The effects of lupin or oat grain supplements on liveweight change, staple strength and position of break for sheep grazing dry annual pastures.

Abstract

Proc. Aust. Soc. Anim. Prod. Vol. 18 THE EFFECTS OF LUPIN OR OAT GRAIN SUPPLEMENTS ON LIVEWEIGHT CHANGE, STAPLE STRENGTH AND POSITION OF BREAK FOR SHEEP GRAZING DRY ANNUAL PASTURES A.N. THOMPSON* and K.M.S. CURTIS** and The effects of grain supplements on liveweight change, staple strength position of break for adult wethers grazing dry pastures from November to nil supplement (control), lupins Treatments used were: April was examined. (lupins) or oats (oats) fed from pasture senescence (25 November) or lupins Each supplement was fed at 100, 200, fed from 7 February (delayed lupins). 300, 400 or 500 g/hd/d, with sheep in the lupins treatment also fed at 50 g/hd/d. Supplements of lupins or oats generally reduced liveweight loss and increased staple strength compared to no supplement, except when lupins were given at While delayed lupins reduced liveweight loss after 7 400 or 500 g/hd/d. no effect on staple strength compared to controls. February, there was which it began affected the the time at Neither supplementation nor These results are discussed in relation to position of break in the staple. their importance to farmers. INTRODUCTION During the summer/autumn period in Western Australia sheep graze dry feeds of and low quality. The intake of these feeds is limited by low digestibility condition crude protein content. Hence, sheep generally lose weight and and there are reductions in wool growth rate and fibre diameter. beginning to reductions in live weight (LW) before farmers allow -nY feed supplement, and then only supplement to achieve maintenance. The cost of supplementation the supplementary feed, and the fact that high levels of increase not only wool production, but also mean fibre diameter of the fleece are the main reasons farmers adopt this strategy. Rowe et al. (1989) found that feeding between and 450 g/hd/d of lupins, oats or barley 150 mean fibre diameter in the fleece by only 0.5 to 0.9 to weaners, increased microns. There was an associated increase in staple strength from 17 up to 26 N/ktex. Staple strength is expected to become a more important determinant of wool prices and, hence, farmers may have to revise their feeding strategies. The experiment described here was designed to determine the effects of different levels of lupin and oat grain supplements and of time of commencement of supplementation on liveweight change (LWC), staple strength (SS) and position of break (POB) in the staple. XATKEUALSANDXETHODS The experiment was conducted at Barker Mount Research Station (Latitude 38O 38' S, longitude 177O 32'), where the climate is characteristically Mediterranean with an annual rainfall of 675 mm. There were 19 one hectare plots containing subterranean clover/annual ryegrass pasture, with between 2200 and 3300 kg dry matter (DM)/ha at senescence. This declined to an average of 1070 kg DM/ha in April, under grazing. * ** Department of Agriculture, Albany, W.A. 6330. Department of Agriculture, South Perth, W.A. 6151. 400 Proc. Aust. Soc. Anim. Prod. Vol. 18 One hundred and ninety Merino wethers (18 months of age, mean LW 51.3 + 0.45 the (s-e-) kg, mean condition score 3.2 & 0.10) were randomly allocated to treatments. The control treatment was replicated three times while the The treatments were: Control - no other treatments were not replicated. supplement; 6 rates of lupin feeding (50, 100, 200, 300, 400 and 500 g/hd/d) senescence (25 November) (lupins); 5 rates of oat commenced at pasture 200, 300, 400 and 500 g/hd/d) commenced at pasture sensecence feeding (100, of lupin feeding (100, 200, 300, 400 and 500 g/hd/d) (oats); and 5 rates commenced on 7 February, when mean LW was 46.9 + 0.73 kg (delayed lupins). The lupins had a metabolisable energy content of 13.7 MJ/kg DM and a crude protein content of 331 g/kg DM compared to values for oats of 9.3 MJ/kg DM and 136 g/kg DM. During the experiment there were significant rainfall events The (>5 mm) on 30 November, 7 and 24 December, 13 January and 25 March. rain in March resulted in a good germination and green feed persisted through to 2 May when good follow up rains (110 mm in 5 days) occurred. Supplementary feeding ended on 17 April when the control groups maintained three successive weighings, probably due to the availability weight through All sheep were grazed in common prior to and after the of green feed. Oats were provided in troughs twice per week and lupins were experiment. manually broadcast across the plots once per week. weeks Live weight and condition score of all sheep were recorded every two Mid-side from pasture senescence until the end of supplementary feeding. dyebands were applied monthly for determination of POB, and mid-side samples from all sheep at shearing in October for determination of SS. were taken POB was measured for 3 staples from each sheep. SS was measured for 10 staples from each sheep using an ATLAS machine. Relationships between LWC or SS and level of supplementary feeding were lupin fitted for lupins, oats and delayed lupins. With LWC, the delayed group was treated separately since the supplementation period was shorter. The regression equation used was: where Y is LWC (g/hd/d) or SS (N/ktex); a, b, c, d, e, f, g are regression coefficients; X, is the level of lupin feeding (g/hd/d); X, is the level of oat feeding and X,, is the level of delayed lupin (g/hd/d); feeding Differences in the response to level of feeding for the (g/hd/d). three supplement groups were compared. Quadratic terms were only included if significant (P < 0.05). RESULTS Effect of supplements on liveweight change Liveweight change and SS for different levels of lupins, oats and lupins are summarised in table 1. delayed 401 Proc. Aust. Soc. Anim. Prod. Vol. 18 Table 1 The effect of level of supplement on liveweight change supplementation and staple strength (SS) during (LWC) During supplementation (143 days), LWC with increasing levels of lupins or oats were described by the following equations: For the delayed lupin group, LWC during supplementation (69 days) increasing levels of lupins was described by the following equation: with The relationships between level of supplement and LWC during supplementation The relationship for lupins was were different (P~0.05) for lupins and oats. improved by fitting a quadratic function because of the adverse effects of 400 and 500 g/hd/d lupins on LWC (Table 1). The relationship for oats indicated a positive linear increase during supplementation (eq. 2), as did that for delayed lupjns (eq. 3). Effect of supplements on staple strength and position of break Changes in SS with increasing levels of each supplement were described following equations: by the For sheep on the delayed lupins treatment, SS was the same as that for the control sheep (Table 1). While there were no differences (P~0.05) in the relationships between level of supplement and SS for lupins (eq. 4) and oats (eq. 5), the relationship for lupins was improved by fitting a quadratic function. Again this was due to the adverse effects of 400 and 500 g/hd/d lupins (Table 1). Comparison of eq. 5 with 6 indicated that feeding oats early improved SS. While eq. 4 was not different to eq. 6, it is apparent that early feeding of lupins up to 300 g/hd/d also tended to increase ss. On average, the POB in the staple was estimated to be on 18 February- for the control sheep, 3 March for sheep on lupins, 23 February for sheep on oats and 19 February for sheep on delayed lupins. 402 Proc. Aust. Soc. Anim. Prod. Vol. 18 DISCUSSION The findings of this experiment indicate that delayed supplementation in this environment resulted in lower SS. With the increased importance of SS in the sale of wool by description, it is likely farmers may have to change their summer/autumn feeding policies. paddock Farmers seldom feed at levels in excess of 200-300 g/hd/d, unless low. At these levels of supplementation there were feed is extremely no differences between oats and lupins for adult dry sheep. However, when fed at more than 300 g/hd/d, lupins resulted in LW loss and SS similar to that lupins for sheep which recieved no supplement. At high levels of feeding, given once weekly -may not only have substituted for the dry pasture at a oats, but also to the extent that total digestible greater rate than intake was reduced. These adverse effects of high lupin feeding energy with delayed lupins, where sheep lost weight and were not apparent supplementary feeding. This indicates the effects may condition prior to occur primarily with adult dry sheep in good condition whose demands for energy are low. the Despite differences in SS, supplementation had no effect on POB in staple. In contrast, Rowe et al. (1989) found for November shorn weaner sheep that as SS increased, the POB in the staple moved closer to the tip. In south western Australia, the weakest part of the staple usually occurs near the break of season (Ralph unpublished). For the delayed lupin group, the break in the staple occurred on the 19 February, only 12 days after feeding commenced. The controls also broke at this time. Hence, there was insufficient time for the supplement to affect wool growth. The POB did not coincide with rainfall event or drastic change in sheep management. any However, in general, the POB in the staple corresponded to the time when fibre diameter was lowest (Curtis unpublished). It would seem the break occurred at this time as green feed became available in March, after which even the control sheep maintained weight. This experiment indicated that significant gains in SS may result from feeding low levels of lupin or oat grain supplements from pasture senescence. While additional work is needed to confirm these findings, it would seem that to produce sound wool above the Australian Wool Corporation recommended minimum of 32 N/ktex, supplementation should not be delayed until after body condition falls. The authors acknowledge the technical assistance of Mrs B.Mavrantonis, R. McDonald, and Mr M. Ellis, and to thank Mrs 3. Speijers statistical analysis. Miss for ROWE, J-B., (1989). BROWN, G., RALPH, I.G., FERGISON, Aust. J. Exp. Agric. 29: 29. C. and WALLACE, J.F. 403