Use of Corn Co-Products in Beef Cow Diets and Its Effects on Cow and Offspring Performance

摘要

The effect of feeding corn by-products on cow reproductive performance, as well as offspring growth and reproductive performance has been investigated through four separate studies. The first study was conducted to evaluate the use of dried distiller's grains with solubles (DDGS) in beef cow diets during early lactation on both dam and heifer offspring growth and reproductive performance. Three diets, consisting of 0, 2.5 or 4.7 kg/d DM of DDGS were formulated to be isocaloric but the DDGS diets exceeded protein requirements. Milk production was not different, however, milk components increased with the addition of DDGS. Resumption of cyclicity of dams, as well as days of age at puberty in heifer offspring were not different. However, while not statistically different, time-artificial insemination (TAI) rates of both cow and heifer offspring were numerically improved with the addition of DDGS in the diet. Plasma urea nitrogen (PUN) concentrations in the cows followed the trend of being higher with increasing levels of DDGS. While PUN concentrations did reach levels that are considered detrimental to fertility, they did not seem to have a negative impact on conception.;In the second study, the use of corn gluten feed (CGF) in dam diets and its effects on their reproductive performance was investigated. Three diets, consisting of 0, 3.3 or 6.7 kg/d DM of CGF were formulated to be isocaloric but the CGF diets exceeded protein requirements. Milk production and milk components were not different with the exception of fat, which tended to be greater in the high CGF treatment. Resumption of cyclicity and TAI conception rates were not improved when CGF was added to the diet. Plasma urea nitrogen concentrations did not approached what would have been considered detrimental to fertility.;The third study was conducted to evaluate feeding DDGS during the second trimester or the second and third trimester (3.0 or 3.5 kg/d DDGS, respectively), on heifer offspring reproductive performance. Growth performance of heifer offspring did not differ among treatments. There were no differences in TAI conception rates in heifer offspring from dams fed DDGS but, dominant follicles tended to be larger in heifer offspring from dams fed DDGS during the second trimester. Due to the lack of improvement in reproductive performance in this study, it has been hypothesized that lactation may be a more critical time point for improvements in heifer offspring reproductive performance.;The fourth study followed the hypothesis of the third study. Because heifer offspring reproductive performance was positively impacted when dams were fed DDGS during early lactation, evaluation of dams fed DDGS during early lactation on bull offspring performance was investigated. Bull offspring growth performance was not impacted by dam diets during early lactation. Scrotal circumference, testosterone concentrations and semen analysis were used to evaluate days of age at puberty, however, puberty attainment in bull offspring was also not impacted. In summary, feeding DDGS as a primary source of dietary energy during early lactation had a positive impact on both cow and heifer offspring reproductive performance, but this does not seem to be true for bull offspring.