Effect of forage supplements on the incidence of bloat ...

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The Veterinary Record, August 17, 1996

zoos; unfortunately the age of death of the birds was not recorded. The situation reported in zoos and in this survey suggests that management factors may play a part, but it is more probable that the low prevalence of tumours found in exhibition birds in this survey was a reflection of their very short life span compared with pet birds. Neumann and Kummerfeld (1983) reported that the peak prevalence of renal tumours in budgerigars was between the ages of three and six years - few exhibition budgerigars reach this age. Beach (1962) reported that testicular tumours and renal tumours were the most common, with the former being most prevalent in pet type budgerigars and the latter most prevalent in breeders' birds. Renal tumours were the commonest type in the present survey in agreement with Beach's findings. Baker (1980) reported that testicular tumours were the most common type in pet birds. The findings of Anon (1981) were different with a preponderance of tumours of the liver and kidney, most of which were of a lymphoreticular type, and it was suggested that they were manifestations of the avian leucosis complex, the antigen for which has been found in other types of budgerigar renal tumours by Neumann and Kummerfeld (1983) and Gould and others (1993). If renal tumours are of an infectious nature the selling, exchanging and exhibition of birds might explain the high incidence in exhibition birds, because the virus could be disseminated by these routes. Only three lymphoreticular tumours were recorded in the present survey and no satisfactory explanation can be given for the differences between the present survey and that of Anon (1981) with regard to these tumours. There were five cases of rhabdomyosarcoma in adult birds and this tumour does not appear to have been recorded in budgerigars previously; the one case in a chick suggests that they can develop at a very early age. This work has shown that a wide variety of diseases occur in exhibition budgerigars in the UK, of which the principal one is megabacteriosis. Trichomoniasis, enteritis, pneumonia, hepatitis

and a degenerative disease of the gizzard lining are also common. Much work remains to be done on the diagnosis in life, the prevention and treatment of diseases of budgerigars, and it is suggested that efforts should be concentrated on these common conditions.

Acknowledgements.

- This work was funded by the Lancashire, Cheshire and North Wales (including the Isle of Man) Budgerigar Society and the Budgerigar Society. The author is grateful for this financial support.

References ANON (1981) The Budgerigar Society Research Digest 1979-1981. Northampton,

Budgerigar Society BAKER, J. R. (1980) Veterinary Record 106, 10 BAKER, J. R (1983) Cage and Aviary Birds September 3, pp I and 9 BAKER, J. R. (1985) Veterinary Record 116, 406 BAKER, J. R. (1986) Veterinary Record 118, 447 BAKER, J. R. (1987) Veterinary Record 121, 448 BAKER, J. R. (1989) Cage and Aviary Birds June 3, pp 3 and 15 BAKER, J. R. (1992) Veterinary Record 131, 12 BEACH, J. E. (1962) Veterinary Record 74, 10 BEACH, J. E. (1965) Journal of Small Animal Practice 6, 15 BLAKEMORE, D. K. (1963) Veterinary Record 75, 1068 GOULD, W. J., O'CONNELL, P. H., SHIVAPRASAD, H. L., YEAGER, A. E. & SCHAT, K. A. (1993) A vian Pathology 22, 33 HALLAM, C. & HALLAM, S. (1995) Cage and A eiary Birds September 23, p 5 LUMEIJ, J. T. (1994a) Avian Medicine: Principles and Application. Eds B. W. Ritchie, G. J. Harrison, L. R. Harrison. Lake Worth, Florida, Wingers Publishing. p 483 LUMEIJ, J. T. (1994b) Avian Medicine: Principles and Application. Eds B. W. Ritchie, G. J. Harrison, L. R. Harrison. Lake Worth, Florida, Wingers Publishing. p 532 NEUMANN, U. & KUMMERFELD, N. (1983) A iian Pathology 12, 353 TULLY, T. N. & HARRISON, G. J. (1994) Avian Medicine: Principles and Application. Eds B. W. Ritchie, G. J. Harrison, L. R. Harrison. Lake Worth, Florida, Wingers Publishing. p 556

Effect of forage supplements on the incidence of bloat in dairy cows grazing high clover pastures C. J. C. Phillips, N. L. James, J. P. Murray-Evans Veterinary Record (1996) 139, 162-165

The effect of offering forage supplements of different compositions was examined in two experiments with cows grazing high clover swards. In the first experiment strawmix supplements of high or low energy content (11 and 9 MJ metabolisable energy/kg dry matter [DM]) and high or low crude protein content (17 and 4 g/kg DM) were offered for periods of three weeks. The energy and protein contents were varied by the content of molasses and soyabean meal, respectively. The high energy, high protein supplement increased the incidence of bloat, and the low energy, high protein supplement reduced it, compared with grazing alone. Bloat was most evident in the first two weeks of each feeding period, suggesting that the cows partially adapted to the diets within three weeks. In the second experiment silage supplements reduced the incidence

C. J. C. Phillips, BSc, PhD, Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge CB3 OES N. L. James BSc, PhD, J. P. Murray-Evans, BSc, PhD, School of Agricultural and Forest Sciences, University of Wales, Bangor, Gwynedd LL57 2UW

of bloat among cows grazing both tall and short swards. The most suitable forages to feed when there is a risk of bloat are those that are slowly fermented in the rumen but are eaten in sufficient quantity to reduce periods of rapid herbage intake.

AN excess of white clover in the pasture causes frothy bloat in cattle, owing largely to the rapid rate at which the clover's mesophyll cells are ruptured during mastication, and the more rapid release of cell solutes for bacterial fermentation than from plants with thicker cuticles (Reid and others 1962, Cheng and others 1980). Bloat can be alleviated by supplying forage supplements which slow down the rate of rumen fermentation. A strawmix could provide the same benefit, but not if it contains concentrated energy and protein sources that are degraded rapidly in the rumen. This paper describes two experiments on ruminal tympany in dairy cows grazing high clover swards, and the effects of supplementing them with forage and a strawmix. Materials and methods

Experiment I Twenty February-calving British Friesian dairy cows

were

allo-


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The Veterinary Record, August 17, 1996

TABLE 1: Composition of high (E) and low (e) energy and high (P) and low (p) protein strawmix supplements in experiment 1

cated according to milk yield to four blocks of a balanced changeover design (Davies and Hall 1969) with five three-week periods from April 27 to August 10. Within each block the cows were allocated at random to receive one of five treatments: no supplement (treatment N) or pasture supplements of high or low energy (treatments E and e) and high or low protein (treatments P or p) in a factorial design. The cows were grazed on 4-6 ha of a perennial ryegrass and white clover pasture sown the previous year. The area was divided into five equal paddocks and the five treatments rotated around the paddocks daily. One application of 63 kg nitrogen/ha was applied to the entire area on June 4. The supplements were formulated from straw chopped to approximately 3 cm, sugar cane molasses, soyabean meal and water as shown in Table 1. They were fed ad libitum twice daily for 30 minutes after each milking in individual feeding boxes (American Calan). Refusals were weighed daily and the intakes are presented for the final week of each period. In addition, before feeding the supplement, all the cows were given a concentrate mix containing 1 kg rolled barley, 200 g of calcined magnesite (to protect them from hypomagnesaemia) and 50 ml of vegetable oil. After consuming this supplement the cows in treatment N were returned to pasture. The cows were assessed daily for the incidence of bloat (swelling of the left sublumbar fossa) at 13.00 and 21.00. When bloat was detected the cow was first walked to the handling race over a distance of 500 m. If the swelling had not subsided the cow was treated with 100 ml dimethicone (Birp; Arnolds Veterinary Products) and returned to the field after 30 minutes observation, provided that the swelling had subsided. On one occasion it did not and, following an unsuccessful attempt to relieve the bloat with a 'stomach tube', ruminal cannulation was required. One cow died of bloat at night and its missing milk production data were estimated by using the procedure of Steel and Torrie (1960) for a Latin square design. Sward height was recorded twice weekly from 18 measurements/ha with a rising plate meter (Milk Marketing Board 1976) in a W pattern across each paddock. Sward composition was determined once in each period by cutting 12 quadrats of 0-1 m2 to ground level with electric sheep shears. The position of the quadrats was determined by using a ranked sampling method with four quadrats ranked for clover content for each quadrat cut (t'Mannetje and Haydock 1963). Cut samples were separated into grass, clover and weeds, and the grass and clover fractions analysed for dry matter (DM), crude protein (cp) and ash by the procedures of the Association of Official Analytical Chemists (1984). At each milking in the last four days of each period, milk yield was recorded and separate samples of milk were taken for fat and protein analysis by the Gerber and Kjeldahl techniques (Ministry of Agriculture, Fisheries and Food 1986), respectively. The incidence of bloat was analysed for differences between treatments, periods and week within period by the X2 test. Intake and production data were examined for the statistical significance of treatment differences by analysis of variance, with treatment, period and block as factors, using the statistical package Genstat (Lawes Agricultural Trust 1985).

Straw (%) ep Ep eP EP

50 25 50 25

Molasses

Soya

Water

(N)

(%)

(g/kg DM)

50 75 25

0 0 25 27 5

188 63 250 63

47.5

Crude protein content

ME content*

(g/kg DM) (MJ/kg DM) 42 43 167 169

89 10.9 8.8 10 7

ME Metabolisable energy, DM Dry matter * Predicted from MAFF (1 975)

by varying the area of herbage available to the cows. The second factor was silage provision, which was either a first or third cut from a predominantly perennial ryegrass sward. The first and third cut contained, respectively, 178 and 161 g DM/kg freshweight, 113 and 215 g cP/kg DM, 345 and 285 g modified acid detergent fibre/kg DM, predicted ME contents of 10-6 and 11 3 MJ/kg DM, had a pH of 3-8 and 4-2, and contained 72 and 119 g ammonia nitrogen/kg total nitrogen. The silages were offered for one hour after morning and afternoon milking. Cow behaviour was observed for 24 hours per period. All other methods were as for experiment 1. cm

Results Experiment I

The mean pasture height was 4-8 cm and its botanical composition was 73 per cent white clover, 25 per cent grass and 2 per cent weeds. The clover contents of the sward in periods 1 to 5 were 73, 77, 74, 72 and 69 per cent, respectively. The intake of strawmix DM was greatest when both the energy and protein content of the mix was increased (treatment EP) (Table 2). Milk yield was similar for all treatments, although it tended to be slightly increased by treatment EP. Milk fat content was not affected by treatment, but milk protein content was increased for the high energy supplements, especially treatment EP. The total incidence of bloat was increased for the cows receiving the EP supplement and was least for cows receiving the eP supplement, with intermediate levels in the N, ep and Ep treatments (P0.25 0.03


164 Ilh

The Veterinary Record, August 17, 1996 25 ,

.

14 1 Cl)

Z1

20 Cl) w

< 10-

Cl)-

0

8-

C

6-

C.) 0

z

Er w

co

42O

0

10

z

N

ep

Ep

eP

_

S

Fatality

-

0

-

EP

TREATMENTS

Treated

5

Not

1

2

treoted

3

PERIODS

FIG 1: Incidence of bloat in the cows in experiment 1

FIG 2: Change in the incidence of bloat experiment 1

viding silage (Table 4). There was no difference between the first and third cuts of silage. Silage increased ruminating time when it was fed to cows grazing the short herbage and reduced the incidence of bloat on both the long and short swards. Herbage height had no effect on the incidence of bloat.

EP gy

Discussion

Experiment 1 demonstrated a synergistic effect between the energy and protein concentrations of the supplement on the intake of strawmix DM and the output of milk protein. Cows in treatment EP ate 16 MJ/day more than cows in treatment ep, and produced 7.3 MJ more milk energy/day (Ministry of Agriculture, Fisheries and Food 1975). The energy and protein synergism could have been related to the rapid release of energy in the form of soluble carbohydrates in the molasses. Molasses requires a nitrogen complement to enable the rumen microbes to utilise the energy released. It has previously been suggested that molasses supplements fed with a silage-based diet should include a protein complement (Thomas 1989), but little benefit has been observed in practice (Hecheimi and others 1989). The major effect of the nutrient synergism in this experiment was to enhance the intake of the strawmix supplement. Bloat was expected in this experiment because of the high clover content. The increase in the incidence of bloat in treatment

Treated Untreated Total

Week within period 2

3

6 13 19

11 11 22

3 6 6

over

the

five

periods in

is further evidence of the synergism between protein and enerin stimulating ruminal bacterial fermentation. The reduced inci-

dence of bloat in treatment eP was probably due to the low ratio of molasses to straw in this supplement (Table 1). If the clover content of a mixed sward is sufficient for bloat to be a risk, then a strawmix supplement could be effective as long as its content of rapidly fermentable carbohydrates is low. Nevertheless, some molasses is required to bind the solid concentrate ingredients to the straw. It is unlikely that such a high frequency of bloat as was experienced in this experiment would be observed in practice, because there was evidence of adaptation to the diet after two weeks. However, the unpredictability of bloat was emphasised by the one fatality, which occurred during dry weather when bloat was unexpected. High intakes can suddenly occur after oestrus, or after cows have been 'off their feed' owing to ill health. The reduction in the incidence of bloat after period 2 was probably related to the stage of clover growth, the reduced clover content of the sward and the dry conditions at the end of the experiment. The absence of any relationship between milk yield and the incidence of bloat was probably because high yielding cows do not necessarily have a greater intake of herbage DM than low

yielding cows (Phillips 1989). As expected the incidence of bloat was less in experiment 2 than experiment 1 because the sward contained less clover. In experiment 2 there was no evidence of a reduction in bloat in the cows grazing the tall sward which contained less clover. However, the rate of herbage intake would have been less on the short sward, thereby reducing the rate of digestion. Both sward height and fibre content therefore need to be taken into account when considering the risk of bloat on a high clover sward. The reduction in bloat with the provision of silage coincided with an increase in the milk yield of the silage-fed cows on the short swards. It is therefore unlikely that the effect was due to the reduction in the extent of rumen fermentation when silage was offered. Bloat may have been caused by temporary periods of

TABLE 3: Changes in the frequency of bloat during each period in experiment 1 1

5

4

P 0 25