The challenge feeding that is practised in South Africa using whole grain is less well formalised than the system described by Leeson. Our feed allocations tend to be far higher than those recommended by the breeding companies (190 g/bird/day as opposed to the recommended 165 g/bird/day). Feeding 25 grams of additional breeder feed greatly increases the daily intake of protein. It is felt that this additional protein intake results in a higher proportion of large, unsetable eggs. For this reason the basal level of breeder feed is held at the breeder recommendation and any additional feed is offered as maize. The daily allocation of maize is then varied.

Ostrich Performance Standards

Although SPESFEED do very little work in the Ostrich industry, from time to time our inputs are sought. What constitutes ‘good performance' has not been defined, but in a recent newsletter published by Blue Mountain Feeds International some goal and/or guidelines were published.

It must be made clear that the following criteria are achievable GOALS that we all should be working towards.

The fact that all of the above are being achieved now, by some breeder birds and a few producers some of the time, is an indication that these targets ARE achievable. In most categories there are a few farmers doing better than the goals listed above. It must be made clear that NO producer is achieving ALL of the above at this time. It is necessary to understand what constitutes good production in order to be able to work towards achieving these targets. It will take a number of years to reach these goals, but it is essential to start NOW.

Economical Heifer Rearing

The objective of rearing heifers must be to produce the best possible cows in the most economic way. The obvious questions of course are which are the best cows and what is the most economical way to rear them? Assuming that the correct genetics have been selected, the answer to both these questions is exactly the same i.e. the optimum age for calving heifers is at 24 months.

Many would feel that there seem to be advantages to calving heifers older than 24 months. They should be larger, better able to compete in the milking herd, and able to produce more milk than younger and smaller heifers. Research has shown conclusively, however, that total milk production in the first lactation will increase by less than 1% for every month that first-calving age increases over 24 months. There is no increase once first-calving age exceeds 27 months. The crucial rider to all of the above is that heifers must be big enough when they calve, regardless of the age. Heifers should be fed to achieve weight gains such that they achieve 85% of mature body weight at calving.

Heifers must not only be heavy enough at calving, but they must also be tall enough, for two reasons. Firstly, the animals have greater body reserves, which can be utilised to produce more milk during the first three months of lactation, when energy intake is mostly limiting and the cows are milking "off their backs". Secondly, the heavier the animal at calving, the closer she is to her ultimate mature live mass. She therefore requires less energy for growth during her first lactation. This allows more energy for milk production.

Table 1 gives some guidelines for live weights, daily gains and shoulder heights at different ages.

The most desirable growth pattern is for heifers to grow at a relatively constant rate. The basic growth targets for Holstein heifers are: 100 kg at three months old, then growing fairly slowly at 0.7 kg of liveweight gain/day to 250 kg at 10 months. One thing to be wary of is not to try and push growth from 3-10 months, because at this age, they will start to lay down fat in the embryonic udder tissue. Once the fat has formed, it restricts the subsequent development of the secretory tissue, and restricts future milk yield. From 14 months – when the heifer will be served – to 22 months, the growth rate needs to be more rapid at 0.85 kg/day. Two months before calving, the feeding can then be slowed down, to ensure that the calf doesn’t grow too big. By 14 months, your heifer should weigh 350 kg and should be served at 15 months weighing 375 kg.

Lifetime milk yield, 305-day lactation yield are maximised when heifers calve for the first time between 23 to25 months of age. This also applies when one considers the economics of heifer rearing.

Unfortunately, it is very difficult to find realistic data on heifer rearing costs in South Africa. The DHIA provides the dairy industry in America with a vast database and they have some interesting facts and figures regarding heifer-rearing costs. It may not be ideal, but converting some of these figures into Rands makes some interesting and surprising reading! Table 2 summarises the cost of rearing a heifer to calve at different ages. These costs would probably appear to be high to most South African farmers. If one formulates diets based on maize silage, hay, maize and a protein concentrate then a feed cost of approximately R3000.00 – R3500.00 to rear a heifer to calve at 24 months is very realistic in South Africa.

According to American data feed costs represent 50-60% of the total cost to rear a heifer. If this is the case, which seems to be very likely, then the figures in Table 2 are not that unrealistic. Labour costs may be lower in South Africa but this difference is probably more than made up by higher interest rates. The cost of raising dairy heifers depends on the price of feed, quality of forages, death losses, culling percentages, and other fixed and variable costs. Age at first calving, however, remains the single most important variable influencing heifer rearing costs. It is interesting to note that the average daily feed costs to raise a heifer to 23.3 months is R0.78 more than the daily feed cost for the heifer that calves at 33.9 months.

Despite this difference the total feed costs for the faster growth rate is R700.00 less and accounts for about 40% of the difference in total costs to rear the two heifers. The reason for this difference is that the heifer growing at a faster rate uses the feed more efficiently. Daily costs incurred, other than feed costs, remain virtually the same regardless of the age at which heifers calve. This means that the greater number of days needed to get slower growing heifers to calving age is the other major factor for the increase in total costs.

Table 3 analyses the economics of rearing a heifer to calve at either 24 months or 30 months. The approach used in this analyses is to assume that the break-even cull age is the age at which an animal can be culled and her income, including her salvage value, is sufficient to recoup her rearing costs. In this situation, the heifer calving for the first time at 24 months only has to remain in the herd long enough to calve the second time (37 months of age). The value of her second calf is enough to put her income over the top. The heifer calving at 30 months has to remain until she is 45 months old, which is 2 months into her second lactation. Note that the older heifer needs to stay until she is 8 months older than the younger heifer, which represents 2 additional months over the difference in age (6 months) at first calving. The assumptions used to do these calculations are listed under the table. A decrease in milk price, and/or the beef price and heifers with a genetic potential lower than 11000 litres will obviously increase the break-even age for both heifers.

Besides the cost advantage, there are other advantages to calving heifers at 24 months. In a herd of 100 cows, with an average calving age of 24 months and a 40% replacement rate, 40 heifers are required annually to maintain herd size. Those heifers will enter the herd over the next year and would range in age from birth to 12 months. In total, 80 heifers are required on the farm. Given a 10% death loss, 88 heifers are required to maintain herd size in which age at first calving is 24 months.

The same process can be used to estimate the number of heifers required in a herd where age at first calving is 30 months. Forty heifers will also be required in the year; however, these heifers will range in age from 19 to 30 months. Next year’s 40 replacements are currently between 7 and 18 months. So there are still 6 months worth of heifers being raised on the farm. That is equal to 20 more heifers, for a total of 100 heifers. Accounting for death loss, 110 heifers are required to maintain herd size in which age at first calving is 30 months.

Increasing calving age therefore greatly increases the inventory of heifer replacements needed and it increases generation interval, which will delay bringing in genetically superior replacement into the herd.

Balancing rations for different age groups can significantly reduce fed costs. Differences in nutrient requirements and feed intake at different stages of growth means that heifers of approximately the same weight and size should be grouped together. This would generally require a minimum of 5 groups; 1.) Pre-weaning (0-2 months), 2.) 3-6 months, 3.) 7-12 months (or puberty) 4.) 13-16 months (or confirmed pregnant, 5.) 17 months - steam-up. Each of these groups has different nutrient requirements. The 1989 NRC specifications for replacement heifers are sufficient for calving heifers at 24 months. The one exception may be for heifers younger than 15 months where it may be advisable to increase protein levels by about 5%, especially on maize silage based rations. This will ensure that there is sufficient protein to promote good growth and prevent heifers from becoming too fat prior to puberty.

To conclude:

Water Quality in Broilers

The importance of good quality water in relation to broiler performance is widely accepted by livestock producers. However, there are extreme variations in water quality. This makes it very difficult to determine exactly which factors (called inclusions) in the water positively or negatively affect broiler performance. In the past studies have been conducted on water quality and its influence on broiler performance in different regions of the USA. In examining the results of these studies, it is evident that the water inclusions (or substances) measured not only act in variable combinations with each other, but also in various concentrations.

This makes it difficult to make definitive statements regarding broiler performance in relation to specific levels of the contents in the drinking water. However, in each of these studies it has been clearly shown that bacterial contamination does negatively affect broiler performance.

Recently, Zimmerman (1997) reported results on the relationship of drinking water and broiler performance in the mid-Atlantic portion of the USA. He reported that total aerobic bacteria number in drinking water lowered broiler body weight while increasing feed conversion and post-mortem condemnations. These results are similar to other studies with regard to the relationship of bacterial content of drinking water and broiler performance. Others have estimated that young broilers that consume contaminated drinking water can experience increases of two to three points in final feed conversion. In summary, the most significant influence of water quality on broiler performance is bacterial contamination of water, particularly borehole water. It is important that we check our boreholes often to make sure they are not contaminated. Contaminated water can come from water run off of fields spread with old litter, faeces from animals in the field, as well as from other naturally occurring organisms found in the soil). However, capping a well may not help if the well is located too close to another source of sewage or static water such as septic tanks, dams, etc.).

An excellent means of treating contaminated water is through continuous chlorination. In one study, chlorination of drinking water reduced total bacterial counts (micro-organism numbers were 100 to 10,000 times lower in chlorinated water as compared to non-chlorinated water), water consumption, litter moisture and caking, and condemnation rates while improving feed conversion (Murphy et al, 1987).

Measuring chlorine levels is relatively easy with the help of a swimming pool test kit. A level of three ppm chlorine in the drinker farthest from a medicator should be adequate to keep bacterial numbers under control.

In summary, with all the opportunities to provide broilers with the ideal management, environment and a properly formulated diet the importance of water quality in broiler performance cannot be overlooked. Check your water source regularly for bacterial contamination as well as other water quality factors. If your broilers' drinking water is contaminated, check to see if your borehole is sealed properly and, if needed, make arrangements to have it properly sealed. Then begin chlorinating your birds drinking water either at the well, or in the broiler house to help control bacterial contamination.

K Bramwell

We have dealt with soya quality issues in a number of earlier newsletters. However, as we become more reliant on soya as the major protein source in our pig and poultry diets we would like to emphasis just how important it is to monitor the quality of the material that we use.

We have directed a fair amount of resources into monitoring the quality of soya used in the country. Samples sent to Dr Cruywagen for microscopic analysis and have shown Zimbabwean soya contaminated with cotton. We have also seen material heavily contaminated with limestone. KOH analysis of soya of West African origin has shown it to be over processed. Chemical analysis of 47% Soya of South American origin has shown that the average protein content is only 46.5%, while analysis of Zimbabwean soya has shown that some sources are excellent while others are fairly variable.

In a recent article in Feedstuffs (4 January 1999) methods of determining Soya quality are discussed. Parsons, form the University of Illinois, reviewed assay methods to determine which was the most useful for monitoring soya quality. The challenge in soya processing is to apply the optimum amount of heat to produce the most nutritious product. Under processing will negatively impact on amino acid digestibility because the anti-nutritional factors (trypsin inhibitor) are not destroyed. Over processing has a negative impact on amino acid digestibility because a proportion have either been destroyed or have been bound as indigestible compounds.

Three methods of determining the adequacy of processing was discussed, the Urease Test, the KOH protein solubility test and the protein digestibility index (PDI). The PDI index which measure protein solubility in water is the simplest of the three methods and may well be the best method of identifying quality soya. In the figures that follow, the degree of processing of soya was simulated by autoclaving the material for differing lengths of time. Chick gain was then plotted against the indexes of protein quality. From the figures it can be seen that the urease test is may be a poor indicator of protein quality.