ABSTRACT
Methane produced by cattle is one of the contributors of anthropogenic greenhouse gas. Methods to lessen methane emissions from cattle have been met with varying success; thus establishing consistent methods for decreasing methane production are imperative. Ferric iron may possibly act to decrease methane by acting as an alternative electron acceptor. The objective of this study was to assess the effect of ferric citrate on the rumen bacterial and archaeal communities and its impact on methane production. In this study, eight steers were used in a repeated Latin square design with 0, 250, 500 or 750 mg Fe/kg DM of ferric iron (as ferric citrate) in four different periods. Each period consisted of a 16 day adaptation period and 5 day sampling period. During each sampling period, methane production was measured, and rumen content was collected for bacterial and archaeal community analyses. Normally distributed data were analysed using a mixed model ANOVA using the GLIMMIX procedure of SAS, and non-normally distributed data were analysed in the same manner following ranking. Ferric citrate did not have any effect on bacterial community composition, methanogenic archaea nor methane production (P>0.05). Ferric citrate may not be a viable option to observe a ruminal response for decreases in enteric methane production.
ABSTRACT
Lolium arundinaceum [(Darbyshire) tall fescue] toxicosis is responsible for substantial beef production losses in the United States, due to its negative effects on reproduction, growth, and feed efficiency. These effects are consequences of toxic alkaloids within tall fescue. Interseeding legumes, such as Trifolium pratense (red clover), into pastures has been shown to mitigate a portion of these effects. Clovers contain isoflavones, which may play a role in tall fescue toxicosis mitigation. The present study utilized 36 Angus steers to determine the effects of daily supplementation with a red clover-isolated isoflavone feed additive on physiological symptoms of tall fescue toxicosis and the rumen microbial environment over a 21-d period. Angus steers were initially stratified based upon their single nucleotide polymorphism genotype at the DRD2 receptor. Treatments were then randomly assigned in a 2 × 2 factorial arrangement within a completely randomized design, where treatment factors consisted of tall fescue seed type (endophyte-infected tall fescue seed vs. endophyte-free tall fescue seed) supplemented with and without the isoflavone additive. Steers that consumed endophyte-infected tall fescue seed had lower serum prolactin concentrations (P = 0.0007), average daily gain (ADG; P = 0.003), final body weight (BW; P = 0.004), and feed efficiency (P = 0.018) when compared with steers that consumed endophyte-free tall fescue seed. Serum insulin-like growth factor-1 (IGF-1) tended to be reduced with supplementation of isoflavones (P = 0.06) but was unaffected by seed type (P ≥ 0.10) and seed by treatment interaction (P ≥ 0.10). Isoflavones reduced serum glucose levels (P = 0.023), but neither seed type, isoflavones, or their interaction affected serum urea nitrogen (SUN), nonesterified fatty acids (NEFA), or insulin (P ≥ 0.10). Volatile fatty acid concentrations, dry matter intake (DMI), ruminal pH, and overall feeding behaviors were also unaffected by seed type or isoflavone treatments (P ≥ 0.10). Twenty-eight ruminal bacteria taxa shifted as a result of seed type or isoflavone treatment (P < 0.05). In this experiment, feeding isoflavones to Angus cattle did not completely mitigate all symptoms of fescue toxicosis. However, dose-response trials may aid future research to determine if dietary supplementation with isoflavones alleviates fescue toxicosis symptoms and promotes livestock growth and performance.
ABSTRACT
Negative impacts of endophyte-infected Lolium arundinaceum (Darbyshire) (tall fescue) are responsible for over $2 billion in losses to livestock producers annually. While the influence of endophyte-infected tall fescue has been studied for decades, mitigation methods have not been clearly elucidated. Isoflavones found in Trifolium pratense (red clover) have been the subject of recent research regarding tall fescue toxicosis mitigation. Therefore, the aim of this study was to determine the effect of ergovaline and red clover isoflavones on rumen microbial populations, fiber degradation, and volatile fatty acids (VFA) in an in vitro system. Using a dose of 1.10 mg × L-1, endophyte-infected or endophyte-free tall fescue seed was added to ANKOM fiber bags with or without 2.19 mg of isoflavones in the form of a control, powder, or pulverized tablet, resulting in a 2 × 3 factorial arrangements of treatments. Measurements of pH, VFA, bacterial taxa, as well as the disappearance of neutral detergent fiber (aNDF), acid detergent fiber (ADF), and crude protein (CP) were taken after 48 h of incubation. aNDF disappearance values were significantly altered by seed type (P = 0.003) and isoflavone treatment (P = 0.005), and ADF disappearance values were significantly different in a seed × isoflavone treatment interaction (P ≤ 0.05). A seed × isoflavone treatment interaction was also observed with respect to CP disappearance (P ≤ 0.05). Eighteen bacterial taxa were significantly altered by seed × isoflavone treatment interaction groups (P ≤ 0.05), eight bacterial taxa were increased by isoflavones (P ≤ 0.05), and ten bacterial taxa were altered by seed type (P ≤ 0.05). Due to the beneficial effect of isoflavones on tall fescue seed fiber degradation, these compounds may be viable options for mitigating fescue toxicosis. Further research should be conducted to determine physiological implications as well as microbiological changes in vivo.
