Complete-lactation milk and component yields following a short (35-d) or a conventional (60-d) dry period management strategy in commercial Holstein herds

Discipline: management; Key words: short dry period, conventional dry period, production, lactation number.

In the modern commercial environment we demand a lot of our cows in terms of milk yield and maximizing profits. One possible way of increasing yields and profit is to shorten the dry period, thereby prolonging the lactation periods in the lifetime of the cow. The question is, is it viable and how does such a practice affect the energy reserves of cows. Also, will the effects be different in second lactation cows compared to older cows? Dr D.E. Santschi and co-workers initiated a research program to address the issue in on-farm trials. The work was published in the Journal of Dairy Science, Volume 94 of 2011, pages 2302 to 2311, the title being: Complete-lactation milk and component yields following a short (35-d) or a conventional (60-d) dry period management strategy in commercial Holstein herds.

In the trials they used a total of 850 cows distributed among 13 commercial Holstein herds. The cows were randomly allocated to one of the two dry period management strategies and compared with respect to milk and component yields, body weight, as well as body condition score (BCS) as indicator of energy reserve status, over complete lactations. The design was that within each herd and every two months, cows were assigned to the short (35-day dry period) or the normal conventional (60-day dry period) management system, based on previous lactation 305-day milk yield, predicted calving interval, and parity: whether first lactation (numbers = 414) or multiple lactations (numbers = 436). Cows assigned to the conventional dry period treatment were fed a dry cow ration from dry-off until 21 days before calving, and were then switched to a pre-calving ration. Cows assigned to the short dry period treatment were fed the pre-calving ration throughout their dry period. Rations were different across herds, but the late-lactation, pre-calving and early lactation rations were identical for both treatment groups within herd.  

As expected, additional milk was obtained at the end of lactation from cows assigned to the short dry period treatment, due to the extended lactation. The results showed that the average daily milk yield in the following lactation was not different between the treatments for third- or greater-lactation cows, but was significantly decreased in second-lactation short dry period cows. However, when expressed as energy-corrected milk, this difference was not significant. Although lower for first lactation than for multiple lactation cows, body weight and BCS were not affected by dry period management strategy across all herds. However, milk production and BCS responses to treatments varied between cows and herds

The results from the study suggest that a short period management strategy could be more appropriate for the modern commercial dairy operation, but:

• should rather not be introduced with first lactation heifers going onto second lactation

• since the results indicate that the short dry period was not suitable for all cows or all herds, farmers should test the possibility under their own on-farm conditions.