Acacia karroo, like many Acacia species in Southern Africa, is a valuable source of forage for ruminants, particularly during dry periods, when it can provided a significant supply of protein compared to other available forages (Brown et al., 2016; Ngambu et al., 2013; Mapiye et al., 2011; Aganga et al., 2000). However, the presence of thorns and tannins limits its consumption and their adverse effect can be alleviated by feeding young sprouts or leaf meal (Brown et al., 2016; Mapiye et al., 2011).
Digestibility
The DM digestibility and particularly the protein digestibility of Acacia karroo are relatively low compared to those reported for similar browse plants, which may be explained by the presence of phenolic compounds and more specifically condensed tannins (Mapiye et al., 2011; Aganga et al., 1998)..
Beef cattle
For beef production, Acacia karroo leaf meal can be mixed with locally available feed energy sources such as rangeland hay or chopped crop residues, before being distributed into troughs in pens or distributed in the rangeland. It can also be fed to steers each morning before they graze poor quality forages. Alternatively, dried leaves can be ground and used in home based or commercial rations (Mapiye et al., 2011).
Grazing steers (3 to 19 months old) supplemented with Acacia karoo leaf meal, in such a way to insure a supply of 150 g of protein, showed higher body condition score, average daily gain, slaughter weight, cold and warm carcass weights than those that were not supplemented. They also showed increased blood concentrations of total protein, albumin, urea, non-esterified fatty acids, P, Ca, Mg and Fe. Supplementing steers with Acacia karroo leaf meal, rather than supplementing them with sunflower cake or not supplementing them, increased meat protein content, and proportions of α-linolenic acid and its derivative docosapentaenoic acid in meat. In these studies, the growth performance of steers supplemented with Acacia karoo leaf meal remained lower than those of steers supplemented with sunflower cake ( (Mapiye et al., 2009a; Mapiye et al., 2009b).
Goats
Acacia karroo leaves are used to supplement grazing goats, or goats fed with low quality forage (Brown et al., 2016). Goats fed alfalfa hay and supplemented with fresh Acacia karroo leaves included at 40% showed higher growth rates, lower meat pH, higher meat tenderness and higher meat juiciness than goats not supplemented with Acacia karroo (Ngambu et al., 2013; Ngambu et al., 2012). Goats fed a mixture of fresh Acacia karroo sprouts and alfalfa showed a higher average daily gain than goats fed a mixture of lucerne hay and commercial pellets at a feeding level of 3% of body weight. The protein content of fresh Acacia karroo sprouts was higher than that of commercial pellets and the composition of the diets was calculated to meet the metabolizable energy requirements of goats (Nyamukanza et al., 2008).
Control of gastro-intestinal parasites
Acacia karroo foliage has anthelmintic properties in ruminants when fed with at an inclusion rate around 40-50% (Brown et al., 2016; Marume et al., 2012, Mapiye et al., 2011; Xhomfulana et al., 2009; Kahiya et al., 2003). Total fecal egg counts and Haemonchus contortus or Oesophagostomum colombianum worm burdens decreased in grazing steers supplemented with Acacia karroo leaf meal compared with non-supplemented steers or steers supplemented with sunflower cake diet (Xhomfulana et al., 2009). A decrease in fecal egg counts and worm counts was observed in kids infected with Haemonchus contortus larvae and given Acacia karroo whereas the infection progressed in kids not fed Acacia karroo (Marume et al., 2012). The anthelmintic properties of Acacia karroo have been attributed to its high content in condensed tannins and not to other polyphenols. For instance, though it contains less polyphenols than Acacia nilotica, Acacia karoo had higher anthelmintic properties in goats than Acacia nilotica and most of its polyphenols are in the form of condensed tannins (Kahiya et al., 2003).
