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1006 PD: Effect of dry propylene glycol versus drenching

Published on 02 October 2006

Negative energy balance (NEB) is a physiological challenge the Holstein dairy cow faces in the early postpartum period when dietary energy intake cannot meet with energy output in milk. Infectious diseases commonly seen are retained placenta, metritis and mastitis, which are consequences of depressed immunity and NEB. Metabolic disorders may include ketosis, displaced abomasum and fatty liver.

Ketosis is the most commonly seen metabolic disorder that occurs in the first month of lactation. Ketosis is characterized as an excessive accumulation of ketone bodies in the body fluids of blood, urine and milk. Clinical signs of ketosis include rapid loss of bodyweight, lack of appetite, rapid decrease in milk production, abnormal rumen contractions and nervous disturbances.

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Subclinical ketosis is characterized by excess ketone bodies in the circulation without the presence of the clinical signs of ketosis. Economical losses from ketosis are considered to be high because of milk and bodyweight losses, treatment cost and culling of cows that have had repeated occurrences of ketosis.

Drenching of propylene glycol (PG) is effective in treating ketosis for postpartum cows. Because feeding of PG requires less labor and reduces stress, the effectiveness of feeding PG as a feed additive to replace liquid drenching has been of interest for the purpose of reducing subclinical ketosis.

We recently fed early lactation cows 250 grams (.55 pounds) per cow per day of dry propylene glycol (PG; 65 percent of 1,2-propanediol) either as a top-dress or as a part of the total mixed ration (TMR) to dairy cows for the first three weeks of lactation and observed a reduction in blood-hydroxybutyrate (BHBA) and urine ketones and a subsequent reduction in the incidence rate of subclinical ketosis from 39 to 13 percent by feeding dry PG.

Between different methods of delivery of dry PG, feeding dry PG as part of the TMR resulted in a better overall energy balance (EB) compared to feeding dry PG as a top-dress. However, feeding dry PG as a top-dress resulted in a greater rate of increase in milk production than feeding dry PG as part of the TMR.

Based on these results, we thought the metabolic adaptation of cows to different methods of delivery of dry PG is probably different. We hypothesized dry PG provided as a top-dress will be as effective as PG provided as a liquid drench in alleviating ketosis. We also hypothesized how dairy cows respond to a slow-release energy source differs from a pulse-dose energy source such that the cow uses a slow-release of energy more efficiently than a pulse-dose of energy.

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The objective of this study is to characterize the metabolic adaptation of cows in response to PG under different methods of delivery. By providing the same amount of pure PG, different methods of delivery of PG will be assessed by:

1. control – no PG
2. oral drench – 200 milliliters (8 ounces per cow per day) of liquid PG (100 percent of 1,2-propanediol) oral drench
3. pulse-dose – 308 grams (.68 pounds) per cow per day of dry PG (65 percent of 1,2-propanediol ) provided directly into the rumen
4. slow-release – 308 (.68 pounds) grams per cow per day of dry PG fed as a part of the TMR

By a direct comparison between oral drench of liquid PG and feeding of dry PG as either a top-dress or a part of TMR, we will show feeding dry PG as a top-dress is as effective as oral drench of liquid PG. Replacing routine drenching with feeding will therefore reduce stress on cows that receive the drench and also reduce cost of labor, ultimately improving overall health and production of dairy cows. If ketosis is reduced by at least 25 percent in the herd, this more than pays for incorporating dry PG into the TMR. PD

—From Penn State Dairy Digest, July 2006

R. Chung, Graduate Research Assistant, and G. A. Varga, Professor of Animal Science, Penn State

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