The Establishment of Fibrolytic Bacteria in the Foal Gastrointestinal Tract Is Related to the Occurrence of Coprophagy by Foals.

The consumption of maternal feces (coprophagy) is commonly observed in healthy foals and is a proposed contributor to microbial colonization of the foal's gastrointestinal tract (GIT). This study investigated the role of coprophagy in the establishment of fibrolytic bacteria in the foal GIT. Nine thoroughbred mares were dosed with chromic oxide, an indigestible marker, as a method to detect the occurrence of coprophagy by their foals. Foal fecal samples were collected from 12 h to 21 d after birth to measure chromic oxide and neutral detergent fiber (NDF) and to enumerate cellulolytic bacteria using culture-based techniques. Milk yield was estimated at 7 and 14 d postpartum. Coprophagy was detected as early as 3 d after birth and detected in all foals by 7 d of age. There were strong relationships between coprophagy and cellulolytic bacteria and NDF in foal feces at 7 d of age (r = 0.9703 and r = 0.7878, respectively; p < 0.05). Fecal NDF and chromic oxide concentrations were negatively related to milk yield (r = -0.8144 and r = -0.6966, respectively; p < 0.05), suggesting milk availability affected the incidence of coprophagy. Based on the relationships identified, maternal feces are an important source of fiber and live microbes for the foal, contributing to the development of the microbial community.

Improved methods for mare milk analysis: Extraction and quantification of mare milk carbohydrates and assessment of FTIR-based macronutrient quantification.

Accurately determining the macronutrient profile of mare milk is a precursor to studying how milk composition affects foals' growth and development. This study optimized and validated an extraction and quantification method for mare milk oligosaccharides, which make up a portion of the carbohydrate fraction of mare milk. Mare milk was extracted with chloroform and methanol, and oligosaccharides were selectively isolated from the carbohydrate fraction using porous-graphitized carbon solid-phase-extraction (SPE). Good recovery rates for milk oligosaccharides (between 70 and 100%) were achieved with the optimized method. This study also compared the use of Fourier-Transform infrared (FTIR) spectroscopy versus wet chemistry quantification methods for protein, fat, and lactose. The FTIR method produced statistically equivalent protein contents to the wet chemistry method, along with substantial savings in both analyst time and consumable consumption. FTIR analysis slightly underestimated the fat content of mare milk relative to the official wet chemistry method, with the difference between the methods increasing at higher fat contents. FTIR also overestimated the lactose content of mare milk and appeared to generate "lactose" values that included the milk oligosaccharides and thus represented the total carbohydrate (lactose and milk oligosaccharides) content of mare milk.

Relationships Between Measurements of Body Fat in Thoroughbred Horses.

Equine obesity is increasing in prevalence, and weight loss diets are frequently recommended for these horses. However, there are also management situations in which horses are deemed to be too thin. To monitor the efficacy of weight change programs, estimates of body fat are often made. There are several systems available to estimate body fat, and there are benefits and challenges to using each method. The objective of this study was to compare four different methods of estimating body fat in Thoroughbred horses. In 14 mature Thoroughbred horses, relationships among body condition score (BCS), morphometric measurements, ultrasonic measures of subcutaneous fat depots, and estimation of total body fat (BFD) via measurement of total body water through deuterium oxide dilution were evaluated. Body condition scores ranged from 4.5 to 6.5 on a 9-point scale. Body condition score, heart girth-to-body weight ratio, and BFD were all positively correlated with each other (P < .05). Subcutaneous fat depth at the tailhead tended to be positively related to BFD when only horses with BCS ≥ 5 were included (P = .0680). These data suggest that BCS remains a simple means of monitoring adiposity in mature horses in moderate condition. Tailhead fat depots may become useful for monitoring changes in body fat in Thoroughbreds with a BCS above 5, although more work with animals of higher adiposity is required and at different times of year.

Phosphorus excretion by mares post-lactation.

Across the equine literature, estimates of true P digestibility range from -23% to 79%. This large range cannot be explained by differences in P intake or phytate-P intake alone. However, differences in endogenous P secretion into the GI tract may explain the variation. In horses, excess absorbed P is not excreted in the urine but is re-secreted into the GI tract, increasing faecal P and leading to estimates of low P digestibility. Thus, accurate estimates of P digestibility can only be obtained if absorbed P is retained in the horse. The objective of this study was to examine P digestibility in post-lactational mares and control mares that were fed similar amounts of P. It was hypothesized that post-lactational mares would have greater P retention and higher apparent P digestibility than control mares. Prior to the study, four lactating and four non-lactating mares were fed a diet that provided 100% of the control mares' P requirement, but only 55% of the lactating mares' P requirement. During the study, both groups were fed P at the rate recommended for non-lactating mares. Post-lactational mares did not retain more P than control mares but tended to excrete more P than control mares (p = .082), presumably due to differences in endogenous P secretion into the GI tract. Metabolic changes occurring during mammary gland involution may have contributed to the increase in P excretion. However, faecal P excretion exceeded P intake in both groups (p = .08) and both groups lost weight during the study. Tissue mobilization during weight loss may have influenced P secretion into the GI tract.

Effect of Starch Source in Pelleted Concentrates on Fecal Bacteria in Prepartum and Postpartum Mares.

Dietary starch source has been shown to affect fecal bacterial communities of horses fed minimally processed cereal grains. However, processing may increase foregut starch digestibility, reducing effects of starch source on fecal bacterial communities. This study aimed to determine the effect of starch source in pelleted concentrates on fecal Lactobacillus spp., amylolytic bacteria, and cellulolytic bacteria in broodmares mares, during the prepartum and postpartum period. Thoroughbred mares (n = 18) were paired by last breeding date then randomly assigned to either an oat-based or a corn and wheat middlings-based pelleted concentrate fed with forage. Mares were fed their assigned concentrates beginning on 310 days of gestation, and fecal samples were collected at 324 days of gestation, before parturition, 1 day, 14 days, and 28 days postpartum. Fecal samples were enumerated by serial dilution and inoculation into selective, enriched media for Lactobacillus spp., amylolytic bacteria, and cellulolytic bacteria. Data were log transformed then analyzed using a mixed model ANOVA with repeated measures (SAS 9.3) to test the main effects of treatment, time of sample, and treatment by time interaction. Starch source did not affect enumerated bacterial communities (P > .05); thus, pelleting concentrates may alter some of the effects of starch sources on the hindgut microbiota. Sample date did not affect amylolytic bacteria (P > .05); however, lactobacilli and cellulolytic bacteria decreased 1 day postpartum (P < .05). Although we did not observe an effect of starch source on fecal bacteria in mares, parturition did appear to alter the hindgut microbiota.

Effect of maternal diet on select fecal bacteria of foals.

Adult horses depend on the microbial community in the hindgut to digest fiber and produce short-chain fatty acids that are use for energy. Colonization of the foal gastrointestinal tract is essential to develop this symbiosis. However, factors affecting colonization are not well understood. The objectives of this study were to evaluate the age-related changes and effects of maternal diet on select fecal bacterial groups in foals from 1 to 28 d of age. Thoroughbred foals (n = 18) were from dams fed forage and one of two concentrates: an oat-based (OB) or corn and wheat middlings-based (CWB) pelleted concentrate. The mares had access to assigned concentrates, along with a mixed hay and cool-season grass pasture, 28 d before and 28 d after parturition. Fecal samples were collected from foals at 1 d (14 to 36 h), 4, 14, and 28 d after birth. Fecal samples were serially diluted with phosphate-buffered saline before inoculation of enriched, selective media to enumerate Lactobacillus spp., amylolytic bacteria, and cellulolytic bacteria. Enumeration data were log-transformed then analyzed with mixed model analysis of variance with repeated measures (SAS 9.3) to test the main effects of maternal diet (OB or CWB), time of sample, and interaction between maternal diet and time. Cellulolytic bacteria first appeared in foal feces between 4 and 14 d of age and increased with age (P < 0.05). Amylolytic bacteria and lactobacilli were abundant at 1 d and then increased with age (P < 0.05). There was an interaction between maternal diet and time for Lactobacillus spp. with OB foals having more lactobacilli than CWB foals at 1 and 4 d (P < 0.05); however, there were no differences observed at 14 d (P > 0.05). Maternal diet did not influence amylolytic or cellulolytic bacteria (P > 0.05). These results indicate that colonization of the hindgut is a sequential process beginning early in the foal's life and that maternal diet may influence some bacteria in the gastrointestinal tract of foals.