Written by Emiliano Videla; edited by Maëva Manet. 

Nowadays, the poultry industry breeds two types of commercial broilers: faster and slower growing breeds. The main difference between them is the time needed to reach slaughter weight (the weight at which there is enough meat to be sold on the market). Even though faster growing breeds represent the majority of broilers being used in the poultry industry, some health and welfare issues have been identified, leading the industry to broaden into breeding more slower growing breeds. These issues are closely related to the broilers’ weight, affecting their ability to move, together with decreased levels of activity. In contrast, the way the slower growing breeds gain weight is not so abrupt, and as a consequence, they often have better health and welfare indicators. Taking these facts into consideration, the author, Dr Laura Dixon, was determined to compare the welfare and behaviour of three commercial faster growing breeds with a slower growing breed.  

The study was carried out at Scotland’s Rural College. A total of 1600 birds, 400 hundred broilers from four breeds (3 x 400 faster growing birds / 1 x 400 slower growing birds) were used, distributed in pens of 50 birds of the same breed. So as to have the daily measurements of the birds’ activity, these pens were recorded 24 hours, once per week. The videos were used to measure the proportion of time spent feeding, drinking, foraging, dustbathing, perching, sitting, standing, in locomotion and preening. When studying animal behaviour, the measurement of daily activities is also known as time budget. In addition, the ability of broilers to walk towards a group of chickens was scored using a so-called gait score on a subset of 25 birds. The author used values from 0 to 5: scores from 0 to 2 represent no difficulties or slight difficulties to walk, without affecting the ability to move itself. Scores from 3 to 5 represent an impediment to walk, ranging from moderate to severe. According to the RSPCA welfare standards for chickens, birds with higher scores (e.g. 4-5) are considered to suffer too much and must be euthanised. Three indicators related to the birds’ welfare status were measured: feather coverage (based on a five-point score, ranging from fully-covered body to patches of bare skin); breast feather cleanliness (based on a three-point score, ranging from clean feather to patches of dirty feathers); and finally, thock lesions (based on a four-point score depending on the presence or absence, and, when present, its size and extension).   

As expected, slower growing broilers took two more weeks than the faster growing broilers to reach slaughter weight (53 vs. 38 days of age). The time budget of the slower growing broilers showed that they spent more time moving, foraging, preening, dustbathing and perching, and less time eating, drinking or just sitting compared to the faster growing breeds. The faster growing broilers spent the majority of the time sitting in the last days of growth. In terms of the ability to walk, the slower growing broilers had a higher proportion of individuals with a gait score ranging from 0 to 2, meaning that the ability to walk was not that much affected. The slower growing breed had better scores with all three welfare indicators, showing higher proportions of birds with fully feathered bodies, cleaner breast feathers, and absence of or presence of small and superficial lesions.  

The poultry industry is working towards establishing a balance between high productivity (short time to achieve a desired weight) and good welfare standards. However, it seems that gaining weight at a fast pace might affect the overall welfare, considering the rather plain time budget, the impaired ability to move and the poor welfare indicators in the fast-growing strains. The slower growing birds, on the other hand, showed an improved overall welfare status and spent more time performing a broader set of behaviours, especially highly-motivated behaviours – namely perching and preening. The perching behaviour, in particular, requires the chickens’ ability to keep their balance to avoid falling from the perch. Taken together, it could be possible that slower growing broilers are more willing and motivated to perform more behaviours, and that they are actually able to perform a wider range of behaviours than faster growing breeds as a consequence of experiencing less pain or discomfort thanks to the gradual weight gain.  

However, and even though the slower growing broilers are winning the welfare race, the author considers that: “they are still at a disadvantage to faster growing breeds in terms of most productive measures”, especially because faster growing breeds develop more breast meat, which is most popular among western consumers. More specifically, although meat from slower growing breeds can be sold at a higher price, which compensates for the extra expenses to produce them, in practice, very few people are aware of the existence of slower growing breeds – and among those who are, despite their good intentions, not all are paying the extra money for improved welfare. It would thus be desirable to increase the availability and visibility of products coming from alternative breeds that show better welfare and health indicators in spite of their “economical disadvantages”, in order to sensitise consumers to the cause of broiler welfare. 

REFERENCES. 

Dixon, Laura M. 2020. “Slow and Steady Wins the Race: The Behaviour and Welfare of Commercial Faster Growing Broiler Breeds Compared to a Commercial Slower Growing Breed.” PLoS ONE 15(4).