Original scientific paper

Seasonal variations in lamb birth weight and mortality

Velimir Sušić ; Department of Animal Husbandry, Faculty of Veterinary Medicine, University of Zagreb, Croatia
Vesna Pavić ; Department for Animal Science, Agriculture Faculty, University of Zagreb, Croatia
Boro Mioč ; Department for Animal Science, Agriculture Faculty, University of Zagreb, Croatia
Igor Štoković ; Department of Animal Husbandry, Faculty of Veterinary Medicine, University of Zagreb, Croatia
Anamaria Ekert Kabalin ; Department of Animal Husbandry, Faculty of Veterinary Medicine, University of Zagreb, Croatia

Abstract

The aim of the study was to determine whether lambs born in different seasons manifest a difference in birth weight and mortality rate. All year-round mating of Merinolandschaf ewes was used based on the natural occurrence of oestrus in different months of the year. The lambing seasons were grouped after birth month of lambs as follows: winter (December-February), spring (March-May), summer (June-August) and autumn (September-November). Data concerning identification number, birth date, type of birth and sex were collected on 401 lambs. Lamb mortality was recorded as number of lambs born dead and lambs born alive but that died within the first 48 hours after birth (perinatal mortality). All lambs were weighed within 12 h after birth, using suspended scales weighing from 0 to 20 kg in minimal 200 g increments. Lambs born in summer had the highest mean birth weight (4.8 kg) which was significantly (P<0.05) different to the lowest mean weight (4.4 kg) observed for lambs born in winter. Similar results were observed within the same sex and birth type group of lambs for male singles among which lambs born in summer were significantly (P<0.05) heavier than those born in winter (5.2 kg vs. 4.7 kg). Prominent but statistically not significant (P>0.05) differences were also observed for birth weight of male twins born in different seasons. Between all female groups (singles and twins), birth weight of lambs born in winter, spring, summer and autumn showed relatively small and not significant differences. Season had a significant (P<0.01) influence on perinatal lamb mortality. Low relative values (1.0 %; 2.0 %) were observed for lambs born in autumn and spring, while during winter and summer, 11.0% and 20.0% of lambs were born dead or died within 48 hours after birth. Within the same season, lambs that remained alive were always heavier than lambs which were born dead or which died after birth. Although the largest difference was observed for birth weights in spring (4.5 kg - alive vs. 3.5 kg - dead), statistically significant (P<0.05) differences were only found within winter births (4.5 kg - alive vs. 4.1 kg - dead) and within summer births (5.0 kg - alive vs. 4.2 kg - dead).

Keywords

season; lamb; birth weight; mortality

Hrčak ID:

31725

URI

https://hrcak.srce.hr/31725

Publication date:

20.10.2005.

Article data in other languages: croatian

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