Losses of sheep following adverse weather after shearing

Deaths due to suspected hypothermia in sheep and alpacas on a Manawatū farm in New Zealand in mid-summer

CASE HISTORY

In mid-summer (February), 42 of a flock of 68 ram hoggets (approximately 5 months of age) and two of a group of 14 alpacas on a farm in the Manawatū region of New Zealand were found recumbent or dead following a period of persistent rain, strong winds and relatively low temperatures. The hoggets and alpacas had been shorn 4 and 53 days previously, respectively, and were in adequate to good body condition with access to ad libitum pasture. Post-mortem and histological examinations were undertaken on four hoggets and two alpacas.

CLINICAL FINDINGS

Apart from hypothermic body temperatures from four recumbent hoggets, nothing of significance was identified on clinical or gross pathological examination. Histological changes of vacuolar hepatopathy, renal tubular degeneration and pulmonary congestion were present in all animals examined.

DIAGNOSIS

Based on the history and clinical and pathological findings, hypothermia was highly probable to have been the cause of the deaths.

CLINICAL RELEVANCE

These cases emphasise the importance of shelter for recently shorn sheep and alpacas regardless of the season.

GPS observation of shelter utilisation by Merino ewes

The present study examined how shelter availability, altitude and temperature influence paddock utilisation by pregnant and lambing Merino ewes. Global positioning systems (GPS) attached to collars allowed continuous tracking of ewes’ positions within two paddocks, and environmental conditions were also monitored throughout this time using temperature loggers. Animal tracking devices (UNEtracker GPS collars) were used in the spring (September–November) of 2008 (51 days) and 2009 (43 days), 14 days post-shearing, to monitor movement of pregnant grazing fine-wool Merino ewes (5 per paddock per year). The data were used to examine sheep use of lone trees, interior shelter, perimeter shelter and remainder of the paddock during three distinct diurnal activity periods, namely night camping, morning grazing and afternoon grazing. Regular use of shelter was consistently recorded in the two experimental years and in both paddocks. The ewes consistently used sheltered areas and both the leeward and windward sides of shelter, particularly during high sheep chill days. The sheep used the sheltered areas significantly more often than they used the remainder of the paddock, which was devoid of shelter except for lone trees. Night camping did not occur at the highest altitude, but predominantly where shelter was also located. The present study has demonstrated the consistent use of shelter by sheep. The shelter-seeking behaviour of the ewes a month post-shearing suggests that these animals are more sensitive to weather conditions than has been previously reported.