Research On The Safety Of The Application Of Ammonium Chloride In Lactating Dairy Cows

The objective of the present study was to determine NH4 Cl tolerance in lactating dairy cows to provide a theoretical basis for use of NH4 Cl both as a research model and in application to dairy cattle feeding, by evaluating its effects on performance, serum and urine metabolites, ruminal fermentation characteristics and nutrient apparent digestibility. Four primiparous lactating Chinese Holstein cows fitted with ruminal cannulas were infused with increasing amounts(0, 150, 300, or 450 g/d) of ammonium chloride in a crossover design, each period lasted 4 wk. Two of these cows received increased ammonium chloride for 1 wk for each amount, and the other 2 cows received only water.Effects of NH4 Cl treatment on milk yield and milk composition. Yields of milk(P=0.001), 4% FCM(P=0.002), and ECM(P=0.002) decreased linearly as infusion increased. The quadratic effects approached significance, indicating that the magnitude of decrease tended to be greater when 450 g/d of ammonium chloride was infused. DMI(P=0.0001), milk fat yield(P=0.003) and milk protein(P=0.008) yield decreased linearly as infusion increased. Milk protein concentration(P=0.002) increased linearly with increasing amount of NH4 Cl. Milk lactose concentration(P<0.0001) and yield of milk lactose(P=0.0004) decreased linearly after NH4 Cl increased above 150 g/d. Milk urea nitrogen concentration(P=0.003) increased lineased linearly as infusion increased.Effects of NH4 Cl treatment on serum and urine metabolites. Blood p H(P=0.003) and urine p H(P<0.0001) decreased linearly as infusion increased. The quadratic effects approached significance, indicating that the magnitude of decreases tended to increase when 300 or 450 g/d of NH4 Cl was infused. The concentration of Cl- in serum(P=0.003) increased linearly with infusion; the quadratic effect approached significance because the magnitude of increase tended to be greater when 450 g/d of NH4 Cl was infused. The concentration of Ca2+ in serum(P=0.080) tended to decrease linearly, but Mg2+ in serum(P=0.056) tended to increase linearly with increasing amount of NH4 Cl. Concentrations of PO43- in serum(P=0.020) increased quadratically as infusion increased, with the largest increases when 450 g/d was infused. Urine volume(P=0.025) increased linearly as DCAD decreased. Linear increases in daily excretion of Cl-(P=0.0003), Ca2+(P=0.0009), PO43-(P=0.0016) and UUN(P=0.001), urine ammonium(P=0.004) in urine were observed as NH4 Cl infusion increased and a linear decrease was observed in daily excretion of K+(P=0.014) and urine acid(P=0.015) in urine. Linear increases were observed in serum activities of ALT(P=0.011), AST(P=0.0004), and GGT(P=0.003), as well as the serum concentration of urea(P=0.005), as the amount of NH4 Cl infusion increased. However, serum uric acid(P=0.046) decreased linearly as infusion increased. Concentrations of glucose(P=0.081), creatinine(P=0.084), and indirect bilirubin(P=0.052) tended to increase linearly as NH4 Cl infusion increased.Effects of NH4 Cl treatment on ruminal fermentation characteristics and nutrient apparent digestibility. The content of ruminal ammonia nitrogen increased significantly as ammonium chloride increased(P<0.05); The ruminal p H tended to decrease linearly with increasing amounts of ammonium chloride(P=0.084); There were no significant effects on the concentrations of acetate, propionate, butyrate and other volatile fatty acids(P>0.05). The digestibility of dry matter(P=0.022), organic matter(P=0.041) increased quadratically and ether extract(P=0.019) increased linely as infused ammonium chloride increased.In conclusion, ammonium chloride daily intake of lactating dairy cows should not exceed 300 g, and a more appropriate daily intake may be 150 g.