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Home > Vol 2, No 2 (2014) > Na-Lampang

Productivity and Tonic Immobility Duration of Thai Crossbred Chickens Raised at Different Stocking Densities

Pongchan Na-Lampang

Corresponding Author: pongchan@sut.ac.th
Article History: Received: 6 March 2014    Accepted: 5 April 2014

Abstract
The objective of this study was to investigate the effects of stocking density (8, 12 and 16 birds/m2) on and tonic immobility duration (a measure of fearfulness) of Thai crossbred chickens (n=900 birds) kept at 100 birds per pen. The results showed that stocking density had no significant (P>0.05) effect on body weight, body weight gain, feed intake, feed conversion ratio and mortality of chickens from the wk2 to 12. When stocking density was increased from 8 birds/m2 to 16 birds/m2, tonic immobility (TI) duration of the chickens increased significantly (P<0.05).However, the TI duration of chickens at a density of 12 birds/m2 was not significantly different from those of both the lower and the higher densities. In conclusion, Thai crossbred chickens could be stocked up to 12 birds/m2 without adverse effect on productivity and welfare when compared to those kept at 8 birds/m2.
Key words: Thai crossbred chicken, stocking density, productivity, tonic immobility

INTRODUCTION
Meat of native chickens is preferred by Thai people over the same products from commercial poultry because of their taste, leanness, and suitability to Thai special dishes (Wattanachant et al., 2004). Thus, native chicken meat is more highly valued than that coming from commercial poultry. The domestic market for Thai native chickens has increased significantly and overseas markets also have strong potential. This has led to a change of practice in raising native chickens in Thailand. Cross breeding of Thai native males with egg type females, rather than pure breeding of Thai native chickens, is used to obtain higher chick production. It is recommended by the Department of Livestock Development, Thailand, that stocking density used for open houses should be 8birds/m2.However, some producers rear their chickens at higher stocking densities in order to reduce the fixed costs of production and produce more kilograms of chickens per unit area. As it is known the at reduction in space per bird generally results in poorer productivity and welfare of the chickens (Estevez, 2007).The objective of this study was to investigate the effect of rearing at higher than recommended stocking density on production and tonic immobility duration, a measure of fearfulness (Marin et al., 2001), in Thai crossbred chickens.

MATERIALS AND METHODS

A total of 900mixed sex Thai crossbred chicks(Thai native males and ISA Brown commercial layer type females), supplied by Suranaree University of Technology poultry farm (Thailand), were reared from one day old to 13 wk of age without the use of beak trimming. The experiment lasted from February to April, 2011.
The pen sizes were 12.5 m2, 8.33 m2, and 6.25 m2 in area. There were 100 birds per pen. This resulted in treatment densities of 8, 12 and 16 birds/m2, respectively. The pens were bedded with approximately 5 cm of rice hulls.
Chicks were brooded for 2 wk before being randomly assigned to the treatments. At the end of the second wk, the chicks were vaccinated according to the recommendation of the , Thailand. The chickens were fed a standard commercial three phase broiler diet. Feed and water were fed ad libitum throughout the rearing period. During the first 3wk, feed was added 3 to 4 times a day. After that the feed was added twice per day (0800 h and 1630 h). The ratio of birds per feeder cup (diameterhigh: 40 cm×30 cm) or water bottle (4L capacity) was 25 to one.
Natural lighting was used after the brooding period until 13 wk old. The chicken house was protected from the wind and rain with plastic sheeting, which was also used to adjust the ventilation. Before stocking the birds, the house was sprayed with . Temperature and relative humidity in the chicken house were recorded continuously.
Data on average body weight (BW), body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR) and mortality rate were determined at the end of the experimentwhen they chickens were 12 wk old.
. The method was similar to that described by Campo et al. (2008). The bird was restrained for 10 s. The observer sat in full view of the bird, about 1 m away, and fixed his eyes on the bird to cause the fear-inducing properties of eye contact. .
The experimental unit considered was the pen. The experimental design used was a completely randomized design with three replicates per treatment. The data were subjected to analysis of variance with the General Linear Model procedure of SPSS 16.0. TI duration data were logarithmically transformed prior to analysis. When significance was indicated, differences among treatment means were tested by Duncan’s multiple range tests.

 RESULTS

During the experiment, average temperature and relative humidity in the chicken house in the morning (0700 h) and the afternoon (1430 h) were (Means ± SE) 24.06 ± 0.29°C, 30.30 ± 0.46°C, 88.09 ± 0.99% and

67.05 ± 1.46%, respectively. Different levels of stocking density did not affect BW, BWG, FI, FCR or mortality (Table 1).

Stocking density affected TI duration of the chickens (Table 2). The TI duration of chickensat16 birds/m2 was higher (P<0.05) than that for 8 birds/m2, while that at12 birds/m2 density was not significantly different from either the higher or lower densities.

 DISCUSSION

The final BW of the chickens (at 12 wk of age) was sufficient to reach the marketable live weight of 1.2 kg which is normal for Thai chickens (Haitook et al., 2003).
The results of this experiment agreed with those of Feddes et al. (2002) and Ravindran et al. (2006) who reported similar BW and BWG for chickens reared at three levels of low, middle, and high densities. The results also agreed with those of Thomas et al. (2004) who reported that stocking density had no effect on broiler mortality. However, Hall (2001) reported a significant increase of mortality in high stocking density in commercial farms. Dawkins et al. (2004) and Jones et al. (2005) argued that stocking density itself was less important to the physical health and mortality rates of the chickens than other environmental factors. Dawkins et al. (2004) showed that the differences between producers in terms of the environment they provide to the animals had more impact on their welfare than stocking density per se.
The longer TI duration observed at the highest stocking density indicates that the chickens were more fearful. These results are similar to the findings of Andrews et al. (1997) and Onbaşılar et al. (2008).The duration of TI response to manual restraint is widely considered to be a useful behavioral index of fear and thus welfare (Marin et al., 2001).This indicates that raising Thai cross breed chickens at 16 birds/m2 can compromise one measure of chickens’ welfare when compared to those raised at 8 birds/m2.
In conclusion, the results of this experiment suggest that Thai crossbred chickens could be kept at a stocking density of 12 birds/m2and maintain the same level of productivity and welfare status as those kept at the suggested 8 birds/m2 by the Department of Livestock Development, Thailand.

REFERENCE

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