Liveweight Of Sheep Research Articles

A comparison of the forage value for sheep of buckwheat and sorghum stubbles grown on the Southern Tablelands of New South Wales

Two grazing experiments were conducted to evaluate buckwheat and sorghum stubbles as forage for sheep. The stubbles were stocked by young crossbred wethers at 10 and 20 ha-1 for 55 days on the buckwheat and 81 days on the sorghum. Measurements were made at regular intervals of the availability and composition of plant material, diet selection, the intake of digestible organic matter (DOM) and liveweight change, while wool production was measured over each experimental period. More than one-third of the sheep grazing buckwheat stubble were affected by fagopyrism (buckwheat poisoning) and this probably reduced both liveweight gain and wool production. Buckwheat residues had a similar nitrogen content to sorghum (1 .0% vs 0.87%), but a lower organic matter digestibility (43.7% vs 57.1%). Mature buckwheat plants were not eaten readily. Mean liveweights of sheep on buckwheat stubble declined throughout the experimental period and overall changes were -3.8 and -7.0 kg for the low and high stocking rates, respectively. Corresponding values for sheep on sorghum stubble were 0.3 and -4.6 kg, although weight losses at the higher stocking rate did not occur until after 40 days grazing. For the same length of grazing as the buckwheat (55 days) the liveweight changes for sorghum were 0.2 and -1.2 kg, respectively. Wool growth rate was low for both stubbles but was more than 60% higher for sheep on the sorghum. Values for each stocking rate were 3.86 and 2.67 (g clean dry wool day-1) for the buckwheat, and 5.39 and 4.33 for the sorghum. It was concluded that sorghum stubble is a useful source of grazing for sheep on the Southern Tablelands but buckwheat stubble, because of its low acceptability, poor nutritional value and the risk of fagopyrism, is of very limited value.

Plasma volume measurements in sheep using Evans’ blue and continuous blood sampling

After intravenous injection of 0.3-0.4 mg Evans' blue/kg liveweight in sheep, blood was collected continuously for 10 min into 10 tubes. Calculations using the dye concentrations in the plasma collected between 3 and 10 min gave values of plasma volume in close agreement with those obtained by intravascular dilution of labelled macromolecules. The dye has no adverse effects on carcase quality and can be used in standard holding pens.

Effect of the liveweight of caged sheep and the amount of feed on offer on estimates of digestibility and ad libitum intake

Three experiments were conducted in which the amount of feed offered to caged sheep was varied. Fresh kikuyu grass (Pennisetum clandestinum) was fed in one experiment and hays in the other two. Within each experiment a significant correlation between dry matter digestibility and liveweight occurred; no differences were detected between the slopes found with the various diets (slope = 0.34 per cent increase in digestibility per kg liveweight). Up to 60 per cent more kikuyu grass was offered to sheep than they could consume. Over this range a significant positive correlation was found between the ratio of the unconsumed to consumed feed and digestibility. This result indicates that great care should be exercised if the results of sheep digestibility experiments are used to interpret field data.

Some effects of formaldehyde treatment of hay or silage and level of barley intake on the production of crossbred lambs fed in pens

Hay and silage treated with formaldehyde were compared with untreated hay and silage during in vivo studies of digestibility, and in growth studies where the forages were fed with and without barley to 6-month-old crossbred lambs. In the growth study there were 20 treatment groups (four forage types offered ad libitum x five barley levels 0, 100, 300, 500 and ad libitum g day-1). Sheep were fed for 6 and 12 weeks for groups fed silage and hay respectively following which animals were slaughtered. On a digested basis, barley contributed from 0 to 76 per cent of digested energy intake. Lamb growth rate varied between 0 and 150 g day-1 and was linearly related to intake of digested DM. Growth rates were above 100 g day-1 where barley constituted 60 to 70 per cent of this intake. Silage and hay with digestibilities of 62 to 65 per cent barely maintained sheep liveweights when fed as a sole diet. The sheep ate more hay than silage and treating the forage with formaldehyde did not significantly increase intake or growth rate.

Age and live weight in sheep

Abstract The age at which ewes reach their maximum live weight depends on the environment. At Lincoln College ewes increase in live weight from the two-tooth stage to a maximum at 5–6 years and then decline. The increase is about 8 kg. In the high-country environment no such increase occurs. Lambs born per ewe lambing also increase with oge to the 5- to 6-year stage.

Undernutrition in grazing sheep. II.* Calorimetric measurements on sheep taken from pasture

The fasting heat production (kilocalories per kilogram liveweight) of sheep normally kept at pasture decreased during a period of 4 months when their liveweight was declining owing to low availability of pasture herbage, but increased considerably after shearing in autumn. It subsequently remained higher than for well-nourished sheep, which showed an effect of loss of fleece for only a few weeks. In thin animals critical temperature was higher after shearing, and their rate of increase in heat production as ambient temperature fell below critical was greater than in sheep in good body condition. Energy expenditure per unit of horizontal locomotion or vertical ascent (calories per metre per kilogram) did not vary significantly with body condition, but total daily expenditure at pasture was probably greater for the undernourished sheep. These results, and energy expenditures at pasture calculated from estimates of carbon dioxide entry rate, were consistent with observations on ruminal concentrations of volatile fatty acids and body energy content. The observations indicated that maintenance requirements (kilocalories per kilogram liveweight) of undernourished grazing sheep might be up to 45% greater than those of well-nourished sheep, particularly during inclement weather. __________________ *Part I, Aust. J. Agric. Res., 23: 483 (1972).

Liveweight and wool growth of sheep in response to the quantity and botanical composition of annual pasture induced by nitrogen fertilizer and stocking treatments

For five years, three rates of ammonium sulphate (N0, N1, and N3: 0, 280, and 840 kg/ha/year) were applied as a split dressing to ,a pasture of Bromus mollis L. and Trifolium subterraneum L. which was continuously grazed by wethers set-stocked at 8.6 and 12.4 sheep/ha. The N0 treatment produced clover dominance, N1 a mixed sward, and N3 grass dominance. The higher stocking rate increased the proportion of clover in the mixed sward. These differences in botanical composition produced three significant effects on the relation between liveweight gain and quantity of green pasture on offer. An increase in the proportion of clover in the sward increased: (1) the quantity of herbage dry matter on offer required for liveweight maintenance; (2) the maximum rate of liveweight gain; (3) the quantity of dry matter on offer at the point of 90% maximum liveweight gain. Regressions of those three parameters on botanical composition accounted for over 90% of the variance. The effects of treatments on liveweight at other times of the year are also described. In the first year of grazing ammonium sulphate increased liveweight, apparently because of increased pasture on offer after emergence. In subsequent years the effect of ammonium sulphate was reversed: liveweight was reduced, and this was associated with lower nitrogen concentrations in, and lower quantities of, herbage produced. Wool elongation rates were greatest in spring and lowest prior to the germinating rains in autumn. Elongation rate was unaffected by stocking rate and only slightly affected by ammonium sulphate. From January to April, greatest elongation occurred on the grass-dominant N3 paddocks; from May to December greatest elongation occurred on the clover-dominant N0 paddocks. The implications of the role of nitrogen fertilizer in relation to sheep production in the winter rainfall regions of Australia are discussed.

Comparative productivity of some cultivars of subterranean clover (Trifolium subterraneum) in north-eastern Victoria

Eight cultivars of subterranean clover (Trifolium subterraneum L.)-Yarloop, Burnley, Bacchus Marsh, Nangeela, Clare, Portugal, Chiltern Valley, and Mt. Barker-were compared in mowing experiments at the Rutherglen Research Station in north-eastern Victoria. All eight had similar total annual yields of dry matter, but all except Chiltern Valley outyielded Mt. Barker (the common district cultivar) in most winters. Yarloop, Burnley, and Bacchus Marsh grew best in winter. Of these, Burnley has most promise, being apparently more persistent than Bacchus Marsh, and having lower oestrogenic potency than Yarloop. There was no difference in greasy wool production from wethers run at five to the acre on Mt. Barker or Bacchus Marsh pastures, despite higher pasture production on the latter. Hay was cut in two seasons ; after feeding equal amounts to each group of sheep, there was a surplus of 20 cwt an acre in favour of the Bacchus Marsh pasture. Clover seed production, winter pasture growth, and sheep liveweights also favoured Bacchus Marsh.

The effect of supplementing serrated tussock (Nassella trichotoma) with urea and molasses on the liveweight of sheep

Merino wethers forced to graze unsupplemented serrated tussock (Nassella trichotoma (Nees) Hack.) in spring 1961 sustained severe liveweight losses. These weight losses were not significantly reduced by supplementing the serrated tussock with urea, molasses, or urea plus molasses, despite a significant increase in intake on all supplemented treatments. The application of urea significantly increased the apparent crude protein content of the tussock foliage immediately after spraying. After grazing, the apparent crude protein content of the tussock fell to its original level despite two applications of urea, one on the first day and one on the fourth day, each week. Results of this trial, and the practical difficulties of applying urea and molasses, indicate that supplementing serrated tussock in this way would be of little practical importance.

Pasture type in relation to live-weight gain, carcass composition, iodine nutrition and some rumen characteristics of sheep I. Live-weight growth of the sheep

1. Two trials are described in which the live weights of sheep grazing four different pastures were compared. The four pastures comprised perennial rye-grass (P), perennial rye-grass plus white clover (P + C), short-rotation rye-grass (S), short-rotation rye-grass plus white clover (S + C).2. Large and highly significant differences existed between the mean live weight of the sheep on the various pastures in each trial. Thus the P sheep had a mean live weight of 107 and 102 lb. in trials I and II, respectively, at the end of each investigation, the P + C sheep 123 and 122 lb., the S sheep 125 and 126 lb., and the S + C sheep 140 and 137 lb.3. The differences in live-weight growth on the four pastures contain two major effects; an effect due to the difference between P and S and an effect which can be attributed to the presence of white clover in the pasture treatment.

Relation between Carcass Composition and Live Weight of Sheep

A RE-EXAMINATION of the work of Hammond1, Wallace2,3, Palsson and Verges4,5, and Wardrop6, suggests that the carcass composition of a sheep, in terms of dissected bone, muscle and fat, is more closely related to its live weight than to its age. Using all the available data from these papers, including ewes and wethers irrespective of breed, age, stage of pregnancy and nutritional history and ram lambs up to the age of 2 weeks, the following regression equations have been computed for estimating the body composition of sheep from empty live weight (that is, the weight of the live animal at slaughter minus the contents of its alimentary tract):

Effects of Gibberellic acid on pasture and animal production in winter

Results are given of a series of field experiments in which Phalaris tuberosa subterranean clover pastures were sprayed with gibberellic acid during winter. The growth of Phalaris was initially stimulated to a marked degree. At considerable expense per acre, this increase in dry matter produced a temporary advantage in liveweight in both weaner sheep and pregnant ewes at a time of the year when the supply of normal pasture was low. Further effects on animal production are discussed in relation to food demands and the sequence of plant reactions to spraying treatment; these effects were adverse in the case of lambing ewes because pasture growth temporarily declined after the period of stimulation. Effects of gibberellic acid on the nutritive value and botanical composition of the pasture are also reported.

Grazing management of native pastures in the New England region of New South Wales. I. Pasture and sheep production with special reference to systems of grazing and internal parasites

In a 4-year grazing experiment with Merino sheep, on a native pasture dominated by Bothriochloa ambigua S.T. Blake, three rates of stocking and continuous v. rotational grazing were compared. The effects of these treatments on the forage available and the botanical composition of the pasture and on sheep liveweights, size of sheep, wool production, wool fibre diameter, and parasitic infestation, both with and without drenching with phenothiazine, mere studied. The effects of seasonal conditions on the above and on the chemical composition of the pasture were also recorded. No consistently significant differences between grazing treatments in their effects on the pasture or on sheep liveweights or parasitic infestation were recorded, although during the final 3 years the total forage available was less under heavy stocking. Seasonal variations in total forage mere not marked, but, production of green forage increased greatly in the spring and declined to a very low level during winter. Similarly, sheep liveweights increased during spring and summer and declined in the winter. These liveweight changes were significantly correlated with the amount of green forage available. Wool fibre diameter showed similar seasonal fluctuations but the maximum diameter was attained earlier than maximum liveweight. Coincident with a spring rise in the amount of green forage there was also an increase in the percentages of crude protein and phosphorus in the green components of the pasture. Liveweight gains of the drenched sheep were significantly greater from the beginning of each experimental year in the late spring (November) to late winter (August) in all stocking treatments. In the spring, when the quality of the pasture improved and worm egg counts were low, drenching had no effect on liveweight gains in three out of four years. Drenching also significantly improved wool production and resulted in an increase in skeletal size of sheep in three out of four years. Drenching reduced egg counts of the parasites Oesophagostomum spp. and Haemonchus contortus (Rudolphi) Cobb but was less effective against Trichostrongylus-Ostertagia spp. For all grazing treatments there was no significant difference in the amount of wool produced per head, but over the 4-year period 56 per cent. more wool per acre was produced from the heavy than from the light rate of stocking.

Limitations to animal production imposed by seasonal fluctuations in pasture and by management procedures

An experiment with Merino wethers on a Phalaris tuberosa-subterraneum clover-volunteer grass pasture has compared throughout an annual cycle the effects of: (a) Seasonal fluctuations in quantity and quality of pasture on liveweight gains and wool production in sheep. (b) Different grazing systems at equal stocking rates both on pasture growth and on liveweight and wool production in sheep. (a) Availability of dry pasture did not affect animal production so long as green pasture was present. Small increases in green pasture in the period of slow growth (winter) gave large increases in liveweight and wool production. Large increases in green pasture in the period of rapid growth (spring) had no effect on the animal. On dry pasture (summer) heavy sheep lost more weight than light sheep. Increasing the amount of dry pasture reduced liveweight loss only slightly but resulted in a greater rate of breakdown of plant material. An asymptotic relationship between availability of green pasture aid animal gain is presented, the asymptote in this instance occurring at a,pproxirnatnly 1400 lb dry matter per acre. The implications of the results are discussed with reference to methods of investigation of species, fertilizers, end management procedures aimed at 01-ercoming pasture limitations to animal production. The validity of investigations which do not take into account the relative constancy of grazing pressure throughout the year, and the continuing effects of plant on animal and animal on plant, is questioned. (b) Regardless of the degree to which pastures had been checked by grazing in spring, all dried out simultaneously on the onset of summer, and all sheep on all treatments reached their peak liveweight turning point on approximately the same date. Less than one-third of the liveweight gain potential of the pasture was attained on any one of the three grazing systems. The mean amounts of the individual pasture components, and of the total weight of pasture, were identical at any one time under the three grazing systems. The closer the systems approached towards continuous grazing the greater were the liveweight gains and wool production.