**3. Nutritive value of some underutilised forage crops**

#### **3.1. Evaluation of the nutritional value of underutilised forages and roughages**

#### *3.1.1. Materials and methods*

Underutilised forage legumes and forage trees and shrubs (non-leguminous) were collected from various regions. These forages included *Colophospermum mopane* leaves and pods (Mangwe district; 20°36′57.5"S 27°45′39.7″E), and *Brassica oleracea var. acephala* (Bulawayo; 20°09′52.1"S 28°35′00.4″E) harvested in Southwestern Zimbabwe, and *Afzelia quanzensis* legume pods (Pietermaritzburg; 29°39′45.6"S 30°24′17.9″E) harvested in South Africa.

Eleven commonly used forages (10 forage grasses and 1 legume forage) were collected in KwaZulu-Natal, South Africa. These roughages included cowpea leaves and stems (*Mucuna pruriens*), maize stover, maize leaves, maize stalks (*Zea mays*), wheat straw (*Tritium aestivum*), kikuyu grass (*Pennisetum clandestinum*), weeping love grass at mature and bloom stages (*Eragrostis curvula*), bean straw, veld grass hay (Pietermaritzburg; 29°39′45.6"S 30°24′17.9″E), veld grass hay (Dundee; 28°09′17.2"S 30°12′42.8″E) and veld grass hay (Camperdown; 29°43′40.4"S 30°31′34.9″E). The forage hays were air-dried under a shade at ambient temperature and stored.

Moisture, dry matter (Method 934.01), organic matter and ash content (Method 942.05) of these forages and roughages were analysed using the procedures described by the Association of Official Analytical Chemists [45]. Nitrogen content was determined using the LECO TruSpec nitrogen analyser (LECO FP2000, LECO, Pretoria, South Africa). Crude protein content was calculated by multiplying the nitrogen content by a factor of 6.25 (crude protein = nitrogen content × 6.25). Neutral detergent fibre, acid detergent fibre and acid detergent lignin were analysed using ANKOM A220 fibre analyser (ANKOM Technology, New York, USA). Hemicellulose content was calculated as the difference between neutral detergent fibre and acid detergent fibre content (hemicellulose = neutral detergent fibre—acid detergent fibre). The cellulose and acid detergent lignin content were determined using the method of Van Soest and Wine [46].

The nylon bag technique [1] was used to determine the degradability of forages and roughages in the rumen. Dried forages were milled to pass through a 2-mm screen using a hammer mill (Scientec hammer mill 400, Lab World Pty Ltd., Johannesburg, South Africa). Approximately 4 g of each ground forage sample was weighed into ANKOM nylon bags (ANKOM Co, Fairport, New York, USA; internal dimensions: 5 × 9 cm; pore size 50 μm) and sequentially incubated (in triplicates per time interval) in the rumen for 120, 96, 72, 48, 24, 9, 6, and 3 hours using four non-lactating Jersey cows (body weight = 330 ± 19.97). The cows were fed on veld hay (*Themeda triandra*) and supplemented with 2 kg Lucerne hay per day (**Table 1**) at Ukulinga Research Farm, Pietermaritzburg, South Africa (29°39′45.6"S 30°24′17.9″E). Incubated bags were removed and washed together with the unincubated (zero hour) bags for 30 minutes (6 cycles each lasting 5 minutes) using a semi-automatic washing machine. Washed bags were oven-dried for 48 hours at 80°C and weighed.

### *3.1.2. Mathematical procedures*

Degradability of forages was determined using dry matter loss (DML) in nylon bags. A curve for DML against incubation time was plotted and used to inspect for outliers. The model of McDonald [47] was fitted on Statistical Analysis System 9.3 (SAS Institute Inc., Cary, NC, USA) to generate degradation parameters of the forages. The model used was as follows: Y = a + b(1–e–c(t–L)), where Y is the degradability at time (t), a is the intercept, b is the potentially degradable fraction, c is the rate of degradation of b and L is the lag time. Effective degradability (ED) was calculated using a predicted passage rates for each forage. The passage rate of solid was predicted using models developed by Moyo et al. [48].

#### **3.2. Results**

content of the fruit ranges between 600 and 910 g/kg DM [43, 44] hence may serve as a potential water source for ruminants in arid and semi-arid regions during periods of water scarcity. There is little evidence to show that ruminants eat the Monkey orange fruit and its hard pod covering makes it an unfavourable feed for non-bipedal animals. There is limited information on the nutritional value of the Monkey orange fruit as a feed source for livestock. Given the potential of the fruit to be used as supplementary water source, evaluation of the feeding value of the fruit may render its use as a potential dual purpose feed for

ruminants and other livestock.

92 Forage Groups

*3.1.1. Materials and methods*

ture and stored.

Soest and Wine [46].

**3. Nutritive value of some underutilised forage crops**

**3.1. Evaluation of the nutritional value of underutilised forages and roughages**

Underutilised forage legumes and forage trees and shrubs (non-leguminous) were collected from various regions. These forages included *Colophospermum mopane* leaves and pods (Mangwe district; 20°36′57.5"S 27°45′39.7″E), and *Brassica oleracea var. acephala* (Bulawayo; 20°09′52.1"S 28°35′00.4″E) harvested in Southwestern Zimbabwe, and *Afzelia quanzensis*

Eleven commonly used forages (10 forage grasses and 1 legume forage) were collected in KwaZulu-Natal, South Africa. These roughages included cowpea leaves and stems (*Mucuna pruriens*), maize stover, maize leaves, maize stalks (*Zea mays*), wheat straw (*Tritium aestivum*), kikuyu grass (*Pennisetum clandestinum*), weeping love grass at mature and bloom stages (*Eragrostis curvula*), bean straw, veld grass hay (Pietermaritzburg; 29°39′45.6"S 30°24′17.9″E), veld grass hay (Dundee; 28°09′17.2"S 30°12′42.8″E) and veld grass hay (Camperdown; 29°43′40.4"S 30°31′34.9″E). The forage hays were air-dried under a shade at ambient tempera-

Moisture, dry matter (Method 934.01), organic matter and ash content (Method 942.05) of these forages and roughages were analysed using the procedures described by the Association of Official Analytical Chemists [45]. Nitrogen content was determined using the LECO TruSpec nitrogen analyser (LECO FP2000, LECO, Pretoria, South Africa). Crude protein content was calculated by multiplying the nitrogen content by a factor of 6.25 (crude protein = nitrogen content × 6.25). Neutral detergent fibre, acid detergent fibre and acid detergent lignin were analysed using ANKOM A220 fibre analyser (ANKOM Technology, New York, USA). Hemicellulose content was calculated as the difference between neutral detergent fibre and acid detergent fibre content (hemicellulose = neutral detergent fibre—acid detergent fibre). The cellulose and acid detergent lignin content were determined using the method of Van

The nylon bag technique [1] was used to determine the degradability of forages and roughages in the rumen. Dried forages were milled to pass through a 2-mm screen using a hammer mill (Scientec hammer mill 400, Lab World Pty Ltd., Johannesburg, South Africa). Approximately 4 g

legume pods (Pietermaritzburg; 29°39′45.6"S 30°24′17.9″E) harvested in South Africa.

Of the underutilised forages, the crude protein content tended to be double as much for *Brassica oleracea var. acephala* compared to *Colophospermum mopane* leaves and pods (**Table 2**). Forage grasses (62.9 ± 34 g/kgDM) tended to have very low crude protein contents compared to legumes (137.6 ± 69) and concentrates (177 ± 39.9). Underutilised *Brassica oleracea var. acephala* (305 g/kgDM) tended to have higher crude protein levels compared to commonly used protein sources (CSC = 222 g/kgDM).

There was not much of a difference between the potential degradability of forage grasses (651 ± 111 g/kgDM), concentrates (756 ± 95.4 g/kgDM), and forage legumes, trees and shrubs (745 ± 110.2 g/kgDM) (**Tables 3**–**5**).


**Table 1.** Chemical composition of experimental feeds and diets fed to cows during nylon bag degradability.

DM: dry matter, OM: organic matter, N: nitrogen, NDF: neutral detergent fibre, ADF: acid detergent, ADL: acid detergent lignin, HEM: hemicellulose, CEL: cellulose, VGH: veld grass hay, LH: lucerne hay.

MPL: *Mucuna pruriens* leaves, MOC: marula oil cake, AQLP: *Afzelia quanzensis* legume pods, BOAL: *Brassica oleracea*e *var. acephala* leaves, MS: maize stover, ML: maize leaves, MT: maize stalks, MIS: millet stover, UTMIS: urea-treated millet stover, WS: wheat straw, EC: *Eragrostis* 

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**Table 3.** Nylon bag degradation of forage legumes, forage trees and shrubs (non-leguminous), and concentrates. ED was

**Table 4.** Nylon bag degradability of forage grasses (roughages) in cows fed with three different diets. ED was calculated

calculated at kp: rate of passage of particles in the rumen = 0.03 per h.

at kp: rate of passage of particles in the rumen = 0.03 per h.

CMLB: *Colophospermum mopane* leaves brown, CMLG: *Colophospermum mopane* leaves green CMP: *Colophospermum mopane* pods, DH: *Diheteropogon hagerupii*, ET: *Eragrostis tremula*,


**Table 2.** Chemical composition of incubated forages.


MPL: *Mucuna pruriens* leaves, MOC: marula oil cake, AQLP: *Afzelia quanzensis* legume pods, BOAL: *Brassica oleracea*e *var. acephala* leaves, MS: maize stover, ML: maize leaves, MT: maize stalks, MIS: millet stover, UTMIS: urea-treated millet stover, WS: wheat straw, EC: *Eragrostis* 

DM: dry matter, OM: organic matter, N: nitrogen, NDF: neutral detergent fibre, ADF: acid detergent, ADL: acid detergent lignin, HEM: hemicellulose, CEL: cellulose, VGH: veld grass

CMLB: *Colophospermum mopane* leaves brown, CMLG: *Colophospermum mopane* leaves green CMP: *Colophospermum mopane* pods, DH: *Diheteropogon hagerupii*, ET: *Eragrostis tremula*,

hay, LH: lucerne hay.

94 Forage Groups

**Table 2.** Chemical composition of incubated forages.

**Table 3.** Nylon bag degradation of forage legumes, forage trees and shrubs (non-leguminous), and concentrates. ED was calculated at kp: rate of passage of particles in the rumen = 0.03 per h.


**Table 4.** Nylon bag degradability of forage grasses (roughages) in cows fed with three different diets. ED was calculated at kp: rate of passage of particles in the rumen = 0.03 per h.


**4. Is it possible to predict the rumen digestibility (feeding value) of** 

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**4.1. Prediction of degradation of forages in the rumen using feed and animal properties**

Data were collected from studies that reported at least average values for in sacco (nylon bag technique) degradability parameters (a, soluble fraction; b, slowly degradable fraction and c, rate of degradation) of roughages and stated the diet, feeds and feed supplements given to animals. A dataset was created bearing degradability parameters from wild and domesticated ruminants from 40 studies. Factors affecting degradability were identified in each of these studies and were categorised into two main groups: (1) diet properties (i.e. fed to the animal) and (2) feed sample properties (i.e. incubated in the rumen). Diet properties were used to account for the effects of rumen ecology on fermentation and included neutral detergent fibre (NDF), starch (STA) and crude protein (CP) contents of entire diet (all in g/kg), level of concentrate supplementation (%) and provision of a urea supplement in the form of a lick (presence = 1, absence = 0). Feed sample properties included urea treatment (%) of sample and feed compositional attributes (DM, dry matter; CP, crude protein; NDF, neutral detergent fibre, ADF, acid detergent fibre; HEM, hemicellulose and ash all in g/kg). Starch content of the diet fed to animals was calculated using the formula: STA = 1000–(NDF + CP). Potential degradability (PD) and hemicellulose (HEM) content were calculated in studies that did not report them using the formulae: PD = a + b; and HEM = NDF—ADF, respectively. Studies that did not report dietary composition of feeds but mentioned names of feeds used had their composition looked up in studies that reported them. These factors were used as input parameters to develop regression models for predicting degradability of feeds in the rumen.

A step-wise regression procedure on the Statistical Analysis System 9.3 (SAS Institute Inc., Cary, NC, USA) was used to select parameters that qualified to develop regression equations to predict (1) rapidly degradable fraction of fibre (a), (2) potential degradability (PD), (3) time lag for fermentation to occur (tL), and (4) rate of degradation (c) in the rumen. One parameter from a pair of correlated parameters was dropped in model development when both correlated parameters significantly influence degradation parameters. Those parameters that qualified for model development were CP and NDF content of feed sample (model for soluble fraction of fibre); ADF content of feed sample and STA content of diet (model for potential degradability); ADF, CP and ash content of feed sample, and STA content of diet (model for time-lag); NDF and CP content of feed sample, and, STA and DNDF content of diet (model

Regression models were used to simulate the rumen degradability of *Colophospermum mopane* leaves and pods, *Diheteropogon hagerupii*, *Eragrostis tremula*, *Mucuna pruriens* leaves, Marula oil cake, *Afzelia quanzensis* legume pods, *Brassica oleraceae var. acephala* leaves, maize stover, leaves and stalks, millet stover, wheat straw, *Eragrostis curvula*, Kikuyu grass, *Schizachyrium exile*, veld grass hay, cowpea husks, cassava root peels, groundnut haulms, *Eragrostis tremula*,

**unknown and underutilised forages?**

*4.1.1. Materials and methods*

for degradation rate).

**Table 5.** Nylon bag degradability of urea treated and untreated forage grasses (roughages) in cows fed kikuyu pasture.

*curvula*, ECB: *Eragrostis curvula* at bloom stage, KG: kikuyu grass, SE: *Schizachyrium exile*, VGHD: veld grass hay from Dundee, VGHC: veld grass hay Camperdown, VGHP<sup>1</sup> : veld grass hay Pietermaritzburg area 1, VGHP<sup>2</sup> : veld grass hay from the Pietermaritzburg area 2, CPH: cowpea husks, CRP: cassava root peels, GNH: groundnut haulms, UTCPH: ureatreated cowpea husks, UTDH: urea-treated *Diheteropogon hagerupii*, UTET: urea-treated *Eragrostis tremula*, UTSE: urea-treated *Schizachyrium exile*, UTMIS: urea-treated maize stover, SS: sorghum stover, UTSS: urea-treated sorghum stover, SSLS: sorghum stover leaves and sheath, SSS: sorghum stover stems, MB: millet bran, WB: wheat bran, and CSC: cottonseed cake.

CMLB: *Colophospermum mopane* leaves—brown, CMLG: *Colophospermum mopane* leaves green, CMPG: *Colophospermum mopane* pods, CPH: cowpea husks, CRP: cassava root peels, GNH: groundnut haulms, MPL: *Mucuna pruriens* leaves, AQLP: *Afzelia quanzensis* legume pods, BOAL: *Brassica oleraceae var. acephala* leaves, UTCPH: urea-treated cowpea husks, MB: millet bran, WB: wheat bran, CSC: cottonseed cake, a: rapidly degradable fraction, b: slowly degradable fraction, c: rate of degradation, PD: potential degradability, and ED: effective degradability.

MS: maize stover, ML: maize leaves, MT: maize stalks, WS: wheat straw, EC: *Eragrostis curvula*, ECB: *Eragrostis curvula* at bloom stage, KG: kikuyu grass, VGHD: veld grass hay from Dundee, VGHC: veld grass hay Camperdown, VGHP1: veld grass hay Pietermaritzburg area 1, VGHP2: veld grass hay from the Pietermaritzburg area 2, kp: rate of passage of particles in the rumen, a: rapidly degradable fraction, b: slowly degradable fraction, c: rate of degradation, PD: potential degradability, and ED: effective degradability.

MS: maize stover, ML: maize leaves, MT: maize stalks, WS: wheat straw, EC: *Eragrostis curvula*, ECB: *Eragrostis curvula* at bloom stage, KG: kikuyu grass, VGHD: veld grass hay.
