Influence of maternal or neonatal vitamin a administration on muscle and adipose tissue development in beef cattle

Abstract

This study aimed to evaluate the effects of Vitamin A (VA) injection on muscular and adipose tissue development, growth performance during cow-calf phase, and skeletal muscle transcriptomics in Angus × Nellore cattle. We hypothesized that VA injection in pregnant cows would be effective as VA injection in newborn calves to stimuli angiogenesis and adipogenesis. In this regard, 40 pregnant cows were utilized in two simultaneous trials in a randomized complete block design. Cows were weighed, blocked by parity and same-sire inseminated in two fixed-time artificial insemination (FTAI). After fetal sexing assessment, pregnant cows were sorted according to fetal sex and allotted in Trial 1 (cows pregnant with male, n = 20) or Trial 2 (cows pregnant with female, n = 20). Following, at 250d of gestation, cows from each trial were assigned into one of the three treatments: control with no VAinjection in cows or calves (CON: no vitamin A), single VAinjection in pregnant cows at 250d of gestation (VAcow; 2,000,000 IU of VA), two vitamin A injections in newborn calves (VAcalf: 200,000 IU of VA each dose), one at birth and one at 60d of age. Calves were weighed at 60d of age, and biopsied in the longissimus thoracis (LT) muscle at 60 d of age and at weaning to assess gene expression. From FTAI to weaning, cow-calf pairs were raised as a common herd under the same conditions. In Trial 1, calves from the VAcalf and VAcow groups exhibited higher weaning BW (P = 0.02) and average daily gain (ADG; P = 0.02) compared to the CON group. VA-treated (VAcalf + VAcow) calves also had greater rump depth (P = 0.03) and tended to have a lower muscularity index (P = 0.07) than CON calves. Transcriptomic analysis revealed 139 differentially expressed genes (DEGs; FDR < 0.10) when contrasting VAcalf + VAcow vs. CON. Comparing VAcalf vs. VAcow, 189 DEGs (FDR < 0.10) were identified. VAcow male calves displayed higher expression (P < 0.01) of RARA, PAX7 (P < 0.02), and tended to express more ZFP423 (P = 0.08). They also had greater expressions of MYF5, DLK1, CEBPA, and IGF1R (P < 0.05) compared to VAcalf and CON groups. In addition, in Trial 2, CON female calves tended to have higher weaning BW (P = 0.08) than VAcalf and VAcow female calves. The CON group also showed a greater longissimus muscle area (P = 0.05), while VA-treated female calves tended to have a lower longissimus muscle ratio (P = 0.07). VAcow female calves tended to express more MYH1 (P = 0.06) than CON. VA-treated groups exhibited higher expression of MYH1 (P = 0.03) and a trend for higher PPARD expression (P = 0.08) compared to CON female calves. Contrasting VAcalf vs VAcow, VAcow female calves expressed more RARB (P = 0.05) and tended to express more RARA and MTOR (P < 0.08). In summary, VA injection in pregnant cows or newborn calves enhance growth performance and modulate key developmental pathways especially in male calves.