Effects of Dietary Energy Levels on Growth Performance, Nutrient Digestibility, Rumen Barrier and Microflora in Sheep

Area of Science:

• Animal Science
• Nutritional Physiology
• Ruminant Metabolism

Background:

• Dietary energy is vital for ruminant growth and health.
• Understanding optimal energy levels is crucial for livestock production.
• Metabolic energy (ME) influences various physiological processes in sheep.

Purpose of the Study:

• To determine the optimal dietary metabolic energy (ME) levels for growing sheep.
• To evaluate the effects of varying ME diets on sheep growth, nutrient digestibility, rumen function, and gut barrier integrity.
• To analyze changes in rumen microbiota composition in response to dietary energy.

Main Methods:

• Forty-five growing Yunnan semi-fine wool sheep were fed diets with ME ranging from 8.0 to 10.4 MJ/kg.
• Evaluated growth performance, including average daily gain (ADG) and feed conversion ratio (FCR).
• Assessed nutrient digestibility, rumen fermentation parameters (VFA, pH, acetate-propionate ratio), rumen barrier function (protein and mRNA expression of tight junction proteins), and rumen bacterial diversity and composition.

Main Results:

• Increasing dietary ME linearly improved ADG, dry matter (DM), and organic matter (OM) digestibility, while decreasing FCR.
• Rumen total volatile fatty acids (VFA) and propionate concentrations increased linearly with ME, while pH and the acetate-propionate ratio decreased.
• Rumen barrier function markers (Claudin-4, Claudin-7, Occludin, ZO-1) and their mRNA expression increased with dietary energy, while bacterial diversity decreased.

Conclusions:

• Higher dietary energy levels positively impact sheep growth, nutrient utilization, rumen fermentation, and gut barrier function.
• Dietary energy significantly alters rumen bacterial community structure and diversity.
• The optimal dietary ME for growing Yunnan semi-fine wool sheep is estimated to be between 9.8 and 10.4 MJ/kg.