Background: Dystocia occurs when there is a failure in one or more of the three main components of birth: expulsive force, birth canal adequacy and fetal size or position [ CITATION Mee08 \l 1033 ]. Deutscher (1991) indicated that the major cause of dystocia is a disproportion between birth weight and the ewe’s pelvic area. This finding is also supported by Cook et al., 1993 and Troxel, 2008. It is concluded that an incompatibility in size between the maternal pelvis and the lamb at birth is largely responsible for the need of assistance at birth (Anderson, 1992 and Patterson & Herring, 1997). Measuring pelvic areas is not a “cure-all” against lambing problems; but it may be a useful aid in a comprehensive ewe selection program to reduce dystocia and perinatal instability
[ CITATION Tro08 \l 1033 ]. The perinatal deaths according to Cloete, (1998) are caused by stressful births ascribed to a 60% prolonged labour period which reduces lamb survival (Dwyer, 2003).
Aim: The aim of the study was to investigate dystocia in mutton sheep and to estimate correlations between the ewe’s pelvic area, birth weight of the lamb and body measurements on the lamb. The Dohne Merino breed was used as a control group.
Methodology: The study during which the pelvic areas of 434 young Dohne Merino stud ewes were measured, was conducted late 2018 at Crux Dohne Merino’s on the farm Geluksdam of Mr Wikus Bekker in the Southern Free State. The pelvic areas of the ewes were measured on 13 March 2018, approximately two weeks before mating. Thereafter, the young ewes (18.5 months old) were mated from 1 April 2018 for two cycles (34 days). Single mating was practised by mating one ram to 60 ewes. Measurements recorded at lambing included: Length of parturition, birth weight, birth status of both the lamb and the ewe, circumference of the lamb’s head and pasterns, the lamb’s shoulder width and lambing ease score. The ewes grazed the natural pastures until two weeks prior to lambing and lambing took place in lambing pens with a balanced pelleted ration.
Results and Discussion:
The pelvic areas and mating weights of the 434 ewes is indicated in Table 1. Closed-circuit television (CCTV) was used to film the young ewes during parturition (picture 1). Eventually 191 ewes out of the 434 could be successfully filmed, out of which 274 lambs were born.
The pelvic area of the young Dohne Merino ewes measured 36.61 ± 3.64 cm2 at mating and the average mating weight of the Dohne Merino ewes were 57.42 ± 3.76 kg. Dohne Merino ewes born as one of a twin or multiple, had slightly bigger measured pelvic areas than singles. The Dohne Merino ewes took 63.11 ± 47.51 minutes on average to expel the new-born lamb as measured from the start of stage 2 of parturition. The lambs weighed 4.85 kg ±1.12 at birth, and their shoulder width measured 7.04 cm ±10.06. Pastern circumference measured 9.19 ± 0.62 cm, head circumference 25.25 ± 1.55 cm and chest circumference was 36.74 ± 3.87 cm. Only one percent of the 191 ewes, filmed on CCTV in this study, needed assistance. The pelvic area to birth weight ratio of the Dohne Merino ewes were 8.02 cm2/kg lamb born. On average their gestation length was 156 days, but no specific date could be linked to specific rams due to performing natural mating.
The following graphs indicate the difference between measurements on mutton sheep and Dohne Merinos. In both cases, young maiden ewes were used which were managed according to normal management practises followed for the breed. The Dohne Merino breed is usually classified as a medium to late maturing breed while mutton breeds are normally regarded as early maturing.
Graph 1 indicates the weight of the two types investigated as 53.31kg on average for mutton sheep and 57.42kg for Dohne Merinos.
According to Graph 2 the age at mating for the two types, was 9.7 months and 18.54 months respectively for mutton sheep and Dohne Merino ewes. Despite this huge age difference, both breeds were physically ready to be mated.
Graph 3 shows the pelvic area measured in cm2 of the two types. The average for mutton sheep 33.43 cm2 and 36.57 cm2 for the Dohne Merino ewes.
Graph 4 indicates birth weights of the two types as 3.7 kg for mutton sheep and 4.85 kg for Dohne Merinos. The weights were recorded within 24 hours after lambing as allowed for by specific farm operations.
Graph 5 shows the length of parturition (minutes it took to lamb) of the two types. Phase 2 of the lambing process which can theoretically be subdivided into three phases, was recorded. The average time it took for mutton sheep, was 60.50 minutes and 63.11 minutes for Dohne Merino ewes. The big difference was that Dohne Merino ewes needed assistance in only 1% of cases whereas 67% of the mutton sheep ewes needed assistance. To limit losses, the mutton sheep ewes were provided with 60-minutes to lamb before human intervention.
Grafiek 5 toon die lengte van die geboorteproses (minute wat dit geneem het om te lam) vir die twee tipes. Fase 2 van die lamproses wat teoreties in drie fases opgedeel word, is opgeneem. Die lamproses het gemiddeld 60.50 minute geduur by vleisskape en 63.11 minute by Dohne Merinos. Die groot verskil was egter dat die Dohne Merino slegs in 1% van gevalle hulp nodig gehad het, terwyl 67% van die skaapvleis-ooie hulp moes kry. Om verliese te beperk, is die vleisskape ‘n periode van 60 minute toegelaat om te lam voor menslike ingryping.
Graph 6 shows the pelvic area in cm2 to kg lamb born. In the case of Dohne Merinos, one kg of lamb was born for every 8.02 cm2 of pelvic area. As apposed to Dohne Merinos, the mutton sheep ewes had a more favourable pelvis area of 9.69 cm2 available to produce one kg lamb but still had a greater incidence of dystocia (67 percent compared to one percent).
Conclusion: The results of the study indicate that young Dohne Merino ewes have an excellent ability to lamb without any assistance. Although the mutton sheep breed has a more favourable pelvic to birth weight ratio than the Dohne Merino ewes, Dohne Merino ewes experienced lambing difficulty in only one percent of cases, whereas 67% of the mutton breed needed assistance. It is recommended that mutton breeds investigate the possibility to mate ewes at a later age possibly as is the case with Dohne Merinos, to decrease the incidence of dystocia.
Acknowledgement: The assistance and provision of ewes by Mr Wikus Bekker is appreciated.
Rerences/Verwysings:
Anderson, P., 1992. Minimizing Calving Difficulty in Beef Cattle.
Cloete, S. et al., 1998. Ease of birth relation to pelvic dimensions, litter weight and conformation of sheep. Small Ruminant research, Volume 31, pp. 51-60.
Cook, B. R., Tess, M. W. & Kress, D. D., 1993. Effect of selection strategies using heifer pelvic area and sire Birth weight expected progany difference on dystocia in first- calf heifers. Journal of Animal Science, March, Volume 71, pp. 602 – 607.
Deutscher, G. H., 1991. Pelvic Measurements for Reducing Calving Difficulty.
Dwyer, C., 2003. Behavioural development in the neonatal lamb; effect of maternal and birth-related factors. Theriogenology, 1027-1050.
Mee, J. F., 2008. Prevalence and risk factors for dystocia in dairy cattle: A review. The Veterinary Journal, 18 December, Volume 176, pp. 93-101.
Patterson, J. P. & Herring, W., 1997. Pelvic measurements and calving difficulty in beef cattle.
Troxel, T. R., 2008. Pelvic area measurements in the management of replacement heifers.
Agtergrond: Dystokia kom voor wanneer daar fout kom met een of meer van die drie hoofkomponente van geboorte nl.: uitdrywingskrag, geboortekanaal- toereikendheid en fetale grootte of posisie (Mee, 2008). Deutscher (1991) het aangedui dat die grootste oorsaak van dystokia ‘n disproporsie is tussen geboortegewig en die bekkenarea van die ooi. Hierdie bevinding word ook ondersteun deur Cook et al., 1993 and Troxel, 2008. Daar word tot gevolgtrekking gekom dat die onverenigbaarheid in grootte tussen die moederlike bekken en die lam se gewig by geboorte, grotendeels verantwoordelik is dat hulp verleen moet word by geboorte (Anderson, 1992 en Patterson & Herring, 1997). Die meting van bekkenareas is nie ‘n “geneesmiddel” teen lamprobleme nie maar dit mag ‘n nuttige hulpmiddel wees in ‘n uitgebreide ooi seleksieprogram om die voorkoms van dystokia en perinatale onstabiliteit te verminder (Troxel, 2008). Die perinatale sterftes (Cloete, 1998), word veroorsaak deur stresvolle geboorte wat toegeskryf word aan ‘n 60% verlengde kraamtyd wat die oorlewing van lammers verlaag
(Dwyer, 2003).
Doel: Die doel van die studie was om dystokia by ‘n vleisskaapras te ondersoek en die korrelasies tussen die ooi se bekkenarea, die geboortegewig van die lam en die liggaamsmetings van die lam te bepaal. Die Dohne Merino-ras is as ‘n kontrolegroep gebruik.
Metodologie: Die studie waardeur die bekkenareas van 434 jong Dohne Merino- stoetooie gemeet is, is laat 2018 uitgevoer by Crux Dohne Merino’s op die plaas Geluksdam van Mnr Wikus Bekker in die Suid-Vrystaat. Die bekkenareas van die ooie is op 13 Maart 2018, ongeveer twee weke voor paring gemeet. Jong ooie (18,5 maande oud) is daarna van 1 April 2018 vir twee siklusse (34 dae) gepaar. Enkel paring met een ram vir elke 60 ooie is toegepas. Metings wat tydens lamtyd aangeteken is, sluit in: lengte van die geboorte, geboortegewig, geboortestatus van die ooi en die lam, omtrek van die lam se kop en kloutjies, skouerbreedte van die lam en gemak van geboorte puntetelling. Die ooie het op natuurlike weiding tot twee weke voor die lamtyd gewei en hulle het in lamhokke met ‘n gebalanseerde korrelrantsoen gelam.
Resultate en Bespreking:
Die bekkenarea en die paringsgewig van die 434 ooie word in tabel 1 aangedui. Geslote kringtelevisie (CCTV) is gebruik om die jong ooie tydens geboorte te verfilm (foto 1). Uiteindelik, kon 191 ooie uit die 434 suksesvol verfilm word waaruit 274 lammers gebore is.
Table 1 Measurements on young Dohne Merino ewes and lambs.
Die jong Dohne Merino-ooie se bekkenarea het met paring 36,61 ± 3,64 cm2 gemeet en gemiddelde paringsgewig was 57,42 ± 3,76 kg. Dohne Merino- ooie wat een van ‘n tweeling of meerling was se bekkenareas het effens groter gemeet. Die Dohne Merinos het gemiddeld 63,11 ± 47,51minute geneem van stadium 2 van geboorte af, om die lam uit te druk. Die lammers het by geboorte 4,85 kg ± 1,12 geweeg, en hul skouerwydte was 7,04 cm ± 10,06. Kloutjiesomtrek was 9,19 ± 0,62 cm, kopomtrek 25,25 ± 1,55 cm en borsomtrek 36,74 ± 3,87 cm. Slegs een persent van die 191 ooie op CCTV verfilm, het hulp nodig gehad met geboorte. Die Dohne Merino-ooie se bekkenarea- geboortegewig-verhouding was 8,02 cm2 / kg lam gebore. Hulle dragtigheidslengte was gemiddeld 156 dae, en spesifieke datums kon nie aan spesifieke ramme gekoppel word nie aangesien natuurlike dekking gedoen is.
Die volgende grafieke toon die verskil in metings tussen ‘n vleisskape en Dohne Merinos as kontrole. In geval van beide rasse is jong ooie aangewend wat volgens normale bestuurspraktyke vir die ras, bestuur is. Dohne Merinos word geklassifiseer as ‘n medium tot laat ryp ras terwyl vleisskape normaalweg as vroegryp beskou word.
Grafiek 1 dui die gewig van die twee tipes aan as gemiddeld 53,31 kg vir vleisskape en 57,42 kg vir Dohne Merinos.
Volgens Grafiek 2 was die paringsouderdom van die twee tipes 9,7 maande en 18,54 maande respektiewelik vir vleisskape en Dohne Merinos. Ten spyte van hierdie groot ouderdomsverskille, was beide tipes wat fisiese bou betref, paargereed.
Grafiek 3 toon die bekkenarea gemeet in cm2 van die twee rasse. Gemiddelde waardes vir vleisskape was 33,43 cm2 en 36,57 cm2 vir Dohne Merinos.
Grafiek 4 dui geboortegewigte aan as gemiddeld 3,7 kg vir vleisskape en 4,85 kg vir Dohne Merinos. Die gewigte is binne 24 uur na lamtyd aangeteken soos spesifieke plaasbedrywighede dit toegelaat het.
Grafiek 5 toon die lengte van die geboorteproses (minute wat dit geneem het om te lam) vir die twee tipes. Fase 2 van die lamproses wat teoreties in drie fases opgedeel word, is opgeneem. Die lamproses het gemiddeld 60.50 minute geduur by vleisskape en 63.11 minute by Dohne Merinos. Die groot verskil was egter dat die Dohne Merino slegs in 1% van gevalle hulp nodig gehad het, terwyl 67% van die skaapvleis-ooie hulp moes kry. Om verliese te beperk, is die vleisskape ‘n periode van 60 minute toegelaat om te lam voor menslike ingryping.
Grafiek 6 toon die bekkenarea in cm2 per Kg. lam gebore. In die geval van Dohne Merinos is een kg lam gebore vir elke 8.02 cm2 bekkenarea. Vleisskape het hierteenoor ‘n meer gunstige 9,69 cm2 bekken area gehad om een kg lam te produseer maar het steeds ‘n groter voorkoms van dystokia (67 persent teenoor een persent) ondervind.
Gevolgtrekking: Die resultate van die studie dui
daarop aan dat die jong Dohne Merino-ooie in
hierdie studie ‘n uitstekende vermoë het om
sonder enige hulp te lam. Alhoewel die vleisskape
se groter bekkenarea, ‘n gunstiger verhouding met geboortegewig as die Dohne Merinos het, het Dohne Merino ooie slegs in 1% van gevalle lamprobleme ondervind, terwyl 67% van die vleisskaap ooie hulp nodig gehad het. Dit word aanbeveel om vleisskaap ooie moontlik ook op ‘n later ouderdom soos die praktyk met Dohne
Merino ooie, gepaar word om dystokia te vermy.
Erkenning: Die hulp en voorsiening van ooie deur Mnr Wikus Bekker word waardeer.
Rerences/Verwysings:
Anderson, P., 1992. Minimizing Calving Difficulty in Beef Cattle.
Cloete, S. et al., 1998. Ease of birth relation to pelvic dimensions, litter weight and conformation of sheep. Small Ruminant research, Volume 31, pp. 51-60.
Cook, B. R., Tess, M. W. & Kress, D. D., 1993. Effect of selection strategies using heifer pelvic area and sire Birth weight expected progany difference on dystocia in first- calf heifers. Journal of Animal Science, March, Volume 71, pp. 602 – 607.
Deutscher, G. H., 1991. Pelvic Measurements for Reducing Calving Difficulty.
Dwyer, C., 2003. Behavioural development in the neonatal lamb; effect of maternal and birth-related factors. Theriogenology, 1027-1050.
Mee, J. F., 2008. Prevalence and risk factors for dystocia in dairy cattle: A review. The Veterinary Journal, 18 December, Volume 176, pp. 93-101.
Patterson, J. P. & Herring, W., 1997. Pelvic measurements and calving difficulty in beef cattle.
Troxel, T. R., 2008. Pelvic area measurements in the management of replacement heifers.