Broiler Performance, Live Weight Variance, Feed and Water Intake and Carcass Quality at Different Stocking Densities

 
 
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 Introduction
Broiler production systems must provide adequate floor area, feed and water. High stocking densities can cause stress to broiler chickens in several ways:

1. Heat stress - Excess body heat generated by broilers is released to the air. More birds in a given space will raise the environmental temperature throughout the barn, which can cause heat stress.
2. Poor air quality due to inadequate air exchange.
3. Increased ammonia levels.
4. Restricted access to feed.
5. Restricted access to water.

The overall effect of reducing floor space on broiler chickens can be poorer growth rate, feed efficiency, liveability, and in some cases, carcass quality (Puron et al., 1995). Also, decreased bird movement can result in poor leg quality (Andrus et al. 1997).

At stocking densities ranging from 10 to 20 birds/m2, male broilers had a linear reduction in live weight and feed intake. As stocking density increased, however, there was no difference in feed conversion or mortality to 7 wk of age (Puron et al., 1995). Female broilers show a similar trend in response to increasing stocking densities, except the reduction in live weight and feed consumption was not significant. Up to a critical point, profitability increases with increased stocking density. The effect of various stocking densities on carcass quality still needs to be determined. This study was undertaken to investigate the effects of stocking density and water nipple density on live weight, water consumption, and carcass quality.

Approach
A total of 6000 broiler female chicks were used for two 6-week trials. The stocking densities used in this study were 0.45, 0.60, 0.75, and 0.90 ft2/bird. Each pen had one overhead fan placed that directed air to the center of the pen thus providing good air movement and cooling for the birds.

Water and feed was provided ad libitum with 23 h light and 1 h dark. At processing, the number of birds with severe (deep), light (surface), old (occurred before shipping) and new (occurred during shipping) scratches were recorded for each density. Condemned, contaminated, and trimmed carcasses were assessed and recorded for each pen. Eviscerated weights for each individual carcass were recorded.

Results

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Performance
Figure 1 shows the final weights and productivity of the birds in the trial. Birds grown at the highest stocking density (0.45 ft2/bird) had the lowest BW (1898 g) and carcass weight (1334). The 0.75 ft2/bird treatment were approximately 100 g heavier at 1985 and 1432 g (live and carcass weights, respectively).

Broilers reared in very close proximity (less space) had a slower growth rate. However, birds with a generous amount of floor space (0.90 ft2/bird) had more variation in body weight. When the fast growing birds grow to their potential in a lower stocking density situation, they may possibly dominate the slower growing less aggressive birds at the feeder. Low stocking densities appear to allow for different growth rates within the flock and therefore lower flock uniformity.

Production in the 0.45 ft2/bird treatment was 17.4 kg/m2 higher than in the 0.75 ft2/bird treatment. Although this high density is not within the range of the optimum floor space determined by Ringer (1971), this would result in an increased gross return of $20.88/m2 at a price of $1.20/kg (live). (Stocking densities at this level are not currently approved by the code of practice for broiler production.)

Implications for heat production
The heat production of broilers is significant, and more of an issue at higher stocking densities. Heat must be removed from the bird to avoid heat stress as a result of elevated temperature in the bird's microclimate. As a result birds can become less active and consume less feed and water (Deaton 1967). High temperatures can result in decreased live weight gain over the broiler cycle.

Feed consumption

prcn0802_fig4.gif - 4.09 K
Figure 2 summarizes the feed consumption of the birds in this trial. High stocking density did not decrease feed consumption relative to the lowest stocking density. Birds in the 0.75 ft2/bird treatment consumed significantly more feed (3183 g/bird) than birds in the 0.90 ft2/bird treatment (2993 g/bird). These birds also had the highest body weight. Average feed conversion (FCR = 1.71) was not affected by stocking density.

Carcass quality
Birds raised at the highest stocking density had a higher incidence of cellulitis (0.98%) compared to 0.47, 0.20, and 0.15 in the 0.60, 0.75 and 0.90 ft2/bird treatments, respectively. There was no significant effect of stocking density on mortality, breast yield, carcass grading or scratches.

Table 1: The positive and negative implications of increasing stocking density in a broiler barn

Pros
Cons
More production (gross income) per unit of floor area
No effect on mortality
Does not decrease percentage of scratches
Does not decrease breast muscle yield
Does not decrease percentage of Grade A
Lower final body weights
Requires more labour
Requires exceptional ventilation management
Well-being concerns (not approved in the code of practice)

J. J. R. Feddes, E. J. Emmanuel, R. H. McGovern*, and M. J. Zuidhof*
University of Alberta and Alberta Agriculture*


Poultry Research Centre News - Vol. 8 No. 2, May 1999
 
 
 
 
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This information published to the web on August 5, 1999.
Last Reviewed/Revised on July 23, 2007.