A. C. Barroeta

Effects of dietary concentration and degree of polyunsaturation of dietary fat on endogenous synthesis and deposition of fatty acids in chickens

1. Two experiments were performed to assess the effect of different amounts of dietary polyunsaturated fatty acids (PUFA) on fatty acid composition of chickens. The contribution of de novo fatty acid synthesis to fatty acid profile was also estimated. 2. In trial 1, different fat sources were blended in different ratios allowing a gradient of dietary PUFA (from 15 to 61u2009g/kg), keeping added fat constant (9%). In trial 2, PUFA-rich oil was added at increasing inclusion rates (2, 4, 6 and 8%), achieving a dietary PUFA content ranging between 27 and 59u2009g/kg. 3. Increasing dietary PUFA inclusion resulted in an increase in PUFA deposition, with higher efficiency when dietary fat also provided saturated (SFA) and monounsaturated (MUFA) fatty acids (trial 1). 4. Increasing dietary PUFA in both trials resulted in a decrease in SFA and MUFA concentration in the whole body. 5. The estimated deposition of fatty acids from de novo synthesis was reduced when dietary fat content increased from 0 to 10%, varying between 35·34 and 17·66% for SFA and between 52·70 and 7·01% for MUFA in the whole body. The greater variation range for the MUFA supports the existence of a mechanism maintaining the SFA: (MUFAu2009+u2009PUFA) ratio within a specific range in biological membranes.

Utilization of different fats and oils by adult chickens as a source of energy, lipid and fatty acids

Abstract Sixty adult Warren roosters approximately 1 year old, randomized in individual cages, were fed a basal diet with or without 4% added fat. Nine fats and oils were evaluated: tallow (T1 and T2); tallow + soybean acid oil (50:50, TSAO); palm oil (PO); palm oil + soybean acid oil (50:50, PSAO); soybean acid oil (SAO); lard (L); soybean oil (SO); and linseed oil (LO). Soybean lecithin was included at 50 g kg −1 in T2. Experimental diets were evaluated for apparent fat availability (AFA), apparent availability of individual fatty acid (AAFA) and apparent metabolizable energy (AME). The AFA and AAFA values for added fats and oils were derived from those obtained for the basal diet and those obtained for the fat-supplemented diets, by difference, assuming the utilization of fat and fatty acid in the basal diet to be constant. The AME values of added fats and oils were calculated as the product of their AFA values and their gross energy values. In addition, the AME of added fats was calculated by substitution from the AME values of the basal diet and the fat-supplemented diets. The AFA and AME of added fats and oils ranged from 873 to 1013 g kg −1 and 33.5 to 40.2 MJ kg −1 , respectively. The addition of soybean lecithin to tallow did not affect the nutritive value of this animal fat. The nutritive value of added fats was more influenced by their free fatty acid content (FFA) and non-nutritive fraction than by their degree of saturation. SAO, with high free fatty acids and unsaponifiable contents, resulted in the lowest values for AME and AFA, but both measurements increased significantly when it was blended with T1 or PO. The AME values of experimental diets supplemented with different fats and oils were equivalent.

Effect of different levels of calcium and phosphorus and their interaction on the performance of young broilers

A study was conducted to evaluate the interaction among 3 levels of Ca and 4 levels of nonphytate phosphorus (NPP) on broiler performance, bone ash, and whole-body fractional retention of Ca and P. Ross male broiler-chicks (n=420) were sorted by BW at d 1 posthatch and assigned to 5 cages/diet with 7 birds/cage. Twelve diets were arranged in a 3×4 factorial of 3 levels Ca (at 0.5, 0.7, or 0.9%) and 4 levels NPP (at 0.25, 0.31, 0.38, or 0.45%) with a high dose of phytase (1,150 U/kg) in all diets. On d 14, chickens were euthanized and the right tibia was collected from 3 birds/replicate; the rest of the animals were used to measure whole-body Ca and P retention. An interaction was observed between the level of Ca and NPP on feed intake (FI), tibia weight, and bone-ash content (P<0.05). Increasing the level of NPP from 0.25 to 0.38% increased FI (P<0.05) on chickens fed the high-Ca diet (0.9%), but not with Ca at 0.5 or 0.7%. Broilers achieved their greatest weight gain (WG) and bone formation with 0.7% Ca and 0.38% NPP. Increasing the dietary Ca decreased its fractional retention from 74% with dietary Ca at 0.5 to 46% with Ca at 0.9%. The increase in the levels of dietary P steadily increased the fractional retention of Ca from 53 to 61%, and increased the whole-body Ca content (g/kg BW). It can be concluded that a dietary level of 0.38% NPP/kg in diets containing a high dose of phytase (1,150 U/kg) and 0.7% Ca are adequate to ensure broiler performance and bone ash of broilers from d 0 to d 14 posthatch.

Effects of extruded diet on the productive performance of weaning and post-weaned calves

Weaning and post-weaned calves were administered a fully-extruded (118°C, 20% humidity, 30 at.) diet, consisting of maize 25%, wheat 15%, soybean meal 21%, 79 TDN, and 17% CP. Compared with the same experimental diet in pellets (70°C, 8 at., control diet), fully-extruded feed resulted in statistically significant improvements in the productive performance of calves. Best results were obtained when administration of milk-replacer stopped. Thus, when calves were fed only the experimental diets, those on the fully-extruded diet showed a higher weight-gain (978 g/day vs. 838 g/day, P<0.01) and a lower feed conversion ratio (2.63 vs. 3.29, P<0.001) than control animals. These results suggest that the extrusion technology can be successfully applied to diets for post-weaned calves.