What happens to the rumen during the dry period? It takes a rest, too, according to researchers from Wageningen University in The Netherlands.
The downside of that is it takes about a month post-freshening to ramp up rumen vitality and metabolic function again, the group discovered in a study recently published in the Journal of Dairy Science.
The purpose of the study was to determine what shortening or even eliminating the dry period had on rumen function and rumen papillae development. Papillae – the finger-like projections on the lining of the rumen wall – are important mechanisms to facilitate volatile fatty acid (VFA) absorption in the rumen. The greater the surface area created by well-developed papillae, the higher the capacity of the rumen to absorb VFAs and synthesize milk and components.
The authors noted a main factor driving the proliferation of rumen papillae is rumen fermentable organic matter intake, which is typically lowered in traditional dry-cow diets.
Twelve pregnant, rumen-cannulated Holstein cows at the end of their first lactations were selected for the study. These animals were a subset of a population of 168 cows being evaluated in a larger nutrition study. They were divided into 3 treatment groups of 4 cows each: (1) a traditional, 60-day dry period; (2) a short, 30-day dry period; and (3) no dry period.
All cows were monitored from 8 weeks before their expected calving date until 8 weeks postpartum. Consistent, forage-based rations were fed to all cows in the lactating, dry, and postpartum stages. The no-dry-period group received only the lactating and fresh-cow rations. Results included:
- Prepartum, dry-matter intake (DMI) and milk yield were greater for cows with a short or no dry period compared to cows with a conventional, 60-day dry period.
- Postpartum DMI was greater for cows with a short dry period compared to cows with a conventional dry period.
- Postpartum plasma glucose concentration was greater for cows without a dry period compared to both groups with a dry period.
- Rumen papillae surface area for cows managed with a dry period decreased as dry periods transpired. At 10 days prepartum, papillae surface area was greatest for the cows with no dry period, and this difference was still present at 3 days postpartum.
- Cows with a short dry period showed faster increase in papillae dimensions after calving compared to those with a conventional dry period.
- The 60-day-dry-period group had recovered papillae surface area to match the other two groups by 28 days in milk.
Faster rumen adaptation postpartum was believed to be related to the increased DMI during the first weeks postpartum for cows managed for a short dry period. However, this did not result in improved metabolic status or milk yield.
The authors stopped short of suggesting that cows should be managed for shorter or no dry periods, and noted that doing so could produce other undesirable consequences. “Although it was not the focus of the study, it is important to consider the effects of dry period length on milk yield postpartum and colostrum composition,” they stated. “Without a dry period, cows will produce less milk in the next lactation and will have lower concentrations of IgG and IgM in colostrum.”
However, they noted the results in terms of rumen papillae condition and dry-matter intake provide some interesting insights. They suggested additional research exploring how adjustments to dry-period length and/or prepartum ration composition could support more steady rumen status and transition into the next lactation.
