• Asian-Australasian Journal of Animal Sciences
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• 제28권9호
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• pp.1226-1234
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• 2015

The development of effective genetic evaluations and selection of sires requires accurate estimates of genetic parameters for all economically important traits in the breeding goal. The main objective of this study was to assess the relative performance of the traditional lactation average model (LAM) against the random regression test-day model (RRM) in the estimation of genetic parameters and prediction of breeding values for Holstein Friesian herds in Ethiopia. The data used consisted of 6,500 test-day (TD) records from 800 first-lactation Holstein Friesian cows that calved between 1997 and 2013. Co-variance components were estimated using the average information restricted maximum likelihood method under single trait animal model. The estimate of heritability for first-lactation milk yield was 0.30 from LAM whilst estimates from the RRM model ranged from 0.17 to 0.29 for the different stages of lactation. Genetic correlations between different TDs in first-lactation Holstein Friesian ranged from 0.37 to 0.99. The observed genetic correlation was less than unity between milk yields at different TDs, which indicated that the assumption of LAM may not be optimal for accurate evaluation of the genetic merit of animals. A close look at estimated breeding values from both models showed that RRM had higher standard deviation compared to LAM indicating that the TD model makes efficient utilization of TD information. Correlations of breeding values between models ranged from 0.90 to 0.96 for different group of sires and cows and marked re-rankings were observed in top sires and cows in moving from the traditional LAM to RRM evaluations.

• Asian-Australasian Journal of Animal Sciences
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• 제33권9호
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• pp.1387-1399
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• 2020

Objective: The objective of this study was to estimate the genetic parameters and trends for milk, fat, and protein yields in the first three lactations of Thai dairy cattle using a 3-trait,-3-lactation random regression test-day model. Methods: Data included 168,996, 63,388, and 27,145 test-day records from the first, second, and third lactations, respectively. Records were from 19,068 cows calving from 1993 to 2013 in 124 herds. (Co) variance components were estimated by Bayesian methods. Gibbs sampling was used to obtain posterior distributions. The model included herd-year-month of testing, breed group-season of calving-month in tested milk group, linear and quadratic age at calving as fixed effects, and random regression coefficients for additive genetic and permanent environmental effects, which were defined as modified constant, linear, quadratic, cubic and quartic Legendre coefficients. Results: Average daily heritabilities ranged from 0.36 to 0.48 for milk, 0.33 to 0.44 for fat and 0.37 to 0.48 for protein yields; they were higher in the third lactation for all traits. Heritabilities of test-day milk and protein yields for selected days in milk were higher in the middle than at the beginning or end of lactation, whereas those for test-day fat yields were high at the beginning and end of lactation. Genetics correlations (305-d yield) among production yields within lactations (0.44 to 0.69) were higher than those across lactations (0.36 to 0.68). The largest genetic correlation was observed between the first and second lactation. The genetic trends of 305-d milk, fat and protein yields were 230 to 250, 25 to 29, and 30 to 35 kg per year, respectively. Conclusion: A random regression model seems to be a flexible and reliable procedure for the genetic evaluation of production yields. It can be used to perform breeding value estimation for national genetic evaluation in the Thai dairy cattle population.

• Asian-Australasian Journal of Animal Sciences
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• 제19권3호
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• pp.315-318
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• 2006

Associations were analysed between polymorphisms localized in intron 3 of the growth hormone gene (GH-MspI) and milk production traits of 543 China Holstein cows. A PCR-RFLP method was used for identification of genotypes. The following frequencies of genotypes and alleles were found: 0.77, 0.21 and 0.02 for +/+, +/- and -/-, respectively, and 0.87 and 0.13 for $GH^+$ and $GH^-$, respectively. Significant differences between herds were observed in the frequencies of both genotypes and alleles. The results of least squares analysis showed that in all three lactation phases the GH +/+ cows yielded most milk (p<0.01 for lactation I and p<0.05 for lactations II and III), whereas +/- cows showed higher milk fat content than +/+ individuals (p<0.05 for lactation I and II, and p<0.01 for lactation III). The +/+ cows yielded more fat than +/- individuals (p<0.01 only in lactation I). The +/+ cows yielded more milk protein than +/- individuals (p<0.01 for lactation I, II, and III). The +/+ cows produced milk of higher protein content than that of +/- individuals (p<0.05 only in lactation II). Based on these results, we conclude that the +/+ of GH locus should be the favored genotype in China Holstein cow breeds for use in marker-assisted selection programmes.

• Asian-Australasian Journal of Animal Sciences
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• 제17권4호
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• pp.533-537
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• 2004

The experiment was conducted to test the hypothesis that supplementing diets of lactating first parity sows with a mixture of carbohydrases (CS) improves lactation performance and second parity reproductive performance. The CS used in this study contained 7 units/g of $\alpha$-1,6-galactosidase, 22 units/g of $\beta$-1,4-mannanase, $\beta$-1,4-mannosidase and trace amounts of other enzymes. Twenty primiparous sows (Newsham Hybrid) were allotted to either the control group (no CS supplement) or the CS group (0.1% CS supplement) and fed the experimental diets during 21 d lactation period. Sows and nursing pigs were weighed at birth and weekly until weaning. Days of weaning-to-estrus were recorded. Sows had free access to feed and water. Feed intake of sows was measured daily. During the second parity gestation and lactation, all the sows were fed the same gestation and lactation diets and their reproductive performance was measured. During the second parity, there were 14 sows (7 sows per group) remained productive. For the first lactation, maternal body weight loss of the CS group was smaller (p<0.05) than that of the control group. There was no difference in litter weight gain between two groups. Voluntary feed intake of sows did not differ between the two groups. Days of weaning-to-estrus of the CS group were smaller (p<0.05) than those of the control group. In the second parity, there was no difference in the reproductive performance between the two groups. In conclusion, supplementing CS in the diet of lactating sows during the first parity decreased body weight loss and days of weaning-to-estrus of sows. However, these effects of the CS supplementation in the first parity were not successfully carried over to the second parity.

• 한국임상수의학회지
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• 제24권2호
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• pp.197-200
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• 2007

The purpose of this study was premature induction of lactation in the transgenic calf to confirm the expression of human lactoferrin gene in the milk as early as possible. We performed the induction of lactation in 6 normal 1-month old calves and 3 normal and 1 transgenic 5-month old calves. In order to induction of lactation, 1-month old calf was injected with estradiol benzoate (0.2 mg/kg), $17-{\beta}$ estradiol cypionate (0.1 mg/kg) and progesterone (0.25-0.5 mg/kg) in every other day by 21 days. After 10 days cessation of administration, dexamethasone (0.028 mg/kg) was injected intramuscularly, however, lactation was failed. In the 5-month old calves, estradiol benzoate (0.2 mg/kg) and progesterone (0.5 mg/kg) were injected individually every other day during 21 days. After 10 days cessation of administration, dexamethasone (0.1 mg/kg) was injected intramuscularly and milk was lactated in the next day. Lactation was successfully induced in the 5-month old normal and transgenic calves and we confirmed the lactoferrin gene in the milk of transgenic calf. In conclusion, confirmation of human lactoferrin gene expressed in the milk of the transgenic calf was possible in 20 months earlier than in normal condition.

• Journal of Nutrition and Health
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• 제3권2호
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• pp.81-85
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• 1970

These experiments were designed to study the influence of protein undernutrition during lactation period(3 wks) or after-weaning period(8 wks) on growth of organs, and on brain and liver composition of the experimental rats. The following experimental groups were studied. Group No. Rats Lactation(3 wks) (Diet of mother rat) After-weaning period(8wks) Rehabilitation Period(17wks) I 8 25% Casein diet 25% Casein diet 25% Casein diet II 8 12% Casein diet 25% Casein diet 25% Casein diet III 8 25% Casein diet 5% Casein diet 25% Casein diet IV 8 12% Casein diet 5% Casein diet 25% Casein diet After the perriod of rehabilitation(17 wks) with 25% casein diet, the following results were obtained. 1. Most of the organs except the spleen could not catch up with the normal group in their weights for the group of protein undernutrition during lactation(3 wks), even after 17 weeks of rehabilitation. For the group of protein undernutrition during after-weaning period(8 wks) brain, lung, heart, spleen and pancreas could catch up with the normal group after rehabilitation. According to this result it is assumed that the growth of brain, lung, heart and pancreas might be developed mostly during lactation and that the growth of liver and kidney might be developed after-weaning period continuously. 2. For the groups of protein underuntrition during lactation period or after-weaning period the amounts of total lipid, cholesterol and phospholipid of brain were lower than those of normal group. Especially, cholesterol level was significantly lower than normal group. And there was also a significant difference in the phospholipid level of the after-weaning(8 wks) deprivation group. 3. The groups of protein undernutrition during lactation or after-weaning period(8 wks) showed lower level of liver nitrogen and higher level of liver fat. Especially, protein undernutriton during lactation gave a greater influence on the lever of liver fat.

• Animal Bioscience
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• 제35권8호
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• pp.1151-1161
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• 2022

Objective: This study was conducted to estimate the association of age at first calving (AFC) with first lactation traits as well as lifetime performance traits in Murrah buffaloes. Methods: Data on first lactation and life time performance of Murrah buffaloes (n = 679), maintained at Indian Council of Agricultural Research-Central Institute for Research on Buffaloes, Hisar, India during the period 1983 through 2017, were deduced to calculate heritability estimates, genetic and phenotypic correlation of different first lactation and lifetime traits. The univariate animal model was fitted to estimate variance components and heritability separately for each trait, while bivariate animal models were set to estimate genetic and phenotypic correlations between traits under study. Results: The heritability was high for first peak milk yield (FPY, 0.64±0.08), moderate for AFC (0.48±0.07) and breeding efficiency (BE 0.39±0.09). High genetic correlations of first lactation total milk yield (FLTMY) with first lactation standard milk yield (FLSMY, 305 days or less), FPY, and first lactation length (FLL) was seen. Likewise, genetic correlation of AFC was positive with FLTMY, FLL, first dry period (FDP), first service period (FSP), first calving interval (FCI), herd life (HL) and productive days (PD). Significant phenotypic correlation of FLTMY was observed with HL, productive life (PL), PD, total lifetime milk yield (LTMY), standard lifetime milk yield (standard LTMY). Moreover, positive genetic and phenotypic correlation of FPY was observed with HL, PL, PD, total LTMY and standard LTMY. Conclusion: This study reports that AFC had positive genetic correlation with FDP, FSP, FCI, and unproductive days while, negative association of AFC was observed with FLSMY, PL, total LTMY, standard LTMY, and BE. This suggests that reduction of AFC would results in improvement of lifetime performance traits.

• Asian-Australasian Journal of Animal Sciences
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• 제22권7호
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• pp.923-930
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• 2009

This study was conducted to compare three models: two random regression models with and without considering heterogeneity in the residual variances and a lactation model (LM) for evaluating the genetic ability of Holstein cows in Korea. Two datasets were prepared for this study. To apply the test-day random regression model, 94,390 test-day records were prepared from 15,263 cows. The second data set consisted of 14,704 lactation records covering milk production over 305 days. Raw milk yield and composition data were collected from 1998 to 2002 by the National Agricultural Cooperative Federation' dairy cattle improvement center by way of its milk testing program, which is nationally based. The pedigree information for this analysis was collected by the Korean Animal Improvement Association. The random regression models (RRMs) are single-trait animal models that consider each lactation record as an independent trait. Estimates of covariance were assumed to be different ones. In order to consider heterogeneity of residual variance in the analysis, test-days were classified into 29 classes. By considering heterogeneity of residual variance, variation for lactation performance in the early lactation classes was higher than during the middle classes and variance was lower in the late lactation classes than in the other two classes. This may be due to feeding management system and physiological properties of Holstein cows in Korea. Over classes e6 to e26 (covering 61 to 270 DIM), there was little change in residual variance, suggesting that a model with homogeneity of variance be used restricting the data to these days only. Estimates of heritability for milk yield ranged from 0.154 to 0.455, for which the estimates were variable depending on different lactation periods. Most of the heritabilities for milk yield using the RRM were higher than in the lactation model, and the estimate of genetic variance of milk yield was lower in the late lactation period than in the early or middle periods.

• 한국가축번식학회지
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• 제24권1호
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• pp.35-40
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• 2000

본 연구는 Wistar계 rat를 이용하여 포유기간 중 제한포유시기와 이유시기를 조절하여, 혈중 IGF- I 수준변화에 대해 검토하였다. NL군 (NL)은 포유자의 수를 8 마리로 조절하였으며, RL군 (RL)과 W군 (W)은 RL0, RL0, RL10, RLl5 및 RL20, 그리고 W0, W5, WI0, W15 및 W20으로 각각 5개 군으로 구분하여, RL군은 각 개시일에 포유자의 수를 8마리에서 4마리로 조절하였으며, W군은 각 개시일에 포유자의 수를 완전히 이유시켜 다음과 같은 결과를 얻었다. 1. NL군의 혈중 IGF-I 농도는 분만직후 (Day 0) 750.59$\pm$3.52ng/$m\ell$ 을 나타내어 15일까지 일정한 수준을 유지하다가 그 후 포유 25일에 1,690.20$\pm$4.42ng/$m\ell$ 까지 증가되었다. 2. 포유초기 RL군 (RL0, RL5)의 IGF- I 농도는 포유 10일에 RL0군과 RL5군에서 각각 1,395.90$\pm$3.45 및 1,351.73$\pm$3.23ng/$m\ell$로서 NL 군의 745.96$\pm$2.24ng/$m\ell$ 보다 유의적 (P＜0.05)으로 높게 나타났으나 포유 15일부터는 차이가 없었다. 3. 포유초기 W군의 IGF- I 농도는 이유 후 일주일 정도는 NL군에 비해 높은 수준 (P＜0.05)을 나타내다가 10일경에 NL군과 같은 수준으로 감소하였다. 포유자극의 강약은 난소의 생리적 변화와 함께 혈중 IGF- I의 농도를 조절하는 것으로 사료된다.

• Preventive Nutrition and Food Science
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• 제1권2호
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• pp.230-233
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• 1996

The purposes of this study was to investigate selenium content of human milk and selenium intake of breast-fed infants at each period of lactation longitudinally. The human milk intake in breast-fed infants was measured by test weighing method from 20 lactating mothers at 1,2 and 3 months postpartum. Selenium content in the milks was determined by atomic absorption spectrophotometry with hydride generation after wet digestion of samples. Selenium intake in breast-fed infants was calculated by multiplying human milk intakes by selenium contents. The milk intakes were 640, 726 and 715g/day at 1,2 and 3 months postpartum. The selenium contents in human milk were characterized by a pattern of slight decline with advancing stage of lactation;13.1, 11.5 and 9.8$\mu\textrm{g}$/L at 1,2 and 3 months during lactation. There was a large individual variation at any stage of this study. The mean dietary selenium intakes in breast-fed infants were 8.38, 8.32 and 6.97$\mu\textrm{g}$/day at 1,2 and 3 months postpartum, respectively. The mean daily intakes on a body weight basis were gradually decreased during the course of lactation.