Nutritional evaluation of baby corn fodder and conventional maize fodder in buffaloes

M P S Bakshi, M Wadhwa and Balwinder Kumar¹

Department of Animal Nutrition, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana-141 004, India
bakshimps@yahoo.com
¹ Krishi Vigyan Kendra, Taran Taaran

Abstract

After picking baby corn ears for human consumption, the leftover green plants/stalks available in plenty as a byproduct is called baby corn fodder. This study was conducted to assess the nutritive value of baby corn (5414-Egyptian variety) fodder in comparison to conventional maize fodder ( Zea maize; J-1006 variety) both by in vitro gas production technique (IVGPT) and by a feeding trial on buffaloes. Eight male buffaloes (live weight 407.8 ± 6.85 kg) divided into two equal groups were offered ad-lib either conventional maize fodder or baby corn fodder supplemented with mineral mixture and common salt.

Both the fodders had comparable proximate and cell wall constituents, except that the CP content was higher (P<0.05) in baby corn fodder than conventional maize fodder. The nutritional evaluation by IVGPT revealed that the net gas production (NGP), digestibility of NDF and true OM; total and individual volatile fatty acids like acetate, propionate and butyrate, and ME availability, was higher in baby corn than in conventional maize fodder. The results of feeding trial revealed that daily DM intake was similar in both the groups, but the digestibility of both proximate and cell wall constituents was higher in the animals fed baby corn fodder as compared to those fed conventional maize fodder. Different parameters of blood profile and purine derivatives excreted in the urine were comparable in both the groups of animals, except the PNI (purine-N index) which was higher in animals fed baby corn fodder as compared to those fed conventional maize fodder. The higher N-intake and low urinary-N excretion resulted in higher N-retention and apparent biological value in animals fed baby corn fodder as compared to conventional maize fodder. It was concluded that baby corn fodder was readily acceptable, palatable and relished by the animals as compared to conventional maize fodder.

Key words: blood profile, in vitro, in vivo, urinary purine derivatives

Introduction

The production of fresh vegetables including baby corn has increased from 239.7 to 279.7 million tonnes in 2003–2013 (FAO 2015), and it will continue to increase in the future, making available their various by-products and wastes for use as animal feed. Use of such non-food parts from agricultural products as animal feed will not only enhance food security but also contribute to alleviation of environmental problems associated with their disposal. The dehusked baby corn is eaten both raw and cooked and is a delicacy in a number of cuisines around the world. About 3–4 picks of baby corn are taken from each baby corn plant. Dehusked baby corn is the main source of income for the farmer as majority of it is exported to America, European countries and South-east Asian countries; besides selling in domestic market. In India, the average baby corn production is about 7.5–8.7 tonnes/ha. Of this edible baby corn cob is only 15%, while the remaining 85% constitutes of outer peels/husk with a silky thread-like structure called baby corn husk with silk (6.4–7.4 tonnes/ha), which has excellent nutritive value for ruminants (Bakshi and Wadhwa 2012). Another by-product is green stalks with leaves also called baby corn fodder (30 tonnes/ha) (Bakshi et al 2016). Though it is fed to the animals, but no information is available on the actual nutritive value of baby corn fodder. This study was therefore, conducted to assess the nutritive value of baby corn (5414-Egyptian variety) fodder in comparison to conventional maize fodder (J-1006) both by IVGPT and by conducting a metabolic trial on male buffaloes fed either of the fodder ad-libitum.

Material and methods

Baby corn fodder

The baby corn (5414-Egyptian variety) fodder and conventional maize fodder (J-1006 variety) were procured from university farm.

In-vitro studies

The nutritional value of conventional maize and baby corn fodder was assessed by in-vitro gas production (IVGP) technique. Three rumen fistulated male buffalo calves were offered 2.0 kg conventional concentrate mixture (maize 25, mustard cake 10, de-oiled mustard cake 20, rice bran 15, de-oiled rice bran 27, mineral mixture 2 and common salt 1 part each) supplemented with 5.0 kg green fodder and 6.0 kg wheat straw. The rumen contents were collected before feeding at 0900 in a thermos flask flushed with CO₂ and maintained at 39º C. The rumen contents were blended for 2–3 min in a blender and strained through four-layers of muslin cloth. The solution, containing 960 ml distilled water, 0.16 ml micro-mineral solution, 660 ml bicarbonate buffer, 330 ml macro-mineral solution and 1.6 ml resazurine (0.1%) were mixed in a Woulff flask (3 Litres capacity) with magnetic stirrer in a water bath at 39º C. The mixture was continuously flushed with CO₂. Then strained rumen liquor (SRL) was added to the buffer media in the ratio of 1:2. About 375 ± 5 mg of the dried ground baby corn fodder and conventional maize fodder (on DM basis) was incubated at 39^oC for 24h in triplicate in 100 ml calibrated glass syringes (Haberle Labortechnik, Germany) with buffered rumen fluid for assessing the net gas production, digestibility of nutrients, VFA production and ME availability. Blank and sample of standard hay were run in triplicate with each set. Syringes were incubated in a water bath at 39º C and swirled every 60 min over a 8h incubation period. If the volume of gas in the syringe exceeded 70 ml after 8 h the volume was recorded and the gas was expelled (Menke et al 1979, Menke and Steingass 1988). After 24 h, the volume of gas produced in each syringe was recorded and the contents of syringes were transferred to spout-less beaker, boiled with neutral detergent solution for assessing the true OM and NDF digestibility. Three sets of samples were incubated, each in triplicate.

Estimation of volatile fatty acids

After 24 h of incubation, a 5 ml aliquot of fluid from each syringe was mixed with 1 ml of 25% meta-phosphoric and kept for 1 h at ambient temperature. Thereafter, it was centrifuged at 5500 rpm for 10 min and clear supernatant was collected and stored at -20º C until analyzed. The volatile fatty acids (VFAs) were estimated using Netchrom 9100 gas chromatograph equipped with glass column (packed with chromosorb 101) and flame ionization detector (Cottyn and Boucque 1968). Temperature of injection port, column and detector was set at 250, 175 and 270º C, respectively. The flow rate of carrier gas (N) through the column was 15 ml min^-1; and the flow rate of H₂ and air through FID was 30 and 300 ml min^-1, respectively. Sample (2 ml) was injected through the injection port using a Hamilton syringe (10 µl). Individual VFA’s of the samples were identified on the basis of their retention time and their concentration (mmol) and calculated by comparing the retention time as well as the peak area of standards after deducting the corresponding blank values.

In-vivo evaluation on adult male buffaloes

Animal feeding

Eight male buffaloes (live weight 407.8 ± 6.85 kg) divided into 2 equal groups were offered either maize fodder (Zea maize; J-1006) or baby corn fodder (5414-Egyptian variety). The respective fodder, supplemented with mineral mixture and common salt, was fed ad libitum as complete feed once a day at 9 hrs. Fresh water was offered twice a day. The animals were adapted on respective diet for 30 days followed by 7 days metabolism trial. During the trial, the animals were kept in metabolic cages and feed intake, faeces, orts and urine voided were recorded. Urine was collected over 500 ml of 20% sulphuric acid to maintain the pH below 3. A portion of urine sample was diluted five times with distilled water, kept in a deep freezer at -20⁰C, till analyzed for purine derivatives (PD) and creatinine (CRT). The animals were weighed at the start and at the termination of experiment for 3 consecutive days. At the termination of metabolism trial, blood samples were collected by puncturing the juglar vein at 4 h post feeding.

Analytical methods

The finely ground samples of feedstuffs, orts and faeces were analyzed for DM, CP and total ash (AOAC 2000), cellulose (Crampton and Maynard 1938) and other cell wall constituents (Robertson and Van Soest 1981). The urine samples were analyzed for total-N (AOAC 2000), allantoin (Young and Conway 1942) and uric acid (Trivedi et al 1978). Purines absorbed were calculated from the purines derivatives excreted in the urine (IAEA 1997). Purine nitrogen index (PNI) represents the ratio between purine derivative-N and total-N in urine. For ammonia estimation, 5 ml of supernatant was mixed with 1 N NaOH and steam distillated and the NH₃ evolved was collected in boric acid solution containing mixed indicator and titrated against 0.01N H₂SO₄ (AOAC 2000). The serum samples were analyzed for total proteins (Henry et al 1974), albumin (Doumas et al 1975), glucose (Trinder 1969) and urea-N (Evans 1968). Globulin was calculated by difference between total protein and albumin.

Statistical analyses

The data were analyzed by using simple ANOVA (Snedecor and Cochran 1994). The data was analyzed by using SPSS (2007) version 16.0 and the means were tested for the significant difference by using Tukey’s b test.

Results and discussion

The average fresh green fodder yield of conventional maize variety (J-1006) was higher than that of baby corn (G-5414) fodder (327 vs. 257q/ha, respectively). The conventional maize fodder and baby corn fodder had comparable proximate and cell wall constituents, except that the crude protein (CP) content was higher in baby corn fodder than in conventional maize fodder (Table 1).

The nutritional evaluation by IVGP technique revealed that the net gas production (NGP), digestibility of NDF and true OM; total and individual volatile fatty acids like acetate, propionate and butyrate; and ME availability was higher in baby corn than that of conventional maize fodder (Table 2). But the relative proportion of acetate, propionate and butyrate was similar in both the fodders. The IVGP studies clearly revealed that baby corn fodder was superior to the conventional maize fodder.

Encouraged by the results of IVGP studies, both the forages were fed ad-lib to adult male buffaloes for their nutritional evaluation. The daily DM intake of buffaloes fed baby corn fodder and conventional maize fodder was similar. The digestibility of DM and OM and that of cell wall constituents was  higher in the animals fed baby corn fodder as compared to those fed conventional maize fodder (Table 3).

The blood profile of buffaloes revealed that the different parameters were statistically comparable in both the groups of animals (Table 4). The levels of different tested parameters were well within the normal range, indicating that the tested forages did not show any adverse effects on blood profile of the animals.

The urine of the animals was also tested for purine derivatives (PD) as these have been used as a tool to predict efficiency of microbial protein synthesis (Chen et al 1990, Balcells et al 1991). The urinary excretion of uric acid and allantoin; and total purine derivatives were comparable in both the groups. The proportion of allantoin and uric acid as percent of total purine derivatives was well within the normal range. The purine derivatives absorbed and the microbial protein synthesized were statistically comparable. But the PNI (purine-N index), which indicated the efficiency of microbial protein synthesis was higher in animals fed baby corn fodder as compared to those fed conventional maize fodder (Table 5).

The higher CP content in baby corn fodder and considerably higher DM intake in animals fed baby corn fodder, resulted in higher N-intake in animals fed baby corn fodder as compared to those fed conventional maize fodder (Table 6). The faecal-N excretion was comparable in both the groups, while urinary-N excretion was lower in animals fed baby corn fodder than those fed conventional maize fodder. It resulted in higher N-retention and N-retained as percent of absorbed i.e apparent biological value of protein in animals fed baby corn fodder as compared to conventional maize fodder (Table 6), indicating better efficiency of utilization of nutrients from baby corn fodder.

Conclusion

• Besides getting handsome amount by selling dehusked baby corn cobs for human consumption, the dairy farmers can get additional income by feeding fodder to dairy cattle.
  
  
• The results revealed that baby corn fodder obtained after picking baby corn cobs for human consumption had higher palatability, digestibility of nutrients and efficiency of utilization of nitrogen as compared to conventional maize fodder and that it can serve as an excellent fodder for dairy animals.

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Received 25 March 2017; Accepted 26 March 2017; Published 2 July 2017

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