Effect Of Dry Period Dietary Energy Density On Performance And Metabolism Of Dairy Cows

The studies on different energy diets during dry period of dairy cows on their production performance, blood biochemical indicators and Hormone Indicators about energy metabolism and ingestion were developed. 30 Chinese Holstein cows during dry period being the proportional age, parity and body condition, clinical health, were randomly allocated into three different energy level groups. The three groups were respectively fed net energy of lactation(NEL), 1.2 Mcal/kgDM(Group A, GA), 1.3 Mcal/kgDM(Group B, GB) and 1.4 Mcal/kgDM(Group C, GC) of the diets for 8 weeks before the calving. All cows were offered the same diet with NEL=1.66 Mcal/kgDM after calving when the studies completed. Milk yields, milk components, body condition score, blood-biochemistry indicators and hormone indicators about energy metabolism and ingestion were measured during this period. Experimental results show that: 1. The group with NEL= 1.3 Mcal/kgDM(GB) and NEL= 1.4Mcal/kgDM(GC) cows increase milk yields in postpartum, while the group with NEL= 1.2 Mcal/kgDM(GA) cows decrease milk performance, 14.5% lower milk yields than GC, but there were no significant difference between the groups of milk components. 2. The GA cows significantly decrease postpartum blood β-hydroxybutyric acid(BHBA) and the non-esterified fatty acids(NEFA) concentrations, reduce body fat mobilization, reduce the falling level of postpartum body condition and effectively relieve negative energy balance(NEB) in postpartum; While the GC cows increase postpartum blood BHBA and NEFA concentrations, increase NEB of postpartum, and worsen condition of body. The higher energy intake tended to promote the occurrences of energy metabolism diseases such as ketone body and fat liver. 3. The GC cows increase postpartum blood growth hormone(GH) and glucagons(GN) concentrations, and there is no significant difference between the groups of insulin(INS). The change of the three hormone indicators suggest that GC cows’ body fat mobilized seriously and increased NEB of postpartum. 4. The GA cows induce more concentration of leptin(LEP) than the GB and GC cows; relieve the state NEB or /and energy lack after calving. 5. The GA cows increase more postpartum blood concentration of neuropeptide(NPY) than GC, increase intake of cows, and effectively relieve the NEB.