title: Phosphorus requirements for 60- to 100-kg pigs selected for high lean deposition under different thermal environments.
abstract: Two experiments were conducted to determine the requirement of available P (aP) of pigs selected for high lean deposition during summer (maximum and minimum temperatures of 29.8 ± 3.6 and 21.3 ± 1.1°C, respectively; Exp. 1) and winter (maximum and minimum temperatures of 24.7 ± 2.1 and 9.1 ± 1.6°C, respectively; Exp. 2). Pigs (66.5 ± 2.8 kg, Exp. 1; and 61.1 ± 0.6 kg, Exp. 2) were randomly allotted to 5 dietary treatments. Exp. 1 had 5 pens/treatment and Exp. 2 had 6 pens/treatment, and all pens had 2 pigs. Treatments were composed of a corn-soybean meal basal diet and 4 diets with additional dicalcium phosphate to obtain 5 aP concentrations (0.122, 0.187, 0.252, 0.317, and 0.382% in Exp. 1, and 0.135, 0.200, 0.265, 0.330, and 0.395% in Exp. 2). Pigs were allowed ad libitum access to their respective diets for 30 d. In Exp. 1, increasing aP improved ADFI and ADG (quadratic, P < 0.05), with maximum responses obtained at 0.226 and 0.256% of aP, respectively. Increasing aP improved (P < 0.05) G:F. A broken-line analysis indicated that G:F was maximized (P < 0.05) at 0.295% of aP or 9.04 g of aP/d. Increasing aP also increased (quadratic, P < 0.05) P and Ca (g/kg) in the metacarpals with maximum responses obtained at 0.314 and 0.272% of aP, respectively. The percentage of ash in the metacarpals continued to increase (linear, P < 0.05) with increasing aP. In Exp. 2, ADG and G:F improved (linear and quadratic, P < 0.05) as aP increased in the diet. A broken-line analysis indicated that G:F was maximized (P < 0.05) at 0.316% of aP or 10.58 g of aP per day. However, increasing aP had no effect on ADFI. Percentages of ash, P, and Ca in the metacarpals increased (linear, P < 0.05) with increasing aP. In conclusion, results of this experiment indicated that finishing pigs (60 to 100 kg) kept in a thermoneutral environment require 0.316% aP in the diet (10.58 g/d) to maximize G:F, but the requirement is only 0.295% aP (9.04 g/d) when pigs are under heat stress.
authors.affiliation: Universidade Federal de Viçosa, Viçosa, Minas Gerais, 36570, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Saraiva
authors.forename: J L
authors.initials: JL
authors.lastname: Donzele
authors.forename: R F M
authors.initials: RF
authors.lastname: Oliveira
authors.forename: M L T
authors.initials: ML
authors.lastname: Abreu
authors.forename: F C O
authors.initials: FC
authors.lastname: Silva
authors.forename: S E F
authors.initials: SE
authors.lastname: Guimarães
authors.forename: S W
authors.initials: SW
authors.lastname: Kim
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D018482:Muscle, Skeletal / Q000502:physiology*; D009751:Nutritional Requirements; D016226:Phosphorus, Dietary / Q000008:administration & dosage* / Q000378:metabolism; D012641:Selection, Genetic; D013552:Swine / Q000235:genetics* / Q000502:physiology*; D013696:Temperature
chemical_list: D016226:Phosphorus, Dietary