title: Association of SNP of neuropeptide Y, leptin, and IGF-1 genes with residual feed intake in confinement and under grazing condition in Angus cattle.
abstract: In this study we quantify and compare the phenotypic variation in residual feed intake (RFI) in 2 groups of Angus female calves: one carrying simultaneously putative favorable allelic variants (SNP) of neuropeptide Y, leptin, and IGF-1 genes (VAL group) and another devoid of such alleles (CON group). We performed 2 sequential trials: under confinement feeding a high-concentrate diet and under grazing condition. In confinement, 38 purebred Angus female calves [mean age and BW of 247 d (SD = 15) and 186 kg (SD = 33.2), respectively] were offered a total mixed ration diet (60:40 concentrate: alfalfa hay, as fed) ad libitum during 57 d. Dry matter intake was estimated from the difference between offered and refused feed; BW was recorded every 2 wk. Under grazing, 12 heifers from each group were ranked by BW and RFI and randomly assigned to 4 pasture paddocks. Heifers were continuously stocked at high-quality, high-herbage-mass mixed pasture. Herbage DMI was determined using the n-alkane technique. Different models were used to determine RFI: models that use phenotypic data [RFI as described by Koch et al. (1963; RFIK) and RFI as described by ME (RFIME)] and models that use standards feeding data [RFI estimated by Fan et al. (1995; RFIF) and RFI in which the expected DMI was derived from equations in Standing Committee on Agriculture (1990; RFISCA)]. Least squares mean values (SE) of DMI (kg/d), metabolizable energy intake (MEI; Mcal/d), ADG (kg), RFIK (kg DM/d), and feed conversion ratio (FCR; kg DMI/kg ADG) for VAL and CON genotype groups were 6.65 and 6.89 (0.49), 16.7 and 17.4 (1.44), 1.24 and 1.24 (0.03), -0.11 and 0.11 (0.09), and 5.8 and 5.8 (0.14), respectively, in the confinement trial. In the grazing trial least squares mean values (SE) of herbage DMI (kg/d), ADG (kg), MEI (Mcal/d), RFIK, and FCR of VAL and CON groups were 8.76 and 10.93 (0.71), 1.4 and 1.37 (0.05), 25.5 and 31.7 (2.09), -1.02 and 1.02 (0.42), and 6.41 and 6.96 (0.46), respectively. Genotyped groups tended to differ in DMI (P = 0.10), in MEI (P = 0.06), and in RFIK (P = 0.10), differed in RFIF (P = 0.010), and did not differ in ADG or FCR during confinement. During grazing, genotyped groups differed in DMI (P = 0.005), in MEI (P = 0.006), and in RFIK (P = 0.002) but did not differ in ADG and FCR. Our results demonstrate a strong association between these 3 SNP and RFI when animals were grazing on a high-quality, high-availability pasture, whereas a weak effect was observed under confinement.
authors.affiliation: Departamento de Producción Animal y Pasturas, Facultad de Agronomía, Universidad de la República, Avenida Garzón 780, 12900, Montevideo, Uruguay. anatruji@fagro.edu.uy
authors.forename: A I
authors.initials: AI
authors.lastname: Trujillo
authors.forename: A
authors.initials: A
authors.lastname: Casal
authors.forename: F
authors.initials: F
authors.lastname: Peñagaricano
authors.forename: M
authors.initials: M
authors.lastname: Carriquiry
authors.forename: P
authors.initials: P
authors.lastname: Chilibroste
mesh_terms: D000822:Animal Husbandry; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000235:genetics* / Q000378:metabolism; D004032:Diet / Q000662:veterinary; D002149:Energy Intake; D005247:Feeding Behavior; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism; D020738:Leptin / Q000235:genetics* / Q000378:metabolism; D009478:Neuropeptide Y / Q000235:genetics* / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D014583:Uruguay
chemical_list: D020738:Leptin; D009478:Neuropeptide Y; D007334:Insulin-Like Growth Factor I