Question: when did factory farming start in the us
[{'answer': '1966', 'provenance': [{'wikipedia_id': '11469677', 'title': 'Intensive animal farming', 'start_paragraph_id': 6, 'start_character': 368, 'end_paragraph_id': 6, 'end_character': 372, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '11469677', 'title': 'Intensive animal farming', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 845, 'bleu_score': 0.9854535765681661, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5195029710457022010}, 'section': 'Section::::History.\n'}]}]