While nitrates (N03) are not very toxic, nitrites (N02) are toxic. In ruminant animals such as cattle, sheep and goats, nitrate is converted to nitrite by bacteria in the rumen. This nitrite is then changed to ammonia. Excess ammonia is absorbed by the blood and passed in the urine as urea. This occurs when the nitrate breakdown system is in balance and no surplus of nitrites accumulate.
Microbial fermentation in the rumen dominates the nutrition of ruminant animals. Microbial ecosystems lend themselves to manipulation by external means, and it has long been clear that feed additives could be used to improve the nutrition of ruminants by manipulating ruminal fermentation. Ionophores and antibiotics have been used in the past to achieve some nutritional goals, however the recent ban of antimicrobial feed additives in the EU has lead to renewed interest in plants or their extracts as feed additives, with some success. This paper reviews recent progress in understanding how plants and their extracts may be used as rumen manipulating agents, with some benefits that were provided by ionophores and others that may improve the health of the animal and the healthiness of ruminant products.
Water is the most essential of all nutrients required by animals. Water functions in the digestion and metabolism of nutrients, elimination of waste products from the body via urine, feces and respiration, transport of nutrients and other compounds into and out of cells, electrolyte balance in the body and as a fluid environment for the developing fetus. A lactating dairy cow has one of the largest requirements for water of any animal. This is because 56 to 81% of her body weight is water and she needs to replace the major loss of water through milk production, milk is 87% water, each day (Murphy, 1992). Therefore, it is essential dairy cattle consume adequate quantities of water each day to meet their requirements.
Accurate understanding of the chemical composition of feedstuffs is the key in properly identifying cost effective feed ingredients and in delivering a ration that maximizes milk production. Assembling this knowledge not only requires understanding of the feeds typically grown on the farm, but also usually involves understanding of other complementary industries that may be supplying feedstuffs to the dairy industry.
Introduction
Previous studies (Busquet et al., 2005; Calsamiglia et al., 2007) have shown that garlic oil (GO) supplementation to in vitro cultures of ruminal micro-organisms leads to reduced methane production and acetate:propionate ratios, but the effects are related to the dose. Our hypothesis was that GO effects might depend on the rumen microbial populations, and thus on both the incubated substrate and the type of diet fed to donor animals.
