Impacts of protein supplementation during late gestation of beef cows on maternal skeletal muscle and liver tissues metabolism

Abstract

Since nutritional requirements are increased at the end of gestation to meet the demands of the pregnant uterus, pregnant beef cows are susceptible to mobilization of body reserves (mainly fat and amino acids (AAs)) and to alter the metabolism of nutrients in the liver and muscle to support such demands. The objective of this study was to evaluate the effect of CP supplementation on maternal nutrient metabolism in the late gestation of beef cows grazing a low-quality pasture. Forty-three pregnant Nellore cows gestating male fetuses (average age = 6 years; average weight = 544 kg) at 193 ± 30 (mean ± SD) days (d) of gestation were divided into eight groups (experimental units, with four to five cows each). Treatments were (1) control (CON, n = 4): pasture-based (PB) diet without CP supplementation and (2) supplemented (SUP, n = 4): PB diet daily supplemented with 2 g/kg of BW of a 43.5% CP supplement. Liver and skeletal muscle biopsies were performed at 265 days of gestation and samples were collected for mRNA expression. On day 280 of gestation, blood samples were collected to assess plasma levels of AA. The CON-fed cows tended to have greater (P = 0.057) total circulating AA than SUP-fed cows. The circulating glycogenic AA was greater (P = 0.035) in CON than in SUP cows. CON cows was greater for histidine (P = 0.015), methionine (P = 0.007) and alanine (P = 0.036) than SUP cows. The CON- and SUP-fed showed no differences for gluconeogenesis, fatty acid transport and signaling axis markers in the liver. The mRNA expression of markers for skeletal muscle synthesis, p7056k (P = 0.060) and GSK3B (P = 0.096), tended to be greater in cows from CON than SUP group. No differences were found for mRNA expression of markers for skeletal muscle degradation. We conclude that CP supplementation to CP-restricted late-pregnant beef cows reduces the maternal tissue mobilization and changes the profile of plasma circulating AA and the mRNA expression of markers for the synthesis of skeletal muscle tissue.

The Effects of Prenatal Diet on Calf Performance and Perspectives for Fetal Programming Studies: A Meta-Analytical Investigation

“…In the late pregnancy, when most studies used in this meta-analysis were concentrated, the bovine fetuses presented an accelerated growth [ 57 ], which resulted in greater glucose and amino acid (AA) demands to attend to the fetus’s anabolism and its oxidative metabolism [ 58 ]. Consistent with this, there is evidence that pregnant beef cows receiving a low-protein diet tended to have a higher circulating pool of total AA and a greater glycogenic AA blood concentration than pregnant cows fed with protein supplementation, indicating the greater skeletal muscle catabolism to attend the fetal demand in un-supplemented beef cows [ 40 ]. This pattern was associated with a lower ADG for cows under a low-protein nutritional plan.…”

Changes in nutritional characteristics and performance of grazing Nellore cows during the peripartum phase receiving or not protein supplementation

“…In growing animals, the rumen is the priority, therefore, only after supplying the N needs in the rumen is the supplementary N destined for anabolic functions (Batista et al, 2016). On the other hand, in pregnant cows the priority destination of available N seems to reside in the gestational tissues (Bell and Ehrhardt, 2000;Lopes et al, 2020).…”

Prenatal origins of productivity and quality of beef

“…Maternal tissue mobilization or deposition occurs as a function of dietary substrate supplies (McNeill et al, 1997). Thus, nutritional adjustments for pregnant cows undergoing nutritional restrictions have been the subject of studies (Lopes et al, 2020), which, in general, aimed to establish nutritional management that minimizes lean tissue catabolism and the negative effects on the fetus. For instance, Lopes et al (2020) showed the importance of supplementation for undernourished beef cows and reported a tendency toward greater mRNA expression of skeletal muscle synthesis markers in cows that received protein supplementation during late gestation.…”