Bovine infectious keratoconjunctivitis in different cattle breeds.

Abstract

150 Proc. Aust. Soc. Anim. Prod. Vol. 17 BOVINE INFECTIOUS KERATOCONJUNCTIVITIS IN DIFFERENT CATTLE BREEDS B.M. BURNS*, C.J. HOWITT+ and C.R. ESDALE** SUMMARY The incidence and persistence of bovine infectious keratoconjunctivitis, or ' pink-eye' , was investigated over three drafts in Hereford, Simmental and Africander-Hereford heifers. Incidence of infection was greatest in Herefords (43.1%), intermediate in Simmentals (21.4%) and least in Africander-Herefords (7.2%). Persistence of infection was related to breed, with Herefords retaining more signs of infection than Simmentals or Africander-Herefords. Infected animals had lower average daily weight gains (479 g/d) than uninfected animals (516 g/d). No relationship was found between eyelid pigmentation, the incidence or persistence of infection and average daily weight gain. The higher average daily weight gains and lower incidence and persistence of bovine infectious keratoconjunctivitis in Africander-Herefords suggest that tropically adapted breeds are more viable commercially in sub-tropical and tropical environments. Key words: change. Bovine infectious keratoconjunctivitis, cattle breeds, weight INTRODUCTION Bovine infectious keratoconjunctivitis (BIK), commonly known as ' pink-eye' , is probably the only serious infectious disease of cattle common in all cattle producing areas of Australia. It is a disease affecting the eyes of cattle and is characterised by an acute to chronic inflammation of the cornea and surrounding tissue. Gallagher (1954) found ` that the intense discomfort, pain ' and temporary or permanent blindness associated with BIK reduced grazing time to a point where growing, breeding and fattening were affected. BI.K is an economically important disease because of these production losses (Thrift and Overfield 1974). The disease is seasonal in occurrence, with a high incidence in young stock during summer (Spradbrow 1967). Possible factors associated with hot conditions which predispose animals to infection are dust, sunlight and flies (Wilcox 1968) . .Degree of eyelid pigmentation has also been related to the incidence of BIK, eyel-ids with complete pigmentation being less affected (Frisch 1975)` . This paw- repor t s on t.he inci dence and pers ist e nce of Bl,K, its ef feet on I i veweigh t gain , and t he re lati onsh ip between eye I id pigmentat' ion and B IK. MATERIALS AND METHODS Location and experimental animals The experimental animals were three-quarter and higher Hereford (H) with the residual being Shorthorn, three-quarter and higher Simmental (S) with the residual being Hereford, and F2 et seq. Africander-Hereford (AH) cattle reared at Brigalow Research Stati on, Theodore. The ncidence and persis tence o f BIK in weaner heifers from t hree calf crops was observed from 1984 to 1986. Location, pastures and herd management have been described by ' Rudder et al. (1986). t ' Swan' Lagoon' Beef Cattle Research Station, Millaroo, 4807 s + Qld. Dept. Primary Industries, G.P.O. Box 46, Brisbane, 4001 ** Qld. Dept . Primary lndustr ies, G.P.O. Box 485, Biloela, 4715 Proc. Amt. Soc. Anim. prod. Vol. 17 Experimental procedure 151 Heifers were examined for BIK at monthly intervals, with each eye being allocated a score of 1 to 6 using the following scale: 1 = no blight, 2 = acut e blight, 3 = yellow cornea, 4 = pointed cornea, 5 = eyeball rupture, 6 = chronic white cornea. Live weights of heifers were also recorded monthly. A subset of these animals, selected at random across breeds from 1984 and 1985 to be replacement breeders, was also weighed at 30 months of age. Pigmentation of each eye, based on the percentage of the eyelid pigmented, was recorded at birth. The period from October to April, when heifers were 12-18 months of age and corresponding to the period of peak predisposing factors to infection (Wilcox 19681, was chosen to investigate both the incidence and persistence of BIK. No cattle were examined in November. A binary variable was redefined from the six original eye scores where 1 = infected (eye score of 2-6) in at least one eye and 0 = not infected (eye score of 1) in both eyes. One incidence and three persistence variables were defined as infected at least once, twice, three times For pigmentation an average and four times of the six chosen observations. percentage pigmentation was obtained for each animal and classed as follows: O-12.5%, 12.5-87.59/o and 87.5-100% pigmentation . The low levels of incidence and persistence and high levels of full eyelid pigmentation in the AH precluded analysis of this breed. Average daily weight gain was calculated from October to April . These variables were analysed using standard analyses of variance for unequal subclass numbers. Factors investigated were breed, year and breed x year interaction . For average daily weight gain, disease incidence or persistence was included as a main effect. For relationships between pigmentation and BIK, pigmentation was included as a main effect. All other interactions were found to be nonsignificant (PpO.05). RESULTS AND DISCUSSION The average percentage incidence and persistence of BIK for H and S are shown in Table 1. The corresponding figures for AH are 7.2%, 4.4%, 1.2% and O.O%., Whilst incidence and persistence of BIK were high in H and S, there was little or none in AH. The low levels in AH correspond with 90% of these animals having 100% eyelid pigmentation. Similarly , in other studies the incidence and persistence of BIK was reported to be higher in Bos taurus breeds compared to Bos indicus breeds and their crosses (Jackson 1953; Frisch 1975; Dodt 1977). Table 1 Leas tsqu a re means of percentage incidence and persistence of B K ove r six ,observat ions for breed. an d year 152 Proc. Aust. Soc. Anim. Prod. VoZ. 17 There was a significant difference (PxO.01) between H and S breeds for incidence and persistence of BIK (Table 1). Levels of incidence and levels of persistence for animals infected at least twice and three times were twice as high in H as in S, and three times as high for animals infected at least four times. Similarly , the percentage of animals infected only once, twice or three times in the six observations was higher in the H (13.3, 11.4 and 5.2%) than the S (8.0, 4.6 and 4.9%) and the AH (2.8, 3.2 and 1.29/o), respectively. There was no significant difference (PsO.05) in incidence or persistence between years; however for animalsinfected at least four times there was a significant (P~0.05) breed b y year interaction . While percentage persistence remained relatively low and stable The rate of for S it rose from 5.1 to 12.2 to 22.4% across the three years for H. infection has been reported to be higher inthe Hereford breed than in other Bos taurus breeds (Jackson 1953). There was no significant difference (PsO.05) between H and S breeds for average daily weight gain after adjusting for years and incidence or persistence of infection . However, AH had a significantly greater (P~0.01) average daily weig,ht gain (605 + 104.1 g/d, mean + SD, n=249) than both H and S (498 and 510 g/d, respectively). There was a general trend in both H and S for average daily weight gain to decrease as persistence of infection increased. The difference in average daily weight gains between years contributed to a significant (P~0.01) breed by year interaction for all levels of incidence and persistence. This interaction was due to the low performance of S, relative to the performance of H, during periods of nutritional stress as experienced in 1985. Large European breeds have the capacity for hiqh growth potential in temperate environments . (Mason 1971). The degree to which these breeds can express this high growth potential In sub-tropical and tropical environments will depend on the severity o f environmental constraints. Table 2 Least squar e means o f ave age da ly weigh t gain (g/d) fo r incidence a,nd pers is t ence o f BIK over six observations 111.8 110.8 111.1 ' 111.5 Means in columns followed,by ,dlfferent letters dlffer significantly (P<O.Ol). Those animals that were Infected had a sjgnlflcantly lower (P<O.Ol) average dally.welght galn than those thatwere uninfected for all levels of disease incidence and persistence (Table 2). Generally the infected animals had a l,O% reduction In average dally weight gain compared with the uninfected animals, which is In agreement with the observations of Thrift and Overfleid (1974) and Frlsch (1975): The subset of animals weighed at 30 months of age' showed that those, heifers originally classed as Infected at least once had significantly lower * (,P<O.O5) I I ve weights (417,~ 38.1 kg, n=39).than those that were uninfected (432 kg, n=88). The reduction In livewelght performance and lower subsequent live weights of previously Infected animals In our study agrees with Thrift and. Proc. Aust. Soc. Anim. Prod. VoZ. 17 153 Overfield (1974) who found that Hereford bulls with no BIK during the preweaning period had significantly greater (PxO.05) post weaning average daily weight gains and live weights than those bulls that were infected. . There were no differences in the incidence or persistence of BIK with level of eyelid pigmentation, these results agreeing with those of Jackson (1953). By contrast , Frisch (1975) found that the proportion of animals with BIK decreased as In our experiment, the level of the level of eyelid pigmentation increased. eyelid pigmentation had no effect on average daily weight gain in either infected or uninfected animals. Frisch (1975) reported that uninfected animals had heavier live weights than infected animals at 8 and 15 months of age for all levels of eyelid pigmentation. Frisch (1975) also reported that infected animals with full y pigmented eyelids were heavier than Infected animals with unpigmented eyelids; The differences between these two results may be caused by subtle differences in resistance to BIK between Hereford cattle used in our experiment and F3 et seq. Hereford-Shorthorn crossbreed cattle used by Frisch (1975). Jackson (1953) cited differences with Bos taurus breeds and our experiment demonstrated differences between Hereford and Simmental in the incidence and persistence of BIK. . Commercial relevance Although there were significant differences in average daily weight gain between infected and uninfected animals, the commercial relevance depends on the . incidence of infection.. Average daily weight gains (g/d) from October to April for infected and uninfected animals by breed were H, 475, 516; S, 486, 516; AH, 605, 605 respectively. Elimination of BIK would increase average daily weight It follows that to b e gain by 4, 1 and 0% in H, S and AH, respectively. commercially viable any remedial procedure to reduce or eliminate BIK must be associated with low cost inputs. One such procedure is to breed animals that already have an inherently high resistance to BIK. ACKNOWLEDGEMENTS Thanks are due to the management and staff of the Brigalow Research Station for their assistance in collecting these data and to colleagues who assisted in the preparation of this paper. REFERENCES DODT, R.M. (1977). Aust. Vet. J. 53: 128. FRISCH, J.E. (1975). Anim. Prod. 21: 265 . GALLAGHER, C.H. (1954). Aust. Vet?J. 30: 61. JACKSON, F.C. (1953). Am. J. Vet. Res.74: ' 19. MASON, 1.1. (1971). Anim. Breed. Abstr.?Q: 1. RUDDER, T.H., SEIFERT, G.W. and BURROW, HT. (1986). Proc. Aust. Soc. Anim. Prod. 16: 347. SPRADKOW, P.B. (1967). Aust. Vet. J. 43: 55 . THRIFT, F.A. and OVERFIELD, J.R. (1974): J. Anim. Sci. E: 1179. W ILCOX, G.E. (1968). Vet Bull. - 349. 38: