Badenhorst, J.F.G.

Skinner, J.D.

van Rensburg, S.J.

English

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S. Afr. J. Anim. Scr.,  l ,  69--71 (1971)THE OCCURRENCE OF FOETAL DWARFIST{ IN THEANGORA GOATJ.D. Skinner, S.J. van Rensburg* and J.F.G. Badenhorst**Division of Animol Physiologlt, Irene, *National Institute .fbr Nutritional Diseases, M.R.C. and**Resurch Institute oi the Ttansvaal Region, Pretorio.Foetal dwarfism following heat stress during preg-nancy has been reported previously in sheep (Yeates,1953, 1958; Epstein & Herz, 1964: Shelton, 1964) andcattle (Bonsma, Badenhorst & Skinner, 1972) but not sofar in goats. The object of the present note is to reporton the occurrence of foetal dwarfing in Angora goatswhen introduced from a temperate region of SouthAfrica into a more unfavourable environment.The data presented are observations made on aflock of 27 does transferred in 1966 from the temperateEastern Cape Province to Messina Research Station,(22oS) situated in the sub-tropical Bushveld of the Nor-thern Tranwaal; for details of the climate vide Bonsma,van Marle & Hofmeyr (1953). Observations on the birth-weight of kids born at Onderstepoort (2605) are alsoincluded. Onderstepoort is situated about 470 k south ofMessina, verging on the sub-tropics, and about 1000 knorth of the Angora farming areas in the Eastern Cape.These data are compared with the weights from kidsborn at Grootfontein Agricultural College (3los) in theCape Province. The Messina does were mated each year(1966-1970) from July, I and, after a summer gestationperiod, the kids were born in December and early January.The Onderstepoort does were mated each year ( 1964-1968) from April and the kids were born in September;while the Grootfontein kids ( t966- 1970) were born inSeptember, following autumn mating. The birthweightsof the kids are presented in Table I and the mean maxi-mum temperatures and highest maximum temperatures inthe three areas recorded during pregnancy are presentedin Table 2.The mean birth weights of the kids at Messina andOnderstepoort were of the same order. Three male minia-ture kids were born at Messina during the six years.Two weighed 1,3 kg and one'1,8 kg wi th a mean weightonly 50,3 % of that of normal males. These kids did notgrow well. The first dwarf only weighed 4,0 kg at weaningat 120 days cf. I 1.8 kg for normal kids at Messina (Plate l).The kid died soon after being weaned and deprived ofmaternal care and nutrition. The second kid died soonafter birth from unknown causes. The third dwarf diedof heartwater at 60 days of age when it weighed 3,6 kgcf . 6,4 kg for two normal kids. Although one female kidweighed 1,8 kg, it grew normally. As in the Shorthorn(Bonsma at ol, 1972) normal kids were born at the sametime as dwarfs which illustrates the wide variation in in-dividual response.Dwarf kids born in the Onderstepoort flock usuallydied within a few days of birth, notwithstanding consider-able efforts to save them. Of five that weighed less than 2kg at birth and survived, only one was severely retarded atweaning on the l20th day. It then weighed 7 kg as com-pared to the normal weight of l4 or l5 kg. However, threeother kids weighing 2,2: 2,4 and 3,I kg at birth were dwarfsat weaning when they weighed 6,6: 7,5 and 7,5 kg.All u.ndersized kids in the Onderstepoort flockwere born after a normal gestation period of between 143and 153 days. Kids delivered prematurely before thel43rd day were without exception stillborn and it istherefore unlikely that the Messina dwarfs were born pre-maturely. It is impossible in retrospect o deduce whenfoetal development was affected. Shelton & Huston ( 1968)induced foetal dwarfing in sheep by exposing ewes in tem-perature control chambers for the last half of pregnancyto a temperature of 32oC for 12 hours per day, and Edey(1969) mentions that high temperatures during mid-pregnancy can cause foetal dwarfing in the sheep.At Messina, where the incidence of dwarfing was19% and the mean kidding percentage only 10,5% perannum, highest maximum temperatures exceeded 32oCvirtually throughout pregnancy but the mean maximumtemperature only exceeded 32oC in November and Decem-ber. On the other hand, temperatures at Onderstepoortdid not reach these extremes, and the incidence of dwarfingwas sti l l  l2%. These goats had particular diff iculty inadapting to stall fed hay and concentrates as they are natu-ral browsers, preferring a short scrub and bush type ofvegetation as is found in the Cape and, to a lesser extent,Messina. It would seem that there is more than one factorinvolved, and as the environment becomes progressivelymore unfavourable for the Angora, in terms of temperatureand nutrit ion, the l ikelihood of dwarfism will increase.A,s in the case of the dwarf Shorthorns at Messina(Bonsma et al, 1972) the dwarf goats at Messina weremales; however, there were also female dwarfs born atOnderstepoort. It has been suggested by Bonsma et al(1972),that the reason for foetal dwarfing in the male couldbe due to a higher metabolic rate in the male foetus whichin turn irnposes a greater temperature strain on the damwith a low heat tolerance coefficient. lt has also beensurmised that there nray be a nutrit ional def iciency affect-ing the deveioping foetus due to a reduct ion in uter ineblood supply (Shelton, 1964). This results from theincreascd peripheral circulation to diss;pate heat load.69TableBirthweights of single Angora kids born in oreas in South Africa t S./:.IthreeScx o fN o .WcrghtMcan t  S I r .( kg )Range( k g )%1 . 9kgWc igh t  asperccntageNorma l *McssinaOnde rstcpoortGroot fontc inMale 9F emale 7A l l  k ids  16Male 44Female 39Al l  k ids 83Ma le  137Female |  55All kids 2922 .50  t  0 .202,30 t  0 ,202,40 10,052 ,52  !  O ,822 ,32  t  0 ,592.40 !  0 .673.04 r 0.042,64 t 0,042.83 j  0 .03| , 3  3 . 6I , r j  _1.2l . . l  1 ,6| , l  4 . 51 ,4  -  2 ,9I , l  4 . 5r , 9  -  4 , 31 . 5  -  3 , 71 , 5  -  4 , 33  3 , 342.61  5 ,9I  2 ,806,48 l , 68 7 ,  I82 .98  7 ,9NormalNormal*  Normal taken as mean weisht  of  Groot fontein k ids.Table 2Meon maximum temperature oC and highest temperature recorded during gestationArea MonthMcssina 25.3V I I  V I I I28,9; 22,4 3 2.5 :t x29,7 34.5 31.3X  X I  X I I39 .4 ;  32 .5  40 ,6 ;  32 ,8  38 .7 ;I V VOndcrstcpoort 25,8 29,4: 23,0 26,2:V I20.3 24.7: 20.4V I I  V I I I25 ,6 ;  23 .2  28 .1 :IX26.6 3 2,IV I1 6 , 8  2 1 , 5 ;vil vlt l16 .3  24 .7 :  18 .9  32 .5txGrootlontcin 24.0 30.7 : t9.7 26 .9 :*, iPlate l. - Angora kids of the vme ages whenThe normal kid weighed I 1,8 kS cl120 days old.4,0 kg for the dwarl.70Dissection studies on non-viable miniature kids atOnderstepoort revealed that such kids had very muchsmaller pituitaries, thyroid and adrenal glands (Van Rens-burg, 197l) suggesting a state of congenital hypopituitarism.There is no question of this condition being hereditarysince a high incidence was recorded among does importedfrom flocks in the Cape where the problem is unknown. lnproportion to bodyweight, the weight of the pituitariesof dwarfs was still reduced by approximately 2O%, butthis state was not confined to kids which were under-sized at birth. These observations are in agreement withthe finding that kids with a normal birthweight may mani-fest as typical miniature dwarfs at four months of age.The data is also not compatible with the hypothesis thatdwarfism results from an inadequate intrauterine nutri-t ional environment. whether it is mediated via reduced ute-rine blood flow in order to dissipate excessive heat loadperipherally, or frank nutrit ional deficiency.An acceptable hypothesis could be the selectivesuppression of the maturation of the foetal endocrinesystem by abnormal levels of maternal hormones. Star-vation and excessive heat are both known to markedlyincrease adrenocortical function. Maintained high levelsof maternal glucocorticosteroids may not only suppressfoetal pituitary development but could contribute to thefoetal dwarfism syndrome by virtue of their anti-anabolicand hence growth suppressing actions. Under such circum-stances incidental adrenal androgen secretion will also beincreased and if the male foetal pituitary is indeed morereceptive to androgenic zuppressive ffects it may accountfor the higher incidence of dwarfism amongst males insome species.AcknowledgementWe would l ike to thank Dr. J.E. Nel of GrootfonteinAgricultural College, Middelburg, C.P., for providing thenormal birthweights with which we could make compari-sons.ReferencesBONSMA, J.C.,  BADENHORST, J.F.G. & SKINNER, J.D.,1972. The incidence of foetal dwarfism from Short-horn cattle in the zubtropics. (Submitted for publi-cation).BONSMA, J.C.,  VAN IUARLE, J.  & HOFMEYR, J.H.,1953.  Emp.J .  exp .  Agr ic .  21 ,154.EDEY, T.N., 1969. Ch. 6 in Animal Reproduction, ed.B.J.F. James Melbourne: F.W. Cheshire.EPSTEIN, H. & HERZ, A.. 1964. Z. Tierz. ZuchtBiol.go,  232.SHELTON, M.,  1964. J.  Anim. Sci .  23,360.SHELTON, M. & HUSTON, J.E.,  1968. J.  Anim. Sci .  27,I  5 3 .VAN RENSBURG, S.J., 1971. Onderstepoort J. vet. Res.3 8 ,  l .YEATES, N.T.I | . ,  1953. J.  agr ic.  Sci . ,  Camb. 43, 199.YEATES,  N.T .M. ,  1958.  J .  agr ic .  Sc i . ,  Camb.  51 ,  85 .7 l

The occurence of foetal dwarfism in the Angora goat

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The occurence of foetal dwarfism in the Angora goat

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