Glucose and acetate metabolism in bovine intramuscular and subcutaneous adipose tissues from steers infused with glucose, propionate, or acetate

Abstract

We hypothesized that abomasal infusion of glucose would promote de novo fatty acid biosynthesis from glucose in vitro in bovine intramuscular (i.m.) and subcutaneous (s.c.) adipose tissues to a greater extent than ruminal infusion of acetate, propionate, or glucose. Angus crossbred steers (n = 24), 22 mo of age, were fitted with ruminal cannulas, and steers were adapted to another corn/sorghum finishing diet over a 2-wk period while recovering from the placement of the cannulas. After the adaptation period, the steers were fed the second finishing diet at 130% of their voluntary intake and were infused with isocaloric amounts (3.76 Mcal/d) of glucose, propionate, or acetate for 35 d. Glucose was infused either into the rumen or into the abomasum, whereas propionate and acetate were infused into the rumen. Acetate infusion decreased DM and DE intakes (P < 0.05). The 5th to 8th longissimus muscle section was removed immediately and transported to the laboratory within 10 min post-exsanguination in 38 °C, oxygenated Krebs Henseleit buffer containing 5 mM glucose and 5 mM acetate. Intramuscular and s.c. adipose tissues were dissected from the muscle and incubated in vitro in 5 mM glucose plus 5 mM acetate (containing [U-14C]glucose or [1-14C]acetate). Lipid content was lower (P = 0.04) in i.m. adipose tissue of the acetate-infused steers than in the other treatment groups, and i.m. adipocytes from acetate-infused steers were smaller (P = 0.01) than those from propionate-infused steers. The rate of incorporation of acetate into glyceride-fatty acids (GFA) in i.m. and s.c. adipose tissues was greater (P < 0.03) in steers receiving ruminal or abomasal infusions of glucose than in adipose tissues from steers infused with acetate. The greatest rates of GFA synthesis were observed in s.c. adipose tissue from steers infused ruminally with propionate or abomasally infused with glucose (P < 0.001). In i.m. and s.c. adipose tissues, the proportion of acetyl units from acetate incorporated into GFA was greater in steers receiving glucose infusion in the rumen or abomasum than in steers receiving acetate or propionate infusion (P < 0.05). Contrary to our hypothesis, abomasal glucose infusion did not promote greater fatty acid biosynthesis from glucose in i.m. adipose tissue than ruminal glucose infusion. However, glucose infusion caused the greatest production of acetyl units from acetate in i.m. and s.c. adipose tissues.

The colour and sensory characteristics of longissimus muscle from beef cattle that grazed grass or consumed concentrates prior to slaughter

“…The growth rates in the different periods within each experiment were as expected based on the management strategies imposed and the carcass conformation and fatness scores were largely similar. The lower IMF concentration in the grass‐fed beef (significantly so in Experiments 2 and 3) despite the similar carcass fatness score within each experiment may reflect the different substrate requirement and supply (acetate versus propionate from grass and concentrate diets) for lipid synthesis in subcutaneous and intramuscular adipocytes 18 …”

Effects of the Duration of Zilpaterol Hydrochloride Supplementation and Days on Feed on Performance, Carcass Traits and Saleable Meat Yield of Nellore Bulls

“…The blood glucose concentration was very similar across all treatments 3 d prior to slaughter. However, blood glucose concentration was lower when bulls were confined for 117 d due to higher energetic demand to synthesize fat tissue towards the end of the current trial [ 39 ]. Greater blood NEFA concentration observed in bulls confined for 117 d represents a different metabolic stage in comparison to those bulls confined for 90 d [ 40 ].…”

Cattle adapted to tropical and subtropical environments: social, nutritional, and carcass quality considerations

“…Intramuscular adipocytes were smaller than subcutaneous adipocytes (Schiavetta et al, 1990;Miller et al, 1991;Campbell et al, 2016;Smith et al, 2018) and the rate of de novo fatty acid synthesis was less in intramuscular adipose tissue across subspecies (Smith and Crouse, 1984;Miller et al, 1991;Campbell et al, 2016;Smith et al, 2018). In Miller et al (1991), intramuscular and subcutaneous adipocyte volumes were less in Santa Gertrudis (B. indicus) steers compared with Angus (B. taurus) steers (Figure 6), consistent with the lower marbling score and AFT for the Santa Gertrudis ( Enzymes associated with de novo fatty acid biosynthesis, as well as glucose and acetate incorporation into fatty acids, were also measured across these experiments (Smith and Crouse, 1984;Miller et al, 1991;Smith et al, 2018). For example, NADP-malate dehydrogenase (NADP-MDH) activity was less in intramuscular and subcutaneous adipose tissues from B. indicus-influenced steers than in B. taurus steers (Miller et al, 1991; Figure 6).…”

“…For example, NADP-malate dehydrogenase (NADP-MDH) activity was less in intramuscular and subcutaneous adipose tissues from B. indicus-influenced steers than in B. taurus steers (Miller et al, 1991; Figure 6). Greater NADP-MDH activity usually indicates greater capacity to incorporate glucose into fatty acids (Prior et al, 1981;Smith and Prior, 1981;Smith and Crouse, 1984;Smith et al, 2018), but the rate of fatty acid synthesis from glucose was not different in intramuscular and subcutaneous from B. indicus-influenced and B. taurus steers (Figure 6). Instead, the rate of fatty acid synthesis from acetate was less in intramuscular adipose tissue from B. indicusinfluenced than in intramuscular adipose tissue from B. taurus steers.…”