Introduction

Integration concentrates the majority of their energy and technical resources on broiler production. Breeders generally do not receive the attention they deserve. Integrators are looking to maximize egg and chick production at the lowest cost with insufficient attention being given to the quality of the chick. There is an abundance of evidence that confirms that breeder nutrition directly impacts the progeny. However, these impacts are generally difficult to measure under commercial conditions and even under controlled trial conditions they may be obscured.

The obsession with lowering feed cost has, I believe, led us to a point where some nutrients, like vitamins and trace minerals are marginal in modern breeders. While, others like crude protein are generally fed in considerable excess and this profoundly affects breeder performance and health. Due to fierce competition and the subsequent low profit margins, vitamin producers are reluctant to invest resources in research, so little breeder vitamin and trace mineral research has been conducted over the past 15 to 20 years. In addition, the current benchmarking practices have pressured the industry in lowering cost wherever possible. Fifteen years ago, breeders were generally peak fed 165 to 170 grams per bird per day with peak egg production at 65 to 70 per cent. Today, the majority of breeders receive 145 to 150 grams of feed at peak with peak production at 80 to 90 per cent – this on reduced vitamin and trace mineral levels.

Measuring breeder nutrition impact on progeny is difficult due to a number of factors. Firstly, the assumption is that all birds receive the allocated feed amount; this certainly is not the case with 30- to 40-gram differences between birds being common. The birds that will be nutrient-limiting are those that are the most severely restricted. This may only be five per cent of the flock, so when assessing the commercial performance between two nutritional regimens it is difficult to have a large enough sample to be able to measure the impact. Secondly, some of the effects may only be apparent under stress conditions. Small or no differences may be seen under trial or ideal commercial conditions, but under a stress (disease, low broiler nutrient levels, chilling), the responses will be more apparent.

The Nutritionist's Role in Breeder Nutrition

Since breeders are restrict fed, it is the nutritionists responsibility to design a feed that meets the nutrient requirements of the bird under their particular set of conditions of; egg production, environmental temperature etc. and then to ensure that that the highest quality ingredients are used in these feeds and that the feeds remain constant over time. Since the birds are restrict fed, the breeder manager needs to 'learn' how to feed the birds. With constantly changing feeds this makes every flock a new experiment, which makes it difficult to manage body weights and uniformity.

Birds do not understand percentages. Producers focus on the nutrient composition of the feed. The most common question I hear is, "What crude protein and energy level should I be feeding?" We need to understand the daily nutrient needs of the bird for a particular environment, given amount of activity and egg production. We then need to know what feeding system is being used and how well feed is distributed to the birds. Once we have this information we know daily need for: kcals of ME, mg of amino acid, grams of calcium etc that the bird requires and how many grams we need to feed it. Then we can formulate the feed to meet these requirements.

Energy and Fat

Energy is a fuel for maintaining basic metabolism, mobility and egg production. Energy is not a nutrient as such but is the result of metabolic oxidation of energy yielding nutrients – carbohydrates, fats and proteins. Having reviewed a large number of breeder formulations, energy appears to be the fist limiting 'nutrient'. This is true under both hot and temperate environments. Under hot conditions fat is helpful as a source of readily available energy, to help with the increased energy demand for increased rate of respiration – panting. Under more temperate conditions, carbohydrates are the preferred source of energy as they are not as readily metabolized and do generate additional heat during metabolism (heat increment). Fat composition and quality is important for the breeder and progeny. Essential free fatty acids are required for cell membrane integrity, immune competence, fertility and embryonic development.

It is well documented that maternal feed fat composition directly influences the fat composition of the egg. This includes fatty acid profile and fat soluble vitamins. Wang et al. (2002) were able to show that maternal dietary polyunsaturated fatty acids (PUFAs) affected the PUFA levels in the spleen of progeny. They also demonstrated feeding Omega 3 fatty acids to the breeder resulted in higher Omega 3 fatty acid levels and immune responses in progeny. The immune response was measured by reduced wing swelling in birds injected with bovine serum albumin. Some other effects of vitamin supplementation will be addressed under the vitamin section.

Crude Protein and Amino Acids

Crude protein is a measurement of the nitrogen content of a feed or an ingredient, assuming that amino acids are the source of measured nitrogen. Crude protein does not give us any information about the amino acid composition and or availability. Modern nutritionists should only formulate feeds on digestible amino acid levels, using crude protein solely as means of easily analyzing blended feeds to ensure correct blending.

Commercial feeds are generally still formulated to minimum crude protein levels, which results in feeds that, with the exception of TSAA (total sulfur amino acids), have amino acids significantly higher than required. The critical amino acids in breeder nutrition are methionine (TSAA), tryptophan, lysine and isoleucine. Methionine and tryptophan directly impact egg size and egg production. A corn/soy diet has excess lysine and isoleucine. When formulating to minimum crude protein levels, the lysine levels are often up to 40 per cent above requirement. Work by Lopez and Leeson (1995) clearly illustrated the negative effect of excess crude protein on fertility and DeBeer and Coon (2006) identified lysine and isoleucine as two amino acids directly affecting the fertility of breeders.

* "Understand the daily digestible amino acid requirement of the breeder and strive to formulate feeds that supply these levels while minimizing the excess of the other amino acids."

Minerals

All nutritionists are aware of the critical importance of the macro minerals; calcium, available phosphorus etc. on bone and egg shell integrity. However, there is very good evidence that maternal levels of trace minerals especially zinc, manganese, copper and selenium impact levels in the egg and influence progeny. This is not new research; hen feeds deficient in zinc were shown by Edwards et al, (1959) to cause slow growth of chicks; Turk et al. (1959) to cause weak chicks, poor feathering and high mortality; and Kidd et al. (1992) showed supplementing with inorganic and/ or organic Zn increased levels of Zn in the bones and increased bone weight.

In addition to Zn's role in DNA and enzymes, Zn is particularly important in the young bird in the synthesis of two key proteins: collagen and keratin (Underwood and Suttle, 2001). Keratin is a structural protein in skin and feathers. Collagen is the major structural protein of internal tissues, including cartilage and bone. The cost of ensuring a sufficient and an available Zn source in breeder and early broiler feeds is minimal considering the impact of poor skeletal development and compromised immunity on the profitability of broiler production.

As with Zn, Mn, Cu and Se levels can be affected in the egg by maternal supplementation. Manganese is vital in embryonic and post natal bone development. Cu is essential for reproduction and development. Se has a sparing effect on vitamin E as an antioxidant.

Vitamins

Although severe vitamin deficiencies will cause a wide variety of deformities and severely affect hatch, grossly underfeeding vitamins is not commonly seen in practice. It is the marginal deficiencies caused either by low supplementation, sources of questionable quality/ availability and less dominant breeders consuming less than calculated feed quantities. The progeny will not exhibit classical deficiency syndromes, but they will not perform to their potential. Aviagen conducted a study to asses the impact on progeny where Vitamins E, K and B vitamins were supplemented at 20 per cent above Aviagen breeder recommendation. Although broiler body weights were only 20 grams heavier at term, mortality of the supplemented group was 2.2 per cent lower than the control birds, with a yield advantage of 0.2 per cent at 2kg body weight.

Egg yolk vitamin E levels were measured and a 50 per cent increase in α-tocopherol seen. In addition, candling clears at 60 and 64 weeks of age were 12.2 vs. 17.3 and 17.9 vs. 26.9 per cent per cent for the higher supplementation group.

Adequate vitamin and trace mineral supplementation with quality vitamins and available minerals is an inexpensive way to ensure that the young chick is prepared for optimal skeletal growth and a healthy immune system, to help deal with challenges during brooding.

Amino Acids and Enteritis in Broiler Chickens

An intact healthy gut is vital to the health and welfare of young chickens. The gut as a multi-cellular organ; has absorptive enterocytes, goblet cells for mucin production; immune cells and an intrinsic neural system. The gut is the first line of defence against, dietary toxins and enteric pathogen invasion. According to Reed (2001) more than 65 per cent of dietary threonine is used in gut function; the threonine content of mucin is excess of 30 per cent. Enteritis results in considerable loss of mucin, studies have shown that threonine will be partitioned away from protein deposition to support the gut and mucin production.

To demonstrate the importance of threonine under enteric stress, a threonine dose response study was conducted to evaluate the impact of L-threonine on enteritis in broiler chickens. Birds were reared to 14 days on a coccidiostat-free, corn/soy feed with increasing levels of added L-threonine (at lysine to threonine ratios from 64 to 72). At 14 days, the birds were challenged with Clostridium perfringens and grown to 42 days of age. Body weights of the challenged birds at the higher threonine levels showed a positive response at 31 days and were similar at 42 days. Breast meat yield on the high treatment was similar between the challenged and control groups at 42 days.

This study supports the theory that animals will partition threonine away from muscle protein to support gut health and mucin production (Ajinomoto Heartland 2003).

Conclusion

Breeder nutrition directly affects the health, egg production and fertility of the birds. There is considerable evidence that breeder nutrition affects the progeny. Although we seldom see the gross deformities of severe nutrient deficiencies, it would appear that current nutrient levels, particularly trace mineral and certain vitamins are marginal particularly for those less aggressive birds that are unable to consume their expected feed allotment. It is these subtle deficiencies that could benefit from proper supplementation of these nutrients.

Overfeeding of crude protein:

1. Costs money; a recent evaluation indicated around $3.00 per ton.
2. Results in additional heat increment, which contributes to the heat load under heat stress conditions. New high yield breeds are particular sensitive to heat stress and nutritionists need to help minimize this stress.
3. Negatively affects fertility
4. Excess protein is excreted, and elevates the nitrogen in the faeces. High nitrogen in the litter results in foot pad lesions and excess ammonia, which can irritate mucus membranes of the eyes a respiratory tract.

Breeder hens are producing the broiler chicks that are the basis of our business. Feeding them correctly will result in healthy, virile chicks, which will have the immune system and skeletal framework required to deal with challenges and achieve their growth potential. The increase in cost of feeding a breeder hen properly compared to the total cost of producing a mature broiler chicken is marginal.

Saving cents may be costing you Rands.

References

Ajinomoto Heartland L.L.C.. 2003. Effect of increasing levels of L-Threonine on C. perfringens induced Necrotic Enteritis in Broiler Chickens fed a corn/soybean diet. Internal research trial conducted at Shur-Gain AgResearch, Buford, Ontatio. Canada. Coon, C., M. DeBeer, M. Manangi, J. Lu, M. Reyes, K. Bramwell and J.M. Sun. 2006. Broiler Breeder Nutrition: The Amino Acid and Crude Protein Requirements of Broiler Breeder Hens for Maintenance, Production and Fertility. Proceedings of Arkansas Nutrition Conference, Rogers, Arkansas Edwards, H.M., Jr. W.S. Dunahoo and H.L. Fuller. 1959. Zinc requirement studies with practical rations . Poultry Sci. 38:436-442. Lopez, G. and S. Leeson. 1995. Response of broiler breeders to low-protein diets. 1. Adult breeder performance. Poult. Sci. 74:685-694 Kidd M.T., N.B. Anthony and S.R. Lee. 1992. Progeny Performance when Dams and Chicks are fed Supplemental Zinc. Poultry Sci. 71:1201-1206 Reeds, P. 2001. Thoughts on the biology of amino acid requirements. Internal Ajinomoto Heartland Presentation, Chicago, IL. Turk, D.E., M.L. Sunde and W.G. Hoekstra. 1959. Zinc Deficiency Experiments with Poultry. Poultry Sci. 38:436-442 Underwood, E. and N. Suttle. 2001. The mineral Nutrition of Livestock. CABI Publishing, London, UK. Wang, Y.W., A.O. Ajuyah, H.H. Sunwoo, G. Cherian and J.S. Sims. 2002. Maternal dietary n=3 fatty acids alter the spleen fatty acid composition and bovine serum albumin-induced wing web swelling in broilers. Poultry Sci. 81:1722-1727.

This paper was presented at the Animal Feed Manufacturers Association of South Africa (AFMA) meeting in 2007.

June 2010