Abstract: 【Objective】The objective of this paper is to study the feed intake, lactation, manure emissions of subclinical hypocalcaemia cows and sewage generated gas pollution emission characteristics. 【Method】 This study was carried out in a Heilongjiang intensive dairy farm. Twelve dairy cows which were similar in postnatal 7-14 days of age, body conditions and parity were selected and divided into subclinical hypocalcaemia group and healthy group, each group had 6 cows, each cow was individually housed, and they were continuously fed for 4 days. Blood samples were taken for measurement of blood Ca, BHBA, NEFA, CLU, P, Mg content indicators every day. Daily milk yield, feed intake, feces and urine of each cow were recorded. Simple dynamic chamber method was used to mix cow manure in the laboratory and NH₃, CO₂ and CH₄ emissions in the mixture were detected and analyzed. 【Result】Cows serum Ca, P and Mg contents in subclinical hypocalcemia symptom group were significantly lower than healthy group (P＜0.01), CLU was significantly lower than that of healthy group (P＜0.05) and BHBA concentration was significantly higher than that of healthy group (P＜0.05) and NEFA concentration was significantly higher than that of healthy cows in healthy group (P＜0.01); milk yield in subclinical hypocalcaemia group was significantly higher than that in healthy group (P＜0.01), 4% energy corrected milk (ECM) was significantly higher than that of healthy cows (P＜0.01) in healthy group, fecal excretion was significantly higher than that of healthy group (P＜0.05); dry matter digestibility and urine volume had no significant difference but a rising trend. Milk yield of cows which were fed 1 kg dry matter was increased significantly (P＜0.01), feces of cows which were fed 1 kg dry matter amount were significantly higher (P＜0.05) in subclinical hypocalcemia calcium group. CH₄ emission curve in healthy group and subclinical hypocalcemia symptom group cows had no significant difference, two groups of gas production trend was basically the same, peak of gas production was on the 52 h, then falling. CO₂ emissions had no significant changes in the trend, no obvious rules, emission peak was appeared in the healthy group and subclinical hypocalcemia symptoms group, respectively, at 36 h and 48 h, the peak in subclinical hypocalcaemia group was appeared earlier than healthy group, and then decreased immediately without regularity and floated up and down. Subclinical hypocalcaemia group of CO₂ cumulative emissions with the passage of time was lower than that of the healthy group; The peak of cows NH₃ emission concentration in healthy group was at 24 hours, then decreased, peaked again at 45 h, emission concentration decreased gradually. The peak of cows NH₃ emission concentration in subclinical hypocalcemia group was appeared at 21 h, then the emission concentration decreased, two groups the test line trend of the two groups were basically the same, all trend were that the peak concentration decreased and floated up and down. The cumulative emissions of NH₃ in subclinical hypocalcemia group were lower than healthy group. 【Conclusion】 During the subclinical hypocalcemia in dairy cows with syndrome of disease due to the feed intake of nutrients can not satisfy the lactation demand in the state of energy and calcium negative balance. At the same time digestive tract absorption rate increased to satisfy the demand of energy lactation; under the same quality of mixed excrements of detection of subclinical hypocalcaemia would not impact on CH₄ emissions, but NH₃ and carbon CO₂ emissions in subclinical hypocalcemia cows manure were lower than that of healthy cows. However, whether reducing greenhouse gas emissions caused the increase of intestinal absorption rate promoted the feed energy uptake still needs to be further studied.

Key words: hypocalcemia, performance, greenhouse gases, faeces, urine, dairy cow