Investigating factors affecting the incidence of tibial dyschondroplasia in meat-type poultry: A meta-analysis

Tibial Dyschondroplasia (TD) is the accumulation of growth plate cartilage in the proximal end of the tibiotarsus bone and has persisted as a major skeletal disorder in the poultry industry, continuing to negatively impact both profitability and animal welfare. Studies have reported potential effects of genetic selection, nutrition, and body weight on TD incidence, but these relationships vary between studies. Therefore, the objective of this study was to conduct a meta-analysis, to identify factors contributing to TD incidence, with 41 publications meeting the inclusion criteria. It was predicted that variables such as body weight (kg), sex, species, age (weeks), dietary calcium to phosphorus ratio (Ca:P), feed conversion ratio (FCR), and the decade of publication would have an impact on the incidence of TD. Linear mixed models were used to assess the effect of independent variables to predict TD incidence while including study as a random effect. Results indicated that increased body weight (0.13 ± 0.028; P < 0.0001) was associated with a higher TD incidence. TD incidence varied by species (P < 0.0001), with a greater effect observed in turkeys (0.16 ± 0.027; P < 0.0001) compared to broilers (0.10 ± 0.140; P = 0.475). In broilers, TD incidence decreased with age (P < 0.0001), with a slightly steeper decline in females (-0.28 ± 0.066; P < 0.0001) compared to males. The decade of study (70s-80 s, 90 s, and 2000s-2020s) was associated with TD incidence (P = 0.041), with incidence at its lowest in the 2000s-2020s (0.19 ± 0.044; P < 0.0001), and highest in the 70s-80s (0.37 ± 0.052; P = 0.028). An increase in the Ca:P ratio corresponded to a larger decline in TD incidence in broilers (-0.99 ± 0.158; P < 0.0001) compared to turkeys (-0.57 ± 0.217; P = 0.011). However, improved FCR (-1.37 ± 0.345; P < 0.0001) was correlated with increased TD incidence. To conclude, this meta-analysis identified factors related to TD incidence and emphasized the need for tailored management strategies to mitigate impact.