Three researchers focusing on alternative feed sources for goats and lambs received their PhD degrees in animal sciences from Stellenbosch University (SU) in South Africa. They investigated how plant by-products can enhance animal health and growth performance, the health value, and shelf life of meat produced from those animals fed these by-products.

Their research is part of ongoing efforts in SU’s Department of Animal Sciences to explore affordable, locally available, and easily accessible alternative feed sources that can sustainably enhance animal production and meat quality.

Prof Cletos Mapiye, an Associate Professor in Meat Science in the Department of Animal Science, supervised all three researchers. The researchers involved graduated in December 2022.

Dr Tulimo Uushona’s dissertation, titled Feeding value and bio-preservative potential of Acacia mearnsii leaf meal for lamb meat production and quality improvement, focused on using alternative feed resources in local feedlot mixes.

In South Africa, leaf meal from invasive black wattle (Acacia mearnsii) is considered a promising alternative source of slowly fermentable energy (that is, fibre) in animal feed. Leaf meal is made from dried, grounded leaves and twigs used as livestock feed.

Wheat bran (Triticum aestivum) is currently one of the main fibre sources in the diets of feedlot animals.

Dr Uushona’s main objective for her PhD was to evaluate whether there is value in substituting black wattle leaf meal for wheat bran in the finishing diets of lambs.

Black wattle trees have invaded approximately 10 million hectares and were planted on 110 000 hectares of land for timber and bark tannin production in South Africa. Finding new uses for black wattle plant material, including by-products from tree leaves as alternative animal feed, is receiving research attention.

Dr Uushona studied how easily digestible black wattle leaf meal was for the animals, whether they could absorb nutrients contained in it and what impact this alternative ingredient in their finishing diets had on meat production and quality.

Her study showed that adding up to 100 g/kg dry matter of black wattle leaf meal to the finishing diets enhanced nutrient digestibility, animal growth, and carcass attributes without affecting meat quality.

The findings also show that adding black wattle leaf meal up to 200 g/kg dry matter in lamb finishing diets improves meat fatty acid composition and tenderness. In addition, it extends the shelf life of lamb meat.

Black wattle leaf meal harvested in the hot and dry season (summer) had the most desirable nutritional and antioxidant profiles of the samples tested, making it a potentially suitable nutraceutical and preservative for ruminant production and meat preservation.

Nutraceuticals for animals refer to feed or part of feed that provides health benefits, including the prevention and treatment of a disease.

Dr Uushona, who comes from Namibia, says black wattle leaf meal should gain more value as a ruminant fibre source for meat production, and a preservative to enhance the shelf-life of meat products.

She considers black wattle leaf meal a promising cheaper source of fibre and bioactive compounds that can serve as meat preservatives. Dr Uushona says this plant by-product offers new commercial opportunities to the black wattle, feed and meat industries.

In his study, Dr Leo Mahachi considered the beneficiation of Sericea lespedeza or ‘poor man’s lucerne’ for intestinal worm control and the production and preservation of lamb meat.

Sericea lespedeza (Lespedeza juncea var. sericea) is a drought-tolerant legume which grows well in low-quality soils and water-scarce regions.

Dr Mahachi, who hails from Zimbabwe, investigated the effects of feeding incremental levels of this legume instead of lucerne (Medicago sativa L.).

His results show this legume could be used as a cheaper, locally adaptable source of nutrients and bioactive phytochemicals instead of lucerne, a commonly used fibre source in feedlot diets. These phytochemicals are the chemical compounds produced by plants.

Dr Mahachi recommends substituting this legume for lucerne up to 187,5 g/kg dry matter in lamb feedlot diets to improve growth performance and meat quality.

This legume can suppress helminths (intestinal worms) and enhance animal growth.

Sericea lespedeza occurs mainly in Asia, North America, Oceania, and Southern Africa and is native to Australia, China, India, Japan, and Taiwan. In South Africa, it grows in pastures on commercial farms. It also occurs along roadsides in the Eastern Cape, Free State, Gauteng, KwaZulu-Natal and Mpumalanga.

Dr Farouk Semwogerere, from Uganda, evaluated the nutrients and bioactive phytochemicals of industrial hemp by-products as potential feed ingredients and meat preservatives in chevon (goat) feedlot production systems.

He explored this feeding alternative in his study titled Nutrients and phytochemicals in hempseed (Cannabis sativa L.) cake: bio-availability and bio-efficacy for chevon production and quality enhancement.

In water-scarce countries such as South Africa, the availability of protein feed resources is a major limiting factor in small ruminant nutrition. The most common protein feed ingredient for feedlot goat production is soya bean meal.

Research into new or underused sources of feed that improve meat production and the shelf life of meat products is essential to ensure the sustainability of the ruminant industry, he points out. Among these options are hemp by-products (that is seed, oil, oilseed cake, hulls and leaves).

The legalisation of hemp production and demand for hemp products are anticipated to increase the global production of hemp and its by-products.

Hempseed cake, in particular, holds potential as a source of animal feed because it is high in crude protein and energy. In addition, it also contains bioactive phytochemicals that could be beneficial to the animals.

In his study, Dr Semwogerere fed Kalahari Red goats diets containing different ratios of hempseed cake and soya bean meal. Kalahari Red is one of the country’s most prominent indigenous commercial chevon breeds.

Castrated goats (aged four to five months) received one of five dietary treatments as part of this study. After a 42-day feeding trial, the animals were slaughtered and assessed for meat quality.

Dr Semwogerere evaluated the effects of feeding increasing levels of hempseed cake as a substitute for soya bean meal in the goats’ finishing diets on nutrient intake and digestibility, meat production and quality.

The findings indicate that hempseed cake can be included in goat finisher diets up to 100 g/kg dry matter to enhance the nutrient digestibility, growth performance, health value, volatile flavour profile and shelf life of chevon without influencing meat colour.

He recommends that producers use hempseed cake as an alternative protein and bioactive source to enhance chevon production, health value, desirable volatile flavour compound profile and protein shelf life.

The findings suggest that hempseed cake could replace up to 100% of soya bean meal in local goat finishing diets without negatively affecting chevon production and quality.

The marketing of chevon from goats raised on hempseed cakes could develop into a particular niche market, Dr Semwogerere points out.

For media queries:
Prof Cletos Mapiye Department of Animal Science, Stellenbosch University
+27 21-808-2640