Effect of dry period management on mammary gland function and its endocrine regulation in dairy cows

Abstract

The objective of this study was to evaluate the effect of shortening the dry period on the mammary gland and the hormonal regulation of its functions. Holstein cows (n = 18) were assigned to a short dry period (SDP; 35 d; n = 9) or a conventional dry period (CDP; 65 d; n = 9). All cows were fed the same diets, with the exception that, during the dry period, the SDP cows received only the pre-calving diet for 35 d, whereas the CDP cows were fed a high-fiber diet from 65 to 28 d before calving and then received the same pre-calving diet as the SDP cows. Mammary gland functional capacity was evaluated at 70 days in milk, and mammary biopsies were taken in early and midlactation. Dry period length averaged 64.3 ± 1.1 and 31.9 ± 1.0 d for the CDP and SDP cows, respectively. The SDP cows had a lower milk yield and a lower energy-corrected milk yield compared with the CDP cows. The SDP cows also had a lower dry matter intake from wk 5 to 20 of lactation and tended to have lower plasma concentrations of β-hydroxybutyrate from wk 1 to 4. Prepartum serum progesterone and estradiol concentrations were unaffected by the dry period management. Serum growth hormone concentrations and milking-induced prolactin release were similar in both groups. However, during the period when the CDP cows were dry but the SDP cows were still being milked (wk -9 to -6), serum prolactin concentrations were higher in the SDP cows than in the CDP cows. The SDP cows had a lower milk BSA content than the CDP cows after the dry period and similar milk lactose concentrations, suggesting that their mammary tight junctions were closed following parturition and, therefore, that the later stage of their lactogenesis was not impaired by SDP management. In early and midlactation, mammary cell apoptosis and proliferation rates as well as mammary expression of genes involved in the function of this tissue were unaffected by the dry period management strategy. For cows in their second lactation, mammary gland functional capacity at 70 d in milk tended to be lower in the SDP cows. In conclusion, even though SDP management decreased milk production during the subsequent lactation, it did not affect mammary cell activity. Although direct evidence is still lacking, decreased mammary cell growth during the dry period is likely responsible for this negative effect. The higher prolactin concentrations in lactating cows during late gestation could be involved in this effect. More research is needed to test these hypotheses.

The effect of milking reinitiation following extended nonmilking periods on lactation in primiparous dairy cows

“…In support, in the present study PRL increased during the reestablishment of lactation for all 3 nonmilked groups. It has been reported that PRL concentrations were lower during the dry period compared with cows that were still being milked (Bernier-Dodier et al, 2011). In contrast, in the present study, during the nonmilked periods, the PRL levels remained similar to pretrial lactating values for the 7-d-nonmilked group, although the 14-and 28-dnonmilked groups had a small increase.…”

Milk production during the colostral period is not related to the later lactational performance in dairy cows

“…According to previous studies, factors such as the length of the dry period or continuous milking affect the milk yield of the subsequent lactation (Annen et al, 2007;Bernier-Dodier et al, 2011). However, to our knowledge, the effect of colostrum yield on subsequent milk production has not been previously reported.…”

The dopamine antagonist domperidone increases prolactin concentration and enhances milk production in dairy cows

“…Serum and milk PRL concentrations were measured by RIA as described by Bernier-Dodier et al (2011). Bovine PRL, rabbit antiserum specific for bovine PRL, and goat anti-rabbit gamma globulin were purchased from the National Hormone and Peptide Program (Harbor-UCLA Medical Center, Torrance, CA).…”