Despite her condition, Viva was a very affectionate chicken who purred and chirped contentedly in the comfort of our kitchen where we made her a bed by the stove. On nice days, we liked to sit with her outside in the grass where she would take great pains to steady herself and run through the yard on her wing tips before collapsing, resting, and starting over.
Already by the 1980s, broiler chickens weighed 4 pounds at 8 weeks old - more than 40 times their original hatching weight. The US Department of Agriculture bragged that if human beings grew that fast, "an 8-week-old baby would weigh 349 pounds." A study published in 2008 said that the growth rate of chickens had increased "by over 300 percent" in the past fifty years, resulting in "impaired locomotion and poor leg health." (Toby Knowles, et al. 2008. "Leg Disorders in Broiler Chickens." PLoS ONE Feb. 6: e1545)
It isn't only their legs. Poultry scientists in the 1990s warned that chickens "now grow so rapidly that the heart and lungs are not developed well enough to support the remainder of the body, resulting in congestive heart failure." (David Martin. 1997. "Researcher studying growth-induced diseases in broilers." Feedstuffs May 26: 6)