Reproductive Performance of Beef Heifers Supplemented with Corn Gluten Feed and Rumen-Protected Fat before Breeding

The Effects of Age at Weaning and Length of Lipid Supplementation on Growth, Metabolites, and Marbling of Young Steers

Simple Summary

Consumers value quality beef and producers are starting to look at the ways production decisions affect the long-term performance of the animals. Early weaning is a production option in many beef cattle production environments. We are looking at the addition of rumen by-pass lipids in addition to early weaning to increase the marbling of steers. The supplementation of rumen protected lipids’ increased plasma concentrations of fatty acids. Supplementation of rumen-protected lipids improved carcass quality of young steers by increasing marbling scores and lipid concentration of steaks without negatively impacting dressing percentage. Therefore, a combination of early weaning and rumen by-pass lipid supplementation can be used as management practices to meet current consumer demands.

Abstract

The objective of this study was to determine how weaning age, days on supplements, and lipid supplementation affected the growth and marbling deposition of steers. Steers from a single sire were early weaned (n = 24) at 150 ± 11 days of age or traditionally weaned (n = 24) at 210 ± 11 days of age. Steers were assigned to control (n = 12/weaning group) or an isocaloric, isonitrogenous rumen by-pass lipid (RBL, n = 12/weaning group) for either 45 (n = 6/treatment) or 90 (n=6/treatment) days then harvested. Steer body weight (BW) was recorded on days −14 and −7, then BW and blood samples were collected on days 0, 22, 45, 66, and 90. The right rib section of each animal was collected for proximate analysis. Longissimus dorsi from RBL steers had increased lipids compared with control steers (3.6 ± 0.2 vs. 2.4 ± 0.2% on a wet basis; p < 0.0001). Steers fed for 90 days had greater (p = 0.02) concentrations of Longissimus dorsi lipid (3.3 ± 0.2%) than those fed for 45 days (2.7 ± 0.2%). There was a weaning age by treatment by days on feed interaction for intramuscular adipocyte diameter (p = 0.02) in which early weaned RBL fed for 90 days steers had an increased adipocyte diameter compared to the early weaned control fed for 90 and early weaned fed for 45 days steers with all other treatment groups as intermediates. Supplementation of RBL increased concentrations of C18:2, C20:4, and total fatty acids on days 45 and 90 (p ≤ 0.05). Data show that RBL supplementation increased the marbling content of the Longissimus dorsi. Furthermore, a longer period of supplementation resulted in increased adipose diameter.

The effect of supplementing rumen undegradable unsaturated fatty acids on marbling in early-weaned steers

The objective of this study was to determine if supplementation with a rumen undegradable unsaturated fatty acids (FA) source improved marbling deposition in early-weaned steers. All steers (Angus, = 23; Angus × Hereford, = 24) were weaned at 150 ± 5 d of age. Steers were blocked by BW and breed and then randomly assigned to either control (CON; average 1.5 kg of corn gluten feed [CGF], = 23) or isocaloric supplementation containing a rumen undegradable fat source (RUF; 200 g of Megalac-R added to an average of 1.06 kg of CGF, = 24) offered 5 d/wk for 110 d. All steers had ad libitum access to pastures throughout treatment and received supplements individually. Steer BW and blood samples were collected at 0, 55, and 110 d of supplementation, and real-time ultrasound measurements were collected at d 110. Following treatment, steers were transported to Oklahoma State University for finishing and subsequent harvesting at a commercial plant. All data were analyzed using the PROC MIXED procedure of SAS either as repeated measures or ANOVA depending on parameters. There were no significant changes in BW from the beginning of treatment to harvest due to treatment. Ultrasound data showed that RUF steers tended ( = 0.08) to have more i.m. fat than CON at d 110. Serum concentrations of FA showed a treatment × day interaction ( < 0.02) for 16:0, 18:0, 18:1-9, 18:2, 20:4, and total FA. These specific FA concentrations slightly increased in CON steers, but there was a more pronounced increase in the concentration of these FA across the supplementation period in RUF steers. Serum triglyceride and cholesterol concentrations were increased ( < 0.01) on d 55 and 110 in RUF steers compared with those in CON steers. Serum leptin concentration in RUF steers was greater ( < 0.01) than CON steers at d 110. After harvest, RUF carcasses had greater ( = 0.01) marbling scores than those of CON carcasses. All other carcass measures were similar between treatments. The percentage of total lipids was increased ( = 0.011) in steaks from RUF compared to CON. There was a decrease ( < 0.05) in adipocyte diameter in i.m. fat depot of RUF steers compared to CON. There was also a tendency ( = 0.06) for RUF steers to have a greater percentage of 20 to 30 μm adipocytes in their i.m. depot than CON steers. This study indicates that supplementation of unsaturated FA can positively impact marbling deposition in early-weaned steers without impacting other carcass measures.

Maternal obesity markedly increases placental fatty acid transporter expression and fetal blood triglycerides at midgestation in the ewe

Obesity of women at conception is increasing, a condition associated with offspring obesity. We hypothesized that maternal obesity increases placental fatty acid transporter (FATP) expression, enhancing delivery of fatty acids to their fetuses. Sheep are a commonly utilized biomedical model for pregnancy studies. Nonpregnant ewes were randomly assigned to a control group [100% of National Research Council (NRC) recommendations] or obese group (OB, 150% of NRC) from 60 days before conception to 75 or 135 days of gestation (dG; term = 150 dG), when placental cotyledonary tissue was collected for analysis. Fetuses of OB ewes were markedly heavier (P < 0.05) on 75 dG than fetuses from control ewes, but this difference disappeared by 135 dG. Maternal obesity markedly increased (P < 0.05) cholesterol and triglyceride concentrations of both maternal and fetal blood. There is no difference in lipoprotein lipase mRNA expression between control and OB group at either gestational age. On 75 dG, the mRNA expression of FATP1 (P < 0.05), FATP4 (P = 0.08), and fatty acid translocase CD (cluster of differentiation) 36 (P < 0.05) proteins were more enhanced in cotyledonary tissue from OB than control ewes; consistently, protein expression of FATP1 and FATP4 was increased (P < 0.05). Similarly, on 135 dG, the mRNA levels of FATP1, FATP4, and CD36 were all higher (P < 0.05), but only FATP4 protein content was enhanced (P < 0.05) in OB cotyledonary tissue. Peroxisome proliferator-activated receptor (PPAR)-γ regulates the expression of FATPs. Both the mRNA expression and protein content of PPARγ were increased in OB cotyledonary in the midgestation. In conclusion, maternal obesity enhances the mRNA expression and protein content of FATPs in cotyledonary in the midgestation, which is associated with higher PPARγ content in cotyledonary.

Maternal obesity up-regulates inflammatory signaling pathways and enhances cytokine expression in the mid-gestation sheep placenta

Obesity in pregnant women is a growing public health concern. The placenta is a source of cytokines which can induce maternal gestational insulin resistance and alter nutrient transport to the fetus. Obesity induces placental inflammation at term, but the impact of obesity on placental inflammation earlier in pregnancy has not been defined. Using sheep as an experimental model, we hypothesized that maternal obesity (MO) would induce inflammation in the cotyledonary (COT) tissue of the placentome by mid-gestation. Nonpregnant ewes were randomly assigned to a control (C, 100% of NRC recommendations) or obese (OB, 150% of NRC) group from 60 days before conception to 75 day of gestation (dG), when ewes were necropsied and placental COT tissue collected for analyses. Free fatty acids content, triglyceride and cholesterol content were higher (P < 0.05) in the fetal plasma of OB compared to C ewes on day 75. MO increased mRNA levels of toll-like receptor (TLR) 2 (P < 0.05) and TLR4 (P = 0.06), macrophage markers cluster of differentiation (CD)11b (P = 0.06), CD14 and CD68 (P < 0.05), and proinflammatory cytokines tumor necrosis factor (TNF)alpha (P < 0.01), interleukin (IL)-6 (P < 0.05), IL-8(P < 0.01) and IL-18 (P = 0.06), in COT tissue. Inflammatory c-Jun N-terminal kinase (JNK)/c-Jun and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB) signaling pathways were up-regulated (P < 0.05) in COT of OB ewes. In conclusion, MO enhanced the placental inflammatory response in OB ewes at mid-gestation, possibly as a result of increased TLR4 and free fatty acids.