Abstract
The objective of this study was to determine the energy values of soybean oil (SBO) and tallow (T) combined in different ratios, and to evaluate their effects on the performance, body composition, and serum lipid levels of starter broilers. In experiment I, a digestibility trial was performed to determine the energy value of the SOB and T mixtures using 100 12 - to 21 -day-old broilers. In experiment II, 930 one-day-old broilers were used. Treatments consisted of the inclusion of 4% SBO and T inclusions at the following ratios: 0:100, 25:75, 50:50, 75:25, 100:0. Each treatment included six replicates. In experiment I, AME and AMEn linearly increased (P<0.01), as SBO participation in the mixture increased. In experiment II, the different lipid ratios quadratically influenced (P<0.01) body weight and weight gain at 21 days of age, increasing up to the ratio of 65.87:34.13. Serum lipids linearly decreased (P<0.05) as SOB inclusion in the diet increased. It was concluded that AME and AMEn of SBO and T at ratios of 0:100, 25:75, 50:50, 75:25, and 100:0 were 7.882 and 7.542, 8.384 and 8.076, 8.701 and 8.385, 8.801 and 8.727, and 9.478 and 9.271 kcal/kg, respectively. The best performance with no detrimental effect on carcass yield was obtained with the mixture of 75% SBO with 25% T. The highest dietary soybean oil level reduced serum lipid levels of 21-day-old broilers.
Highlights
The use of vegetable oils and animal fats in broiler diets has been beneficial for poultry production
It was concluded that AME and apparent metabolizable energy corrected for nitrogen (AMEn) of soybean oil (SBO) and T at ratios of 0:100, 25:75, 50:50, 75:25, and 100:0 were 7.882 and 7.542, 8.384 and 8.076, 8.701 and 8.385, 8.801 and 8.727, and 9.478 and 9.271 kcal/kg, respectively
The main factor that influences the nutritional value of fat sources is digestibility, which is affected by fatty acid saturation degree, carbon number in the chain, free fatty acid concentration, position of the glycerol molecule, as well as the interaction between saturated and unsaturated fatty acids (Rener & Hill, 1961; Ketels & DeGroote, 1989; Dvorin et al, 1998; Leeson & Summers, 2001)
Summary
The use of vegetable oils and animal fats in broiler diets has been beneficial for poultry production. They often present higher than expected biological value, increasing dietary metabolizable energy, which usually results in higher growth rates and better feed efficiency. The main factor that influences the nutritional value of fat sources is digestibility, which is affected by fatty acid saturation degree, carbon number in the chain, free fatty acid concentration, position of the glycerol molecule, as well as the interaction between saturated and unsaturated fatty acids (Rener & Hill, 1961; Ketels & DeGroote, 1989; Dvorin et al, 1998; Leeson & Summers, 2001). Dvorin et al (1998) showed that the energy values of fat sources by mixture with vegetable oils due to interaction between saturated and unsaturated fatty acids, provided the fatty acids present in the mixture are balanced. Due to its high energy density, fat synthesis and deposition in these tissues are metabolically costly to the birds, in addition of being an undesirable and expensive pathway of dietary nutrient partition
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