The 2017-2019 drought caused many challenges and nutrition-related issues in all classes of livestock. The following case was investigated over a two-year period and highlights the importance of species-specific diet formulation and delivery. This case emphasises the difference between sheep and goats and the absence of available literature and information on goat health and nutrition.
Contact was made in August 2019 by a goat producer, located approximately 80km north west of Dubbo, who was experiencing abortions in his commercial boer goat herd for the second consecutive year. The previous year there had been abortions and stillbirths, predominantly in maiden does. In 2019, the abortions were occurring in does from all mobs and age groups. At this time the does were run in several large mobs that had mixed age, body condition, parity and litter size. The farm was experiencing its third consecutive year of drought and as such the goats were being fed a complete ration. As with many properties in their third year of drought, there was minimal ground cover and no paddock feed available.
The goats were fed 700g of barley/hd/day delivered via trail feeding between weaning and joining, which was increased to 1kg barley/hd/day just prior to joining. Feed was again increased to 1.2kg barley/hd/day just after scanning and approximately one month out from kidding an additional 350g/hd/day of field peas were added. Throughout this time wheaten hay was provided as a roughage source.
The initial foetuses examined were estimated to be approximately 80 days gestation based on foetal size and lack of hair follicle development.
Over the course of kidding, approximately 15 dead kids were presented, ranging from mid-gestation abortions (see figure 1), to kids which had died within 48 hours of birth. Post-mortems were unremarkable.
The herd was inspected, and all does were estimated to be in BCS 2.5-3/5. Blood was collected from four does that had recently aborted, including one which had aborted in the previous 48 hours. Clinical examination of these does was normal and mild perineal staining was identified.
Infectious causes including Pestivirus, Campylobacter, Coxiella, Toxoplasma and Chlamydia were considered unlikely as abortions were occurring in every age group for two consecutive years. These aetiologies were subsequently ruled out through laboratory testing. Foetal copper levels and foetal GSH PX were also normal.
Vitamin A deficiency was also investigated as it had caused abortions and stillbirths in cattle within the region. Kids born with low vitamin A levels rely on colostrum to provide the initial source of vitamin A. Vitamin A & E levels in does were measured in both 2018 and 2019 with several animals returning low Vitamin A results. A comparison of liver Vitamin A levels from kids that had and had not fed was also used to test the theory that vitamin A deficiency was contributing to the losses. Table 1 shows that vitamin A levels of both the fed and unfed kids were well below the reference range. As there are no Vitamin A reference ranges for goats (neonatal or otherwise), sheep reference ranges were used. Based on liver samples and history it was assumed that hypovitaminosis A was contributing to the clinical presentation.
Table 1: Foetal Vitamin A & E results
|Neonate||Liver Vitamin A (mg/kg)||Liver Vitamin E (mg/kg)|
|Sheep Reference range||>100mg/kg ww||>1.5mg/kg ww|
|Not fed (<24hr old)||5.6||1.6|
|Not fed (<24hr old)||2.1||4.0|
|Fed (1 week old)||9.9||6.5|
|Fed (5 days old)||1.2||3.9|
Extensive laboratory testing failed to identify a probable infectious cause of the losses and therefore non-infectious causes such as nutritional deficiencies were considered. After consultation with experts in this field, it was identified that the ration the goats were receiving was deficient in both the energy and protein and failed to meet the nutritional requirements of gestating does. As such inadequate nutritional abortion was identified as the most likely cause of abortion with hypovitaminosis A contributing to the losses.
There were several factors relating specifically to goats that were identified as likely contributing to this clinical presentation, including:
Goats have a unique ability to terminate pregnancy when nutrition is inadequate. To better understand this mechanism it is useful to review maintenance of pregnancy in goats. The production of progesterone signals for the maintenance of pregnancy and in goats the corpus luteum is the only source of progesterone for the duration of gestation. With inadequate nutrition the corpus luteum involutes and the pregnancy terminates. The mechanism of pregnancy termination in goats is not well understood.5 Nutritional requirements from 90 days pregnancy to birth are the most critical and are roughly outlined in table 2.
Table 2: Energy requirements of pregnant goat1,7
|Days gestation||Daily energy requirement|
|Dry 50kg goat||7.5MJME/kgDM7|
|90-110 days||1.4 x Maintenance + activity|
|110-140 days||2 x Maintenance + activity|
|140-150 days||2.5 x maintenance|
As a result of the above, the following management changes were recommended:
In 2020, after an exceptional season and copious amounts of green feed, the farm did not experience any kidding issues.