Dairy Channel: A researcher’s view on shorter lactation

Since several studies on shortened dry periods were presented at the American Dairy Science Association’s annual meeting last summer, it seems like you can’t open up a dairy magazine without seeing something written about the subject.

We were one talk into the 2004 Tri-State Dairy Nutrition Conference in Ft. Wayne, Ind., this week when the topic surfaced again.

Shorter or longer. Traditionally, we have managed for 60-day dry periods. It isn’t unusual to find shorter dry periods in older cows on many farms.

Recent research looks at dry periods anywhere from zero to 56 days in length.

(Remember that rare zero day to one-week dry period on your farm that you just considered a major goof instead of being ahead of your time management?)

Actually, while there may prove to be advantages of shorter dry periods, evidence points to 20 to 25 percent less milk yield if no dry period was provided.

Ups and downs. After reviewing a number of published studies examining various iterations of shorter dry periods, Ric Grummer, dairy researcher at the University of Wisconsin, feels it is reasonable to expect a 5 percent drop in milk yield in the lactation following a 30-day dry period.

Two of the three studies measured protein percentage with two of them reporting a significant increase for the lactations following a 30-day dry period.

There was only one experiment that demonstrated a significant increase in milk fat percent.

Only part of the answer. While these studies are beginning to answer questions about production in the lactation immediately following the shortened dry period, they only tracked the cows part way through the lactation.

Why? Because it costs a lot of money to conduct a good study on a statistically significant number of cows through one lactation, let alone 2 or 3 consecutive lactations.

Many questions surface about shorter lactations.

His thoughts. Q: How short is too short?

Grummer: “We are recommending a 40-day dry period to accommodate cows that have shorter than normal gestation lengths (e.g. cows with twins) and dry cow treatments.”

Q: Will there be antibiotic residues from shorter dry periods?

Grummer: “There may be … producers should send milk samples from individual cows to the milk plant for testing when first implementing a shorter dry period.”

Herd health. Q: Will there be more mastitis?

Grummer: “We need more data here. Some information suggests that there are fewer new infections during shorter dry periods.”

Q: What should be fed to these shorter dry period cows?

Grummer: “We need more data here. There are some suggestions.”

(This would be another whole column. Contact me if you would like a copy of the article.)

Calf nutrition. Q: Will extending the lactation cause a diversion of nutrients away from the fetus?

Grummer: “No. Cows should be in positive energy balance and our data suggest that there is no difference in calf weights when the dry period is shortened to 28 or 0 days (in Grummer’s experiment.)”

Q: Will cows “burn out” if the dry period is shortened to 30 days?

Grummer: “There is no research data for cows given a 30 day dry period for two consecutive gestation/lactation cycles.

“Nevertheless, it is unlikely that they would “burn out”. Our data reveal that cows are more likely to be in positive energy balance during the extended lactation period.

Colostrum. Q: Is there a problem with colostrum quality?

Grummer: “Only if cows are not allowed a dry period. Without a dry period, cows will produce more colostrum, but it will have lower immunoglobulin concentrations.”

Q: Are some cows better suited for shorter dry periods than others?

Grummer: “Some data suggests that cows in their second pregnancy may be less likely to successfully negotiate a shortened dry period.

“Cows with a longer calving interval may be more likely to tolerate a shortened dry period. There are many more questions than answers about shorter dry periods.

“We really need multiple lactation studies to evaluate the long term impacts.

“How will lifetime production, reproduction and health of cows given shorter dry periods, (who will milk more days but give less milk per day,) compare to cows given longer dry periods.

“Only study of multiple lactations in a controlled setting will give us the real answer.”

(The author is the northeast Ohio district dairy specialist with OSU Extension. Send comments or questions in care of Farm and Dairy, P.O. Box 38, Salem, OH 44460.)

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