PSVII-2 Effect of vitamin A administration in pregnant cows or newborn calves on beef quality and skeletal muscle gene expression.

Abstract

The study aimed to evaluate the effects of Vitamin A (VA) injection on beef quality and skeletal muscle gene expression related with myogenesis, lipogenesis and angiogenesis of Nellore × Angus crossbred steers and heifers. Fifty-two pregnant Nellore cows, with an average initial body weight of 438 ± 48.9 kg were allocated to a randomized block design with a 3 × 2 factorial arrangement (3 treatments and 2 sexes of progeny). Cows were assigned to one of three treatments at 250 d of gestation: no VA injection (CON: 18 cows); VA injection in pregnant cows at 250 d of gestation (VAcow; 2,000,000 IU, 17 cows) and VA injection in newborn calves at birth and 60 d of age (VAcalf; 200,000 IU each dose, 17 cows). After weaning, the offspring were allotted into pens and feedlot finished for 207 d, steers and heifers were slaughtered at a commercial abattoir. Longissimus muscle samples were collected for gene expression analysis and meat quality assessment at 14 d of aging. Gene expressions were analyzed by RT-qPCR. Data were analyzed using the MIXED procedure of SAS 9.4 with fixed effects of VA injection, sex, and VA injection*sex interaction. The random effects were animal, AI group, and cow parity. There was no effect of VA on pH, cook lost, shear force and color index (L*, a*) (P > 0.10). However, muscle b* index was greater (P = 0.04) in VAcalf than all treatments. The expression of CPT2, DKL1, and ZNF423 genes were downregulated (P < 0.05) in VAcow compared to CON and VAcalf animals (Table 1). Meanwhile, the RXRA gene was less expressed (P = 0.05) in both VAcow and VAcalf animals. Regarding progeny sex, the expression of PPARG, CPT2, ACOX, GHR, MYH1, MYH2 genes were higher (P < 0.05) and MYH7 tended to be higher (P = 0.08) in females. However, PAX7 gene was higher (P = 0.05) in males. There was a treatment × sex interaction for the expression of ACACA (P = 0.05) and RXRG (P = 0.01) genes. For ACACA, VAcalf was less expressed in males but similar to the Control and VAcow in females, whereas in females, VAcalf was numerically the highest. For RXRG, VAcow was less expressed in males, while the Control showed the highest expression (0.11 vs. 1.00), with the latter also being the highest in females (0.77). Therefore, its concluded that the application of VA in pregnant cows or newborn calves does not affect color and shear force, and can alters the expression of myogenic and lipogenic genes, demonstrating that this vitamin has a long-term epigenetic effect on the offspring, whether its application occurs during the gestational phase or in the neonatal phase.