本帖最后由 小馬哥 于 2012-12-28 09:59 編輯
The correct nutrition of laying hens Date:2010-10-25 By Kristjan Bregendahl, Ph.D.
The proper nutrition of laying hens is essential to ensure birds, and the business, are at peak performance.
file:///C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\ksohtml\wps_clip_image-12018.png Development of feed intake with age and suggested diet phases. Eash diet is formulated to provide the breeder-recommended grams or milligrans, given the observed feed intake of the hens. Correct nutrition plays a major role in attaining the modern laying hens’ genetic potential for egg production and egg quality. Furthermore, the cost of feed accounts for some 65 to 75% of the cost of producing an egg. Therefore, the nutrition program is critical in determining the overall profitability and success of the egg-production business.
Feeding the laying hen starts with feeding the pullet
It is important to develop a healthy, good-quality pullet with sufficient body reserves to sustain the high demands of egg production. Mistakes made during the growing period are difficult, if not impossible, to correct in lay, so the pullet nutrition program should be viewed as an investment in the laying period.
During grow, the body weight and body weight uniformity are the best tools to manage the nutrition program and ensure correct development of the pullets. Therefore, the body weight of the pullets should be monitored by weighing the birds regularly. The most successful pullet producers begin weighing the pullets at 2 weeks of age and weigh them every week thereafter. The frequent body weight measures are necessary to be able to correct problems in grow and are also needed to help determine when grower diets should be changed.
Diet changes in grow should be based on body weight rather than age. If, for instance, a diet change is scheduled at 3 weeks of age, but the body weights of the pullets are below the 3-week target weight, the diet should be fed a week or two longer, until target-weight-for-age is met. In contrast, diets can be switched sooner if the pullets are above the target weight.
If pullets are failing to gain body weight at the desired rate, the diet specifications should be compared to the breeder’s recommendations. If there are no obvious differences that can explain the reduced growth rate (and no problems in management or health status is evident), then the rate of body weight gain can be increased by increasing the diet’s energy concentration. In hot weather, when feed consumption is low, the dietary contents of nutrients (amino acids, fatty acids, minerals, and vitamins) may need to be increased as well to increase growth rate.
Feeding the laying hen
Knowing the feed intake of the flock is critical. The nutrition recommendations for laying hens are typically based on supplying a given amount of nutrients per day to each hen, expressed in milligrams or grams per day. One must therefore know (or accurately estimate) the hens’ daily feed intake in order to calculate the dietary percentage inclusion of each nutrient.
For example, with an observed feed consumption of 110 g/day and a recommended daily calcium intake of 4.4 g/day, the dietary calcium concentration should be 4.0%: (4.40 g Ca needed × 100) / 110 g feed consumed = 4.0% Ca in the diet Should the daily feed consumption decrease to, say, 105 g/day because of hot weather or other factors, the hens fed the above diet would consume only (105 g × 4.0% =) 4.2 g calcium. Importantly, the same decrease in daily intake is also true for other nutrients and energy. As a result, eggshell quality, egg weight, and egg production will decrease unless the diet density is increased to provide the recommended amounts of energy and nutrients given the lower feed intake.
Suggested diet program for laying hens
The first diet that is fed as the hens start laying eggs is critical to sustain body weight gain, to meet the high demands of egg production, and also to ensure a long productive life of the hen. At this time, the hens’ feed intake is relatively low and if the hens cannot obtain sufficient energy and nutrients from the diet, they will use body reserves to sustain egg production. When the body reserves are (almost) depleted, egg production stops and the classical post-peak dip in egg production follows. Therefore, the first layer diet should be fairly concentrated, often necessitating relatively high inclusion levels of oil, digestible amino acids, calcium, and available phosphorus. Because of the high nutrient density of the first diet, it is relatively expensive when compared on a price-per-1000-kg basis. However, the diet is only fed for a short time and only little of the diet is consumed because of the relatively low daily feed intake. Therefore, the actual cost of feeding Diet 1 is low and, importantly, it ensures adequate energy and nutrient intake to ensure a high peak, prevents depletion of body reserves, and an excellent persistency of lay.
Diet 1 is fed from start of lay (Figure 1), but the diet phase is relatively short. The diet is formulated for a relatively low feed intake, which is as low as economically and practically feasible (the exact feed-intake value depends in part on the individual farm and economics). The diet is fed until the observed feed consumption has increased by 5 to 10 g/day, which typically occurs around 26 to 27 weeks of age. Often the first diet is fed until 45 to 50 weeks of age, and does not take the dramatic changes in feed intake during this time into consideration.
When the flock’s feed intake has increased by 5 to 10 g/day, Diet 1 can be reformulated to take advantage of the now higher feed intake. Diet 2 should be formulated with similar—or perhaps slightly less (0.10 MJ/kg or 25 kcal/kg)—energy as that of Diet 1 to deliver the same milligrams or grams of nutrients per day as that of Diet 1, given the differences in feed intake. That means that Diet 2 is less concentrated and, therefore, less expensive. If desired an aggressive egg-weight control program can be begun at this age by reducing the hens’ intake of amino acids and added fat. The next diet is formulated after the feed intake has increased another 5 g/day, which typically occurs around 36 to 37 weeks of age, and is therefore slightly less concentrated than Diet 2. The feed intake usually does not change much after this time (Figure 1), so subsequent diet changes (to Diet 4) are governed mainly by controlling egg weight (by reductions in amino acid content and added fat), maintaining eggshell quality (by increases in calcium and decreases in phosphorus). That said, these diets should be reformulated to avoid under- or over-feeding the hens if the feed intake changes. To avoid too abrupt changes in diet formulation that may cause large, temporary decreases in feed consumption, changes in energy content among different diets should be done in steps of no more than about 0.10 MJ/kg or 25 kcal/kg per week. Similarly, nutrient contents should not change more than about 5% per week (e.g., from 0.90% lysine to 0.86% lysine), meaning that multiple diet changes over several weeks are needed if larger decreases in energy or nutrients are desired.
Kristjan Bregendahl is a nutritionist, and director of technicalsService at Hy-Line International, US. Updated:Sep 15, 2011This article appeared in Poultry International, December 2010. ©Copyright 2012, All Rights Reserved.
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