Assignment Task
Aim
To understand the dynamics between stocking rate, feed availability, supplementary feeding, liveweight, parasitic status and wool growth in grazing Merino sheep. Learning outcomes: You will gain experience with:
1. Designing grazing trials.
2. Techniques for the measurement of wool growth.
3. Relationship between nutritional status and wool growth
4. Relationship between nutritional status and parasitism
5. Relationship between stocking rates and sheep productivity.
The impact of stocking rate on wool growth Financial expediency, driven by fluctuations in wool prices, often forces graziers to adjust stocking rates in order to retain enterprise profitability. Decisions on such changes evolve from the individual circumstances on each enterprise and may involve either an increase or a decrease.
The aim of this study is to determine the biological impact of adjusting stocking rate on pasture yield and wool growth parameters. El Nino and La Nina events, due to the Southern Oscillation Index (OSI), and climatic indicators such as the Indian Ocean Dipole (IOD), Southern Annular Mode (SAM) and Madden-Julian Oscillation (MJO) influence Australia’s climate variability.
This results in graziers across southern Australia frequently encountering variability in feed availability and supplementary hand feeding is often required to maintain body condition and wool growth during shortages. Also, although feed often appears to be available in abundance the onset of a dry spell, which is common over the winter months in this region, may cause a significant feed shortage. This of course will also be dependent on stocking rate.
A line of Fine wool Merino sheep will be grazed on small plots on the reproduction unit at Cobbitty. The carrying capacity of this country most likely does not exceed the 15 and 30 dry sheep equivalents (DSE) per hectare used for the duration of the 5 weeks of the experiment. We wish to evaluate the carrying capacity of this country and have been allocated 2 plots to evaluate this. One of the major problems associated with the maintenance of sheep at the Reproduction block is the development of worm populations that are resistant to trichostrongylus and haemonchus spp. T. colubriformis is a common parasite in both lambs and mature animals in the tablelands and slopes of SE Australia.
Haemonchus contortus (barbers pole worm) is more commonly found in areas experiencing summer rainfall. Camden falls into this category. Animals will be drenched with a broad spectrum anthelmintic to minimise endoparasitic infection. Measurements Liveweight will be monitored at 1, 14 and 35 days of the experiment with sheep scales maintained at the sheep unit. It is important to also body condition score (BCS) the animals at each weighing. Wool measurements Mid-side patch Day 1 Mid-side patches will be shorn centred 30 cm from the vertebral column down the last rib. A 10 x 10 cm patch will be delineated with a pentel pen and stencil on the right-hand side of the animals Day 35 Mid-side patches will be shorn with small animal clippers (Size 40 blade) and the patch clippings stored in a seed envelope ready for washing. Samples will be dried in an oven at 40 0 C for 48h before weighing quickly to prevent moisture content returning to its normal regain of 16%. 13 Samples will be washed with a hot 1% nonidet detergent solution (x 6) and subsequently with ethanol (x 2) in nylon mesh filters. Samples are again dried in the filter for 48 h, re-weighed and clean fleece weight /100cm2 and wool yield calculated. This can then be converted to wool production for the whole animal using the assumption that the wool-bearing skin area of a 45kg animal is 1m 2 .
Thus’ the conversion from a mid-side patch to a whole sheep is a multiple of 100 given that 1m 2 is the equivalent of 10,000cm 2 . Dye band Day 1 A dye band will be placed on the same site as above but on the left-hand side of the animal. To make up the dye, mix equal volumes of Vero hair colour (Joico International: other hair colours will work as well) from any hair salon with 30% H2O 2. This is best done in a small plastic container and then draw up into either a 1ml or 2ml syringe. Place a 18g needle on the syringe with the tapered end cut off. The solution is applied in a thin line with a syringe and needle for a length of 10 cm on the skin of all animals. N.B. WEAR GLOVES. The hair colour can stain and damage skin.
Day 35 The staple containing the dyeband will be clipped also on the last day of the trial and used to measure the effect of treatment on staple length and on staple strength. Staple strength will be assessed subjectively. Pasture availability This will be measured by clipping herbage to a constant height within a 0.316m 2 quadrat at 3 sites in the paddock depending on the evenness of the herbage in each of the plots. Before the quadrat is cut a reading with a plate reader will be made so as to calibrate subsequent readings with the metre for this type of pasture. With this method pasture availability will be assessed at days 1, 14 and 35 of the experiment. Samples will be dried to a constant temperature in the oven at the Franklin laboratory for 72h and dry matter yield per m 2 calculated. Pasture will also be analysed for protein, energy and digestibility.
Faecal egg counts A. Method
1. Collect 10 g fresh faeces from each of ten animals selected at random from the flock. It is best to collect from the rectum with a gloved finger. Collect immediately before use, or otherwise store faeces at 4 o C.
2. For each animal, weigh out 2 g faeces and place it in a mixing jar and add 60 ml of saturated NaCl solution. Mix thoroughly with a powered stirrer.
3. Immediately after stirring, place a sample of the suspension into the counting chamber, holding the pipette at 45 o to the slide.
4. Allow the slide to stand for 1-2 minutes.
5. Count the number of eggs in the chamber (using the 10x objective lens).
6. Score the fresh faeces for consistency factor, as follows: 1 = normal pellets 1.5 = soft 2 = soft, no pellets 3 = watery
7. Calculate eggs per gram as follows: e.p.g. = number of eggs x 60 x consistency factor 14 B.
Faecal egg count – comments
1. If few or no eggs are found, the procedure may be modified to increase the probability of finding eggs. Allow the homogenized faeces to stand for 10 minutes in the mixing jar. Then withdraw a small volume of liquid from the surface of the suspension and place into the counting chamber. In this case the calculation of e.p.g. is not valid.
2. The method outlined is a variant of the McMaster Egg Counting technique which was developed in Australia. The essential equipment is the slide, consisting of two layers of glass separated by a known distance, and having on the upper layer a ruled square of known area. Hence, when this square is scanned microscopically a known volume of the suspension is examined.
3. It is essential to fill the slide whilst or immediately after stirring the suspension, since the eggs are continuously floating upward in both the mixing jar and pipette.
4. A number of factors must be considered in interpreting the McMaster Egg Count. These will include:
i) what worm species are present in the sheep?
ii) what is the fecundity of the worm species present?
iii) is the distribution of eggs in the faeces homogenous?
5. Clearly, the McMaster method must be treated with caution; there is considerable error in the count per se, and the count can only be interpreted in a broad sense. Nevertheless, it is a valuable diagnostic aid, since a better rapid procedure is not available.
6. Counts of over 400/g are considered to represent a significant worm burden. Timetable Date Activity Day 1 Tuesday 05/03/24 (S1 wk 3) 2-5pm Sheep reproduction block. Establishment of stocking rate. Collection of wool/pasture samples. Day 14 Tuesday 19/03/24 (S1 wk 5) 2-5pm Sheep reproduction block. Collection of pasture/faecal samples. Day 35 Tuesday 09/04/24 (S1 wk 7) 2-5pm Sheep reproduction block. Collection of wool/pasture/faecal samples. Ongoing Processing of pasture/wool samples. Please remember that the class is responsible for the collection, recording and distribution of all data.
Procedures Day 1, 14 and/or 35
1. Design trial for 15 and 30 sheep/Ha
2. Check or insert ear tags into sheep
3. Weigh and condition score all sheep
4. Allocate sheep to treatment groups
5. Clip midside skin and mark mid-side patches
6. Place dye bands on sheep 15
7. Collect faeces from animals and conduct faecal egg counts on them
8. Collect pasture samples and place in oven for drying.
9. Record minimum and maximum temperatures and rainfall for 5 week period.
10. Keep good records in duplicate and distribute (e.g. set up an Extensives FB page) EXTENSION ARTICLE) It is important to have the skills that will enable you to communicate effectively with a broad audience.
Throughout your undergraduate degree you have had ample opportunity to write in a scientific style. This assignment will assist in developing your “journalistic” style and enable you to effectively communicate in ‘layman’ terms. You have been asked to write a word article for The Land newspaper on: “Industry recommendations from a stocking density trial for Merino sheep at Camden NSW.” This should include a brief introduction providing the latest information in the scientific literature on this subject, together with a summary of the results you obtain from the current trial. This is to be written in the journalistic style found in The Land newspaper.