A comparison of pod and seed characteristics, nutritive value, digestibility and seed survival in cultivars from different Medicago species fed to sheep

Abstract

This Study was conducted to compare pod and seed characteristics, nutritive value, digestibility and seed suvival 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 (71–91mg) followed by M. littoralis (27mg) and M. polymorpha (23mg). 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 (P ≤ 0.05)differences in the number of seeds per 100g 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 (23%) was superior to the other cultivars in terms of seed recovered after ingestion by sheep, followed by M. littoralis (9%) M. truncatula cultivars (4%). This study showed that M. polymorpha (cv. Santiago) is best suited for utilisation by sheep during the summer months when medic pods are the major component of their diet.

Keywords: botany; characteristics; cultivar; digestibility; grazing; Medicago littoralis; Medicago polymorpha; Medicago truncatula; pods; seed; seed recovery; sheep; South Africa; southwestern Cape; summer grazing; survival

African Journal of Range and Forage Science 1995 12(1): 11–15