Effects of Herbal Feed Additive on Milk Production of Dairy Cows

[Objective] The aim of this study was to investigate the efficacy of the herbal feed additive Zengrujianniusan on the milk production of dairy cows. [Method] Thirty-two black-white lactating cows were randomly divided into four groups, and were fed with forage supplemented with 0 （control group）, 0.2%, 0.4% and 0.6% Zengrujianniusan for 60 d. During this period, the contents of fat, protein and non-fat solid in milk were measured every 20 d. [Result] The milk production of the cows whose forage was added with 0.2 %, 0.4 % and 0.6% Zengrujianniusan was 4.02%, 12.50%, 14.00% higher than that of the control （P〉0.05）. The herbal feed additive had no significant influence on the contents of fat, milk and non-fat solid in milk, but significantly reduced the number of somatic cells. [Conclusion] The study will provide reference for developing feed additives which is safe and non-toxic to cows and their milk.

Identification of SNPs in Bovine SLC27A1 Gene and Its Effects on Milk Production Traits in Chinese Holstein Cattle

[Objective] This study discussed the SNPs of SLC27A1 gene and its relationship with milk production traits in Chinese Holstein Cattle in order to find the SNP site which had significant effect on milk production traits in Chinese Holstein Cattle.[Method] DNA was extracted from the bleed of 48 Chinese Holstein Cattle selected according to phenotypic character and mixed into DNA pool for SNPs detection by polymerase chain reaction-single strand conformation polymorphism（PCR-SSCP）and cloning sequencing.Then different genotypes were detected in other 231 Chinese Holstein Cattle by PCR-RFLP.The association between genotype and production traits was assessed by GLM procedure,SAS version 8.02.[Result] There were T112C in exon3 and G64A loci in 3＇UTR,among them the T112C in exon3 was synonymous mutation.There were 3 genotypes TT,TC and CC in T112C locus and 3 genotypes GG,GA and AA in G64A locus.The population was at Hardy-Weinberg equilibration.Cows with genotype CC had significantly highest milk yield than those with genotype TC（P0.01）,and there were no significant differences among the 3 genotypes on milk protein percent and milk fat percent（P0.05）,but the tendency of CC TC TT on milk protein percent and the tendency of TT TC CC on milk fat percent were showed.There was no significant difference among the 3 genotypes of G64A loci on milk yield,milk protein percent and milk fat percent（P0.05）,but the tendency of GA GG AA on milk yield and the tendency of AA GG GA both on milk protein percent and milk fat percent were showed.[Conclusion] There was certain relation between the T112C locus and milk yield traits;It may improve milk yield to raise the frequency of genotype CC;SLC27A1 gene could be a useful candidate gene in selection program on milk yield traits in Chinese Holstein Cattle,which provided a theoretical basis for the marker-assisted breeding and further study of SLC27A1 gene.

Simultaneous Determination of Melamine, Ammelide, Ammeline, and Cyanuric Acid in Milk and Milk Products by Gas Chromatography-tandem Mass Spectrometry

Objective To develop an analytical method for simultaneously qualitative and quantitative determination of melamine and triazine-related by-products including ammelide, ammeline, and cyanuric acid in milk and milk products by gas chromatography- tandem mass spectrometry （GC-MS/MS）. Methods Melamine and triazine-related by-products namely ammelide, ammeline and cyanuric acid in the samples were extracted in a solvent mixture of diethylamine, water, and acetonitrile （10：40：50, V/V/V）. After centrifugation, an aliquot of the supernatant was evaporated to dryness under a gentle stream of nitrogen gas, and then melamine and triazine-related by-products were derivatized using BSTFA with 1% TMCS. The derivatives of melamine and its analogues were determined by gas chromatography/tandem mass spectrometry using multiple reactional monitoring （MRM） with 2, 6-Diamino-4-chloropyrimidine （DACP） being used as an internal standard. Results The linear detectable ranges were from 0.004 mg/kg to 1.6 mg/kg for melamine, ammelide, ammeline, and cyanuric acid with a correlation coefficient no less than 0.999. The recovery rates of the tour compounds in spiked blank milk powder at concentrations 0.5, 1, 2 mg/kg were between 61.4%-117.2%, and the relative standard deviation was no more than 11.5% （n=6）. The detection limits of melamine, ammelide, ammeline and cyanuric acid in milk powder were 0.002 mg/kg with a ratio of signal to noise of 3. Conclusion This GC-MS/MS method for simultaneous determination of melamine, ammelide, ammeline, and cyanuric acid in milk and milk products is sensitive and specific.

Fine Mapping QTLs Affecting Milk Production Traits on BTA6 in Chinese Holstein with SNP Markers

Our previous studies demonstrated that the region around markers BMS470 and BMS1242 on BTA6 showed a linkage to 305-d milk yield and composition traits in the Chinese Holstein population. We herein focused on such narrow region to fine map milk production QTLs with 15 SNPs across 25 Mb with each SNP in 1 Mb within most regions in a Chinese Holstein population with daughter design. 1 449 Holstein cows and 11 sires were genotyped for such SNPs by using TaqMan probe and RFLP assays. Multipoint linkage analysis across family revealed a QTL affecting milk yield between PPARGC1A C4075T and SLC34A2 T1713C. Meanwhile, within family analysis found three milk yield QTLs （two in CR T60984131G-CEP135 C501T and one in PDLIM5 A106C-OPN T3907, a fat yield QTLin UGDH T1670C-CR T60984131G region, and two protein yield QTLs in TBC1D1 G501C-UGDH T1670C and PPARGC1A C4075T-SLC34A2 T1713C, respectively. Associations between aforementioned significant SNP markers and milk production traits were further implemented. We found significant associations of PPARGC1A C4075T, SLC34A2 T1713C with milk yield （P0.05, P0.01, P0.01）, UGDH T1670C, and CR T60984131G with fat yield （P0.01, P0.01）, and PPARGC1A C4075T, SLC34A2 T1713C, UGDH T1670C and OPN T3907 with protein yield （P0.01, P0.01, P0.01, P0.01）. Our findings implied that QTLs affecting milk production traits on BTA6 were pleictropism or multigenic effect and PPARGC1A and OPN may be the causal mutations behind milk production QTLs on BTA6 in the Chinese Holstein population.

Effect of dietary phosphorus content on milk production and phosphorus excretion in dairy cows

Background：Phosphorus（P） supplementation is costly and can result in excess P excretion.This study investigated the effects of reducing dietary P on milk production and P excretion in dairy cows over a full lactation.Method：Forty-five multiparous Holstein dairy cows were divided into 15 blocks according to expected calving date and previous milk yield,and assigned randomly to one of the three dietary treatments：0.37,0.47,and 0.57%P（DM basis）;these P levels represent the NRC recommendations,Chinese recommendations,and the amount of dietary P commonly fed by Chinese dairy farmers,respectively.Average daily feed intake was calculated from monthly data on feed offered and refused.Milk yields of individual cows were recorded weekly,and milk samples were taken for analysis of protein,fat,solids-not-fat,lactose,and somatic cell count.Blood samples were collected on days-6,-3,0,3,6 relative to calving,and then monthly throughout lactation,and analyzed for P and Ca concentrations.Spot samples of feces and urine were collected for 3 consecutive d during weeks 12,24,and 36,and P concentrations were analyzed.Reproduction and health data were recorded.Results：Dietary P did not affect dry matter intake or milk yield（P〉 0.10）.Milk fat content was slightly higher in cows fed 0.37%P than in cows fed 0.47%P（P = 0.05）.Serum concentrations of P and Ca did not reflect dietary P content（P〉 0.10）.Fecal and urinary P both declined linearly（P〈 0.05） as dietary P decreased from 0.57 to0.37%.Fecal P content was 25%less when dietary P was 0.37%compared to 0.57%.Health events and reproductive performance were not associated with dietary P content（P〉 0.05）.Conclusions：Lowering dietary P from 0.57 to 0.37%did not negatively affect milk production,but did significantly reduce P excretion into environment.

A Capra hircus chromosome 19 locus linked to milk production influences mammary conformation

Background:Economically important milk production traits including milk volume,milk fat and protein yield vary considerably across dairy goats in New Zealand.A significant portion of the variation is attributable to genetic variation.Discovery of genetic markers linked to milk production traits can be utilised to drive selection of highperformance animals.A previously reported genome wide association study across dairy goats in New Zealand identified a quantitative trait locus(QTL)located on chromosome 19.The most significantly associated single nucleotide polymorphism(SNP)marker for this locus is located at position 26,610,610(SNP marker rs268292132).This locus is associated with multiple milk production traits including fat,protein and volume.The predicted effect of selection for the beneficial haplotype would result in an average production increase of 2.2 kg fat,1.9 kg protein and 73.6 kg milk yield.An outstanding question was whether selection for the beneficial allele would co-select for any negative pleiotropic effects.An adverse relationship between milk production and udder health traits has been reported at this locus.Therefore,a genome wide association study was undertaken looking for loci associated with udder traits.Results:The QTL and production associated marker rs268292132 was identified in this study to also be associated with several goat udder traits including udder depth(UD),fore udder attachment(FUA)and rear udder attachment(RUA).Our study replicates the negative relationship between production and udder traits with the high production allele at position 19:26,610,610(SNP marker rs268292132)associated with an adverse change in UD,FUA and RUA.Conclusions:Our study has confirmed the negative relationship between udder traits and production traits in the NZ goat population.We have found that the frequency of the high production allele is relatively high in the NZ goat population,indicating that its effect on udder conformation is not significantly detrimental on animal health.It will however be important to monitor udder conformation as the chromosome 19 locus is progressively implemented for marker assisted selection.It will also be of interest to determine if the gene underlying the production QTL has a direct effect on mammary gland morphology or whether the changes observed are a consequence of the increased milk volume.

Appraisement on Contributive Ratio of Scientific and Technical Progresses in Milk Productive Enterprises by Model C^2GS^2

Scientific and technical progress has been the driving forces of enterprises development.Milk productive enterprises are developing faster and growing better.It is very important to measure the contributive ratio of scientific and technical progress in milk productive enterprises.And the appraisement could help to develop milk productive enterprises.The model C^2GS^2 was established to appraise the contributive ratio of scientific and technical progress in milk productive enterprises in the research.And the appraisement on the contributive ratio of scientific and technical progress in milk productive enterprises was made by the model.In the results of appraisement,science and technology play a main role in milk productive enterprises.It is shown that our milk productive enterprises are developed by scientific and technical progress while not by input of productive factors.

Fabrication and evaluation of a portable and reproducible quartz crystal microbalance immunochip for label-free detection ofβ-lactoglobulin allergen in milk products

In this study,a label-free,portable and reproducible immunochip based on quartz crystal microbalance(QCM)was developed for the qualitative detection ofβ-lactoglobulin(β-LG),an allergen,in milk products.Experimental parameters in the fabrication and regeneration procedure such as pH of the coupling microenvironment,amount of anti-β-LG antibody and regeneration reagent were optimized in detail.Under optimal conditions,the proposed QCM immunochip exhibited good recognition of β-LG,with a calibration curve of ΔF=12.877 C_(β-LG)^(0.4809)(R^(2)=0.9982)and limit of detection of 0.04μg/mL.Additionally,this portable QCM immunochip had good stability,high specificity,and no obvious cross-reaction to three other milk proteins(α-casein,α-lactalbumin,and lactoferrin).It could compete a qualitative measurement within5 min,and could be reused at least ten times.In the β-LG analysis of actual milk samples,the developed QCM immunochip yielded reliable and accurate results,which correlated strongly with those from the standard HPLC method(R^(2)=0.9969).Thus,the portable,stable,and reproducible QCM immunochip developed in this study allowed the rapid,cost-effectively and sensitively measure theβ-LG in milk products.

Production Systems, Genetic Diversity and Genes Associated with Prolificacy and Milk Production in Indigenous Goats of Sub-Saharan Africa: A Review

Goats are one of the oldest domesticated animal species widely distributed in the world playing an important role in the food production system in Sub-Saharan African Region (SSAR). Due to their multiple uses (milk production, meat, fiber and hides) and adaptation aptitudes to ecological conditions, goats produce and contribute positively to farmers’ socio-economy status in various production systems. This review aimed at giving a summary overview on the goat’s production systems characteristics, the genetic diversity and the candidate genes affecting reproductive and milk production performances in goat breeds in SSAR. It has been observed that traditional livestock production system with communal grazing system is the most used in goat keeping in SSAR. The geographical locations play an important role in the relationships between goat’s distributions in the region. At the same time, goats might have been differentiated and isolated one to others due to the wide geographic range, the diversify climate and the topography in the region. Among the six worldwide known haplogroups of goat (A, B, C, D, G and F), haplogroup A is the most representative in SSAR. However, haplogroup G and B can be found in some goat populations in some countries in east (Kenya and Ethiopia) and south parts of Africa. This review reveals that little is known on the candidate genes associated with prolificacy and milk production traits in indigenous goat breeds in the region. That observation suggests the importance of assessing candidate genes associated with economic traits in the populations of goat in SSAR.

Effects of Feeding Siamese neem leaves and Zanthoxylum Pods, on Dry Matter Intake, Dry Matter Digestibility, Milk Production and Composition in Thai Holstein Dairy Cows, Fed Rice Straw as Fiber Source

The plant secondary metabolites （PSM） are highly sought compounds for use as an alternative to conventionally used feed additives in animal production these days; Siamese neem leaf （Azadirachta indica A. Juss. var. siamenses Valeton） and Zanthoxylum pods （Zanthoxylum piperatum） are known to contain numerous such compounds.The objectives of this study were to determine effects of feeding Siamese neem leaf and Zanthoxylum pods as feed additives on dry matter intake （DMI）, dry matter digestibility （DMD） and milk production and milk composition. Lactating Thai Holstein cows （n = 8） were arranged in two replicates of 4 x 4 Latin square designs, housed in individual stall, treatments consisted of Siamese neem 0.5 and 1.5 g kgl dry matter （DM）, ZanthoxylumO. 1 and 0.5 g kg1 DM added to the total mixed ration （TMR）. TMRand drinking water were provided ad lib. There were no significant differences （P 〉 0.05） in DMI and crude protein （CP）, acid detergent fiber （ADF）, neutral detergent fiber （NDF） digestibility, milk production and composition among the treatments.However, significant difference （P 〈 0.05） was observed in dry matter （DM） and ether extract （EE） digestibility. Though statistically non-significant, Zanthoxylum at higher dose level tended to show low DMI （14.85 kg） in cows, while promotingmarginally higher milk （14.18 kg） production as compared with lower dose levelwhere DMI and milk production were 16.14 kg and 13.83 kg.This indicated that Zanthoxylum has a potential to improve feed digestion in dairy cows when used as additives.

<i>Aflatoxin</i>M1 (<i>Aspergillus parasiticus, flavus</i>) Occurrences in Milk and Milk Products and Its Possible Health Effects

Aflatoxin M1 (AFM1) occurrence in milk and milk products has been a major concern among food scientists over the past three decades owing to its possible health risk in humans. The well-documented AFM1 associated adverse health outcomes include hepatocarcinogens, mutagens genotoxins, mutagenicity, and teratogen. The paper reviews the occurrence of AFM1 in milk, milk products, and human milk in developing and developed countries, with its safety standards of regulation. The health associated risks with AFM1 are the important methods used in detecting and reducing AFM1 in milk and other milk products are presented.

Consumers＇ Preferences for Quality and Safety Attributes of Milk Products in Niger： A Best-Worst Scaling Approach

The overall objective of this research was to determine consumers＇ preferences for quality and safety attributes of milk products using advances in the best-worst scaling approach. A list of 16 quality and safety attributes of milk products based on previous studies was compiled and used in this study. The balanced incomplete block design technique was used to build the questionnaire administered to respondents in the data collection. The multinomial mixed logit was employed to analyze the data. Results suggest that nutritive value, shelf life, availability, purity and safety are the most important attributes of milk product; while origin, fat content, food miles, packaging and handling convenience are the least importance attributes of milk products to consumers The study concludes that demand for dairy products can be significantly stimulated in the study area when these most important attributes have been considered by producers, processors and marketers.

Economical Analysis of Milk Production in the Farms of Siedlce Region

Last years the most profitable line of activity in agriculture is considered with milk production. The-effectiveness of this project depends primarily on the direct costs and the obtained of purchase price. Therefore the aim of this work was to analyze the financial results of dairy farms in the east part of Mazovia region. Completing the research in 2010, to the owners of 36 farms were sent a questionnaire containing 18 questions. The obtained data were used to characterize the various research facilities. And then the whole population was devoted on the 6 production groups, depend on the number of physical units of dairy cows. Moreover, based on survey data, an analysis of the profitability of milk production was done. It was the following economic values： direct costs, revenue, gross margin and the index of production profitability. Also the statistical analysis by calculating the Pearson linear correlation coefficient （r） and coefficient of determination （R2） was done. The study showed that the highest annual yield of milk from a cow at the level of 7500 kg, reached the farmers with the area of l 9.7 ha of with the density of 1.82 BFU/ha and with 8 years of cow utilization. Respondents from this group also received the highest value of effectiveness index （184.60%）. In addition, the performed regression analysis showed significant positive correlation between the effectiveness index and the surface agricultural lands occurring in the farms, density of agricultural lands, and efficiency from a cow and the price of milk.

Antibiotic residues in milk and milk products:A momentous challenge for the pharmaceutical industry and medicine

Dairy products are nutritious food items that contain various essential nutrients,however,it has been proven that residual antibiotics have contaminated such products.These residues can cause several side effects on human health.They increase antimicrobial resistance against several threatening microorganisms,as well as significant growth in allergenic reactions.Various methods,including heat treatments,have been applied to alleviate and reduce the effect of antibiotic residue level in milk and milk products.Changes in drug levels were not sig-nificantly remarkable,obliging researchers to find new approaches to prevent or reduce their risk and limit their complications on human health.

Anhui Huainan Milk Product Company

The Yiyi brand milk series are theleading products of the Anhui Huainan MilkProduct Company. The predecessor of thecompany was a state-owned farm, whichwas set up in the 1950s, with a total area of2,734 hectares. The company has a completestructure covering agriculture, forestry,animal husbandry, fishery, industry andcommerce. Its agriculture has full waterconservancy facilities and an irrigationsystem for strong resistance to naturaldisasters. Its scientific and technologicalforces are strong too. Since 1989, its per unityield and total output have been listed on thetop level along the basin of Huai River. Animal husbandry. There are threelivestock farms with 3,000 head of milkcows, one third of the Anhui provincial total. Industry has some processing

Milk Production in Tibet

This paper describes milk production and livestock production in Tibet. Some information of market demand has also been presented. There has been very little information published in Tibetan journals on production and nutrition of cattle. This review provides a brief introduction to feeding systems and feeding resources. Many studies on milk production have been done in isolation, and do not go beyond the basic and practical level. Compared with dairy cattle research in other parts of China, large gaps in knowledge still exist in cattle production science, particularly related to nutrition, and systems approaches for the development of a dairy industry.

Amino acids and mammary gland development:nutritional implications for milk production and neonatal growth

Milk is synthesized by mammary epithelial cells of lactating mammals. The synthetic capacity of the mammary gland depends largely on the number and efficiency of functional mammary epithelial cells. Structural development of the mammary gland occurs during fetal growth, prepubertal and post-pubertal periods, pregnancy, and lactation under the control of various hormones （particularly estrogen, growth hormone, insulin-like growth factor-I, progesterone, placental lactogen, and prolactin） in a species- and stage-dependent manner. Milk is essential for the growth, development, and health of neonates. Amino acids （AA）, present in both free and peptide-bound forms, are the most abundant organic nutrients in the milk of farm animals. Uptake of AA from the arterial blood of the lactating dam is the ultimate source of proteins （primarily 13-casein and a-lactalbumin） and bioactive nitrogenous metabolites in milk. Results of recent studies indicate extensive catabolism of branched-chain AA （leucine, isoleucine and valine） and arginine to synthesize glutamate, glutamine, alanine, aspartate, asparagine, proline, and polyamines. The formation of polypeptides from AA is regulated not only by hormones （e.g., prolactin, insulin and glucocorticoids） and the rate of blood flow across the lactating mammary gland, but also by concentrations of AA, lipids, glucose, vitamins and minerals in the maternal plasma, as well as the activation of the mechanistic （mammalian） target rapamycin signaling by certain AA （e.g., arginine, branched-chain AA, and glutamine）. Knowledge of AA utilization （including metabolism） by mammary epithelial cells will enhance our fundamental understanding of lactation biology and has important implications for improving the efficiency of livestock production worldwide.

Milk production and composition and metabolic alterations in the mammary gland of heat-stressed lactating dairy cows

This experiment was conducted to investigate the effects of heat stress(HS) on the feed intake, milk production and composition and metabolic alterations in the mammary gland of dairy cows. Twenty Holstein cows were randomly assigned to one of two treatments according to a completely randomized design. Half of the cows were allocated to the HS group in August(summer season), and the other half were assigned to the HS-free group in November(autumn season). HS reduced(P<0.01) dry matter intake(DMI), milk yield, milk protein and milk urea nitrogen(MUN) of cows compared with HSfree control, but increased(P<0.01) milk somatic cell counts(SCC). We determined the HS-induced metabolic alterations and the relevant mechanisms in dairy cows using liquid chromatography mass spectrometry combined with multivariate analyses. Thirty-four metabolites were identified as potential biomarkers for the diagnosis of HS in dairy cows. Ten of these metabolites, glucose, lactate, pyruvate, lactose, β-hydroxybutyrate, citric acid, α-ketoglutarate, urea, creatine, and orotic acid, had high sensitivity and specificity for HS diagnoses, and seven metabolites were also identified as potential biomarkers of HS in plasma, milk, and liver. These substances are involved in glycolysis, lactose, ketone, tricarboxylic acid(TCA), amino acid and nucleotide metabolism, indicating that HS mainly affects lactose, energy and nucleotide metabolism in the mammary gland of lactating dairy cows. This study suggested that HS might affect milk production and composition by affecting the feed intake and substance metabolisms in the mammary gland tissue of lactating dairy cows.

Identification of single nucleotide polymorphisms of PIK3R1 and DUSP1 genes and their genetic associations with milk production traits in dairy cows

Background:Previously,phosphoinositide-3-kinase regulatory subunit 1(PIK3R1)and dual specificity phosphatase 1(DUSP1)were identified as promising candidate genes for milk production traits due to their being differentially expressed between the dry period and the peak of lactation in livers of dairy cows.Hence,in this study,the single nucleotide polymorphisms(SNPs)of PIK3R1 and DUSP1 genes were identified and their genetic associations with milk yield,fat yield,fat percentage,protein yield,and protein percentage,were investigated using 1067 Chinese Holstein cows from 40 sire families.Results:By re-sequencing the entire coding region and 2000 bp of the 5′and 3′flanking regions of the two genes,one SNP in the 5′untranslated region(UTR),three in the 3′UTR,and two in the 3′flanking region of PIK3R1 were identified,and one in the 5′flanking region,one in the 3′UTR,and two in the 3′flanking region of DUSP1 were found.Subsequent single-locus association analyses showed that five SNPs in PIK3 R1,rs42590258,rs210389799,rs208819656,rs41255622,rs133655926,and rs211408208,and four SNPs in DUSP1,rs207593520,rs208460068,rs209154772,and rs210000760,were significantly associated with milk,fat and protein yields in the first or second lactation(P values≤0.0001 and 0.0461).In addition,by the Haploview 4.2 software,the six and four SNPs in PIK3R1 and DUSP1 respectively formed one haplotype block,and the haplotype-based association analyses showed significant associations between their haplotype combinations and the milk traits in both two lactations(P values≤0.0001 and 0.0364).One SNP,rs207593520(T/G),was predicted to alter the transcription factor binding sites(TFBSs)in the 5′flanking region of DUSP1.Further,the dual-luciferase assay showed that the transcription activity of allele T in rs207593520 was significantly higher than that of allele G,suggesting the activation of transcriptional activity of DUSP1 gene by allele T of rs207593520.Thus,the rs207593520 SNP was highlighted as a potential causal mutation that should be further verified.Conclusions:We demonstrated novel and significant genetic effects of the PIK3R1 and DUSP1 genes on milk production traits in dairy cows,and our findings provide information for use in dairy cattle breeding.

Association between growth rates, age at first calving and subsequent fertility, milk production and survival in Holstein-Friesian heifers

Age at first calving (AFC) affects the profitability of dairy enterprises. This study examined the relationships between AFC and subsequent fertility, milk production and survival up to third calving in UK Holstein-Friesian heifers;Study 1 comprised 134 consecutively born heifers from the same herd (AFC 764 ± 8 days) and Study 2 contained 445 heifers born on 17 farms (AFC 796 ± 6 days). Growth rates and fertility during rearing were monitored and animals were subsequently divided into four AFC groups for analysis: <23 months, 23 - 25 months, 26 - 30 months and >30 months. The actual AFC reflected both growth rate and heifer fertility, with later calving heifers already lighter by 6 months of age. The proportion conceiving to first service was highest (93% and 84% for Studies 1 and 2, respectively) for the youngest AFC group. Fertility in the first lactation was best in cows calving at 23 - 25 months and worst in the oldest AFC group. Milk production parameters in the first and second lactations were broadly similar between AFC groups but significantly more heifers with an AFC < 26 months calved for a third time. These younger calving animals therefore achieved more days in milk over 5 years, with >44% of their days alive spent in milk production compared with only 18% - 40% in cows calving at ≥26 months. Hence cows with an AFC < 26 months produced the most milk in their first 5 years of life. These results indicate that an AFC of 0.75 kg/d up to 15 months and good heifer fertility and resulted in the best subsequent performance.