Shortening the DP to <60?days has been promoted during the past few years. Several experiments designed to examine the effects of reducing the DP to approximately 4?weeks have shown no difference in milk production and/or fat-corrected milk in the subsequent lactation (Annen et?al. 2004; Bachman 2002; Gulay et?al. 2003; Rastani et?al. 2005). Rastani et?al. (2005) designed a study to detect the effect of shortening or eliminating DP on energy balance, non-esterified fatty acid (NEFA) <a href="https://en.wikipedia.org/wiki/Itraconazole
">Itraconazole concentrations, DMI and reproduction. These data were evaluated both pre- and post-partum period in lactating dairy cows. In this study, cows were divided into three treatment groups. The first treatment reflected traditional (T) dry cow management practices. These cows had a 56-day DP and were fed a low-energy (LE) diet from 56 to 29?days pre-partum, followed by a moderate-energy (ME) diet from 28?days pre-partum to parturition. The second treatment group had a shortened (S) DP of 28?days; these cows were fed a HE diet throughout lactation and the DP. The third treatment group had no planned (N) DP and remained on a HE diet. The most intriguing results, including energy balance, DMI, NEFA levels and reproductive data, were observed in the N dry period group. Mean pre-partum DMI was greater in the N group than in S and T cows (Fig.?1). Cows in the N group did not go through negative EB, compared with S or T cows, during the post-partum period (Fig.?2). NEFA levels were also lower in N cows compared with S and T cows. However, although the N cows displayed the most interesting CYC202 supplier
and favourable data (greater DMI, higher EB and lower NEFA levels), it is not possible to apply this strategy in commercial dairy farms owing to lower milk production in subsequent lactation. In order to obtain reproductive data, cows�� ovaries were evaluated by ultrasound, and blood samples were collected three times per week, beginning at 6 or 7?days post-partum and continuing until 7?days after the second ovulation (Gumen et?al. 2005). The most dramatic effect observed was that the first post-partum ovulation occurred earlier in N cows than in S and T cows (Fig.?3). Verteporfin mouse
Furthermore, the average number of days from calving until the first detection of a 10-mm follicle was fewer in N (8.0?days) and S (8.9?days) than in T (10.5?days). Cows that were on the no planned dry treatment had a higher first service conception rate, fewer services per conception and fewer days open. However, these data should be evaluated carefully due to the small number of animals in each group. A recent study performed in a large commercial dairy examined the effects of shortening the dry period on reproduction in a large number of cows (Watters et?al. 2009). Cows were assigned to either 55?days dry (traditional) or 34?days dry (shortened) groups.