Effects of Dietary Zinc Cysteamine Supplementation on Growth Performance, Physiological Responses, and Fecal Microbiota in Weaned Foals.

Overview

• This study investigated the effects of dietary zinc cysteamine (Zn-CS) supplementation on growth, health, and gut microbiota in weaned Ili foals.
• The researchers found that Zn-CS improved growth performance, nutrient digestibility, antioxidant capacity, hormone levels, and beneficial gut bacteria, identifying 6 mg/kg body weight per day as the optimal dose.

Introduction and Purpose of the Study

• Zinc cysteamine (Zn-CS) is a chelated form of zinc that has been found to improve gut health and growth in piglets.
• Its effects on weaned foals were not well understood prior to this study.
• The goal was to evaluate the impacts of Zn-CS supplementation on multiple parameters in weaned Ili foals, including:
• Growth performance
• Nutrient digestibility
• Physiological and biochemical status
• Fecal microbiota composition

Experimental Design

• Thirty-two 6-month-old Ili foals were randomly assigned to four groups.
• Groups received daily dietary Zn-CS supplementation at doses of 0 mg, 2 mg, 4 mg, or 6 mg per kg of body weight for 90 days.
• Measurements taken included:
• Growth metrics: final body weight, total weight gain, average daily gain, and body size indicators
• Nutrient digestibility: dry matter, digestible energy, metabolizable energy, acid detergent fiber
• Blood biochemical parameters: plasma albumin, total cholesterol, liver enzyme activities
• Serum hormones: growth hormone, insulin, triiodothyronine (T3), and somatostatin
• Antioxidant status: activities of superoxide dismutase, glutathione peroxidase, catalase and total antioxidant capacity, malondialdehyde content
• Fecal characteristics: pH, volatile fatty acid (VFA) concentrations, and microbiota composition

Key Findings: Growth and Nutrient Digestibility

• Zn-CS supplementation significantly improved growth outcomes:
• Higher final body weights
• Increased total weight gain
• Greater average daily gain
• Linear improvements in body size measures
• Digestibility of key nutrients improved markedly with Zn-CS:
• Improved dry matter digestibility
• Higher digestible and metabolizable energy utilization
• Better acid detergent fiber digestion

Physiological and Biochemical Effects

• Plasma biochemistry showed regulation via Zn-CS supplementation:
• Increased plasma albumin levels
• Reduced total cholesterol levels
• Normalized liver enzyme activities, indicating better liver function
• Antioxidant defense was strongly enhanced by Zn-CS:
• Elevated activities of superoxide dismutase, glutathione peroxidase, catalase
• Higher total antioxidant capacity
• Significant reduction in malondialdehyde, a marker of oxidative stress

Hormonal Changes

• Zn-CS upregulated growth-related hormones:
• Increased plasma growth hormone (GH)
• Increased insulin levels, supporting energy metabolism
• Higher triiodothyronine (T3), indicating enhanced metabolic activity
• Somatostatin, a hormone that inhibits GH, was decreased, facilitating growth promotion.

Fecal Characteristics and Microbiota

• Zn-CS supplementation reduced fecal pH, indicative of changes in gut fermentation.
• Volatile fatty acids (VFAs) in feces increased, reflecting enhanced microbial fermentation and nutrient utilization.
• Microbial community structure was reshaped by Zn-CS:
• Increase in beneficial bacterial populations
• Suppression of potential pathogenic bacteria

Conclusions and Implications

• Dietary Zn-CS at doses up to 6 mg/kg body weight per day promotes growth, physiological health, and gut microbiota balance in weaned Ili foals.
• The positive effects include improved nutrient digestion, enhanced antioxidant defenses, favorable hormonal changes, and increased beneficial gut bacteria.
• The study identifies 6 mg/kg BW/day as the optimal supplementation dose under experimental conditions for supporting foal development.
• These findings suggest Zn-CS as a promising dietary additive to improve growth performance and health in young horses post-weaning.