Effects of liquid microbial inoculants on quality attributes of forage cowpea
It is imperative to improve the quality of fodder crops. Therefore, in the present study, effect of different treatments of liquid microbial inoculation on the nutritional quality of forage cowpea has been studied.
Acid detergent fibre (ADF)
Acid detergent fibre are frequently used as standard for evaluating the quality of forage. ADF primarily represents cellulose and lignin. Because of the negative relationship between the digestibility and ADF, low ADF is desirable.
The perusal of the data revealed significant reduction in ADF% in treatments with liquid microbial inoculants when compared with the control (P£0.005). Highest and the lowest ADF% was noted in control (T
1: RDF) and treatment T
10 i.e 75% of RDF +
Burkholderia sp.+
Burkholderia seminalis with values of 37.94% and 34.25% at Ludhiana respectively. The percentage decrease in ADF% over T
1 (control) in T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
3, T
2 and T
4 was 9.25%, 8.90%, 8.59%, 8.40%, 6.41%, 3.60%, 0.74%, 0.61%, 2.28% and 0.56% respectively at Ludhiana.
Likewise, data pertaining to ADF (%) at Bathinda revealed decrease in ADF% with the application of liquid microbial inoculants (Table 2). The percentage decrease in ADF content over T
1 (control) in T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
3, T
2 and T
4 was 12.67%, 12.21%, 11.78%, 10.63%, 10.27%, 6.39%, 2.14%, 2.97%, 1.67% and 1.29% respectively at Bathinda location.
In all the treatments with liquid microbial inoculants decline in ADF % was recorded and lowest ADF% was recorded with treatment 75% of RDF +
Burkholderia sp. +
Burkholderia seminalis. This might be due to escalated availability of nitrogen owing to biological nitrogen fixation by
Burkholderia sp,
Burkholderia seminalis and
Bradyrhizobium sp. Improved uptake of nitrogen imparts succulence to green plants by reducing the fibre content.
These results are in close conformity with the earlier findings of Asefa (2018) who reported that the application of
Rhizobium inoculants and phosphorus fertilizer had significant negative effects on haulm NDF, ADF and ADL content of faba bean over control.
Neutral detergent fibre (NDF)
NDF consists of slowly digestible and non-digestible fibrous portion of plant which commonly consists of cell wall material including hemicellulose. However, if NDF of the ration is too low it results in health problems like displaced abomasum, acidosis and foundering may occur (Ball
et al., 2001).
Data presented in Table 1 showed non-significant effect of liquid microbial inoculants on NDF% (P£0.005). However, numerically highest and lowest NDF% was recorded in control (T
1: RDF) and treatment T
10 i.e 75% of RDF +
Burkholderia sp. +
Burkholderia seminalis (54.41% and 48.18% respectively) at Ludhiana. The percentage decrease in NDF% over T
1 (control) in T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
3, T
2 and T
4 was 11.45%, 11.13%, 11.13%, 9.13%, 7.51%, 7.48%, 5.64%, 5.58%, 5.53% and 2.07% at Ludhiana respectively.
The data pertaining to NDF% at Bathinda showed significant effect with liquid microbial inoculants (Table 2). Maximum and minimum NDF% of 54.79% and 47.00% was observed in control (T
1: RDF) and T
10 treatment (75% of RDF +
Burkholderia sp. +
Burkholderia seminalis) respectively. However, treatments T
2 and T
4 were at par with treatment T
1 whereas treatments T
3, T
5, T
6, T
7, T
8, T
9, T
10 and T
11 showed significant reduction in NDF% over T
1. The percentage decrease in NDF% over T
1 (control) in T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
3, T
2 and T
4 was 14.22%, 13.89%, 13.75%, 11.63%, 10.28%, 7.64%, 7.51%, 5.31%, 4.69% and 1.97% at Bathinda respectively.
The reduction in the NDF might be due to increased succulence by reducing the formation of polysaccharides such as lignin, cellulose and hemicellulose which generally account for NDF content in plant because of biological nitrogen fixation by
Burkholderia seminalis,
Burkholderia sp. and
Bradyrhizobium sp. These results are in agreement with the findings of Patel
et al., (2012) who reported that increased supply of N fertilization and other minerals resulted in decreased levels of NDF content in fodder maize.
Crude protein (CP)
Dietary proteins are vital constituents of animal feed and its nutritional and functional properties affect the overall quality of the feed. As a legume, cowpea is a rich and low-cost source of proteins and nutrients (Egounlety and Aworh, 2003). Crude protein is an estimate for the total proteinThe data showed non-significant effect of liquid microbial inoculant on crude protein content in all treatments at Ludhiana location (Table 1). Nevertheless, the percentage increase in crude protein with respect to T
1 in treatment T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
3, T
2 and T
4 was 16.38%, 16.14%, 14.29%, 9.90%, 6.77%, 6.42%, 6.37%, 6.08, 3.47% and 2.72% respectively.
However, at Bathinda, crude protein content significantly increased over the control in all treatments of liquid microbial inoculants (Table 2). Highest crude protein content was recorded with T10 treatment .The percentage increase in crude protein content of treatments T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
3, T
2 and T
4 over control are 19.27%, 18.01%, 17.00%, 14.84%, 13.52%, 12.51%, 8.08%,7.18%, 0.84% and 0.36% respectively. Treatments T
11, T
10, T
8, T
7, T
6 and T
5 showed significant improvement in crude protein content and treatments T
2, T
3, T
4 and T
9 were at par with treatment T
1.
This might be due to improved growth due to phytohormones production by the inoculated bacteria which stimulate nutrients absorption as well as photosynthesis process, as a result of which protein content increases. This is in agreement with the finding of Tesfaye
et al., (2018) who reported significant improvement of soybean crude protein content due to application of
Bradyrhizobium inoculants.
In vitro dry matter digestibility (IVDMD)
IVDMD is a very important and most demanded key quality traits for fodder production where it governs nutrient availability to animal for their health and growth. Liquid microbial inoculants showed significant effect on IVDMD content in all treatments at Ludhiana location (Table 1). The percentage increase in IVDMD over T
1 in treatment T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
3, T
2 and T
4 was 12.49%, 12.41%, 11.90%,7.65 %, 6.87%, 5.27%, 4.82%, 2.80%, 2.57% and 2.26% respectively. Moreover, treatments T
2, T
3 and T
4 were at par with treatment T
1 and treatments T
5, T
6, T
7, T
8, T
9, T
10 and T
11 showed significant improvement in IVDMD content over T
1. However, IVDMD content was non-signficantly affected by all the treatments of liquid inoculants at Bathinda. Accordingly, the percentage increase in IVDMD content of treatments T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
2, T
3 and T
4 over control (T
1) was 12.27%, 9.71%, 9.35%, 9.23%, 7.39%, 6.18%, 6.08%, 5.82%, 5.05% and 1.55% respectively. Positive response of IVDMD to the application of different inoculant treatments (
Burkholderia seminalis,
Burkholderia sp. and
Bradyrhizobium sp.) might be due to the phosphate solubilizing activity of the inoculated cultures. Further, improved availability of phosphorus could be considered as an important means to improve the nutritional value of cowpea forage. These findings were in line with earlier studies of
Reddy et al., (2003) who reported that inoculation of cereal seed with nitrogen fixing bacteria such as
Azotobacter and seed of pulses with phosphate solubilizing bacteria resulted in decreased fertilizer requirement and improved crude protein and IVDMD (
In vitro dry matter digestability) of fodder.
Ash content
The ash content of feed resources (%) non-significantly influenced by the different treatments of liquid microbial inoculants. In our study highest ash content was observed with T
10 followed by T
5. The percentage increase in ash content over T
1 was 25.05%, 23.19%, 22.70%, 22.60%, 19.28%, 18.79%, 18.00%, 17.51%, 2.05% and 1.96% in T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
3, T
2 and T
4 respectively at Ludhiana (Table 1). At Bathinda location, liquid inoculants had significant effect on ash percentage (Table 2) and ash content varied from 9.11% (T
1) to 11.55 % (T
10). Moreover, the treatments T
2, T
3, T
4, T
7, T
8 and T
9 were at par with T
1 whereas treatments T
5, T
6, T
10 and T
11 showed significant improvement in total ash content. The percentage increase in ash content over T
1 was 26.78%, 23.93%, 15.81%, 15.04%, 12.62%, 12.29%, 4.83%, 2.85%, 2.09% and 0.33% in T
10, T
5, T
11, T
6, T
8, T
7, T
9, T
2, T
3 and T
4 respectively. The increase in total ash percentage in treatments with liquid microbial inoculants might be due to the production of growth promoting hormones such as auxin, cytokinin and gibberellin through
Burkholderia seminalis,
Burkholderia sp. and
Bradyrhizobium sp. and improved growth due to mineral nutrient uptake from the soil which in turn might have resulted in increased total ash content. This was in line with those
Shahverdi et al., (2014) who reported that native
rhizobium with reduced application of chemical fertilizers treatment as compared to no application of biological fertilizers with recommended chemical fertilizers showed increased ash percentage (3.25%) in Persian clover (
Trifolium rosapinatum L.).
Total sugars
Data regarding the total sugar content has been presented in Table 1 and Table 2. The application of liquid microbial inoculants significantly increased total sugar content in leaves over the control at Ludhiana (Table 1). However, maximum total sugar content was recorded in T
10 (15.82 mg/g) while minimum total sugar content was noted in the T
1 treated plants (14.97 mg/g). However, the treatments T
3,T
5, T
6, T
7, T
8, T
4,T
9, T
10 and T
11 improved significantly over the treatment T
1. Similarly, significant increase in the total sugars content was observed in the treatments with liquid microbial inoculants at Bathinda location. Maximum total sugars were recorded by T
10 treatment (15.80 mg/g) and minimum total sugar was recorded by T
1 treatment (14.97 mg/g). The treatments T
3, T
5, T
6, T
7, T
8, T
9, T
10 and T
11 improved significantly and the treatments T
2 and T
4 were found to be at par with T
1.
The improved sugar content due to supplementation with microbial inoculants might be due to better absorption and mobilization of nutrients by the action of
Burkholderia seminalis, Burkholderia sp. and
Bradyrhizobium sp.The results were in conformity with Stancheva
et al., (2016) who reported that
Bradyrhizobium japonicum solely and in combination with
arbuscular mycorrhizal fungi increased the content of proteins, soluble sugars and total phenols in the cowpea.
Correlation analysis of quality attributes
Correlation analyses are being widely used in many crop species by the plant breeders to understand the nature of complex interrelationships among the traits and to identify the sources of variation in yield
(Finne et al., 2000).
The data pertaining to the correlation between the quality components as influenced by the liquid microbial inoculants has been presented in Fig 1 for Ludhiana location and Fig 2 for Bathinda location. Interpretation of data revealed positive correlation between ADF% and NDF%. However, both these parameters were found to be negatively correlated with other quality parameters at both the locations. This might be due to the fact that lignin and cellulose component of ADF are also component of NDF.
Eskandari et al., (2009) also reported that acid detergent fibre and neutral detergent fibre are major indicators of digestibility which negatively affects feed quality. Further, in present investigation liquid microbial inoculants were found to reduce the ADF and NDF percentage.
Likewise, crude protein component of forage cowpea found to exhibit significant positive correlation with IVDMD, chlorophyll content, and total phenols whereas at Bathinda location, CP found to be significantly correlated with IVDMD, total sugars and total phenols. Similarly, IVDMD found to be significantly correlated with chlorophyll, total sugars and total phenols at Ludhiana location and at Bathinda location, it was found to be significantly correlated with total ash in addition to chlorophyll, total sugars and total phenols. Similar results were seen by Anup and Vijaykumar (2000). IVDMD were also found to have positive significant correlation with total sugars and total ash content. These results were at par with Kaur and Thakur (2016) who reported that IVDMD showed positive association with carbohydrate fractions (TCHO) of energy feeds.
Total ash content found to be significantly correlated with chlorophyll, total sugars and phenolic content at both the locations. Furthermore, chlorophyll content of the leaves was found to significantly correlate total sugars and phenol at Ludhiana location and at Bathinda location, it was only significantly correlated with total phenols. Further at both the locations, total sugars and total phenols found to be significantly correlating with each other.
The results of correlation studies revealed that ADF and NDF had negative correlation with CP indicating that the higher CP would suggest lower fibre content in fodder crops and could be taken as one of the selection criteria. Our results were in accordance with previous studies on ADF content in cowpea
(Devasena et al., 2009) and NDF content in cowpea
(Prusty et al., 2013). Thus, the use of liquid microbial inoculants resulted in increased CP and IVDMD content and lowered ADF and NDF content. Thereupon, ascertaining their positive role in improving cowpea fodder quality traits.
Turk et al., (2015) also reported that the selection for increased crude protein would result in lower fibre concentration which would be desirable from the standpoint of forage quality. Maximum improvement observed in the quality paramenters was with 75% of RDF +
Burkholderia sp. +
Burkholderia seminalis followed by 100% RDF+
Burkholderia sp. +
Burkholderia seminalis.
