Time pattern and causes of lamb mortality on commercial sheep farms in Southern Germany operating conservation grazing and non-seasonal production systems – a field study

Abstract

Benchmarking is becoming increasingly important in sheep farming and little published data has so far been available for German sheep flocks. This field study was conducted to gather detailed information on lamb mortality on 17 large commercial sheep farms operating non-seasonal production systems in Southern Germany thus providing benchmarking data for this management system for the first time. During a twelve-month-period detailed lambing and mortality records were kept and suspected causes of death were noted by the farmers. Farm management data were obtained by questionnaire and statistical analyses were performed to identify potential influences on lamb mortality. A total of 14,918 lambs were born at term during the study period (13,751 alive and 1,167 stillborn). Abortion events were also noted, but insufficient records were kept on the number of aborted fetuses – these figures therefore only refer to lambs born at term. The mean stillbirth rate was 7.7% (range: 2.7–16.3%, median 7.2%, SD 3.6) while the average mortality of live-born lambs was 13.4% (range: 0.8–40.1%, median 11%, SD 9.8), leading to average total lamb losses of 20.1% (range 6.5–44.9%, median 17.7%, SD: 10.1). Perinatal deaths (stillbirth and lambs that died on their first day of life) accounted for an average of 52% of these total lamb losses (range: 33−89%, median 46%, SD: 16). Stillbirth was the predominant cause of lamb loss accounting for an average of 45% of deaths (range: 15−84%, median: 37%, SD: 18). Other suspected causes of death included infectious diseases (13%), maternal factors (8%), weakness (7%), accidents/external circumstances (4%), Schmallenberg Virus−related malformations (2%), parasites (2%), nutritional causes (2%) and other individual (1%) or unknown causes (16%). For our study population, farmer education was identified as a statistically significant factor related to a lower stillbirth rate. Fixed lambing times as opposed to year-round lambing showed a tendency to be associated with increased lamb survival, as did vaccination of the ewes against clostridial diseases and pasteurellosis. Multiples showed significantly higher peri- and neonatal mortality, while mortality of single lambs was significantly higher later in the rearing period. No statistically significant differences in lamb mortality could be shown for indoor versus outdoor lambing or other management factors. This study generated benchmarking data for flocks used in conservation grazing and non-seasonal production. The analysis of lambing data also proved very helpful on each individual farm to develop tailor-made flock health programmes and to identify farm-specific problems, particularly on farms with high mortality rates.