The aim of this study was to determine the potential for accumulation of deoxynivalenol (DON) in yellow mealworm larvae (Tenebrio molitor) reared on high DON Fusarium-infected wheat and investigate the effects on production, survival and nutritional traits. Wheat containing 200 μg/kg DON was used as the control diet. A different source of wheat was sorted into six fractions and mixed to obtain low (2000 μg/kg), medium (10,000 μg/kg) and high (12,000 μg/kg) levels of DON. Each diet was replicated five times with 300 or 200 mealworms per replicate for the feeding and breeding trials, respectively. Trial termination occurred when the first two pupae were observed (32–34 days). There was no difference in the concentrations of DON detected in the larvae between diets that ranged from 122 ± 19.3 to 136 ± 40.5 μg/kg (p = 0.88). Excretion of DON was 131, 324, 230 and 742 μg/kg for control, low, medium and high, respectively. Nutritional analysis of larvae showed maximum crude protein of 52% and crude fat of 36%. Ash, fiber, chitin, fatty-acids and amino-acid content were consistent across diets. Survival was greater than 96% for all life stages and average daily gain ranged from 1.9 ± 0.1 to 2.1 ± 0.1 mg/day per mealworm. Larvae accumulated low levels of DON from Fusarium-infected wheat diets suggesting contaminated wheat could be used to produce a sustainable, safe protein source.

A novel SNP was discovered within the promoter region of alcohol dehydrogenase 1C (ADH1C c.-64T>C), the C allele eliminating a potential binding site for the transcription factor C/EPBα. The purpose of this study was to examine if an interaction between this SNP and vitamin A restriction had an effect on carcass characteristics in beef cattle. Following backgrounding on a β-carotene-deficient diet, 130 steers (50 TT, 50 CT, and 30 CC) were finished for 5 mo and received either no supplemental vitamin A (unsupplemented) or 750,000 IU/mo (supplemented). A subgroup of 5 steers•genotype⁻¹•treatment⁻¹ was randomly selected for pre- and postfinishing liver biopsies to assess vitamin A status and measure gene expression. Unsupplemented steers (Bos taurus) had significantly greater (P < 0.05) marbling scores than supplemented steers. There was a significant interaction between genotype and vitamin A supplementation on ether-extractable intramuscular fat (IMF). Within the unsupplemented treatment, TT steers had nearly 23% greater IMF than CC steers. Additionally, unsupplemented TT steers had over 24% greater IMF than supplemented TT steers. Expression of ADH1C in the liver was additive with each additional T allele, potentially due to the elimination of a possible binding site for C/EBPα. It is plausible that CC cattle have reduced ability to metabolize retinol to retinaldehyde (and subsequently retinoic acid) and that a phenotypic effect is only observed when vitamin A is limiting. Therefore, ADH1C c.-64T>C genotype, in combination with reduced vitamin A supplementation, could potentially be implemented in marker-assisted management to maximize marbling in finishing cattle.

Previously, the single nucleotide polymorphism in alcohol dehydrogenase (ADH1C c.-64T>C) was shown to have an association with intramuscular fat (IMF) in the longissimus thoracis (LT) muscle when vitamin A was limited in finishing rations of beef steers. The purpose of this study was to determine the optimum vitamin A supplementation level, in combination with ADH1C genotype, to increase IMF of the LT muscle. In total, 45 TT genotype, 45 CT and 27 CC Black Angus crossbred steers were backgrounded on a commercial ration containing 3360 IU vitamin A/kg dry matter (DM). During finishing, the steers were randomly assigned to one of three vitamin A treatments at 25%, 50% and 75% of the National Research Council recommendation of 2200 IU/kg DM. Treatments were administered via an oral bolus. Carcass quality was evaluated and a sample from the LT muscle was collected for analysis of IMF. A treatment×genotype interaction (P=0.04) was observed for IMF; TT steers on the 75% treatment had higher IMF relative to CT and CC steers on the same treatment. Western blot analysis showed that TT steers had higher (P=0.02) ADH1C protein expression in hepatic tissue. Previously, TT steers exhibited increased IMF when fed limited vitamin A. In the current study, the lack of variation in IMF between treatments and genotypes at the lower vitamin A treatment levels was likely due to the majority of the steers grading Canada AAA (USDA Choice). However, the western blot data supports that TT steers are expected to have higher IMF deposition, due to an increased production of ADH1C. The interaction between ADH1C genotype and vitamin A supplementation level has the potential for use in marker-assisted management programs to target niche markets based on increased marbling.

Carcass quantity (lean meat yield) and quality (degree of marbling) in beef cattle determines much of their economic value. Consequently, it is important to study genes that are part of the appetite pathway and that may ultimately affect carcass composition. Pro-opiomelanocortin is a prohormone that codes for many different peptides, several of which are involved in the appetite pathway. A single nucleotide polymorphism (SNP) c.288C>T in pro-opiomelanocortin (POMC) has previously been associated with hot carcass weight (HCW) and shipping weight (Ship wt) in beef cattle.

A single nucleotide polymorphism (SNP) in the bovine leptin gene has been associated with carcass traits and elevated gene expression. To examine the relationship between leptin genotype with serum leptin concentration and carcass traits, blood samples were collected 24 h prior to slaughter in 89 head of cattle. Cattle were predominantly of Angus (n = 26), Hereford (n = 31) and Charolais (n = 32) breed types with approximately half homozygous for the T allele or the C allele. Cattle were limit fed to achieve 1 kg d^-1 liveweight gain for a 70-d background period while during finishing, animals were fed ad libitum such that half the animals within each breed type were slaughtered at 8 or 12 mm back fat determined by ultrasound. Preslaughter serum leptin and insulin were determined using radioimmunoassays (RIA) specific for cattle and sheep. Animals homozygous for the T allele had greater (P < 0.05) backfat depth at the beginning (2.4 ± 0.49 vs. 1.8 ± 0.49 mm) and end (3.1 ± 0.42 vs. 2.4 ± 0.42 mm) of the backgrounding period and reached target finishing back fat depths at lighter (P < 0.01) weights (548.2 ± 20 vs. 588.0 ± 20 kg) and in fewer (P < 0.05) total days on feed (179.3 ± 13 vs. 195.2 ± 13 d) than homozygous C animals. Leptin genotype effects on serum leptin concentration were confined to a three-way interaction such that TT Charolais fattened to 12 mm had significantly higher serum leptin levels than CC animals. Leptin concentration was correlated positively with measurements of fat (e.g., average ultrasound fat depth at end of test r = 0.45, P < 0.01). Results are consistent with an increased rate of fat deposition associated with the T allele in leptin. Key words: Beef cattle, leptin, carcass, yield