correlations between relative growth and Tona score (r = 0.295), Pasgar score (r = 0.332), chick weight (r = –0.937) and yolk-free chick weight (r = –0.862) were significant. Significant correlations were found between relative growth and chick weight (r = –0.357) and yolk-free chick weight (r = –0.320) in the acute high temperature group. Following were the correlations in the chronic high temperature group: between relative growth and Pasgar score (r = 0.249), chick weight (r = –0.438) and yolk-free chick weight (r = 0.279).

4. Discussion

The chick quality has gained increased importance for hatcheries and also for broiler producers because it has been accepted as an indicator of broiler growth performance. It is known that there is a critical relationship between the day-old chick quality and post-hatch broiler performance (Tona et al. 2003; Meijerhof 2009b). When optimum incubation conditions are provided, yolk sac is absorbed exactly by embryos and navel of chicks is closed well; thus, the number of good quality chicks increases and early stage chick mortality due to uncovered navel or yolk sac and E. coli infections can be reduced (Meijerhof 2003). In hatcheries, the day-old chick quality is measured with different scoring systems: Tona score, Pasgar score, one-day-old chick weight, yolk-free chick weight and chick length.

During incubation, the chick quality is affected by some factors. One of the most important factors that affect chick quality is incubation temperature. In this study, the Tona and Pasgar scores varied among the hatcher temperature groups, and they were higher in the control group compared to the acute and chronic high incubation temperature groups. These results showed that the high hatcher temperatures and the period exposed to high temperature have negative effects on one-day-old chick quality.

The chick weight and yolk-free chick weight were higher in the control and acute high temperature groups than in the chronic high temperature group. No significant difference was observed between the control and the acute high temperature groups for chick weight and yolk-free chick weight. It shows that short-term high temperatures during hatching period as acute high temperature affects one-day-old chick quality in different ways from long-term high temperature as chronic high temperature. Whereas the chicks of the control group were determined as the highest quality with Tona and Pasgar score methods, the chicks of the control and acute high temperature groups were better than the chronic high temperature group in consideration of chick weight and yolk-free chick weight as chick quality indicators. Molenaar et al. (2011) applied normal (37.8°C) and high (38.9°C) incubation temperatures during the hatching period, and they reported a higher chick weight in the normal incubation temperature group. But, chick length was similar among groups, so the different hatcher temperatures did not affect the chick length at hatch. Similarly, Joseph et al. (2006) found that higher temperature during hatching period resulted in lower chick-hatching weight, but similar chick length compared to control. Similarly, in this study, chick length was similar in the treatment groups.

It was reported that live weight on day 7 is the best predictor of slaughter weight (Willemsen et al. 2008). In this study, on days 7, 14 and 21 of the growing period, the live weights of chicks were lower in the acute and chronic groups compared to the control group. It clearly showed that there is a relationship between Tona and Pasgar scores and live weights of chicks during the growing period compared to chick weight and yolk-free chick weight. It is supported with the finding of Meijerhof (2009a) that chick weight could not be a good standard for the determination of chick quality, because chick weight is correlated with egg-setting weight and it compromises the actual body weight and residual yolk weight. Yolk-free chick weight demonstrates how much of egg content was converted into embryo weight, so it is a more reliable indicator of chick quality (Meijerhof 2009a).

Suboptimal incubation conditions also cause deficiencies in development during embryonic stage and in broiler growth performance during rearing period (Meijerhof 2003). Hill (2002) reported that optimum incubation temperature is required for competence development of organs and growth; if not, it supresses development, growth and survival rate. In this study, the relative growth between days 1 and 7 of growing period was the highest in the control group, whereas it was higher between days 7 and 14 in the control and acute groups compared to the chronic group. But, during the last week (days 14–21), the highest relative growth was in the acute high temperature group. During the growing period, the chicks of the chronic high temperature group had lower relative growth, and it was supported by lower chick quality scores with Tona, Pasgar, chick weight and yolk-free chick weight. It clearly showed that the higher temperatures could negatively affect the chick quality and post-hatch growing and broiler performance. Deeming (2000) reported that higher incubation temperatures increase oxygen requirements of embryos. As a result of much more burning of oxygen, waste heat production and also incubation temperature show an increase (Lourens 2003). As a result of this, growth rate is deteriorated, utilization of albumin proteins is repressed and embryo goes under stress. At hatching, higher late-term embryonic mortalities, lower hatchability, worse quality of chicks and post-hatch early period chick mortalities could occur (Deeming 2000; Lourens et al. 2005, 2007).

Lately, the effects of different incubation temperatures in a certain stage on embryonic development, chick quality and broiler performance have been investigated by different researchers. Hulet et al. (2007) investigated the effects of low (37.5°C), control (38.6°C) and high (39.7°C) temperatures during hatching stage of incubation on broiler performance. As a result, they found that differences in chick-hatching weight reflected the final broiler weight. The highest chick-hatching weight was found in high temperature group as 43.1 g. In the low temperature and control groups, hatching weight was determined as 41.1 g and 42.2 g, respectively. At the end of rearing period, higher final broiler weight was found in the control (2263.3 g) than others (low, 2213.8 g; high, 2165.7 g). Similarly, in this study, on day 21, the live weights of chicks in the control, acute and chronic groups were 1083.2 g, 992.8 g and 930.2 g, respectively.

In the Tona score, activity, feathering and appearance, condition of eyes, conformation of legs, condition of navel area, remaining yolk sac and status of the yolk membranes are scored (Tona et al. 2003), whereas in the Pasgar score activity, navel condition, confirmation of legs and beak, and status of yolk membranes are scored (Boerjan 2002). It was previously reported that the chick quality score has an importance for prediction of broiler performance (Tona et al. 2003, 2005). In a study carried out by Tona et al. (2005), the relationship between chick quality parameters was investigated. And it was found that quality parameters were linked with each other; for example, the chicks with poor condition of the navel area were low-quality chicks and it was highly correlated with the conditions of the appearance and activity, the amount of retracted yolk and remaining yolk membranes (Tona et al. 2005). The different incubation temperatures affect these parameters at hatch in different ways, so the chick quality scores in different scoring systems differ at hatch. In this study, the relationships between these scoring methods have been investigated, taking into consideration different hatcher temperatures. The relationship between Tona and Pasgar scores and chick length were significant in the control, acute and chronic high temperature groups. But in the chronic high temperature group, the correlation between Tona score and Pasgar score was negative, and the chronic high temperature during hatching period affected the parameters of Tona and Pasgar scores differently. It was remarkable that there is a negative correlation between Tona score and chick-hatching weight in the control and acute high temperature groups. The Pasgar score correlated differently with other quality scoring methods in treatment groups. For example, Pasgar score correlated negatively with chick weight and yolk-free chick weight in the control group, whereas it correlated only with chick weight in the acute high temperature group and with chick length in the chronic group. As it was expected, the correlation between chick weight and yolk-free chick weight was significant in all treatment groups, but a weaker correlation was observed in the chronic high temperature group compared to the control and acute high temperature groups. Similar results are concluded by Willemsen et al. (2008). The relationship between chick weight and chick length was in the chronic high temperature group, and it was supported by the other findings of Wolanski et al. (2006) and Willemsen et al. (2008). A significant correlation between yolk-free chick weight and chick length was found only in the acute high temperature group. These results showed that the chick quality parameters are affected by small deviations in incubation temperatures.

The correlations between live weights on day 1 and all chick quality scoring methods were significant in the acute high temperature group, whereas only chick length in the control group and chick weight and yolk-free chick weight in the chronic high temperature group. Some researchers showed that a correlation between one-day-old chick weight and slaughter weight exists. Powell and Bowman (1964), Proudfoot and Hulan (1981) and Sklan et al. (2003) found a positive relationship, whereas Gardiner (1973), Shanawany (1987), Wolanski et al. (2003) and Tona et al. (2004) found no relationship between the two parameters. Some researchers found a positive correlation between chick length and body weight at 42 days of age (Hill 2001; Meijerhof 2006; Molenaar et al. 2008). Molenaar et al. (2007) reported that the chick length on hatching day had a predictive value for slaughter weight (r = 0.36) for male broilers. On day 7, significant correlation was observed between live weight on day 7 and chick length in the acute high temperature group. It can be understood that there were no relationships between live weight on day 7and chick quality. In the control group, the correlations between growth rate and Tona and Pasgar scores, chick weight and yolk-free chick weight were significant. The correlation between the chick weight and growth rate was negative in all treatment groups. Similarly, Tona et al. (2003, 2005) also found a negative correlation (r = –0.42) between chick weight and relative growth. In the acute high temperature group, correlations between live weight on day 7 and chick weight and yolk-free chick weight were significant, whereas in the chronic high temperature group, between live weight on day 7 and Pasgar, chick weight and yolk-free chick weight. These results showed that a negative correlation between growth rate and chick-hatching weight and yolk-free chick weight exists.

5. Conclusion

In conclusion, the one-day-old chick quality can be measured with various scoring methods to predict broiler growth performance under commercial conditions. The first stage of successful and profitable broiler production depends on accomplished hatchery management and good quality and healthy chick production. During incubation, incubation temperature affects embryonic development and chick quality at hatch and post-hatch broiler performance. Because of large-scale production, broiler performance standards like slaughter weight, growth rate, feed conversion rate and mortality are too important for producers. And it is known that first-week broiler growth performance and mortality are related with chick quality. So determining the chick quality with high accuracy and objectivity is very important, but still there is lacking evidence of correlations between day-old chick quality methods and post-hatch performance, especially in different incubation conditions. Therefore, chick quality and relationships between these parameters and post-hatch performance should be searched in detail, considering various factors such as different incubation conditions, breeder age and breeder lines.

Funding

This study was financially supported by the Scientific Research Project Council of Uludağ University [Project Number HDP(Z)-2013/37].

Additional information

Funding

Funding: This study was financially supported by the Scientific Research Project Council of Uludağ University [Project Number HDP(Z)-2013/37].