Effects of energy density in close-up diets and postpartum supplementation of extruded full-fat soybean on lactation performance and metabolic and hormonal status of dairy cows.

This experiment was conducted to investigate the effect of energy density (ED) in the close-up period and supplementation of extruded full-fat soybean (ESB) during the first 4 wk after parturition on intake, body weight (BW), metabolic status, and performance of dairy cows. Fifty-seven Chinese Holstein cows with similar parity, previous 305-d milk yield, and expected calving date were dried off at -60 d relative to parturition and fed the standard herd dry-cow diet until -21 d relative to parturition. Energy density at low (LED, 1.25 Mcal/kg), medium (MED, 1.41 Mcal/kg) or high (HED, 1.55 Mcal/kg) levels of the close-up diets and postpartum supplementation of ESB at 0 kg/d (control, CON) or 1.5 kg/d (TRT) were used in a 3 × 2 factorial arrangement. All cows received the same CON diet from wk 5 to wk 8. As ED increased in the close-up diet, cows had higher dry matter intake and gained more BW and body condition score, and consequently were in improved energy balance status during the prepartum period, but lost more BW and more body condition score during the first 8 wk of lactation. Compared with LED cows, HED cows had higher blood concentrations of insulin and glucose, and lower nonesterified fatty acids (NEFA) prepartum, but had lower insulin concentration, higher leptin concentration and tended to have higher NEFA concentration postpartum. Milk production was not affected by the prepartum ED, although HED cows produced approximately 2 kg/d less milk than MED and LED cows during early lactation. Postpartum ESB supplementation elevated blood glucagon concentration regardless of prepartum ED during the first 4 wk of lactation. Interactive effects between prepartum ED and postpartum ESB supplementation were observed in blood concentrations of insulin, NEFA, bilirubin, total protein, albumin, and globulin. During early lactation, TRT decreased globulin concentrations in MED cows, and reduced NEFA and bilirubin concentrations in HED cows. Compared with CON, TRT cows had higher yields of milk (34.32 vs. 36.53 kg/d), milk lactose (1.63 vs. 1.74 kg/d), and solids-nonfat (2.98 vs. 3.18 kg/d), tended to have a greater yield of milk protein (1.11 vs. 1.17 kg/d), but tended to have lower milk fat percentage (4.18 vs. 3.94%) during the first 4 wk of lactation. In conclusion, compared with feeding the HED diet, feeding the LED diet during the close-up dry period had positive carryover effects on metabolism and production during early lactation, and the MED diet showed no advantage over the LED diet. Extruded full-fat soybean supplementation during the first 4 wk of lactation had positive effects on postpartum metabolic status, especially for those receiving the MED or HED diet prepartum, and resulted in an overall improved milk production during early lactation.