Introduction

For successful broiler production a chick requires good bodyweight, with excellent nutritional reserves at day old. It needs to be in excellent health with a fully functioning immune system. From this starting point, providing the broiler with suitable environment and nutrition will enable optimal performance to be achieved.

The developing embryo and the hatched chick are completely dependent for their growth and development on nutrients deposited in the egg. Consequently the physiological status of the chick at hatching is greatly influenced by the nutrition of the breeder hen.

In reviewing breeder nutrition, it should be remembered that nutrient supply to the broiler breeder is a sum of two parts, namely nutrient content of the diet and quantity of feed supplied to the breeder birds. Both parts need to be balanced to ensure correct daily nutrient supply. It is also very important to realise that the cost of feeding the breeder appropriately to ensure good nutritional status of the chick is very low when viewed on a per chick basis and compared with the total feed cost of raising a broiler to slaughter weight. Calini (2006) calculated that the cost of breeder feed contributing to the production of a chick is equivalent to only 7% of the total feed cost for a broiler grown to 2.5Kg. This illustrates the value of ensuring the best possible nutrition of the breeder.

Nutrient Levels in Broiler Breeder Feeds

When considering nutrient levels in breeder feeds, the nutritionist must focus on the daily supply of individual nutrients to the bird. Starting with protein, studies have shown that the protein levels fed to breeders in production can affect chick bodyweight and final broiler performance. The relationship between protein content of breeder feed and chick weight seems well defined.

Using this information, a breeder diet with an energy density of approximately 2750 Kcal/Kg should have a protein content of 15%. This optimum protein level has been supported by other work, and it is important to remember this is an optimum level, not a minimum, as excess protein can be as detrimental as insufficient protein. In particular, it has been shown that excess protein reduces fertility. Furthermore, consideration must be given to protein quality and the nutritionist must ensure a balance of amino acids is supplied from good quality protein sources.

The impact of energy content of the breeder feed is not as well defined as that of protein. Reviewing studies carried out to evaluate optimum energy intake would suggest that 440 - 480 Kcals/bird/day is most appropriate for optimal chick quality. This equates to 160 - 175 g/bird/day at 2750 Kcal/Kg feed. When considering energy, attention must also be given to fat composition and in particular to the requirement for unsaturated fats such as linoleic acid. This essential fatty acid is required for cell membrane integrity, immune competence and embryonic development, therefore directly affecting chick quality. In practical terms, the inclusion of added fats into breeder feeds should be kept low, with preference for unsaturated fats rather than saturated fats.

The major minerals, especially calcium, phosphorous, sodium, potassium, magnesium and chloride are involved in shell formation; improvements in shell quality generally lead to better egg and chick quality. Variations in maternal phosphorous supply have been shown to influence bone ash of young but not older progeny. It is important to supply adequate phosphorus in breeder diets to ensure best possible bone integrity in the early stages of chick growth. In terms of trace minerals, most interest in this field has centred on the use of chelated minerals which have been shown to increase deposition in the egg and transfer to the tissues of the hen and the embryo. Most recent work has focused on the antioxidant status of breeders, embryos, offspring and the role of selenium. Seleno-methionine has been shown to improve both the vitamin E and antioxidative status of eggs, embryos and chicks up to 10 days of age. Supplemental zinc methionine and manganese amino acid complexes have shown improvements in chick immunity and liveability.

Table 1 is a summary of those minerals which when fed to breeders have an effect on progeny performance.

Vitamins are involved in most metabolic processes and are an integral part of foetal development, therefore the consequence of suboptimal levels of these nutrients in commercial diets are known to result in negative responses to both parent and offspring performance. Vitamins account for about 4% of the cost of a breeder feed, so economising on vitamin inclusion rates is rarely a sensible option. Generally there is a shortage of information on vitamin requirements of broiler breeders especially when related to offspring performance. Most of the breeder work is quite dated and since that time breeder performance has changed.

A review of work on fat soluble vitamins, biotin and pantothenic acid has shown that vitamin E has the largest impact on progeny. In general it seems to be justified to supplement practical breeder feeds with 100 mg/kg vitamin E.

The influence of increased vitamin levels fed to young parent stock on progeny performance is an area which has received significant commercial interest. Internal and field trials have shown that increased vitamin levels (mainly B Vitamins and Vitamin E) improved liveability and early growth. A practical basis for making recommendations is to feed vitamin levels that maximise the resulting level in the egg.

The Influence of Feed Allocation on Chick Quality

Underfeeding the hen can have an impact on chick quality and this is particularly noticeable in the early production period. Modern hybrid parent flocks commence production at a faster rate than in the past and consequently egg output increases over a shorter time span during the early laying period. Feed allocations during this period have not necessarily increased in line with this egg production trend. Low feed allocation intake by young commercial breeder flocks have been shown to compromise nutrient transfer to the egg, resulting in increased late embryonic death, poorer chick viability and uniformity (Aviagen Ltd 2002). In a study by Leeson (2004) broiler breeders were fed different levels of feed through peak production varying from 140 to 175 grams. Although the increased feed allocation increased bodyweight there was no influence on egg size up to 175g, however chick weight was influenced by feed allocation. See Table 2 below.

Table 2. The effects of breeder feed levels on chick weight
Peak breeder feed (g/b/d)	30 week breeder chick weight (g)
140	40.3
147	40.0
155	41.5
162	41.7
169	41.8
175	42.0

Summary

Research shows that nutrient supply to the broiler breeder is of consequence to chick quality and production performance. This places greater emphasis on the nutritionist providing the correct nutrient density diet and the flock manager to provide appropriate feed intake to the bird coming into lay and through the production period.

4 Key Points

• Breeder Nutrition influences chick quality and broiler performance
  
• Broiler performance can be economically improved by investing in breeder nutrition
  
• Supply diets with adequate and consistent nutrient levels to breeders
  
• Manage feed quantities with reference to breeder physiological requirements, productive status and bodyweight

March 2007