Protein Supplementation during Mid-Gestation Alters the Amino Acid Patterns, Hepatic Metabolism, and Maternal Skeletal Muscle Turnover of Pregnant Zebu Beef Cows

Effects of Early Weaning on Performance and Carcass Quality of Nellore Young Bulls

This study compared early weaning (EW; 150 days) with conventional weaning (CW; 240 days) in Nellore young bulls, evaluating performance, carcass characteristics, and meat quality. A total of 74 non-castrated male calves were divided into two weaning strategies: EW (n = 37) and CW (n = 37). During the growth phase, which lasted 454 ± 14 d for EW calves and 359 ± 16 d for CW calves, animals received a protein-energy supplement at a ratio of 5 g per kg of body weight while grazing Brachiaria brizantha cv. Marandu. The animals were managed for an 87d finishing phase in three collective feedlot pens, with a 3-week adaptation protocol, starting with corn silage to a concentrate ratio of 55:45 and reaching a ratio of 30:70 in the final diet. Body weight, average daily gain (ADG), dry matter intake (DMI), feed efficiency (FE), carcass characteristics, and meat quality were evaluated. The EW group was approximately 44 kg lighter than the CW at the time of conventional weaning (p < 0.001). However, this weight difference did not influence ADG, DMI, and FE in the finishing phase. No significant differences were observed in carcass characteristics such as yield percentage, loin area, subcutaneous fat thickness, and meat quality, except for the weight of primal cuts, which was greater in the CW group (p < 0.001). Thus, although calves weaned early are lighter throughout subsequent production phases than those weaned conventionally, performance, efficiency, carcass yield, and meat quality are not affected.

Effect of pregnancy and feeding level on voluntary intake, digestion, and microbial nitrogen synthesis in Zebu beef cows

The objective of this research was to evaluate how pregnancy and feeding regimens affect the feed intake, digestibility, and efficiency of microbial nitrogen (N) synthesis in beef cows. Forty-four multiparous Nellore cows, comprising 32 gestating and 12 non-gestating cows, with an average weight of 451 ± 10 kg, were assigned to either a HIGH (ad libitum) or LOW (limited feeding at 1.2 times maintenance based on the NRC) feeding regimen during the gestational period. The dry matter intake (DMI) in kg/d was significantly greater (P < 0.01) in HIGH-fed cows. The DMI reduced (P < 0.05) in proportion to the shrunk body weight (SBW) as days of pregnancy (DOP) increased. The interaction between feeding level and DOP was significant (P < 0.05) for the digestibility of dry matter (DM), organic matter (OM), N compounds, ether extract (EE), ash- and protein-free neutral detergent fiber (NDFap), gross energy (GE), and total digestible nutrients (TDN). Except for DM and TDN digestibility, there was a reduced nutrient digestibility as gestation progressed in HIGH-fed cows. In contrast, digestibility increased as a function of DOP in LOW-fed cows. Microbial N synthesis (g/day) was significantly higher in HIGH-fed cows (P < 0.001) compared to LOW-fed cows. The efficiency of microbial N production per g of N intake and kg of digestible OM intake was (P = 0.021) and tended (P = 0.051) to be greater in LOW-fed cows compared to HIGH-fed cows. In summary, HIGH-fed Nellore cows reduce feed intake and digestibility with advancing gestation, affecting feed utilization. In addition, LOW-fed cows, showed higher microbial protein synthesis efficiency, potentially making them more nutrient-efficient under challenging nutritional conditions.

Maternal protein supplementation during mid-gestation improves offspring performance and metabolism in beef cows

This study examined the impact of maternal protein supplementation during mid-gestation on offspring, considering potential sex-related effects. Forty-three pregnant purebred Tabapuã beef cows (20 female and 23 male fetuses) were collectively managed in a pasture until 100 d of gestation. From 100 to 200 d of gestation, they were randomly assigned to the restricted group [(RES) - basal diet (75% corn silage + 25% sugar cane bagasse + mineral mixture); n = 24] or control group [(CON) - same basal diet + based-plant supplement [40% of crude protein, 3.5 g/kg of body weight (BW); n = 19]. From 200 d of gestation until parturition, all cows were equally fed corn silage and mineral mixture. During the cow-calf phase, cows and their calves were maintained in a pasture area. After weaning, calves were individually housed and evaluated during the backgrounding (255 to 320 d), growing 1 (321 to 381 d), and growing 2 (382 to 445 d) phases. Offspring's blood samples were collected at 210 and 445 d of age. Samples of skeletal muscle tissue were collected through biopsies at 7, 30, and 445 d of age. Muscle tissue samples were subjected to reverse-transcription quantitative polymerase chain reaction analysis. Prenatal treatment and offspring's sex (when pertinent) were considered fixed effects. The significance level was set at 5%. At mid-gestation, cows supplemented with protein reached 98% and 92% of their protein and energy requirements, while nonsupplemented cows attained only 30% and 50% of these requirements, respectively. The RES offspring were lighter at birth (27 vs. 31 kg), weaning (197 vs. 214 kg), and 445 d of age (398 vs. 429 kg) (P ≤ 0.05). The CON calves had greater (P < 0.05) morphometric measurements overall. The CON offspring had ~26% greater muscle fiber area (P ≤ 0.01). There was a trend (P = 0.06) for a greater Mechanistic target of rapamycin kinase mRNA expression in the Longissimus thoracis in the CON group at 7 d of age. The Myogenic differentiation 1 expression was greater (P = 0.02) in RES-females. Upregulation of Carnitine palmitoyltransferase 2 was observed in RES offspring at 445 d (P = 0.04). Expression of Fatty acid binding protein 4 (P < 0.001), Peroxisome proliferator-activated receptor gamma (P < 0.001), and Stearoyl-Coenzyme A desaturase (P < 0.001) was upregulated in CON-females. Therefore, protein supplementation during gestation enhances offspring growth and promotes favorable responses to lipogenesis, particularly in females.