The use of moist diets for broilers

Water is the most abundant component of live beings. Percent bodily water content varies depending on animal species, body fat, and age. In broilers, maintaining the level of body water within certain limits is essential for the regulation of physiological functions, such as cardiovascular activity. It is important to remember that water consumption/excretion in the baby chick (in relation to body weight) are larger than those in the adult bird, since major body water losses during the first weeks of life without increased water intake can have adverse repercussions in the flock, mainly due to heat stress (Butolo, 2005). The amount of water that a bird drinks throughout its life span is somehow higher than twice the amount of feed consumed. If not enough water is available, feed intake is reduced and performance is adversely affected (Boleli, 2002). Early in its life, the bird is extremely sensitive to dehydration (Butolo, 2005). The only element which deficiency is more critical than that of water is oxygen. Potable water is vital for bird development. If 10% body water is lost due to dehydration, bird performance is reduced, while if water loss reaches 20%, death can occur. In broiler production, the balance in the water-to-feed intake ratio is extremely important. The use of moist diets for broilers has shown promising results on feed intake, feed efficiency and nutrient retention (Yalda y Forbes, 1995). The purpose of this study was to evaluate the administration of diets with different moisture contents to broilers in the period of 1 to 49 days of age.

Seven hundred and sixty eight Cobb®, male, broiler chicks, were used. Birds were distributed using a completely-at-random experimental design including 6 treatments (0, 10, 20, 30, 40, and  50% water inclusion in the feed) with 4 repetitions of 32 birds each, and 4 feed phases (pre-starter, 1 - 7 days; starter, 8 - 21 days; grower, 22 - 42 days; finisher, 43 - 49 days). The total feeding period lasted for 49 days. Feed and water amounts were calculated based on Cobb intake charts to facilitate the addition of water to the diet and avoid losses. The experimental feeds were formulated using corn and soybean meal. Nutritional levels are described in Table 1.

Table 1. Percent composition and calculated nutritional values in the experimental broiler diets

In order to determine feed amounts to be offered, the Cobb broiler management manual was used. Diets were offered in the morning, and leftovers were removed on the following day, in order to avoid potential fermentation, evaluate feed dry matter, and calculate feed intake.

Both FI and FCR were recorded at 49 days (experiment completion). FI in treatment group 0 (no water inclusion) was determined based on total feed intake in each experimental period and weighing feed leftovers at the end of the period. FI in all other treatments (10, 20, 30, 40, and 50% water inclusion) was determined by weighing the feed then deducting feed leftover weight. During the experiment, water intake was also determined. For this purpose, water was weighed daily at serving time using trough-type drinkers. Water amounts were adjusted daily in accordance with intake. Water leftovers were weighed at drinker washing time, then deducted for water intake calculations. Water intake determinations did not take into account the amounts of water added to the feed.

Bird body temperatures were measured weekly in two birds per repetition, always at the same time, in the following regions: head, back and legs.

At 7 and 21 days, two birds per repetition were killed and 2 cm sections from the proximal duodenum of each animal were collected for histological evaluation. After preparing microscope slides, 30 villus height determinations and 30 crypt depth determinations were performed for each duodenum sample collected, using an Axioplan II Zeisssendo microscope. In addition to slide observations. micro-photographs were also obtained in order to measure villi height and crypt depth. Experimental data was analyzed using the SAS software (2001), and treatment means were compared using Tukey's test, at a 5% probability level.

Other workers have reported that birds fed a moist diet showed increased feed intake as compared with those fed a dry diet, during the last experimental week (Yalda and Forbes, 1995). A separate commercial trial compared the performance of birds fed a moist diet with those receiving a pelleted dry feed. Both FI and WG were lower in the birds with the moist diet, while a 5% FCR increase was observed (Preston et al., 2000). Table 2 shows no statistical differences among treatments regarding water intake and WG, with a significant FI increase when 30% water was included in the feed (P<0.05).

Table 2. Performance parameters in broilers fed diets with different levels of water inclusion during the period of 1 - 49 days of age

As far as body temperature is concerned, no effect of the moist diet was observed on broiler temperature (Table 3), which can be explained by the fact that the experiment was performed during fall/winter, when the ambient temperatures were within birds' thermal comfort zone (Araujo, 2003).

Table 3. Body temperatures in 49-day-old broilers fed various physical form diets

When looking at duodenum villi height, an effect (P<0.05) can be seen at 7 and 21 days of age, due to the inclusion of water in the diet. This can be explained by the fact that digestive enzymes penetrate feed particles more readily in the moist feed, thus resulting in improved nutrient retention (Yalda and Forbes, 1995). Likewise, gastric juices also penetrate the feed more easily (Forbes, 2003).

Table 4. Histological morphology: villi height (mm) and crypt depth (mm) in the duodenum of broilers fed a moist diet at 7 and 21 days of age

This study showed that the inclusion of different levels of water in the diet of broilers had no positive effect on animal performance or body temperatures. Nevertheless, the inclusion of 50% water resulted in improved duodenum villus height.

Araujo LF. Nutrição pós-closão: aspectos teóricos e práticos. 2003. In: Simpósio sobre Nutrição de Aves e Suínos. Anais ... Campinas, pp.183-210

Boleli IC. 2002. Estrutura funcional do trato digestório. In: Fisiologia Aviária Aplicada a Frangos de Corte. Macari M, Furlan RL, Gonzales E. editores. 3^a Ed. Jaboticabal: FUNEP/UNESP, pp.75-95.

Butolo JE. 2005. Bebedouros - Tipos - Vantagens e Desvantagens. Disponível em: http://www.avisite.com.br/cet/6/01/index.shtm.

Forbes JM. 2003. Wet food for poultry. Avian and Poultry Biology Rewies 14(4):175-193.

Preston CM, Mccracken KJ, McaliIster A. 2000. Effect of diet form and enzyme supplementation on growth, efficiency and energy utilisation of wheat-based diets for broilers. British Poultry Science 41:324-331.

Yalda AY & Forbes JM. 1995. Food intake and growth in chickens given food in the wet form with and without access to drinking water. British PoultryScence 36:357-369.