. 2019 Dec 11;93(6):1301–1317. doi: 10.3382/ps.2013-03614

Table 5.

Effect of diseases on production performance under different animal welfare (AW) concepts compared with the healthy baseline situation (bolded data indicate that under particular AW concepts the effect of the disease is changed compared with the conventional system)

	Input variable
Production system/disease	Mortality (% flock)	Daily weight gain (g/d)	Weight at delivery (g)	Feed conversion ratio (g/g)	Condemnation rate at slaughter (% flock)
Conventional
Baseline situation	4.00¹	54.88¹	2,250¹	1.75¹	0.00
Infectious bronchitis (IB)	5.00²	52.38²,³	2,193²	1.75²	0.50⁴
Infectious bursal disease (IBD)	4.12⁵	52.50³	2,205⁶	1.77⁶	0.00
Coccidiosis	4.00⁷,⁸	51.99⁷,⁸	2,080⁹	1.87⁷,⁸	0.00
Coccidiosis with preventive drugs	4.00⁷,⁸	53.70^7,8,10	2,008¹⁰	1.82¹⁰	0.00
Escherichia coli	4.44¹¹	51.62³	2,168¹²	1.88¹²	0.00
Necrotic enteritis (NE)	4.82¹³	52.90³	2,222¹³	1.82¹³	1.36¹³
Leg problems	4.91¹⁴,¹⁵	44.00¹⁶	1,848¹⁷	1.78¹⁸	0.30¹⁴
Ascites	4.66¹	54.88	2,250	1.75	0.26¹⁹
Sudden death syndrome (SDS)	4.22¹	54.88²⁰	2,250²⁰	1.75²⁰	0.00
Volwaard
Baseline situation	1.50¹	41.07²¹	2,300²²	2.09²²	0.00
IB	1.59¹	29.98²	2,243²	2.09²	0.50⁴
IBD	1.62²³	40.25²¹	2,254⁶	2.11⁶	0.00
Coccidiosis	1.50⁷,⁸	38.92²⁴	2,180⁹	2.21²⁵	0.00
Coccidiosis with preventive drugs	1.50⁷,⁸	40.21²⁴	2,252¹⁰	2.16¹⁰	0.00
E. coli	1.59¹¹	40.77²¹	2,283²⁶	2.15²⁶	0.00
NE	2.32¹³	40.57²¹	2,272¹³	2.16¹³	1.36¹³
Leg problems	1.50¹	34.00¹⁶	2,151¹⁶	2.11¹⁸	0.30¹⁴
Ascites	1.57¹	41.07	2,300	2.09	0.05¹⁹
SDS	1.54¹	41.07²⁰	2,300²⁰	2.09²⁰	0.00
Better Life 1*/Puur & Eerlijk
Baseline situation	1.50¹	41.07²¹	2,300²²	2.09²²	0.00
IB	1.59¹	29.98²	2,243²	2.09²	0.50⁴
IBD	1.62²³	40.25²¹	2,254⁶	2.11⁶	0.00
Coccidiosis	1.50⁷,⁸	38.92²⁴	2,180⁹	2.21²⁵	0.00
Coccidiosis with preventive drugs	1.50⁷,⁸	40.21²⁴	2,252¹⁰	2.16¹⁰	0.00
E. coli	1.59¹¹	40.77²¹	2,283²⁶	2.15²⁶	0.00
NE	2.32¹³	40.57²¹	2,272¹³	2.16¹³	1.36¹³
Leg problems	1.50¹	34.00¹⁶	2,151¹⁶	2.11¹⁸	0.30¹⁴
Ascites	1.57¹	41.07	2,300	2.09	0.05¹⁹
SDS	1.54¹	41.07²⁰	2,300²⁰	2.09²⁰	0.00
Better Life 2*
Baseline situation	1.50¹	37.50²¹	2,100²²	2.15²²	0.00
IB	1.59¹	32.11²,²¹	2,043²	2.15²	0.50⁴
IBD	1.62²³	36.75²¹	2,058⁶	2.17⁶	0.00
Coccidiosis	1.50⁷,⁸	35.92²⁴	2,012⁹	2.27²⁵	0.00
Coccidiosis with preventive drugs	1.50⁷,⁸	37.21²⁴	2,084¹⁰	2.22¹⁰	0.00
E. coli	1.59¹¹	36.45²¹	2,041²⁶	2.21²⁶	0.00
NE	2.32¹³	37.00²¹	2,072¹³	2.22¹³	1.36¹³
Leg problems	1.50¹	32.92¹⁶	1,951¹⁶	2.17¹⁸	0.30¹⁴
Ascites	1.57¹	37.50	2,100	2.15	0.05¹⁹
SDS	1.54¹	37.50²⁰	2,100²⁰	2.15²⁰	0.00
Better Life 3*/Skal
Baseline situation	3.00²⁷	34.57²¹	2,800²⁷	2.75²⁷	0.00
IB	3.09¹	25.55²	2,743²	2.75²	0.50⁴
IBD	3.12²³	33.88²⁸	2,744⁶	2.78⁶	0.00
Coccidiosis	3.00⁷,⁸	30.25²⁴	2,450⁹	2.87²⁵	0.00
Coccidiosis with preventive drugs	3.00¹¹	31.23²⁸	2,530²⁹	2.84²⁹	0.00
E. coli	3.09¹¹	34.16²⁸	2,767²⁶	2.88²⁶	0.00
NE	3.82¹³	34.22²⁸	2,772¹³	2.82¹³	1.36¹³
Leg problems	3.00¹	31.00¹⁶	2,651¹⁶	2.76¹⁸	0.30¹⁴
Ascites	3.00¹	34.57	2,800	2.75	0.00¹⁹
SDS	3.00¹	34.57²⁰	2,800²⁰	2.75²⁰	0.00
Organic
Baseline situation	2.80²⁷	37.14²¹	2,600²⁷	2.63²⁷	0
IB	2.89¹	36.16²,³⁰	2,453²	2.63²	0.5⁴
IBD	2.97¹,²	36.40³⁰	2,548⁶	2.66⁶	0.00
Coccidiosis	2.80⁷,⁸	31.50²⁴	2,205⁹	2.75²⁵	0.00
Coccidiosis with preventive drugs	2.80¹¹	32.64²⁸	2,285²⁹	2.72²⁹	0.00
E. coli	3.89¹¹	36.67³⁰	2,567²⁶	2.76²⁶	0.00
NE	3.62¹³	36.74³⁰	2,572¹³	2.70¹³	1.36¹³
Leg problems	2.80¹	33.00¹⁶	2,451¹⁶	2.64¹⁸	0.30¹⁴
Ascites	2.80¹	37.14	2,600	2.63	0.00¹⁹
SDS	2.80¹	37.14²⁰	2,600²⁰	2.63²⁰	0.00

Van Horne et al. (2003).

Mortality increases by 25%, daily weight gain decreases by 27%; weight at delivery decreases by 57 g; no effect on feed conversion (Yohannes et al., 2012). No difference in impact under AW concepts.

Calculated based on weight at delivery: growth/g per d = weight at delivery/42 d.

⁴

Condemnation rate of 0.5%. No change is assumed under AW concepts (Lasher and Shane, 1994).

⁵

Mortality increases by 3% in conventional systems (Müller et al., 2003).

⁶

Weight at delivery is 2% less; feed conversion increases by 1% (McIlroy et al., 1989).

⁷

No mortality due to coccidiosis; daily growth decreases by 1.32 g; weight at delivery is 100 g less, feed conversion increases by 0.1 (Voeten et al., 1988).

⁸

No mortality due to coccidiosis; daily growth decreases by 5%; feed conversion increases by 2% (Graat et al., 1998).

⁹

Weight at delivery under coccidiosis = average growth/g per d × production days.

¹⁰

Due to coccidiostat, weight at delivery improved to 72 g and the feed conversion decreased by 0.05 compared with the situation in which no vaccination was applied (Wheelhouse et al., 1985).

¹¹

Mortality under conventional system is 0.26 to 0.62. The average of the 2 seasons is 0.44 (Van Horne et al., 2003). Mortality under the AW concept is 0.09.

¹²

Weight at delivery in conventional system is 83 g less; feed conversion was increased by 0.32 g between d 49 to 66, which suggests an increase in feed conversion for approximately 16 d. Accounting for the length of the production round in the conventional system, the feed conversion ratio is estimated at 1.88 g/g, i.e., 16 d × (1.75 g/g + 0.32 g/g) + 24 d × 17.5 g/g (Bhushan et al., 2008).

¹³

Mortality increases by 0.82%; weight at delivery is 28 g less; feed conversion increases 0.071, condemnation rate is 1.36% (Lovland and Kaldhusdal, 2001). Under AW concepts, the same effect is assumed as in conventional systems.

¹⁴

Increase in mortality due to leg problems is 0.8%; condemnation rate is 0.3% (Verma, 2007).

¹⁵

Increase in mortality is 1.1% (Sullivan, 1994).

¹⁶

In the study of Yalçin et al. (1998) the daily growth was 7 g less due to leg problems. Hereby, chickens without are compared with those with gait score (GS) 1. The effect in case of GS greater than 3 can be higher, which is also assumed in this study. A decrease in daily growth of 7 g is applied in case of Volwaard, Better Life 1*, and Better Life 2*. The decrease for conventional systems is assumed to be 10 g/d. The decrease for organic and Better Life 3* is assumed to be 4 g/d. Due to the provision of a free-range area, a slower-growing breed, a lower stocking density, and a natural day-night regimen, the number of birds with GS 4 and 5 decreases.

¹⁷

The effect on daily growth is the same for the rest of the production round, which means that the weight at delivery is calculated by multiplying the daily growth by the number of production days.

¹⁸

Chickens with leg problems eat the same quantity (Weeks et al., 2000). However, these chickens lose weight, which results in a higher feed conversion. Su et al. (1999) calculated the feed conversion for chickens with and without GS 4 and 5. The average feed conversion for chickens with GS 4 and 5 was 0.03 lower than that in the situation without leg problems. With improved welfare, the severity of leg problems decreases. It is assumed that leg problems are the most severe in the conventional system, which indicates that leg problems have the highest effect on feed conversion in conventional systems (feed conversion is lower with 0.03). In Volwaard, Better Life 1*, and Better Life 2*, the feed conversion was 0.02 lower and in Better Life 3* and organic systems it was 0.01 lower compared with the situation without leg problems.

¹⁹

Condemnation rate for conventional is 0.26%. Condemnation rate for AW concepts is 0.05%. However, no ascites are assumed for organic and Better Life 3* systems, which means that the condemnation rate under these concepts is zero (Herenda and Jakel, 1994).

²⁰

No effect apart from mortality (Julian, 2005).

²¹

Calculated based on weight at delivery: growth/g per d = weight at delivery/56 d.

²²

Ellen et al. (2012).

²³

Mortality due to IBD increases similarly under AW and conventional systems (+0.12). This results in a relative increase in mortality due to IBD, which corresponds to the findings of Van Horne et al. (2003).

²⁴

Voeten et al. (1988) found that chickens could recover from an infection of coccidiosis in 35 d, which means that its effect on performance was eliminated. It is assumed that the chicken grows at a slower rate for 35 d, and for the rest of production period, a healthy growth rate is calculated. The following formula calculates the average growth: average growth/g per d = [35 d recovery × (growth healthy – negative effect coccidiosis) + rest of the production period × growth healthy]/total production days. Under Volwaard, Better Life 1*, and Better Life 2*, the daily growth decreases by 4 g/d lower during the recovery period of 35 d. Under Better Life 3* and organic, the daily growth decreases by 11 g/d, because the free-range area infection with coccidiosis and the probability of picking up more oocysts increase.

²⁵

Subclinical coccidiosis is primarily expected in a conventional system. A light infection level is assumed in Volwaard, Better Life 1*, and Better Life 2* because the chickens have access to free range. A moderate infection level is assumed in Better Life 3* and organic systems because the use of anticoccidial drugs is prohibited (Reid and Johnson, 1970; Voeten et al., 1988).

²⁶

Effect of E. coli is decreased due to a lower stocking density, breed, and fewer stress factors. However, there is an increase due to the free-range area. The relative decrease in mortality is calculated (80%) according to Van Horne et al. (2003). The effect under the AW concepts is decreased by 80% compared with that under conventional system. However, in case of organic and Better Life 3* concepts, the free-range area is not covered and the water may remain there, which could serve as a good reserve for E. coli. Therefore, the effect of E. coli for these concepts is decreased by 60%.

²⁷

Vermeij and Van Horne (2008).

²⁸

Calculated based on weight at delivery: growth/g per d = weight at delivery/81 d.

²⁹

Due to vaccination against coccidiosis, weight at delivery improved to 80 g and the feed conversion decreased by 0.03 compared with the situation in which no vaccination was applied (Vermeulen et al., 2001).

³⁰

Calculated based on weight at delivery: growth/g per d = weight at delivery/70 d.