Non-traditional Straws: Alternate Feedstuffs for Ruminants

The nutritive value of 4 straws, obtained after thrashing of seeds from fodder crops, was assessed as complete feed for ruminants. Sixteen male Murrah buffaloes (liveweight 365.8±19.5 kg), were divided into 4 equal groups and offered ad lib. straw of either Trifolium resupinatum, Trifolium alexandrium, Medicago sativa or Lolium perenne, supplemented with minerals and vitamin A, for 40 days in a completely randomized design. Simultaneously, each straw was offered to 3 rumen fistulated male buffaloes in order to assess the biochemical changes in the rumen. Compared to other straws M. sativa straw had higher (p<0.05) organic matter (OM), crude protein (CP), acid-detergent fiber (ADF) and cellulose content. L .perenne had the highest (p<0.05) hemicellulose and lowest (p<0.05) CP and acid-detergent lignin (ADL) content. T. resupinatum had the lowest concentration of cell wall constituents (CWC). The digestibility of nutrients of T. resupinatum and L. perenne straw was similar, but higher (p<0.05) than that of other straws. M.sativa straw showed highest (p<0.05) digestibility of CP. The highest OM digestibility of T. resupinatum and CP digestibility of M. sativa were responsible for highest (p<0.05) total volatile fatty acids and trichloroacetic acid precipitable nitrogen in the strained rumen liquor. The digestible crude protein (DCP) was highest (p<0.05) in M. sativa followed by that in T. alexandrium. The total purine derivatives excreted in urine varied from 0.22-0.32 mmol/kg W/d. The efficiency of microbial protein synthesis indicated that OM of straws of M. sativa and that of T. alexandrium was used more (p<0.05) efficiently. The microbial protein synthesized was highest in T. resupinatum, but statistically similar to other groups. The values for N-retention and apparent biological value were highest for L. perenne, though comparable with that of M. sativa and T. alexandrium. The available metabolizable energy (ME) was highest (p<0.05) in T. resupinatum followed by that in L. perenne and lowest in M. sativa. It was concluded that all the straws, supplemented with minerals and vitamin A, could be fed exclusively to adult ruminants with no adverse affect, as animals were able to maintain body weight (372±20.1 kg). (


INTRODUCTION
India proudly occupies first position in livestock population (464 million) and milk production (88MT) and to sustain this position, 300×10 6 adult cattle units (1 adult unit = 450 kg live weight) are to be fed, but there is shortage of 26 million tons (MT), 280 MT and 44 MT of concentrates, green forages and straws/stovers, respectively (Bakshi and Wadhwa, 2004).Due to competing pressures on land, ironically the green revolution and diversified use of agricultural crop residues, the gap between the demand and supply of feedstuffs is increasing.
The nutritive value of feeds and fodder has a significant bearing on productivity of livestock.In most of the developing countries, the conventional cereal straws and stovers constitute the bulk of DM consumed by low and medium yielders under field conditions.These straws generally have poor nutritive value (Ranjhan and Pathak, 1979).In this situation, there is a need to either improve the efficiency of utilization of existing feed resources or to tap the newer non-conventional feed resources.
There is little scope for increasing the area under fodder production.Efforts, therefore, have been made to improve the quality of existing green forages, to increase per acre yield of fodder and to develop new fodder varieties, to ensure sufficient availability of green fodder to the livestock.The leftover material i.e. the straw (obtained after thrashing/collection of seeds) from the leguminous/nonleguminous fodder crops, currently being used as soil conditioner or burnt in the field, thereby causing environmental pollution.The average straw production from T. alexandrium, T. resupinatum, M. sativa and from L. perenne was 30, 37, 15 and 62 Q/ha, respectively.Such straws if utilized judiciously, can bridge the gap between demand and supply.Such byproducts of forage crops could be exploited as livestock feed.This study was therefore, planned to assess the nutritional value of leguminous and non-leguminous straws for buffaloes.

Feedstuffs
The straws of 4 different multi-cut, rabi fodder crops of Punjab viz.Trifolium resupinatum (shaftal), Trifolium alexandrinum (berseem), Medicago sativa (alfalfa) and Lolium perenne (rye grass), sown in febrile loamy soil with good drainage in October (when the ambient temperature and relative humidity is around 24°C and 67%, respectively), were procured from the Plant Breeding Department of Punjab Agricultural University, Ludhiana.The seeds are usually ready by the end of May-June (when average ambient temperature and relative humidity is around 31°C and 49%, respectively) and were thrashed mechanically (Trifolium alexandrinum and Medicago sativa) or manually (Trifolium resupinatum and Lolium perenne).

Digestibility trial
Each straw was offered ad lib., supplemented with mineral mixture (calcium 16%, phosphorus 9%, magnesium 4%, sulphur 1.4-2.3%,iron 0.3%, copper 0.078%, zinc 0.64%, manganese 0.10%, cobalt 0.009%, iodine 0.02%, acid insoluble ash 2.4%, lead 16 mg/kg and arsenic 5 mg/kg), common salt and vitamin A, as a complete feed once-a-day at 9 h, individually to 4 male Murrah buffaloes (live weight 365.8±19.5 kg).Fresh water was offered twice a day.The animals were adapted for 30 days followed by a 7-day metabolism trial.During the trial, the animals were kept in metabolism cages and a record of feed intake, orts, faeces and urine voided was maintained.The animals were weighed at the beginning and at the end of the experimental period for 3 consecutive days.Samples of feedstuffs and orts were collected at 24 h interval and dried in duplicate at 80°C in a forced air oven.Urine voided by the experimental animals was collected in plastic cans (containing 500 ml of 20% sulphuric acid in order to maintain the pH below 3) attached to a urine collection duct underneath the floor of metabolism cages.An aliquot of 5 ml was diluted to 25 ml with distilled water and kept in a deep freezer at -20°C until analyzed for purine derivatives (PD) and creatinine (CRT).For nitrogen estimation, 1% of the total urine was preserved in bottles daily which were kept in a refrigerator till analyzed.The faeces voided were collected manually and kept in iron drums (30 kg capacity) for 24 h, weighed and mixed; 0.5% duplicate samples were weighed into aluminum trays for DM determination.For nitrogen estimation, 0.25% of total faeces was preserved in previously tared, wide-mouth plastic bottles daily, containing 25 ml sulphuric acid (20 %v/v).

Rumen studies
Each straw supplemented with minerals and vitamin A was offered as complete feed to 3 rumen fistulated male Murrah buffaloes (live weight 451.2±12.5 kg) ad lib.for a 30 day adaptation period.Thereafter, samples of rumen contents were collected before feeding and then at 2 h interval up to 10 h post-feeding.The rumen contents were strained through 4-layered muslin cloth and pH was determined (digital pH meter) immediately after collection.The strained rumen liquor (SRL) was preserved with a few drops of saturated mercuric chloride and stored at 4°C till analyzed.

Analytical methods
Finely ground (1 mm) samples of straws, feeding residues and faeces were analyzed for moisture, CP and total ash (AOAC, 1990), cellulose (Crampton and Maynard, 1938) and other cell wall constituents (Robertson and Van Soest, 1981).The SRL was analyzed for total-N, ammonia-N (AOAC, 1990), trichloroacetic acid precipitable-N (TCA-N; Cline et al., 1958), and total volatile fatty acids (TVFA; Barnet and Reid, 1957).The NPN was calculated by subtracting TCA-N from Total-N.The ME was determined from apparent digestible OM using the relationship given by Broster and Oldham (1981).The urine samples were analyzed for total-N (AOAC, 1990), allantoin (Young and Conway, 1942), uric acid (Trivedi et al., 1978) and creatinine by the method of Folin and Wu described by Hawk et al. (1976).Purines absorbed were calculated from the urinary PD excreted using the equation of Chen et al. (1990).Efficiency of microbial protein synthesis (EMPS) was expressed as microbial nitrogen production (g) /kg digestible OM fermented in the rumen (DOMR); DOMR was taken as 0.65 of the apparent digestible OM intake and purine nitrogen index (PNI) presents the ratio between purine-N and total -N in urine.

Statistical analysis
The data were analyzed according to a completely randomized design (Snedecor and Cochran, 1994) using STATGRAPHICS Version 5.0.The differences between means were compared by Duncan's multiple range test (Duncan, 1955).

RESULTS AND DISCUSSION
The CP content of non-conventional straws ranged from 64 (L.perenne) to 86.9 (M.sativa) g/kg DM.M. sativa straw had higher (p<0.05)OM, CWC and CP content (Table 1).Nath et al. (1990) and Dahiya et al. (1998) reported much lower CP content (58 to 61 g/kg DM) in berseem straw.The CP content in these straws was much higher than that reported (28-47 g/kg DM) for traditional cereal (wheat and paddy) straws, pearl millet or sorghum stalks or maize stovers (Bakshi and Langar, 1994), but comparable with urea-treated naturally fermented wheat straw and other crop residues (Bakshi et al., 1986;Bakshi and Langar, 1994;Bakshi and Wadhwa, 2001).The NDF content in M. sativa (810 g/kg DM) and L. perenne (800 g/kg DM) was similar but higher (p<0.05)than the straws of Trifolium spp.(650 to 680 g/kg DM).The straw of L. perenne, being nonleguminous in nature, had the highest (p<0.05)hemicellulose, lowest (p<0.05)CP and ADL content as compared to other straws.The bound nitrogen or acid detergent insoluble-N (ADIN) was lowest (p<0.05) in M. sativa and highest (p<0.05) in T. resupinatum.The straw of T. alexandrium had higher ADL content than T. resupinatum, resulting in low digestibility of nutrients (DM, CWC and cellulose).The ADL content in leguminous fodder straws was much higher (5.1 to 7.6%) but that of L. perenne was comparable to that of traditional cereal straws, millet stalks and stovers (Bakshi and Langar, 1994).
DM intake, expressed on liveweight basis, was highest (1.89%) for L. perenne and lowest (1.66%) for M. sativa; however, the differences were statistically non-significant (Table 2).The DM consumption of T. alexandrium was higher (1.9 vs. 1.4% of body weight) than reported by Dahiya et al. (1998).The digestibilities of DM, OM and that of ADF were highest (p<0.05) for T. resupinatum followed by the digestibility values for L. perenne straw.NDF and cellulose of L. perenne straw was highly digestible.The CP of M. sativa was more (p<0.05)digestible than that of other straws.The digestibilities of most of the nutrients in T. alexandrium and M. sativa were similar, but lower (p<0.05)than those of T. resupinatum and L. perenne straws.The digestibilities of DM and CP of these straws were similar, though that of CWC was much lower than that of naturally fermented wheat straw (Bakshi and Langer, 1994;Bakshi and Wadhwa, 2001).Nath et al. (1990) reported DM digestibility within a comparable range, although CP digestibility was above the expected value for T. alexandrium straw.The higher digestibility of nutrients (OM) in animals fed T. resupinatum straw resulted in higher (p<0.05)TVFA production in the rumen (Table 3) as compared to that of T. alexandrium.The high VFA concentration in the rumen for T. resupinatum, L. perenne and M. sativa suggested a higher microbial activity.The total-N concentration in the SRL was higher in animals fed L. perenne straw, though differences between straws were statistically non-significant.The highest concentration of TCA-N was observed in animals fed M. sativa straw, which could be due to significantly higher CP content and digestibility.L. perenne straw showed similar results to those of M. sativa.Minimum ammonia-N concentration was observed in the SRL of animals fed L. perenne straw.The N-fractions, expressed as percent of total-N, showed that TCA-N constituted 54.2% in T. alexandrium and 67.8% in M. sativa.Topps and Elliott (1965) and Kanjanapruthipong and Leng (1998) showed that urinary excretion of PD provide an indicative and noninvasive method for predicting synthesised microbial protein that leaves the rumen and is digested in the intestines.Urinary allantoin excretion was similar in all the groups (Table 4).Uric acid excretion was higher (p<0.05) in animals fed T. resupinatum or T. resupinatum straw than that in animals fed either M. sativa or L. perenne straw.However, urinary excretion of total PD was similar (0.22 to 0.32 mmol/kg W 0.75 /d) in all the groups.Allantoin constituted 72-78% of PD excreted.Allantoin has been reported to be the main constituent total PD excreted as also observed in cattle urine (Chen et al., 1995;Susmel et al., 1994;Chen and Gomes, 1995).Allantoin and uric acid are the PD present in cattle urine because of high xanthine oxidase activity which, converts xanthine and hypoxanthine into uric acid prior to excretion (Valadares et al., 1999;Pimpa and Liang, 2002).PNI indicates the efficiency with which degradable nitrogen is converted to microbial protein in the rumen (Chen and Jayasuria, 1997;Chen et al., 1999).The PNI values were lowest (0.041) in animals fed M. sativa straw and highest (0.084) in those fed L. perenne and T. resupinatum straw, clearly indicating poor conversion efficiency of M. sativa straw (Table 5); however, the supply of microbial protein to the host animal was higher in animals fed M. sativa straw and lowest in animals fed L. perenne straw.The urinary excretion of creatinine ranged between 0.61-0.77mmol/kg W 0.75 /d.It was higher (p<0.05) in animals fed T. resupinatum or T. alexandrium straw than in animals fed either M. sativa or L. perenne straw.The ratio of PD to creatinine concentration in urine ranged from 0.37 (L.perenne) to 0.44 (M.sativa).The ratio of PD to creatinine corrected for metabolic weight was lowest for L. perenne (31.3) and highest for animals fed M. sativa straw (36.6).Moscardini et al. (1999) reported similar values for buffaloes.The allantoin/creatinine ratio, an index of total allantoin excretion in urine and an indicator of rumen microbial protein synthesis (Gonda, 1995), was not affected by dietary treatments and averaged 2.92 (p>0.05).The daily N intake was highest (p<0.05) for T. alexandrium straw followed by that for M. sativa straw (Table 5).The excretion of N in faeces was greater (p<0.05) in animals fed Trifolium straw than on the other straws.On the contrary, the animals fed M. sativa straw excreted more urinary-N.The minimum urinary-N excretion was observed in animals fed L. perenne straw.High excretion of urinary N (22.7 to  38.0 g/d) on feeding these fodder straws, other than L. perenne, might be indicative of inefficient capture of ruminal NH 3 -N (Table 3) for microbial protein synthesis.The Total-N excretion was higher in animals fed T. alexandrium straw, but when expressed as a percent of N intake it was greater in animals fed T. resupinatum straw.The higher TCA-N in M. sativa and L. perenne was responsible for minimum N-excretion resulting in higher Nretention and apparent biological value.The poor digestibility and inefficient utilization of N in T. resupinatum straw by the buffaloes could be due to high ADIN content in this straw.The N-retention from these straws was comparable to that obtained with naturally fermented cereal straws, millet stalks and maize stovers fed to buffaloes (Bakshi and Langar, 1994).
The nutritive value of different straws revealed that the straw of M. sativa had the highest (p<0.05)DCP content followed by that in T. alexandrium (Table 5).The T. resupinatum straw had the lowest DCP value, N-retention and apparent biological value, but it had higher (p<0.05)available ME as compared to other straws.The DCP content in traditional cereal (wheat and rice) straws is negligible and the ME availability varies between 5.8 and 6.6 MJ/kg DM (Mc Donald et al., 1977;Ranjhan and Pathak, 1979).Animals fed these non-traditional straws maintained body weights (Table 5) indicating the capability of these feedstuffs to meet the basal requirements of ruminants, unlike the traditional straws such as wheat and rice.

CONCLUSION
The results conclusively revealed that nutritionally, all four evaluated un-conventional straws of fodder crops could meet the basal maintenance requirements of adult buffaloes.
Figures with different superscripts in a row differ significantly, p<0.05.

Table 1 .
Chemical composition of the straws (g/kg DM)

Table 2 .
Voluntary dry matter intake and digestion parameters in Murrah buffaloes fed four different straws DMI: Dry matter intake, NDF: Neutral detergent fiber, ADF: Acid detergent fiber.Figures with different superscripts in a row differ significantly, p<0.05.

Table 3 .
pH, volatile fatty acids and N fractions in the rumen liquor of Murrah buffaloes fed four different straws

Table 5 .
Nitrogen retention (g/d) and body weight changes in Murrah buffaloes fed four different straws : Nitrogen, BV: Biological value.ME: Metabolizable energy, DCP: Degestible crude protein.Figures with different superscripts in a row differ significantly, p<0.05. N