Weight loss resistance: a further consideration for the nutritional management of obese Equidae.

The study explores varying levels of weight loss resistance in overweight horses and ponies, seeking to better understand dietary adjustments that can holistically combat equine obesity. The researchers monitored changes in body mass, condition, and other physical and metabolic indicators as the animals underwent a limited forage-based diet.

Methodology

• The researchers focused on 12 overweight horses and ponies (body condition score, BCS, 7/9 or above). These animals were of varied breed and gender, and were monitored over a period of 16 weeks.
• The subjects were randomly divided into two groups, each receiving variations of a restricted, forage-based diet. The Group 1 diet focused on chaff-based feed and hay, while the Group 2 diet leaned more on hay and a nutrient-balancer. The amount of food intake was capped at 1.25% of body mass.
• Various physical and metabolic measures were observed, including body mass, body condition score, heart and belly circumference, and direct (ultrasound) and indirect (D(2)O dilution, bioelectrical impedance analysis) measures of body fat. Additionally, indices of insulin resistance were tracked.

Findings

• There was notable individual variability among the animals in terms of proportional weight loss, ranging from 0.16% to 0.55% of initial body mass each week. This shows that some equine subjects had a higher resistance to weight loss than others.
• The degree of weight loss resistance was not tied to any specific outset variable or the diet given. Instead, it was primarily determined by the animal’s identity and individual characteristics, with animal identity accounting for 65% of the observed variation.
• Predicted rates of weight loss lessened over time. Furthermore, body condition score and bioelectrical impedance analysis measures were found imprecise when estimating D(2)O-derived body fat percentage.
• Changes in the fat depth within the retroperitoneal area (located behind the abdomen’s peritoneum) and just below the skin were noted. In general, belly circumference changes correlated with ln loss of retroperitoneal fat and body mass.
• By the end of the study, 9 out of the 12 animals showed improved insulin resistance, thus indicating a positive shift in metabolic health.

Implications

• The study emphasizes the need for specific dietary restrictions in addressing equine obesity. A starting point could be limiting forage dry matter intake to 1.25% of body mass.
• However, adjusting the restriction to 1% may be necessary for animals showing high weight loss resistance.