[Objective] This study aimed to estimate the genetic parameters for milk yield, fat percentage, fat yield and age at first freshening of Chinese Holsteins first lactation cows in Heilongjiang under frigid-temperature ...[Objective] This study aimed to estimate the genetic parameters for milk yield, fat percentage, fat yield and age at first freshening of Chinese Holsteins first lactation cows in Heilongjiang under frigid-temperature and temperature zone. [Method] Records of yield and reproduction from 8 868 Chinese Holstein first lacta- tion cows from 21 herds were utilized to evaluate genetic parameters for Hei- Iongjiangs＇ Chinese Holsteins. Restricted maximum likelihood （REML） method was used with an animal model. [Result] The heritabilities were 0.16 to 0.34 for yields and fat percentage, 0.38 for reproduction （age at the first freshening）, which were similar to estimates for temperate areas from similar methods, except for constituent percentage. Also, the estimates of genetic correlation were high between milk yield and fat yield （0.97）, but were low between milk yield and fat percentage （-0.24）, age at the first freshening （-0.29） and generally antagonistic. [Conclusion] Thus, es- timates of genetic parameters in this frigid and frigid-temperate environment did not differ appreciably from those that occur in temperate dairy areas.展开更多
The objective of this study was to investigate the effect of Palm Oil By-pass Fat （POBF） on milk composition of early lactation Holstein during dry season, 24 postpartum Holstein （1 d-14 d） were selected and align...The objective of this study was to investigate the effect of Palm Oil By-pass Fat （POBF） on milk composition of early lactation Holstein during dry season, 24 postpartum Holstein （1 d-14 d） were selected and align to two groups according to CRD experimental design; each group included 12 Holstein cows. The control received by-pass fat 0 g/h.d, the experimental group received by-pass fat 300 g/h.d. The results shown, DMI and yield of milk did not be affected with supplementation of by-pass fat, however, milk protein increased by 6.71%, milk fat increased by 8.16%, lactose increased by 0.22%, SNF increased by 1.98%, TS increased 4.08%; digestibility of diet protein decreased by 6.62%, digestibility of EE decreased by 7.96%, digestibility of NDF and ADL decreased by 1.36%, 8.97% respectively, digestibility of DM and OM decreased by 4.42, 3.07 percentage units; amount of C4-C17 milk fatty acids showed a decreased tendency, that of CIs-C22 showed an increased tendency, the milk CLA increased significantly （P 〈 0.01）. To sum up, supplementation of by-pass fat for early lactation Holstein is an important measure to balance energy and sustain milk yield and quality.展开更多
文摘[Objective] This study aimed to estimate the genetic parameters for milk yield, fat percentage, fat yield and age at first freshening of Chinese Holsteins first lactation cows in Heilongjiang under frigid-temperature and temperature zone. [Method] Records of yield and reproduction from 8 868 Chinese Holstein first lacta- tion cows from 21 herds were utilized to evaluate genetic parameters for Hei- Iongjiangs＇ Chinese Holsteins. Restricted maximum likelihood （REML） method was used with an animal model. [Result] The heritabilities were 0.16 to 0.34 for yields and fat percentage, 0.38 for reproduction （age at the first freshening）, which were similar to estimates for temperate areas from similar methods, except for constituent percentage. Also, the estimates of genetic correlation were high between milk yield and fat yield （0.97）, but were low between milk yield and fat percentage （-0.24）, age at the first freshening （-0.29） and generally antagonistic. [Conclusion] Thus, es- timates of genetic parameters in this frigid and frigid-temperate environment did not differ appreciably from those that occur in temperate dairy areas.
文摘The objective of this study was to investigate the effect of Palm Oil By-pass Fat （POBF） on milk composition of early lactation Holstein during dry season, 24 postpartum Holstein （1 d-14 d） were selected and align to two groups according to CRD experimental design; each group included 12 Holstein cows. The control received by-pass fat 0 g/h.d, the experimental group received by-pass fat 300 g/h.d. The results shown, DMI and yield of milk did not be affected with supplementation of by-pass fat, however, milk protein increased by 6.71%, milk fat increased by 8.16%, lactose increased by 0.22%, SNF increased by 1.98%, TS increased 4.08%; digestibility of diet protein decreased by 6.62%, digestibility of EE decreased by 7.96%, digestibility of NDF and ADL decreased by 1.36%, 8.97% respectively, digestibility of DM and OM decreased by 4.42, 3.07 percentage units; amount of C4-C17 milk fatty acids showed a decreased tendency, that of CIs-C22 showed an increased tendency, the milk CLA increased significantly （P 〈 0.01）. To sum up, supplementation of by-pass fat for early lactation Holstein is an important measure to balance energy and sustain milk yield and quality.
