novatech
Well-known member
While searching for nutritional requirements that may improve conception rates I found this and thought I would pass it along.
New research has shown that high levels of protein in winter annual forages can reduce reproductive efficiency (Beck et al., 2005). Most winter annual pastures (wheat, rye, ryegrass) are very high in protein. When protein is degraded in the rumen, it is degraded into ammonia that is then transported to the liver where it is converted into urea. This will increase the blood urea nitrogen (BUN) levels. When BUN is elevated, reduced reproductive efficiency has been observed. It has been shown that the high levels of urea in the blood will reduce the pH in the uterus causing poor fetal survivability in early pregnancy. This has only been documented when cows have continuous access to lush pasture. Reductions in pregnancy rates of approximately 20 percent have been observed mostly in dairy cows with high levels of BUN. A study conducted at the University of Arkansas compared the reproductive efficiency of heifers grazed on either wheat and ryegrass pastures or fed a drylot ration of 75 percent grain and 25 percent hay (Beck et al., 2005). Heifers were grazed or fed the grain-based ration for five months prior to breeding. Daily gain of the heifers was approximately 1.22 lb/day for each group. Heifers were synchronized and artificially inseminated (AI) once and then clean-up bulls were placed with the heifers for 56 days. There were no statistically significant difference in either AI or overall pregnancy rates between the two groups. However, some trends were noticed in pregnancy rates as overall pregnancy rates for grain fed heifers was 88 percent and pregnancy rates for heifers that grazed wheat and ryegrass pastures was 69 percent. Heifers that grazed the winter annuals calved 14 days later than heifers fed the grain-based diet during development. Conceiving early in the breeding season is especially important for heifers as this will allow them more time to breed back after having their first calf.
"The reduced pregnancy rates from grazing winter annual pastures have only been observed when animals had continuous access to the pasture. Often, cows are limit grazed a few hours a day and supplemented with hay. There should be little or no problems with reproduction when using this feeding strategy. If animals are allowed to graze continuously during the early part of the breeding season then do not feed any supplemental protein. There may be some alleviation of the problem if low protein grains such as corn is fed during this time to increase the use of nitrogen in the rumen, which should lower BUN levels"
This quote was taken from http://pubs.caes.uga.edu/caespubs/pubcd/B1322/B1322.htm
New research has shown that high levels of protein in winter annual forages can reduce reproductive efficiency (Beck et al., 2005). Most winter annual pastures (wheat, rye, ryegrass) are very high in protein. When protein is degraded in the rumen, it is degraded into ammonia that is then transported to the liver where it is converted into urea. This will increase the blood urea nitrogen (BUN) levels. When BUN is elevated, reduced reproductive efficiency has been observed. It has been shown that the high levels of urea in the blood will reduce the pH in the uterus causing poor fetal survivability in early pregnancy. This has only been documented when cows have continuous access to lush pasture. Reductions in pregnancy rates of approximately 20 percent have been observed mostly in dairy cows with high levels of BUN. A study conducted at the University of Arkansas compared the reproductive efficiency of heifers grazed on either wheat and ryegrass pastures or fed a drylot ration of 75 percent grain and 25 percent hay (Beck et al., 2005). Heifers were grazed or fed the grain-based ration for five months prior to breeding. Daily gain of the heifers was approximately 1.22 lb/day for each group. Heifers were synchronized and artificially inseminated (AI) once and then clean-up bulls were placed with the heifers for 56 days. There were no statistically significant difference in either AI or overall pregnancy rates between the two groups. However, some trends were noticed in pregnancy rates as overall pregnancy rates for grain fed heifers was 88 percent and pregnancy rates for heifers that grazed wheat and ryegrass pastures was 69 percent. Heifers that grazed the winter annuals calved 14 days later than heifers fed the grain-based diet during development. Conceiving early in the breeding season is especially important for heifers as this will allow them more time to breed back after having their first calf.
"The reduced pregnancy rates from grazing winter annual pastures have only been observed when animals had continuous access to the pasture. Often, cows are limit grazed a few hours a day and supplemented with hay. There should be little or no problems with reproduction when using this feeding strategy. If animals are allowed to graze continuously during the early part of the breeding season then do not feed any supplemental protein. There may be some alleviation of the problem if low protein grains such as corn is fed during this time to increase the use of nitrogen in the rumen, which should lower BUN levels"
This quote was taken from http://pubs.caes.uga.edu/caespubs/pubcd/B1322/B1322.htm
