In the current intensive production system, ruminants are often fed high-grain (HG) diets. However, this feeding pattern often causes rumen metabolic disorders and may further trigger laminitis, the exact mechanism is not clear. This study investigated the effect of HG diet feeding on fermentative and microbial changes in the rumen and on the expression of pro-inflammatory cytokines and matrix metalloproteinases (MMPs) in the lamellar tissue. In all, 12 male goats were fed a hay diet (0% grain; n=6) or an HG diet (56.5% grain; n=6). On day 50 of treatment, samples of blood, rumen content, and lamellar tissue of hooves of goats were collected. The data showed that compared with the hay group, HG-fed goats had lower (P<0.05) rumen pH but higher (P<0.05) total volatile fatty acids and lactate in the rumen and higher (P<0.05) lipopolysaccharide (LPS) levels in the rumen and blood. HG diet feeding altered the composition of rumen bacterial community, and correspondingly, the results suggested that their functions in the HG group were also altered. HG diet feeding increased (P<0.05) the expression of interleukin-1β, interleukin-6, tumour necrosis factor-α and MMP-2 mRNA in the lamellar tissues compared with the hay group. Correlation analysis indicated that the expression of pro-inflammatory cytokines were positively correlated with MMP-2 expression in lamellar tissues. Overall, these results revealed that HG feeding altered the patterns of rumen fermentation and the composition and functions of rumen bacterial community, and lead to higher levels of LPS in the peripheral blood, and further activated the inflammatory response in lamellar tissues, which may progress to the level of laminar damage.

The objective of this study was to identify possible risk factors for poor cow hind limb cleanliness in Danish loose-housed, lactating dairy cows. The study was conducted as a cross-sectional study of 1315 cows in 42 commercial Danish dairy herds with primarily Danish Holstein cows. The effect of four cow-level factors (parity, days in milk, daily lying time and lameness) and eight herd-level factors (herd size, milk production, milking system, floor type, access to pasture grazing, floor scraping frequency, hoof bathing frequency and hoof washing frequency) on the risk of having dirtier hind limbs were analysed using ordinal logistic regression fitting a proportional odds model. Cow hind limb cleanliness was scored using an ordinal score from 1 to 4: 1 being clean and 4 being covered in dirt. The odds ratios (ORs) estimated from the proportional odds model depict the effect of a risk factor on the odds of having a higher rather than a lower cleanliness score. First parity cows had an increased risk of being dirtier compared with third parity or older cows (OR = 1.70). Compared with late lactation, early and mid lactation were associated with an increased risk of being dirtier (OR = 2.07 and 1.33, respectively). Decreasing the daily time lying by 30 min was associated with an increased risk of being dirtier (OR = 1.05). Furthermore, an increased risk of being dirtier was found in herds with no pasture access (OR = 3.75).