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Abstract
This study was conducted to compare pod and seed characteristics, nutritive value, digestibility and seed survival of intact medic pods after ingestion by sheep. Different diets comprising the intact pods of six cultivars of the medic species that are most widely sown in South Africa, viz. Medicago truncatula (Paraggio, Parabinga, Sephi and Cyprus) M. polymorpha (Santiago) and M. littoralis (Harbinger AR), were randomly allocated to 30 South African Mutton Merino wethers. Representative feed and faeces samples were collected daily and analysed for dry matter (DM), organic matter (OM) and crude protein (CP). Acid detergent fibre (ADF) and neutral detergent fibre (NDF) were also determined and apparent digestibility coefficients were subsequently calculated for DM, OM and CP. Pod and seed characteristics (pod and seed mass, seed to pod ratio, number of seeds per pod, hardseededness and seed recovered after ingestion) were determined. Medicago truncatula cultivars had the highest pod mass (71–91 mg) followed by M. littoralis (27 mg) and M. polymorpha (23 mg). The better seed:pod ratio of M. polymorpha (34%) and M. littoralis (30%), in comparison to the M. truncatula cultivars (18–28%), were associated with significant (PsO.05) differences in the number of seeds per 100 g of pods. This higher seed content of M. littoralis and M. polymorpha was also expressed in higher crude protein, digestible protein and digestible organic matter contents in pods. Medicago polymorpha had the highest (95%) and M. littoralis the lowest level of hardseededness (86%). Medicago polymorpha (23%) was superior to the other cultivars in terms of seed recovered after ingestion by sheep, followed by M. littoralis (9%) and M. truncatula cultivars (4%). This study showed that M. polymorpha (cv. Santiago) is best suited for utilization by sheep during the summer months when medic pods are the major component of their diet.
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