PSIII-23 Maternal metabolizable protein level and rumen-protected methionine impacts on beef steer progeny gene expression in muscle and liver

This experiment evaluated how maternal metabolizable protein level and rumen-protected methionine supplementation during late gestation impacts expression of genes associated with fetal programming in beef steer offspring. In a 3 x 2 factorial arrangement, 138 Angus crossbred cows were randomly assigned one of three metabolizable protein (MP) treatments (fed to meet 90, 100, or 110% of MP requirements), with(without) 9 g/d of rumen-protected methionine (MET; Smartamine®M, Adisseo Inc.). The isocaloric diets were fed for the last 8 weeks of gestation. Steer progeny (n = 51) were assigned to one of seven pens by weight and received a common corn-based grower diet (58% corn silage, 26% alfalfa haylage, 15% soybean meal) for 47 days, followed by a finisher diet (78% high moisture corn, 12% alfalfa haylage, 8% soybean meal) for 115 ±31.5 days until slaughter. At slaughter, samples of Sternomandibularis muscle and liver were collected and snap-frozen in liquid nitrogen for RNA isolation and analysis of gene expression for growth, myogenic, and adipogenic genes. Data were analyzed using PROC GLIMMIX in SAS, with maternal MP level and MET supplementation as fixed effects, and pen as a random effect. Exceeding maternal MP requirements increased expression of myogenic regulatory factor, myogenin (MYOG; 90% MP: 0.72, 100% MP: 0.94, and 110% MP: 1.00; SEM = 0.083, respectively; P = 0.02) in muscle from steer progeny at slaughter. Methionine supplementation decreased expression of pyruvate kinase (PKM; MET: 0.81, No MET: 1.16; SEM = 0.092; P = 0.02) in muscle, which is associated with lean tissue growth. Maternal nutritional treatment did not influence hepatic gene expression (P ≥ 0.06). These data suggest that maternal nutrition may impact progeny muscle development, while maintaining metabolic function of the liver.

The effects of rapeseed cake intake during the finishing period on the fatty-acid composition of the longissimus muscle of Limousin steers and changes in meat colour and lipid oxidation during storage

Context Cold-pressed rapeseed cake is a by-product of biodiesel manufacturing that can be obtained on-farm after simple mechanical extraction of the oil. It has a high crude fat content and contains significant amounts of linoleic acid, which make it a promising lipid supplement to modulate meat fatty acid profile. However, previous studies have indicated that using unsaturated fats in beef cattle diets could promote lipid oxidation and reduce meat redness. Aims The present study aimed to evaluate the effects of supplementation of intensively fattened beef steers with cold-pressed rapeseed cake on the fatty acid composition of beef fat and changes in measures of meat colour and lipid oxidation during 6 days of aerobic storage. Methods Sixteen Limousin steers were divided into two homogeneous groups and were fed ad libitum with barley straw and a concentrate mixture supplemented with either PROGRAS (PROGRAS at 2.7% of the diet, high in palmitic acid C16:0 from palm oil; CTR, experimental control; n = 8) or cold-pressed rapeseed cake (CPRC at 14.8% of the diet; CPRC treatment; n = 8) for a period of 9 months. The growth performance and carcass traits were assessed. The intramuscular fatty acids were analysed and the colour stability and lipid oxidation were measured in meat stored aerobically at 4°C for 0, 3 or 6 days. Key results Slaughter bodyweight and average daily gain were not affected by the inclusion of CPRC in the diet. Nor were there any changes in carcass weight, conformation or fatness. The longissimus thoracis from CPRC-fed animals depicted a higher UFA–SFA ratio and a lower atherogenic index than did that from animals fed CTR. Feeding CPRC increased the oleic acid , the vaccenic acid and the rumenic acid proportions in the muscle fat without affecting the ratio of C18:1 trans-10 to C18:1 trans-11. The extents of lipid oxidation and colour deterioration during aging were not affected by the dietary treatments. Conclusions The use of cold-pressed rapeseed cake as a lipid supplement in beef-steer diet improved the fatty acid profile of muscle fat without compromising meat oxidative stability, animal growth performance and carcass characteristics. Implications The supplementation of beef-steer diet with cold-pressed rapeseed cake could be an advantageous economical strategy allowing exploitation of an important by-product of small-scale biodiesel manufacturing to provide consumers with healthier meat.

198 Sale price of Holstein feeder steer lots relative to other breed descriptions sold through Superior Livestock video sales from 2010 through 2018

The objective was to determine relative value of Holstein feeder steer lots compared to steer lots of other breed descriptions sold through video auctions while adjusting for all other factors that significantly influenced sale price. Data were analyzed from 14,075 lots of feeder steers sold through 211 livestock video auctions from 2010 through 2018. All lot characteristics that could be accurately quantified or categorized were used to develop a multiple regression model that evaluated effects of independent factors on sale price using a backwards selection procedure. A value of P < 0.05 was used to maintain a factor in the final model. A lot was categorized into one of four breed descriptions: 1) English, English crossed, 2) English-Continental crossed, 3) Brahman influenced, 4) Holstein. Average weight and number of steers in lots analyzed was 363.2 ± 50.6 kg BW and 121.1 ± 110.3 head, respectively. English, English crossed lots sold for the greatest (P < 0.05) sale price ($152.39/45.36 kg). English-Continental crossed lots sold for the second greatest (P < 0.05) sale price ($150.61/45.36 kg). Brahman influenced sold for the third greatest (P < 0.05) sale price ($148.75/45.36 kg). Holstein lots sold for the lowest (P < 0.05) sale price ($110.56/45.36 kg). To determine potential change in relative value of Holstein feeder steers from 2010 to 2018, data were analyzed in three-year increments. In all three-year increments, Holstein feeder lots sold for the lowest (P < 0.05) sale price compared to the other breed descriptions of beef steer lots. The average discount of Holstein feeder lots relative to other breed descriptions was $33.19/45.36 kg BW in 2010–2012, $42.96/45.36 kg BW in 2013–2015, and was the greatest in 2016–2018 at an average discount of $46.24/45.36 kg BW, likely indicating lessening interest in the feedlot sector to feed Holstein steers to harvest.