Broiler Chickens On-Farm Welfare Assessment: Estimating the Robustness of the Transect Sampling Method

Abstract

Assessing commercial broiler chickens' welfare usually comes at the cost of reduced precision due to the large flock sizes and required time commitments. The transect method for on-farm welfare assessment is conducted by walking within delimited paths between feeder and drinker lines within the commercial house, referred to as transects. This non-invasive method is conducted by detecting birds with signs of impaired welfare indicators, which include leg problems, sickness, body wounds, and feather dirtiness. The transect method has been validated for commercial turkey flocks but not for broiler chickens due to the large flock sizes. The aim of this study was to evaluate the robustness of the transect method in broiler chicken flocks through a capture–recapture approach of a known subpopulation of 80 birds. Groups of 10 chickens were captured and individually marked in eight locations of the house. Two observers collected the number and position of the detected marked birds while walking along non-adjacent transects (four samplings/house/day) during the two following days. Detection and repetition rates per house, and within transects, were calculated, as well as the effects of flock density, transect number/house (six vs. eight), and sampling time (morning vs. afternoon). The number of traveled transects was calculated for birds detected more than once, and the population random distribution was tested by comparing the number of observed and expected birds/transect. Results showed more than 64% of detection rate with a repetition rate/house sampling of 24% and per transect of 1.66%. Higher repetition rates in six-transect houses and during morning samplings were detected. The number of traveled transects was higher in eight-transect houses and from birds first detected at walls, indicating longer traveled distances in wider houses. In addition, bootstrapping techniques were used to calculate the optimal sampling effort. Our findings indicate that the lowest repetition rates and optimal sampling can be achieved by assessing two transects, being one wall and one central, separated by three transects in between. Such sampling procedure would provide robust results for welfare assessment of commercial broiler chicken flocks.

On-farm welfare assessment of commercial Pekin ducks: a comparison of methods

“…When using fewer transects is advisable that the transects used be spread across the farm to decrease the likelihood of double counting birds as they move across transects, and that transects of the same dimensions be used to the extent possible. It should be noted that as in previous work ( Marchewka et al., 2013 , Marchewka et al., 2015 , 2019 ; BenSassi et al., 2019a , BenSassi et al., 2019b ), drinkers and feeders were used as transect delineators in the present study. However, unlike in previous studies, the lines and feeders were not equally distributed resulting in transects of varying widths.…”

“…Rather than inspecting a subsample of birds, assessors walk the length of the barn back and forth along predetermined paths and record all incidences of birds that show welfare impairments. The TW method has been identified as a viable strategy for evaluating from a distance the welfare of broilers ( Marchewka et al., 2013 ; BenSassi et al., 2019a , BenSassi et al., 2019b ) and turkeys ( Marchewka et al., 2015 , Marchewka et al., 2019 ; Ferrante et al., 2018 ) and has been incorporated into the AWIN Welfare Assessment Protocol for Turkeys ( AWIN, 2015 ).…”

Developing a novel welfare assessment tool for loose-housed laying hens – the Aviary Transect method

“…The Aviary Transect method was based on the routine checks performed daily by egg producers combined with the established methodology from broiler and turkey transect walks ( Marchewka et al, 2013 , 2015 ; BenSassi et al, 2019a , b , c ). When applying transects sampling methodology, the entire flock is observed, and the frequency of birds falling within each predefined welfare indicator are scored ( Marchewka et al, 2013 ).…”

Evaluation of Welfare in Commercial Turkey Flocks of Both Sexes Using the Transect Walk Method

“…In the last decade, increased attention has been directed toward the welfare of commercial poultry and its assessment. Not only the awareness of the public, but also of farmers and stakeholders, is increasing due to the obvious impact of animal welfare issues on production [ 1 , 2 , 3 , 4 ].…”

“…On the other hand, the transect walk method has proven to be practical, reliable, and efficient without the need to catch birds or subject the flock to excessive stress. The method has been used successfully in large flocks of broilers [ 1 , 2 , 3 ]. and in turkeys [ 7 , 8 , 9 ].…”