They are discussing the effect so protein intake on modifying the toxic effect so aflatoxin on the liver. I have mentioned aflatoxins before. Aflatoxins are damaging to the liver and are known for causing liver cancer in immune suppressed people.
They found that in the rat studies that when the rats were high doses of casein (milk protein) during the dosing of aflatoxin that they did not develop much in the way of liver damage. When the high doses of casein were given after the rats were given the aflatoxin there was a 6 fold increase in the damage to the liver.