Original ResearchComparison of Nutrient Digestibility Between Adult and Aged Horses
Introduction
Although there has been considerable research conducted on the nutritional requirements of the healthy adult horse [1], [2], [3], there is little published work relating to the healthy aged horse. One of the few published studies reported that aged horses had a lower phosphorus absorption and lower fiber digestibility, as well as a trend for lower crude protein (CP) digestibility [4]. However, these findings were not supported in a later report by the same author who speculated that intestinal damage associated with parasite infestation may have contributed to the findings of the original study [5]. Although human studies have documented changing nutritional requirements for the aged, such as an increased requirement for vitamin D [6], selenium [7], and a decreased energy need [8], nutritional recommendations are often made on the basis of data collected in studies of aged humans with specific health problems, such as anorexia [6], [9].
The objective of this study was to compare macronutrient, calcium, and phosphorus digestibility between healthy adult and healthy aged horses fed three rations. Rations designed represent those commonly fed to horses including hay only, hay with a high-fat (oil) and low-cereal starch concentrate, and hay with a low-fat (oil) and high-cereal starch concentrate. Our hypothesis was that there would be no differences in digestibility of the different diets between healthy aged and healthy adult horses.
Section snippets
Animals
The study was originally designed with 18 mares; however, one animal was excluded because of unrelated health reasons. Thus, 17 stock-type mares completed the study, including nine healthy adult horses (5–12 years of age) and eight healthy aged horses (19–28 years of age). Twelve of the 17 mares (five adult and seven aged) originated from a single facility where they had been housed for several years and therefore were exposed to similar diet and management practices, including regular
Results
Aged horses weighed less (455 ± 12 kg) than adult horses (500 ± 13 kg; P = .02). There were, however, no differences in BCS between the two age groups (4.8 ± 0.2 for aged and 5.1 ± 0.2 for adult horses, respectively; P = .20). There were no interactions between BW or BCS and age, diet, or feeding period (Table 2).
Discussion
This study found no difference in the digestibilities of energy, NDF, CP, fat, calcium, or phosphorus between the two age groups. Diet differences were observed (diet differences are the subject of another manuscript in preparation), but as there were no interactions between age and diet, results were not included within this work. Data from this study support the hypothesis that older horses in good health and body condition do not automatically require changes to their core diet [16]. The
Conclusions
In comparison with previous work, this study evaluated a larger number of healthy horses, all of which had received regular anthelmintic treatment and had acceptable dentition. They were tested on three commonly fed formulated diets (high roughage, high oil and fiber, and high cereal) and underwent a relatively long diet adaptation period of 5 weeks. This study suggests that, under most practical feeding situations, differences in digestive capacity are unlikely to be present in healthy aged
Acknowledgments
The authors acknowledge Waltham Center for Pet Nutrition (Leics, UK) for funding this work.
References (34)
- et al.
Digestibility of a complete ration in horses fed once or three times a day and correlation with key blood parameters
Vet J
(2007) - et al.
Digestion in the aged horse
J Equine Vet Sci
(1989) Evidence-based equine nutrition
Vet Clin North Am Equine Pract
(2007)Nutrition and the aging male
Clin Geriatr Med
(2010)- et al.
Selenium status, fatty acids, vitamins A and E, and aging: the Nove study
Am J Clin Nutr
(1994) Vitamins in health and aging
Clin Geriatr Med
(2004)Nutrition of the aged horse
Vet Clin North Am Equine Pract
(2009)- et al.
Feeding and microbial disorders in horses: 2: Effect of three hay: grain ratios on digesta passage rate and digestibility in ponies
J Equine Vet Sci
(2001) - et al.
The digestibility and mineral availability of mature bermuda grass and alfalfa hay in mature horses
J Equine Vet Sci
(2000) Nutrition for aging cats and dogs and the importance of body condition
Vet Clin North Am Small Anim Pract
(2005)