Various nutritional tools have been used to improve the productive and reproductive performance of animals, among which difference between certain minerals, called dietary cation anion difference (DCAD) plays a pivotal role. Low or negative DCAD diets reduce blood pH and HCO3- and animal becomes acidotic. This improves Ca absorption from the intestinal tract. It also induces mobilization of Ca from bones which improves Ca status of the animal, thus preventing the occurrence of milk fever at the time of parturition. This may increase milk production and health in subsequent lactation. However, animals fed high DCAD diets before parturition may suffer from milk fever. Milk fever affected animals have increased plasma cortisol level that causes immunosuppression at calving. It is also positively associated with other problems like retained placenta, mastitis and udder edema. On the other hand, feeding high DCAD diet results in increased ruminal pH which is pre-requisite for optimal microbial activity as well as improving the feed intake of the animal. Improved dry matter intake (DMI) is positively correlated with milk yield by providing precursors for various milk constituents. High DCAD diet results in increased milk fat percent due to shifting of ruminal volatile fatty acid production towards acetic acid and butyric acid. It also improves energy balance of the animal which causes increased blood flow towards ovaries and increased progesterone synthesis and follicular development due to positive association between energy balance and postpartum ovulation, which leads to improved reproductive performance of the animal. While feeding low DCAD diet reduces feed intake which causes negative energy balance in early lactating animals that lessens conception rate and increases services per conception. In conclusion, feeding low DCAD diets prepartum prevents the occurrence of milk fever via improving Ca status while feeding high DCAD diets results in improved productive and reproductive performance in lactating animals.
Key words: Feed intake, milk yield, reproductive performance, hypocalcaemia, dietary cation anion difference.
Abbreviations: DCAD, Dietary cation anion difference; VFA, volatile fatty acids, NDF,neutral detergent fiber; ADF, acid detergent fiber; OM, organic matter; CP, crude protein; IGF-I, insuline like growth factor; DMI, dry matter intake; PTH, parathyroid hormone.
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