VN May 2017

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Lamb mortalities (Part 1) Dr. Chantelle Erwee, Zoetis South Africa (Pty) Ltd, Technical Manager: Ruminants

Introduction W e all love the arrival of newborn lambs. In the same breath, few things are more frustrating and distressing than lambs dying for no obvious reason. Lamb mortality remains a huge economic concern to both intensive and extensive sheep farming systems, but some consideration also needs to be given to the welfare side of the issue, affecting both the ewe and the lamb. (1,2,3) As with most aspects of farming, there is no ‘one recipe’ that works on each and every farm, however, this article series will aim to serve as a brief summary and refresher which will touch on some of the most important aspects affecting lamb survival. (1) The management and farming strategies that influence lamb survival should start long before the birth of the lambs. (3) The advantages of an increase in the number of lambs born will be outweighed by the disadvantages of losing those lambs due to decreased survival. (1) Most lamb losses occur during the first week of the lamb’s life, with nearly half of these deaths occurring on the day of birth. (1,2,3) The afore- mentioned highlights the importance

in other words, a higher surface area to volume ratio. (3) Heat loss is influenced mainly by surface area whereas heat production is more related to body weight. (3) Due to their relative larger surface area, smaller lambs will lose more heat to the environment, placing them at greater risk of developing hypothermia than larger lambs. (1,2,3) At birth, the ewe’s protected uterine environment is replaced with an external environment full of challenges which can include cold or wet weather and, most likely, predators.(1) After birth, the lamb’s core temperature drops by approximately 1 to 2 °C from the warm uterine environment of 39 °C. (3) To counteract and

of the post-partum period to the lamb’s survival. (3) The several causes and aspects that can lead to neonatal lamb mortality differ according to the management system. (1,2) Extensive sheep farming systems will more likely lose lambs from dystocia, starvation or exposure, whereas, the intensive systems will be faced more with threats of infectious diseases and parasites. (1,2,3) Lamb birth weight, colostrum intake and hypothermia Lamb birth weight is a major risk factor in lamb mortality. (1,2) An intermediate birth weight within the breed is optimal, with increased mortalities seen at both high and low birth weights. (1,3) Large lambs might be predisposed

to birthing difficulties,

whereas small lambs may be more inclined to die from starvation and exposure. (3) Lambs with low birth weights have a high birth coat/birth weight ratio or

32 Mei/May 2017