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February 2013 Archive for Animal Health & Nutrition

RSS By: Rick Lundquist, Dairy Today

Rick Lundquist is an independent nutrition and management consultant based in Duluth, Minn. He provides livestock production advice.

Fat Cows Have Weaker Immune Systems at Calving

Feb 24, 2013

Stress, the release of cortisol and negative energy balance are other suspected culprits for problems during this critical lactation time.

Cows are more susceptible to infectious diseases and metabolic disorders around the time of calving because the immune system is at its weakest during this time. Mastitis, metritis and other infections respond to treatment much less at calving than at any other point in the cow’s lactation.

We don’t know the whole story about why cows have poorly functioning immune systems around the time of calving, but there are several theories, according to Matt Waldron at the University of Missouri. We know that stress and the release of cortisol at calving suppress the immune system.

Negative energy balance caused by the high demands for milk production and lower prepartum dry matter intake seems like an obvious culprit. Mastectomized cows have been shown to have better immune function than cows with intact mammary glands immediately following calving, indicating that the metabolic demands of the mammary gland stress the immune system. But experimentally induced feed restrictions during lactation have not resulted in the same immunosuppression as at parturition, so negative energy balance by itself doesn’t seem to be the cause.

Over-conditioned cows have a greater risk for inflammation and infection after calving, and the cause-and-effect puzzle is slowly being assembled, according to Waldron. Fat cows are more likely to have higher levels of circulating nonesterified fatty acids (NEFA) and ketones and also accumulate more fat in the liver. Elevated NEFA, ketones and liver triglycerides have all been associated with impaired immune function. Fat cows also tend to have higher levels of unstable oxidizing molecules that react with tissue fat, protein and DNA and contribute to inflammation.

Calcium is involved with proper immune system function. Cows with subclinical or clinical milk fever are more susceptible to mastitis.

So, how do we help immune function during this critical time in a cow’s lactation? Minimizing stress by providing a clean, comfortable environment for transition cows is number one. Avoid calving over-conditioned cows. The high price of cull cows lately should help this situation. Prepartum diets designed to minimize subclinical milk fever may also reduce the risk of mastitis and metritis. Providing adequate bioavailable antioxidant nutrients such as vitamin E, A, and zinc and selenium can help reduce inflammation and duration of infections, according to Waldron.

The 1%ers of Reproductive Performance

Feb 04, 2013

How do the top herds in reproductive performance get to be the 1%ers?

How do the top 1% of herds in reproductive performance get to be the 1%ers? What do they do that sets them apart? A survey conducted by researchers at the University of Pennsylvania compiled data from 16 herds that were nominated by their consultants based on excellence in reproductive performance. These producers ranged from 262 to over 6,000 lactating and dry cows.

Cow fertility has a biological component (the cow) and a management component. Fertility has decreased with increasing milk production over the years. Days open has increased from 110 days in 1965 to 150 days in 2005. There’s no question that fertility is influenced by high production. So, reproductive management has become ever more important and according to this survey, it’s what sets the 1%ers apart.

Pregnancy rate (PR) averaged 32% in the 1%ers compared to about 16% for all herds in the Raleigh Dairy Records Management System (DRMS). This put these herds in the top 1% for PR. These herds averaged 71 days to first service compared to 92 days for all herds in DRMS. Surprisingly, the 1%ers had only average conception rates compared to all herds in DRMS (44 % first service conception rate and 39% across all services vs. 43% for all DRMS herds).

Excellent heat detection and insemination rates resulted in the superior reproductive performance in the 1%ers. High insemination rates in these herds were due to controlled first insemination programs as well as consistent repeat insemination programs. They employed weekly or biweekly pregnancy checks combined with a resynchronization program. The 1%ers used a combination of timed AI and heat detection by visual and heat detection aids (paint, markers and activity monitors). In a nutshell, the 1%ers were aggressive and applied their reproductive programs consistently.

The herds in this survey were in the Midwest, Northeast and on the West Coast. There were no herds from the Southern states, where heat and humidity challenge reproductive performance. But the same intense reproductive management still applies if herds in the South want to improve reproductive performance.

Since this is primarily a nutrition column, I should mention that nutrition was not considered as a variable in this survey. I would assume that nutrition programs were also well managed in these 1%ers. No magic pill or nutritional supplement can substitute for hard work and superior management of a reproductive program.

Reference: Ferguson, J.D. and A. Skidmore. 2013. Reproductive performance in a select sample of dairy herds. J.Dairy Sci. 96:1269-1289.

Rick Lundquist is an independent nutrition and management consultant based in Duluth, Minn. Contact him at siestadog@aol.com.
 

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