Manzano has alleged that he and other riders from the Kelme team were given drugs for dogs, cattle and horses when doctor Eufemiano Fuentes was part of the outfit.
He also implicated team manager Vicente Belda and trainer Jose Ignacio Labarta in the practice. Both are also in the dock.
Fuentes has been charged with his sister Yolanda and three other defendants from cycling teams in connection with a blood doping racket, with dozens of suspects in cycling and possibly other sports.
The five are accused of endangering public health but not incitement to doping, which was not a crime in Spain at the time of their arrests in 2006.
Manzano, who made similar accusations in a wide-ranging interview with Spanish sports daily AS in 2004, claims that his health was compromised by the substances given to him during his time with Kelme and recalled one occasion when he fainted during a stage of the Tour de France in 2003.
"I had taken oxyglobin intravenously, a haemoglobin for dogs (which increases oxygen levels in the blood), and Belda and Labarta knew, of course," Manzano said during evidence.
"I attacked (French rider) Richard Virenque on a stage and I began to feel progressively worse until I fainted. In the team they asked me to not say what I had taken nor to do a test because it was in France and we would all go to jail."
The court was told that Manzano had been pressured into taking the substances by the trio.
"I took the medication because it was compulsory in the team. I never did it voluntarily. If I report them here (in Spain), I am sacked. If I did it in France, then all of Kelme would go to jail."
Manzano also went on to describe the lengths the team went to prevent its riders from testing positive.
"They put a white powder on the penis to deteriorate the urine sample so that we didn't test positive for EPO," he said.
Fuentes, Labarta and Belda all deny endangering public health.