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This article was published in 1988
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A Study of Neonatal Mortality in a Beef Herd
C.D. Gee, B.V.Sc.* and E.R. Gaden, B.Sc.Agr.**
ABSTRACT
A pilot study of neonatal deaths in a herd of 250 beef, Shorthorn cattle on the Southern Tablelands of New South Wales is reported. Death rates as high as 44% from heifer groups are described.
A comparative trial using parenteral iodine eliminated congenital goitre as a possible cause. There were 30 neonatal deaths. 26 were confirmed as due to maternal dystocia.
Pathological changes in many of the dystocia caused deaths were minimal but a congested, swollen tongue was a definitive lesion.
Ratios of thyroid weight to calf body weight were examined for 25 of the calves. The mean was 0.56 gm/kg.
The death rate was higher in heifers mated at 14 to 16 months of age than in those mated at 20 to 22 months. However the numbers were not large and the result was not significant.
Significantly more male than female calves died from maternal dystocia.
The use of a Jersey bull for heifer matings eliminated the dystocia problem. The Jersey cross allowed safe, early mating at 14 months of age.
INTRODUCTION
These observations are presented as a pilot study of the causes of neonatal death in a beef herd at Goulburn on the southern tablelands of New South Wales. Neonatal calf deaths had been a problem on this highly improved property for at least four years.
The 1438 hectare property runs some 8,000 sheep and 250 beef cattle. It is situated only a few kilometres to the west of Goulburn and is one of the better grazing properties of the district. Several hundred hectares are of a rich alluvium on creek flats. The rest of the property is gently undulating terrain with sedimentary, duplex soils. They are moderately acidic with the acidity increasing to the ridges. Pastures respond to phosphorus, sulphur and molybdenum. Natural timber cover consists of large specimens of box and gum.
The property has been well improved by applications of molybdenum and superphosphate over many years. All paddocks have been pasture improved and vary from excellent on the alluvial flats to sound on the lighter hills.
The cattle were good quality Shorthorns. The breeding herd was self replacing with the steers and excess heifers normally sold as vealers and yearlings. Heifers were mated at about 22 months of age to calve as two year olds.
From 1980 onward the owner sought the assistance of the authors with an unacceptable number of calf deaths. In 1980 there were 12 neonatal deaths in a mob of 46 heifers. Autopsies on four calves indicated dystocia as the cause of death. The diagnosis was given with some reserve because the calves were not excessively large and the head oedema and congestion were minimal.
In 1981 there were 14 neonatal deaths in a mob of 40 heifers. There were also about 10% of neonatal deaths in the older cows. Again the head oedema and congestion were minimal and causes other than dystocia began to be suspected. Death rates in 1982 and 1983 were lighter but still a cause for concern. Neonatal goitre was known to be an occasional occurrence in sheep in that general area. Some of the calves had larger thyroids than the expected normal. Suspicion began to fall on goitre as the cause, or a contributing cause, of the mortality.
In mid September, 1983 a stillborn call from a mature cow was autopsied. The total thyroid wet weight was 79 gm. One week later a similar calf was examined with a thyroid weight of 34 gm. At histopathology at the Regional Veterinary Laboratory at Glenfield both thyroids were described as severe hyperplastic goitre with little or no visible colloid.
In 1984 a trial was begun with the aim of closely studying the neonatal deaths. It was decided to set up a controlled field experiment with the aim of testing parenteral iodine in the prevention of neonatal death in the herd. All dead calves would be weighed, autopsied and identified to the mother.
Observations continued in 1985 and 1986 with the emphasis swinging to the effects of dystocia in neonatal death. The possible correlation between maternal, pelvic area and neonatal death was tested.
MATERIALS AND METHODS
The mating and management of the herd was in accordance with the owner's normal practice.
Mob 1 was composed of 31 heifers mated at 14 to 16 months of age and 28 heifers mated at 20 to 22 months of age. The two groups were run together from 7 weeks before mating until completion of calving. Mobs 2 and 3 were of 34 and 50 adult cows respectively.
Each mob was grouped by a random number system intended to provide about two thirds, iodine treated and one third untreated. The treatment used was an oily, iodine injection.*** The product is known to provide prophylactic iodine levels over a long term. The current recommendation of the manufacturer is for a 4 ml injection every 2 years.
On 6 June 1984 the selected females were injected intramuscularly with 4 ml of the iodine product.
Calving began on 20 July 1984. Most aborted and stillborn calves were autopsied. Calf weight and dam identification were recorded. Whole thyroids were weighed fresh and undried after removal of extraneous tissue. Formalin preserved sections of thyroid were examined at the Regional Veterinary Laboratory at Glenfield, New South Wales.
Cows which were non pregnant or which died prior to parturition were eliminated from the trial.
Cross sectional pelvic dimensions were measured for 27 cows in Mob 1. Possible correlations between pelvic measures and neonatal death were studied.
The instrument used was a proven device for obtaining estimates of vertical and horizontal pelvic measurement. ****
When results of the 1984 trial became available, the owner was encouraged to test a Jersey bull for heifer matings. There was no controlled trial but neonatal deaths were recorded and compared with previous years.
RESULTS
Deaths
Losses of calves in the 1984 calving were heavy. There were 30 neonatal deaths from the 143 cows. The incidence of dead calves was much heavier in the heifers than the cows. There were 7 dead calves from 74 cow calvings and 23 from 52 heifer calvings. This difference is highly significant (X2 = 20.35). The iodine treatment clearly failed to reduce the death rate (Table 1). 24 of the deaths were confirmed by autopsy as due to dystocia. Another 3 were strongly suspected as dystocia leaving only 3 deaths attributable to other causes.
There was no significant difference in the death rate between the heifers mated at 14 to 16 months of age and those mated at 20 to 22 months of age (15 ex 28 versus 8 ex 24)(x2 = 2.15).
There were 19 confirmed dystocia deaths from the heifer group for which the sex was recorded. 14 were male and 5 were female. This difference is highly significant (X2 = 6.72).
Weights of dead calves ranged from 15.5 to 35.4 kg with a median of 32.2 kg and mean of 29.3 kg. This is considered normal for the breed.
Total thyroid wet weights ranged from 6 to 43.5 gm with a median of 14.3 gm and mean of 16.5 gm.
The ratio of total thyroid wet weight in grams to calf weight in kilograms ranged from 0.25 to 1.5 with a median of 0.52 and mean of 0.56.
Gross Pathology
26 of the 30 dead calves were autopsied. 15 had marked congestion and oedema of the muzzle area extending to a variable extent aborally to the cranial area. 6 had only light to moderate congestion and oedema about the muzzle region with very limited aboral extension. All 21 calves with muzzle oedema had a characteristic tongue lesion. On cross section, about 4 cm from the tip, the tongue was strongly congested. The cross sectional shape tended to an equilateral triangle in contrast to the flattened oval of the normal tongue.
The owner assisted at parturition in 6 of the 15 cases with marked facial oedema and in 2 of the 6 cases with lighter, more restricted oedema. This history provided support for the characterisation of the oedema as a definitive lesion of neonatal death due to dystocia.
Two calves had congestion and oedema of the hind legs but not of the head. One of these cows was assisted by the owner in a posterior presentation. Both were classed as malpresentation dystocias.
Three calves from mature cows did not have lesions suggestive of dystocia. Two survived for some days with autopsies indicating starvation and neonatal infection respectively. The third was a perinatal death with patchy aeration of the lungs and no diagnosis was reached.
Four calves were not examined. The owner noted facial oedema in two. Another was found in a decomposed state in a dam. One heifer was found dead by the owner and had clearly died in dystocia. Three of the four may thus be safely categorised as dystocia deaths.
In summary 26 deaths were due to maternal dystocia, 1 to starvation, 1 to infection and 2 to unknown causes.
Histopathology
23 thyroids were suitable for histopathology. 13 resulted in no significant findings. 10 had non specific lesions, usually including congestion and, in several cases, haemorrhage into some follicles. In several cases there were up to 20% of follicles with columnar epithelium.
The interpretation was that there were no consistent histological lesions and that the histopathology was consistent with neonatal death due to dystocia.
Maternal Pelvic Measurement
On 20-6-85, 27 cows were examined and pelvic measurements taken. The cows were first calf cows derived from the heifer group of 52 in the calving trial. 5 were cows whose calves had died from dystocia in the trials.
Vertical and horizontal measurements were recorded. Numbers were insufficient for any valid deductions. However the measurements for the cows with a history of dystocia were similar to those of the normal cows. Results are in Table 2.
Jersey Bull
The main 1984 trial clearly established heifer dystocia as the major cause of neonatal death on the property. It was known that other owners had elected to mate their heifers to Jersey bulls to eliminate the problem.
The owner decided to mate all heifers to calve in 1985 to a Jersey bull. A mob of some 35 heifers were mated to calve at 24 months of age. All calvings resulted in live calves and no heifer required calving assistance. There were only 3 neonatal deaths for the season and all three were from mature cows mated to Shorthorn bulls. No autopsies were performed so the cause of death remains unknown.
DISCUSSION
The initial aim of the trial was to test a parenteral iodine injection in the prevention of neonatal calf deaths suspected to be due to goitre.
Clearly the results have eliminated goitre as a possible cause of the problem. Further, the death rate was higher in the iodine treated than in the untreated group. There was no need for statistical analysis to support the interpretation that the parenteral iodine had not reduced the death rate.
However it was also clear that the parenteral iodine product was a very practical and convenient way of providing long term iodine supplementation (up to 2 years).
Despite the negative result with the iodine supplementation, there were many useful results arising from the detailed observations. The gross pathology in many calves was not striking. Though dystocia was known to be the cause of the deaths, the extent and degree of oedema and congestion of the head were often limited, The strong impression was that relatively mild oedema of the lips and muzzle was consistent with a diagnosis of dystocia death. A congested tongue with a tendency to a triangular cross section was a consistent feature.
The death rate of calves from the cow group was 7 ex 75 calvings (9.3%) and 3 deaths were not due to dystocia. 23 calf deaths resulted from the 52 heifer calvings (44%). Only one was not confirmed as dystocia related. The strong impression was that the problem is important only in heifers and that the same animals in later life will calve without undue trouble.
The higher incidence of neonatal death in the heifers mated at 14 to 16 months of age over those mated at 20 to 22 months of age was interesting. It was not statistically significant but appeared to be a real difference rather than merely sampling variation. The 15 calf deaths from 28 calvings in the heifers mated at the younger age was clearly an unacceptable death rate for any commercial herd.
This observation is at variance with other published records suggesting that there is no correlation between heifer dystocia and age at mating (Young 1970).
The significantly higher number of males in the heifer dystocia calf deaths was consistent with other studies (Morris C.A. et al.).
Thyroid Weight
The total thyroid wet weights varied from 6 to 43.5 gm. The median of 14.3 gm in non goitrous thyroids was higher than expected. Some references indicate a much lower normal range such as a mean of 6.5 gm (Blood et al. 1983). It is postulated that, in anterior presentation dystocia, the thyroid is strongly affected by the head oedema and congestion induced by pressure effects. Clearly the oedema would increase the thyroid weight by quite a large factor.
It was the original thought of the authors that the ratio of thyroid weight to body weight would be a more useful indicator than thyroid weight alone. References have since been found to support this opinion (Hernandez et al. 1972 cited by Mason 1976).
The ratio in our series varied from 0.25 to 1.5 gm/kg with a median of 0.52. This was not strikingly different from the normal of 0.35 quoted by Hernandez.
The 1983 incorrect diagnosis of congenital goitre in this herd raises some questions. Histological observations should not be taken as diagnostic but merely as useful aids to diagnosis. Thyroid weights should be considered in relation to calf body weight with due recognition of the effects of passive congestion in dystocia.
Mason (1976) ranked histology as of more diagnostic importance then thyroid weight with total, thyroid iodine content of intermediate importance. However he stressed that not one of these criteria alone was ideal as a diagnostic tool. He recommended thyroid to bodyweight ratio as a useful indicator of the severity of goitre.
Other Properties
The experience of the writers in the Southern Tablelands of NSW was that heifer dystocia was a cause of heavy calf mortality rates on many properties in certain seasons.
Enquiries about 1984 calvings revealed the following case histories :
Owner A
In a mob of some 100 Hereford heifers mated to Angus bulls 75% had dystocia. The calf death rate was 50% of calvings.
Owner B
The dystocia rate in Hereford heifers mated to Hereford bulls in this large herd was commonly up to 25% with a related calf death rate of 20% of calvings.
Owner C
Another large Hereford herd with a heifer dystocia rate of 25% in good seasons and deaths of 10% of calvings.
Owner D
An example of a small owner with a heavy loss rate. 7 of 10 Hereford two year old heifers had dystocia leading to 4 calf deaths.
Case reports like these have been by no means unusual. Observations on a number of New South Wales properties revealed a 15% calf death rate in heifers due to dystocia (Young (1970)].
Breeding Management
Possible solutions were considered after the 1984 trial. These included selection for larger pelvic area in heifers, nutritional changes and selection of sires for lower birth weight of progeny.
Literature studies and the experience of the writers suggested that selection procedures would be slow and unrewarding. Similarly it appeared that nutritional management would require near starvation to significantly reduce birth weight. Feeding of a below maintenance ration for at least three months has been claimed to be necessary to achieve any marked reduction in calf birth weight [Young (1970)]. This would be difficult on a commercial property and would reduce productivity.
Mating of the heifers to a breed known to reduce birth weight seemed to be the best choice. To provide some certainty that the required effect would be achieved, it was decided to use a Jersey bull over the heifers.
The results have suggested that the use of a Jersey bull can eliminate the heifer dystocia problem. The manager may then choose to mate heifers to calve at 24 months instead of 30 to 36 months of age. The net effect is virtually a bonus calf crop with no dystocia problem.
Admittedly the Jersey cross calves are strongly discounted in the market place. However this effect is less at a younger age and the Jersey cross calves perform quite well to the vealer stage (to 12 months of age). It is also worthy of note that a keen buyer was found for the female, Jersey cross calves for use as vealer mothers.
The extent of the market place discounting is hard to quantify. The male vealers were sold at 4 to 5 months of age for from $90 to $132. The owner's assessment is that the penalty due to the Jersey cross is about 15%. He feels that most of the penalty at this age is due to a correspondingly lower weight than the purebreds.
The heifer calves were held for a further 6 months or so and were sold for up to $150.
The owner also remarks that the first-calf cows carry less fat through their second pregnancy and calve well to beef bulls at their second calving.
It is highly probable that other sires may be proven to succeed in eliminating heifer dystocia with a much less severe market discount for the progeny. This is an avenue for further study.
ACKNOWLEDGEMENTS
We thank Mr GM for making his commercial herd available.
We acknowledge the assistance and support of May & Baker Australia Pty, Ltd and thank them for their donation of the parenteral iodine product.
REFERENCES
Blood, D.C., Radostits, O.M. and Henderson, J.A. (1983) - 'Veterinary Medicine'. Baillière Tindall; 6th Ed., London
Mason, R.W. (1976): Aetiological Studies of Ovine Congenital Goitre in Tasmania with Particular Reference to the Cressy-Longford Area. M.V.Sc. Thesis, Univ. of Melbourne.
Morris, C.A.; Bennett, G.L.; Baker R.L.; Carter, A.H. (1986): Birth weight, Dystocia and Calf Mortality in Some New Zealand Beef Breeding Herds. J. Anim. Sci. 62:327-343
Young, J.S. (1970): Management of the Beef Heifer for Maximum Reproductive Performance. Vet. Review No. 9 of the University of Sydney Post-graduate Foundation in Veterinary Science
FOOTNOTES
* Goulburn Pastures Protection Board, Box 67, Goulburn, N.S.W, 2580
** Department of Agriculture, 159 Auburn St, Goulburn, N.S.W, 2580
*** Lipiodol - May & Baker Australia Pty Ltd, 19-23 Paramount Rd., West Footscray, Victoria, 3012
**** The Rice Pelvimeter - Lane Manufacturing Inc., 2057 South Hudson, Denver, Colorado, 80222
TABLE 1
Calf Deaths by Dam Age and Iodine Treatment
| TREATED | UNTREATED | TREATED & UNTREATED | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Dead | Live | Dead % | Dead | Live | Dead % | Dead | Live | Dead % | |
| Cows | 6 | 38 | 14 | 1 | 29 | 3 | 7 | 67 | 9 |
| Heifers | 17 | 18 | 49 | 6 | 11 | 35 | 23 | 29 | 44 |
| Heifers & Cows | 23 | 56 | 29 | 7 | 40 | 15 | 30 | 96 | 24 |
TABLE 2
Pelvic Measurements of Trial Cows at Second Joining (cm)
| Number | Vertical | Horizontal | |||
|---|---|---|---|---|---|
| Mean | Standard Deviation | Mean | Standard Deviation | ||
| Normal Calf | 22 | 18.16 | 1.1999 | 15.89 | 0.816 |
| Dead Calf | 5 | 18.10 | 1.194 | 16.10 | 0.742 |