Effect of crop residues in haylage-based rations on the performance of pregnant beef cows

Pregnant beef cow's nutrition and its effects on postnatal weight and carcass quality of their progeny

A systematic review (SR) and meta-analysis (MA) were performed to evaluate the effects of different energy levels (metabolizable energy, ME) and crude protein (CP), supplied to pregnant cows, on weight of their progenies at 60 (BW60), 100 (BW100), 180 (BW180) and 205 (BW205) days of age, average daily gain (ADG), and weight, age, loin eye area (LEA), marbling and fat thickness (FT) at slaughter. The SR was performed on two electronic databases. The MA for random effects was performed for each response variable separately. The BW60 was reduced (P<0.001; I² = 78.9%) when cows consumed CP and ME above the required levels during the third trimester of pregnancy (3TRI). The BW205 was lower (P<0.001; I² = 92.6%) when cows consumed ME above the recommended levels in the second trimester of pregnancy (2TRI) and 3TRI. Conversely, the ADG was higher when cows consumed CP (P = 0.032; I² = 96.1%) and ME (P<0.001; I² = 96.1%) above the required levels. The steers whose mothers consumed CP and ME above the required levels during the 3TRI were slaughtered 5.5 days earlier (P = 0.015; I² = 98.5%) compared to other steers. The marbling was higher (P<0.001; I² = 91.7%) in calves born to mothers consuming CP and ME above the recommended levels, regardless of the gestation phase. The FT was higher (P<0.001; I² = 0%) in the offspring of cows that consumed CP and ME above the required levels during the 3TRI. Thus, CP and ME intake, at levels higher than those recommended by the NRC, by pregnant cows in the 3TRI reduces the progeny weight up to 205 days of age. However, this is advantageous during the finishing phase, as it reduces slaughter age and increases the ADG and carcass quality by improving marbling and FT.

Effect of moderate dietary restriction on visceral organ weight, hepatic oxygen consumption, and metabolic proteins associated with energy balance in mature pregnant beef cows

Twenty-two nonlactating multiparous pregnant beef cows (639 ± 68 kg) were used to investigate the effect of dietary restriction on the abundance of selected proteins regulating cellular energy metabolism. Cows were fed at either 85% (n = 11; LOW) or 140% (n = 11; HIGH) of total NE requirements. The diet consisted of a haylage-based total mixed ration containing 20% wheat straw. Cows were slaughtered by block (predicted date of parturition), beginning 83 d after the initiation of dietary treatments and every week thereafter for 6 wk, such that each block was slaughtered at approximately 250 d of gestation. Tissue samples from liver, kidney, sternomandibularis muscle, ruminal papilli (ventral sac), pancreas, and small intestinal muscosa were collected at slaughter and snap frozen in liquid N2. Western blots were conducted to quantify abundance of proliferating cell nuclear antigen (PCNA), ATP synthase, ubiquitin, and Na/K+ ATPase for all tissues; PPARγ, PPARγ coactivator 1 α (PGC-1α), and 5´-adenosine monophosphate-activated protein kinase (AMPK) and the activated form phosphorylated-AMPK (pAMPK) for liver, muscle, and rumen; phosphoenolpyruvate carboxykinase (PEPCK) for liver and kidney; and uncoupling protein 2 (UCP2) for liver. Statistical analysis was conducted using Proc Mixed in SAS and included the fixed effects of dietary treatment, cow age, block, and the random effect of pen. Dietary treatments resulted in cows fed HIGH having greater (P ≤ 0.04) ADG and final BW than cows fed LOW. Abundance of ubiquitin in muscle was greater (P = 0.009) in cows fed LOW, and PCG-1 α in liver was greater (P = 0.03) in cows fed HIGH. Hepatic O2 consumption was greater in HIGH (P ≤ 0.04). Feed intake can influence the abundance of important metabolic proteins and suggest that protein degradation may increase in muscle from moderately nutrient restricted cows and that energy metabolism in liver increases in cows fed above NE requirements.