and proglottid morphology according to Beveridge and Gregofy (1976).

Despite the small number of foxes examined in this study, 9 of 19 (47%) had E. granulosus infections. Seven of 17 foxes collected in the Bondo State Forest and both foxes from the Morton National Park contained hydatid worms. Recovered worm burdens ranged from 1 to 280 with an average of 90 worms per fox (n=8). The infections were patent in many foxes with several worms having gravid proglottids. Other intestinal parasites recorded were Wncinaria stenocephala (53%), Toxocara canis (260/0), Toxascaris leonina (lo%), Spi- rometra erinacei (lo%), Taenia serialis (26%) and T. pisifor- mi3 (21%). In comparison, all 13 dogs trapped during the same time period in the Bondo State Forest were infected with E. granulosus with worm burdens ranging from 325 to 302,000 (average 44,700 n = 13) (Gasser et a1 1988). Also, a preliminary study in 1986 of wild dogs in or about the Morton National Park demonstrated eight of eleven wild dogs were infected with E. granulosus (Morrison ef a1 1988).

Where possible, hydatid worms from each fox were ex- amined microscopically to determine strain type, based on rostellar hook number, arrangement and morphology (Kumaratilake and Thompson 1984a). Worms from 4 foxes collected in the Bondo State Forest were classified as sylvatic strain. Worms from another fox at this location had rostellar hook characteristics which were shared by both domestic and sylvatic strains and consequently could not be classified. Hy- datid worms from the remaining 4 foxes could not be classified because they were devoid of rostellar hooks. In comparison, hydatid worms from wild dogs trapped in the Bondo State Forest were predominantly sylvatic strain, however, in two dogs mixed infections of both sylvatic and domestic strains of E. granulosus were present. (RCA Thompson unpublished data).

The explanation of this high prevalence of hydatid infection in foxes currently remains speculative. Foxes may have ac- quired infection through direct predation or scavenging of mammals which act as intermediate hosts of E. granulosus. Dietary and parasite surveys of foxes have shown that fresh sheep material is an infrequent food item, and consequently, access to viable metacestode stages of E. granulosus, Taenia ovis and T. hydatigena from sheep is highly restricted (Mc- Intosh 1963; Coman 1973b; Coman and Ryan 1974; Ryan and Croft 1974). Domestic strain hydatid worms were found in a fox from the Gundaroo area of south-eastern New South Wales and these were thought to have been acquired by scavenging dead ewes from a nearby farm (Thompson et a1 1985). The present study demonstrates that foxes may be readily infected with the sylvatic strain of hydatid in forest or bushland habitats. The sylvatic strain is normally main- tained through a predator-prey interaction involving dingoes or wild dogs as definitive hosts and macropodid marsupials as intermediate hosts (Herd and Coman 1975; Thompson and Kumaratilake 1982; Kumaratikale and Thompson 1982, 1974a, b). Several studies of stomach contents of foxes have recorded the presence of macropodid remains (Coman 1973b; Ryan and Croft 1974; Croft and Hone 1978). These studies conclude that the majority of this macropodid material is most probably consumed as carrion in the form of road-killed animals or scavenging the carcases left by kangaroo shooters. Despite this information, there is some evidence that foxes are capable of occasionally capturing and killing macropods (Hornsby 1982). In contrast, wild dogs and dingoes are known to be efficient predators of macropods (Newsome et a1 1983). It is conceivable that the foxes examined in this study acquired hydatid infection through scavenging the carcases of macro- pods which had been killed by dingoes or wild dogs. The smaller average number of hydatid worms in foxes compared with those from wild dogs from the Bondo State Forest location may be due to a reduction in the proportion of worms which establish successfully in foxes (Thompson 1983). Al- ternatively, it could be related to the consumption of fewer viable protoscolesces resulting from scavenging carcases which have been initially killed and fed on by wild dogs.

I24

Macropods do not represent the only likely sourcL infection at these locations. Feral pigs may also be imb since they are known to occur at these New South Wh. , locations and can harbour viable hydatid cysts. Currently there is no evidence to suspect the rabbit as an intermediate host for hydatid infection, the high prevalence of T. pisiformis and T. serialis in the foxes merely being a reflection of the im- portance of rabbits in their diet.

The authors wish to thank B Lantry, D Wise and A Elliot for their laboratory assistance; R Hobbs for assistance with the morphological characterisation of isolates and the co- operation of B Morris and C Crocker in the collection of the foxes. The financial support to Dr Thompson of the Australia Research Grants Scheme is gratefully acknowledged.

References Beveridge I and Gregory GG (1976) - Aust Ver J 52: 369 Coman BJ (1973a) - Aust Vet J 49: 378 Coman BJ (1973b) - Aust J Zoo1 21: 391 Coman BJ and Ryan G (1974) - Aust Vet J 50: 577 Croft JD and Hone LJ (1978) - Aust Wildl Res 5: 85 Dent CHR and Kelly JD (1974) - Aust Vet J 50: 176 Gasser RB, Lightowlers ME, Obendorf DL, Jenkins DJ and Rickard

MD (1988) - Aust Vet J 65: in press Gemmell MA (1959) - Aust Vet J 35: 450 Hornsby PE (1982) - Aust Mammal 5: 225 Herd RP and Coman BJ (1975) - Aust Vet J 51: 591 Howkins AB (1986) - Proc AIST/ANZAAS Conference 'Technology

Kumaratilake LM and Thompson RCA (1982) - Helminthol Abstr

Kumaratilake LM and Thompson RCA (1984a) - Int J Parasit 14:

Kumaratilake LM and Thompson RCA (1984b) - Int J Parasit 14:

Morrison P, Stanton R and Pilatti E (1988) - Aust Vet J (1988) 65:

McIntosh DL (19631 - CSIRO Wild Res 8: 1

today and tomorrow' Sydney p 152

(Ser A) 51: 233

467

581

97

Newsome AE,'Corbett LK, Catling PC and Burt RJ (1983) - Ausr

Pullar EM (1946) - Aust Vet J 22: 12 Wildl Res 10: 477

Ryan GE (1976) .- Aust Vet J 52: 126 Ryan GE and Croft JD (1974) - Aust Wildl Res 1: 89 Thompson RCA (1983) - Ann Trop Med Parasit 77: 75 Thompson RCA and Kumaratilake LM (1982) - Trans R SOC trop

Thompson RCA, Nicholas WL, Howell MJ and Kumaratilake LM

(Accepted for publication 19 August 1988)

med Hyg 16: 13

(1985) - Ausl Vet J 62: 200

Effect of supplementary feeding and zeranol on puberty in feral Cashmere goats

School of Agriculture and Forestry, T WOLDE-MICHAEL University of Melbourne, Parkville, HM MILLER Victoria 3052 JHG HOLMES

Animal Research Institute, BA McGREGOR Department of Agriculture and Rural Affairs, Werribee, Victoria 3030 Veterinary Clinical Centre, DB GALLOWAY University of Melbourne, Werribee 3030

The natural breeding season of goats in Victoria peaks in March and April, with kidding in spring and weaning at the beginning of summer onto mature pasture. When green pas- ture is not available after weaning, kids typically maintain or lose weight (McGregor 1984) and in April may weigh no more than at weaning. Well-grown doe kids sometimes mate and conceive in autumn, kidding at 12 months of age, but the essential criteria for attainment of puberty (age, weight, growth rate) are undefined in this genotype. Feeding of concentrates may induce more kids to attain puberty in autumn, permitting earlier breeding and shortening the generation interval. Use

Australian Veterinary Journal, Vol. 66, No. 4, April, 1989

of the non-steroid anabolic zeranol* also increases growth rate, in Angora wethers by 55% (McCregor er a/ 1984) and in Spanish Grenadine wethers by 32Y0, in bucks by 55% (Silva and Berenguer 1984). But in other species, zeranol has caused significant retardation of sexual development, delaying pu- berty in ewe lanibs (Cooper 1981), reducing pregnancy rates in heifers (Staigmiller et u/ 1983) and reducing testicular de- velopment after prepubertal implantation, in lambs at 44 d (Riesen er (I/ 1977) and in calves at 160 d (Riquelme and Campo 1983). No effects on sexual development of goats appear to have been reported.

We defined attainment of puberty by does as the day of first oestrus. Definition of puberty in males cannot be as precise. Electro-ejaculation of young bucks to determine the onset of spermato-genesis was considered likely to yield un- reliable results. In mature, sexually active bucks, spermatids are found in 80% of seminiferous tubules while 2OYo are quiescent. Kids with sperm or spermatids in 70% of tubules were considered to have reached puberty. We examined the effect of age, weight and zeranol treatment on attainment of puberty using 114 kids from the University of Melbourne llock of re-domesticated feral goats being selected for cash- mere at Mt Derrimut (20 km west of Melbourne), during 14 weeks from weaning (6 January 1984 to 14 April 1984). Mid- April is after the peak of the natural breeding season so that oestrus would have been displayed by does reaching puberty. Pasture growth usually begins about this time, rendering fur- ther supplementation superfluous. Kids with known birth dates from dams of known weight were weaned at about 125 days of age. We studied an initial slaughter group of 9 females and 10 males, culled at weaning, and 3 management strategies:

(1) Crazing on mature pasture without supplementation: 55 doe kids retained for breeding were grazed on senescent rye grass and barley grass of low quality, typical of the pasture available at this season.

(2) Supplementation of roughage: 9 female and 11 male kids maintained in separate bare yards, were fed daily 400g per head of grain (77.5% barley, 20% lupins, 2.5% limestone) and average-quality grass hay ud lib, and slaughtered on 17 April 1984.

(3) Supplementation of roughage, plus zeranol: 9 females and 11 males, implanted with 12mg zeranol, were treated as in (2).

Oestrus was detected by the use of vasectomised mature bucks, fitted with harnesses and cold-weather crayons and run with each doe group. Kids were weighed and scrotal circum- ference measured fortnightly. At slaughter, ovarian follicles (>2mm) and ovulations were counted. In males, an epi- didymal smear was prepared. Testicular weight and volume were measured and a section of testis stained with haematox- ylin and eosin was examined histologically. The proportion of tubules containing spermatids or sperm was measured. Growth data were analysed by ANOVA and reproduction data by regression.

During the trial, 3 kids died through misadventure. Initially, males weighed 14.3kg ( ? 1 .O) and females 12.5kg (+_ 1 .O). Crazing does grew less than half as fast as fed does (p<O.001, Table I ) . Supplemented males grew faster than females (p<O.OOI); zeranol increased these rates by about 25%. There was steady growth from February to April in the supplemented kids, indicating that the seasonally poor growth of weaners in autumn can be overcome by purely nutritional means and is not a seasonal effect on the kids' appetite per se.

Does slaughtered in January had up to 8 small (>2mm) follicles per ovary, suggesting some development at this stage. Grazing and supplemented does without zeranol showed first oestrus at the same mean weights, about 15kg, but at different ages (Table 1). There was a large range in weights (10 to 2Okg) and ages (140 to 258 d) over which does reached puberty. They showed oestrus at the expected 3-week intervals and had

Ralgro, Wellcorne Australia Ltd, 600 Nicholson St, Fitzroy North, Victoria 3065

Auslruliun C'erermory Journul. Vol. 66, No. 4, April, 1989

TABLE 1 Effect of diet and zeranol on the growth rate of bucks and does and the age, weight and date of first oestrus in does

Item Grain Grain Grazing S E M plus ze ran0 I

Mean growth, glday

Mean growth, glday

No. in oestrus 618 418 30153 No. in oestrus twice 618 018 Age (days) at first oestrus 172 143 202 5 Weight (kg) at first oes-

t r u s 15.2 13.0 15.4 0.4 Mean date 28 Feb. 25 Jan. 27 March 5 days Weight at 14th week: Oestral does (kg) 18.8 19.6 17.0 0.32 Non-oestral (ka) 14.8 17.3 14.2 0.32

(bucks) 82 100 -

(does) 50 63 15 4.9

'Many of these does showed first oestrus so late that the experiment terminated before a second oestrus could occur.

corpora lutea and follicles >3mm at slaughter. Does which did not show oestrus were lighter throughout. Later born does tended to be younger and lighter at puberty, concentrating its onset around the end of March in grazing does. Of 8 does receiving zeranol, 4 showed oestrus within 2 weeks of treat- ment. They were of similar age and weight to the most pre- cocious in other groups. Neither they nor the other zeranol- treated does came in heat after this, although 2 had corpora lutea at slaughter. These observations d o not indicate stimu- lation of puberty by zeranol. The zeranol group averaged 18.4kg at slaughter, 20% above the weight a t which untreated does showed oestrus. Overall, first oestrus occurred when the does (n =40) had attained 39+. 1.4% of dam's weight at mat- ing.

For both scrotal circumference and testicular weight at slaughter, the correlation (r') with weight was 0.81 (p<O.Ol) but with age was only 0.50 (n s). Scrota1 circumference in- creased 0.62 + O.llcm/kg weight gain over the range 8 to 33 kg but was more closely related (r' = 0.86, p<O.OI) to buck weight as a proportion of dam weight than to buck weight per se. The proportion of active seminiferous tubules and presence of sperm in the epidydimis were not strongly related to weight or age (r' = 0.55.11 s). All but one kid had sperm or spermatids in over 70% of tubules when they weighed over 40% of dams' mature mating weights (about 15.5kg). Even in January, mature sperm were found in the epidydimis of 7 of 10 bucks. We did not determine if 15kg bucks could mate successfully, but at 22kg they were sexually active. Zeranol did not affect testis weight. Testis weight and volume could be predicted from scrotal circumference since r' = 0.96 (p <0.001).

Initiation of puberty occurred at the lower end of the range of 40% to 70% of mature weight reported by Doney et al (1982). Grain feeding increased weight by 4kg above grazing, which could be critical in lifting some weaners above the weight threshold for puberty. An appropriate strategy may be to divide weaner does into 3 groups: those which would reach mating weight without supplements, those which would require supplements and those which would not reach this threshold even with grain feeding. Supplementing only the second group would increase the number of does capable of breeding at 7 months. Further study is needed of the effect of early (l-year- old) kidding on lifetime performance and of the interactions with nutrition. Similarly it may be profitable to feed buck kids to obtain earlier mating. However, the range of age and weight at puberty makes the identification of these 3 groups inaccurate.

The effect of zeranol on female reproduction obviously precludes its use on breeding does, as in other species. Al- though we found no deleterious effect on bucks, which were approaching puberty when implanted, in view of such a small response in growth (2kg in 100 days) and the evidence of

I25

effects on males of other species, there is no justification for its use.

This study found that spring-born “cashmere” kids weaned in summer can reach puberty in autumn at 40% of dam’s weight (about 15kg). It is not known if kids born at other seasons will reach puberty at this weight. Improving the nu- trition of light weight weaners will increase the number reach- ing puberty and available for mating and shorten generation interval. To avoid accidental matings, weaned bucks should be separated from all females. Scrota1 circumference is a reliable index of testis weight. The use of zeranol is contra- indicated in stimulating puberty.

Zeranol was generously provided by Wellcome Australia. T Wolde-Michael was supported by the Australian Develop- ment Assistance Bureau, which also provided funds for the project.

References Cooper RA (1981) - Er Vet J 137: 513 Doney JM, Gunn RG and Horak F (1982) - in “Sheep and G o a ~

Production”, in “World Animal Science” series, Elsevier, Amsterdam, Vol C1, p 60 McGregor BA (1984) Proc Ausi Soc Anim Prod 15: 715

McGregor BA, Mientges D, A d a m M and Wellington J K M (1984) Aust Vet J 61: 327

Reisen JW, Beeler BJ, Abnes FB and Woody CO (1977) - J Anim Sci 45: 293

Riquelme RA and Campo CDH (1983) - Arch Med Vei Chile 15: 80

Silva M and Berenguer F (1984) - Anim Prod 38: 546 Staigmiller RB, Bellow RA and Short RE (1983) - J Anim Sci 57:

527

(Accepted for publication I 1 November 1988)

CORRESPONDENCE

Digging behaviour in domestic dogs

Division of Veterinary Biology, School of Veterinary Studies Murdoch University, Western Australia 6150

GJ ADAMS J GRANDAGE

Digging holes in the garden is an irritating activity of pet dogs. An American survey showed that digging consistently ranks within the 10 most common behavioural problems (Campbell 1986). This article reports a survey of dog owners in the Perth neighbourhood to see if any consistent patterns of digging behaviour could be identified. The survey was part of an “independent study contract” by one of us (GJA) and contributed a small part towards an undergraduate program in biology.

Owners were identified by approaching and talking to people in public parks, shopping centres, in urban streets, and at various places of work in and around Perth. Interviews were structured around 25 questions, the answers from which es- tablished the physical characteristics of the dog and its en- vironment. The final survey was based on 100 fully completed questionnaires.

Eighty three per cent of dog owners said their dogs dug and 73% of these dug close to the house. Large dogs dug significantly more than miniature dogs (P < 0.01; 24 of 25 large dogs, versus 7 of 13 miniature dogs). Despite some evidence that young, male, short-haired, dogs were more prone to digging than their older, female, long-haired counterparts, these tendencies were not statistically significant. Similarly there was no statistical correlation between digging behaviour and exercise area, exercise frequency, feeding time or whether a family member was with the dog during the day. Owners who claimed they had active dogs reported more digging behaviour than those who had sedentary ones. The majority of dogs dug all year round although digging activity was reported to be higher in summer than winter and higher in the daytime than at night. Dogs left outside for long periods unattended were, understandably, more likely to dig than those kept inside except for walks. Those restricted to small gardens dug more than fothers in less confined areas but this was not statistically significant.

The holes dug by dogs were reported to be of irregular form but were mostly single, saucer-shaped depressions under half a metre in diameter with about one shoeboxful (about 5

litres) of earth scattered peripherally. Dogs often favoured particular sites which were then subject to repeated excava- tions. Major excavations were occasionally reported where deep pits equalled the dog’s size.

Only speculative evidence was found in the scant literature to suggest why domestic dogs dig. No authors were found who commented on its relation to the fossorial activity of wild canids several of whom dig subterraneans lairs. Bochelt (1984) claimed that puppies may dig as a response to separation from their owners, or, as frightened adults, as an escape response. Beaver (1987) suggested they dig to reach a neigh- bour’s animal behind a fence, or to seek relief from the summer heat. Campbell (1975) suggested that some dogs dig by example, as an allelomimetic activity. They were all simply suggestions.

Similar views were also frequently registered in the present survey, although there were few reports of dogs digging close to fences. Owners were asked why they thought their dogs dug holes. The answers were: ‘to keep cool’ (21 out of 83); ‘out of boredom and frustration’ (19); ‘playing’ (10); ‘to bury bones’ (8); ‘out of spite and revenge’ ( 5 ) ; ‘to follow the scent of prey’ (4); ‘because we have been digging’ (3); ‘because the dog’s stupid’ (2); ‘to escape’ (1); ‘to sleep in’ (1); ‘no idea’ (9).

Asked how they tried to stop their dog from digging evoked the following responses: ‘put mouse-traps in the hole’; ‘put dog faeces in the hole’; ‘hold the dog’s head in the hole’; ‘smack the dog’, ‘scold the dog’; ‘hose the dog’; ‘cover the holes with wire mesh’; ‘put the dog in the rubbish bin’; ‘put the dog in the hole and fill it in’; ‘put pepper on the dog’s nose’; ‘deprive it of bones’; ‘brick up the hole’; ‘rope off the area’; ‘give the dog a good talking to’; ‘tell her she’s a naughty dog’; ‘I just cried’.

The survey confirms that digging is part of the normal behaviour of pet dogs. The causes remain unknown although the variety of circumstances under which digging occurs and the large number of plausible suggestions implies that the motivation is multifactorial. No reliable means of prevention was revealed by the survey. Nevertheless it is still tempting to suggest that a dog’s digging behaviour may be modified by increased contact with the owner.

References Beaver BV (1987) - Southwest vet 38: 35 Borchelt PL (1984) - In Nutrition and Behaviour in Dogs and Cats,

edited by RS Anderson, Pergamon Press, Oxford pp 170, 193 Campbell WE (1975) - Eehaviour Problems in Dogs, Amer Vet Publ,

Santa Barbara, California, p 238 Campbell WE (1986) - Mod Vet Pruc 67: 28

(Accepted for publication 25 November 1988)

126 Australian Veterinary Journal, Vol. 64 No, 4, April, 1989