( ( ( The ( last ( six weeks ) ) ) ( of gestation ) ) ( ( is ( ( the period ) ( of ( ( rapid growth ) ( of ( the ( fetal lambs ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ last) (CD six) (NNS weeks)) (PP (IN of) (NP (NN gestation)))) (VP (VBZ is) (NP (NP (DT the) (NN period)) (PP (IN of) (NP (NP (JJ rapid) (NN growth)) (PP (IN of) (NP (DT the) (JJ fetal) (NNS lambs))))))) (. .)))
The last six weeks of gestation is the period of rapid growth of the fetal lambs.
(ROOT (S (NP (DT The) (JJ fetal) (NN period)) (VP (VBZ lasts) (NP (NP (QP (RB approximately) (CD 30)) (NNS weeks)) (NP (NNS weeks)))) (. .)))