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Protein Nutrition and Fertility in Cattle.
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2001-12-01
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Kenny, D.A., Diskin, M.G., Sreenan, J.M., Protein Nutrition and Fertility in Cattle, End of Project Reports, Teagasc, 2001.
Abstract
The objectives of the project were to determine the effects of dietary
crude protein intake, on blood concentrations of ammonia and urea and
on fertility, and on the possible biological mechanisms involved. Heifers
were used in all experiments in order to avoid any confounding effects of
lactation and, or, negative energy balance. The results are summarised as
follows.
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Blood urea and ammonia increased linearly with increases in
dietary urea. Fermentable carbohydrate, in the form of
molassed sugar beet pulp (MSBP), was more effective than
barley in reducing blood urea concentration. Plasma ammonia
concentrations were more variable but MSBP was again more
effective than barley in reducing these.
Embryo survival rate was not affected by either dietary crude
protein (CP) or fermentable energy intake irrespective of
whether animals were fed a silage diet supplemented with feed
grade urea or were grazing pasture with a high crude protein
content. Despite generating systemic urea concentrations of up
to 25 mmol/L and systemic ammonia concentrations of up to
242 μmol/L no significant relationship between these
parameters and embryo survival rate was established.
Consistent with these results on embryo survival, elevated
blood urea or ammonia had little effect on the biochemical
composition of oviduct fluid, the environment of the early
developing embryo.
It can be concluded that elevations in systemic concentrations
of ammonia or urea per se, particularly of the magnitude
observed under normal feeding conditions, are unlikely to
impair embryo survival in cattle as a consequence of
disruptions to the oviductal environment.