An Assessment of the Effects of Guanidinoacetic Acid on the Performance and Immune Response of Laying Hens Fed Diets with Three Levels of Metabolizable Energy.

Different levels of metabolizable energy (ME) and the inclusion of guanidinoacetic acid (GAA) in the diet of 53-week-old Lohmann LSL-CLASSIC hens were used to evaluate its effect on reproductive parameters, egg quality, intestinal morphology, and the immune response. Six diets were used in a 3 × 2 factorial design, with three levels of ME (2850, 2800, and 2750 kcal/kg), and with (0.08%) or without the inclusion of GAA. The addition of GAA to diets with low levels of ME increased (p < 0.05) egg production and egg mass. Moreover, hens fed with 2800 kcal/g without GAA had the highest concentration (p < 0.05) of serum interleukin IL-2, while those fed diets with the same amount of ME but supplemented with 0.08% GAA had the lowest concentration. Finally, the inclusion of 0.08% GAA increased (p < 0.05) the concentration of vascular endothelial growth factor (VEGF), regardless of the ME level in the diet. This study highlights the potential role of GAA in decreasing the energy level of ME (50-100 kcal/g) in the feeding of hens and in the modulation of specific immune responses. Further research is recommended to fully understand the mechanisms of action of GAA on the mechanism target of rapamycin and its relationship with the immune response.

Effect of Dietary Guanidinoacetic Acid Levels on the Mitigation of Greenhouse Gas Production and the Rumen Fermentation Profile of Alfalfa-Based Diets.

The objective of this study was to evaluate the effect of different percentages of alfalfa (Medicago sativa L.) hay (AH) and doses of guanidinoacetic acid (GAA) in the diet on the mitigation of greenhouse gas production, the in vitro rumen fermentation profile and methane (CH4) conversion efficiency. AH percentages were defined for the diets of beef and dairy cattle, as well as under grazing conditions (10 (AH10), 25 (AH25) and 100% (AH100)), while the GAA doses were 0 (control), 0.0005, 0.0010, 0.0015, 0.0020, 0.0025 and 0.0030 g g-1 DM diet. With an increased dose of GAA, the total gas production (GP) and methane (CH4) increased (p = 0.0439) in the AH10 diet, while in AH25 diet, no effect was observed (p = 0.1311), and in AH100, GP and CH4 levels decreased (p = 0.0113). In addition, the increase in GAA decreased (p = 0.0042) the proportion of CH4 in the AH25 diet, with no influence (p = 0.1050) on CH4 in the AH10 and AH100 diet groups. Carbon monoxide production decreased (p = 0.0227) in the AH100 diet with most GAA doses, and the other diets did not show an effect (p = 0.0617) on carbon monoxide, while the production of hydrogen sulfide decreased (p = 0.0441) in the AH10 and AH100 diets with the addition of GAA, with no effect observed in association with the AH25 diet (p = 0.3162). The pH level increased (p < 0.0001) and dry matter degradation (DMD) decreased (p < 0.0001) when AH was increased from 10 to 25%, while 25 to 100% AH contents had the opposite effect. In addition, with an increased GAA dose, only the pH in the AH100 diet increased (p = 0.0142 and p = 0.0023) the DMD in the AH10 diet group. Similarly, GAA influenced (p = 0.0002) SCFA, ME and CH4 conversion efficiency but only in the AH10 diet group. In this diet group, it was observed that with an increased dose of GAA, SCFA and ME increased (p = 0.0002), while CH4 per unit of OM decreased (p = 0.0002) only with doses of 0.0010, 0.0015 and 0.0020 g, with no effect on CH4 per unit of SCFA and ME (p = 0.1790 and p = 0.1343). In conclusion, the positive effects of GAA depend on the percentage of AH, and diets with 25 and 100% AH showed very little improvement with the addition of GAA, while the diet with 10% AH presented the best results.

Effects of sodium butyrate and active Bacillus amyloliquefaciens supplemented to pasteurized waste milk on growth performance and health condition of Holstein dairy calves.

The objectives of the present study were to examine the impact of feeding both probiotics and sodium butyrate on calf performance and the economic implication of each treatment. A completely randomized design was used to investigate body weight (BW) gain, feed conversion efficiency and health conditions of Holstein dairy calves fed either pasteurized waste milk (PWM; n = 9) or a non-medicated milk replacer containing sodium butyrate and active probiotic Bacillus amyloliquefaciens (NMR; n = 9) from birth to 60 days of age. Numerically, calves fed PWM consumed more starter feed between days 16 and 45 than calves fed NMR but the difference became smaller by 60 days. Birth weights and colostrum IgG and serum total protein concentrations did not differ (p > 0.05) between the PWM and NMR calves. Calves receiving PWM had slightly greater BW at days 30 and 45, but were similar to that of calves receiving NMR at day 60. No differences were observed between PWM and NMR-calves for BW gains, flank height, hip width and health conditions (p < 0.05). Calves fed NMR had more watery feces but less frequent bouts of coughing than PWM-fed calves. Feed cost was higher (p < 0.001) for PWM-fed calves than NMR-fed calves during the experimental period. Dairy calves receiving NMR fortified with sodium butyrate and Bacillus probiotic could perform as similar as calves receiving PWM, and they had similar economic efficiency during the 60-d study period.