Animal Reproduction Science, 6 (1983/1984) 291--299 291 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

THE INFLUENCE OF ARTIFICIAL PHOTOPERIOD ON THE GROWTH, APPETITE AND REPRODUCTIVE STATUS OF MALE RED DEER AND SHEEP

A.M. SIMPSON, J.M. SUTTIE*t and R.N.B. KAY

Physiology Department, Rowett Research Institute, Bucksburn, Aberdeen AB2 9SB (Great Britain)

*To whom correspondence should be addressed.

tPresent address: Invermay Agricultural Research Centre, Private Bag, Mosgiel, New Zealand.

(Accepted 11 October 1983)

ABSTRACT

Simpson, A.M., Suttie, J.M. and Kay, R.N.B., 1984. The influence of artificial photo- period on the growth, appetite and reproductive status of male red deer and sheep. Anita. Reprod. Sci., 6: 291--299.

Young male red deer and Suffolk × (Finn x Dorset) sheep were kept on an artificial photoperiod such that two cycles of daylength occurred during one calendar year. They were penned separately, fed to appetite, weighed weekly and measured tri-weekly.

Both species showed two cycles of intake, growth and gonadal activity in response to the daylength when only one would have been shown on natural photoperiod, al- though in the sheep these cycles were of lower amplitude than in the deer. The deer grew two sets of antlers during the study. A lag of some 3--4 months occurred between an event such as peak food intake and the time it would have been expected to occur re- lative to the daylength cycle. It is considered that although daylength controls these cycles, there is an endogenous rhythm which photoperiod cannot completely suppress.

INTRODUCTION

Male sheep show profound annual cycles of food intake (Gordon, 1964; Kay and Suttie, 1980), growth and reproductive status (Marshall, 1937). These cycles are known to be under the control of the photoperiod mediated by various hormones (reviewed by Sadleir, 1969). Similarly, male deer show such cycles (Blaxter et al,, 1974); however, the control mechanisms for deer are less well known. Normally mature male deer grow one set of antlers (a mirror of reproductive potential and status) each year but under artificial lighting may grow up to three sets (Goss, 1969a). This suggests that cycles of growth and reproduction in deer likewise may be controlled by day- length. The aim of the present study was to place red deer and sheep on an

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artificial photoper iod such that two cycles of photoper iod of normal am- plitude occurred in one calendar year to determine the effects on growth, appetite and reproductive status.

MATERIALS AND METHODS

Four male red deer (Cervus elaphus) calves born in July and six Suffolk X (Finn X Dorset) ram lambs born in August were placed individually in pens and exposed to an artificial light cycle such that, although the amplitude of the change in daylength was normal for Aberdeen at 58°N, the period was reduced by half, to 6 months. The light intensity was 558 lux at 1.35 m above floor level. The stags were fed to appetite daily a diet containing barley (84%), fish meal (13%), vitamins and minerals (3%). The sheep were fed to appetite twice daily a diet based on barley straw (40%), wheat {23%) and barley (13%), with molasses, vitamins and minerals (24%). Food intake was recorded daily, and all animals were weighed weekly. At 3-weekly intervals both testes were measured with steel calipers and antlers (deer only), and hind feet, a measure of skeletal development, were measured using a flexible metal tape. Two blood samples were taken by jugular venipuncture 30---60 min apart from each animal. After centrifuging, the two plasma samples were pooled for each animal, then frozen at -22°C before being analysed for testosterone (Rowe et al., 1974). The standard used was testosterone (Sigma Chemicals, Ltd.). Inter- and intra-assay co- efficients of variation were always less than 10%.

On each occasion the deer were sedated with 20 mg xylazine/100 kg body weight (Rompun, Bayer Ltd.) to permit measuring and blood sam- pling. One of the stags (No. 74) died of a kidney infection in May of the study.

RESULTS

In response to the artificial daylength cycle the deer showed two peaks of food intake during one calendar year (Fig. 1), when only one peak would have been anticipated under natural photoperiodic conditions. These twin cycles were less evident in the sheep; in particular, the first appetite de- pression was more a levelling off than an actual trough. Peak intake tended to lag some 3 months behind peak daylength for both species, during both cycles.

Changes in body weight (Fig. 2) largely parallel those for food intake, as would be expected. Although a small weight loss was shown by the stags in April--May this was scarcely evident in the sheep. In September-- October the deer showed a pronounced weight loss whereas the sheep merely maintained weight over this period.

Hind foot length (Fig. 3) was largely unaffected by the imposed photo- period. The feet of the sheep reached their asymptotic length in July--

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August aged 1 year; there was, however, no evidence that the deer had ceased growth at the close of the study.

Testis size, an index of gonadal development, showed two clear peaks of activity in both species in May--June and again in September--October (Fig. 4). The cycle of development and regression was more marked in the deer, whose testes, nonetheless, were about 10% the size of those of the sheep.

Plasma testosterone largely reflects testis size although the first period of gonadal activity by the deer did not result in a detectable peak of test- osterone {Fig. 5). Higher levels of testosterone were detected for sheep than deer.

All stags began to grow first pedicles, then antlers, in November and all had ceased antler growth by May. Three of them cleaned their antlers of velvet in June and cast them in July, when testis size was minimal. How- ever, one deer whose antlers were sawn off prior to cessation of growth

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failed to clean or cast the antler stumps and the second set of antlers grew, deformed, from these.

Immediately after casting, the remaining deer regrew antlers, whose growth was complete by September. All deer successfully cleaned their antlers shortly after growth ceased.

The antlers grown during both cycles tended to be short, and light (Table I).

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TABLE I

Length and weight of each antler grown by deer

Deer No. Cycle 1 Cycle 2

Length Weight Length Weight (cm) (g) (cm) (g)

74 L 23 -- -- --

R 16.5 -- -- --

75 L 18.5 55 32 193

R 14.5 52 31 237

76 L 27 46 21 79

R 27 56 18 68

77 L 13.5 13 32 87

R 13.0 19 26 72

DISCUSSION

The present study shows that reducing the period of the annual cycle of photoperiod from 12 to 6 months, in addition to doubling the number of antler cycles each year (Goss, 1969a), also doubles the number of food

297

intake, growth and gonadal activity cycles. In turn this indicates that photo- period is likely to be responsible for circannual rhythms in deer as has been shown for sheep.

The cross breed of sheep used in the present study is known for its rel- ative lack of a seasonal pattern of breeding (Robinson et al., 1975). It would appear to follow therefore that less marked reproductive cycles are accompanied by less well marked appetite and growth cycles (Kay, 1979). Had a breed of sheep with a pronounced cycle of breeding been used for this study, for example Soay sheep, then higher amplitude cycles of appetite or growth might have been expected (Kay and Suttie, 1980; Suttie, 1981).

The maximum live weight attained by the deer was similar to that re. ported for 15-month-old deer on a natural light cycle by Blaxter et al. (1974), and Suttie (1980).

The antlers grown by deer in the present study were smaller both in length and weight than those reported by Blaxter et al. (1974), and Suttie and Kay (1982), for penned stags on natural photoperiod. The antler length of yearling stags was about 30 cm and 2-year-olds 48 cm in Suttie and Kay's (1982) study. Corresponding weights were 150 g and 400 g, respec- tively. It is considered that the artificial photoperiod, by restricting the amount of time available to grow antlers, caused a reduction in size. This agrees well with Goss (1969a, b), who found that Sika deer (C. nippon) kept on artificial light had smaller antlers than controls on natural photo- periods.

Growth of the hind foot was unaffected by photoperiod, and continued to lengthen either throughout the study (deer) or until an asymptote was reached (sheep). This conforms with studies on deer such as those by Blaxter et al. (1974) and Suttie (1981), where skeletal growth continued during the first year of life irrespective of photoperiod or plane of nutrition.

The peak plasma level of testosterone was much higher in the sheep than the deer. This relationship was also shown by Suttie (1981), who compared Soay sheep -- a highly seasonally breeding animal -- with red deer. The function of this disparity is unknown, but sheep have testes 10 times larger than deer, so the difference may be purely physical. The seasonal pattern of development and regression of the testes probably indicates a seasonal pattern of fertility (Varadin et al., 1975); thus the rams and stags in the present study became fertile twice during one calendar year corresponding to the artificial photoperiod.

Events in the biannual cycle tended to lag some 3--4 months behind the position, relative to the photoperiod, which would have been expected, on the basis of information gained from natural photoperiods (Kay, 1979; Suttie, 1981). For example, the food intake trough occurred after daylength had already begun to increase, whereas one might have expected it to occur when daylength was decreasing, but before the simulated winter solstice. The reason for this is likely to be that although changes in daylength con-

298

trol the timing of cycles, there is an endogenous rhythm which the artificial photoperiod cannot fully suppress. This conforms with theories of regu- lation of seasonal cycles which propose that photoperiod entrains endo- genous rhythms (Bunning, 1958). Nonetheless, the artificial photoperiod was capable of inducing two cycles of growth, intake and gonadal develop- ment, in one calendar year in deer and sheep.

All cyclic functions occurred in the normal sequence in deer and sheep and the artificial photoperiod affected all equally; that is, peaks of gonadal activity, troughs of food intake and zero or negative weight gain tended to be associated temporally, and correspondingly, gonadal regression, peaks of food intake, weight gain and antler growth (deer) were associated. This may indicate that these cyclic functions share a common entraining mech- anism, whose sequence itself may be controlled by daylength.

ACKNOWLEDGEMENTS

Mr. E.D. GoodaU assisted with the measuring and sampling of both deer and sheep. A.M.S. and J.M.S. were in receipt of NERC post-graduate studentships.

REFERENCES

Blaxter, K.L., Kay, R.N.B., Sharman, G.A.M., Cunningham, J.M.M. and Hamilton, W.J., 1974. Farming the Red Deer. H.M.S.O, Edinburgh, 43 pp.

Bunning, E., 1958. The Physiological Clock. Longmans/Springer Verlag, Berlin. Gordon, J.G., 1964. Effect of time of year on roughage intake of housed sheep. Nature

(London), 204: 798--799. Goss, R.J., 1969a. Photoperiodic control of antler cycles in deer. 1. Phase shift and

frequency changes. J. Exp. Zool., 170: 311--324. Goss, R.J., 1969b. Photoperiodic control of antler cycles in deer. 2. Alterations in

amplitude. J. Exp. Zool., 171: 223--234. Kay, R.N.B., 1979. Seasonal changes of appetite in deer and sheep. A.R.C. Res. Rev.,

5: 13--15. Kay, R.N.B. and Suttie, J.M., 1980. Relationship of seasonal cycles of food intake

and sexual activity in Soay rams. J. Physiol. (London}, 310: 34--35P. Marshall, F.M.A., 1937. On the change over in oestrous cycles in animals after trans-

ference across the equator, with further observations on the incidence of the breed- ing seasons and the factors controlling sexual periodicity. Proc. R. Soc. London, Ser. B, 122: 413--428.

Robinson, J.J., Fraser, C. and McHattie, I., 1975. The use of progestagens and photo- periodism in improving the reproductive rate of the ewe. Ann. Biol. Anim. Biochim. Biophys., 15: 345--352.

Rowe, P.H., Lincoln, G.A., Racey, P.A., Lehane, J. Stephenson, M.J., Shenton, J.C. and Glover, T.D., 1974. Temporal variations of testosterone levels in peripheral blood plas- ma of men. J. Endocrinol., 61: 63--73.

Sadleir, R.M.F.S., 1969. The Ecology of Reproduction in Wild and Domestic Mammals. Methuen, London, 321 pp.

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Suttie, J.M., 1981. The influence of nutri t ion and photoper iod on the growth, develop- ment and endocrine status of captive red deer and Soay rams. Ph.D. Thesis. University of Aberdeen, 247 pp.

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Varadin, M., Stipancevic, L. and Pavlovic, A., 1975. Die Bedeutung der saisonabh~ingigen Ver~inderungen der Hodengrosse und Samenkanalchendurchmessers bei Schafbocken. Zuchthygiene, 10: 119--124.