Study On Models For Lactation Curve Analysis Of Cows And Mammary Gland Cell Apoptosis And Expression Of Enzymes Related In Lactation Of Kunming Mice

This study can be comprised of two parts,first of which,with the purpose of providing conferences on management of dairy herd by proposing ideal lactation curve model and production record interval,was conducted to investigate the fitting performances of four mathematical models based on data of different intervals between test-days. In the second part,Kunming mouse were provided diets that had different fat levels but the same energy and protein density, to study its effects on lactation. We hope the second trail can enrich lactation physiology and serve as a foundation for the further research on lactation curve models.In the first trail, four lactation curve models were fitted to the production data, which based on the information of 108 lactations of 103 cows obtained from Qingdao liuhe dairy.For each lactation, the data sets of DIM were made according to the following criteria: the only interval from calving to first test (5d) and five intervals between tests (1,10,20,30 and 40d). The parameters of models were estimated according to the results of Marquardt iteration in NLIN of SAS 8.2. The effects of models and test-day intervals on predictions were analyzed based on their predicted deviations on milk day yield and 305d yield.Results suggested that the predicted deviations of 305d yield of ALI model was higher than that of others (P<0.05), but no significant difference was detected among other three models' predicted deviations(P>0.05); the intervals of 30d and 40d served higher deviations of predictions on 305d yield(P<0.05).The results analyzed on predictions of 305d yield among models except ALI indicated that the interval of 40d made the highest deviation, and intervals of 30d and 20d were minor, the other two intervals were the lowest(P<0.05).The predictions on yield of DIM become worse when the interval was extended. In the second trail, the uniparous Kunming mouse were chosen as the study objectives. The diets were designed based on GB1424.3-2001,contained different fat but a same energy density,and the diets were accomplished by regulating the ratio of corn and bean oil.The samples were collected at three days before parturition,one day before parturition ,1d,4d,7d,10d,13d,17d,20d in lactation.The indexes analyzed in experiment were blood serum hormones (prolactin, estrogen and progesterone),cell apoptosis in mammary gland detected by TUNEL,the mRNA expression of enzymes related in lactation (FAS,a-ACC,GT) and p-casein.The main results indicated that the diets with higher fat degraded the productive performance(P<0.05) and the expression of GT mRNA(P=0.14) of mouse, elevated the expression of a-ACC mRNA (P=0.07); the mammary cell apoptosis was clearly detected in the sample that collected from the day before parturition,and wasn't detected in the samples in lactation; the levels of all the blood serum hormones of mouse degraded significantly (P<0.05) after pauturition,but didn't have a consistent change in lactation;the treatments of diets didn't have significant effects on blood serum prolactin,but affect the other two hormones significantly (P<0.05); the expressions of all the mRNA detected in this trail differed significantly (P<0.05) among the different times, but didn't differ significantly among diets(P>0.05).