General News

Welcome to the last newsletter of 1998. Most of the general news revolves around some changes that have occurred at SPESFEED. Trish Adam has joined us as Office Administrator. She has taken over the bookkeeping role from my wife Linda. Charmaine Nortje has started working for us on a part time basis following the birth of her little girl. She will be helping us with the newsletter, our courses and maintaining the technical database.

We have spread our operations a little further north and I am happy to say that Peter de Wet will be consulting in association with us in Zambia. Peter has an MSc in poultry nutrition from the University of Natal and currently lives in Zambia where he has been doing missionary work for the last two years. He will be involved on a part time basis and will continue with his church work as before.

We have been concerned for some time that both the cheques that we send our creditors and the cheques that are mailed to us are no longer secure. As some of you will know, our bank recently lost a number of cheques that we had already deposited when their delivery scooter was hijacked between the branch and their main data processing centre.

This has caused us to examine some alternatives. Standard Bank has recently gone live on the Internet. This means that electronic banking is available to most people including us, this holds a number of advantages for both our clients and us. Apart from Being "on line" to the bank at all times, we are now able to pay our creditors electronically.

There are some concerns about the security of the Internet, but we are assured that the data encryption mechanisms that the bank have built into their system would make any form of electronic tampering extremely difficult. We believe that the chance of cheques going missing using conventional post is far higher than it would be using electronic banking and would like to urge our clients to investigate this means of payment. Please ask Trish how best to do this.

Generally speaking a newsletter follows a particular style and format. The style of newsletters should be short and punchy, to convey as much information as possible in as short a read as possible. I hope that we achieve what we set out to do.

For sometime we have been receiving John Gadd’s pig newsletter called the "Pig Pen". This publication is excellent in that it is packed full of information in a very readable format. If you don’t already receive it please try to get yourself on the mailing list.

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The vagaries of the Rand have had some impact on many of the ingredients that we use in our diets. This has been particularly true in the case of Vitamins. Costs have risen by between 18 and 25% across the board. Expect premix prices to be adjusted upwards in the near future.

As the price of fishmeal has increased so our reliance on Soya beans, both in the form of Full Fat Soya and Oilcake has increased. In the most recent edition of the Journal of Applied Poultry Research there are two excellent articles on the effect of over processing of Soya on poultry performance.

No sooner had I written the above, two things happened. Firstly, a similar précis of this work appeared in Feedstuffs.

I believe that the information contained in the paper is relevant enough for it to appear in both Feedstuffs and SPESFEED NEWS. Secondly, we have been contracted by the American Soya Bean Association (ASA) to analyse and report on the relative quality of soybean meal from various sources. The aim of the project is to provide a detailed review on the quality, consistency and value of different sources of Soybean meal for livestock rations in South Africa. We will provide a regular review of the results throughout the next twelve months.

Pollution control regulations in Europe have lead to the regulations restricting the amount of phosphate that may occur in animal manure. Much of this phosphate occurs naturally in our feed ingredients, but occurs in the phytate form, which is not available to the animal. The inclusion of phytase enzymes in the diet means that much of this phytate phosphate, as well as many other minerals in the phytate form, become available to the animal. There is also some evidence that amino acid digestibility is also improved.

By using phytase enzymes the amounts of inorganic phosphate in the diet can be reduced. This results in a reduction in the phosphate levels in the manure by as much as 30%.

I have been interested in the use of phytase enzymes for a long time, but their costs have prohibited their inclusion in most commercial diets. Of late the price on phosphates have escalated sharply, while the price of the enzymes has been coming down. It would appear that they are now cost effective for use in layer diets, but they still have a way to go in the case of broiler and pig diets.

Practical formulation of dairy diets with amino acids

This article is a summary of the paper presented by Lourens Erasmus at the AFMA symposium in May.

As the genetic potential of dairy cows improves it is becoming increasingly important to ensure that their nutritional requirements are met. For cows producing 10 000 to 13 000 kg of milk / lactation, microbial protein supplies a decreasing proportion of total protein required. Significant amounts of protein must therefore be supplied by rumen undegradable protein (UDP). It is not just the amount of UDP, but also the quality i.e. the essential amino acid (EAA) content that is important. At present the majority of dairy diets in South Africa are formulated to meet UDP and rumen degradable protein (RDP) requirements with no consideration of EAA content. The limitation of this system was shown in an evaluation of 60 trials in which low UDP protein sources were replaced with high UDP sources. Milk production increased in only 19% of the comparisons, decreased in 9% and did not change in the other 73%. Possible reasons for the lack of response are:

Sources of absorbable amino acids

MCP supplies 50% or more of the absorbable AA to dairy cows. MCP has an apparent intestinal digestibility of about 85% and an EAA profile that is similar to that of lean tissue and milk. UDP is the other source of absorbable AA. The digestibility of UDP and the EAA profile varies a great deal, both among feeds and within feeds.

Lysine (Lys) and methionine (Met) have been identified as the first two limiting amino acids in maize based diets. Lys will tend to be first limiting and Met second in diets based on maize and maize by-products. Met will be first limiting and Lys second in diets with high legume and animal protein sources.

A useful way in which to predict which AA will be limiting for a diet is to assume that the AA composition of milk protein is indicative of the AA requirements for milk production. Different protein sources can be given a "milk protein score" by comparing their AA profile with that of milk protein (Table). The "milk protein score" is the proportion of the first limiting AA in the protein source relative to milk protein. For instance the protein in cottonseed meal contains only 46% as much Met as does milk protein. MCP remains higher in quality than most feed proteins. The challenge is to develop a MCP and UDP combination that presents desirable array of AA to the lower digestive tract. Obtaining this balance in practice is dependent on the use of computer models that predict AA flows to the small intestine and compares these with requirements. The result will obviously be different for each type of diet. Examples of computer models that do this are: the Cornell Net Carbohydrate and Protein System, the French PDI System and the Degussa model.

Production responses to additional AA (mainly Met and Lys) in the form of animal proteins or rumen protected amino acids (RPAA) in practical diets have been extremely variable. The type of production response depends on the stage of lactation. Increasing amino acid supply to mammary tissue tends to increase milk volume if started at or prior to calving. If delayed until peak production, milk volume increases are small so the main response is increased concentration of milk protein.

Requirements for AA can be expressed either in daily amounts (g/day) or on the basis of profiles. It is easier, however, to formulate a diet for a desired profile of absorbable AA rather than for a daily quantity of AA. Profiles can be determined more accurately and the approach is consistent with the concept of "ideal proteins" as used in monogastric formulations. Furthermore, the AA profile of protein entering the mammary gland is representative of that which is absorbed form the intestine. Therefore, it is at the site of absorption that the optimum profile must be achieved.

Three approaches have been used to estimate the EAA requirements of lactating cows: 1.) factorial (mathematical); 2.) "direct dose response" and 3.) indirect dose response. These different approaches have provided remarkably similar results. Therefore, until more research is done it seems reasonable to conclude that conservative estimates for the required contribution of Lys and Met approximate 15% and 5% of total EAA, or 7.1 and 2.3% of total AA, respectively when conventional diets are fed.

1. Maximise DMI.

 

Increasing DMI increases both MCP and UDP. Therefore, the first and most important step towards increasing AA supply to the small intestine is to increase DMI.

 

2. Maximise microbial protein synthesis.

MCP is the best quality and cheapest source of protein for milk production, so its synthesis must be maximised. MCP production is directly related to the amount of fermentable carbohydrate, which is the bacteria’s greatest requirement. It is the single most important factor that drives MCP synthesis. The second largest requirement for MCP synthesis is RDP, which supplies a mixture of peptides, free AA and ammonia. For practical diet formulation the following guidelines can be followed to maximise rumen fermentation and MCP synthesis.

 

1. Protein.

CP - 17-19% total diet DM

RDP - 60-65% of total CP

UDP - 35-40% of total CP

SIP - 30-35% of total CP

 

2. Carbohydrates.

ADF - 19-21% of total diet DM

NDF - 25-30% of total diet DM

Roughage NDF - 19-22% of total diet DM

NSC - 35-40% of total diet DM when feed ingredients are high in sugars and starches

NSC - 40-45% of total diet DM when fibrous by-product feeds are used.

Starch -: 25-25% of total diet DM.

 

When considering rumen degradability parameters the following general guidelines can be used:

Rumen degradable starch - 50-75% of total starch

Rumen degradable NDF - 50-60% of total NDF

Rumen degradable CHO - 50-55% of total CHO

Ratio of rumen degradable NSC (RDNSC) to RDP- Not more than 3.2.

1. Do not assume that feed ingredient UDP and UDP digestibility values are constant.

As DMI increases, the rate of passage of feed through the rumen increases and this will mean that less of the protein in a feed will be degraded in the rumen and UDP will increase. The UDP content and its digestibility in the small intestine can be significantly changed by factors such as temperature, humidity and heating time during processing. In order to formulate for AA the formulator has to have some idea of the actual amount of AA that a feed ingredient will make available for absorption from the small intestine.

 

2. Do not oversupply AA.

Overfeeding Met without regard to Lys has been shown to depress milk protein content and yield and feed intake. Always select UDP sources to achieve the "required" Lys:Met ratio of approximately 3:1.

 

It is going to become increasingly important to make use of computer models to firstly estimate AA requirements and then to balance diets that meets these requirements. However, the success of these models is determined by the quality of data that is entered. More research is needed and diet formulation programs must become more sophisticated and validated extensively in practice before balancing for AA could be performed with the same precision as for non-ruminants. Also, analyses of raw materials, especially forages, will have to be improved. Not only will analyses have to become more reliable but they will have to become more comprehensive. Formulating for AA will certainly be a big step towards more efficient, profitable and environmentally friendly milk production.

Layer Nutrition

We have understood most of the factors, which determine feed intake in laying hens for some time. That is to say we know what the effects of body weight, egg output and growth are in terms of nutrient requirement. We also know that laying hens are able to adjust their feed intake so as to meet these nutrient requirements. Intake can be predicted using this information and linear regression. However these predictions are not always accurate as there is often unexplained or residual feed consumption. Residual Feed Consumption (RFC) can be defined as the difference between observed and predicted feed consumption.

I recently attended a talk given by Dr Casey, the President of Hy-line International. He explained that the way in which his company was setting about improving the feed conversion of Hy-Line layers was to select birds with lower RFC.

The whole issue was put into perspective by some work by Gabarrou et al. published in the March 1998 edition of British Poultry Science. They report that earlier workers were able to show that the heritability of RFC was high at between 0.21 and 0.28 and that selection for RFC was thus valuable. In their experiment they used two strains of laying hens that had been selected for 17 generations for either high RFC (R+) or low RFC (R-).

They found that R+ birds consumed 48% more food than R- birds. Although the birds spent the same amount of time eating, R+ birds ate more frequent but smaller meals. The heat increment of feeding was significantly enhanced in the R+ hens (23.9 Vs 13.7 kJ/100 ME intake in the R- hens. When the birds were force-fed the same amount of feed both lines had the same heat increment, but when additional amounts of feed were fed the R+ hens were able to dissipate the excess energy consumed better than the R- hens.

We know that all of the major breeding companies are giving the matter of RFC considerable attention in their breeding programs. We are also becoming aware that it is becoming increasingly difficult to rear modern layer hybrids to meet the required target mass at point of lay. R- birds are less active in terms of their feeding behaviour. From a theoretical perspective their nutrient requirements have not changed. I have begun to suspect that the modern layer has become a "shy eater" for want of a better term. It would appear that perhaps there is some scientific basis for this feeling.

From time to time I am shown layer flocks that are pale (bleek) and have never known what the reason is. We have just bought a new book called "Comparative Avian Nutrition" by K.C Klasing and published by CAB International. It is a well-written and informative book. Whilst reading the section on Carophylls I found the answer to this question. The colour of a chicken's skin, adipose tissue, and egg yolk directly reflects the types and levels of xanthophylls found in its food. The intensity of pigmentation of the yolk and skin of chickens increases and then plateau’s as the dietary xanthophyll concentration increases.

If laying hens are switched to a xanthophyll-free diet, yolk pigmentation declines over a few days and within a week eggs with white yolks are laid. Clearly, tissue stores of xanthophylls are low relative to the large amounts needed for yolk pigmentation. If dietary carotenoid consumption resumes, yolks reach full pigmentation within a week's time. Even at high dietary carotenoid levels, poultry divert the majority to yolk production and other tissues lose colour because they do not receive a normal (maintenance-level) allocation. The rate of colour loss in specific tissues is related to the rate of cell turnover in that area. The skin around the vent loses its carotenoid pigment fastest, followed by skin on the face. The beak begins to lose pigmentation at its base, where it is renewed, and if laying persists for 5 weeks the entire beak becomes unpigmented. The scales of the shanks lose pigment following 4-5 months of continuous egg laying. When laying stops, pigment reappears in the same order in which it disappears.

In short, pale birds are most probably being fed a diet with marginal levels of Carophyll.

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Sow body condition - Standards for new genotypes?

Improved genotypes have been selected to grow efficient (fast/lean) to heavy slaughter weights. Edwards and Campbell (1993) have estimated that the maximum lean meat deposition in late maturing genotypes only occurs at between 100 – 140 kg live weight. The consequences for the breeding sow are as follows:

The changing characteristics of sows in UK nutrition experiments (Edwards, 95)

All these changes have made the modern sow more vulnerable to marginal nutrition. Problems with reproductive function first became a major issue with the advent of the "thin sow" syndrome, and recent research attention focused on the importance of deposition and maintenance of body fat reserves.

Body condition scoring (BCS) is the common method to assess sow condition. This method combines visual appraisal and estimated backfat to arrive at a number from 1 to 5. The relationship between BCS and backfat is shown below (Carrion, 98):

The above table shows the recommended backfat profile of the sow herd before farrowing and at weaning (Carrion 98).

The relationship between body condition score and backfat depth was measured on 2 farms and compared to the PIC data. The results are shown in the figure below:

Soya Oilcake Quality

In two articles in the most recent edition of the Journal of Applied Poultry Research, Aburto, Vazquez and Dale of the University of Georgia discuss both the implications of overprocessing (OP) Soya Oilcake and strategies for using this material.

Several methods of measuring the degree of processing of Soya are available to us. Perhaps the most widely used is Urease Activity (UA). However, low levels of UA are not always indicative of over processing, and since there is no negative scale in the UA test, this application is of limited value in quantifying the severity of OP. It has been shown that Protein Solubility (PS) in a 0,2% potassium hydroxide (KOH) solution closely reflects the degree of OP as reflected by impaired chick performance. It has been shown that Soya with a PS value of below 70% probably has impaired nutritive value and values of below 65% are almost certainly indicative of OP.

Excessive heat treatment reduces the nutrient content of Soya, principally by compromising protein quality. True amino acid digestibility decreased with over processing, the largest decreases being in lysine, cystine, aspartic acid and histidine.

Although varied responses have been observed regarding the energy (Metabolizable Energy) content of overheated Soya, these authors were able to show that in instances when Soya was severely overprocessed there was a significant decrease in energy.

The implication of using overprocessed Soya (PS of 35%) in young broilers is dramatic as can be seen from table 2. It was found that performance of chicks fed overproccesed material was not improved by the addition of methionine or threonine, in either the presence or absence of additional lysine. While the addition of lysine largely overcame the effects of overprocessing.

* Note that the PS of the OP material was 35% and that of the control 80%

In a second trial it was shown that if Soya is moderately overprocessed (55 to 70% PS) it can be used in practical diets provided that adequate lysine is added to the ration. The exact amount required depends on the degree of overprocessing, but it would appear that at least 0.12% of added lysine would be required in the case of moderate and 0.2% in the case of severely heat damaged material.

A good quality creep feed is digested efficiently by –pre-weaned piglets, and it contributes to pre-weaning weight gain when pigs are weaned at 4 weeks (Pajor, 1991). However the influence of creep feed intake on adaptation to weaning is not so clear. In fact, with piglets weaned at 4 weeks most studies report little or no relationship between creep feed intake of a piglet and its success in adapting to weaning. The exception being that the occasional piglet achieves an unusually high pre-weaning intake and can be weaned with little difficulty (Pajor, 1991).

Two creep trials where conducted by Ibis Piggery. In the first trial an imported starter pellet was compared to a local creep meal with a negative control group (received no creep) being added during the second trial. Feeding commenced on the 7^th day of age and the piglets where weaned at 26.2 days. All pigs received the same post-wean creep after weaning. The pigs where weighed at weaning and at 32 and 64 days after weaning.

The pre-wean results are shown in the table below:

1. Pre-weaning growth:

2. Pre Weaning creep feed intakes:

3. Post weaning growth:

4. Conclusions:

This reduced the growing period by at least a week and hence saved a minimum of 7 kg of grower/finisher feed.