Field techniques to increase lamb survival.

Abstract

FIELD TECHNIQUES TO INCREASE LAMB SURVIVAL A. R. BEGGS* and E. J. CAMPION Summary Observations over a 20 year period in an autumn lambing (March) Saxon Merino flock have shown a consistent rise in the lamb marking percentages from the low 70's to almost 100% concurrent with changes in technique at lambing. The techniques described and discussed are: (i) intensive paddock husbandry, (ii) 'drift' lambing in small paddocks, (iii) pen, or fold, lambing. I. INTRODUCTION Alexander ( 1964) stressed the importance of three factors influencing the survival of the newborn lamb:(i) Warmth and food (ii) The lamb 's energy balance (iii) The behaviour of ewe and lamb. Since disease is rarely a major factor (Hughes et ~11. 1964)) Alexander concluded that lamb survival depends largely on the standard of animal husbandry practised in relation to the severity of nutritional and climatic stresses imposed by a particular environment. The purpose of this paper is to describe a successful system of lambing husbandry developed for a Merino commercial and stud flock in the Western District of Victoria. This system was developed between 1945 and 1965 in order to obtain a consistently high lamb marking percentage. II. MATERIAL AND METHODS (a) Environment ( i) Location These observations were recorded on the property 'Buln Gherin', eight miles south of Beaufort and approximately 100 miles west of Melbourne. (ii) Climate and Physical Features The annual rainfall is 24 inches (60 cm), more than two inches of rain during lambing conditions for lamb survival are excellent at this ture is over 100�F (38�C) occasionally, cold, extremely rare. Winds at this time of the year warm. but the probability of receiving (March-April) is low. Weather time and although the temperawet and windy conditions are vary in intensity but are usually 3 'Buln Gherin', Beauf ort , Victoria. j-Marcus Oldham Farm, Agricultural College, P.B., Geelong, Victoria. 169 Rain too is warm, heavy and of short duration. The area consists of open basaltic plains with few trees and some shelter is provided by stony outcrops. The 'drift lambing' area is surrounded by scattered plantations and has a slight northern aspect. (iii) Pasture an<d Stocking Rates Throughout the period under discussion, soil fertility has been rising due to pasture improvement with annual clovers and perennial grasses. The stocking rate per acre has risen from 4 dry sheep equivalents in 1921 to about 5 in 1965. (iv) Lambing Pens The pens used in Periods 4 (maiden ewes) and 5 (see below) were 4 ft (1.3 m) long by 3 ft (lm) wide by 3 ft (1 m) high, and were made of 3/4 inch ( 1.9 cm) pipe and 3 inch (7.5 cm) mesh. Tins of water were provided in all pens and hay for feed, and bedding was changed daily. The first 40 pens were not roofed and were situated adjacent to the sheep yards; hesian covering was used to prevent heat stress and a wall of pressed hay reduced wind. The 36 pens added in Period 5 were on a concrete floor and covered by a skillion roof off an existing shed. All pens were completely movable and were used for lamb marking and drenching at different sites. (b) Joining crnd Lambling The sheep were fine-woolled Saxon Merinos of the Eurambeen strain which has been autumn lambed since 1856. The commencement of lambing in all years discussed was March 10. Ewes were first joined at 2% years of age and culled at 53 years. Two per cent of 'Buln Gherin' stud rams were used. Adequate nutrition was given to all ewes approaching lambing, and oats grain and/or pasture hay was fed when the season was unfavourable. Sheep dogs were not used with any of the drift lambing systems. Since 1958, foxes have been poisoned prior to lambing. Certain features of husbandry have been modified between 1945 and 1965 (Table 1). Brief descriptions of the five lambing systems are given. (i) Period I, 1945-53 Ewes were set stocked at 0.75 per acre and inspected once daily during lambing. (ii) Period 2, 1954 The lambing ewes were inspected twice daily. (iii) Period 3, 1955-58 The normal set stocking was used until late January when supplementary oats were fed if needed and this assisted in training ewes for the drift. In order to reduce flock size in the drift the ewes were visually classed, on fullness of udder as well as size and colour of vulva, into three lambing groups-forwar d (the first to lamb) ; midseason (in lamb but not as full in the udder and with normal vulvas) ; late or dry (not showing signs of being in lamb). Midseason and late or dry groups were left in outer paddocks with minimal supervision. A TABLE 1 Periods, years and husbandry systems few lambs were born in these groups but as the classing was done during the week before the first lamb was due, most of the early lambing ewes were in the forward group. At the commencement of lambing, the forward group entered the first 10-l 5 acre drift paddock of saved phalaris and subterranean clover pasture. In the drifting sequence, the unlambed ewes were moved to the second paddock at 7.30 a.m. daily, leaving the lambed ewes behind. The ewes that lambed on the first day were moved out of the drift on the fourth evening to make room for unlambed ewes commencing their second drifting cycle. Lambed ewes were held in a large enough to set-stock an outer that stock water was located close losses occurred in the first years of half a mile to water. neighbouring paddock until a flock, estimated paddock, was formed. It was most important to the exit from the drift area, as many lamb this system due to the ewes having to travel As the forward group 's numbers were depleted, the midseason (and subsequently the late) flocks were added to the drift. (iv) Period 4, 1959-64 The aged ewes were lambed in a seven paddock (8-10 acres) drift which generally resembled the four paddock described in Period 3. Half the paddocks were cut and pressed into round bales left in the paddock each spring so as to avoid annual hay cutting in the same paddocks. This `provided supplement at least every second day to circulating ewes. Shelter for lambs in inclement weather was never more than one paddock away. Ewes with twin lambs were separated on the fifth day post partum and given preferential feeding. Maiden ewes (3 years old) were lambed in the 40 pens described above. Immediately before lambing was due to commence the maiden ewes were drafted into the three groups forward, midseason and Late as described in Period 3. The forward ewes were kept close to the main sheep yards during the day, and during daylight any ewes on the point of lambing were drifted up to the pens to lamb. Each evening (4.30 p.m.), the unlambed ewes were classified as either imminent or not imminent. The examination was visual and physical as follows: Udder. Ewes close to lambing have full and firm udders. It was always necessary to feel an udder physically as some udders develop anteriorly and cannot be assessed visually. VuZva becomes relaxed and usually darkens as lambing approaches. Pelvis relaxes seen by the dropping of the ischium prior to lambing. The 40 most imminent ewes were placed in their individual pens overnight and any unlambed at 7.30 a.m. were returned to the main group. Every maiden ewe capable of feeding a lamb was forced, either in the pens (often with the use of plaited twine halters to prevent butting) or in small ( 4 Et 6 in i.e. 1.5 m) circles of mesh, to take a lamb. Maidens having a dead lamb had a lamb fostered on to them by placing the skin of their own dead lamb over the foster lamb. 172 Ewes with twins were kept separate on leaving the pens and subsequently received preferential grazing. The men working in the drift with the aged ewes assisted in cleaning pens and in choosing the next batch of maidens to lamb. (v) Period 5, I965 All ewes were lambed by the methods described for maiden ewes in Period 4. With the addition of 36 pens, all ages of ewes were mixed during the initial sorting into forward, midseason and late groups. During the peak of lambing, 110 to 150 ewes lambed per day and nearly half of these during daylight hours, so that the 76 pens were just sufficient to cope. Ewes with twin lambs were separated and given preferential grazing. Lambed ewes, once they were successfully mothering their lambs, were gradually drifted out to the outer paddocks and set-stocked until weaning. III. RESULTS Figure 1 shows the lamb marking percentages obtained in each Period, and Table 2 gives the lambing results for the years 1960 to 1965. Table 3 summarises the labour inputs at lambing for each period, highlighting the fact that man hours spent at lambing show little relationship to the lambing percentage or to the total number of lambs being reared to an economic age, i.e. first shearing. The total number of ewes being handled shows a steady rise throughout successive periods. About 90% success has been achieved with the methods of fostering described for maiden ewes in Period 4 but failures occurred when the ewe had no visible sign of milk or became too distressed to lactate. 173 TABLE 2 Analysis of lambing performance from 1960 to 1965 'Percentages calculated on base of number of ewes mated. +Percentage of total lamb deaths. TABLE 3 Analysis of man hours at lambing *Figure not yet available (estimate 2,300). IV. DISCUSSION A series of husbandry systems has been described and their results indicated but, as no control flock has been kept, it is not possible to assess how much they contributed to the increased lamb survival. The systems were develope d because it was felt that the extensive system was inefficient and, to be effective, traditional patterns had to be broken. A great deal of attention has been paid to maternal behaviour of the ewes, particularly of ewes with twin lambs, because ewes becoming separated (mismothered) from one of a set of twins appeared to be a major contribution to the deaths in lambs. The all-pen lambing system has been developed because mismothering became a problem in the drift system when large numbers of lambs were born in a small area. It is now necessary to perfect the technique of getting ewes with lambs gradually away from the lambing pens to the outer paddocks. The pens have been successful in preventing mismothering of lambs at the time of birth and in assisting ewes with dystocia and subsequent mothering. They have also proved helpful in allowing ewes to become used to mothering twin lambs and preventing unlambed ewes (particularly maidens) from pirating one of a set of twins. Lambing at 'Buln Gherin ' is now of shorter duration, 5 weeks instead of 12 weeks, and has become a labour demand job roughly equivalent to shearing. Much of the men' time in the early periods was taken up with travelling around s the property and very little effective effort was contributed to lamb survival. V. REFERENCES AL EXANDER, G.(1964) . Lamb survival: Ph ysiological considerations. Proceedings of the Australian Society of Animal Production 5: 113. H UGHES , K. L., H ARTLEY , W. J., H AUGHEY , K. C., and MCFARLANE, D. (1964). A study of perinatal mortality of lambs from Oberon, Orange and Monaro districts of New South Wales. Proceedings of the Australian Society of Animal Production 5: 92. 176