Abstract: Stock-type mares (498 ± 9 kg BW; 12 ± 7 yr) were used in a completely randomized design for 56 d to test the hypothesis that concentrate fortification improves apparent digestion and enhances lean mass over the topline. Horses were stratified by age, BW, and BCS and randomly assigned to either a custom pelleted concentrate (CON; = 13), or an iso-caloric, iso-nitrogenous pellet that included amino acid fortification, complexed trace minerals, and fermentation metabolites (FORT; = 10). Concentrate was offered at a total 0.75% BW/d (as-fed) twice daily, and diets were designed to meet or exceed maintenance requirements for mature horses. Horses had ad libitum access to Coastal bermudagrass hay (7.4% CP, 67% NDF, and 40% ADF). Every 14 d BW and BCS were recorded, and ultrasound images were captured every 28 d. area (LDA) and subcutaneous fat thickness (FT) were measured between the 12th and 13th ribs (12th/13th) and 17th and 18th ribs (17th/18th). Intramuscular fat at the 17th/18th ribs and rump fat-thickness were also obtained. Horses were dosed with 10 g/d of titanium dioxide (TiO) for 14 d to estimate forage dry matter intake (DMI). To account for diurnal variation, fecal samples were collected twice daily at 12-h intervals during the last 4 days, advancing by 3 h each day to represent a 24-h period. Fecal samples were composited by horse and analyzed for TiO to estimate fecal output and acid detergent insoluble ash was used to calculate forage DMI. To evaluate body composition, horses were infused with a 0.12 g/kg BW deuterium oxide (DO) on d 0 and 56. Body fat percentage (BF) was determined by quantifying DO in plasma samples collected at pre- and 4-h postinfusion via mass spectrometry. All data were analyzed using PROC MIXED (SAS v9.4). The model contained a fixed effect of diet; horse (diet) was a random effect. Horses receiving FORT gained 17th/18th FT ( < 0.01) and increased 17th/18th LDA from d 0 to 56 ( < 0.01) while 17th/18th FT and LDA were unchanged in CON. Regardless of diet, BF estimated by DO infusion increased in all horses from d 0 to 56 ( < 0.01). Average hay DMI was 2.1% BW, but did not differ between diets. In this study, concentrate fortification did not significantly ( 0.27) affect apparent digestion. In conclusion, concentrate fortification may promote greater muscle development along the posterior topline.
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This study investigated the impacts of diet fortification on body composition in mature horses and the apparent digestion when consuming low-quality forage. The findings suggested that while there was no significant impact on digestion, fortified diets may encourage muscle development along the horse’s back.
Study Design and Methodology
The researchers utilized stock-type mares of similar body weight (BW) and age. The horses were divided into two groups; one receiving a custom pelleted concentrate (CON), and the other receiving an iso-caloric, iso-nitrogenous pellet with added amino acids, complexed trace minerals, and fermentation metabolites (FORT).
Both groups consumed the concentrates twice daily as part of a diet designed to meet or exceed the maintenance requirements for mature horses. They were also given unlimited access to low-quality Coastal bermudagrass hay.
The team recorded the body weight and body condition score of the horses every 14 days and took ultrasound images every 28 days. They, in particular, took measurements of the longissimus dorsi area (LDA) and fat thickness (FT) in the mid and lower back of the horses. Additionally, they recorded measurements of intramuscular fat in the lower back and rump fat thickness.
To estimate hay intake, the horses were given a known quantity of titanium dioxide markers for two weeks. The researchers collected fecal samples to determine its excretion level, which was used to estimate hay intake.
The researchers also used a method called – deuterium oxide (DO) infusion – to evaluate changes in body composition over time. They infused a known quantity of DO in the horses and by quantifying it in blood samples, they could estimate the total body water and hence derive the body fat percentage.
Results and Interpretation
The results showed that horses receiving the FORT diet showed an increase in muscle mass and fat thickness along their posterior topline over the course of the study (from day 0 to 56). By contrast, horses on the CON diet did not exhibit any changes in these aspects.
All horses, irrespective of their diet, showed an increase in body fat estimated by DO infusion. However, the dietary treatment did not affect hay intake, suggesting that diet fortification did not significantly influence apparent digestion.
Despite the fact that diet fortification did not improve apparent digestion, the increase in muscle mass in horses on the FORT diet suggested that diet fortification may prove beneficial in promoting muscle development.
Conclusion
The study concluded that concentrate diet fortification might not impact digestion, but it could promote greater muscle development along the posterior topline in horses.
Cite This Article
APA
Much ML, Leatherwood JL, Zoller JL, Bradbery AN, Martinez RE, Keegan AD, Lamprecht ED, Wickersham TA.
(2019).
Influence of diet fortification on body composition and apparent digestion in mature horses consuming a low-quality forage.
Transl Anim Sci, 4(1), 1-9.
https://doi.org/10.1093/tas/txz137
Department of Animal Science, Texas A&M University, College Station, TX.
Leatherwood, Jessica L
Department of Animal Science, Texas A&M University, College Station, TX.
Zoller, Jennifer L
Department of Animal Science, Texas A&M University, College Station, TX.
Bradbery, Amanda N
Department of Animal Science, Texas A&M University, College Station, TX.
Martinez, Rafael E
Department of Animal Science, Texas A&M University, College Station, TX.
Keegan, Abby D
Cargill Incorporated, Elk River, MN.
Lamprecht, Emily D
Cargill Incorporated, Elk River, MN.
Wickersham, Tryon A
Department of Animal Science, Texas A&M University, College Station, TX.
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