David Contreras Marquez

Cottonseed meal is a suitable replacement for soybean meal in supplements fed to Nellore heifers grazing Brachiaria decumbens

The objective was to evaluate the effect of substituting soybean meal with cottonseed meal in supplements containing 15% and 30% of crude protein (CP), as well as evaluate the effect of supplementation use, on the performance and nutritional status of Nellore heifers. Forty heifers that were 13 months old and 250 ± 4 kg were kept in five 2.5-ha paddocks covered with Brachiaria decumbens. They were compared as they received different supplements (1 kg/head.day) in a 2 × 2 + 1 factorial – two protein sources (soybean and cottonseed meal) by two protein concentrations (15% and 30%) plus a Control treatment, which was a mineral mix only. The supplemented heifers showed greater weight gains, final bodyweight (P < 0.10) and higher intake of all evaluated nutrients (P < 0.10), as well as greater digestibility of these nutrients compared with those from the Control treatment. The animals fed supplements containing 15% CP had lower digestibility of dry matter, organic matter, CP and neutral detergent insoluble fibre corrected for ash and protein. These animals also had lower total digestible nutrients as compared with those which received a supplement containing 30% CP (P < 0.10). The treatments containing cottonseed meal provided greater dry matter digestibility (P < 0.10). Cottonseed meal can fully substitute soybean meal to grazing heifers during the rainy season. Supplements containing 30% of CP provided greater digestibility than 15% CP supplements. Supplemented animals had better performance.

Supplementation of grazing beef cows during gestation as a strategy to improve skeletal muscle development of the offspring

The appropriate supply of nutrients in pregnant cows has been associated with the optimal development of foetal tissues, performance of their progeny and their meat quality. The aim of this study was to evaluate supplementation effects of grazing cows in different stages of gestation on skeletal muscle development and performance of the progeny. Thereby, 27 Nellore cows were divided into three groups (n=9 for each group) and their progeny as follows: UNS, unsupplemented during gestation; MID, supplemented from 30 to 180 days of gestation; LATE, supplemented from 181 to 281 days of gestation. The percentage composition of the supplement provided for the matrices was the following: ground corn (26.25%), wheat bran (26.25%) and soya bean meal (47.5%). The supplement was formulated to contain 30% CP. Supplemented matrices received 150 kg of supplement (1 and 1.5 kg/day for cows in the MID and LATE groups, respectively). After birth, a biopsy was performed to obtain samples of skeletal muscle tissue from calves to determine number and size of muscle fibres and for messenger RNA (mRNA) expression analysis. The percentage composition of the supplement provided for the progeny was the following: ground corn grain (30%), wheat bran (30%), soya bean meal (35%) and molasses (5%). The supplement was formulated to contain 25% CP and offered in an amount of 6 g/kg BW. Performance of the progeny was monitored throughout the suckling period. Means were submitted to ANOVA and regression, and UNS, MID and LATE periods of supplementation were compared. Differences were considered at P0.10). Similarly, no differences were observed between calves for nutrient intake (P>0.10). However, greater subcutaneous fat thickness (P=0.006) was observed in the calves of LATE group. The ribeye area (P=0.077) was greater in calves born from supplemented compared with UNS cows. The supplementation of pregnant cows did not affect the muscle fibre size of their progeny (P=0.208). On the other hand, calves born from dams supplemented at mid-gestation had greater muscle fibre number (P=0.093) compared with calves from UNS group. Greater mRNA expression of peroxysome proliferator-activated receptor α (P=0.073) and fibroblast growth factor 2 (P=0.003) was observed in the calves born from MID cows. Although strategic supplementation did not affect the BW of offspring, it did cause changes in carcass traits, number of myofibres, and mRNA expression of a muscle hypertrophy and lipid oxidation markers in skeletal muscle of the offspring.