• Asian-Australasian Journal of Animal Sciences
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• v.5 no.2
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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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• v.20 no.1
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• pp.12-18
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• 2007

The objective of the study was to compare ranking of Sahiwal bulls selected on the basis of highest lactation milk yield of their dams with their estimated breeding values (EBVs) using an animal model. Data on 23,761 lactation milk yield records of 5,936 cows from five main Livestock Experiment Stations in Punjab province of Pakistan (1964-2004) were used for the study. At present the young A.I bulls are required to be from A-category bull-dams. Dams were categorized as A, B, C and D if they had highest lactation milk yield of ${\geq}$2,700, 2,250-2,699, 1,800-2,249 and <1,800 litres, respectively. The EBVs for lactation milk yield were estimated for all the animals using an individual animal model having fixed effect of herd-year and season of calving and random effect of animal. Fixed effect of parity and random effect of permanent environment were incorporated when multiple lactation were used. There were 396 young bulls used for semen collection and A.I during 1973-2004. However, progeny with lactation yields recorded, were available only for 91 bulls and dams could be traced for only 63 bulls. Overall lactation milk yield averaged 1,440.8 kg. Milk yield was 10% heritable with repeatability of 39%. Ranking bulls on highest lactation milk yield of their dams, the in-vogue criteria of selecting bulls, had a rank correlation of 0.167 (p<0.190) with ranking based on EBVs from animal model analysis. Bulls' EBVs for all lactations had rank correlation of 0.716 (p<0.001) with EBVs based on first lactation milk yield and 0.766 (p<0.001) with average EBVs of dam and sire (pedigree index). Ranking of bulls on highest lactation yield of their dams has no association with their ranking based on animal model evaluation. Young Sahiwal bulls should be selected on the basis of pedigree index instead of highest lactation yield of dams. This can help improve the genetic potential of the breed accruing to conservation and development efforts.

• Asian-Australasian Journal of Animal Sciences
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• v.10 no.6
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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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• v.12 no.1
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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.

• Animal Bioscience
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• v.35 no.10
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• pp.1499-1511
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• 2022

Objective: This study was aimed to estimate the genetic parameters, including genetic and phenotypic correlations, of milk yield, lactation curve traits and milk composition of Thai dairy cattle from three government research farms. Methods: The data of 25,789 test-day milk yield and milk composition records of 1,468 cattle from lactation 1 to 3 of Holstein Friesian (HF) and crossbred HF dairy cattle calved between 1990 and 2015 from three government research farms in Thailand were analysed. 305-day milk yield was estimated by the Wood model and a test interval method. The Wood model was used for estimating cumulative 305-day milk yield, peak milk yield, days to peak milk yield and persistency. Genetic parameters were estimated using linear mixed models with herd, breed group, year and season of calving as fixed effects, and animals linked to a pedigree as random effects, together with a residual error. Univariate models were used to estimate variance components, heritability, estimated breeding values (EBVs) and repeatability of each trait, while pairwise bivariate models were used to estimate covariance components and correlations between traits in the same lactation and in the same trait across lactations. Results: The heritability of 305-day milk yield, peak milk yield and protein percentage have moderate to high estimates ranging from 0.19 to 0.45 while days to peak milk yield, persistency and fat percentage have low heritability ranging from 0.08 to 0.14 in lactation 1 cows. Further, heritability of most traits considered was higher in lactation 1 compared with lactations 2 and 3. For cows in lactation 1, high genetic correlations were found between 305-day milk yield and peak milk yield (0.86±0.07) and days to peak milk yield and persistency (0.99±0.02) while estimates of genetic correlations between the remaining traits were imprecise due to the high standard errors. The genetic correlations within the traits across lactation were high. There was no consistent trend of EBVs for most traits in the first lactation over the study period. Conclusion: Both the Wood model and test interval method can be used for milk yield estimates in these herds. However, the Wood model has advantages over the test interval method as it can be fitted using fewer test-day records and the estimated model parameters can be used to derive estimates of other lactation curve parameters. Milk yield, peak milk yield and protein percentage can be improved by a selection and mating program while days to peak milk yield, persistency and fat percentage can be improved by including into a selection index.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.2
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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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• v.30 no.8
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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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• v.8 no.4
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• pp.365-368
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• 1995

Lactation curves of dairy cows were generated using three models, namely; incomplete gamma function (model 1), polynomial inverse function (model 2) and non-linear regression (model 3). Secondary milk yield data of 27 cows which had completed 6 lactations were used in this study. Milk yield records (once a week) throughout the lactation and from the first three months of lactation were fitted to the models. Estimation of total milk yield by model 3 using the data once a week throughout the lactation resulted in smaller % bias and standard error than those generated from model 1 and 2. But, model 2 was more accurate in predicting the 305-day milk yield equivalent closer to actual yields with smaller bias % and error using partial records up to 3 months. Also, model 2 was able to estimate the time to reach peak yield close to the actual data using partial records and model 2 could be used as a tool to advise farmers on appropriate feeding and management practices to be adopted.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.4
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• pp.523-531
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• 2008

Buffalo are a major source of milk production, contributing 12.1% in the World and 38.0% in Asia. The buffaloes are kept under peri-urban farming systems to produce milk for urban populations. Breeding is delayed in these herds to get more economic benefit because farmers believe that the pregnancy decreases milk production. The lactation milk value has been studied in this paper as an economic indicator. Complete milk yield records of 3,304 buffaloes was collected from a group of state farms. Economic traits including lactation yield, lactation length, calving interval (CI), dry period and milk yield per day of calving interval (MYPDCI) were derived from the data. The animals were grouped according to parity number (1-3), service period (G1 to G4, conceiving during <150, 150-200, 200-300 and >300 days post calving) and yield levels (HMY>2,500; MMY 2,001-2,500; and LMY 1,500-2,000 liters/ lactation). To study the effect of pregnancy on milk composition a research trial was conducted at a medium size private dairy farm, using forty lactating buffaloes of three yield levels and four service period groups, as described already. Milk was sampled on alternate weeks and analyzed for fat and protein contents (%). For quantifying the value of milk produced during a lactation period, the value corrected milk (VCM) was determined and converted to lactation milk value (LMV). Group means were compared for varicous parameters. Highest milk yield ($2,836.50{\pm}15.68$ liters/lactation) was recorded in the HMY animals of G4 group while lowest milk yield of $1,657.04{\pm}8.34$ liters/lactation was found in LMY of G1. Lactation was significantly increased with the extending of service period. The shortest dry period was recorded in HMY, parity 1, G1 animals and the longest in parity 2, MMY, G4.The CI was shortest in HMY, parity 1, and G1 animals and longest in LMY, parity 3, G4 buffaloes. The HMY, parity 2, G1 buffaloes showed the highest MYPDCI and the lowest value was recorded ($6.53{\pm}0.17$ vs. $2.76{\pm}0.04$ liter/day) for LMY, parity 1, G4 buffaloes. The VCM decreased with the delayed conception. This decreasing trend was higher in respect of the total yield but decrease in the VCM was smaller due to the increasing levels of fat and protein in the milk. The gap between the various production classes was reduced based on the VCM as compared with the yield per day of CI. LMV showed a consistent decline with extending service period in all three production groups. The study suggests that CI increased with delayed conception, showing a consistent trend in the low, moderate and high yielding buffaloes. There was a coherent declining pattern of milk yield with delaying conception, associated with prolonged CI. An animal conceiving at a later stage of lactation showed a decline in financial returns of 24 to 27% compared with those conceiving earlier.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.3
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• pp.343-348
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• 2004

The objective of the present study was to determine the plasma level of insulin-like growth factor-I (IGF-I) in relation to mammary blood flow and milk yield including biological variables of relevance to milk synthesis in two different types of crossbred Holstein cattle at 3 different stages of lactation. Eight heifers were 87.5% HF and eight 50% HF animals were selected for the experiments. The three stages of lactation tested were: early lactation (30 days postpartum), mid-lactation (120 days postpartum) and late lactation (210 days postpartum). Animals in each group were fed a concentrate and rice straw treated with 5% urea as the source of roughage throughout the experiments. In early lactation, mammary blood flow and milk yield of 87.5% HF animals were significantly higher than those of 50% HF animals. In mid- and late lactation, both mammary blood flow and milk yield showed a proportional decrease from the early lactating period of 87.5% HF animals. The trends for persistency were observed in 50% HF animals as for udder blood flow and milk yield throughout the experimental periods. The plasma glucose level of the 50% HF animals was significantly higher than those of 87.5% HF animals in both early and mid-lactation. The concentrations of arterial plasma free fatty acids ($C_{16}\;to\;C_{18}$) were higher in 50% HF animals as compared with 87.5% HF animals in all periods of study. In early lactation, the concentration of plasma growth hormone (GH) of 87.5% HF animals was higher than those of the 50% HF animals, thereafter the mean level of plasma growth hormone declined in both mid- and late lactation. The concentration of plasma IGF-I of 50% HF animals was significantly higher than those of 87.5% HF animals in all stages of lactation. There were no differences among stages of lactation for the levels of plasma IGF-I, insulin and growth hormone in 50% HF animals. In 87.5% HF animals, the plasma levels of both IGF-I and insulin were lower in early lactating period while it showed an increase during mid- and late lactation. The present results indicated that the regulatory role for the higher mammary blood flow and milk yield during lactation in 87.5% HF are not mediated via the higher level of circulating IGF-I. Differences in mammary blood flow and milk yield between 50% HF and 87.5% HF animals are in part due to a higher concentration of circulating growth hormone. The lower level of circulating growth hormone in 50% HF animals would be regulated by higher levels of IGF-I, free fatty acid and glucose in plasma.