The effect of feed physical form on commercial layer nutrition

Water is an essential nutrient for life. In the body, water performs several biologic functions in addition of being a fundamental constituent of both intra-cellular and extra-cellular fluids. Water is the most abundant component in live beings, and its content varies depending on animal species, body fat levels, and animal age.

Body water content in the hen varies depending mainly on bird's age, but generally it represents  ̴ 85% of live weight during the first week of life,  ̴ 70% by week 4, and  ̴ 60%, in the adult stage. Water represents nearly 65% of egg weight (Gama et al., 2008).

Regardless of ambient temperature variations birds, as homeotherms, have the ability to maintain body temperature. Factors leading to increased body temperature beyond certain limits due to either environmental or physiological conditions, can be lethal for the bird (Yahav et al., 2000). Therefore, water plays an important temperature-regulating function thus being extremely beneficial for birds, particularly in hot environments (Forbes, 2003).

Birds typically receive water and feed separately, different from swine in certain production stages, when feed and water are mixed together resulting in a paste or a slurry that are better accepted by animals. Historically, the addition of water to industrial poultry diets has not been recommended, due to the difficulties in implementing such practice. Even though, some workers have recently reported results from this feeding regime (Forbes, 2003).

Due to the high level of specialization that the poultry industry has reached, novel nutritional alternatives need to be proposed, in order to make the most of birds' full genetic potential. One major challenge today is assuring that birds consume the necessary amount of ingredients for maximum performance (Araújo, 2003).

In layers, feed intake is closely related with water intake, so that any problems affecting water intake will impact feed intake, and vice versa (Gama et al., 2008). Administering a moist diet to birds can result in improved production and performance levels.

The objective of this study was to evaluate different feed physical forms in commercial layers by the addition of various water inclusion levels, on productive performance parameters.

The experiment was carried out in the experimental poultry farm, College of Veterinary Medicine and Animal Husbandry, Sao Paulo State University (USP), Pirassununga campus, SP, Brazil. One hundred and ninety two (192) Hyline W-36, 48-week-old hens were distributed using a completely-at-random design, with 6 treatments (0, 10, 20, 30, 40, and 50% water inclusion in the feed) and four 8-bird repetitions. The basal diet was formulated with corn and soybean meal, in accordance with the levels recommended by Rostagno (2005), as shown in Table 1.

Table 1. Nutritional composition of the basal diet

The following performance parameters were recorded: feed intake (g/bird/day), feed conversion rate (g feed/g egg) and egg production (% eggs/bird). On the last two days of each period daily egg production was collected in order to determine egg weight/egg mass (g), specific gravity, eggshell thickness, and percent eggshell.

Every day, animals were fed 100 g feed/bird/day in order to facilitate water addition at the proportions established for each treatment. Feed leftovers were weighed on the following morning. Feed intake was determined daily by deducting leftovers from feed served. Results were expressed based on dietary dry matter intake.

Specific gravity was determined as recommended by Moreng and Avens (1990). Eggshells were dried at ambient temperature for 7 days then weighed, in order to estimate eggshell %. Eggshell thickness was measured at egg equator using a micrometer with a 0.01 mm precision and a 0.01 - 10.00 mm range.

Egg mass (g/bird/day) was estimated at the end of each experimental period by multiplying mean weight times mean egg production.

Body temperatures were recorded weekly using an infrared thermometer in 3 body regions (comb, back, and legs) of two animals per repetition. In addition rectal temperatures were also recorded. All temperatures were measured always at the same time in the day in order to avoid variations derived from ambient temperature.

Experimental data was analyzed using the SAS software (2001), and the means were compared using Tukey's test (P<0.05).

Results showed that as water inclusion levels in the feed were increased, feed conversion rates decreased. Also, hens fed the diet with 30% added water had increased egg production as compared with the controls (Table 1).

Table 2. Mean feed conversion rate (FCR, g feed /g egg) and egg production (EP, % eggs/bird) in commercial layers fed diets with various levels of water inclusion

No statistically-significant differences (P>0.05) were observed in egg weight, eggshell thickness, % eggshell or egg specific gravity. Nevertheless, treatments with water inclusion resulted in positive effects on egg mass (Table 3).

Table 3. Egg quality parameters: egg weight (g), egg mass (g), eggshell thickness (mm), % eggshell, and egg specific gravity

Body temperature evaluations showed that, at the water inclusion levels analyzed, no effect was observed of moist diet on body temperature in commercial layers (Table 4). The poultry industry has experienced major transformations in recent years. Modern layers are now more precocious and feed efficiency has improved, resulting in larger amounts of eggs with lesser feed intakes. Therefore, nutritionists have looked at new nutritional alternatives aiming to fulfill bird requirements through adequate feeding management practices. The use of moist or even fluid diets in swine has become more and more popular in recent years. Nevertheless, this practice in poultry has been limited and, in addition, only scarce information exists with this regard in commercial layers. In accordance with Yalda and Forbes (1995), and Forbes (2003) the use of moist feed in birds can play an important role both nutritionally and economically by reducing feed cost due to improved nutrient utilization.

Table 4. Body temperatures of commercial layers fed a moist diet during 56 days

This research demonstrated that feed physical form, resulting from the inclusion of various water levels, is a viable alternative for commercial layers. Moist feed resulted in improved animal performance and increased egg production.

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