Dr Bruce R. Behrends
Agri-Tech
Litchfield, MN
U.S.A.
Managers of commercial egg production flocks are continuously challenged with trouble shooting unexpected egg production drops. These drops may be a large, rapid decline in production (Figure 1) or a lack of persistency where production declines at a rate faster than expected (Figure 2). These production drops cause significant economic loss and it is the duty of production management team to determine their causes so they can be eliminated in future flocks.
Many factors including nutrition and feeding, layer health, environment and management affect performance of layer flocks. The nutritionist and feed mill are responsible for providing properly formulated and mixed feed that will support optimum egg production and egg size at a minimum cost. Because layers in cages are solely dependent on the feed in the feed trough for their nutrition, errors in nutrient specifications, ingredient selection, formulation, mixing and delivery can result in production drops. This article provides guidelines to evaluate feed and nutrition as a variable in diagnosing egg production problems.
Characteristics of a good layer feed program
Well-designed and executed feeding programs are essential to maximum layer performance. In most companies, a professional nutritionist supervises the nutrition and feeding program. This person sets up feeding specifications, monitors performance and revises the program as necessary. A quality control program is necessary to monitor feed ingredient quality.
Most layer nutrition programs offer a wide range of nutrient levels. The nutritionist uses breeders' recommendations, research data, and industry experience to develop ration specifications. Considerations of feed ingredient quality, strain of layer and egg size requirements are used to refine the program. The education and professionalism of the nutritionist will contribute to the success of the program. Small differences in opinions may exist between professionals, but most of these differences are not large enough to have significant effects on production. The egg producer should select a nutritionist or nutrition company that is well staffed and experienced.
The program and formulas designed by the nutritionist are only as good as the available ingredients, the mixing system and the coordination of delivery. To execute the program, there must be good communication between nutrition and purchasing. If purchasing is considering changing suppliers for a specific ingredient, rations may need to be reformulated. Quality control information will be necessary to evaluate the new supplier.
The automated feed mill is a "Black Box". Neither feed ingredients nor finished feeds are seen during the mixing process. Ingredients are stored in bins, weighed with a computerized batch control system, mixed, stored in load-out bins and delivered in covered hopper trucks to feed tanks. Feed ingredients should be sampled and inspected upon delivery and feed being loaded in the truck should be inspected for obvious deviation from the norm. Because much of the mixing is under control of the batching system, it is absolutely necessary that formulas be verified upon entry. The batching system must be functioning as expected. A regular reconciliation of actual versus theoretical disappearance of ingredients is helpful to insure the accuracy of the batching system. A quality control program to analyze finished feed should be employed as an additional check.
Coordination between production and the feed mill are important to ensure that the correct feed is ordered in a timely manner and rations are changed when specified.
When feed is suspected as a problem
A typical scenario in egg production is a dramatic loss of eggs in one or more flocks in a multi-age production complex. When this happens, the production manager must work with the nutritionist, feed mill, veterinarians and flock managers to determine the cause of the problem. A systematic approach should be used to develop a case history. The first line of investigation is to determine if the flocks had feed, light, air and water (FLAW). If it was found, based on recording systems and talking with barn managers, that none of these items were off the norm, further investigation is necessary. The vaccination and health program should be reviewed with a veterinarian; blood samples should be taken and submitted for evaluation. If mortality increases, birds should be taken to a diagnostic lab for post-mortem examination.
Because feed and nutrition may be a problem, evaluation should be conducted immediately. A procedure to evaluate feed and nutrition is as follows:
Evaluate the formulation
Check nutrients – Is the original formula correct and does it provide nutrients appropriate for the flock at its level of production and feed intake?
Check ingredients – Are all ingredients including salt and vitamin trace mineral premix included?
Evaluate batching and mixing
Check the batching system – Was the formula transferred or entered to the batching system correctly? If batch size was changed, were all changes made correctly?
Check feed ingredient usage and reconcile usage – Does actual ingredient usage match up with the theoretical usage in the feed mill? Malfunctions in computer systems, turn heads or batching systems can result in the wrong ingredient being added. The computer will tell the operator if the material is moving from a certain bin, but it won't tell if it is the correct material.
Check the feed mill quality control results – Does the feed mill quality control program indicate that ingredients are meeting specifications and complete feeds are being mixed correctly? Is there any possibility of contamination of by-product ingredients?
Analyze feed samples
Obtain appropriate samples – The feed mill should sample each load of feed before it is delivered. To secure representative samples, several grab samples should be taken as the truck is being loaded or the load should be probed in several places. We have found that multiple samples are much more representative of the load than a single grab sample. Feed deliveries from two weeks prior to the problem should be analyzed. In most cases, it was the prior feed delivered rather than the feed in the bin at the time of the problem that caused the problem. Having retained samples at the mill or the production site is essential to trouble shooting in feed related production drops.
Specify analyses to be conducted and send samples to a qualified Lab – Samples should be sent to an experienced laboratory. For general troubleshooting, we recommend analysis for protein, calcium, phosphorus, and sodium. It is helpful for the lab if expected values are provided. This helps the lab personnel to adjust their sample size and dilution to provide a more accurate analysis. The lab should retain the samples for 30 days in case re-checks are needed to verify results.
Evaluate results and relate to performance problems
Evaluate analytical results – Because layer feed is not pelleted, it tends to segregate and variation in analysis will exist. Based on our experience, we have assigned analytical tolerances to these nutrients as outlined in Table 1.
A single grab sample is subject to wide variation and has wider tolerance compared to a blend of several samples. Calcium in layer feeds can be especially variable because of segregation of large calcium particles. The type of information that we obtain from analysis will help us determine if feed was mixed correctly. If several nutrients are out of tolerance in the samples, we need to evaluate the accuracy of the mixing and batching system.
Relate the analyses to performance problems - A summary of various nutrients and their effect performance follows:
Protein – Rate of lay and eggs size decrease if the layer flocks' protein intake does not meet the flocks' protein needs. The decreases are directly proportional to the amount of deficiency and the amount of time the deficient formula is fed. Because the hen's body maintains some protein reserve, errors in feed mixing concerning protein would have to be large to cause sudden production drops. A more common problem is rations that are slightly under their expected protein level due to feed ingredients not meeting expected protein levels. Regular analysis of ingredients and complete feeds are necessary to develop rations that meet expected nutrient levels.
Calcium – Layers react quickly to a ration without supplemental calcium. Shell quality deteriorates rapidly and eggs production ceases. Marginal deficiencies of calcium are another matter. Because calcium is an inexpensive nutrient and is extremely important for eggshell quality, most nutritionists use a wide safety factor when setting calcium specifications. A layer requires approximately 2 grams of calcium for an eggshell. A formula with 4% calcium consumed at 22 lbs/100/day will provide 4 grams of calcium.
Accurate analysis of calcium in layer rations is difficult. Because calcium is heavy, it tends to segregate as the feed is handled from mixing to distribution in the feeding system. Also, the use of large particle size limestone or oyster shell make obtaining representative samples difficult. As indicated in Table 1, our analytical tolerance for calcium for a "grab sample" of feed is plus or minus 40%. If multiple samples are taken by probing a truck or feed bin, the accuracy is improved. It is important to be aware of this inherent analytical variation when evaluating results of layer feed samples analyzed for calcium.
A common problem in high producing layers is a diagnosis of weak bones and beaded ribs even though correct levels of calcium and phosphorus are included in the feed. This condition may be due to lack of calcium intake rather than feed mixing or formulation. In the competitive environment of a layer cage, there are probably some birds that don't achieve a high enough feed intake during the onset of egg production. These birds probably become weak, go down in the cages and deplete their bone calcium before egg production ceases. These are usually the birds that we select for post-mortem examination. Current trends in layer nutrition are to increase calcium levels and use calcium sources with particle size and optimum solubility for layers.
Phosphorus – Because phosphorus is a major component of bone, phosphorus deprivation results in deterioration of bone strength. Nervous symptoms and cage layer fatigue may be involved in severe phosphorus deficiencies. Because phosphorus analysis is reasonably accurate, errors in feed mixing regarding phosphorus can be quickly diagnosed. Because animal by-products may vary in their phosphorus content, it is important to monitor suppliers through regular quality control information and adjust formulations if phosphorus contents of animal by-products change.
Salt – Deletion of salt in corn-soybean formulas that do not contain animal by-products results in rapid cessation of egg production. Corn and soybean meal are both extremely deficient in sodium. When a ration without salt is fed, the hen's physiological mechanism shuts off ovulation to prevent sodium loss through the egg. Because the effect is so dramatic, leaving salt out of corn-soy formulas has been used as a technique to molt layers. In a typical salt deficiency problem, otherwise healthy layers will go out of production and decrease feed intake. Because ovulation ceases, it will take 3 to 4 weeks for the birds to return to lay. Sodium deficiency is less dramatic in formulas containing meat and bone meal or other animal protein products.
At the other extreme, excessive salt will cause increased water consumption and wet droppings. A quick quality control test is to taste the feed. If evidence points to excessive salt, the suspect feed should be removed and replaced with correctly mixed feed. If the hens have access to water and correct feed is provided quickly, we haven't noted losses in egg production.
When salt analysis is specified, most laboratories analyze for the chloride ion and convert this value to salt by dividing by 0.6. (Salt if 60% chloride.) Because feed ingredients contain chloride, the analyzed salt content will be higher than the amount of added salt. Table 2 gives estimates of sodium and salt values from various types of layer formulas. We request sodium analysis if we suspect salt is the problem.
Because layers are highly sensitive to sodium levels, we recommend utmost care be used to make sure salt is added to the formula in correct amounts. An extremely reliable micro ingredient system or adding salt by hand is recommended rather than adding salt through the main batching system.
Conduct further analyses if needed
Vitamins and trace mineral – Vitamins and trace minerals are usually added to layer rations as low inclusion rate premixes. Deletion of the premix is a potential cause of egg production problems. The severity of the problems is proportional to the length of deletion. Riboflavin and Vitamin D are the vitamins most likely to become deficient in a short time. Lack of riboflavin results in reduced egg production. Layers produce soft-shells and shell-less eggs within 7 days of being fed a ration devoid of Vitamin D. Continued lack of Vitamin D results in cessation of egg production. Commercially available water-soluble Vitamin D products have been successful in reversing the symptoms in laying flocks where Vitamin D deficiency has occurred. Trace minerals have less of an effect on egg production with manganese and zinc being first limiting.
Because vitamins and trace minerals are added at low levels, accurate analysis is difficult. Vitamin A (retinol) has the lowest limits of detection and is not found in feed ingredients. Analysis for this ingredient can be conducted to determine if the premix has been added to the feed. Other techniques to determine if the premix has been added are the use of microtracers or colored vitamin products that can be detected by microscopic analysis.
If it is determined that the premix has been added to the feed and vitamin deficiencies are reported in the diagnosis, specific vitamin analysis can be conducted on premix samples. Premix samples should be analyzed at a laboratory experienced in vitamin analysis. It is helpful to provide the laboratory with expected amounts and the manufacturer of the Vitamins A and D in the premix. Because different vitamin manufacturers use different protective coating on their product, it is important to use appropriate lab procedures for the product in question.
Molds and mold toxins – Mold and mold toxins are sometimes implicated in egg production drops. Fusarium molds may grow in corn in the field in wet, cool years and may produce T-2 toxin. Aspergillus molds, which produce aflatoxin, are a result of hot, dry growing conditions. However, both of these molds can grow in corn without their associated toxins present. Aflatoxin has been reported to cause decreased egg production, reduced hatchability and immunosuppression in layers. T-2 toxin has been reported to cause decreased egg production and thin eggshells. Although T-2 toxins have been reported to cause mouth lesions, they are not the only factor. Daft et.al. (Avian Diseases 45:349 2001) found a greater incidence of mouth lesions with meal vs. pelleted feed. Other factors reported to cause mouth lesions are stress from the onset of egg production or disease. More mouth lesions are found with cage and drinker design prevents the hen from rinsing fine particles of feed from the mouth.
In trouble shooting egg production drops, mold toxin analysis should be conducted only when other variables have been eliminated. Because of the complex nature of mold toxins, their analysis and their effects on egg production, it is wise to work with a consultant knowledgeable in this area rather than routine analysis for a variety of toxins.
Summary
These are some recommendations for preventing and trouble shooting feed related egg production drops:
The best defense is a good offense: the feeding program should be designed and executed by competent people. A routine quality control program in the feed mill will help ensure quality ingredients and accurate formulas.
Save feed samples: We recommend labeling and saving samples from each feed delivery for three months. These samples can be stored in garbage cans to prevent damage from rodents. If the feed is implicated in a production drop, it is extremely important to have samples of feed delivered and consumed prior to the drop. Feed samples taken from the hopper at the time of the production drop may not be the delivery that was associated with the problem.
Conduct routine analysis on feed samples associated with production drops: We recommend analyzing for protein, calcium, phosphorus and sodium. Be aware of analytical variations associated with the method of sampling (Table 1). If the analytical values are not within tolerances have them rechecked by the lab to verify results. In the meantime, review formulas, batching, and delivery procedures to insure accuracy. If the recheck indicates results are out of tolerance, determine the cause and correct the problem. Set up systems to prevent the problem from happening again.
If the nature of the problem points to vitamin or trace mineral deficiency, verify that the premix was included by analyzing for microtracers or conducting Vitamin A analysis. If the premix was included and vitamin deficiencies are implicated, have the premix analyzed for suspect vitamins at a qualified laboratory.
If molds or mold toxins are implicated, be aware of the difficulty of their analysis. Knowledge of local crop conditions or information from State laboratories may be helpful in determining which specific molds or toxins to suspect. If mold toxin analysis is conducted, work with a laboratory that specializes in this area.
If it is determined that feed is not the problem, continue to work with production personnel and veterinary professionals to identity the cause.
From Proceedings of the "Midwest Poultry Federation Convention", St. Paul, Minnesota, U.S.A.
