Consequences of Transition Treatments on Fertility and Associated Metabolic Status for Dairy Cows in Early Lactation

SIMPLE SUMMARY: Shortening or omitting the dry period improves energy balance and metabolic status, but reduces milk production and increases the risk of body fattening of cows in the subsequent lactation. Reducing the postpartum dietary energy level in order to match the lower milk yield after 0-d dry period could prevent body fattening. Earlier, reducing postpartum dietary energy level for cows after 0-d dry period reduced days open in the subsequent lactation, which may indicate improved underlying fertility. This study investigated effects of reducing dietary energy level from week 4 postpartum onwards for cows after 0-d dry period on fertility variables and associated metabolic status. Reducing the postpartum dietary energy level in cows with 0-d dry period reduced the interval from calving to onset of luteal activity in cows of parity ≥ 3, compared with a standard dietary energy level or a 30-d dry period. Fewer days open was related to fewer services per conception, fewer days to onset of luteal activity, higher percentage of ovarian cycles of normal length (18–24 d), and improved energy balance in weeks 1–7 of lactation. In conclusion, reducing a postpartum dietary energy level to match lower milk yield after 0-d dry period improved fertility in cows of parity ≥ 3, but not in cows of parity 2. ABSTRACT: This study aimed to (1) investigate effects of reducing postpartum dietary energy level for cows after a 0-d dry period (DP) on resumption of ovarian cyclicity and reproductive performance, (2) relate days open with other reproductive measures, and (3) relate onset of luteal activity (OLA) and days open with metabolic status in early lactation. Holstein-Friesian dairy cows were randomly assigned to 1 of 3 transition treatments: no DP and low postpartum dietary energy level from 22 days in milk( DIM )onwards (0-d DP (LOW)) (n = 42), no DP and standard postpartum dietary energy level (0-d DP (STD)) (n = 43), and a short DP and standard postpartum dietary energy level (30-d DP (STD)) (n = 43). Milk progesterone concentration was determined three times per week until 100 DIM. Plasma metabolite and hormone concentrations were measured weekly until week 7 postpartum. Reducing postpartum dietary energy level in older cows (parity ≥ 3) after no DP and 22 DIM did not affect milk production but prevented a positive energy balance and shortened the interval from calving to OLA. In addition, services per pregnancy and days open were reduced in cows of parity ≥ 3 on 0-d DP (LOW), compared with cows of parity ≥ 3 with 0-d DP (STD), but not in cows of parity 2.