Browsing by Author "Fernandes KA"

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    Comparison of gastrointestinal transit times in stabled Thoroughbred horses fed freshly cut pasture and three conserved forage-based diets
    (CSIRO Publishing, 2022-07) Fernandes KA; Rogers CW; Gee EK; Fitch G; Bolwell CF; Kittelmann S; Bermingham EN; Thomas DG
    Context: The type of forage offered to horses varies in physical form, moisture content and nutrient quality, and these variables could affect the intake, passage rate and digestibility of the forage consumed. Aims: To investigate the changes in passage rate of digesta through the gastrointestinal tract in horses fed four different forage-based diets (diet effect). Methods: Thoroughbred mares (n = 6) were stabled in loose boxes for 6 weeks. During Weeks 1, 3 and 5 (washout periods), all horses were fed freshly cut pasture, either in restricted quantities (Week 1) or ad libitum (Weeks 3 and 5). Using a 3 × 3 Latin square design during Weeks 2, 4 and 6, each pair of horses was abruptly transitioned to one of three conserved forage-based diets (chopped ensiled forage fed exclusively or with oats, or perennial ryegrass hay with oats) fed ad libitum. At the beginning of each week, indigestible polyethylene markers (n = 200) were administered to the horses via a nasogastric tube, followed immediately by transition to the new diet. Key results: There was a significant diet effect on the daily dry-matter intake of feed (P < 0.0001), percentage of time spent eating (P < 0.001), frequency of voiding faeces (P < 0.05) and quantity of faeces voided (P < 0.0001). There was a significant horse effect on the daily dry-matter intake of feed (P < 0.0001) and quantity of faeces voided (P < 0.0001), but no differences in the percentage of time spent eating or the frequency of voiding faeces. There were significant diet and horse effects on the time to recovery of the first marker in the faeces (P < 0.01 and P < 0.01 respectively) and the mean retention time of markers in the gastrointestinal tract (P < 0.05 and P < 0.001 respectively). Mean retention time was negatively correlated with feed intake and quantity of faeces voided (r2 =-0.51 and r2 =-0.64 respectively). Conclusions: Longer mean retention time was associated with a greater fibre content in the diet and a restricted feed supply, thus supporting the hypothesis that horses alter mean retention time on the basis of a nutrient absorption optimisation model. Implications: Feed composition, but also the quantities offered, may alter measurement of apparent feed digestibility in horses.
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    Resilience of Faecal Microbiota in Stabled Thoroughbred Horses Following Abrupt Dietary Transition between Freshly Cut Pasture and Three Forage-Based Diets
    (MDPI (Basel, Switzerland), 2021-09-06) Fernandes KA; Rogers CW; Gee EK; Kittelmann S; Bolwell CF; Bermingham EN; Biggs PJ; Thomas DG; Costa M
    The management of competition horses in New Zealand often involves rotations of short periods of stall confinement and concentrate feeding, with periods of time at pasture. Under these systems, horses may undergo abrupt dietary changes, with the incorporation of grains or concentrate feeds to the diet to meet performance needs, or sudden changes in the type of forage fed in response to a lack of fresh or conserved forage. Abrupt changes in dietary management are a risk factor for gastrointestinal (GI) disturbances, potentially due to the negative effects observed on the population of GI microbiota. In the present study, the faecal microbiota of horses was investigated to determine how quickly the bacterial communities; (1) responded to dietary change, and (2) stabilised following abrupt dietary transition. Six Thoroughbred mares were stabled for six weeks, consuming freshly cut pasture (weeks 1, 3 and 5), before being abruptly transitioned to conserved forage-based diets, both offered ad libitum. Intestinal markers were administered to measure digesta transit time immediately before each diet change. The conserved forage-based diets were fed according to a 3 × 3 Latin square design (weeks 2, 4 and 6), and comprised a chopped ensiled forage fed exclusively (Diet FE) or with whole oats (Diet FE + O), and perennial ryegrass hay fed with whole oats (Diet H + O). Faecal samples were collected at regular intervals from each horse following the diet changes. High throughput 16S rRNA gene sequencing was used to evaluate the faecal microbiota. There were significant differences in alpha diversity across diets (p < 0.001), and a significant effect of diet on the beta diversity (ANOSIM, p = 0.001), with clustering of samples observed by diet group. There were differences in the bacterial phyla across diets (p < 0.003), with the highest relative abundances observed for Firmicutes (62 - 64%) in the two diets containing chopped ensiled forage, Bacteroidetes (32-38%) in the pasture diets, and Spirochaetes (17%) in the diet containing hay. Major changes in relative abundances of faecal bacteria appeared to correspond with the cumulative percentage of intestinal markers retrieved in the faeces as the increasing amounts of digesta from each new diet transited the animals. A stable faecal microbiota profile was observed in the samples from 96 h after abrupt transition to the treatment diets containing ensiled chopped forage. The present study confirmed that the diversity and community structure of the faecal bacteria in horses is diet-specific and resilient following dietary transition and emphasised the need to have modern horse feeding management that reflects the ecological niche, particularly by incorporating large proportions of forage into equine diets.
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    Seasonal Variation in the Faecal Microbiota of Mature Adult Horses Maintained on Pasture in New Zealand
    (MDPI (Basel, Switzerland), 2021-08-04) Fernandes KA; Gee EK; Rogers CW; Kittelmann S; Biggs PJ; Bermingham EN; Bolwell CF; Thomas DG; Costa M
    Seasonal variation in the faecal microbiota of forage-fed horses was investigated over a 12-month period to determine whether the bacterial diversity fluctuated over time. Horses (n = 10) were maintained on pasture for one year, with hay supplemented from June to October. At monthly intervals, data were recorded on pasture availability and climate (collected continuously and averaged on monthly basis), pasture and hay samples were collected for nutrient analysis, and faecal samples were collected from all horses to investigate the diversity of faecal microbiota using next-generation sequencing on the Illumina MiSeq platform. The alpha diversity of bacterial genera was high in all samples (n = 118), with significantly higher Simpson's (p < 0.001) and Shannon-Wiener (p < 0.001) diversity indices observed during the months when horses were kept exclusively on pasture compared to the months when pasture was supplemented with hay. There were significant effects of diet, season, and month (ANOSIM, p < 0.01 for each comparison) on the beta diversity of bacterial genera identified in the faeces. While there was some inter-horse variation, hierarchical clustering of beta diversity indices showed separate clades originating for samples obtained during May, June, and July (late-autumn to winter period), and January, February, and March (a period of drought), with a strong association between bacterial taxa and specific nutrients (dry matter, protein, and structural carbohydrates) and climate variables (rainfall and temperature). Our study supports the hypothesis that the diversity and community structure of the faecal microbiota of horses kept on pasture varied over a 12-month period, and this variation reflects changes in the nutrient composition of the pasture, which in turn is influenced by climatic conditions. The findings of this study may have implications for grazing management and the preparation of conserved forages for those horses susceptible to perturbations of the hindgut microbiota.