Poster 6.2: Rumen metabolism of sheep fed silage containing poultry litter - Shahid Rasool, S.H. Raza and Tanveer Ahmad

INTRODUCTION

The use of molasses not only improves the energy content of silage but also ensures low pH and prevents proteolysis. The nitrogen (N) concentration of the cereal and grass silages, which is generally low, can be improved considerably, without affecting its fermentation characteristics, by the addition of poultry waste at the time of ensiling. Ensiling poultry waste with cereal forages and grasses not only considerably increases their inherent low N concentration but also provide many basic nutrients such as energy, calcium, phosphorus and micronutrients. In this way the poultry waste can be recycled as feed for livestock with no undesirable effects on animal health. The aim of this study was to determine the effect on the rumen metabolism of sheep of feeding silage containing broiler litter.

MATERIALS AND METHODS

Commercial broiler house litter was sun dried, ground and stored for silage making. A representative sample of litter was analysed for total N, protein N, ammonia N, ash, fibre fractions, silica (Van Soest and Robertson, 1982) and non-fibre carbohydrates. Dried broiler litter(1) (30% DM) and cane molasses (60% of DM) were added to chaffed Sudax fodder (SPL-Silage) for silage making. Control silage without litter was also prepared. To determine chemical changes during ensiling, triplicate samples of each silage were analysed at the start and on 40th day, when opened. Samples were analysed for DM, total N, protein N, ammonia N and lactic acid. Since the poultry litter had a high silica concentration, which dissolves in neutral detergent but not in acid detergent, adding the difference in silica between ADF and NDF to the apparent hemicellulose values made a correction. Lignin was determined as acid detergent (AD) lignin and cellulose as lignin free ADF (see Table 1)

Table 1. Comparative analysis of broiler litter and Sudax

Notes: All values are on a % DM basis.

Three adult rumen cannulated mature sheep were randomly allotted to one of the following rations in an experiment based on a 3 × 3 Latin Square design:

(1) Ration A: Complete farm ration.
(2) Ration B: SPL-silage.
(3) Ration C: Sudax silage + 30% concentrate mixture

All rations were formulated at 14% crude protein (CP) and 70% total digestible nutrients (TDN). Each ration was fed to a rumen-cannulated sheep for a period of 10 days as adjustment period. In the following three days, the rumen liquor samples were collected at 0, 3 and 6 hr post-feeding. The pH of rumen liquor was recorded immediately after collection with a Beckman pH meter. The rumen liquor samples were strained through four layers of cheese cloth and the filtrate was collected in 50-ml plastic bottles, each containing 2 drops of Normal H₂SO₄. After adding a few drops of chloroform, the samples were stored in a deep freezer until analysis after thawing, for total N, protein N and ammonia N.

The data on chemical analysis of rumen liquor were analysed statistically using analysis of variance technique in a factorial model (3´3 with interactions) in a Latin Square design (Steel and Torrie, 1981).

RESULTS

Data on average pH and different N fractions in rumen liquor of sheep fed on different rations is shown in Table 2. Significantly (P<0.05) higher pH was observed in rumen liquor of sheep fed the ration containing SPL silage as compared to that having Sudax silage + concentrate mixture. The changes in pH of rumen liquor of sheep at different times post-feeding were found to be non-significant (P>0.05).

Sheep fed on the complete farm ration had significantly (P<0.05) higher total N than those on SPL silage or Sudax silage + plus concentrate mixture. The sheep on SPL silage had the lowest total N concentration, and it was significantly higher (P<0.05) when Sudax silage was supplemented with concentrate mixture (Table 2). Significant differences (P<0.05) were also observed in total N concentration of rumen liquor of sheep at different times post-feeding. At zero hours post-feeding, the total N concentration of ruminal fluid of sheep on complete farm ration was significantly higher (P<0.05) than that of the other rations. The ruminal total N concentration of sheep on SPL silage and Sudax silage + concentrate mixture rations were similar at 0 hours post-feeding. At 3 hours post-feeding, the total N concentration of rumen liquor of sheep on Sudax silage + concentrate mixture ration increased and was higher (P<0.05) than those on SPL silage ration.

The protein N concentration of rumen liquor was significantly higher (P<0.01) on complete farm ration, followed by regime Sudax silage + concentrate mixture and SPL silage. The protein N concentration of rumen liquor of sheep on all ration at different times post-feeding followed a pattern similar to total N concentration.

The ammonia-N of rumen fluid of sheep fed SPL-silage was significantly higher (P<0.05) compared to complete farm ration or Sudax silage + concentrate mixture (Table 2). An ammonia-N concentration of rumen fluid was the lowest at 0 hours but it increased significantly (P <0.05) at 3 hours post-feeding, and then decreased again at 6 hours post-feeding. Following this pattern, the final ammonia-N concentration of ruminal fluid was not significantly different from that determined at 0 hours post-feeding.

Table 2. Average pH and different N fractions in rumen liquor of sheep fed different rations

Notes: (1) Ration A: complete farm concentrate; B: SPL-silage; C: Sudax silage + concentrate mixture. (2) Means within column with different superscripts differ significantly (P<0.05).

DISCUSSION

The results as shown in Table 2 indicate that the difference among rations were significant (P<0.05). It has been observed that when 3.1 to 6.0 kg poultry litter was fed to cattle in a daily ration, ammonia concentration in rumen fluid was 3 to 5 times higher than the optimal level of 10 mg/dl for maximum fermentation and optimal microbial protein synthesis (Silanikove and Tiomkin, 1992). It was stated that once the microbial requirements for N in the rumen are met, there should be no further increase in the rate of fermentation. Excessive consumption of poultry litter exposes the cow to metabolic burdens, as reflected in ammonia (>20 mg/dl) concentration and reduces the cell life span (Visck, 1984).

Ammonia concentration in rumen fluid had a direct relationship with poultry litter intake and the parallel increase with pH would encourage the absorption of ammonia from the gut (Harmeyer and Martens, 1980). Excessive ammonia, which is not utilized by the microbes, is absorbed in the blood circulation and converted to urea in the liver, with consequent metabolic burden on liver.

Rumen pH, concentration of total N, protein N and ammonia N very much depend upon the physiological status of the animal, as appeared in the experiment reported here, when sheep were fed on SPL-silage. When Sudax silage was fed with supplemental concentrate mixture, the concentrations of total N and protein N increased and that of ammonia N decreased compared with SPL-silage, yet it was less (P<0.0l) than the control. The reason being that increased DM intake reduced cell wall or structural carbohydrates, with a corresponding increase in cell contents and thus increased rate of digestion due to microbial stimulation with corresponding increases in microbial population and protein synthesis.

The pH of rumen fluid on three diets indicated the highest value on SPL-silage, probably due to high ammonia concentration. The ammonia N of the rumen fluid increased to a significantly (P<0.01) higher level, on all the three rations, at 3 hours post-feeding and again decreased to a lower level. It was probably either utilized by microbes or crossed the rumen wall, because during this time the pH of the rumen fluid was in the range of favourable ammonia absorption. The results of this trial indicate that SPL-silage alone could not support growth because it was deficient in energy, had higher concentration of soluble N, low concentration of less soluble protein and a high proportion of structural carbohydrates with correspondingly decreased microbial stimulation and low ruminal fermentation.

REFERENCES

Harmayer, J., & Martens, H. 1980. Aspects of urea metabolism in ruminants with reference to the goat. J. Dairy Sc., 63: 1707-1728.

Silanikove, N., & Tiomkin, D. 1992. Toxicity induced by poultry litter consumption: Effects on measurements reflecting liver function in beef cows. Anim. Prod., 54: 203-209.

Steel, R.G.D., & Torrie, J.H. 1981. Principles and Procedures of Statistics. Tokyo: McGraw Hill.

Van Soest, P.J., & Robertson, J.B. 1982. Analysis of Forages and Fibrous Foods. New York, NY: Cornell University.

Visck, W.J. 1984. Ammonia: its effects on biological systems, metabolic hormones and reproduction. J. Dairy Sc., 67: 481-498.