Abstract:
Shortage of quality feed is the major constraint in livestock production particularly under
smallholder subsistence farmer’s conditions in sub-Saharan Africa, including South Africa.
This is due to the fact that livestock production under smallholder subsistence farmers
predominantly depends on communal grazed natural pastures which are often inadequate in
both quality and quantity particularly during the dry season. In order to improve livestock
production in these areas, there is a need to address shortage of feed both in terms of quantity
and quality. Consequently cowpea (Vigna unguiculata (L.) Walp.) varieties adaptable in
Limpopo province of South Africa were evaluated for their nutritive value and in vitro gas
production (fermentation) attributes in order to identify superior varieties as potential forage
source for ruminants animals.
Several laboratory experiments (including proximate analysis, in vitro digestibility estimate
and gas production) were conducted at the University of Pretoria, South Africa. In this study,
12 varieties of cowpea were evaluated for their chemical composition, in vitro organic matter
digestibility and gas production (fermentation) attributes. Generally the adaptable varieties
had more than 15% crude protein (CP) content with relatively low neutral detergent fibre
(NDF), thus they were highly digestible. This indicates that these varieties could be
potentially utilised as supplementary forage and nitrogen source to complement poor quality
forage. However, of the 12 varieties, three, Bechuana white, IT 97K-499-35 and TX 08-30-1
were relatively superior as they had greater CP, ME and IVOMD with low fibre values.
Hence, these three varieties are chosen for further evaluation in terms of their potential in
improving ruminal fermentation and digestibility of poor quality grass hay when used as supplement at three different levels of inclusion. This was done by conducting an in vitro gas
production experiment and measuring parameters such as, ruminal fermentation, in vitro
organic matter digestibility and NDF degradability of forage. Generally supplementing poor
quality grass hay with cowpea varieties improved grass hay fermentation. Among the cowpea
varieties, high levels of inclusion resulted in greater gas production for Bechuana White and
IT 97K-499-35, while for TX 08-30-1 variety, there was no difference between 15 vs 30 % or
50% inclusion level. Thus Bechuana White and IT 97K-499-35 can be used as a forage
source while TX 08-30-1 varieties can be recommended as a protein source to supplement
poor quality forage. However, there is a need to determine their dry matter intake,
digestibility and animal performance response in order to utilise them in the feeding system
of ruminants. In vitro supplementary results to poor quality forage suggests that thirty percent
level of inclusion of the two cowpea varieties (Bechuana White and IT 97K-499-35) has the
maximum benefit.
