COCCI Nutrition: Cocci vaccination enables more flexible diet

Review your program to minimise coccidiosis pressure and maximise control

Dr. José Ignacio Barragan, Poultry Veterinarian and Independent Nutritional Consultant, Spain

As long as commercial poultry operations have been in existence, nutritionists have tried to appraise the impact of feed nutrients and the changing dietary needs of broilers. They have also sought to find and control anti-nutrition factors present in the feed.

In many cases, nutritional needs are linear but diminish as chickens grow older. In other words, as birds age, the dietary contribution of the feed differs and, in general, diminishes.

An important factor to consider is the chicken's sensitivity to the diet's energy level. There is practically a linear relationship between energy levels in the diet and the feed conversion index. Since the feed conversion index is the most important factor affecting the cost of broiler production, it is generally the first element defined by nutritionists. Once this value is established, remaining nutrients are defined in terms of the estimated consumption according to the energy level and the needs of the production phase.

Another important dietary decision is the length of time that each feed type should be used. First consider the number of feed types that the mill can manufacture based on its capacity and the logistics involved. In general, feed mills usually handle three different broiler feed types and, under certain circumstances, four, but it is usually difficult to increase this amount. Generally, the more types of feed that can be manufactured, the better the nutritional needs of chickens can be met. On the other hand, the mill's capabilities are usually considered before cost optimization.

Once the amount of different broiler feed types is established, the age limits for the use of each feed must be determined. In theory, this should be the most economical feeding program. In reality, though, the feeding program is significantly influenced by the anticoccidial program.

Traditional programs

For years in Spain and many other countries with a long tradition of poultry farming, the coccidiosis control program consisted of a chemical product, which generally was nicarbazin during the first weeks followed by an ionophore (e.g., monensin, salinomycin). The optimum period of time that nicarbazin can be used is 21 days, since less time reduces its efficacy, while more increases the risk of growth depression; in addition, different regulations require that this anticoccidial be withdrawn a certain number of days before slaughter.

As a result, the more universally used formulation programs have had a starter feed until 21 days of age, a grower feed until a few days before slaughter (depending on the regulations) and a withdrawal feed until slaughter. This is the way it has been done, even though it may not be the most technically or economically ideal program.

The situation differs when chickens are vaccinated to control coccidiosis. The length of time that finisher feed is used is not determined by concerns that chickens will suffer from coccidiosis in the late "and expensive - grow-out period. These new circumstances also allow feed to be formulated for times that the chicken's intestines are battling Eimeria introduced by the vaccine, which is the period between 15 and 25 days of age.

Vaccinated birds

Feeding programs for chickens vaccinated against coccidiosis should have three different objectives. They should:

Develop the immunological system. The feed should promote growth and good immunity system function.

Provide birds with the best defense for replication periods by providing good digestibility and, when possible, preventing other complicating factors such as necrotic enteritis.

Utilize the resistance to coccidiosis created in birds to maximize growth for the lowest cost possible in the final grow-out period.

This triple objective can be achieved more easily with a feeding system that's different from the one used now. It would provide the use of:

An "impulse" (pre-starter) feed from 0 to 14 days of age
A highly digestible feed from 15 to 30 days
A technically and economically useful feed from 31 days until slaughter.

Field trials

To test this new diet, trials were conducted at one of the most prestigious experimental farms in Spain. In one trial, 4,500 Hybro males were used. The birds were divided into three groups: those that received an anticoccidial, those that did not, and those that were vaccinated against coccidiosis. Among each of the three groups, half received the conventional diet and half received an alternative diet (Table 1).

The conventional feeding program consisted of the following feed types:

P1: Starter. From 0 to 21 days, with 3020 Kcal; 23.6% total protein and 1.1% of available lysine.
P2: Grower. From 21 to 42 days, with 3250 Kcal; 23% protein and 1.05% of available lysine.
P3: Finisher. From 43 to 49 days, with 3250 Kcal; 21.9% protein and 0.95% of available lysine.
P1 feed was given as crumbs and P2 and P3 as granules.

The alternative feeding program consisted of the following feeds:

P0: A pre-starter from 0 to10 days, with 3000 Kcal; 24% protein and 1.3% of available lysine.
P1: A starter from 11 to 21 days, 2850 Kcal; 23% protein and 1.04% of available lysine.
P2: A grower.
P3: A finisher.

Feeds P2 and P3 are identical to the conventional feeding program. In the alternative program, all diets were given in granular form. The P0 and P1 granules were smaller to accommodate smaller birds.

The goal of the alternative diets was to ensure the best possible start for chickens and to facilitate digestibility during the first 21 days of age with a less concentrated feed. Results for the period from 0 to 10 days are presented in Tables 2, 3 and 4.

The results show that body weights at 10 and 21 days and at the end of the trial are higher in birds fed with the program consisting of a pre-starter and a more digestible starter compared to those fed the standard program. These differences are significant in all three production periods as well as in the three coccidiosis control programs (anticoccidial, no anticoccidial and vaccinated). The largest appreciable difference in numbers regarding final bodyweight was seen in the vaccinated group.

The feed conversion ratio tends to be slightly worse, though not truly significant, in chickens fed the alternative program due to higher feed consumption. However, this slight increase in feed consumption does not limit the opportunity for final weight increase using the alternative program. The slightly increased cost of feed with the alternative program for the initial stages is due to the higher concentration of amino acids and improved characteristics of the feed ingredients.

To reduce the cost of feed and better utilize the immunity obtained against coccidiosis in vaccinated chickens, it is possible to modify the duration of the "third stage" feed (generally known as "withdraw" feed because it coincides with the withdrawal period of the growth promoters and coccidiostat). Studies by Saleh, Watkins and Waldrop have shown that, in high bodyweight chickens, a diet with the characteristics of a withdraw feed can be used for longer periods without affecting the technical results (Table 5).

We can see that increasing the use of withdraw feed in birds of medium bodyweight up to 14 days reduces the average weight in birds that received only grower, but not withdraw feed. However, when the test is repeated in heavy weight birds, there is no difference between chickens that consumed 7 or 14 days of withdraw feed.

With these results in mind, a trial was repeated at the same location of the first trial. The results for chickens with different withdrawal periods are compared in Table 6.

A standard feeding program containing anticoccidials is compared with a series of alternative programs in vaccinated chickens consuming a first feed with two variations (normal and higher digestible, with lower levels of energy and protein/amino acids) and a second and third feed of variable duration, increasing the withdrawal period (Table 7).

The results show there is no difference between chicken weights regardless of the withdrawal period used or the feed conversion rate, even though it is numerically better in chickens that received the feed from 35 days of age. This test was unable to establish differences between the chickens that received the two different first stage feeds, even though, numerically, the weights of chickens fed the more digestible, but less concentrated, feed were slightly lower. Neither was it possible to find differences between the processing results among chickens in the different treatment groups, nor in the values of litter quality or in Eimeria oocysts counts.

In the end, there were no significant differences between the results of the vaccinated and the anticoccidial-fed control groups.

From these trials, we can conclude that in chickens vaccinated against coccidiosis, it is possible to extend the time that finisher (withdrawal) diets are used if final weight will be higher than 2.4 kg (5.28 lbs), without having detrimental effects.

On the other hand, a starter diet with special characteristics may allow the birds to have a better "start" with improved resistance during the period of higher Eimeria replication.

Conclusion

Using an "impulse" starter feed, a highly digestible second stage diet fed between 15 and 25 days of age along with a finisher diet fed for a longer period of time than usual can better meet the needs of chickens vaccinated against coccidiosis.

Once liberated from the limits established by the use of a traditional anticoccidial program, poultry producers can have more freedom designing feed formulas and programs. Alternative programs might also benefit vaccinated chickens by providing them with better intestinal health, without increasing the cost of the feeding program.

Source: CocciForum Issue No.8, Schering-Plough Animal Health.