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Boosting lamb growth rates from lucerne crops

MURDEDUKE FARM WALK, 27th March 2006

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About these notes

These notes were prepared by Cam Nicholson Grain and Graze regional co-ordinator and David Watson of Agvise Services.

The field work was conducted on Murdeduke Winchelsea by livestock manager of Murdeduke, Simon Falkiner and David Watson.

Disclaimer

The advice provided in these notes is intended as a source of information only. Southern Farming Systems, its employees or contractors do not guarantee that these notes are without flaw of any kind or is wholly appropriate for your purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.

Reference in these notes to specific commercial supplements in no way implies endorsement of these products by Grain and Graze or Southern Farming Systems.

Copying of these notes and information contained within

These notes may be copied in whole or part as long as recognition is given to the Grain and Graze program and Southern Farming Systems.

The Grain and Graze Program

The Grain and Graze program is based on co-operation between industry, government and regional natural resource managers.

Grain & Graze represents a first for Australian agriculture as four of the country's top Research and Development Corporations have joined forces to help farmer groups to deliver research and development activities. The national partners are Meat & Livestock Australia, Australian Wool Innovation Limited, Grains Research & Development Corporation and Land & Water Australia. The Corangamite and Glenelg Hopkins Catchment Management Authorities are also actively involved. The project is delivered by Southern farming Systems.

The South-Western Victorian Grain & Graze region is one of eight G&G pilot zones throughout the grains/sheep/beef zone of Southern Australia. For more information go to www.grainandgraze.com.au

Background

The Grain and Graze program is promoting the use of lucerne as a break crop in the cereal-canola rotation. It is envisaged a typical crop rotation may be one or two cycles of canola-wheat-barley followed by up to three years of lucerne. The lucerne would provide the opportunity to address difficult to control weeds such as annual ryegrass and act as a disease break. The other benefits of lucerne in a crop rotation include:

• Aggressive deep roots that deplete soil moisture to a point where winter rainfall will not replenish to saturation in the crop phase, thereby preventing the soil becoming waterlogged.

• the accumulation of significant amounts of nitrogen in the soil profile

• root pathways for subsequent crops created by decaying lucerne roots

• the opportunity to utilised ‘out of season’ summer feed in conjunction with a dedicated fattening system.

Farmers who have tried this perennial break crop report two major difficulties that need to be overcome if the potential of lucerne is to be fully realised. The first is the need to increase the growth rates of lucerne in winter[1]. The second is the disappointing growth rates of lambs grazing lush, high quality lucerne. Given the metabolisable energy on offer, growth rates should be significantly higher than most farmers experience. Theoretical liveweight gains of lambs should consistently exceed 350g/hd/day, however in practice 250g/hd/day is rarely exceeded.

This trial seeks to improve lamb growth rates on lucerne through supplementation.

Possible reasons for reduced lamb growth rates

The reasons for less than anticipated growth rates from lambs grazing lush lucerne are unclear. Discussions with many animal nutritionists provide differing although plausible reasons for poor growth. Unfortunately there is no conclusive data to confirm these differing positions. However there is general agreement the poor growth rates may be due to animal health issues (although the exact nature of these health problems vary) and / or the composition of the diet (issues relating to energy, protein, fibre, mineral balance).

Animal health issues

Redgut is the most commonly encountered animal health problem for lambs grazing rapidly growing lucerne, particularly in the spring or after summer rains. It is a poorly understood condition that may account for mortalities of 1-2% for no apparent reason. It is often confused with the clostridial disease pulpy kidney since symptoms of sudden death and rapid bloating are common with both. However it is suspected sub clinical redgut problems (ie not causing death but reduced performance) may be more widespread.

It is believed the ingested lucerne, being very palatable and high in soluble protein and low in fibre moves rapidly through the intestinal tract of the animal. This allows fermentation to continue within the large intestine causing both the production of gas and ammonia. This is thought to result in the in distension and twisting of the bowel which ultimately leads to death. On autopsy this enlarged and very red bowel or large intestine is obvious.

Dietary imbalance

Discussions with leading nutritionists commonly suggest the dietary problems relate to a lack of energy in the diet to balance the very high protein concentrations consumed by the animals. It is speculated that adding a high energy source of readily available carbohydrates should redress the protein/energy imbalance, although the cost effectiveness of adding additional energy is often disputed (eg MacKinnon project).

Other reasons include:

• a lack of fibre to ensure proper rumen mixing.

• a deficiency of specific minerals, either in total amount or in the proportions compared to other minerals (ie the dietary cation anion balance) is also suggested.

Possible solutions to lower than expected lamb growth rates

Animal health issues

To reduce the incidence of redgut, it is recommended to raise the fibre content of the diet by providing access to a low protein roughage such hay or straw while grazing the lucerne. This assumes animals will eat the roughage on offer, however selective grazing by individual animals may lead to variable intake of the fibre source.

“On/off” grazing utilizing a “rough” pasture paddock for two out of every five days is also a tactic that has proved successful but is labour intensive and does not allow for maximum animal production to be achieved. Likewise injection with Vitamin A,D & E every 6-8 weeks whilst animals are grazing lucerne is thought to reduce the likelihood of deaths and production losses occurring.

None of these treatments alone or in combination are totally reliable.

Dietary imbalance

Unfortunately there does not seem to be consensus from ruminant nutritionists as to what may be the most appropriate treatment to solve the dietary imbalance. As mentioned previously, the various solutions presented during our enquires seemed plausible, however rigorous scientific evaluation of these treatments in relation to grazing lucerne was not available.

Nevertheless it was felt the solutions suggested fell into three broad categories:

• Offer fibre to the grazing animal

• Offer high energy, low protein

• Add vitamins to the animal and offer minerals and rumen ‘buffers’.

To develop these treatments Grain and Graze enlisted the assistance of San Jolly, Productive Nutrition P/L, to design a grain / fibre ration that was most likely to increase conversion efficiency.

To test the theory that conversion efficiency could be improved by the addition of vitamins, trace elements and rumen buffers, a treatment was prescribed by David Horsinall of the Animal Logic Group. This involved the use of the commercially available products available through some merchandise stores.

Trial design

The lamb grazing trial was conducted under the direction of Livestock Manager, Simon Falkiner, with assistance from David Watson.

Three trials were undertaken. The first commenced in mid November 2005 and concluded in early December. The lucerne grazed was lush and plentiful at the start of the trial. Difficult seasonal conditions (no rain), aphid attack and shearing in mid December resulted in the first trial concluding earlier than anticipated (21 days only).

After shearing, further lucerne paddocks were found and a modified trial recommenced in January 2006 using the same lambs but with a reduced number of treatments. The second modified trial was undertaken but involved grazing smaller quantities of less digestible lucerne. The lucerne in this trial appeared stressed and not as lush as trial 1. The second trial ran for 14 days until the available lucerne was consumed.

After summer rain a third trial was commenced in late February and completed on March 22, 2006 using a new mob of lambs (26 days). The lucerne was limited in quantity but similar in quality to the first trial ie. Lush leafy lucerne, although its quality declined rapidly. Only two treatments were examined given the limited availability of lucerne.

The results of each trial are discussed separately and then combined conclusions are drawn.

Interpretation of the results - Understanding the interaction between feed quantity, feed quality, animal intake and animal performance.

The quality and quantity of the feed influence the amount of pasture an animal eats. When there is sufficient quantity of pasture, an animal will eat to its maximum. However as the quantity of feed declines, an animal cannot ‘harvest’ enough to completely fill its stomach (as animals only graze for a maximum of 11to 12 hours in any 24 hour period).

The quality of the pasture is equally important in influencing animal intake. An animal will only continue eating if there is space in their stomach to store the extra feed. High quality feeds are digested more rapidly in the stomach of the animal than low quality feeds. This means the stomach is emptied more quickly allowing more feed to be eaten.

It is the combination of feed quantity and feed quality that influence intake. Abundant high quality feed will maximise intake, whereas either limited amounts of high quality feed or large qualities of low quality feed will reduce intake.

		Quantity of feed of offer
		High	Low
Quality of feed on offer	High	High intake – can harvest a lot of feed and it passes through the stomach quickly.	Restricted intake – can’t harvest enough feed, so the stomach is never full.
	Low	Restricted intake – can harvest a lot of feed but can’t pass it through the stomach quickly, so the animal is prevented in eating more until the stomach begins to empty.	Low intake – the animal cannot harvest very much feed and what it eats takes along time to pass out of the stomach.

Once the animal has feed in its stomach, it extracts energy (amongst other things). By definition high quality feeds have greater concentrations of energy per amount of feed consumed. Therefore an animal offered a large amount of high quality feed leads to high intake of a highly concentrated product. This ‘multiplier effect’ can mean dramatic differences in available energy simply on the basis of small changes in quantity and/or quality of feed offered to the grazing animal (see appendix 1).

The total amount of energy consumed by the grazing animal is then used for maintenance and ‘growth’ (pregnancy, lactation, wool growth, muscle, fat). An animal will always satisfy its maintenance requirements before contributing to growth. Also as an animal gets heavier, maintenance requirements increase.

To maximise animal performance, the animal needs to be supplied with sufficient quantities of high quality feed, that provides an amount of energy well in excess of its maintenance requirements.

The trials conducted on Murdeuke were of a commercial scale which means the lucerne available to the grazing animals varied slightly from paddock to paddock and over time, even in the same paddock. Small differences in pasture quantity and pasture quality between paddock will influence the animal performance.

Therefore we stress the liveweight changes of the lambs in these trials need to be examined in conjunction with the quality and quantity of feed offered to the lambs.

To assist in understanding the influence the various supplements had in these trials, the Grazfeed[2] computer model was used to calculate predicted animal performance. The predicted result was compared to the measured result from the paddock. This allowed identification of liveweight change that could not be explained by Grazfeed and may be due to improvements in animal health and/or improved feed conversion.

Trial 1 – Grazing plentiful lush lucerne

Four treatments were applied. These were:

Treatment 1: No supplementation (control)

Treatment 2: Fibre (barley straw) fed ad lib and offered in large square bales.

Treatment 2: High energy, low fibre concentrate (barley grain) presented in a trail and intended to be fed at 450gms/hd/day.

Treatment 4: Commercially available lamb weaning treatment[3] involving injections of vitamins A,D,E and B12 plus a pellet containing buffers, rumen modifiers, vitamins and trace elements intended to be fed at 100 gms/hd/day (it was intended to use a loose lick product but the lambs refused to consume it). The treatment is aimed at reducing physiological and nutritional stress up to 50 days post weaning.

The content of the different treatments is listed (table 1). The barley and hay supplements were analysed by Feedtest , with the ELMS Lamb Weaning Concentrate Pellet based on the product label (Table 1).

Treatment	Dry Matter (%)	DDM (%)	Crude Protein (%)	Energy (MJ ME/kg)	Other	Cost ($/t)
Straw, barley	89.3	59.0	3.5	8.0		$80
Grain, barley	89.0	85.5	12.1	13.0	ADF – 5.6%	$150
Weaning pellets + Vit A,D,E and B12 injection	N/A	N/A	9.3	8.6	Organic and inorganic minerals, vitamins and vegetable oil	$1860 for pellets + $29c/hd injection

Table 1: Drymatter, feed quality and other components of treatments used.

Four paddocks of similar size with similar quantities and densities of lucerne were chosen. Each paddock was tested prior to the trial commencing and again at the end of the grazing period (table 2 & 3).

Treatment	Paddock	Drymatter (%)	DM (kg/ha)	DDM (%)	Protein (%)	Energy (MJ ME/kg)
Control	Partos	17.1	3801	70.1	29.6	10.5
Straw	Barrier East	19.2	3130	68.3	26.7	10.1
Barley	Langleys	19.3	3406	68.4	27.9	10.2
Weaning pellets	Holts	17.8	3361	69.0	27.2	10.2
Average		18.4	3425	69.0	27.9	10.3

Table 2: Feed quality and quantity on day 1.

Treatment	Paddock	Drymatter (%)	DM (kg/ha)	DDM (%)	Protein (%)	Energy (MJ ME/kg)
Control	Partos	43.0	1510	61.9	22.0	N/A
Straw	Barrier East	45.0	1687	62.6	22.6	N/A
Barley	Langleys	47.0	1863	63.2	23.1	N/A
Weaning pellets	Holts	45.0	1687	62.6	22.6	N/A
Average		45.0	1687	62.6	22.6

Table 3: Feed quality and quantity on day 21.

Lambs were second cross July drop lambs (Merino Border Leister dams X White Suffolk rams). Lambs were allocated to the treatment areas through a simple 4 way draft, having an average liveweight of 33.7 kg at the start of the trial. The stocking rate was set at 20/ha, resulting in approximately 200 lambs in each mob.

Imprint feeding of grain and pre-conditioning to the lucerne after weaning (for three weeks) occurred to all mobs of lambs before drafting into the four treatments. All lambs had received a vitamin A,D,E and B12 injection at marking, 5 weeks before the first trial commenced.

Lambs were drenched with Virbamec (an avomectin drench). To eliminate the possible confounding effect of internal parasites, the lambs were drench at approximately three week intervals during the course of the trial.

Modifications to the original treatments

There was difficulty in getting the animals to eat the various supplements offered while grazing the lucerne. These difficulties encountered for each treatment were:

• Straw - Observations would suggest the lambs ate very little of the straw on offer and tended to use the material for ‘entertainment’.

• Barley – The intention was to build up to feeding a barley grain ration of 450gm/hd/day. In trying to attain this level of feeding significant wastage was encountered and rates were cut back to a point where acceptable levels of wastage occurred. It was estimated the lambs only ate 30 gm/hd/day in week 1, 50 gm/hd/day in week 2 and 80 gm/hd/day in week 3. This is despite the imprint feeding pre-weaning.

• Weaning pellets - The intention was to feed this as a loose lick but this was not accepted by the lambs so similar pelletised form of the product was used. The prescribed treatment rates were also never achieved, with consumption very similar to the barley treatment (ie. 30, 50 and 80 gms/hd/day in weeks 1, 2 and 3 respectively).

Results

The liveweight gain over the 21day period is presented (table 4, figure 1)

Treatment	Starting weight 17/11/2005 (kg)	Finishing weight 8/12/2005 (kg)	Weight gain (kg)
Control	34.0	39.9	5.9
Straw	33.2	39.2	6.0
Barley	33.9	39.7	5.8
Weaning pellets	33.8	41.4	7.6

Table 4: Measured change in liveweight over trial period

(Figure 1 not shown - Download Full Document (.pdf 140kb) to view all figures and pictures)

Figure 1: Measured liveweight gain for lambs

Discussion

The quality and quantity of feed offered to the lambs at the start of the trial varied slightly, with the highest quality and quantity feed provided to the control group. The feed would be considered lush and of high quality with drymatter averaging less than 20%, digestibility around 70% and protein in excess of 25%. At the conclusion of the trial drymatter had been halved and digestibility reduced. Protein also declined but still remained above 20%. The drymatter results suggest most of the leaf had been consumed, leaving only stem behind.

Grazfeed calculations at the start of the trial predicted an average weight gain in excess of 350 gms per day on each of the treatments without any additional supplements. Given the high quantity of feed (more than 3000 kg/ha) and high quality of feed (DDM around 70%) on offer, there was minimal difference in predicted growth rates between treatments at the start of the trial. However at the end of the trial predicted liveweight gain from lucerne without considering the supplementation dropped dramatically, with greater differences between treatments (table 5).

Treatment	Anticipated weight gain on entry (gm/day)	Anticipated weight gain on exit (gm/day)
Control	385	159
Straw	360	190
Barley	372	210
Weaning pellets	375	198

Table 5: Predicted liveweight gain from Grazfeed at the start and of the trial excluding the effects of the supplements.

By estimating the daily change in feed quality and quantity during the trial period, it was possible to estimate the predicted total liveweight gain from Grazfeed and compare this to the actual liveweight gain measured. Over the 21 days of grazing, it was predicted the lambs in each mob should achieve an average weight gain of 290 gm per day. This comparison is shown in column 2 of table 6. A value greater than 100% suggest the recorded liveweight was less than predicted by Grazfeed.

The different treatments were then included into the Grazfeed calculations and the impact of predicted liveweight gain recalculated. The difference in performance could then be attributed to the supplement offered (column 3 of table 6).

Treatment	Comparison of actual and predicted weight gain on lucerne	Predicted increase from using supplement	Comments
Control	Lambs did 5% worse than predicted	NIL
Straw	Lambs did as predicted	Improve weight gain by 1.1 %
Barley	Lambs did 8% worse than predicted	Improved weight gain by 1.0 %	Substitution effect occurred with barley
Weaning pellets	Lambs did 18% better than predicted	Improved weight gain by 0.8%	17% increase ‘unexplained’

Table 6: Predicted impact of different supplements

The measured growth rate of the lambs was largely explained by the lucerne they were grazing in all treatments except the weaning pellets. Surprisingly there appears to be less suppression in lamb growth rate despite grazing the lush high quality feed. However this may be because the feed quality changed rapidly, limiting the period of exposure to the lush feed. An extended period of exposure may have resulted in reduced liveweight gain. A growth rate of approximately 280 grams per day was achieved during the 21 day period.

Providing barley straw to the lambs grazing lucerne made no discernible difference to liveweight gain. The measured difference between the control and the straw / lucerne treatment was only 5 gm/hd/day. Grazfeed calculations predicted this 5 gm/hd/day improvement.

The difficulty in getting the lambs to eat large quantities of barley limited the result of using this treatment. It was estimated each animal consumed a total of 1.1 kg of barley during the trial period. At such low levels of consumption, it is not surprising the treatment appears to have little influence on liveweight gain.

The weaning pellets, in conjunction with the vitamin A,D,E and B12 injection resulted in liveweight gains well in excess to that predicted by Grazfeed. Given the quality and quantity of lucerne these lambs were grazing, the treatment has increased growth rates during the 21 day period by 80 gm/hd/day over the average of the other treatments. The increase in liveweight cannot be attributed to increased energy intake through the weaning pellets. This would suggest an improvement in the efficiency of converting the consumed lucerne into liveweight gain.

Trial 2 – Grazing ‘hardened’ lucerne

The first trial was modified after shearing partly due to the results from the first trial and partly because of the limitation of additional lucerne paddocks. The straw and barley treatments were combined and the lambs from these previous treatments boxed together. This left three treatments remaining:

Treatment 1: No supplementation (control)

Treatment 2: Fibre (barley straw) fed ad lib and offered in large square bales and high energy, low fibre concentrate (barley grain) presented in a trail and fed at 100 gm/hd/day.

Treatment 3: Weaning pellets fed at 100gm/hd/day.

The same lambs used in trial 1 were used in trial 2, with an average liveweight of 44.5 kg at the start of the trial. The stocking rate was set at 20/ha, resulting in approximately 210 lambs in treatments 1 and 3 and 370 lambs in the combined treatment 2. The trial continued for 14 days.

Three new paddocks were sourced. One of these treatments required a collection of smaller lucerne paddocks to be used. Gates were opened between these smaller paddocks allowing grazing of all paddocks at the same time.

Results

The lucerne on offer to the lambs at the start and completion of this trial period are listed (table 7 & 8).

Treatment	Paddock	Drymatter (%)	DM (kg/ha)	DDM (%)	Protein (%)	Energy (MJ ME/kg)
Control	Churchills	45.2	1677	59.7	18.0	9.1
Straw & Barley	Homestation	31.8	2452	68.3	20.9	10.1
Weaning pellets	Various smaller paddocks	38.5	2065	64.0	19.5	9.6

Table 7: Feed quality and quantity on day 1.

Treatment	Paddock	Drymatter (%)	DM (kg/ha)	DDM (%)	Protein (%)	Energy (MJ ME/kg)
Control	Churchills	63.5	495	56.3	14.9	8.1
Straw & Barley	Homestation	39.8	533	61.5	22.3	9.5
Weaning pellets	Various smaller paddocks	51.7	514	58.9	18.6	8.8

Table 8: Feed quality and quantity on day 14.

The liveweight gain over the 14 day period is presented (table 9, figure 2)

Treatment	Starting weight 28/12/2005 (kg)	Finishing weight 11/01/2006 (kg)	Weight gain (kg)
Control	44.8	47.4	2.6
Straw & barley	43.8	48.1	4.3
Weaning pellets	44.9	48.9	3.9

Table 9: Measured change in liveweight over trial period

(Figure 2 not shown - Download Full Document (.pdf 140kb) to view all figures and pictures)

Figure 2: Measured liveweight gain for lambs

Discussion

The quality and quantity of feed offered to the lambs at the start of the second trial varied significantly between treatments. Overall the feed was of poorer quality and quantity that at the conclusion of the first trial than the start of the second trial. Visual observations would suggest the lucerne had ‘hardened’ considerably and lacked the lush, high moisture content of the previous trial.

The highest quality and quantity feed in the three paddocks available was provided to the straw and barley treatment group, with the poorest feed to the control group. This difference had a major influence on the growth rates measured in the three treatments.

Grazfeed underestimated the likely liveweight gains on all three treatments compared to what actually occurred. This makes interpreting the effect of the different treatments difficult, however it appear the influence of the weaning pellets was less once the feed had hardened.

Trial 3 – Grazing short lush lucerne

The results from the first two trials suggest an improvement in lamb growth rates on lush lucerne using the weaning pellets as a supplement. A third trial was established using an August drop mob of lambs at average weight of 38.9 kg.

Two treatments were tested

Treatment 1: No supplementation (control)

Treatment 2: Weaning pellets plus injections of vitamins A,D,E and B12 fed at 100 gm per day.

Four paddocks were used in the trial, the first pair of paddocks were grazed for 16 days and the second pair for 12 days. More than 350 lambs were used in each treatment group.

Results

The lucerne on offer to the lambs at the start and completion of this trial period are listed (table 10 & 11).

Treatment	Paddock	Drymatter (%)	DM (kg/ha)	DDM (%)	Protein (%)	Energy (MJ ME/kg)
Control	Black 50 22 Feb	31.7	532	70.9	23.6	10.6
	Lakeside 10 March	35.9	582	69.1	22.5	10.3
Weaning pellets	Churchills 22 Feb	37.5	338	76.7	31.2	11.6
	Homestation 10 March	32.9	974	70.9	23.6	10.6

Table 10: Feed quality and quantity at start of grazing

Treatment	Paddock	Drymatter (%)	DM (kg/ha)	DDM (%)	Protein (%)	Energy (MJ ME/kg)
Control	Black 50 10 March	38.2	160	53.1	16.0	7.8
	Lakeside 22 March	69.7	195	34.0	8.1	4.2
Weaning pellets	Churchills 10 March	58.5	515	47.6	16.1	6.7
	Homestation 22 March	43.4	122	55.3	13.6	7.9

Table 11: Feed quality and quantity at the end of grazing

The liveweight gain over the first 16 and following 12 day period is presented (table 12, figure 3)

Treatment	Starting weight 22/02/2006 (kg)	Interim weight 10/03/2006 (kg)	Finishing weight 22/03/2006 (kg)	Weight gain (kg)
Control	38.9	42.2	45.1	6.2
Weaning pellets	38.9	44.4	48.8	9.9

Table 12: Measured change in liveweight over trial period.

(Figure 3 not shown - Download Full Document (.pdf 140kb) to view all figures and pictures)

Figure 3: Measured liveweight gain for lambs

The results for this trial show an increase in liveweight which is greater than predicted from grazing lucerne alone. Grazfeed calculations did not predict the large differences in liveweight gain between the control mob and the mob fed weaning pellets.

Economic analysis

A simple partial budget was constructed to compare the costs and returns of using the weaning pellets (table 13). The cost of the pellets was $1860 per tonne and the liveweight gain was valued at $3.50/kg carcass weight ($1.68/kg lwt). Vaccination with vitamin A,D,E cost 14c/hd and vitamin B12 15c/hd (excluding labour). No feeding out costs were included.

	Additional liveweight over trial period (kg/hd)	‘Value’ of this additional gain ($/hd)	Quantity of pellets fed[4] (kg/hd)	Cost of vaccination & pellets ($/hd)	Financial gain ($/hd)
Trial 1	1.6 kg	$2.69	1.12 kg	$2.37	$0.32
Trial 2	1.3 kg	$2.18	1.40 kg	$2.60	-$0.42
Trial 3	3.7 kg	$6.22	2.60 kg	$5.13	$1.09

Table 13: Simple partial budget – weaning pellets

Discussion

The results from the series of trials conducted on Murdeduke would suggest lamb growth rates on lush high protein lucerne can be increased by the addition of a small quantity (100gms/hd/dy) of weaning pellets in conjunction with an injection of vitamin A, D, E and B12.

It would appear the conversion of the feed consumed into animal products is enhanced by this treatment. In the first trial an additional liveweight gain of 80 gm per head per day more than the control was achieved over a 21 day period. In the third trial over 26 days, the additional liveweight gain was 133 gm/hd/day over the lucerne treatment (control).

A simple gross margin would suggest both treatments are marginally positive this may improve if the effects could be sustained over a longer period of growth. However with pellets at a cost of $1860/tonne and fed at 100gm per head per day, a differential weight gain over the lucerne only treatment of 111 gm/day would need to be achieved to break even.

No attempt was made to try and attribute the positive liveweight gain to any component of the pellet (eg the minerals, vitamins or rumen buffers used), although it is clear the energy provided in this supplement does not account for the measured increase in weight gain.

However the benefits derived from the weaning pellets seem to diminish greatly when the quality and quantity of feed on offer is reduced as in trial 2. The less than ideal feeding conditions especially on the control and weaning pellet treatments resulted in lower lamb growth rates. The 300 gm/hd/day result on the barley and straw treatment can be largely attributed to the better feed on offer and to a lesser extent the additional energy provided by the barley.

The influence of feeding barley and / or straw remains unclear. The inability to get the lambs to eat these treatments meant they could not be adequately tested. The same problem may have been encountered with the rumen buffer / vitamin / mineral treatment if an alternative to the lose lick treatment was not available.