Negative energy balance during early postpartum is associated with reduced reproductive performance in dairy cows.
A pooled statistical analysis of seven studies completed in our group from 1993 to 2010 was conducted to investigate the association between prepartum energy feeding regimen and reproductive performance. The interval from calving to pregnancy (days to pregnancy, DTP) was the dependent variable to assess reproductive performance. Individual data for 408 cows (354 multiparous and 54 primiparous) were included in the analysis. The net energy for lactation (NEL) intake was determined from each cow’s average dry matter intake and calculated dietary NEL density. Treatments applied prepartum were classified as either controlled-energy (CE; limited NEL intake to ≤100% of requirement) or high-energy (HE; cows were allowed to consume >100%) diets fed during the far-off (FO) or close-up (CU) dry periods. Cow was the experimental unit.
The Cox proportional hazard model revealed that days to pregnancy was shorter for CE (median=157days) than HE (median=167days) diets during the CU period [hazard ratio (HR)=0.70]. Cows fed HE diets during the last 4weeks prepartum lost more body condition score in the first 6weeks postpartum than those fed CE diets (−0.43 and −0.30, respectively).
Cows fed CE diets during the FO period had lower nonesterified fatty acids concentrations in week 1, 2 and 3 of lactation than cows fed HE diets. Higher nonesterified fatty acids concentration in week 1 postpartum was associated with a greater probability of disease (n=251; odds ratio=1.18). Cows on the CE regimen during the FO period had greater plasma glucose concentrations during week 1 and week 3 after calving than cows fed the HE regimen.
Higher plasma glucose (HG) concentration compared with lower glucose (LG) in wk 3 (HG: n=154; LG: n=206) and week 4 (HG: n=71; LG: n=254) after calving was associated with shorter days to pregnancy (week 3: median=151 and 171d for HG and LG, respectively, and HR=1.3; week 4: median=148 and 167days, respectively, and HR=1.4). In the first 2weeks after calving, cows that received HE diets in the FO period had higher concentrations of total lipids and triglyceride and greater ratio of triglyceride to glycogen in liver than cows fed CE diets.
In conclusion, cows fed CE diets during the CU period had a shorter interval between parturition and conception, which may be explained by increased NEL intake during the first 4weeks postpartum and lower incidence of peripartal diseases. Lower body condition score loss during the first 6weeks postpartum and slightly higher glucose concentration at wk 3 likely contributed to improved reproductive performance.
Source: Journal of Dairy Science