Abstract
The objective of this study was to evaluate the effect of reducing the crude protein (CP) with the use of amino acids in diets with the same amount of calories anddifferent levels of soybean oil (SO) for finishing pigs kept in two different ambient temperatures. A total of 120 barrows (initial weight of 68.0±1.9 kg) were utilized for the experiment. The design was of randomized blocks in a 2 × 3 × 2 factorial arrangement (two levels of CP, 16.2 and 13.7%; three levels of SO, 1.5; 3.0 and 4.5%; and two ambient temperatures, 19 and 31 oC), totaling twelve treatments with five replicates for thirty days. The heat reduced feed intake (FI) of the animals, regardless of the levels of CP and SO used, and reduced weight gain (WG) in diets with reduced CP and SO or higher SO. The increased level of CP and SO improved feed conversion (FC) when the animals were kept in thermoneutral environment and given a diet with higher protein content. The reduction in CP increased FI only in the thermoneutral environment. In the heat, WG increased in diets with higher levels of SO, without influencing FC. The manipulation of diet and temperature did not affect most carcass traits. The SO reduced backfat thickness (BT) only in diets with high CP and animals kept in thermoneutral environment. The reduction of CP increased the BT only in diets with high content of SO, both in hot and thermoneutral environments. Heat reduces FI and the inclusion of SO does not improve performance or carcass characteristics in these conditions. The reduction in CP improves WG only in diets with high oil content; however, it increases BT. In thermoneutral environment, increasing the SO is beneficial for performance and carcass characteristics, except when diets with reduced CP are used. The reduction in CP improves performance only in diets with low oil content.
Highlights
In tropical countries, one of the challenges of production is the high temperature and humidity inside the facilities, which limit well-being and high productivity
The objective of this study was to evaluate the effect of reducing the crude protein (CP) with the use of amino acids in diets with the same amount of calories anddifferent levels of soybean oil (SO) for finishing pigs kept in two different ambient temperatures
Within the wide range of ambient temperature, there is a range in which the body temperature remains constant with minimal effort of thermoregulatory mechanisms, in which there is no sensation of cold or heat for the animals, called “Thermal Comfort Zone” or “Thermoneutral Zone.”
Summary
One of the challenges of production is the high temperature and humidity inside the facilities, which limit well-being and high productivity. Within the wide range of ambient temperature, there is a range in which the body temperature remains constant with minimal effort of thermoregulatory mechanisms, in which there is no sensation of cold or heat for the animals, called “Thermal Comfort Zone” or “Thermoneutral Zone.”. When the environmental temperature rises above the upper limit of the Comfort Zone, the thermoregulatory system is activated to maintain thermal equilibrium between the animal and the environment, which represents an extra effort and, changes in productivity. Pigs kept in thermo neutral environments tend to express their maximum genetic potential. Pigs living in hot environments present greater body length. According to Noblet et al (2001), this represents the adjustment mechanisms that facilitate the heat dissipation through increased body surface area
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