Nutrient utilization by limit- and ad libitum-fed growing horses.
Eighteen Quarter Horse and Paint weanling colts were assigned to two treatments, either limit or ad libitum feeding. Nutrient digestibilities of diets were evaluated between 6 and 12 mo, 12 and 18 mo and 18 and 24 mo of age. From 6 to 12 mo, energy digestibility (64 to 68%) was unaffected by feed intake level. Ad libitum-fed horses had energy digestibilities 9 to 10% greater (P less than .05) than limit-fed horses between 12 and 24 mo of age, but adjustment for DM intake removed these differences. Limit-fed, mature ponies used dietary energy similarly to growing horses from 6 to 18 mo of age, but they used digested dietary energy more efficiently (P less than .05) than young horses at 24 mo of age. Ad libitum-fed horses digested more (P less than .05) dietary protein than limit-fed horses between 12 and 24 mo of age, but adjustment for DM intake removed these differences. True digestibilities of dietary Ca were estimated at 71 to 42% among periods, whereas true digestibilities of dietary P ranged from 52 to 6%. Sufficient P was absorbed by all horses between 6 and 18 of age, but by 24 mo of age horses were in negative P balance despite an apparently adequate P intake. Using regression analyses, daily endogenous fecal Ca and P were predicted to be 36 and 18 mg/kg body weight, respectively.
Cymbaluk
N F
NF
Dept. of Herd Med. and Theriogenol, University of Saskatchewan, Saskatoon, Canada.
Christison
G I
GI
Leach
D H
DH
D000818:Animals; D002136:Calcium, Dietary / Q000378:metabolism*; D004044:Dietary Proteins / Q000378:metabolism*; D004063:Digestion; D004734:Energy Metabolism; D005247:Feeding Behavior / Q000502:physiology*; D006736:Horses / Q000254:growth & development*; D008297:Male; D010758:Phosphorus / Q000378:metabolism*
D002136:Calcium, Dietary; D004044:Dietary Proteins; D010758:Phosphorus