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The effect of very low food intake on digestive physiology and forage digestibility in horses


Clauss, Marcus; Schiele, K; Ortmann, S; Fritz, J; Codron, D; Hummel, J; Kienzle, E (2014). The effect of very low food intake on digestive physiology and forage digestibility in horses. Journal of Animal Physiology and Animal Nutrition, 98:107-118.

Abstract

Equid digestion is often conceptualized as a high throughput/low efficiency system, in particular compared to ruminants. It is commonly assumed that ruminants have an advantage when resources are limited; the effect of low food intake on digestive physiology of horses has, however, not been explored to our knowledge. We used four adult ponies (initial body mass [BM] 288 ± 65kg) in two subsequent trials with grass hay-only diets (in dry matter [DM]: hay1, mid-early cut, crude protein [CP] 10.5%, neutral detergent fibre [NDF] 67.6%; hay2, late cut, CP 5.8%, NDF 69.5%), each fed subsequently at four different dry matter intake (DMI) levels: ad libitum and at 75, 55 and 30 g kg-0.75 d-1. We particularly expected digesta mean retention times (MRT) to increase, and hence fibre digestibility to increase, with decreasing DMI. Ponies maintained BM on the first, but lost BM and body condition on DMI55 and DMI30. MRTs were negatively correlated to DMI and ranged (for particles < 2 mm) from 23/31 h (hay1/2) on the ad libitum to 38/48 h on DMI30. Digestibilities of DM, nutrients and fibre components decreased from DMI75 to DMI30; apparent digestibilities of organic matter and NDF (hay1/2) dropped from 47/43 % and 42/37 %, respectively, on the ad libitum DMI to 35/35 % and 30/28 % on DMI30. Additional differences evident between the two hays included a higher estimated ‘true’ protein digestibility for hay1, and finer faecal particles on hay2; there were no differences in faecal particle size between intake levels. The results suggest that below a certain food intake threshold, the major digestive constraint is not fermentation time but nutrient supply to gut bacteria. The threshold for such an effect probably varies between feeds, and might differ between ruminants and equids.

Abstract

Equid digestion is often conceptualized as a high throughput/low efficiency system, in particular compared to ruminants. It is commonly assumed that ruminants have an advantage when resources are limited; the effect of low food intake on digestive physiology of horses has, however, not been explored to our knowledge. We used four adult ponies (initial body mass [BM] 288 ± 65kg) in two subsequent trials with grass hay-only diets (in dry matter [DM]: hay1, mid-early cut, crude protein [CP] 10.5%, neutral detergent fibre [NDF] 67.6%; hay2, late cut, CP 5.8%, NDF 69.5%), each fed subsequently at four different dry matter intake (DMI) levels: ad libitum and at 75, 55 and 30 g kg-0.75 d-1. We particularly expected digesta mean retention times (MRT) to increase, and hence fibre digestibility to increase, with decreasing DMI. Ponies maintained BM on the first, but lost BM and body condition on DMI55 and DMI30. MRTs were negatively correlated to DMI and ranged (for particles < 2 mm) from 23/31 h (hay1/2) on the ad libitum to 38/48 h on DMI30. Digestibilities of DM, nutrients and fibre components decreased from DMI75 to DMI30; apparent digestibilities of organic matter and NDF (hay1/2) dropped from 47/43 % and 42/37 %, respectively, on the ad libitum DMI to 35/35 % and 30/28 % on DMI30. Additional differences evident between the two hays included a higher estimated ‘true’ protein digestibility for hay1, and finer faecal particles on hay2; there were no differences in faecal particle size between intake levels. The results suggest that below a certain food intake threshold, the major digestive constraint is not fermentation time but nutrient supply to gut bacteria. The threshold for such an effect probably varies between feeds, and might differ between ruminants and equids.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Veterinary Clinic > Department of Small Animals
Dewey Decimal Classification:570 Life sciences; biology
630 Agriculture
Language:English
Date:2014
Deposited On:23 Jan 2014 10:31
Last Modified:07 Dec 2017 08:23
Publisher:Wiley-Blackwell
ISSN:0931-2439
Publisher DOI:https://doi.org/10.1111/jpn.12053

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