Reduced Dry Periods and Varying Prepartum Diets Alter Postpartum Ovulation and Reproductive Measures

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.

Management of Dry and Transition Cows to Improve Energy Balance and Reproduction

“…1) [24] and potential for enhancing reproductive performance is increased. Some of the same benefits may be obtained by shortening the dry period, however, they will likely be of a smaller magnitude than obtained when eliminating the dry period completely [6].…”

“…For our first study [6,24], cows were assigned to treatments at -56 d prepartum. The 3 treatments were 1) 56 d dry: cows fed a lowenergy far off diet from -56 to -29 d prepartum and a moderateenergy transition diet from -28 d to parturition; 2) 28 d dry: cows fed lactation diet throughout the dry period; and 3) 0 d dry: cows fed lactation diet until calving.…”

“…A common observation is an increase in time to resumption of ovarian cyclicity as negative EB increases [1,6]. Early resumption of ovarian cyclicity is important because fertility at first breeding may increase as the number of estrous cycles prior to breeding increases [7].…”

Dietary energy density in the dry period on the metabolic status of lactating cows

“…However due to the limited number of animals per treatment, it is difficult to come to a definitive conclusion about the benefits of the M diet in the dry period to fertility variables. Gümen et al (2005) reported improved reproductive measures (time of the first ovulation, first-service conception rate, days open) in groups fed continuously with a high-energy diet and no planned dry period, compared to the traditional two-phase dry period. Colazo et al (2009) in spite of increasing the postpartum dry matter intake and a reduction of negative energy balance, demonstrated that restricted nutrition in the last 4 weeks of gestation negatively affected pregnancy at first insemination.…”

Nutritional sub-fertility in the dairy cow: towards improved reproductive management through a better biological understanding

“…Although delayed first ovulation is clearly related to body condition score at calving and energy balance of early lactation, it is not as clearly related to milk production. Depending on the experiment but not on herd yield, greater Review: nutritional sub-fertility in the dairy cow milk yield increased the delay to first ovulation and/or to the day of commencement of luteal activity (C-LA) (Petersson et al, 2006), decreased it (Fonseca et al, 1983;Garbarino et al, 2004) or had no effect (Staples et al, 1990;Darwash et al, 1997;Gumen et al, 2005;Lopez et al, 2005;Pedernera et al, 2008). The effect of milk yield may also be approached by breed differences.…”