• Asian-Australasian Journal of Animal Sciences
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• 제5권2호
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• pp.375-382
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• 1992

The effect of certain factors such as sex of calf, status of buffalo, season of calving, parity and sire on lactation length and total lactation yield was studied in 391 Nili-Ravi buffaloes. The average lactation length was $301.73{\pm}1.87$ (mean $\pm$ SE) days with a range of 181 to 505 days whereas the average lactation yield was $2031.08{\pm}19.16kg$ and ranged from 1023 to 6535 kg for 984 lactations. The differences in the means of lactation length and lactation yield due to the sex of calf were significant (p<0.05). The status of buffaloes had a significant (p<0.05) effect on lactation length but its effect on lactation yield was non-significant. The season of calving had no effect on lactation length but it influenced the lactation yield significantly. The milk yield was highest ($2150.81{\pm}43.52kg$) in buffaloes which calved in spring and lowest ($1959.92{\pm}30.83kg$) in autumn. The effect of parity on both traits under study was significant (p<0.01). The maximum and minimum lactation lengths of $309.82{\pm}3.96$ and $284.16{\pm}7.17$ days were observed in the first and sixth lactations, respectively. The milk yield was maximum ($2150.38{\pm}58.79kg$) in the seventh lactation and minimum (1818.31 60.04 kg) in the sixth lactation. The influence of sire was significant on lactation length (p<0.05) and milk yield (p<0.01).

• Asian-Australasian Journal of Animal Sciences
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• 제10권6호
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• pp.567-570
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• 1997

A multiple trait animal model having milk yield and lactation length was used to estimate genetic parameters using data from four institutional herds and four field recording centers. Response to selection for milk yield alone and in combination with lactation length was estimated by using principles of genetic theory. Lactation records (n = 2,353) adjusted for age at calving to 60 months were utilized. Milk yield was 17% heritable with repeatability of 0.44. Lactation length had a low heritability of 0.06 with repeatability of 0.16. Genetic correlation between the two traits was 0.70. Selection response in milk yield can be improved slightly (103.8 vs 102.8 kg) when information on covariance with lactation length is used together with the information on milk yield.

• Asian-Australasian Journal of Animal Sciences
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• 제12권2호
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• pp.161-164
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• 1999

Dairy performances of Pabna cows and its crossbreds with Sahiwal (SL) and Friesian (F) in the Baghabarighat dairying area of Bangladesh were evaluated. Four SL and three F sires were used for the crossbreeding. The exotic sire effect of individuals on their daughters were also evaluated in this study. It showed that the genetic group had a significant (p<0.05) effect on birth weight, age at first heat, calving interval, lactation length and lactation yield. The lowest birth weight (17.9 kg), longest age at first heat (39.2 m) and calving interval (16.3 m) shortest lactation length (199 d) and lowest lactation yield (728 L) were found in Pabna cows. The highest birth weight (22.5 kg). shortest age at first heat (25.5 m) and calving interval (13.7 m), longest lactation length (253 d) and highest lactation yield (1936 L) were found in the F crossbreds. Within the same breed, the effect of individual sire was significant (p<0.05) on age at first heat, lactation length and lactation yield. Individual sire effects of SL bulls differed significantly (p<0.05) but F sires had a non-significant (p>0.05) effect on calving interval in their progeny. The fat % and SNF % in milk and number of services required for conception did not differ (p>0.05) among inter-and intra- breed sire groups.

• Asian-Australasian Journal of Animal Sciences
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• 제12권1호
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• pp.56-60
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• 1999

Production and reproduction data of 47 Nili-Ravi buffaloes (162 records) were analyzed with regression techniques. Average lactation milk yield was $2,020.04{\pm}44.59$ liters, lactation length $277.42{\pm}5.70$ d and calving interval $467.10{\pm}11.58$ d. The ranges for these parameters respectively were : 609-3591 lit, 122-614 d and 228-982 d. Year of calving and lactation length had significant effect on total milk yield (p < 0.01), whereas other factors such as month of calving, lactation number and calving interval had no effect on total lactation milk yield. Year of calving had influenced significantly other traits (p < .01) such as calving interval and lactations completed. This indicated considerable environment role in buffalo productivity. Effect of month of calving on total lactation milk yield and other traits was however, found to be non-significant. Nili-Ravi buffaloes produced maximum milk during their first three lactations as compared to subsequent lactations. Regression model explained 40 percent variation in total lactation milk yield due to factors analyzed : animal (dam), year and month of calving lactation length and calving interval.

• Asian-Australasian Journal of Animal Sciences
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• 제15권5호
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• pp.695-698
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• 2002

Performance data (from 1985 to 2000) of Jersey cattle imported from USA and maintained at Islamabad, Pakistan were evaluated. The purpose of this study was to assess the genetic merit of Jersey breed under Pakistani environment for further propagation. Cows with at least two calvings were considered for this study; records on 50 daughter-dam pairs were available on production and reproduction performance traits for genetic evaluation. The average age at first calving in parents was $25.2{\pm}2.4$ m as compared to $23.9{\pm}6.6$ m in progeny. Calving interval in parents and progeny was $416{\pm}74$ and $446{\pm}105$ d; lactation length $301{\pm}51$ and $325{\pm}73$ d; lactation milk yield $2,908{\pm}669$ and $2,707{\pm}903$ lit respectively. All these differences were found to be statistically significant except lactation length. The correlations between age at first calving and total lactation milk was -0.25, between calving interval and total lactation milk yield was 0.14, and between lactation length and total lactation milk yield was 0.79. The $h^2$ of these traits were low indicating important role of environment in expressing the genetic potential of animals. The S.E of $h^2$ of all the traits was high due to large variation in data.

• Asian-Australasian Journal of Animal Sciences
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• 제30권8호
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• pp.1093-1098
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• 2017

Objective: The aim of the current study was to describe the relationship between milk yield and lactation number, stage, length and milking frequency in Korean Holstein dairy cows using an automatic milking system (AMS). Methods: The original data set consisted of observations from April to October 2016 of 780 Holstein cows, with a total of 10,751 milkings. Each time a cow was milked by an AMS during the 24 h, the AMS management system recorded identification numbers of the AMS unit, the cow being milking, date and time of the milking, and milk yield (kg) as measured by the milk meters installed on each AMS unit, date and time of the lactation, lactation stage, milking frequency (NoM). Lactation stage is defined as the number of days milking per cows per lactation. Milk yield was calculated per udder quarter in the AMS and was added to 1 record per cow and trait for each milking. Milking frequency was measured the number of milkings per cow per 24 hour. Results: From the study results, a significant relationship was found between the milk yield and lactation number (p<0.001), with the maximum milk yield occurring in the third lactation cows. We recorded the highest milk yield, in a greater lactation length period of early stage (55 to 90 days) at a $4{\times}$ milking frequency/d, and the lowest milk yield was observed in the later stage (>201 days) of cows. Also, milking frequency had a significant influence on milk yield (p<0.001) in Korean Holstein cows using AMS. Conclusion: Detailed knowledge of these factors such as lactation number, stage, length, and milking frequency associated with increasing milk yield using AMS will help guide future recommendations to producers for maximizing milk yield in Korean Dairy industries.

• Asian-Australasian Journal of Animal Sciences
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• 제15권1호
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• pp.7-10
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• 2002

The breeding data relating to Hariana herd spread over 18 years (1979-96) were analysed to estimate genetic, phenotypic and environmental changes in characters of economic importance which might have taken place during the several years of selective breeding practiced in the herd. The average genetic changes in a given character were estimated by four methods. The phenotypic trends observed for different economic traits were not significant. On changing the method of estimation, magnitude and direction of genetic trends changed. Comparison of estimates of genetic trends by different methods showed that adjustments for biases due to non-random allotment of dams with respect to their age and merit suggested by Powell and Freeman (1974) were useful for increasing the precision of the estimates. Hence, this method was found to be the best method for estimation of genetic trends. The estimate of genetic trends by this method were 4.03${\pm}$6.21 days, 3.24${\pm}$5.33 kg, 0.15${\pm}$0.43 days, 0.09${\pm}$0.59 days, 0.01${\pm}$0.02 kg and 0.01${\pm}$0.01 kg for age at first calving, first lactation milk yield, first lactation length, first calving interval, first lactation milk yield per day lactation length and first lactation milk yield per day of calving interval, respectively.

• Asian-Australasian Journal of Animal Sciences
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• 제15권6호
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• pp.890-894
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• 2002

The accuracy of the gamma function to describe lactation curve of Yankasa ewes was investigated using milk production data obtained from 168 ewes with either complete or incomplete 84 day lactation records. Ewes were daily hand milked after over-night separation from lamb and thorough disinfection of the udder. The daily milk yield on the average was estimated from the weekly total yield. The effect of type of birth, parity, season of birth and lactation length on the components of lactation curve (a, b, c and s) were analysed by least-square procedures. All factors except parity significantly (p<0.01) influenced the curve parameters. The goodness of fit of the function did not differ between the two classes of varying duration of lactation; incomplete lactation however, showed a lower persistency and as expected lower level of production. Correlations ($r_p$) between lamb weight gain and milk yield using the weight records from lamb weighed at weekly intervals indicated a high and positive relationship in the early lactation that decreased in intensity as the lactation advanced.

• Animal Bioscience
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• 제34권6호
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• pp.949-956
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• 2021

Objective: This study was focused on the estimation of parameters of Wood's model and description of the lactation curve using the cows which were lactated over 24 months on the first lactation. Methods: The database included 1,333 pure-bred dairy Simmental primiparous cows which lactated for 24 months (732 days). The initial dataset entering the procedure of assessment of parameters of Wood's function included 35,826 milk yield records. Milk yield was recorded throughout lactation, with the earliest record taken on day 6 and the latest on day 1,348 of lactation. This dataset was used for the assessment of parameters a, b, c of Wood's model using the non-linear statistical procedure. These parameters were estimated for different length of lactation. The assessed parameters were used for calculation of some characteristics of lactation curves. Results: The lowest value of a parameter (15.2317) of Wood's model of lactation curve was found out in lactations up to 305 days long, contrary to b and c parameters which were highest in those lactations (0.1029 and 0.0015, respectively). The maximum value of a parameter (17.4329) was found out in lactations up to 640 days long, unlike b and c parameters which were minimal in those lactations (0.0603 and 0.0010, respectively). Conclusion: It can be concluded that the parameters of Wood's model and the shape of lactation curve are changing with the growing number of milk yield records. Also, the assessed parameters revealed a significant milk production potential after 305 days of lactation.

• Asian-Australasian Journal of Animal Sciences
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• 제15권3호
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• pp.315-320
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• 2002

Test-day records (n=13677) sampled from 896 ewes in 5-9 (${\mu}$=7.5) monthly test-days were used to estimate genetic and phenotypic parameters of test-day yields, lactation milk yield (TMY), length of the milking period (DAYS) and three measures of persistency of milk yield in Boutsico dairy sheep. Τhe measures of persistency were the slope of the regression line (${\beta}$), the coefficient of variation (CV) of the test-day milk yields and the maximum to average daily milk yield ratio (MA). The estimates of variance components were obtained under a linear mixed model by restricted maximum likelihood. The heritability of test-day yields ranged from 0.15 to 0.24. DAYS were found to be heritable ($h^2$=0.11). Heritability estimates of ${\beta}$, CV and MA were 0.15, 0.13, 0.10, respectively. Selection for maximum lactation yields is expected to result in prolonged milking periods, high rates of decline of yields after peak production, variable test-day yields and higher litter sizes. Selection for flatter lactation curves would reduce lactation yields, increase slightly the length of the milking period and decrease yield variation as well as litter size. The most accurate prediction of TMY was obtained with a linear regression model with the first five test-day records.