Nutritional Factors That Limit Livestock Production in Communal Areas

NAMIBIA’S northern communal areas (NCA) extend over nearly 185 000 square km (22% of Namibia’s land surface) and house approximately 1,2 million of its people (55%).

The vast majority of people are still dependent on traditional forms of agriculture (communal farming) for their livelihood.

Although originally subsistence-based, NCA agriculture is quickly transforming towards surplus production and profit-making.

However, livestock production is restricted by prohibition of animal and meat exports due to foot-and-mouth disease (FMD) zoning. Rainfall in the farming part of the NCA increases from 200 mmyear in the west (eastern Kaokoveld) to 650 mm in the east (Zambezi flood plains).

Ecologically, a recurrent fodder deficit and poor nutritive value of forage are perceived to limit livestock production in addition to man-made factors (e.g. exclusion from suitable meat and stud breeding markets, inability to access bank credit due to freehold land ownership, far distance to input suppliers, unstructured business environment, poor farm management skills) that will not be discussed in detail in this article. What can be done about the ecological factors that limit livestock production?

The most obvious reason for a recurrent fodder deficit would be overstocking per se or non-adaptive grazing methods.

The regional average carrying capacity of NCA rangelands in the dry season of 2011, based on conventional methods of clipping herbaceous standing yield, was 6,1 halarge stock unit(LSU).

The 201011 rainy season was about 10% above average and was followed by the most severe drought in a farming generation in 201112.

About 17% of the NCA area is inhospitable to vegetation, being hyper-arid (western Kaokoveld and northern Namib desert), salt pans, seasonally inundated wetlands or urban area, reducing the effective farming area to 154 000 square km.

It is estimated that NCA farmers hold 1,6 million cattle, 1,8 million goats, 400 000 donkeys and 250 000 sheep. This translates roughly to 2,4 million LSU of 450kg each, or an average regional stocking rate of 6,4 haLSU.

Compared to the 2011 carrying capacity, on a regional scale this hardly constitutes overstocking with too many grazing animals, although there are of course areas where this is the case, especially in the more fertile and palatable areas.

Thus far, institutions and society were unable to buffer the estimated 250 000 smallholder farmers in the NCA effectively against natural calamities.

Livestock populations are decimated to their ecological ceiling on a regular basis by natural events such as drought, floods, wildfires, outbreaks of locusts, termites and armyworm, etc.

The inability to bring livestock to conventional markets does not facilitate adaptive stocking responses by NCA farmers and many animals are needlessly lost to natural calamities.

One wonders why geographic zoning and isolation of FMD-prone regions persists when the commodity-based approach endorsed by the World Organization of Animal Health (OIE) allows the supervised participation of such regions in international trade.

Yet, most rangeland in the NCA is already degraded. In less utilized areas (e.g. inland areas without natural permanent drinking water), the trend of deterioration is accelerating rapidly (mainly because of the supply of drinking water by pipeline or drilling of boreholes).

Measured indicators of rangeland degradation include:

A canopy cover of the soil of only 80,8% in the west (poor soil canopy cover promotes erosion), 32,5% of all plants are woody, there are 4 292 11frasl2m-bush equivalentsha and 5 033 woody seedlingsha (high abundance of woody plants indicates bush encroachment), 45,9% of grasses are annual (indicating selective overgrazing of perennial grasses), only 17,7% of grasses are climax and 17,4% are decreaser species 48,3% of grasses are pioneer and 78,2% increaser II species.

The shift from grass to bush, from perennial to annual grass, from climax and decreaser to pioneer and increaser II grass species indicates that non-adaptive grazing methods that decimate desirable perennial grasses are the real cause of rangeland degradation in the NCA.

Declining nutritive value of forage is linked to the degradation of savanna grass swards.

In the NCA, only grass swards dominated by a variety of climax grass species are able to meet growing cattle’s growth requirement in the rainy season (seven percent dietary crude protein, CP and 55% digestibility of organic matter, DOM) and maintenance requirement in the dry season (five percent CP, 48% DOM).

Once the desirable perennial grasses are replaced by undesirable perennial grasses, nutritive value declines below what is required and animal production declines. Undesirable grasses usually also have a higher content of plant fibre, impeding the flow of nutrients through the digestive tract of ruminant animals.

When annual grasses and forbs take over the sward, there is a short-lived nutritional boost in the rainy season but, due to the non-persistence of annual grasses, starvation sets in during the dry season. Hungry grazers (cattle) increasingly turn to browse to sustain themselves but because they are ill-equipped to harvest and digest browsed forage, their production decline is not halted effectively.

The current practices of allowing livestock free access to the commonage, occupying it virtually continuously, and the attempted suppression of all fires (in some areas: unplanned over-frequent burning) expedite the deterioration of the grass sward, erosion of the topsoil and encroachment of invasive bush.

All elements of rangeland degradation: unfavourable changes in botanical composition, ground cover and nutritive value, can be reversed by adaptive rangeland management that is based on the rotational utilization of the grass sward during the rainy season, allowing desirable perennial grasses to seed before being re-grazed, and by rehabilitation of degraded rangelands.

Planned, hot fires integrated into the rotational grazing plan are the only “natural” means of controlling bush thickening (as opposed to chemical and mechanical control measures) on the landscape level. To attempt to alleviate the declining nutritive value of degraded grass swards by supplying energy- and protein-rich nutrient supplements (e.g. licks) is technically feasible but very expensive and does not address the root cause of the problem.

Nutritive problems that cannot be alleviated by improved rangeland management relate to the deficiency of certain minerals virtually throughout the NCA. Minerals derive from the soil and their occurrence in grasses is largely independent of species, i.e. rangeland condition.

The most widespread deficiencies of minerals in the NCA are of phosphorus (P) and of the micro-minerals copper (Cu), zinc (Zn), manganese (Mn) and iodine (I) on all sandy and leached soils (in Oshana, Ohangwena, northern Oshikoto, Kavango and Zambesi regions) and on the loamier soils with limestone outcrops in the west (Omusati region).

On the latter soils, the high calcium carbonate content of the diet induces a relative mineral deficiency in ruminant livestock. On the fertile, loamy and non-calcareous soils of the Kaokoveld (Kunene region) the P deficiency is less severe, but micro-nutrient deficiencies persist. On the sandy soils of the eastern NCA, selenium (Se) and magnesium (Mg) are also sporadically deficient.

These mineral deficiencies seriously depress animal productivity and fertility and are the underlying cause of many perceived health problems in the NCA. They can be overcome easily by targeted supplementation of P by licks and micro-minerals preferably by injection. A vitamin A deficiency is also suspected in the dry season.

Moreover, livestock in the NCA have a persistent salt hunger living in a sub-tropical area so that rock salt should always be available. However, rock salt is not a substitute for targeted mineral supplementation.

In summary, the nutritive factors that limit livestock production in Namibia’s NCA can be overcome by a combination of adaptive grazing management, rangeland restoration and region-specific mineral supplementation, which would also address the root causes of degradation-induced poor livestock productivity.

A summary of this work, funded by the Millennium Challenge Account Namibia (MCA-N) was presented to the Grassland Society of Southern Africa (GSSA).

Source : The Namibian