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Citation of this paper

Crude protein intake and growth performance of West African Dwarf (WAD) goats fed cassava peel substituted with cowpea haulms

Omotoso O B, Rafiu M O and Oso T S

Department of Animal Production and Health, School of Agriculture and Agricultural Technology, Federal University of Technology, P M B 704, Akure. Ondo State, Nigeria


In rural communities, postharvest crop mainly residues are often left in open fields, consequently contributing to environmental pollution. Meanwhile, these residues have nutritional potential that could be harnessed for improved and sustained livestock (ruminant) production. Hence, a 56-day study was conducted to evaluate the potentials of cowpea haulms (CH) when combined with cassava peel meal (CPM) at 100CPM, 75CPM25CH, 50CPM50CH and 25CPM75CH for goats. The feed materials were blended and mixed together and were fed to twenty (20) growing West African Dwarf (WAD) goats aged 10 - 12 months, live bodyweight of 8.86 kg, randomly assigned (5 goats per group) to the dietary treatments. From the results, the increased dry matter intake and daily weight gain resulted in linear or curvilinear increases in relation to the improvement in feed conversion ratio as cowpea haulms replaced cassava peel in the diet. Suggesting that cowpea haulms are rich in nutrient and improved the feed protein quality. Consequently, cassava peel substituted with cowpea haulms at 75% improved the goats' dry matter intake, live weight gain and feed conversion ratio. It is therefore recommended that substituting cassava peel with cowpea haulms at 25:75 is optimum for growth, reduces environmental pollution, converts waste to wealth and could be adopted by ruminant farmers.

Keywords: crop residue, daily weight gain, feed intake, small ruminant


Ruminant production remains a significant sector contributing greatly to the animal protein sources in the diets of humans. However, the productivity of West African Dwarf (WAD) goats, which are a vital source of meat and milk for smallholder farmers in West Africa, is constrained by limited quality and quantity of feed (Ofori and Hagan, 2021), particularly during the dry season when pasture supply is scanty, resulting in poor nutrition and reduced optimal performance (Omotoso et al 2023). Crop residues after crop harvest are cheap, readily available throughout the year and therefore can be considered as alternative feed material in ruminants’ nutrition to ease off feed scarcity and inadequate nutrition commonly observed during the dry season and can be used as a substitute for expensive concentrate/convectional feedstuff (Okoli, 2020a). Cassava peel has been widely used as a feed ingredient with higher energy but low protein concentration (Okoli, 2020b). Cowpea haulms are postharvest residues regarded as nuisance/waste by crop farmers after dehulling and are burnt off on the farmland contributing significantly to global warming and environmental pollution. Meanwhile, these cowpea haulms are protein-rich feed material, being a leguminous plant and could easily be complement energy-rich feed material, even without subjecting to further process like ensiling, for improved small ruminant production by peasant farmers. Due to the nature of their stomach, ruminants show improved performance when energy and protein-rich diets are strategically integrated for feeding (Omotoso et al 2023). By harnessing these resources, the productivity of WAD goats can be improved, contributing to the rise in animal protein supply and enhancing food security, especially in the sub-Saharan Africa. Therefore, this study was conducted to evaluate the dietary effect of substituting cassava peel with cowpea haulms on nutrient intake and growth performance of West African Dwarf (WAD) goats.

Materials and methods

Experimental site

The study was conducted in the Department of Animal Production and Health, Federal University of Technology. Akure (FUTA), Ondo State, Nigeria.

Sourcing and processing of feed materials

The sun-dried cassava peels were collected from a cassava processing industry in Igbatoro, Akure, while the cowpea haulms were collected from the Teaching and Research Farm of the Department of Crop, Soil, and Pest Management, FUTA. The haulms were collected immediately after dehulling, sun-dried, milled from the University Feedmill and kept in a clean air-tight container for later use. The experimental diets constitute cassava peel substituted with cowpea haulms as shown in Table 1.

Table 1. Gross composition (%) of the experimental diets

Ingredients (%)





Cassava peel





Cowpea haulms





Animal procurement, management and experimental design

A total of twenty (20) WAD goats, with age range of 10 – 12 months and average initial weight of 8.86 kg was used for the study. The goats were purchased from reputable farms in Ondo State, Nigeria. Upon the commencement of the experiment, the goats were housed individually in a pen measuring 2 x 1-meter square, with free access to water and feed. The goats were randomly apportioned into four (4) treatment groups, balanced for weight comprising five (5) goats per treatment in a completely randomized design.

Data collection, feed analysis and statistical analysis

Goat feed intake was estimated by removing daily leftovers from the feed offered. Goat weights were measured before the experiment and weekly basis in the morning prior to feeding. Feed samples were analyzed for chemical composition using AOAC (2016) and Van Soest et al (1991) methods. Data were subjected to one-way analysis (ANOVA) using SPSS (2020) version 26.0.


As cowpea haulms were replaced with cassava peel, there was an observed increase in the percentage of crude protein and crude fiber (Table 2).

Table 2. Chemical composition (%) of the experimental diets


Cowpea haulms, %







Dry Matter







Crude Protein

5.31 d

12.2 c

17.8 b

24.6 a



Crude Fibre

8.65 c

11.8 b

13.2 b

17.4 a



Ether Extract

2.26 a

2.14 a

1.84 b

1.82 b



Acid Detergent Fibre

44.7 c

49.1 a

46.3 b

43.1 d



Neutral Detergent Fibre

45.9 c

52.6 a

51.8 a




Acid Detergent Lignin

35.5 a

33.0 b

29.6 c

23.8 d



abcd Means in the same row without common letter are different at p<0.05

Figure 1. Daily weight gain by WAD goats fed cassava
peel substituted with cowpea haulms
Figure 2. DM feed conversion by WAD goats fed cassava
peel substituted with cowpea haulms

Figures 1 and 2 depict the augmentation of both daily weight gain and DM feed conversion, exhibiting either linear or curvilinear patterns, as the substitution of cassava peel with cowpea haulms took place. This observation is further supported by the enhancement in DM intake, as illustrated in Figure 3, which aligns with the data provided in Table 2.

Figure 3. DM feed conversion by WAD goats fed cassava
peel substituted with cowpea haulms

Table 3. Growth performance of WAD goats fed experimental diets DMI by WAD goats fed cassava peel substituted with cowpea haulms


Cowpea haulms, %






p -value

Initial weight (kg)







Final weight (kg)







Weight gain (kg)

2.43 d

3.17 c

3.83 b

4.34 a



Dry matter intake (g/day)

389 b

466 a

387 b

449 a



Daily weight gain (g/day)

43.4 d

56.6 c

68.4 b

77.5 a



Feed conversion ratio

8.97 a

8.23 b

5.65 c

5.79 b



abcd Means in the same row without common letter are different at p<0.05


The high crude protein intake in this study could be traced to the cowpea haulms which influenced palatable and acceptable (voluntary feed intake) by the animals. Omotoso et al (2022) reported that voluntary feed/nutrient intake in goat is a function of complex determinants ranging from age, breed, physiological status, feed palatability, feeding conditions, and management among others. Goats fed 25CPM75CH had the highest nutrient intake and consequently, daily weight gain (Figure 1). Omotoso and Fajemisin (2020) reported that increased dry matter intake can be attributed to the quality of protein, acceptability of the diets, and their palatability. Increased dry matter intake contributes to the enhancement of rumen microbial activity, as sources of energy and nitrogen which provide the necessary support for growth, development and performance. Also, Oloche et al (2021) reported that feeding cowpea husks to goats resulted in improved feed intake and digestibility. The experimental animals showed high feed consumption, and the level of cowpea haulms inclusion had favorable effects on feed intake, with the calculated nutrient intake increasing as the cowpea haulms inclusion level increased. The high nutrient intake of West African Dwarf (WAD) goats was due to the quality of the feed, specifically the nutrient availability. The crude fibre intake recorded by goats fed 25CPM75CH was an indication that the feed provides bulk structural components to animals; hence promotes proper rumen function by stimulating rumination and maintaining a healthy rumen environment which consequently enhances growth performance. Bayne and Edmondson (2021) reported that adequate fiber intake helps to prevent digestive disorders and improves the overall digestive health of ruminants.

Goats fed 25CPM75CH had the highest gain weight and the least feed conversion ratio which could be traced to the potential of cowpea haulms to enhance growth. Weight gain is dependent on dry matter intake, protein intake, and the digestibility of the nutrients by the animals (Jiwuba et al 2021). The growth performance of small ruminants’ hinges on the availability of high-quality and quantity feeds. Prakash et al (2020) reported that the higher feed conversion ratio indicates a less desirable diet, as the animal needs to consume more feed to achieve a unit weight gain.



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