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Impact of diet and arginine supplementation on pancreatic mass and digestive enzyme activity in non-pregnant ewes
Objectives were to determine the possible effects of feed intake and arginine infusion on pancreatic mass, and α-amylase and trypsin activities in ewes (2 to 4 yr of age; initial BW = 61.8±0.5 kg). Initially, 82 ewes were randomly allocated to one of three feeding groups; control (C; n = 24; 2.14 Mcal/kg), overfed (O; n = 27; 2xC), or underfed (U; n = 31; 0.6x C). Estrus was synchronized using a controlled internal drug release (CIDR) device for 14 days. At CIDR withdrawal, ewes from each dietary group were assigned to one of two treatments; Arg (L-Arg HCl, 155 µmol/kgBW) or saline (~10 mL). Treatments were administered 3 times daily for 21-26 days via jugular catheter beginning on day 0 of the first estrous cycle until the time of tissue collection. Ewes were euthanized during the early (d5) or mid (d10)-luteal phase of the second estrous cycle. Each pancreas was immediately removed, weighed, and stored at -80˚C until further analysis. Data were analyzed as a completely randomized design with a factorial arrangement of treatments (diet, arginine, and diet × arginine). Stage of estrus was initially included in the model but was removed as no differences (P > 0.10) were observed for any of the variables. During nutrition and Arg-treatment, C maintained BW and body condition score (BCS), O gained 4.1±1.3 kg, and U lost 15.5±0.6 kg; for O, BCS increased by 1.1±0.1 but for U decreased by 0.5±0.1. BW was greatest (P < 0.001) in O, less in C and least in U, and pancreas weights were greater (P = 0.02) in O than U. Concentration of α-Amylase activity (U/g and U/g protein) was greater (P ≤ 0.04) in O than U α-Amylase activity expressed as kU/pancreas was greater (P ≤ 0.002) in O than C or U. Trypsin activity (U/g, U/kg BW, and U/g protein) was greatest (P ≤ 0.05) in U. Arginine treatment did not influence pancreatic mass or α-amylase and trypsin activity. These data demonstrate that increasing feed intake increases α-amylase activity but decreasing feed intake increases trypsin activity in the pancreas. Thus, plane of nutrition but not arginine supplementation affects pancreatic mass and exocrine function in non-pregnant ewes which could affect digestive function and feed efficiency. Supported by USDA-AFRI grant 2011-67016-30174 to ATGB and DAR, Hatch Projects ND01748 to DAR and ND01712 to ATGB.
Keywords: sheep, arginine, pancreas