Effects of long-term restricted feeding on digestion and energy utilization in Balady vs. Shami goats

•Effect of intake level, control (CON) or restricted (RES), was studied in goats.•Similar digestibility was reported for Shami and Balady goats with RES or CON level.•Only Balady goats can reduce their energy expenditure (EE) with RES intake.•Reduction in EE is a mechanism of adaptation for survival under RES intake level.•Energy balance is better in Balady than Shami goats when fed RES intake level.

Twenty four non-lactating goats (Age=3.5±0.08 years; Balady goats, n=12 and Shami goats, n=12) were used to evaluate the effects of long-term nutrient restriction on digestion and energy utilization. Six animals of each goat breed were fed a concentrated mixture and alfalfa hay diet (50:50 as DM basis) to meet metabolizable energy (ME) of maintenance (MEm, CON). The other six animals were fed 50% of this amount relative to actual BW (RES). Animals were individually housed for a 90-day period and then moved to metabolic cages in two sets of 12 animals each, three per treatment and breed for each set. Total Energy expenditure (EE) was estimated by a heart rate (HR) monitor for 48 h after its individual calibration by oxygen consumption with a face mask open-circuit respiratory system. Body weight and digestibility were negatively affected by long-term restricted feeding, without differences in digestibility between goat breeds. Energy expenditure was greater for CON vs. RES (417 vs. 355 kJ/kg BW0.75/day respectively, P<0.001) and lower for Balady goats compared to Shami goats, particularly in terms of RES intake treatment (312 vs. 399 kJ/kg BW0.75/day respectively, P<0.01). As a result, the energy balance (EB) was similar for both goat breeds on treatment CON, while it was greater (P<0.05) for Balady goats than Shami goats when they received RES treatment (−133 vs. −208 kJ/kg BW0.75/day respectively, P<0.01). In conclusion, Balady goats, but not Shami goats, have the ability to reduce their EE in order to improve their EB as a mechanism of adaptation when their ME intake is restricted below MEm requirements.