## 4 Discussion
### Dry Matter Intake, In Vitro Degradability Parameters of Dry Matter and Neutral Detergent Fiber  
Differences observed between treatments in DMI could be attributed to the NDF contents of the experimental diets [34]. Our results do not agree with [PERSON] [39], who found higher values of DMI when supplementing diets based on corn silage with LLL. The highest values of aDM, bDM, DPDM EDDM, and KdDM recorded in T1 may suggest the availability of nutrients provided by carbohydrates and proteins from alfalfa hay [40]. Therefore, the higher values obtained for the aDM, bDM, and EDDM fractions will indicate a better nutrient availability for rumen microorganisms. Furthermore, the slower value of KdMS recorded in T2 indicates that the amount of energy that can be extracted from the diets during the time it remains in the rumen is low. Our results are in partial agreement with the DM degradability parameters reported by [PERSON] et al. [41], who investigated the effect of replacing alfalfa hay with L. leucocephala leaves in proportions of 25, 50, and 100%. EDDM values registered in T1 could be associated with the high contents of NDF and TC, which become severe limitations to improve the ruminal digestion of the nutrients contained in the treatments and negatively affect the dry matter degradability. MRRTDM's higher values and lower KpDM values observed in T2 and T4 can also be explained by the NDF contents. [PERSON] [42] has pointed out that when the content of the cell walls increases, the KpDM decreases and the MRRTDM increases proportionally, causing the cellulose and hemicellulose to ferment slowly, and this causes the physical filling of the rumen [43]. The highest kdNDF value was recorded in T1 and the lowest in T2 (\(p<0.05\)). This suggests that T2 was being broken down at a slower rate. In the present study, aNDF, bNDF, EDNDF, and kdNDF decreased when LLL replaced alfalfa hay by 20%. This may be due to the presence of anti-nutritional factors such as saponins and tannins in LLL [44]. KpNDF value was higher in the treatment with alfalfa hay as a forage source (T1) (\(p<0.05\)), while the other three were similar (\(p>0.05\)). The decrease in the in vitro degradability parameters of NDF observed in T2 (aNDF, bNDF, EDNDF, and kdNDF) does not agree with the results obtained by [PERSON] et al. [45], who found higher values, including LLL at 20% of the diet. These differences between both studies can be attributed to differences in the methods to determine degradability [46]. True Digestibility In Vitro of Dry Matter, Ruminal Fermentation Patterns, and Microbial Biomass Synthesis  
TDIVDM value in T1 could be attributed to a high synthesis of microbial biomass [47], while in T2, it could be explained by the lower contribution of ammonia and non-fibrous carbohydrates (NFC) for microbial growth [48]. The decrease in ammonia concentrations in T2 and T4 could be explained by the tannin content of the diets. There is general agreement that tannins decrease the degradation of proteins provided by the diets, mainly via the formation of tannin-protein complexes, which help to decrease the concentration of NH3-N [49]. Despite this trend, the NH3-N values observed in this study are within the optimal range to maximize microbial growth in the rumen, which is reported between 5 and 10 mg/dL [50]. Ruminal NH3-N concentrations are consistent with the results found by [PERSON] et al. [51] when evaluating LLL in ruminant diets. The decreased acetate in T2 and T4 and increases in propionate concentrations in both treatments can be attributed to the contents of structural carbohydrates (NDF) as well as non-fibrous carbohydrates (NFC) supplied by the experimental diets [52]. In fact, previous studies have consistently reported a decrease in the molar ratio of acetate and increases in the ratio of propionate under in vitro conditions using high-starch concentrates [53] and high-fiber forages [54].