Ruminal undegradable protein enriched diet during late gestation of beef cows affects maternal metabolism and offspring’s skeletal muscle development

Abstract

We aimed to investigate the impacts of ruminal undegradable protein (RUP) enriched diet during late gestation on performance of pregnant beef cows and skeletal muscle growth of the offspring. From 180d of gestation to parturition, a total of 31 Brahman pregnant cows were randomly assigned to one of the experimental treatments: High-RUP diet (H-RUP, n = 17), and control diet (CTRL, n = 14). Maternal results showed no differences (P > 0.05) in dry matter intake, and total digestible nutrients intake between treatments. However, crude protein intake and the RUP intake were greater (P < 0.01) in H-RUP, while CTRL group had greater (P < 0.01) rumen degradable protein intake. Cows from H-RUP group were heavier (P < 0.01) at parturition and had greater (P = 0.01) average daily gain. Blood levels of nitric oxide tended (P = 0.06) to be greater in H-RUP, while blood glucose levels were not altered (P > 0.60) by RUP-enriched diet. Blood aminoacidic profile showed greater (P = 0.02) concentrations of methionine in CTRL group, and greater (P < 0.01) concentrations of the branched chain amino acids in H-RUP cows. A greater (P = 0.04) number of muscle fibers were observed in the H-RUP offspring, while a tendency (P = 0.07) of greater muscle fiber diameter was observed in CTRL offspring. Gene expression analysis indicated higher (P < 0.01) expression of the satellite cells marker (PAX7) in CTRL offspring. In contrast, the expression of the markers of fibro-adipogenic progenitor cells (PDGFRα), and adipogenesis (ZFP423, PPARγ, C/EBPα) were higher in the skeletal muscle of H-RUP offspring. Consistently, at the protein level the greater abundance of ZFP423 (P = 0.03), and PPARγ (P = 0.01) were observed in H-RUP offspring. Moreover, the expression of the fibrogenic marker (TGFβ) was higher (P = 0.01) in H-RUP offspring. Our findings suggest that supplementing pregnant beef cows during late gestation may increase the availability of amino acids, responsible to maintain maternal body conditions and to change the skeletal muscle characteristics of the offspring. Since the resulting offspring from H-RUP treatment showed greater number of muscle fiber and an increase in the process of intramuscular adipogenesis our data suggest that a RUP-enriched diet for pregnant cows at late gestation may be beneficial for the achievement of better carcasses at slaughter. However, the feeding strategy showed no changes in the offspring’s performance during the growing phase.