Amazing progress has been made in the nutrition and management of dairy cattle during the last 20 years.

The average milk production for Holstein cows is now greater than 20,000 pounds. We now take an integrated approach to managing our cows. No longer are nutrition and feeding managed separately from cow comfort, climate modification and grouping strategies. A good feeding program can appear to be exceptional because of superior cow comfort or environmental management.

We should be proud of the advances made in the last 30 years in dairy cattle feeding and management. Yet, one area is lagging behind the others in progress, and that area is reproduction. As a young student studying Animal Science, I was taught that the ideal calving interval was 13 months. Calving interval has not improved in the last 20 years. Calving interval has increased from 13 months to 15 months. This increase in calving interval suggests that either fertility is declining in the dairy population or we have a breakdown between nutrition and reproduction.

It is easy to blame the increase in milk yield per cow for the decline in fertility of the dairy cow. As daily milk production is increased from 70 pounds to 100 pounds, the heat detection rate declines from 80 to 90 percent at the lower milk production to 40 to 50 percent at 100 pounds of milk. This would suggest that as milk production increases it becomes more difficult to detect cows in heat.

The common view is that as the dairy cow produces more milk in early lactation, she experiences a greater negative energy balance and this leads to poor conception rates. Yet, when the relationship between high milk yield in the first 60 days in milk and reproduction was examined, the effect of high milk yield on reproduction was neutral and not significant. The impact of metabolic diseases such as retained placenta and metritis was much greater on reproduction than milk yield. If a cow has a retained placenta or metritris, she is 14 to 15 percent less likely to conceive than a healthy cow.

The take-home message from this research was that cows that remain healthy during the transition period get bred and have good conception rates. Cows that do not transition well and do not remain healthy during the transition period have poor conception rates. Pregnancy rate is decreased in cows that have fatty liver, and days open is significantly increased in these cows.

Prescription for a successful transition program
Reproduction can be improved by focusing on the transition period and putting together a successful transition program. A successful transition program has the following characteristics:

1. Optimize dry matter intake during the dry period without the excessive consumption of energy.

2. Optimize dry matter intake during the first three to four weeks of lactation.

3. Prevent the development of fatty liver in the transition cow.

4. Provide those nutrients in the diet that support and enhance good liver function. Some of these nutrients are choline, trace minerals and methionine.

5. Prevent excessive loss of body condition in the first 21 days after calving. This will require the integration of nutrition with cow comfort, environmental modification and proper cow movement and grouping strategies.

A successful transition program will improve conception rate by maintaining low-blood non-esterified fatty acids (NEFA) concentrations in the first 14 days after calving. Cows with elevated blood NEFA concentrations in the first 14 days after calving did not get pregnant by 100 days in milk. When NEFA concentration was low during the first 14 days in milk, cows got pregnant by 100 days in milk (DIM).

Elevated blood NEFA concentration on day 3 after calving is directly related to the probability of getting a cow pregnant on the first service. A cow with elevated blood NEFA on day 3 after calving has only a 33 percent chance of getting pregnant on the first service. A cow that remains healthy during the transition period can have a first service conception rate of greater than 50 percent.

Poor conception rate leads to increased days open and this can be expensive. A 14 month calving interval equates to 150 days open. If you have a 14 month calving interval, it is costing you $177 per cow. Now is the time to get motivated about having a successful transition program and improving reproduction.

One goal for a successful transition program is to have dry matter intake of 12.5 kilograms (kg) or 27.5 pounds. Dry cows can eat 2 percent of their body weight daily during the dry period. So a 1,450 pound dry cow should consume 29 pounds of dry matter. A first lactation cow weighing 1,350 pounds should consume 27 pounds of dry matter.

Dry matter intake less than 27.5 pounds during the dry period will usually lead to poor dry matter intake after calving. Poor dry matter intake after calving leads to poor milk production. Your goals for dry matter intake should be 27.5 pounds in the dry period and 41 pounds in the first 21 days after calving.

The link between nutrition and reproduction
One phrase can explain the link between nutrition and reproduction, and that phrase is keep cows healthy. Healthy cows are cows with normal liver function, good appetite and less than 5 percent fat in the liver during the transition period. These healthy cows can have first service conception rates of greater than 50 percent even though the average first service conception rate is 30 percent in the typical dairy herd.

Approximately 50 percent of our transition cows develop moderate to severe fatty liver. In these cows, liver function is compromised and you observe elevated concentrations of ketones in the blood or urine and a depression in reproduction. Numerous research studies have been published which report a negative effect of fatty liver on many of the important reproductive parameters. If you want to improve reproduction, then you need to feed and manage cows to prevent the development of moderate to severe fatty liver and maintain normal liver function during the transition period.

Cows that consume excess energy in the dry period will be likely to develop metabolic diseases. Healthy cows will have lower NEFA concentrations in the first seven days after calving and get pregnant sooner after calving. Reasons to manage and feed cows to prevent fatty liver are listed below:

• Healthy cows eat more during the transition period.

• Healthy cows do not have metabolic diseases.

• Healthy cows have higher first service conception rate.

• Healthy cows mobilize less body fat because they have greater DMI and make more glucose in the liver.

• Healthy cows have lower NEFA concentrations in the first seven days after calving.

• Ration guidelines enhance liver function and promote good dry matter intake in the transition period.

The key to successful transition cow feeding is not to overfeed energy and get cows to consume a diet containing plenty of digestible fiber. A successful transition program meets dry matter intake goals without causing cows to get fat. You want to feed a low starch diet and keep the energy in the diet low by limiting the amount of corn silage and using chopped wheat straw and beet pulp if it is available. Nutrients such as rumen protected choline; chelated minerals, selenium and vitamin E have all been shown to be beneficial in the transition cow diet.

Additives such as rumensin, yeast culture and anionic salts should also be considered when formulating the close-up cow diet. Anionic salts and rumensin should not be used in the far-off dry cow diet.

The key points in designing a successful transition cow program are listed below:

• Do not feed excessive amounts of energy in the dry period.

• Feed dry period diets that have plenty of digestible fiber.

• Healthy cows during the transition period get pregnant sooner and have greater first service conception rate.

• Preventing fatty liver in the transition period will improve reproduction.

• Minimizing excessive fat mobilization during the transition period will improve reproduction by reducing NEFA.

• Use nutrients that enhance liver health and immunity.

By following these guidelines, you will improve transition cow health, improve reproductive performance and have less metabolic disease in your herd. If you adopt this approach to feeding dry cows, you must begin with the far-off dry cow. Cows that consumed excess energy in the dry period had lower dry matter intake postpartum, accumulated a greater amount of fat in their liver and mobilized a greater amount of body fat after calving.

Cows fed lower energy diets in the dry period had greater dry matter intake in the first four days after calving and were in less negative energy balance compared to cows fed higher energy diets in the dry period. How we feed dry cows will effect reproduction because over feeding of energy in the dry period will lead to fatty liver and greater mobilization of body fat after calving. PD

References omitted but are available upon request at editor@progressivedairy.com

—Excerpts from 3rd Annual I-29 Dairy Conference Proceedings

Stephen M. Emanuele
Ph.D. PAS
Animal Nutrition and Health Group
Balchem Corporation