Abstract
The hoof digital cushion is a complex structure composed of adipose tissue beneath the distal phalanx, i.e. axial, middle and abaxial fat pad. The major role of these fat depots is dampening compression of the corium underneath the cushion. The study aimed to determine expression of target genes and fatty acid profiles in the hoof of non-pregnant dry Holstein cows fed low (CON) or high-energy (OVE) diets. The middle fat pad of the hoof digital cushion was collected soon after slaughter. Despite the lack of effect on expression of the transcription regulators SREBF1 and PPARG, the expression of the lipogenic enzymes ACACA, FASN, SCD, and DGAT2 was upregulated with OVE. Along with the upregulation of G6PD and IDH1, important for NADPH synthesis during lipogenesis, and the basal glucose transporter SLC2A1, these data indicated a pro-lipogenic response in the digital cushion with OVE. The expression of the lipid droplet-associated protein PLIN2 was upregulated while expression of lipolytic enzymes (ATGL, ABDH5, and LIPE) only tended to be upregulated with OVE. Therefore, OVE induced lipogenesis, lipid droplet formation, and lipolysis, albeit to different extents. Although concentration of monounsaturated fatty acids (MUFA) did not differ, among the polyunsaturated fatty acids (PUFA), the concentration of 20:5n3 was lower with OVE. Among the saturated fatty acids, 20:0 concentration was greater with OVE. Although data indicated that the hoof digital cushion metabolic transcriptome is responsive to higher-energy diets, this did not translate into marked differences in the fatty acid composition. The decrease in concentration of PUFA, which could contribute to synthesis of inflammatory molecules, in OVE-fed cows indicated that feeding higher-energy diets might be detrimental for the mediation of inflammation in digital cushion. This effect could be further exacerbated by physiologic and endocrine changes during the peripartal period that favor inflammation.
Highlights
Lameness is one of the most important welfare issues of high-producing dairy cows in North America [1]
Dairy cows undergo several metabolic and physiologic adaptations in order to ensure a successful initiation of a new lactation cycle
The fat depots change from an adipogenic/lipogenic to a lipolytic state after parturition [11]. This effect is mainly attributed to a state of insulin resistance during the transition period [12]
Summary
Lameness is one of the most important welfare issues of high-producing dairy cows in North America [1]. The latter has been attributed to management and environmental factors [2] as well as physiologic adaptations such as postpartal negative energy balance, which can lead cows to excessive loss of body condition (BCS) [3]. Postpartal negative energy balance can be exacerbated by prepartal high-energy diets, where overconditioned cows entering a new lactation mobilize greater amounts of fatty acids (FA) from fat depots such as subcutaneous and mesenteric. A lower BCS at calving has been associated with reduced thickness of the digital cushion and, in turn, this condition can lead to development of hoof-related diseases such as sole ulcers and white line disease [3]
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