Influence of pregnancy in mid-to-late gestation on circulating metabolites, visceral organ mass, and abundance of proteins relating to energy metabolism in mature beef cows1,2

Abstract

In mid-to-late gestation, nutrient demand increases to meet the growth requirements of the conceptus and cows may alter metabolism in response to energy demands of pregnancy. By better understanding the metabolic role of pregnancy, there may be opportunities to better understand maintenance energy costs and improve overall feed efficiency. Eighteen mature Simmental/Angus crossbred cows, pregnant (PREG; n = 9) and nonpregnant (OPEN; n = 9), were used to investigate the effect of pregnancy on BW change, carcass traits, visceral organ mass, and circulating serum metabolites. Cows were blocked by day of expected parturition such that each block was slaughtered 4 to 5 wk before parturition. Cows were individually fed for ad libitum intake using Calan gates for 89 to 105 d. Cows were weighed, ultrasounded for rib (over the 12th and 13th rib) and rump fat, and a serum sample obtained at d 1, 56, and 3 to 5 d before slaughter. At slaughter, organs were removed, trimmed of fat, and weighed. Serum was analyzed for β-hydroxybutyrate (BHBA), NEFA, glucose, urea, total cholesterol, and triiodothyronine (T3). Tissue samples from liver, kidney, sternomandibularis muscle, ruminal papillae, pancreas, and small intestinal mucosa were collected at slaughter and snap frozen in liquid N. Western blots were conducted to quantify abundance of: proliferating cell nuclear antigen (PCNA), ATP synthase, ubiquitin, and Na(+)/K+ ATPase for all tissues; PPARγ, PPARγ coactivator 1α (PGC1-α), 5'-adenosine monophosphate-activated protein kinase (AMPK) and phosphorylated-AMPK (pAMPK) for liver, muscle, and rumen; phosphoenolpyruvate carboxykinase (PEPCK) for liver and kidney; and uncoupling protein 2 (UCP2) for liver. Data were analyzed using PROC MIXED in SAS as a replicated randomized complete block. Liver weights (actual, relative to BW, relative to HCW) were heavier (P ≤ 0.02) in OPEN. Rumen mass and kidney fat weight, both relative to BW, were also greater (P ≤ 0.04) in OPEN. On d 56 and at preslaughter, PREG cows had greater (P ≤ 0.04) BHBA, NEFA and urea concentrations and lower (P = 0.04) cholesterol concentration. Hepatic Na(+)/K+ ATPase abundance was greater (P = 0.04) in PREG cows. In rumen papillae, abundance of pAMPKα was increased (P = 0.006) in PREG cows. These data indicate that PREG cows may metabolize energy reserves and alter their metabolism to meet the energetic demands of the growing fetus.

The influence of pregnancy and plane of nutrition during pregnancy on pancreatic digestive enzymes and insulin-containing cell cluster morphology in beef cows

“…Final body weight (BW) did not differ between OPEN and PREG cows (Table 1) as reported previously (Wood et al 2013b). Pancreas weight (g and g kg −1 ), and protein concentration and content (mg g −1 and g per pancreas), did not differ between OPEN and PREG cows.…”

“…a OPEN refers to nonpregnant cows (n = 9); PREG refers to pregnant cows (n = 9). ultrasound fatness measurements (rib fat and rump fat) were not different between treatments (Wood et al 2013b). However, carcass marbling score tended to be greater in OPEN than PREG cows (Wood et al 2013b) suggesting that cows were at different energy statuses.…”

“…ultrasound fatness measurements (rib fat and rump fat) were not different between treatments (Wood et al 2013b). However, carcass marbling score tended to be greater in OPEN than PREG cows (Wood et al 2013b) suggesting that cows were at different energy statuses. Differences in energy balance between OPEN and PREG cows are also supported by the increase in NEFA, urea N, and β-hydroxybutyrate and no differences in DMI and ADG between treatments (Wood et al 2013b).…”

“…The experiments were approved by the University of Guelph Animal Care Committee and the animals were cared for according to the guidelines of the Canadian Council of Animal Care (1993). Animal care and experimental design were described previously (Wood et al 2013a(Wood et al , 2013b.…”

“…For experiment 1 (Wood et al 2013b), 18 mature [n = 9 nonpregnant (OPEN) and n = 9 pregnant (PREG)] cows primarily of Angus and Simmental crossbreeding were used in a replicated, randomized complete block design to determine the effects of pregnancy on pancreatic function. Cows were 5.33 ± 2.8 yr old and went through at least one successful pregnancy before start of the trial.…”