early post-natal behaviour in lambs of ten breeds

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  • Applied Animal Behaviour Science, 15 (1986) 229--240 229 Elsevier Science Publishers B.V., Amsterdam --Printed in The Netherlands

    EARLY POST-NATAL BEHAVIOUR IN LAMBS OF TEN BREEDS

    J. SLEE and ANTHEA SPRINGBETT

    A.F.R.C. Animal Breeding Research Organisation, Kings Buildings, West Mains Road, Edinburgh, EH9 3JQ (Gt. Britain)

    (Accepted for publication 25 April 1985)

    ABSTRACT

    Slee, J. and Springbett, A., 1986. Early post-natal behaviour in lambs of ten breeds. Appl. Anita. Behav. Sci., 15: 229--240.

    Activity and sucking behaviour during the first hour after birth, and rectal temperature were recorded in 297 lambs of 10 breeds: Scottish Blackface, Welsh and Cheviot (hill breeds); Oxford, Border Leicester, Southdown, Merino and Finn (lowland); Soay and Boreray Blackface (feral).

    Two components of behaviour were analysed; the time to stand following parturition and the time to reach the udder. There were significant breed differences in both com- ponents. Lambs stood for at least 3 min during the first hour except for about half the Leicesters and most Finns. The feral and hill breeds and the Oxfords reached the udder early; the remaining breeds were slow or unsuccessful. Failure to reach the udder was associated with a higher incidence of hypothermia, especially in Finns and Merinos.

    Weather (combined air temperature and windspeed) was correlated with udder-seeking success but not with the time to stand.

    Within breeds, birthweight affected the times to stand and reach the udder, but litter size did not, except through its effect on birthweight.

    The present results and other data from the same breeds showed that those breeds with effective udder-seeking behaviour also tended to have good resistance to hypothermia and low perinatal mortality.

    INTRODUCTION

    In order to survive, a newborn lamb should stand, suck from its mother and establish a bond with her as soon as possible after birth. The maintenance of a normal body temperature is also necessary if the lamb is to be mobile (Slee, 1977) and find the udder and suck {Alexander and Williams, 1966a, b). The ability to withstand cold-exposure, as well as being necessary to avoid lethal hypothermia, may also be important in establishing a secure maternal bond with adequate suckling. If exposure to cold disrupts the behaviour patterns necessary to ensure suckling, as reported by Alexander and Williams (1966a, b), then energy reserves, being depleted by the demand for increased heat production, will not be replenished and the lamb will

    0168-1591/86/$03.50 1986 Elsevier Science Publishers B.V.

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    die from cold and starvation (Slee, 1979, 1981). The cold/starvation syndrome is frequently the major cause of early post-natal lamb mortality (Houston and Maddox, 1974).

    Previous work showed that lambs of different breeds varied significantly in their ability to resist hypothermia and in their field mortality rates in the same location (Sykes et al., 1976; Slee et al., 1980). The present work involved detailed observations on the neonatal behaviour of lambs of the same breeds born under similar conditions at the same location. The breeds differed in the following respects: (i) the environments to which they were previously adapted; (ii) their natural lamb mortality rates; (iii) their suscep- tibility to hypothermia; (iv) physical characteristics such as birthweight, coat type and litter size.

    The breeds could be broadly classified as: commercial hill sheep, lowland sheep (both large and small) and feral sheep. Comparisons between these main types, which would presumably have been subjected to different selection pressures for lamb viability, could be valuable in identifying genetic variation in components of behaviour relevant to survival. For example, the two feral breeds (taken from St. Kilda where there is a high lamb mor. tality rate, Jewell et al., 1974) would have been adapted to a situation of severe climatic and nutritional stress. Lowland commercial sheep, with the advantages of shelter, shepherding and adequate nutrition, would have been subjected to different types of selection.

    The behavioural observations covered the first hour after birth, during which time most lambs stand and begin to suck (Alexander, 1958; Bareham, 1976). The events observed included activity immediately after birth, dam-directed behaviour and sucking behaviour, and were similar to those described by Bareham (1976) in Clun Forest and Suffolk cross lambs born indoors. Lamb body temperatures and prevailing weather conditions were also recorded, so that interactions between breeds, weather severity, sus- ceptibility to hypothermia and early behaviour could be considered. This investigation was expected to indicate which aspects of early neonatal behaviour might be important components of survival.

    MATERIALS AND METHODS

    Observations were carried out on an Animal Breeding Research Organisa- tion (ABRO) lowland farm at the Dryden Laboratory, Roslin, Midlothian, between 1975 and 1978. During those years, 860 ewes of 10 breeds lambed. Scottish Blackface (202); South Country Cheviot (81); Welsh Mountain (117); Oxford Down (38); Border Leicester (50); Southdown (57); Finnish Landrace (94); Tasmanian Merinos (87); Soay (109); Boreray Blackface (25).

    The sheep were bred at Dryden but derived originally from different sources. The Scottish Blackface and Welsh Mountain breeds were from

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    A.B.R.O. hill farms in Tweeddale and in North Wales, respectively, the Cheviots and Border Leicesters were from the South of Scotland, the Oxfords from an A.B.R.O. lowland farm in Staffordshire, the Southdowns from the South of England, and the Finnish Landrace from an A.B.R.O. upland farm in Tweeddale. The Boreray Blackfaces and Soays were im- ported by A.B.R.O. in 1966 and 1970, respectively, from feral sheep popula- tions on the island of St. Kilda, 100 miles off the west coast of the Scottish mainland, and the Tasmanian Finewool Merinos were imported by A.B.R.O. from Australia in 1956.

    Lambing usually began in January or February and continued until May or June. The ewes lambed under natural conditions in either a 0.2-ha pad- dock containing up to 8 sheep, or a 1.2-ha field containing up to 30 sheep. Observations were conducted outdoors from 08.30 until 18.30 on week- days, if daylight permitted, and from 09.30 until 16.30 at weekends. The sheep were viewed from nearby laboratory windows or from inside a caravan. Births which occurred overnight or which were not actually observed were excluded, and so were observations where there was any disturbance or interference. This procedure resulted in acceptable observations on 297 lambs (see Table I).

    TABLE I

    Lambs observed over 4 years with average littersize and birthweight

    Breed Breed No. of lambs Mean Range Mean type litter-size birthweight (kg)

    S. Blackface Hill 69 1.4 (1--2) 3.6 Welsh 63 1.7 (1--3) 2.8 Cheviot 20 1.4 (1--3) 3.7

    Soay Feral 28 1.4 (1--2) 1.8 Boreray 9 1.1 {1--2) 2.5

    Oxford Lowland 13 1.3 (1--2) 5.9 B. Leicester 24 1.8 (1--4) 4.3 Southdown 22 1.4 (1--2) 3.5 Merino 16 1.1 (1--2) 3.5 Finn 33 2.5 (1--4) 2.3

    Total 297

    The following observations were made on the lambs and were timed from the completion of the birth process: first shaking of head; first attempt to rise on knees; first attempt to rise on feet; standing for 1 min; standing for 3 min; nudging along the flanks of the ewe; nudging the ewe in the udder region; lamb first at the udder; apparent sucking.

    Observations generally continued for 1 h after birth, or until the lamb sucked, whichever occurred first.

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    Observations on lambs which did not suck within 1 h were therefore truncated. In addition, lambs which lay immobile for more than 25 min in cold weather were considered to be in danger of hypothermia and un- likely to suck. They were removed and brought indoors. Incomplete obser- vations thus arose from 1-h truncation or early removal.

    Lamb rectal temperatures were measured after 1 h when observations were completed, or when suspected hypothermic lambs were removed and brought indoors. The latter were measured at the time of removal (usually between 30 and 50 min after birth). Sykes et al. (1976) showed that the rectal temperatures of lambs in the field change little between 20 min and 1 h after birth, so the measurements should be comparable. Measure- ments were obtained from a thermoelectric dial thermometer (Light Lab- oratories) with a thermistor probe inserted 6 cm (Sykes et al., 1976). The weather was also recorded as follows: air (shade) temperature; wind speed (from a cup anemometer placed 25 cm above the ground); sun (presence/ absence); rain (absent, moderate or heavy). In the data analysis, weather conditions were represented by an index of the cooling power of the en- vironment, derived from the air temperature (C) and the wind speed, according to tables published by Burton and Edholm (1955). The index was calculated by reducing the measured air temperature by 2--16C for wind speeds varying from 0.2 to 6.7 m s -1. This index was termed "effective ambient temperature" (EAT). Temperature and air movement were likely to be the most important components affecting the cooling power of the environment upon a newborn lamb already soaked by amniotic fluids. The relationship between EAT and the cooling power of the environment was tested by reference to a simple artificial lamb constructed from a 12 X 21 23-cm tin box containing a 60 W light bulb as a heat source and a thermostat, lined with 1-cm thick polystyrene and covered by a lamb's skin. The ther- mostat was set to maintain the surface of the box at 30C (a typical skin temperature) and was connected to an electric meter and power supply. When t