Sixty-five Holstein cows were used to evaluate management schemes involving altered dry period (DP) lengths on subsequent milk production, energy balance (EB), and metabolic variables. Cows were assigned to one of 3 treatments: traditional 56-d DP (fed a low-energy diet from -56 to -29 d and a moderate energy diet from -28 d to parturition; T), 28-d DP (continuously fed a high energy diet; S), and no planned DP (continuously fed a high energy diet; N). Prepartum DM intake (DMI), measured from 56 d prepartum through parturition, was lower for cows on the T treatment than for cows on the S treatment and was higher for cows on the N treatment than for cows on the S treatment. There were no differences in prepartum plasma glucose, and beta-hydroxybutryric acid; there was a treatment by time interaction for prepartum plasma nonesterified fatty acid (NEFA). There was no difference in prepartum liver triglyceride (TG); postpartum liver TG was decreased for cows on the N treatment compared with cows on the S treatment, but was similar for cows on the T and S treatments. Postpartum NEFA was similar between cows on the T and S treatments, but was greater for cows on the S treatment than for cows on the N treatment. Postpartum glucose was greater for cows on the N treatment compared with cows on the S treatment and tended to be greater for cows on the S treatment than for cows on the T treatment. There was no difference in postpartum solids-corrected milk (SCM) production or DMI by cows on the T vs. S treatment. However, there was a tendency toward lower postpartum SCM production by cows on the N vs. S treatment and a tendency for greater postpartum DMI by cows on the N vs. S treatment. Postpartum EB was greater for cows on the S vs. T treatment and the N vs. S treatment. In general, T and S management schemes had similar effects on DMI, SCM, and metabolic variables in the first 70 d of the subsequent lactation. Eliminating the DP improved energy and metabolic status.

No abstract

There has been substantial recent interest in shortening dry periods; however, the effects of this management change on reproduction have not been adequately evaluated. Holstein cows (n = 58) were assigned in a randomized block design to 1 of 3 treatments: 1) traditional (T) dry period (approximately 56 d) in which cows were fed a low energy diet from 56 to 29 d prepartum followed by a moderate energy diet for 28 d; 2) shortened (S) dry period (approximately 28 d) in which cows were fed continuously a high energy diet; or 3) no planned (N) dry period in which cows were fed continuously a high energy diet. All cows received a high energy lactation diet after calving. Ovaries were evaluated by ultrasound and blood samples collected 3 times weekly beginning at d 6 or 7 postpartum until 7 d after second ovulation. Average days from calving until first detection of a 10-mm follicle were fewer in N (8.0 d) and S (8.9 d) than in T (10.5 d) cows. Time from calving to first ovulation was earlier in N (13.2 d) than in S (23.8 d) and T (31.9 d) cows. A greater percentage of follicles of the first follicular wave ovulated in N (89%; 16/18) than in T (42%; 8/19), with S (62%; 13/21) cows being intermediate. Double ovulation rate at the first ovulation was greater in T (61%) than N (16%), with S (35%) intermediate. No difference was detected in double ovulation rate at second ovulation (13/56). Number of cows with persistent corpus luteum (>30 d; 15/56) was not different among groups; however, short luteal phases were greater in N (28%; 5/18) than S (0%; 0/20) cows. Days to first artificial insemination were fewer in N (69.4 d) and S (68.0 d) than in T (75.0 d). First-service conception rate was greater in N (55%; 11/20) than in T (20%; 4/20), with S (26%; 6/23) cows being intermediate. Days open in pregnant cows were fewer in N (93.8 d) than in T (145.4 d), with S (121.2 d) cows being intermediate. Thus, shortening or eliminating the dry period leads to earlier postpartum ovulation and the results highlight the need for future large field studies to accurately evaluate the effect of dry period length on reproductive performance of lactating dairy cows.

Possible advantages of reducing length of dry period include increased income from milk production, simplified dry cow management, decreased metabolic disorders, and alleviation of overcrowded dry cow facilities.

Days dry may influence reproductive measures such as days to first postpartum ovulation, days open, and pregnancy per artificial insemination (AI). Holstein cows (n = 781) from an approximately 3,000-cow commercial dairy operation were randomly assigned to 1 of 2 treatments with different targeted dry period (DP) lengths. Treatments were 1) a traditional DP of 55 d (T) or 2) a shortened DP of 34 d (S). All dry cows on T were fed a low-energy diet until 35 d before expected calving, and then at 34 d before expected calving, cows on T and S were fed a moderate energy diet until parturition. After parturition, all cows consumed the same diets that included a postcalving diet followed by a lactation diet. Actual days dry for each treatment were close to expected values, 34 and 56 d for S and T, respectively. Median days until first postpartum ovulation occurred sooner for S compared with T (35 vs. 43 d). The percentage of cows that were classified anovular by 70 d in milk (DIM) was more than 2-fold greater for cows on T than S (18 vs. 8%). Cows received AI after standing estrus starting at d 45, and the percentage of cows pregnant at 70 DIM tended to be greater for S than T; younger cows were similar (20.2 vs. 18.8%), but there was a difference between S and T in older cows (20.3 vs. 10.6%). Similarly, median days open tended to be fewer for cows on S than T. At 300 DIM, 85% of cows in both treatments were pregnant. Combining data from first and second service, pregnancies per AI were greater in older cows on S than T (32 vs. 24%). Thus, shortening the DP appeared to increase reproductive efficiency in older cows by shortening time to first ovulation, reducing numbers of anovular cows, and improving fertility. Future studies at more locations with varying reproductive management strategies are needed to confirm and provide the mechanistic basis for these results.