Effect of walking exercise and nutritional plan on goat performance

Abstract

This study evaluated the effects of walking exercise and nutritional plan on metabolic variables and the growth of stabled goats. Thirty-six goats [body weight (BW) = 21 ± 0.3 kg] were allocated in individual pens, and the treatments were randomly assigned to the animals in a 2 × 2 factorial design. The treatments consisted of walking exercise (7,5 km/day) or not and two nutritional plans [90 % (0.9M) or 170 % (1.7M) of the maintenance requirements] for 50 days (first period) . Further, all animals were fed a diet that met 170 % of their maintenance requirements and were not subjected to exercise for more 35 days (second period). There was no interaction effect between walking and nutritional plan for any of the studied variables. Walking exercise did not affect rib-eye area (REA; P = 0.13) or subcutaneous fat thickness (SFT; P = 0.11), but reduced body weight (BW) in the first (P = 0.03) and second (P = 0.03) periods. The animals in the 0.9M nutritional plan group exhibited lower REA and SFT values than those in the 1.7M group. This was accompanied by a decrease in plasma triiodothyronine concentration (T3; P = 0.03) in the animals that received the 0.9M plan in the first period. Exercise and nutritional plan, respectively, did not change (P ≥ 0.17) the plasma concentration of growth hormone (P = 0.31; P = 0.17), the gene expression of growth hormone receptors (GHR; P = 0.85; P = 0.79), insulin-like growth factor 1 (IGF-I; P = 0.87; P = 0.77), insulin-like growth factor 1 receptor (IGF1R; P = 0.55; P = 0.63) or peroxisome proliferator-activated receptors alpha (PPARα; P = 0.90; P = 0.92). In the second period, the BW and REA of the goats in the 0.9M group remained lower than those observed in the 1.7M group (23.33 vs. 30.37; P < 0.0001). Plasma T3 levels returned to values similar to those obtained with the 1.7M plan at the end of the second period (1.20 vs. 1.23; P = 0.03). Walking reduces the BW of goats without changing rib-eye area, subcutaneous fat deposition on the Longissimus muscle or gene expression. Nutritional restriction through a diet that meets 90 % of the maintenance requirements reduces weight gain but does not induce a full compensatory growth in goats.