1 Water Requirements

Transcription

1 1 Water Requirements

2 2 1.0 INTRODUCTION Water Requirements Planning of stock and domestic water supplies involves a thorough investigation of the total requirements of a property. The system should be designed so that it will be compatible with the ultimate development envisaged for the property, even though it may not be completely installed initially. 2.0 STOCK WATER CONSUMPTION The main factors affecting water consumption are: The size, type, condition and individual characteristics of the animal. The food intake, in particular it s dry matter content, protein content, digestibility and salt content. The temperature, humidity, and rainfall. The frequency of watering i.e. how long since the animal last had access to water. The sources of water available to the animal are: Metabolic Water This water is formed in the body as a result of oxidation of animal tissues. This is important in the overall water economy of the animal but it is an internal function which is not of major concern to the design of a water system. Water consumed with food It is usually assumed that the water included in the food supplements the total daily water consumed by drinking. Thus a feed with a high dry matter content will provide little water for the animal and conversely a feed with a low dry matter content will provide relatively more water.

3 3 Free Water This is the water voluntarily drunk from troughs or any other source of drinking waters. This is the water a water system must provide. Animal Foodstuffs. Animal foodstuffs can be classified into 3 main groups according to their general nature and properties according the following scheme: Roughages ROUGHAGES s HAYS STRAWS FOODS SUCCULENTS GREENFEED ROOTS CONCENTRATES PROTEIN CARBOHYDRATE Roughage s. Roughage s are dry, fibrous and bulky. The fibre varies from 20-50% and accounts for the low digestibility and fairly low digestible energy. They tend to be high in dry matter and thus contain little water. The protein content is generally low and especially low in straws. Generally speaking roughages are good as a maintenance ration in winter but are too bulky and low in digestible energy for use as a production ration. Food DM Fibre Protein Digestible Energy (as % Dry Matter) Good hay Clover hay Lucerne hay Wheat straw Oat straw The hays are very variable in nutritive value due to stage of growth at cutting and the weather at harvesting. In general Lucerne hay is better than

4 4 grass hay because it is higher in protein. The straws are very poor indeed. Due to the demand for higher energy and digestibility hay has been replaced by silage in the diet of dairy cows. Available in three forms. Grass either ensiled or baled and Maize (Ensiled). These feeds contain a higher level of protein and energy. Dr matter is below 35%. Succulents. These foods contain a large amount of water. The dry matter varies from 10-25%. They are palatable, digestible, fairly laxative, and have a good effect on the animal. The succulents can be divided into two sub-groups: Greenfeed Roots Greenfeed covers grass, silage, and the green crops such as rape, chou moellier, lupins, green oats, etc. These foods are usually well balanced containing ample protein and are therefore very good for all purposes. Water content of some may be too high with the consequence that bulk may limit appetite. Roots include such foods as turnips, fodder beet and swedes. These are low in protein but provide a good bulk of food and are used for winter feeding. Food DM Fibre Protein Digestible Energy (as % Dry Matter) % Grass, young leafy Grass, stemmy Silage Rape Chou Green oats Swedes Turnips Fodder beet Potatoes

5 5 Concentrates. These are dry, non-fibrous, concentrated foods. They are low in fibre and hence are highly digestible. They are dry, containing only about 10-15% moisture. In all cases the digestible energy is high, of the order 60-80%. Some of the carbohydrate concentrates such as the cereal grains are low in protein. The remainder is rich in protein. All concentrates are costly to grow or to buy. They are therefore used sparingly and for definite purposes such as fattening store stock or for milk production. The type of concentrate, carbohydrate or protein should be fed according to the purpose. Food DM Fibre Protein Digestible Energy (as % Dry Matter) % Barley Oats Wheat Maize Peas From the foregoing discussion it is understandable that mid to late summer is the period of peak demand for stock water. At this time the weather is the hottest and the pastures tend to be higher in dry matter than in, say, the spring. The very high dry matter content of concentrates and roughage s must also be noted as a stock consuming this type of feed will require access to significant quantities of drinking water. 2.1 Volume Consumed by the Stock Because we must always design for the worst case scenario we must consider the stock water requirements in mid to late summer and design for the stock numbers which will be on the farm at that time. The peak daily stock water requirement in mid to late summer is determined on the basis of 4.0 litres per sheep stock unit and 9.0 litres per cattle stock unit. The term livestock units (LSU) or ewe equivalent (EE) or just stock unit is used to express the annual feed requirement of a standard 55 kg breeding ewe rearing a single lamb.

6 6 [Carrying capacities of farms are based on stock numbers carried at 30 June.] One livestock unit requires approximately 520 kg good-quality pasture a year. TABLE OF LIVESTOCK CONVERSION FACTORS LIVESTOCK CLASS Sheep WEIGHT IN KILOGRAMS Weight at Mating Ewe Pre-winter weight Hogget PRODUCTION Lambs Weaned 90% 100% 130% Slow growth rate Medium growth rate Fast growth rate LSU Ram Beef Cattle Breeding Cow % 6.3 Weaners Heifers, Steers, Bulls Slow growing Rapid growing Rapid growing Dairy Cattle Fat yield (kg) Cow Jersey yearling Friesian yearling Jersey calf Friesian calf

7 7 Further simple conversions are in common use: Autumn born calf 2.0, rising 1 year heifer 3.5, rising 1 year bull 4.0, rising 2 year heifer(empty)4.5, rising 2 year old heifer (in-calf) 6.0, rising 2 year steer 5.0, 3 year steer 5.5. Deer (red) Fawning Mature hind months hind months hind Dressing % Velvet (kg) Mature stag months stag Goats (dairy) Milk yield (litres) Does Grass only Browsing Goats (purebred Angoras) Mohair (kg) Does Stud Other Bucks Stud Other Hoggets Goats (Cashmere) Cashmere (g) Does Feral Av Bucks Farmed AV

8 8 NOTE: As goats may be browsing scrub and weeds, and because they do not readily consume clover, a direct LSU comparison with other livestock classes may not apply. Thus to determine the total stock water requirement one simply takes the number of sheep stock units and multiplies by 4.0 litres plus the number of cattle stock units multiplied by 9.0 litres to get the total volume in litres. For example the table below shows an analysis of current and projected stock and their peak water consumption. Class of Stock Number Stock Units Total, m 3 /day CURRENT Ewe/Ewe Hogget/2th 12,500 12, Lamb 2,500 1, Ram Breeding Cow 850 5, R 3y 300 1, R 2y 550 2, Bull PROJECTED Ewe/Ewe Hogget/2th 15,000 15, Lamb 3,000 2, Ram Breeding Cow 1,600 9, R 2y 1,400 5, Bull Peak Flow The information generated in 2.1 above gives the total volume consumed over the day; it does not tell us anything about the peak flow rate. That is we know how much water we need to supply over the whole day but we don t know how fast the animals will drink it. To deal with this we use a number of assumptions, which have been based on field studies of stockwater consumption. The assumptions are:

9 9 Dairy Cows. Up to a herd size of 200 cows assume a quarter will drink their daily requirement in any one hour (or, in other words, the cows will all drink their daily allowance in four hours). For a herd size over 200 cows assume a fifth of the herd will drink their daily requirement in any one hour. Dry Stock. For sheep one tenth of the flock will drink their daily requirement in any one hour. For cattle one sixth of the herd will drink the daily requirement in any one hour. It is important to note the major difference between the requirements of cattle and sheep; both in terms of daily volume and peak flow rate. Thus, for sheep and beef farms the ratio of cattle to sheep is very important from the point of view of the water supply. Therefore it is very important to ascertain from farmers their proposed stocking policy in the future and to explain to them the impact on the water supply. So, to calculate peak flows, we apply the assumptions listed above. For example: Class of Stock Number Stock Units Total, m 3 /day Ewe/Ewe Hogget/2th Lamb Ram Breeding Cow R 3y R 2y Bull 12,500 2, CURRENT 12,500 1, ,100 1,650 2, Peak Flow, m 3 /h PROJECTED Ewe/Ewe Hogget/2th 15,000 15, Lamb 3,000 2, Ram Breeding Cow 1,600 9, R 2y 1,400 5, Bull

10 10 In designing a system we will be interested in the TOTAL peak flow as well as the peak flow to different mobs of stock on the farm. For dairy farms it is easy since it is the milking herd which always controls the design; however, for sheep and beef farms it is necessary to determine the mob sizes of different classes of stock as at mid to late summer in order to determine which ones will place the greatest demand on the water system. 3.0 DAIRY SHED CONSUMPTION Water use in the dairy shed can be calculated from the following: Back Flush Cleaning Vat, once a day 150 l Machine cleaning Sanitizing rinse 9 l/unit Cold rinse 25 l/unit Non ionic rinse Hot detergent 5 l/unit 9 l/unit + 45 l Hot rinse 5 l/unit + 45 l 53 l/unit + 90 l Total 2 x 53 sets cups l = Sets of cups x l It must be noted that yard wash down requires a flow of 200 to 300 litres/minute and it is not usually possible to deliver this direct from the water system. So tank storage at the shed is necessary. Water for milk cooling can be drawn from the farm water system, used for cooling and then delivered to the storage tank from which the wash down pump draws it for yard cleaning.

11 11 In New Zealand peak milk production is approximately 30 litre/cow/day *. Typically the cows are milked at a 10h interval and a 14-hour interval being the difference between the morning-afternoon and afternoon-morning milking (respectively). Thus the peak volume of milk per milking is: X 30 = 17.5 litre of milk per cow per milking The peak flow rate of milk to be cooled is equal to the total volume divided by the total time. Total volume = number of cows x 17.5 litre of milk. The estimation of total time is important and in most sheds this is 1.5 to 2.0 hours. This milk cooler generally operates with a cooling water to milk ratio of 2:1 (i.e. twice as much water as milk flowing); thus the peak water flow rate is equal to twice the milk flow rate. The peak flow required at the dairy shed will usually be the flow required by the cooler plus any other concurrent uses such as teat washing. [NOTE: for wash down flows it is often a good idea to get the farmer to show you a hose which in their view is good and to measure that hose s flow rate, using a drum and stopwatch; in this manner you know what the farmer will be happy with.] * These figures are general as some cooler manufacturers use a peak milk yield of 10 litre and 14 litre per milking.

12 DOMESTIC WATER CONSUMPTION It is assumed that the minimum daily water use is 230 litres/day/person; the use of automatic washing machines and dish washing machines increases water consumption. A certain element of judgement is required here; but it must be observed that the total volume is not usually great when compared with the stock consumption. A use, which can consume a lot of water, is that of the garden. An allowance of 4 litres per m 2 of garden per day is usual. It doesn t take a very big garden to consume a lot of water; and, if there is a tendency to put the sprinkler on for long periods, the total volume used can be significant. To calculate the maximum flow rate to a house it is first necessary to list all the outlet points in the house and then to make a rational estimation of how many of these points are likely to be used simultaneously during peak periods. The discharges of various outlet points within a household are as follows: Shower, bath, laundry Toilet cistern Kitchen sink 5 to 15 litres/minute 5 to 7 litres/minute 10 to 12 litres/minute For example, in a household of two adults and two children, it would be reasonable to assume that, in the early evening, the bath, kitchen sink, and toilet cistern could be in use simultaneously, hence the total flow could be: Bath Toilet Kitchen Sink 14 litres/minute 7 litres/minute 11 litres/minute 32 litres/minute The maximum rate at which water is used on a house garden depends mainly upon the size of the garden. Most house gardens today are watered by garden sprinkler. A typical garden sprinkler on a 13 mm garden hose has a flow rate of approximately 15 litres/minute. For a very large garden it may be necessary to operate two sprinklers simultaneously, hence the required flow rate would then be 30 litres/minute.

13 OTHER DATA 5.1 Piggeries Cleaning: 1500 litres per day per 100 m 2 of area to be cleaned. Peak flow as per dairy shed wash down hose. Stockwater consumption: Mature pigs = 11 litre/head/day Brood Sows = 22 litre/head/day In the case of peak flow there will be a large number of drinking nipples and the like supplying water. In the absence of factual information on the number of outlets operating simultaneously use the relationship: Where n = number expected to operate N = total number available outlets [The flowrate required at each drinking nipple must then be obtained from the manufacturers or estimated.] 5.2 Poultry Laying hens 32 litres/100 birds/day Non-laying hens 18 litres/100 birds/day Turkeys 55 litres/100 birds/day For peak flow assume that one tenth of the flock will drink their daily requirements in any one hour.

14 14 Exercise 1 Miropuke Station had the following stock on hand in the summer: M.A. ewes 3200 E. Lambs 1250 Male lambs 850 Rams 50 Killers/dog tucker 60 Breeding cows 160 R. 2 yr. heifers 59 Heifer calves 57 R. 2 yr. steers 52 Steer calves 72 Friesian bulls 37 Bulls 6 The owners live in a 4 bedroom home, which is surrounded by extensive gardens, estimated to cover 3000 m 2 ; the owners are keen gardeners. They currently have three children at home. There is one full time employee who lives with his wife and young family of two, in a three bedroom cottage, which has a minimal area of garden. Calculate the total volume of water required each day and the peak flow rate. Show all your workings and be prepared to explain any assumptions you have made.

15 15 EXERCISE 2 You have been retained to design a water supply for a mixed dairy/bull beef operation. Using the information given below estimate the peak daily water demand and the peak flow rate [show all your workings.] Stock on hand in February 260 large Friesian dairy cows 80 heifers 300 calves (born previous August) 200 R 2yr bulls Note 1. There is a 26 aside Herringbone shed. 2. Each row milks in approximately 8 minutes. 3. There are two houses on the property each having 5 people living in them. 4. Do not make any allowance for water for gardens.