The study, which was carried out independently by Scotland’s Rural College (SRUC), compared the health, welfare and production characteristics of three fast growing breeds with a commercially available slower-growing breed.

It found that the fast growth rate breeds of birds (referred to as ‘conventional breeds’) were up to three times more likely to suffer from lameness and demonstrated a distinct lack of activity and behavioural expression, when compared to the slower-growing breed.

Read the full report here.

Key findings

Conventional breeds are inactive from a young age

The trial showed that birds from the conventional breeds became inactive from as young as 9 days of age. By 37 days, they spent around three quarters of their time sitting down doing nothing, compared to 51% of time for the slower-growing breed. Click to view chart here.

Conventional breeds also halved their time standing in just 2 weeks (from more than 10% at 16 days, to less than 5% at 37 days), and reduced their walking (from less than 5% at 9 days, to around 1% at 37 days). By comparison, birds of the slower-growing breed spent around 13% of their time walking and standing at 37 days.

Conventional breeds have poorer physical condition

Hock burn: Conventional breeds were shown to sit more and therefore spent more time in contact with the litter. The condition of their hocks and feathers was therefore poorer. Only 23.5 to 40.7% of the conventional birds had healthy hocks (score 0), compared to more than 80% of the slower growing birds. Click to view chart here.

Dirty feathers: More than 80% of the conventional birds had dirty breast feathers (score 2) compared to ~30% for the slower-growing birds. In addition, around 30% of the slower-growing birds had clean breast feathers. Click to view chart here.

Poorer breast feather cleanliness and fewer healthy hocks in the conventional breeds occurred despite using more wood shavings over the course of the trial to keep the litter dry and friable: around 24kg of additional wood shavings were required in the pens of the conventional breeds, compared to 14.5kg for the slower-growing breed.

Conventional breeds are restricted in their behaviour

Perching: Perching is important for birds to rest undisturbed and lift them off the litter. Conventional birds spent little time perching, peaking at around only 3% at 16 days of age, compared to a peak of around 12% at day 30 for the slower-growing breed. Click to view chart here.

Comfort behaviours: Behaviours such as dust bathing are important for maintaining feather condition and are a sign of positive wellbeing. However, the conventional breeds spent significantly less time dust bathing, peaking at 16 days. By contrast, the slower-growing birds continued to increase this activity up to 37 days (the last day of the observation period). Click to view chart here.

Conventional breeds are selected for high production

As expected, the conventional breeds had a higher average daily live weight gain and lower feed conversion ratio than the slower-growing breed. On average, conventional breeds grew at 63g per day (up to 2.2 kg), compared to 46g per day for the slower-growing breed (approximately 26% slower).

Feed conversion ratio for each breed was 1.46, 1.43 and 1.35 for Breeds A, B and C, respectively, compared with 1.76 for the slower-growing breed. Overall, birds from the slower-growing breed ate approximately 21% more feed than birds from the conventional breeds to reach the same body weight and took an average of 14 days more to reach that weight.

All birds were slaughtered at 3kg. Average carcase weight was not different between the slower-growing breed and conventional Breeds A and C; Breed B however had a significantly lighter carcass weight.

Average breast meat yield was not different between the slower-growing breed and Breed B, however, both had significantly lighter breast weights compared to Breeds A and C.

The slower-growing breed had significantly more leg meat yield than the conventional breeds by around 100g.

Selective breeding for fast growth, high breast meat yield and feed efficiency has led to a multitude of welfare problems in the conventional breeds, such as poor physical condition, low activity and lack of behavioural expression, as detailed above.

The RSPCA trial also confirmed the impact of such selective breeding practices on mortality, walking ability and muscle health in the conventional breeds.

Conventional breeds had higher mortality rates

Overall mortality (dead and culled birds) was higher in Breeds A and B (around 11%) than the slower-growing breed (5.2%) and conventional Breed C (6.8%). Click to view chart here.

Conventional breeds had poorer walking ability

Birds of the slower-growing breed had significantly better walking than all three conventional breeds and was the only breed with a proportion (13%) of gait score 0 (best walking).

Overall, the distribution of gait scores leaned towards the better end of the scale for the slower-growing breed birds and the poorer end of the scale for the conventional breeds. Click to view chart here.

Conventional breeds had higher rates of muscle disease

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