Gelatin isn’t just a ‘carrier’; it’s also good for dogs, especially ageing ones. For example, it inhibits inflammation and breakdown of the cartilage matrix.Collagen in the cartilage matrix and gelatin have a similar amino acid composition and there are indications that the amino acids in gelatin stimulate the synthesis of collagen cartilage.
This is one of the factors behind research that demonstrates the improvement in canine osteoarthritis due to gelatin supplementation. A trial of 15 dogs, fed gelatin in addition to their normal diet, found an improvement in activity(vitality), stiffness and lameness.
Plant-based jelly carriers don‘t currently provide the same benefits. Gelatin is also a human-grade ingredient that is generally regarded as safe (GRAS) for all species.
 P,Jacobs & Grim, H. & Geene, H. & Beynen, Anton & Vlerk, T..(2010). Oral Administration of Gelatin Hydrolysate Reduces Clinical Signs ofCanine Osteoarthritis in a Double-Blind, Placebo-Controlled Trial. AmericanJournal of Animal and Veterinary Sciences. 5. 10.3844/ajavsp.2010.102.106.