Dietary influences on bacteriophage numbers in the rumen

Abstract

Animal Production in Australia 1998 Vol. 22 DIETARY INFLUENCES ON BACTERIOPHAGE NUMBERS IN THE RUMEN A.V. KLIEVE, A.F. TURNER, and G.L. HECK Dept of Primary Industries, Animal Research Institute, Yeerongpilly, Qld 4105 Bacterial lysis within the rumen is considerable and is a major source of feed utilization inefficiency. Bacterial viruses (bacteriophages) are implicated in this lysis. Bacterial viruses are obligate pathogens of bacteria and occur in dense populations in the rumen (Klieve and Swain 1993). Preliminary findings suggested that feed components affect phage activity. The aim of this study was to gauge whether diet type did have a marked influence on the size of the bacteriophage population in the rumen. A survey was undertaken of the total phage numbers present in the rumen contents of beef cattle (Bos taurus and Bos indicus), dairy cattle and sheep fed diets of fresh forage, dry forage and grain, with and without a variety of supplements. The animals used were either fitted with a rumen cannula, through which rumen fluid was removed, or rumen contents were aspirated through a tube placed into the rumen through the mouth. Rumen fluid samples were processed and the total amount of bacteriophage DNA was determined as previously described (Klieve and Swain 1993). The results are summarized in Table 1. Table 1. Total phage DNA (m g/ ml of rumen fluid) in rumen contents of beef cattle, dairy cattle, and sheep fed fresh forage, dry forage and supplements in various amounts as percent of liveweight (w) Feed type Supplement Number and type of animals (S) - stomach tube sampled (C) - rumen cannulae sampled. six beef cattle (Bos indicus X) (S) two beef cattle (Bos indicus X) (S) two beef cattle (Bos indicus X) (S) three beef cattle (Bos indicus X) (S) three beef cattle (Bos indicus X) (S) nine beef cattle (Bos taurus) (C) three beef cattle (Bos indicus X) three beef cattle (Bos indicus X) three beef cattle (Bos indicus X) two beef cattle (Bos indicus X) ( three beef cattle (Bos indicus X) three beef cattle (Bos indicus X) three beef cattle ( Bos indicus X) three beef cattle (Bos indicus X) four sheep (C) three sheep (C) three Friesian steers. (C) (S) (S) (S) S) (S) (S) (S) (S) Av. total phage DNA (�g/ml) 14.83 8.94 10.32 5.65 14.40 13.55 5.88 3.03 4.41 6.28 3.98 3.81 1.40 6.11 4.54 5.48 5.32 0.77 1.59 s.e. Fresh pasture Buffel grass Buffel grass Buffel grass Buffel grass Buffel grass Kikuyu grass Dry forage Rhodes grass hay Rhodes grass hay Rhodes grass hay Rhodes grass hay Rhodes grass hay Rhodes grass hay Rhodes grass hay 1:2 Lucerne:Rhodes 1:3 Lucerne:Oatenhay 1:3 Lucerne:Oatenhay Barley chop + Rhodes Grass Hay Feedlotted Barley:Sorghum 60:24 Barley:Sorghum 60:24 Sorghum, 2% w CSM, 1.5% w Sorghum, 0.8 to 2% w 3.69 3.42 0.42 3.90 5.84 1.83 2.17 0.34 1.07 2.01 0.60 1.36 0.25 3.15 0.34 1.71 2.11 0.09 0.39 CSM, 0.5% w CSM, 1% w CSM, 1.5% w CSM, 2% w Fishmeal, 0.2 to 0.8% w Molasses, 1.5 to 2% w 2 kg CSM Bentonite High P: Ca Low P: Ca nine beef cattle (Bos indicus X) (S) eight beef cattle (Bos indicus X) (S) Animals feeding on green pasture tended to have high phage numbers whereas those on dry feed had fewer phage (30 to 50%), and feedlotted animals much fewer again (10% of those at pasture). This trend appeared to be unaffected by animal species or the feeding of supplements. The results suggest that the extent of phage activity in the rumen, and hence bacterial lysis, is influenced by the diet and if the triggers to the higher activities can be found it may be possible to reduce phage mediated bacterial lysis through dietary manipulation. KLIEVE, A.V. and SWAIN, R.A. (1993). Appl. Environ. Microbiol. 59, 2299-2303. 341