Nutrition and the skeletal health of dogs and cats

Abstract

In this thesis, the influence of nutrition on skeletal health was studied. Obesity is a common disease in companion animal practice. In dogs and cats obesity often exacerbates osteoarthritis (OA). Although in humans we consider obesity as a serious health issue, in companion animals we proved that obesity or overweight is considered as normal, beautiful, or ideal. Dietary long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been proved to be effective in dogs suffering from OA by mediating the inflammatory response. We demonstrated that treatment of cats suffering from OA with dietary supplementation with EPA and DHA also resulted in improvement of locomotion. Vitamin D is important for skeletal health as it plays a central role in calcium metabolism. Sunlight has long been recognized as a major provider of vitamin D for humans. We demonstrated that the “sunshine vitamin” is synthesized in sufficient amount in the investigated carnivorous species, thus they are largely dependent on dietary intake of vitamin D. High calcium and/or vitamin D intake in puppies has proven to influence skeletal development at older age. Since quite some puppies start to be raised on PMRs, the calcium and vitamin D content of the PMRs were investigated and proved to be higher compared to the declaration on the package. Furthermore, most breeders overfeed their puppies with PMR, which resulted in calcium and vitamin D intakes exceeding the safe upper limit. Another common developmental orthopedic diseases in young dogs is medial coronoid disease (MCD). Delayed endochondral ossification plays a crucial role in MCD development. This delayed endochondral ossification might be due to a (relative) vitamin D deficiency. We demonstrated that supplementing the daily ration of young growing dogs susceptible to develop MCD with vitamin D did not result in a decreased prevalence of MCD. These findings are suggesting that other factors play a role in delayed endochondral ossification preceding MCD development. The conversion of vitamin D is stimulated by growth hormone (GH), which is mainly produced by the pituitary gland, In adult dogs with Cushings disease an important source of GH is suppressed. The removal of the pituitary gland as treatment results in the removal of an important source of GH, and in humans this results in osteoporosis. However, in adult dogs, 1,25DHCC and PTH plasma levels were not different before and after hypophysectomy compared to healthy control dogs. In conclusion, neither in dogs with Cushings disease nor after hypophysectomy, there is a need for vitamin D supplementation. Vitamin A is the other vitamin which plays a role in maintaining skeletal health. Vitamin A excess in cats has been studied in the 1960s and 1970s and demonstrated skeletal hyperostosis, mostly in the cervical spine. It is remarkable that moderate increased vitamin D supplementation (as present in natural feeding stuffs like raw liver) decreases the detrimental influence of excess vitamin A on liver fibrosis, but not on the skeleton, possibly due to the anti-fibrotic effect of moderate vitamin D.