Physico-Chemical Characteristics and Acceptability of Graded Levels of Ensiled Cabbage Waste and Wheat Offals as Ruminants’ Supplemental Diet

Animal nutritionists are now searching for new non-traditional feed sources to enhance ruminants’ diets due to price increases and the unavailability of some unconventional feed ingredients. In a Completely Randomized Design, wheat offal was substituted with cabbage waste silage in diets 1 to 5 at 0, 10, 20, 30, and 40%, respectively for 30 days to assess the physicochemical characteristics and acceptability of the new diets by Yankasa rams. Temperatures of 29.00 ± 0.14 and 28.05 ± 0.78 °C, respectively, were noticeably lower in diets 4 and 5. Diets 4 (4.26) and 5 (4.38) considerably lowered (P > 0.05) the pH. All of the diets had good silages based on color, smell, and texture, with diet 5 having a firm and wet texture. Diets 4 and 5 had sweet aromatic odour. With increasing the amount of cabbage waste in the silage, the dry matter dropped, going from 80.11 to 46.88% in diets 1 and 5, respectively. Diet 4’s lowest CP of 12.68%, is sufficient for ruminant feeding. In diet 4, the values of crude fiber and ether extract significantly (P < 0.05) increased. Although there were substantial differences (P < 0.05) in each diet’s fiber content, the NDF, ADF, and ADL all fell within the acceptable range for excellent silage. All the silages made in diets 1 to 5 were acceptable by Yankasa rams, but diet 5 ranked highest in terms of coefficient of preference (CoP). According to all findings, cabbage waste could be a valuable silage additive in ruminants’ diets. Wheat offal can be replaced by cabbage waste up to 30% and 40% in the diet of ruminants with good silage formation and better CoP.

Introduction

One of the main issues influencing the productivity of ruminant animals in Nigeria is the low nutritional value of pasture during the rainy season as a result of increased cell wall components (Loweet al., 2011). Another issue is the scarcity of fodder during the dry season. To counter-check this, it becomes necessary to replenish the nutritional imbalance in tropical pastures in order to boost productivity and prevent animal morbidity and mortality (Lamidi & Ologbose, 2014). By enhancing digestion, speeding up the transit of indigestible residues, and raising the intake of total digestible nutrients (TDN), supplementation has been shown to promote pasture utilization (Rothet al., 2019).

Animal nutritionists have discovered that when ensiled or sun-dried, vegetable wastes, with losses of approximately 55% at various points along the food chain in Africa (Gustavssonet al., 2011), can be used as a supplemental diet for ruminant production. Additionally, it can be used to produce biogas at the expense of its environmental threat (Makkar & Ankers, 2014; Kafleet al., 2014). However, the precise assessment of its nutritional value (NV), which will determine how much nutrition can be absorbed by ruminant animals from the feedstuff, is necessary for its supplementation in ruminant diets (Tedeschiet al., 2019).

One of the many unconventional feed ingredients or agro-industrial byproducts that are traditionally used to supplement the diet of ruminants is wheat offal/bran. A by-product of dry milling, common wheat (Triticum aestivum L.) proceesed into flour is wheat offal or bran. It can be used to partially or completely to substitute maize, a traditional feed ingredient (Alikweet al., 2012; Makinde & Inuwa, 2015; Abbatoret al., 2017). In Nigeria, however, the regular increases in wheat prices and the increased cost of transportation from manufacturers to the place of use for livestock are anticipated to raise production costs.

A potential non-traditional feed source for ruminants is cabbage wastes (Brassica oleracea), a vegetable by-product that is readily available in Nigerian cities with large fresh produce markets. It has high moisture content and includes between 137 and 280 grams of crude protein, 9 to 17 grams of ether extract, and 186 grams of crude fiber per kilogram of dry matter (Guptaet al., 1993; Mekashaet al., 2002). If not ensiled, its high moisture content (86–140 g dry matter (DM)/kg) will need to be fed within three days; however, if combined with other high DM feedstuff for successful feeding, it could be utilized much longer (Nkosi & Meeske, 2010).

Makkar and Ankers (2014) suggest that ensiling could be a replacement for wasted agricultural byproducts for use as animal feed. The production of silage is favoured because it is less reliant on the weather, ensures that nutrients are preserved, and can be stored for a long time. Research on the chemical components of cabbage wastes ensiled with other high DM diets produced a variety of outcomes. The growth stage, season, species and variation, types of soil, and growth environment could all have a role in the discrepancies (Mekashaet al., 2002; Wadhwaet al., 2006; Nkosiet al., 2016; de Evanet al., 2019). The purpose of this study is to evaluate the substitutability of cabbage waste for wheat offal in ruminant silage additives in terms of physical attributes, chemical constituents and preference by Yankasa sheep.

Materials and Methods

Location of the Experiment

The experiment was carried out at the small ruminants unit of the Teaching and Research Farm, University of Ibadan, Ibadan, Oyo State, Nigeria. The climate is tropical with about 1311 mm of annual precipitation which starts in March and reaches its peak in June with an average of 190 mm. March is the warmest month with an average temperature of 28.6 °C. The average annual temperature is 26.5 °C while the variation in annual temperature is around 4.5 °C.

Experimental Diets

Five diets were formulated in accordance with the typical nutritional needs of ruminants (Adegun & Aye, 2013), to constitute the treatments in a completely randomized design.

Diet 1: 0% Cabbage waste (CW), 60% wheat offal (WO), 20% Dry cassava peels (DCP) and 20% Brewers’ Dried Grain (BDG).

Diet 2: 10% CW, 50% WO, 20% DCP, 20% BDG.

Diet 3: 20% CW, 40% WO, 20% DCP, 20% BDG.

Diet 4: 30% CW, 30% WO, 20% DCP, 20% BDG.

Diet 5: 40% CW, 20% WO, 20% DCP, 20% BDG.

Procurement of Test Ingredients

The cabbage waste was collected from Eleyele vegetable market in Ibadan, south west, Nigeria and was transported to the Teaching and Research farm. The cabbage waste was chopped using cutlass into smaller size of about 4 mm for easy compaction as recommended by T’Mannetje (1999). The chopped materials were wilted under shade for 24 hours on concrete floor. The wheat offals and Brewers’ Dried Grain were bought from feed millers shop in Ibadan city while the cassava peel was obtained from the garri processing plants in University of Ibadan.

Silage Preparation

The chopped cabbage waste, wheat offal, dry cassava peel and brewers’ dried grain were weighed according to the treatments and mixed together. They were filled into 4-litre mini silos made of plastic materials in different proportions and in triplicates to form the five dietary treatments as described by Babayemi (2009). The ensiled materials were well compressed to eliminate trapped air and rapidly sealed with the polythene sheet in order to prevent air re-entry. The plastic materials were then compressed with weights and ensiled for 30 days as recommended by T’Mannetje (1999) and Babayemi (2009).

Evaluation of Physical Characteristics of the Silages

Colour, odour and texture of the silages

Silage colour was assessed by visual observation and using a colour chart. The odour/smell and texture were assessed by a 5-man panel. These steps were taken against a bias attitude of a one-man assessor since the physical attributes are reported on a nominal and not on ordinal scale (Guoet al., 2002).

Determination of pH of the silages

The pH of the silages was determined using a pocket pH meter (Hanna portable meter) by taking about 25 g of sample from each treatment, mixed with 100 ml of distilled water in a beaker for 1 hour and agitated for 2 minutes. Following this, a pH meter glass electrode was then inserted into the supernatant for 1–2 seconds and pH determined following the standard procedure (AOAC, 2000; Babayemi, 2009).

Determination of temperature of silages

The temperature of silages was taken by dipping a thermometer inside silage mass and kept in place for 5 minutes before taking the reading. Thereafter, 100 g samples were taken from different depths of the silos and mixed to ensure homogeneity of samples. Another 200 g was sampled, mixed up thoroughly and kept in the freezer at -4 °C for subsequent laboratory analysis.

Chemical analysis of the silages

Dry matter content of the ensiled material was determined by oven-drying at 65 °C until constant weight was achieved. The samples were milled and kept until ready for analysis. The samples of the silages were milled in the laboratory with hammer mill of 1mm sieve and subjected to chemical analysis for determination of crude protein, ash, ether extract and nitrogen free extract as described by AOAC (2000). Neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) were assessed by the methods proposed by Van soestet al. (1991).

Acceptability studies

Fifteen (15) Yankasa rams aged between 12–15 months were used in a completely randomized design and allowed to feed four (4) hours daily for 10 consecutive days. Consumption was measured by deduction of remnants from the amount of feed served daily. The diet preferred was assessed from the coefficient of preference (CoP) value and percentage of preference was adapted from forage acceptability study of Babayemi (2009). The diet preferred was relatively acceptable/preferred provided the CoP value was greater than unity. Coefficient of Preference=Intake of individual SilageMean intake of the silage types

If CoP is <1, the feed is poorly accepted, if >1, the feed is well accepted (Bamikoleet al., 2004).

Statistical Analysis

Data collected were subjected to analysis of variance using the procedure of SAS (2000). Significant means were separated using Duncan Multiple Range F-Test (DMRT) (Duncan, 1955). Results were considered significant at P < 0.05.

Results

Table I presents the physical features of ensiled wheat offal and graded levels of cabbage wastes. Regarding temperature and pH, there are statistical differences across the diets. Diets 4 (28.05 ± 0.78 °C) and 5 (29.00 ± 0.14 °C) had comparable temperatures, however, diets 1 (31.90 ± 0.42 °C), 2 (30.95 ± 1.06 °C) and 3 (31.55 ± 0.64 °C) had considerably higher temperatures (P < 0.05) than diets 4 and 5. The temperature values of diets 1, 2, and 3 did not differ significantly (P > 0.05). Diet 1 produced pH that was substantially higher (6.31 ± 0.06) than other diets with diet 4 and 5 recording the lowest pH of 4.26 ± 0.04 and 4.38 ± 0.12 respectively at P < 0.05. Diets 1 and 2 had light brown coloring, diet 3 had light greenish brown coloring, diet 4 had slightly darker brown coloring, and diet 5 had a brownish green coloring. There are differences in color across the diets, with only diets 1 and 2 having a similar color. Additionally, the odor varied among the diets, but it was similar for diets 1 and 2 and diets 4 and 5. The two groups were different, and they were likewise different from diet 2. Only diets 3 and 4 had similar degrees of firmness across all diets, which varied in all other diets.

Table I. Physical Characteristics of Graded Levels of Cabbage Waste Ensiled with Wheat Offal

Diets	Temperature (°C)	pH	Colour	Odour	Texture
Diet 1	31.90 ± 0.42b	6.31 ± 0.06a	Light Brown	Pleasant Fruity	Very Firm and Dry
Diet 2	30.95 ± 1.06b	5.29 ± 0.33b	Light Brown	Pleasant Fruity	Firm and Dry
Diet 3	31.55 ± 0.64b	5.18 ± 0.06b	Light Greenish Brown	Aromatic Fruity	Firm
Diet 4	29.00 ± 0.14a	4.26 ± 0.04c	Slightly Dark Brown	Sweet Aromatic	Firm
Diet 5	28.05 ± 0.78a	4.38 ± 0.12c	Brownish Green	Sweet Aromatic	Firm and Slightly wet

The chemical constituent (%) of cabbage waste, wheat offal and varying grades of ensiled cabbage waste with wheat offal is shown in Table II. The proximate constituents of cabbage waste were 19.65%, 14.40%, 32.02%, 6.75% and 9.20% in terms of dry matter (DM), crude protein (CP), crude fibre (CF), ether extract (EE) and ash respectively, while those of wheat offal were 91.00%, 16.24%, 8.56%, 3.45% and 5.32%, respectively. There were significant differences (P < 0.05) among all of the examined parameters in the ensiled diets. Diet 1 had the highest DM (80.11 ± 0.42%) content which reduced significantly with the addition of cabbage wastes in the diets with 5 having the least DM (43.88 ± 9.40%). Crude protein was higher and statistically similar (P > 0.05) in diets 1 and 5 (15.95 ± 0.21 and 16.25 ± 0.21%) respectively while diet 4 recorded the least (P < 0.05) CP value of 12.68 ± 0.60%. Crude fibre ranged from 17.20 ± 0.42% in diet 2 to 18.95 ± 0.21% in diet 4. Ether extract (EE) values were comparable (P > 0.05) in diets 1, 3, 4, and 5 with the least significant (P < 0.05) value in diet 2. When compared to the other diets, diet 3 had the highest and most significant (P < 0.05) value in terms of ash, while diets 1 and 4 had the lowest values.

Table II. Chemical Analysis of Cabbage Waste, Wheat Offal and Graded Levels of Cabbage Waste Ensiled with Wheat Offal (%)

Diets	Dry matter	Crude protein	Crude fibre	Ether extract	Ash
CW	19.65 ± 0.52	14.40 ± 0.62	32.02 ± 1.28	6.75 ± 0.24	9.20 ± 0.78
WO	91.00 ± 3.02	16.24 ± 0.54	8.56 ± 0.64	3.45 ± 0.16	5.32 ± 0.44
Diet 1	80.11 ± 0.42a	14.50 ± 0.28b	18.50 ± 0.42ab	2.25 ± 0.07ab	7.85 ± 0.35c
Diet 2	75.34 ± 9.28ab	15.95 ± 0.21a	17.20 ± 0.42c	2.20 ± 0.14b	10.30 ± 0.28bc
Diet 3	70.55 ± 0.45ab	13.93 ± 0.39b	18.40 ± 0.14ab	2.55 ± 0.21ab	15.95 ± 0.25a
Diet 4	59.79 ± 2.81b	12.68 ± 0.60c	18.95 ± 0.21a	2.70 ± 0.28a	6.80 ± 0.57c
Diet 5	43.88 ± 9.40c	16.25 ± 0.21a	18.05 ± 0.21b	2.55 ± 0.07ab	13.10 ± 5.09b

The graded levels of cabbage waste ensiled with wheat offal and their respective fiber fractions are shown in Table III. For acid detergent lignin, neutral detergent fiber, and acid detergent fiber, there were significant differences (P < 0.05) across the diets. Between diets 1 and 5, there was no discernible change for NDF. However, these values were considerably greater than the NDF values obtained for diets 2, 3, and 4. Diet 1 (36.65 ± 0.49%) considerably enhanced the acid detergent fiber, and diet 5 (33.40 ± 0.99%) followed. Diets 3 and 4 had the least significant variations but similar values (P > 0.05). Diet 1 significantly increased in terms of ADL, followed by diet 5. There was no discernible difference (P > 0.05) between diets 2 and 4 in terms of ADL values, while diet 3 had the lowest value of 12.35 ± 0.35%.

Table III. Fibre Fractions of Graded Levels of Cabbage Waste Ensiled with Wheat Offal (%)

Diets	NDF	ADF	ADL
Diet 1	49.95 ± 0.21a	36.65 ± 0.49a	15.50 ± 0.57a
Diet 2	47.05 ± 0.35b	31.00 ± 0.14c	14.20 ± 0.57b
Diet 3	43.90 ± 0.28d	27.95 ± 0.64d	12.35 ± 0.35c
Diet 4	45.10 ± 0.57c	29.25 ± 0.21d	13.80 ± 0.42b
Diet 5	49.35 ± 0.57a	33.40 ± 0.99b	14.95 ± 0.21ab

Acceptability and preference of graded levels of cabbage waste ensiled with wheat offal by Yankasa rams are presented in Table IV. All the silages made in diets 1 to 5 were acceptable by Yankasa rams. However, there were significant differences (p < 0.05) in the coefficient of acceptability (CoP) in the diets. There were significant similarities (p > 0.05) in the CoP of diet 3 (1.06),4 (1.06) and 5 (1.09) which were significantly higher (p < 0.05) than the CoP of diet 1 (1.02) and diet 2 (1.01). The preference ranking was highest for diet 5 (40% cabbage waste) while diets 1 (0% CW) and 2 (10% CW) recorded the least preference ranking.

Table IV. Acceptability and Preference of Graded Levels of Cabbage Waste Ensiled with Wheat Offal by Yankasa Rams

Diets	CoP	Preference Ranking	SEM
Diet 1	1.02ab	3rd	0.02
Diet 2	1.01ab	4th	0.02
Diet 3	1.06a	2nd	0.03
Diet 4	1.06a	2nd	0.02
Diet 5	1.09a	1st	0.02

Discussion

The study’s temperature range of 28.05 °C to 31.90 °C is in line with the temperature of good silage (Weinberget al., 2001). Silages produced at temperatures outside of this range tend to be of worse quality, even though it may still taste fine. In diets 4 and 5, more cabbage waste in the diets resulted in decreased pH. This is in line with Adautonet al. (2015) who reported that with the inclusion of ground corn, the pH values of the cabbage silage increased linearly. A pH of up to 4.5 is regarded as good, whereas pH values above 5.5 may not be regarded as desirable (Trisnadewi & Cakra, 2020). According to Babayemi (2009), high pH which may be due to clostridia is a definite indicator of an undesirable fermentation due to high dry matter that has led to poor quality silage as observed in diet 1 to 3 with pH greater than 5. High pH hinders silage fermentation by inhibiting the growth or killing microbes that are pH intolerant (Kunget al., 2018). All of the silage diets smelled fruity and pleasant, which suggested that quality silages had been produced (Kunget al., 2018). Tingshuanget al. (2002) claim that the presence of plant structures in silage is a sign of high-quality silage. Firmness, a characteristic of good quality silage, can be found in all of the silages in this study.

Out of all the diets, diet 4 has the least amount of crude protein (12.78%), which is still good for ruminants. It has been determined that small ruminants require up to 11% to 13% amount of CP for maintenance and modest growth (Asaoluet al., 2012). Because the values were identical in diets 1 and 5, the crude protein value did not follow any particular pattern in the diets. This contradicts the finding of Adautonet al. (2015), who found that the amount of CP reduced as ground maize in cabbage silage rose. This might be because wheat offal has a higher CP than ground corn. Additionally, compared to cabbage and wheat offal, ground corn had lower quantities of fiber and protein, which helps to explain the decreases in the CP, NDF, ADF, and lignin contents of the cabbage silages.

The chemical constituents of cabbage waste recorded in this study are similar to other results (Adautonet al., 2015; de Evanet al., 2019). For wheat offal, the CP observed in this study (16.24%) exceeds 11.30% obtained by (Alikweet al., 2012). Also, the same authors revealed a higher EE value (11.00%) than the 3.45% obtained in this study. As the amount of cabbage waste in the diets grew, the dry matter (DM) dropped. With the addition of wheat offal, the anticipated rise in the DM content of the cabbage silage was confirmed (Adautonet al., 2015). In a similar vein, dry matter rose as breadfruit addition to water hyacinth silage was increased (Abegundeet al., 2017). In contrast to unensiled cabbage waste, silages with more cabbage waste had DM of 59.79 and 43.66%, which increased DM. This would boost nutrients available to the animals (Nkosiet al., 2016). For every kilogram of new silage provided to the animal, a higher DM will result in greater calorie and protein intake (Khorvashet al., 2006; Bakshiet al., 2016). The increased DM in ensiled cabbage waste compared to 6.60%–16.30% DM in fresh cabbage waste was caused by the use of absorbent materials like wheat offal, dry cassava peel, and brewer’s dried waste (de Evanet al., 2019). Additionally, the addition of ground maize to the cabbage waste silage resulted in a higher value of DM (Adautonet al., 2015). Neutral detergent fiber (NDF) and lignin levels in all of the diets are low, indicating a strong potential for voluntary ingestion. The amount of feed an animal can consume reduces as forage NDF rises. NDF of up to 48%, however, as found in all diets in this study, indicates high-quality silage (Beef-Lamb New Zealand feed quality fact sheet, 2019). The fiber components did not exhibit any discernible patterns, but another study found that adding ground corn to silage decreased its NDF, ADF, and lignin amounts (Adautonet al., 2015). The chemical variations between ground corn and wheat offal could be the cause of the discrepancies.

The diets showed moderate acceptability. Organoleptic characteristics are useful in assessing silage quality because the volatile nature of many ensilement processes produces a variety of unique colours, odours and tastes (Kunget al., 2018). The reason for the acceptability of the silages to the animals may be due to its odour, as the amount of cabbage increased the odour becomes more aromatic and more acceptable. Preference is influenced by physical structure and chemical composition (Babayemi, 2009).

Conclusion

Due to its favorable physical and chemical characteristics, ensiled cabbage waste has a lot of potential as a supplement in ruminant diets. The farmer may easily obtain cabbage waste at minimal cost due to transportation, which makes it a great element to substitute for wheat offal while creating silage. Up to 30% and 40% of cabbage waste can substitute the wheat offal in ruminants’ diets as a result of adequate nutrient, physical parameters and acceptability by Yankasa rams.

Authors’ Contribution

This is to confirm that Maria Kikelomo Adegun conceived and designed, analyzed and interpreted the data, drafted the manuscript and revised it critically for important intellectual content.

Tolulope Ososanya was involved in the design, analysis and interpretation of the manuscript and revised it critically for important intellectual content.