Strategies of virginiamycin supplementation in the postweaning phase on growth performance and carcass quality of beef cattle.

The present study evaluated the effects of supplementing VM in grazing cattle during the rearing phase on performance and carcass quality of beef cattle in the finishing phase. Two experiments with a randomized block design were conducted in consecutive years to contrast two post-weaning supplementation strategies using VM at 45 mg/100 kg body weight (BW). In the first year, treatments were protein supplement in the dry season and mineral supplement in the rainy season versus the addition of VM both in the protein and mineral supplements. In the second year, was contrasted with protein supplement in the dry season and protein-energy supplement in the rainy season. Performance, carcass traits, and carcass quality were evaluated at the end of both phases. In Year 1, adding VM in mineral supplement increased final backfat thickness (P=0.05), backfat gain (P=0.06), final rump fat thickness (P=0.02), and rump fat gain (P=0.01). In the finishing phase, VM-treated cattle had a greater dry matter intake (P=0.03) and tended to show a greater backfat thickness than non-treated cattle (P=0.07). In Year 2, no VM effects were observed on post-weaning phase performance and carcass traits. However, cattle-fed VM during the post-weaning phase tended to show a lower feed conversion ratio (P=0.09) and had a significantly higher gross feed efficiency (P=0.03) than non-treated cattle at slaughter. Virginiamycin supplementation during rearing on pasture improves performance and carcass fattening in the growth phase and has a residual effect in the finishing phase that may reflect greater backfat thickness and gross feed efficiency.

Maternal Nutrition Affects Nitrogen Isotopic Signature in Blood Plasma of Beef Cattle Dams and Their Offspring.

This study evaluated the effects of gestational supplementation strategy on nitrogen isotopic signature in blood plasma of beef cows and their progeny. The study comprised 15 pregnant Nellore cows divided into three different supplementation protocols: NP) non-programmed group; PP) cows receiving protein−energy supplement in the last third of pregnancy; and FP) cows receiving protein−energy supplement throughout the gestational period. Blood plasma from cows was sampled at the beginning of gestation, in the prepartum, and postpartum periods as well as from their calves at 30 and 180 days of age, for the analysis of stable isotope ratios 15 N/14 N. At pre- and postpartum periods, cows fed PP and FP presented greater abundance of δ15 N compared to NP (p < 0.05) at pre- and postpartum. All three groups showed significant differences (p < 0.05) in the postpartum period. The δ15 N values of calves at 30 days of age differed between the NP group and PP and FP groups (p < 0.05), with no difference (p > 0.05) at 180 days of age. The different gestational supplementation strategies influenced isotopic fractionation of nutrients of cows and their calves after birth, indicating effects on nutritional metabolism and cumulative behavior on isotope abundance related to consumption during gestation.

Effect of including oilseed grains in bovine diets on fatty acid profile, lipid stability, and sensory aspects of burgers.

The aim of this study was to evaluate the effect of including different oilseed grains in the diets of cattle on the qualitative and sensory characteristics and fatty acid profile of burger over a storage period of up to 120 days. The soybean diet increased 30% of ether extract in burgers when compared to the control diet. The inclusion of oilseeds in the bovine diet did not change the n-6/n-3 and hypocholesterolemic/hypercholesterolemic ratio, as well as the cholesterol levels in the burgers. The smallest flavor and aroma note scores were attributed to burgers produced with meat of bovine fed with cottonseed (4.35 and 4.67, respectively). The sunflower diet resulted in smaller lipid oxidation (1.03 mg/kg). The storage period increased lipid oxidation (0.43 and 1.97 mg/kg of malonaldehyde at 0 and 120 days, respectively). The inclusion of oilseeds in the diet of cattle does not change the ratios of fatty acids in burgers, which are important to human health. It is recommended to use soybean and sunflower grains in cattle diets to improve the sensory quality of burgers. A 30-day storage period is recommended to maintain the flavor and juiciness of beef burgers.

Slow-release urea in supplement fed to beef steers

Replacing regular urea (RU) by slow-release urea (SRU) at two levels of non-protein nitrogen (NPN) in concentrate, offered with low-quality roughage, was evaluated in beef steers on dry matter intake (DMI), ruminal fermentation parameters, plasma urea nitrogen (PUN), total tract apparent digestibility of diets and in situ degradability of nitrogen sources. Eight ruminally cannulated steers were allocated into two 4x4 Latin squares, totalizing four treatments: 40 NPN/0 SRU: 40% of concentrate crude protein (CP) as NPN, resulting from 0% of SRU and 100% of RU; 40 NPN/50 SRU: 40% of concentrate CP as NPN, resulting from 50% of SRU and 50% of RU; 40 NPN/100 SRU: 40% of concentrate CP as NPN, resulting from 100% of SRU and 0% of RU; 80 NPN/100 SRU: 80% of concentrate CP as NPN, resulting from 100% of SRU and 0% of RU. Results showed that partial substitution of regular urea by slow-release urea did not alter dry matter intake, pattern of ruminal fermentation or plasma urea nitrogen concentrations and increased the total tract apparent digestibility of crude protein in steers diets. The increase in non-protein nitrogen content in crude protein of the concentrate could compromise feed intake and the efficiency of nutrient utilization in the steers fed complete diets based on low quality forage.