Influence of the inclusion of co-products of the soy oil industry in poultry diets on nutrient digestibility, growth performance, and production

The general objective of this thesis was to study the effect of inclusion of different co-products from the bioenergy industry in poultry diets on nutrient digestibility, growth performance, and production. To this end, the influence of glycerin, lecithins, and re-esterified oil from soy oil industry, were developed in three studies. In the first study (chapter 2), the influence of source and level of inclusion of raw glycerin (GLYC) in the diet on growth performance, digestive traits, total tract apparent retention (TTAR), and apparent ileal digestibility of nutrients was studied in broilers from 1 to 21 d of age. There was a control diet based on corn and soybean meal and 8 additional diets that formed a 2 × 4 factorial with 2 sources of GLYC and 4 levels of inclusion (2.5, 5.0, 7.5, and 10%). The GLYC used were obtained from the same original batch of soy oil that was dried under different processing conditions and contained 87.5 or 81.6% glycerol, respectively. Type of processing of the GLYC did not affect any of the variables studied except DM and organic matter retention (P < 0.05) that was higher for the 87.5% glycerol diet. From d 1 to 21, feed conversion ratio (FCR) improved linearly (L, P ≤ 0.01) as the GLYC content of the diet increased, but ADG was not affected. On d 21, the relative weight (% BW) of the liver and the digestive tract increased (L, P < 0.01) as the level of GLYC in the diet increased, but lipid concentration in the liver was not affected. The TTAR of DM and organic matter increased quadratically (Q, P < 0.05) and the AMEn content of the diet increased linearly (L, P < 0.01) with increases in dietary GLYC. Also, the apparent ileal digestibility of DM (L, P < 0.05; Q, P = 0.07) and gross energy (L, P < 0.01) increased as the GLYC content of the diet increased. It is concluded that raw GLYC from the biodiesel industry can be used efficiently, up to 10% of the diet, as a source of energy for broilers from 1 to 21 d of age and that the energy content of well-processed raw GLYC depends primarily on its glycerol content. In a second study (chapter 3), the effects of the inclusion of raw glycerin (GLYC) and lecithin in the diet on egg production, egg quality and total tract apparent retention (TTAR) of dietary components was studied in brown egg-laying hens from 23 to 51 wk of age. The experimental design was completely randomized with six diets combined as a 2 × 3 factorial with two levels of GLYC (0 vs.70 g/kg) and three animal fat to lecithin ratios (40:0, 20:20 and 0:40 g/kg). Each treatment was replicated eight times and the experimental unit was a cage with ten hens. Production was recorded by replicate every 28-d period and cumulatively. For the entire experiment, the inclusion of GLYC in the diet hindered feed conversion ratio per kilogram of eggs (2.071vs. 2.039; P < 0.05) but did not affect any of the other production or egg quality traits studied. The replacement of animal fat by lecithin (40:0, 20:20 and 0:40 g/kg) increased egg weight(60.1, 60.7 and 61.8 g, respectively; P < 0.001) and egg mass production (56.8, 57.5 and58.8 g/d, respectively; P < 0.01) and improved yolk color as measured by the DSM color fan (9.2, 9.2 and 9.5, respectively; P < 0.001) and feed conversion ratio per kilogram of eggs(2.072, 2.068 and 2.027, respectively; P < 0.05). Feed intake, egg production and body weight gain, however, were not affected. The inclusion of GLYC in the diet did not affect nutrient retention but lecithin inclusion improved TTAR of dry matter (P < 0.05), organic matter (P < 0.05), ether extract (P < 0.001) and gross energy (P < 0.001). In summary, the inclusion of 70 g glycerol/kg diet hindered feed conversion ratio per kilogram of eggs but did not affect any other production or digestibility trait. The replacement of animal fat by lecithin improved egg weight, egg yolk color and nutrient digestibility. Consequently, lecithin can be used as a lipid source in laying hen diets with beneficial effects on egg production. In the third study (chapter 4), the apparent metabolizable energy (AME) of traditional and re-esterified lipid sources and the effects of its inclusion in the diet on nutrient retention and broilers performance were studied in two experiments (Exp) from 7 to 21 d of age. In Exp 1 there was a control diet without any supplemental fat and three extra diets that included 25 g/kg of soy oil (SO), re-esterified monoacylglycerol (RMAG) or re-esterified triacylglycerol (RTAG) at the expense (wt:wt) of the control diet. The gross energy (GE, MJ/kg) of the oils was 39.66, 38.06 and 38.56, respectively. The AME of the lipid sources was determined by two methods: a) multiplying its GE by the digestibility of the ether extract (EE) of their respective diets and b) by difference between the AME of the control and the corresponding experimental diet. Nutrient retention was not affected by fat supplementation, except for EE that was higher for the oil supplemented diets than for the control diet (P < 0.001). The AME of the SO, RMAG and RTAG was 35.44, 33.89 and 34.05 MJ/kg when measured directly from digestibility data and 37.70, 35.68 and 35.83 MJ/kg when calculated by difference between the control and the oil containing diet. Fat supplementation improved feed to gain ratio (P ˂ 0.01) from 7 to 21 d of age, with effects being more pronounced for SO than for RMAG or RTAG. In Exp 2, the design was the same than in Exp 1 but the experimental diets included 50 g/kg of SO, acidulated soapstocks (ASO), lard, RMAG, RTAG or a 20:80 mixture of SO and RMAG (SO-RMAG). The AME of the supplemental fats was greater for the SO, SO-RMAG and lard than for the RMAG, with RTAG and ASO being intermediate (P < 0.01). Fat inclusion improved the retention of all nutrients. The AME content of the supplemental fats was higher when calculated by difference between the AME of the control and the fat containing diet than when measured directly from the GE and EE digestibility data and higher when included at 50 g/kg than when included at 25 g/kg. Supplemental fat improved ADG and F:G of the broilers, irrespective of the lipid source used (P ˂ 0.001). In conclusion, the re-esterified monoacylglycerol and triacylglycerol oils were well digested by broilers, with AME values within the range of those of traditional fat sources.