Content area
Abstract
Introduction. Differences in dietary maintenance requirements for old horses compared to adult horses is unknown (NRC, 2007). The objective of this study was: to investigate the dietary intake in a group of old mares while testing the effects of a fatty acid supplement containing α-linolenic acid and chromium yeast on insulin sensitivity and inflammatory markers.
Materials and methods. Dietary intake for thirty-two old (mean ± SE, 21.9 ± 0.65; 16–26 yr), nonpregnant, idle mares was tracked between February to July of 2010 and was compared to the 2007 National Research Council predicted values for idle maintenance horses. Fourteen of the 32 mares were supplemented between July 2009 and July 2010 with 190 g/d of Equine Platinum Plus Metabolic Support (EPPMS): a fatty acid formula from Platinum Performance™ containing ALA with an addition of Chromium Yeast and other minerals and vitamins. Baseline blood samples were taken on those 14 mares, weight was taken using a calibrated electronic livestock scale (Cardinal Scale Manufacturing Company; Webb City, MO). Mares were classified into non-metabolic or insulin resistant using basal proxies (Treiber et al., 2005). Monthly assessment of dietary intake, BW, BCS and neck condition score (NCS) began in February. Twenty-two mares participated on an exercise schedule 3 to 5 d/wk. Dietary intake predicted requirements were adjusted for those walked versus idle, voluntary activity by other mares. The six months of predicted vs. actual nutrient intake values were analyzed by ANOVA and significant differences were compared by the least square means analysis.
Results & discussion. Overall, actual caloric intake was 13.8% higher than predicted caloric intake (P < 0.001); more specifically, in the month of June, actual was higher than predicted by 21.6%. In addition, actual intake of CP, calcium (Ca), phosphorus (P), magnesium (Mg), zinc (Zn), and copper was higher in June than predicted intake of those same nutrients (P < 0.001) in all other months. An increase in WSC (P < 0.028) occurred with the increase in DMI from May (8.4%) to June (9.5%). Dietary caloric intake increased by an average of 20% from May to July and BCS increased (P < 0.05) from 5.8 to 6.4 (out of a 1–9 possible range); yet NCS ( P = 0.71) and weight (P = 0.99) did not vary even though most of the time the mares were fed on average, 13.8% above DE requirements. An increase in BCS by 0.6 may be due to the even greater increase (21.6%) in calories during the month of June. Additionally, those supplemented with EPPMS increased in insulin sensitivity and pancreatic-beta cell function from July 2009 to May 2010 (P < 0.001); yet weight trended to increase (P = 0.07). Caloric intake increased between sampling from 1.35% BW to 1.47% BW. Inflammatory cytokines COX-2 ( P < 0.05) and IL-1 (P < 0.05) increased. TNF-alpha trended higher (P = 0.07) after supplementation and IL-10 was lower for those walked (P < 0.05). No effect was seen for cortisol or exercise compared with any other parameters. Vitamins, minerals, and amino acids were present in the supplement, but not measured and results are inconclusive for insulin sensitivity. In comparison with the short-run study of those supplemented versus non-supplemented, no change in insulin sensitivity was found for those supplemented. Dietary intake increased from May to July by 6 kcal/kg of BW. Weight increased (P < 0.05) amongst both groups of walked or idle and weight trended to increase (P < 0.06) between supplemented versus non-supplemented. An increase in BCS (P < 0.003) was found between May (5.6 ± 0.22) to July (6.25 ± 0.22).
Conclusion. Although previous research has indicated that nutrient intake is similar between old and young horses, in the current study mares did not increase in body weight or condition when fed 10% above energy requirements. A long-term controlled study measuring dietary nutrient inputs and outputs as well as left-over feed coupled with more frequent body weighing for tracking body weight fluctuations is needed to confirm current results. Additionally, those fed EPPMS from July 2009 to May 2010 increased in insulin sensitivity and pancreatic-beta cell function; however, when BCS and weight increased due to dietary calorie increase occurred in the short-run study compared to those non-supplemented, no effect was found on insulin sensitivity. In terms of improvement, a more controlled study including IR old horses with simiar BCS given a consistent diet would be needed to evaluate the effects of a fatty acid supplement. (Abstract shortened by UMI.)
