RESUMEN
Supplying trace minerals in more bioavailable forms such as amino acid complexes (AAC) could help ameliorate the incidence of hoof disorders in peripartal dairy cows. The aim of this study was to evaluate the effects of supplementing metal AAC during the peripartal period on expression of 28 genes in corium tissue related to claw composition, oxidative stress, inflammation, chemotaxis, and transcriptional regulation. Forty-four multiparous Holstein cows received a common diet from -30 to 30 d relative to parturition and were assigned to receive an oral bolus containing either inorganic trace minerals (INO) or AAC (i.e., organic) Zn, Mn, Cu, and Co to achieve supplemental levels of 75, 65, 11, and 1 ppm, respectively, in the total diet dry matter. Inorganic trace minerals were provided in sulfate form, and AAC were supplied via Availa Zn, Availa Mn, Availa Cu, and COPRO (Zinpro Corp., Eden Prairie, MN). Locomotion score was recorded before enrollment and weekly throughout the experiment. Incidence of hoof health problems at 30 d in milk was evaluated before a hoof biopsy in a subset of cows (INO=10; AAC=9). Locomotion score did not differ between treatments in the prepartum or postpartum period. The incidence of heel horn erosion was lower in AAC cows, but the incidence of sole ulcers did not differ. Downregulation of KRT5, CTH, CALML5, and CYBB, and upregulation of BTD in AAC cows indicated a decrease in the need for activation of cellular pathways to regenerate corium tissue and increase biotin availability in the sole claw. These molecular changes in the sole could have been triggered by the lower incidence of heel erosion in response to AAC. Among the genes associated with oxidative stress, the AAC cows had greater expression of NFE2L2, a transcription factor that regulates the antioxidant response, and the antioxidant enzyme SOD1. Among genes associated with inflammation, AAC cows had greater expression of TLR4, and lower expression of TLR2, IL1B, and TNF compared with INO cows. Supplementation with metal AAC during the peripartal period affected the expression of genes involved in composition, oxidative stress, and inflammation status in the corium. The hoof biopsy procedure used in the present study should be further perfected and implemented in future lameness research to expand our understanding of hoof biology in dairy cows.