| The experiment was conducted to study the effects of genistein supplement on the performance and metabolic parameters of Chinese Holstein cows in early lactation periodand the optimal dose.Eight healthy multiparous Chinese Holstein cows in early lactation were chosen. There were four high-yielding cows and four middle-yielding cows, separately with similar milk yield, parity and parturition date and body weight. The 4×4 Latin square experimental design was used to evaluate the effects of dietary genistein supplement. All the cows were fed the basal diet plus one of four different levels (A,B,C and D ) of genistein (0, 10, 20 and 30mg/kg, dry matter based).The results showed that: (1) DMI and Feed efficiency was affected with genistein supplement (P>0.05).(2) The milk yield and 4%FCM yield tended to be higher with genistein supplement and there was no significant difference within treatments (P>0.05).(3) Genistein supplement significantly increased the milk fat percentage and milk protein percentage. The milk fat percentage of high-yield cows supplemented C and D levels of genistein were also increased 34.38% than the cows only fed the basal diet (P <0.01), for the middle-yield cows, milk fat percentage with genistein supplement at the level of C and D significantly increased about 40.58% and 52.17%, comparing to the control diet(P <0.01). the milk protein percentage of middle-yield cows were separately increased 7.61 %, 10.1% and 3.26% with genistein supplement at B, C and D level, compared to A level(P <0.01); high-yield dairy cows fed diet with genistein supplement at the level of B and C increased milk protein percentage about 6.14% and 12.27% than the A level (P <0.01). Genistein supplement increased SNF of high-yield cows. Comparing with the basal diet, diet with genistein supplemented at the level of B and C separately increased SNF about 1.03% (P<0.01) and 4.03% (P<0.01). But genistein supplement had no effects on the milk SNF of middle-yield dairy cows (P>0.05). (4) The apparent digestibilities of crude protein, crude fat, NDF and ADF were not affected by dietary genistein supplement (P>0.05). (5) Effect of genistein on serum triglycerides, total protein, urea nitrogen content were not significant (P>0.05). Dietary genistein supplement decreased serum free fatty acids content of middle-yield cows, especially for the supplement level of C (P<0.05), but had no effects on high-yield cows (P>0.05). (6)Genistein tended to increase serum content of T4 (P>0.05) and GH (P<0.05). The serum GH level of high-yield cows increased about 20.00% (P<0.05) and 114.28% (P<0.01) when supplementing genistein at B and C level, but for the middle yield cows, C and D levels of genistein supplement increased about 203.33% (P<0.01) and 53.33% (P<0.01) than the A level. Dietary genistein could increase serum prolactin (PRL) level, for high-yield cows, serum PRL levels respectively increased 160.69% (P<0.01), 48.76% (P <0.01) and 15.42% (P <0.05) supplemented at the level of B, C and D. Genistein supplement at the levels of C and D had significant effects for the middle-yield cows, serum PRL levels respectively increased 68.26% (P <0.01) and 114.37% (P <0.01). Dietary genistein supplement at the levels of C and D increased serum estradiol (E2) levels of high-yield cows and middle yield cows were increased about 64.04% (P <0.01), 82.53% (P<0.01) and 112.57% (P <0.01), 58.38% (P <0.01). (7)The economic profit declined when dietary genistein supplemented at the level of 10mg/kg, but improved at the level of 20mg/kg and 30mg/kg.The study showed that genistein supplementation was benefit for Chinese Holstein cows in early lactation period and could improve performance of cows and economy profit supplemented at the dose of 20～30mg/kg (diet based).
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