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Ivan Rush: High protein ration effect on reproduction

Thankfully the weather has cooperated these past few weeks in the region and calving cows are facing less challenges from cold stress. It is great to see the newborns and the start of another successful calf crop.

A couple of people have called wanting to know why cows occasionally retain placentas. I often tell people that I can talk for 30 minutes on retained placentas and probably not give them a specific answer to their problem. We do know that cows that abort or calve 2-3 weeks early have a high probability of retaining placentas. We are sure that cows that are deficient in vitamin A will tend to retain placentas, usually accompanied with light, thin and weak calves. Others suspect low levels of vitamin E and/or selenium, or low levels of phosphorus, but this has not been well documented.

I personally feel that the primary cause behind cows retaining placentas is that their energy intake crashes during calving. I am convinced that I see more problems in thin cows that continue to lose considerable weight during calving, but again I have not seen this researched and documented. The bottom line is, in many cases, retained placentas happen and we don’t have the answer why.



Your veterinarian can advise you on how to treat cows, which will often include the use of prostaglandin and maybe oxytocin and antibiotics. The one thing that all veterinarians and beef specialists agree on is to not try to mechanically remove the placenta. You will often do more damage than good and can actually tear the uterus, which will delay or prevent rebreeding, or in some cases kill the cow. Data shows than any cow with a retained placenta for a period of time will be delayed in breeding.

I enjoy reading state beef reports from the region and found an excellent article in the Oklahoma State University Beef Report that questions if high protein diets have a negative effect on reproduction. We often hear that if cows or heifers are on high-protein feeds, such as lush green pastures, reproduction will be lowered. The theory is that the excess nitrogen in the rumen enters the blood stream causing very high levels of blood urea nitrogen (BUN), which negatively effects the uterine environment by lowering the pH and causing problems in fertilization or implantation of the fertilized egg. Basic data with dairy cattle in Wisconsin showed this effect and was published in the early 1990s.



I have always had a hard time accepting that this data could be used for conditions in this region because of the large number of cattle that are bred very successfully each year that graze wheat pasture in the southern states and irrigated grass or crested wheatgrass pasture in much of our region. In addition, producers continue to see that even a short time on lush, spring green grass, will assure a high early conception rate.

Finally a two-year study was conducted at Oklahoma State University where a group of heifers grazed wheat pasture that contained 26 percent crude protein (almost as high as 30 percent protein cake) were compared to a group that were maintained and bred in a dry lot on a diet that was 11 percent protein. The heifers were synchronized so all of the breeding was done at the same time with the same technicians.

The bottom line showed that the reproductive economical traits slightly favored the heifers that were bred on wheat pasture. First service conception was 53 percent versus 43 percent for the wheat pasture and dry lot, respectively. Overall conception was not significantly different, with 95 percent versus 88 percent for wheat pasture and dry lot heifers, respectively. Blood samples were taken for all heifers for five days just before and during breeding, and the heifers on wheat pasture had very high BUN levels (22-25 mg/dL); significantly higher than dry lot heifers, which was 5-7 mg/dL.

Previous data indicated that if BUN was greater than 16-18 mg/dL, it was considered high and detrimental to reproduction. The authors measured other blood perimeters, including IGF-I, and could not explain the lack of negative effect of the high protein wheat pasture. It wasn’t an energy effect because the heifers in dry lot had slightly higher gain than heifers on wheat pasture. The authors did point out data in Australia that showed some negative effects with high protein diets were offered that pushed BUN levels over the 16 mg/dL threshold.

As a result of the Oklahoma State two-year study, I have no reservations in recommending turning cows or heifers out on lush, high protein and high energy pastures, without fear of lowering fertility.

Our hearts and prayers must go out to those in Japan. I thought I had some problems, but when I turned the TV on and saw the start of the devastation, I found I had no problems compared to what these poor people were experiencing.


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