This study aimed to evaluate the effects of different proportions of alfalfa silage on the fermentation quality, in vitro digestibility, and aerobic stability of total mixed ration (TMR) silage. Three TMRs were prepared with different silage contents on a fresh matter basis: (1) 60% alfalfa silage (AS60), (2) 40% alfalfa silage (AS40), and (3) 20% alfalfa silage (AS20). The lactic acid in AS60 did not increase after 30 days of ensiling (p > 0.05). Butyric acid was detected in the AS20 group after 14 days of ensiling. The AS60 group showed significantly higher in vitro dry matter digestibility than the AS20 group (p < 0.05). The aerobic stability of TMR silage gradually increased with a decreasing percentage of alfalfa silage (p < 0.05). Unlike AS60, which directly gained an acidic environment from the alfalfa silage, AS40 developed a stable acidic environment during ensiling and further improved aerobic stability. However, when the percentage of alfalfa silage was reduced to 20%, a risk of clostridial spoilage occurred in the TMR silage. Therefore, the addition of 40% alfalfa silage to TMR is optimal and could achieve both good fermentation quality and considerable resistance to aerobic deterioration in TMR silage.

(Objectives) The objectives of this study were to evaluate the effect of half-replacement of the supplementary sulfate sources of Cu, Mn, and Zn with methionine-hydroxy-analog-chelated (MHAC) mineral or amino-acid-complexed (AAC) mineral forms in diets on the mineral status, blood immune biomarkers, and lameness of lactating cows. (Methods) Sixty multiparous Holstein cows (158 ± 26 days in milk; body weight: 665 ± 52 kg; milk yield: 32 ± 7 kg/day) were randomly assigned into one of three dietary treatments (n = 20 per group): (1) MHAC: 50% replacement of sulfate minerals with MHAC forms. (2) AAC: 50% replacement of sulfate minerals with AAC forms. (3) S: 100% sulfate minerals (control). Their Cu, Mn, and Zn concentrations, blood immune biomarkers, and lameness were measured monthly. Repeated-measure mixed models were used to evaluate the effects on trace mineral status over time. As the responses with the MHAC and AAC forms were similar, the treatments were also analyzed as organic trace minerals (OTMs, combining the MHAC and AAC groups, n = 40) versus inorganic trace minerals (ITMs, the S group, n = 20). (Results) Cows supplemented with OTMs had higher concentrations of Cu and Mn in their serum (p ≤ 0.05), a higher hoof hardness (p ≤ 0.05), and a lower incidence of lameness compared to those with ITMs on d 90. There were no statistical differences (p > 0.10) in the concentrations of IgA, IgG, or ceruloplasmin, but there were significant differences (p = 0.03) in the concentrations of IgM in the serum as fixed effects of the diet treatments during the whole trial. On d 30 and 90, the serum IgA concentrations of the cows supplemented with OTMs tended to be higher (0.05 < p ≤ 0.10) than those in the cows supplemented with ITMs. (Conclusions) The half-replacement strategy showed that the MHAC and AAC sources of Cu, Mn, and Zn additives had similar effects on the production performance, blood immune biomarkers, and lameness of the lactating cows. The long-term replacement strategy with OTMs led to the enhancement of the trace mineral concentrations in their body fluids, blood immune biomarkers, and hoof health.

Background: The rumen development of calves can result in long-term effects on growth, health, and milk yields in adult cattle. Dietary fiber supplement can stimulate rumen development in calves during pre-weaning period. Non-forage fiber can be used as starter fiber to reduce gastrointestinal fill and increase the content of rumen volatile fatty acid (VFA) because of higher biodegradable fiber. Numerous studies revealed that non-forage fiber has no negative effect on pre-weaning calves compared to forage fiber, but few evidences of rumen development were given. It is unclear whether different fiber sources impact the development of rumen in pre-weaning calves. Here, this study investigated the synergistic responses of rumen microbiota, metabolites and epithelium to different fiber source. Results: Thirty healthy Holstein calves with similar age (4.2 ± 2.3 days) and body weight (39.2 ± 3.6 kg) were allocated to two groups (15 cows per group), and were fed with one of the two diets with different fiber sources, short oat hay (SO), or short soybean hull (SS) for 8 weeks, respectively. At the end of the experiment, 6 calves of each group with similar body weight were selected to slaughter. Observations showed that SO-feeding calves has lengthened and widened rumen epithelial papillae. Metagenomic results revealed that different bacteria responded to different fiber source by different Carbohydrate-active enzymes (CAZymes) (P < 0.05). Metabolomics analysis indicated that “vitamin B6 metabolism” pathway was significantly enriched based on the 22 increased metabolites in the SO calves (P < 0.05, pathway impact > 0.05). The Pyridoxine, 4a-Carbinolamine tetrahydrobiopterin and Gentisic acid were enriched under SO feeding (P < 0.05, VIP > 1). Transcriptome analysis revealed that 129 differentially expressed genes (DEGs) were identified from comparison of the two groups. The DEGs related to transcription, translation and energy metabolism were upregulated (P < 0.05). Conclusions:The SO feeding (forage fiber) can lead to the enrichment of beneficial metabolites and metabolic pathways, promote the expression of genes related to energy metabolism, transcription and translation, and ultimately promote the development of rumen epithelium. Therefore, in pre-weaning calves production, attention should be paid to the impacts of forage fiber (short oat hay) introduction on rumen morphology and function.