Complex sentence: He acquired a flock of the then rare Southdowns from John Ellman of Glynde, Sussex and bred them to produce a strain of larger size, earlier maturity and improved fleece quality.
Split into simpler sentences: He acquired a flock of the then rare Southdowns from John Ellman of Glynde, Sussex. He bred his flock to produce an improved breed of larger size, earlier maturity and improved fleece quality.