Ewes Ha-1 Research Articles

Effect of stocking rate, time of lambing and inclusion of lucerne on prime lamb production in north-east Victoria

Results of a grazing study involving Border Leicester x Merino ewes and their progeny are reported for a 4-year period 1969 to 1972. The study was conducted at Rutherglen in north-east Victoria. The 1260 ewes observed throughout the study were allotted to 42 treatment plots with 30 ewes per plot. Thirty of the plots were located on annual pasture (subterranean clover, barley grass) involving three replicates of ewes stocked at 7.4,9.9 and 12.4 ewes ha-l for ewes joined over 7-week periods to commence lambing about May 5, June 23 or August 8. Additionally, an extra three plots with spring lambing were grazed at 14.8 ewes ha-1. A further 12 plots contained lucerne on one third of the plot area. The ewes on these plots also lambed for a 7-week period commencing August 8, and provided three replicates of 7.4 9.9, 12.4 and 14.8 ewes ha-1. First services were concentrated early in the joining period in the spring-lambing ewes, there were few returns to services and few ewes failed to mate. On the other hand, among ewes joined to lamb in autumn, first services were distributed over the entire joining period, and many ewes returned to service or failed to mate. The mating pattern of ewes joined to lamb in winter were intermediate between the autumn and spring lambing groups. Although the liveweight of spring-lambing ewes was lighter at mating, the number of lambs born per 100 ewes joined was greater than for winter lambing, and these in turn were greater than for autumn lambing ewes. The response to an additional 1 kg liveweight at mating was 1.7, 2.0 and 2.8 additional lambs born per 100 ewes joined for autumn, winter and spring lambing, respectively. Wool production per hectare increased linearly with increase in stocking rate; it was marginally affected by time of lambing and was greatest where lucerne was provided. The number of lambs reared per ha increased linearly with increase in stocking rate, albeit there was some decline in carcase weight and a small decline in numbers of lambs reared per ewe. Lambs born in autumn and winter were generally slaughtered in prime condition at 31 kg liveweight, except in the drought year of 1972, but more lambs were produced from a winter lambing than from autumn lambing. When lambing was in August-September there was a slight increase in the numbers of lambs reared above that of winter lambing, but the proportion of lambs marketed at less than 31 kg was greatly increased. Where lucerne was provided to spring-lambing ewes the greatest weight of meat per hectare was produced, and few lambs were less than 31 kg. In descending order of magnitude, the major factors affecting carrying capacity were season, year, stocking rate and time of lambing. Seasonal shortcomings in nutrition were alleviated by the provision of supplementary feed. At the lighter stocking rates of 7.4 and 9.9 ewes ha-1 the amounts of supplements fed were very low, even in the drought year of 1972. These two lowest stocking rates could be maintained indefinitely without excessive use of supplementary feed. Discernible changes in botanical composition with partial loss of productive grass and clover species, reduction in pasture growth rate, increased use of supplementary feed and lowered wool production of ewes, occurred with spring lambing without lucerne, particularly at 12.4 and 14.8 ewes ha-1. Pasture composition and growth details were very similar with either autumn or winter lambing.

Sheep production on the north coast of New South Wales. 2. A feasibility study of prime lamb production

Lamb production was studied in an experiment that ran for four years, 1968 to 1972, at Grafton, New South Wales, in a region where no commercial sheep are grown. Merino and Dorset Horn x Merino ewes stocked at 15 ewes ha-1 were mated in spring to Border Leicester rams and the lambs sold for slaughter in October. The mean number of lambs born per 100 ewes mated was 81.7 for crossbred ewes and 48.4 for Merino ewes (P< 0.05) and the mean carcase weights of the lambs were 14.8 kg and 12.7 kg, respectively (P< 0.01). The mean weight of fleeces cut from Merino ewes (3.24 kg) was greater (P< 0.01) than that from crossbred ewes (2.58 kg). The ewes were treated with anthelmintics either every four weeks or according to climatic conditions. There were no significant differences between the anthelmintic treatments for lamb liveweights at birth, weaning or slaughter; carcase weight; ewe fleece weight; or mortality rate. Treatment every four weeks increased ewe live weight during only one short period from August 1971 to February 1972 (P< 0.05). Data from this experiment compared favourably with survey data for the high rainfall zone in Australia and it was concluded that prime lamb production on the north coast of New South Wales is biologically feasible.

The effects of phosphorus, sulphur and stocking rate on the yield, chemical and botanical composition of natural pastures, North-West Slopes, New South Wales

The effects of phosphorus (P), sulphur (S) and stocking rate on the dry matter yield, and chemical and botanical composition of natural pasture were examined from November, 1971 to May, 1976 in a 20 point central composite design. P and S were applied annually at five levels (0, 6, 15, 23, 29 kg P ha-1; 0, 14, 34, 54, 67 kg S ha-1) and the plots were grazed continuously at five stocking rates (2.2, 3.2, 4.8, 6.3, 7.3 dry ewes ha-1). Each of the factors, P, S, and stocking rate affected total dry matter. At 4.8 and 6.3 sheep ha-1 the optimum rate of P was 15 kg ha-1, but at 3.2 sheep ha-1 it increased from 15 kg ha-1 to 23 kg ha-1 over the period. S had little effect on yield at the start and end of the experiment, but in between its effect depending on stocking rate; at 3.2 sheep ha-1 low levels (<I4 kg ha-1) were optimal, but at 4.8 and 6.3 sheep ha-1 very high levels (>54 kg ha-1) were needed. The quantity of green grass and legume was low in winter and was not consistently affected by any of the factors. The level of N in the green grass remained at less than 2%. Over the period of the experiment the basal cover of perennial grass and the frequency of annual legume declined, while the percentage of bare ground and annual grass increased. These changes over time could not be related to any of the factors, except that the percentage of A. ramosa declined at the higher stocking rates. In some years high stocking rate decreased the percentage of A. ramosa and S. variabilis, and increased that of C. truncata, D. linkii, K. phleoides and T. glomeratum. In terms of pasture yield, fertilized perennial grass pastures on the North-West Slopes have potential carrying capacities of at least 4.8 dry sheep ha-1. However, to support this high stocking rate without significantly affecting pasture yield high levels of S, around 54 kg ha-1, and moderate levels of P, around 15 kg ha-1, are required. At this higher stocking rate no major changes in botanical composition occurred.

An economic analysis of a 10 year rate of stocking trial with fine-wool

Merino ewes were grazed for 10 years at stocking rates of 8, 12 and 16 ha-1, lambing in winter, spring or summer on a phalaris/white clover pasture on the Northern Tablelands of New South Wales. Wool production, wool yield and count, and lambing and weaning rates were established for the wide range of climatic conditions experienced. A spring lambing is indicated under the within-year price relationships experienced. Under a wide range of wool and lamb prices the optimum stocking rate varied from 12 to 16 ewes ha-1 depending on labour costs.

Stocking rate, joining time, fodder conservation and the productivity of Merino ewes. 1. Liveweights, joining and lambs born

In an experiment at Hamilton in western Victoria, groups of 30 Merino ewes born in 1967 were stocked at 11.7, 15.4 or 19.2 ewes ha-1 and joined to Merino rams each year on April 5 or May 8 for five weeks. Hay was conserved on half the number of plots and fed back to the ewes at joining. Observations at mating and lambing in each year from 1970 - 73 are presented. Seasonal conditions exerted a greater effect upon liveweight change before joining than did the applied treatments but liveweight at joining declined significantly as stocking rate increased. Oestrus activity and the number of ewes returning to service were similar on all treatments. Both the number of lambs and the proportion of twin births declined linearly as stocking rate increased. It is concluded that a similar relationship between liveweight and ovulation rate existed on all treatments. Withholding the introduction of rams from April until May did not result in any change in the number of lambs born. Hay feeding failed to increase the number of lambs born. It is suggested that the ewes substituted hay for pasture.

A comparison of continuous grazing and deferred autumn grazing of Merino ewes and lambs at 13 stocking rates

The performance of Merino ewes and their lambs was measured when the sheep were either continuously grazed or autumn-deferred on annual pastures. The two management systems were compared at a series of 13 stocking rates from 4.9 to 19.8 ewes ha-1 for 5 years from 1970 to 1974 at the Kybybolite Research Centre, South Australia. The deferred sheep were fed in yards on a mixture of oat grain and hay at 6.8 kg per head per week during the 6-week deferment period. It was found that the continuously grazed ewes required very little hand-feeding up to a stocking rate of 17.3 ewes ha-1. Grazing management had little or no effect on wool production in ewes or lambs, on the number of lambs born and weaned, or on lamb growth rates. Although the incidence of pregnancy toxaemia was very low (1%) it was higher in the deferred treatments. Autumn deferment resulted in extra pasture during the winter months of June and July. However, the continuously grazed pastures reached the same level of availability as the deferred pastures in late winter and early spring. Total yearly pasture production tended to be greater on the continuously grazed pastures and increased as the stocking rate increased. It is concluded that there is little merit in adopting an autumn deferment system of grazing management for Merino ewes and lambs. A relationship between lamb growth rate and both available pasture and pasture height is presented. It would appear that pasture height measurements are no better predictors of Iamb growth rates than pasture yield measurements.

Stocking rate, joining time, fodder conservation and productivity of Merino ewes. 2. Birth weight, survival and growth of lambs

In an experiment at Hamilton in western Victoria, groups of 30 Merino ewes were stocked at 11.7, 15.4 or 19.2 ewes ha-1 and joined to Merino rams each year on April 5 or May 8 for five weeks. Hay was conserved on half the number of plots and fed back to the ewes before and during joining. Observations on birth weight, survival, and growth of lambs born between 1970-73 are presented. Both the highest stocking rate and the earlier lambing were associated with a depression of about 7 per cent in the birth weight of twin lambs, but single lambs had similar birth weights on all treatments. Lamb survival was highly variable and there were few significant treatment effects. However, mortalities within 48 hours of birth were lower amongst flocks joined to lamb in October than those lambing in September (single lambs 9.2 per cent vs. 14.7 per cent-twin lambs 19.9 per cent vs. 40.2 per cent). Most of the improvement was attributed to drier conditions and lower windspeeds in October. Lamb growth rates fell with increasing stocking rate but the variation in weaning weight was less than 2 kg. Lambs born in September were about 10 per cent heavier at weaning than those born in October. Compensatory growth after weaning resulted in negligible differences in weight at 12 months between lambs from the different stocking rate treatments, but lambs born in September were still significantly heavier than those born in October.

Effect of management system and stocking rate on the performance of ewes and lambs

A grazing experiment was conducted at Cowra, on the western slopes of New South Wales, on a pasture consisting of lucerne (Medicago sativa) and annual species including capeweed (Arctotheca calendula), barley grass (Hordeum leporinum). wimmera ryegrass (Lolium rigidum) and subterranean clover (Trifolium subterraneum) . The performance of Border Leicesterx Merino ewes mated to Dorset Horn rams and the growth of their progeny was compared under rotational and set stocked grazing management systems, with and without a 20 per cent area of lucerne saved for grazing when additional feed was required. There was one stocking rate (8.7 ewes ha-1) in 1966 and two (8.7 ewes ha-1 and 13.0 ewes ha-1) in 1967 to 1969. Rotational grazing decreased the lamb growth rate but increased the number of lambs born. The management system did not affect the body weight or wool production of the ewes. Lucerne was quickly eliminated from the set stocked areas and was greatly reduced in the rotational systems. Capeweed became dominant in the set stocked areas. Saving increased the number of lambs born at the high stocking rate in 1967 to 1969. In 1966 saving reduced lamb growth, ewe body weight and wool growth in the rotational system. The high stocking rate increased wool production per hectare, but decreased the number of lambs born and, in 1967, the lamb growth rate.

Effect of time of joining and rate of stocking on the production of Corriedale ewes in southern Victoria. 5. Ovulation rate and embryonic survival

In the final five months of an experiment which had lasted from November 1967 to June 1971 a study was made of the ovulation rate and embryonic survival in a flock of 540 five-year-old Corriedale ewes grazing annual pasture in southern Victoria. Ewes were stocked at 5, 7 1/2 or 10 ewes ha-1, and were joined with rams for six weeks beginning at either February 8 or April 19, 1971. A comparison with actual lambing data in 1970 was made. Ewes stocked at 5 ewes ha-1 had a higher ovulation rate and estimated lambing rate (based on embryos surviving to day 28) than those stocked at 7 1/2 or 10 ewes ha-1. Ovulation rate was higher for ewes of high liveweight than for ewes of low liveweight among those stocked at 7 1/2 and 10 ewes ha-' but not among those stocked at 5 ewes ha-1. Ewes joined in April had a higher ovulation rate and estimated lambing rate than ewes joined in February. There was no significant interaction between joining time and stocking rate on estimated lambing rate which was in contrast to the previous year 1970, when increased stocking rate reduced the number of lambs born per ewe from the February joining. Embryonic survival was greater among ewes joined in February and stocked at 7 1/2 ewes ha-1. There was no difference between stocking rates in embryonic survival among ewes joined in April. There was a trend for fewer twin ova to be lost when shed in April than in February.

Early weaning of grazing sheep. 2. Performance of ewes

Two similar groups of Corriedale ewes were formed from a flock of 231. These were grazed on separate phalaris (Phalaris tuberosa) pasture at 8.6 or 17.3 ewes ha-1, respectively high and low nutritional planes, from seven weeks before their first lambing in spring 1968 until after their second lambing. Within each group the 1968 lambs were weaned by removal to other pastures at six or 12 weeks of age, or were left unweaned for 21 or 29 weeks in the high and low planes respectively. Birth weights in 1968 did not differ between planes, and for all ewes an increase of 1 kg in lamb birthweight was associated with a reduction in clean wool production during the last seven weeks of pregnancy of 0.22 � 0.11 g d-1. Pregnancy appeared to reduce by about one half the expression of genotypic differences between sheep in wool producing ability, and reduced 12 months clean fleece weight by about 5 per cent. Low plane ewes produced significantly less milk containing less solids. Liveweight gains and rates of wool growth were reduced by lactation and increased after weaning, wool growth the more slowly. Both rates of recovery were less in the low plane where, unlike the high plane, lactation appeared to reduce expression of genotypic differences in wool production. Clean fleece weights were reduced by about 5 and 10 per cent by lactations of respectively six weeks and five months duration. At subsequent joining a smaller proportion of the low compared with high plane ewes was marked by the ram and of these a smaller proportion produced lambs. Within the low plane, the longer the preceding lactation the lower the liveweight at second joining and lambing, and the lower the mating and lambing percentages. The results indicated that when there was a shortage of feed at and after lambing the performance of ewes would be improved by weaning their lambs at about six weeks. Ewe liveweights were consistently greater after six week weaning than after later weaning, a result confirmed in other experiments on weaning within fixed total areas of pasture.

The value to Merino ewes and lambs of continued superphosphate topdressing on a subterranean clover pasture ley

In an experiment at the Agricultural Research Station, Temora, New South Wales, Merino breeding ewes with their lambs grazed continuously from 1966 to 1970 at three stocking rates, 5, 7.5 and 10 ewes ha-1, on annual Trifolium subterraneum clover pasture topdressed every autumn with superphosphate fertilizer at nil, 94 or 188 kg ha-1. Stocking rate had an effect on ewe body weight in autumn each year and in winter and spring of the last year but it had no effect no wool production per ewe. Apart from the dry year, stocking rate had no effect on lamb performance. Superphosphate had little effect on ewe body weight and none on wool production but there were more lambs on the fertilized treatments than on the unfertilized pastures in 1967 when rainfall was low. Fertilizer encouraged barley grass dominance whereas the pasture not topdressed grew more clover and produced more burr. With no topdressing, available soil phosphate declined steadily over the five years to less than half the initial level. The results indicate that in a spring lambing, Merino ewe enterprise in the southern New South Wales wheat belt, where clover-ley farming is the general practice, annual pasture topdressing is no longer necessary after approximately 1000 kg ha-1 superphosphate has been applied to the soil and the fertilizer is continued through the cropping phase.

Early weaning of grazing sheep. 1. Growth of lambs

In six experiments during 1968-1972, Corriedale and Merino breeding ewes were grazed on phalaris (Phalaris tuberosa) pastures at densities of from eight to 33 ewes ha-1. In the first experiment the lambs were weaned at six or 12 weeks of age, or were left unweaned until liveweight was, or approached, 32 kg. The weaned lambs were grazed on a phalaris or a lucerne (Medicago sativa) pasture with abundant herbage, and growth rates were significantly greater on the lucerne. Lambs from ewes grazed at a density of 8.6 ha-1 grew to 32 kg more slowly if weaned at six rather than 12 weeks, and grew most rapidly if left unweaned; with ewes grazed at 17.3 ha-1 these weaning treatments had the reverse effect. The positive relationship between growth rate to six weeks and subsequent growth to 12 weeks differed between lambs weaned at six weeks and those unweaned. This effect was examined in the other five experiments on lambs weaned within fixed pasture areas at six weeks by confinement to half the original area. Growth was compared with that of lambs that remained with their ewes on similar total areas not subdivided. The slower the growth rate from birth to six weeks, the less was the adverse effect of weaning on growth during the subsequent six weeks, Regression analysis indicated the difference between weaned and unweaned lambs would be zero if liveweight at the end of the first period was 10.6 kg (95 per cent confidence limits � 1.8 kg) representing a growth rate from birth of about 150 g d-1. Practical implications are discussed.

Lucerne persistence and the productivity of ewes and lambs grazed at two stocking rates within different management systems

From 1967 to 1971 a grazing experiment was conducted at the Agricultural Research Station, Temora, New South Wales with Merino ewes and first cross spring lambs on lucerne pastures. Set stocking was compared with a number of rotational systems at twice replicated stocking rates of five and ten ewes ha-1. The rotational systems consisted of either five or seven paddocks each grazed to give a constant pasture recovery time of 36 days year round, or 36 days mid-summer to mid-winter and 24 days when lambs were present. Stocking rate was the only variable affecting ewe wool production and body weight. During the driest year the constant rotation was the best treatment, whereas in the wetter year ewes managed in a variable rotation grew most wool. The number of lambs born and their birth weight did not vary among treatments. Growth rate was slower at the higher stocking rate but the management treatments had no effect on lamb growth. Lucerne plant density decreased by half during the first three years of the experiment. Thereafter plant density was maintained in the rotationally grazed systems. Under continuous grazing at the high stocking rate no lucerne survived after four months but at the low stocking rate most remaining plants died after a spring drought in 1971.

Effect of time of joining and rate of stocking on the production of Corriedale ewes in southern Victoria. 3. Wool growth and the composition and availability of pasture

A study was made during a three year period (1 968-1 970) of wool production by a flock of 540 ewes grazing annual pasture at Werribee, Victoria. The ewes were stocked at three rates (5, 7 1/2 and 10 ewes ha-1) and lambed between July 6 and August 20 or between September 10 and October 29 each year. Fibre diameter and length of wool samples were measured in 1968, 1969 and 1970 ; in 1970 growth of greasy wool was calculated from staples of dye-banded wool. Wool growth was reduced in all ewes during late pregnancy and early lactation but was not affected during late lactation in ewes lambing in September. The proportion of tender fleeces from all ewes was greater in 1970 and the weight of fleeces from only those ewes bearing single lambs was less in all years for ewes lambing in July than for ewes lambing in September. More ewes were barren and fewer ewes had twins in July and consequently the mean fleece weights of all ewes from both groups were similar. Fleeces from ewes stocked at 10 ha-1 were lighter, shorter and finer than fleeces from ewes stocked at 5 and 7 1/2 ha-1, but the proportion of tender fleeces did not differ between the groups. Wool production of ewes stocked at 5 and 7 1/2 ha-1 increased from 1968 to 1970, whereas that of ewes at 10 ha-1 did not. This was associated with differences in pasture availability and composition. At 10 ewes ha-1 less pasture was present in winter and spring in 1970 than in 1968, whereas at the other stocking rates it was greater. In 1970 the density of weeds in autumn was greater and in spring more silver grass (Vulpia spp.) and less brome grass (Bromus spp.) was available at the high stocking rate.

Effect of time of joining and rate of stocking on the production of Corriedale ewes in southern Victoria. 4. Production of ewes born in July and September and effect of inclusion of Phalaris tuberosa in annual pasture

The production of two groups of 56 ewes born either in the month of July or September in 1968,1969 or 1970 (a total of 336 ewes) was compared until November 1972. From weaning (1 2 weeks) to approximately 15 months of age the ewes were grazed on two types of pasture (with and without Phalaris tuberosa) at two rates of stocking (8 and 11 ewes ha -1) and thereafter ewes born in the same year grazed common pasture. Ewes lambed in August, the first lambing being at two years of age. Throughout the experiment ewes born in July remained heavier and produced heavier fleeces and heavier lambs than ewes born in September. In the first lambing (maiden ewes only) 20 per cent more lambs were weaned from ewes born in July than from ewes born in September but at later lambings differences in reproductive performance were small. Liveweight gains of ewes grazing pastures containing phalaris were 1 to 2 kg greater between November and February than those grazing pasture without phalaris. At their first lambing, ewes that had been grazing phalaris at the rate of 8 ewes ha-1 produced fewer lambs than the corresponding group grazing pasture without phalaris. Losses in production due to lambing ewes in July rather than September as previously reported are unlikely to be offset by production differences of their offspring.

Effect of time of joining and rate of stocking on the production of Corriedale ewes in southern Victoria. 2. Survival and growth of lambs

A study of the survival and growth of lambs was made over a three year period (1968 to 1970) on a flock of 540 ewes grazing annual pasture at Werribee, Victoria. Ewes were stocked at three rates (5, 7 1/2 and 10 ha-1) and lambed between July 6 and August 20 or between September 10 and October 29 each year. Observations were made on the same ewes each year. Rate of stocking had no effect on the birth weight of lambs but single-birth lambs born in September were lighter than those born in July. More twins were born in September than in July and a smaller proportion of lambs born survived from the September than from the July lambing. Of the lambs born to ewes stocked at 10 ha-1 in 1968 and 1969 a smaller proportion survived than of the lambs born to ewes stocked at 5 ha-1. The growth rate of lambs born in July was constant between birth and weaning at 12 weeks of age but declined as rates of stocking increased. When the lambs born in September were about eight weeks old the pastures matured and growth rates of lambs declined and at weaning liveweights of lambs from plots stocked at different rates were similar. Lambs born in July on plots stocked at 5 and 79 ewes ha-1 were as much as eight kilograms heavier at weaning than the lambs born in September at equivalent rates of stocking. Neither rate nor time of onset of milk production was significantly affected by stocking rate.