Variation pattern of lactation performance in different parities,lactation stages and somatic cell levels of Montbéliarde x Holstein crossbred cows
[Objectives]This study aimed to compare the differences in lactation performance of Montbéliarde(Mo)× Holstein(Ho)crossbred cows in different parities,lactation stages and somatic cell levels,and analyze their correlation and variation patterns,and provide theoretical basis for the fine management and milk quality improvement of Mo × Ho cows.[Methods]In this study,the lactating cows of crossbreeding progeny with Montbéliarde as the sire and self-bred Holstein cows as the dam were studied.Based on the data from the dairy herd improvement(DHI)report,a comparative study was conducted by parities size(1 and 2 parities),lactation stage(0-99 d,100-199 d,200-299 d and ≥300 d),somatic cell count(SCC)(low SCC,0-1×105 mL-1;medium SCC,＞1×105-2×105 mL-1;high SCC,＞2×105 mL-1)were classified and grouped,and Duncan's multiple comparisons and Pearson's correlation analysis were used for comparative studies.[Results]There was a highly significant difference in milk yield between different parity of Mo × Ho cows(P＜0.01),and the milk yield of the first parity was significantly lower than that of the second parity;milk yield significantly negatively correlated with milk fat percentage(P＜0.05).Fat/protein(F/P)highly significantly positively correlated with milk fat percentage(P＜0.01).There were significant differences in milk yield,milk fat percentage,milk protein percentage,F/P,milk urea nitrogen(MUN),SCC and SCS among Mo x Ho cows at different lactation stages(P＜0.05),with the highest milk yield and lowest SCC at 0-99 d of lactation.There were significant differences in lactation days,milk yield,milk fat rate and F/P at different SCC levels(P＜0.05),with the highest milk yield at low SCC levels.Total milk fat highly significantly positively correlated with total milk protein.In low and medium SCC levels,milk fat rate highly significantly positively correlated with F/P(P＜0.01);in high SCC levels,milk protein rate and F/P significantly negatively correlated with milk fat rate(P＜0.05);[Conclusions]The milk yield and milk composition of Mo x Ho cows differed significantly among different parities,lactation stages and SCC levels,and the milk yield showed a pattern of increasing and then decreasing with the increase of lactation days.The milk fat rate,milk protein rate and F/P showed a trend of first decreasing and then increasing.Therefore,it was necessary to develop corresponding feeding management programs for different parities,lactation stages and somatic cell levels in order to give full play to the production potential and hybrid advantage of Mo × Ho cows and improve economic efficiency.
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