Dairy Cow Breeding Research Articles

A novel SNP of the ATP1A1 gene is associated with heat tolerance traits in dairy cows

PCR low ionic strength single-strand conformation polymorphism (PCR-LIS-SSCP) and DNA sequencing methods were used to analyze the polymorphisms within the coding region of bovine ATP1A1 gene. A novel C/A mutation was identified at the nucleotide position 2789 of the ATP1A1 mRNA, but it was silent with respect to the amino acid sequence of the protein. The LIS-SSCP banding pattern could be divided into three kinds of genotypes, named CC, CA, and AA. Also, the association of the novel SNP of ATP1A1 gene with heat tolerance traits was studied, we found that the individuals with genotype CC showed significantly higher heat resistance than those of genotype CA (P<0.05). Further, the mRNA levels of ATP1A1 gene in lymphocytes of peripheral blood in dairy cows among various temperature groups and genotypes were analyzed by using real-time RT-PCR. Results showed that the expression of ATP1A1 mRNA was highest in heat-stressed cows with CC genotype among the three genotypes (P<0.01), and the ATP1A1 mRNA level at temperature 32.5°C was higher than that at optimal temperature 12.5°C in dairy cows (P<0.01). Simultaneity, the plasma potassium (K+, mmol/l) and sodium (Na+, mmol/l) declined when the temperature dropped (P<0.05). Our findings implied that the novel SNP here could be a potential genetic marker for anti-heat stress trait in dairy cow breeding.

The analysis of relationships between chemical composition, physical, technological and health indicators and freezing point in raw cow milk

The milk freezing point (MFP) is used for the control of milk food chain quality especially for possible adulteration with water. A crucial issue is the acceptance of the legislative discrimination limit (RLDL) of MFP for standard quality. The aim was to explain the relations between MFP and spectrum of milk indicators (MI) and possible impacts of MFP on technological milk properties. 76 bulk milk samples (BMS) from Holstein (1, &lt;I&gt;n&lt;/I&gt; = 36) and Czech Fleckvieh (2, &lt;I&gt;n&lt;/I&gt; = 40) cattle were analyzed for 48 MIs. The dairy cows were relatively healthy as for the occurrence of production disorders. BMSs were taken from February to June. Extraneous water was excluded. 44 MIs were correlated with the MFP. The relations were not regularly consistent between breeds. Milk yield was connected with MFP (&lt;I&gt;r&lt;/I&gt; = 0.40; &lt;I&gt;P&lt;/I&gt; &lt; 0.05). It shows the necessity of modification of RLDL of MFP in dependence on dairy cow breeding. Further relations (&lt;I&gt;P&lt;/I&gt; ≤ 0.05) were among MFP and: total milk solids (&lt;I&gt;r&lt;/I&gt; = –0.50); solids-non-fat (–0.33); crude protein (–0.32); true protein (–0.43); whey protein (–0.47); milk fat (–0.46); electrical conductivity (–0.35); lactose (–0.35); somatic cell count (–0.36); fat/protein ratio (–0.36); milk citric acid (0.47); Na (–0.34). The poor relations (&lt;I&gt;P&lt;/I&gt; &gt; 0.05) were among MFP and casein, milk urea and acetone. The cheese-making indicators were not affected by MFP. The MFP was related to milk fermentation indicators (&lt;I&gt;r&lt;/I&gt; = from –0.34 to –0.39, &lt;I&gt;P&lt;/I&gt; &lt; 0.05). It is important for the control of milk food chain quality by MFP and for the estimation of its RLDL.

Environmentalimpactevaluationofinnovation in traditionalfoodproductionlines. Part II: casestudies

1 Nat. Inst. of Chemistry, Lab. for Environmental Sciences and Engineering, Hajdrihova 19, SI-1001 Ljubljana, Slovenia, e-mail: gasan.osojnik@ki.si 2 Univ. of Ljubljana, Biotechnical Fac., Dept. of Animal Science, Groblje 3, SI-1230 Domžale, Slovenia, Prof, Pd.D., M.Sc., e-mail: romana.marinsek@bf.uni-lj.si Environmental impact evaluation of innovation in traditional food production lines. Part II: case studies Case studies of environmental impact assessment were performed for production steps of three traditional food production lines (dairy cow breeding, dry-cured ham, Brassica sp. growing) in order to examine the previously constructed methodological framework. The emission inventory was obtained on the basis of initial experimental data. The emissions were aggregated accordingly for the characterization to environmental impact categories. The contribution of studied process steps to several environmental impact categories was assessed (greenhouse gas emission, acidification potential, eutrophication potential, use of resources and use of agricultural land).

Faba beans (Vicia faba) in dairy cow diet: effect on milk production and quality

The use of alternative plant proteins in place of the soybean meal protein in diets for farmed animals aims to reduce the extra-EU soybean import and partially substitute the GMO in the food chain. Among the possible alternatives, the heat-processed (flaked) faba beans appears interesting for dairy cow diet. Two consecutive experiments were carried out to test flaked faba beans as a partial substitute for soybean meal in the diet of Reggiana breed dairy cows producing milk for Parmigiano-Reggiano cheese-making. In both experiments a “Control” concentrate (12% soybean meal, no faba beans) was compared with a “Faba” concentrate (7.5% soybean meal and 10% flaked faba beans). Forages fed to animals were hay (mixed grass and alfalfa) plus mixed grass in experiment 1, hay only in experiment 2. Milk yield and quality and the characteristics of grab faecal samples as empirical indicators of digestibility, were similar between feeding groups. The milk urea content was slightly lower in the “Faba” group, particularly in experiment 2 (“Control” vs “Faba”: 34.6 vs 32.9 mg/dL in experiment 1, P<0.1; 27.4 vs 23.4 mg/dL in experiment 2, P<0.01); the plasma urea content in experiment 2 confirmed the trend observed in milk (3.9 vs 3.0 mmol/L, P<0.01). The inclusion of faba beans, within the allowed limit of the Parmigiano-Reggiano Consortium for diet formulation, could represent a feasible opportunity for a partial substitution of soybean meal.

Season and physiological status affects the circadian body temperature rhythm of dairy cows

The circadian body (vaginal) temperature rhythm was measured in 36 dairy cows: Holstein–Friesian (HF, n = 12), Jersey (J, n = 12) and their crossbreed, Holstein–Friesian × Jersey (HF × J, n = 12) at six different periods (5-7 days in duration) during the year that could potentially be a seasonal and physiological stressor. These were a) early winter (late pregnancy), (b) early spring (early lactation), (c) late spring (before mating at mid-lactation), (d) early summer (after mating at mid-lactation), (e) late summer (late lactation, early pregnancy) and, (f) early autumn (drying-off at the end of lactation, mid-pregnancy). Live weight and body condition score was recorded on the first day of each measurement period. Live weight differed ( P < 0.001) with breed with HF cows heaviest and J cows lightest (HF: 525 ± 51, HF × J: 456 ± 56, J: 401 ± 30 kg). HF cows tended ( P = 0.099) to have a higher body condition than either J or HF × J cows although the overall change in body condition during the experiment was similar ( P = 0.961) amongst breeds. The circadian body temperature rhythm differed markedly between each measurement period, being flatter and having a less prominent morning nadir and afternoon peak during early winter compared to spring and summer. The timing of peak body temperature was 4-5 h earlier in early autumn in HF and HF × J cows relative to J cows. There was no breed difference ( P ≥ 0.162) in daily mean body temperature except for a tendency ( P = 0.075) for mean body temperature to be moderately higher in J cows (38.5 °C) during late summer compared to HF and HF × J cows (38.4 °C), primarily due to an increase ( P = 0.001) in daily minimum body temperature (38.0 vs. 37.8 °C). The daily range of oscillation (maximum–minimum) in the body temperature rhythm was highest during late summer, particularly in HF and HF × J cows. Minimum body temperature was also higher ( P = 0.033) for J cows than HF and HF × J cows during early autumn (37.9 vs. 37.8 °C). In conclusion, season and physiological status of cattle had a profound effect on the circadian body temperature rhythm but there was little difference between the breeds of dairy cows studied.

The effect of dairy cow breed and cross on milk production and fatty acid composition under grazing conditions

Dietary intake of omega-3 polyunsaturated fatty acids (n-3 PUFA) and conjugated linoleic acid (CLA) has been recognized as having potential positive effects on human health (Lock and Bauman, 2004). Furthermore, alteration of the fatty acid (FA) composition of milk through targeted manipulation of dairy cow diets can be achieved (Dewhurst et al., 2006). Although breed effects on the FA composition of milk have previously been reported (Kelsey et al., 2003), most work to-date has been conducted under high input TMR based systems. Furthermore, little is known on the effects of heterosis on concentrations of FA in milk. The objective of this study was to examine whether differences in milk FA concentration exist between two contrasting breeds of dairy cow and their F1hybrid managed under a grazing based production system.

Winter feeding systems and dairy cow breed have an impact on milk composition and flavour of two Protected Designation of Origin French cheeses

This study investigates the effects of two feeding systems and two dairy cow breeds on milk yield and composition, physical and sensorial properties of Camembert and Pont-l’Evêque cheeses. The experiment consisted of a 2 × 2 factorial arrangement of treatments. A low energy grass diet with only 15% of concentrate (LowGS) was compared with a high-energy maize silage diet with 30% concentrate (HighMS). Thirty-four Holstein (Ho) and 34 Normande (No) cows in early lactation were assigned to one of two feeding systems for a 6-week period. Cows on the LowGS feeding system had lower milk yield, fat and protein content. In both feeding systems, No cows had lower milk yields but higher milk protein contents than Ho cows. The LowGS feeding system altered milk fatty acid (FA) composition by reducing saturated FA. Breed had only a small impact on milk FA. Concerning milk coagulating properties, only the firmness was reduced by the LowGS feeding and the Ho breed. The effects of breed and feeding system on the protein content of cheeses were more marked in Camembert cheese than in Pont-l’Evêque cheese. However, the Camembert cheese from Ho-LowGS was, in fact, characterized especially by lower protein content. LowGS feeding system and No breed produced more yellow cheeses. Feeding systems had limited effects on the firmness of Camembert and Pont-l’Evêque cheeses measured by penetrometry. In sensory analysis, Ho breed and LowGS feeding produced a Camembert cheese with a more melting texture in the mouth due to the increase of spreadability index and of proteolysis. The type of cheese also had an influence: the effects were more important on Camembert cheese than on Pont-l’Evêque cheese. Only the Ho-LowGS treatment produced a very specific Camembert cheese different from the others. The feeding systems and breed of dairy cow have no determinant effect on PDO (protected designation of origin) Camembert and Pont-l’Evêque cheeses, especially regarding taste. In this kind of trial, despite the effects of feeding systems and breed on milk composition, the role of cheese ripening and microbiology appears to be of considerable importance.

Pea (Pisum sativum) in dairy cow diet: effect on milk production and quality

The use of alternative plant protein in place of soybean meal protein in diets for farmed animals aims to reduce the extra-EU soybean import and partially substitute GMO in the food chain. Among the possible alternatives, the heat-processed (flaked) pea appears interesting in dairy cow diets. Two consecutive experiments were carried out to test flaked peas as a partial substitute for soybean meal in the diet of Reggiana breed dairy cows producing milk for Parmigiano-Reggiano cheese-making. In both experiments a “Control” concentrate (8.3% soybean meal) was compared to a “Pea” concentrate (5% soybean meal and 15% flaked peas). Forages fed to animals included mixed grass hay and alfalfa hay in experiment 1, and hay (mixed grass and alfalfa) plus mixed grass in experiment 2. Milk yield and quality, and the characteristics of grab faecal samples, examined to get some empirical indicators of digestibility, were similar between feeding groups. Compositional changes (crude protein and solubility) in forages used as common base in the diets of both experiments had a slight effect on milk and plasma urea contents. There was a tendency for a higher milk urea content in the “Pea” group (32.3 vs 30.1mg/dl in experiment 1, P<0.1; 30.2 vs 28.0mg/dl in experiment 2, P<0.1). The plasma urea content was different only in experiment 2 (4.9 vs 5.6mmol/l, respectively for “Control” and “Pea” groups; P<0.05). The inclusion of the heat-processed pea within the allowed limit of the Parmigiano-Reggiano Consortium for diet formulation could represent a feasible opportunity for a partial substitution of soybean meal.

Faba bean in dairy cow diet: effect on milk production and quality

Two consecutive trials were carried out to test flaked faba beans as a partial substitute for soybean meal (SBM) in the diet of Reggiana breed dairy cows. In both trials a “Control” concentrate (12% dehulled SBM) was compared to a “Faba” concentrate (7.5% dehulled SBM; 10% flaked faba beans). Forages fed to animals included hay (mixed grass and alfalfa) plus green mixed grass in trial 1, hay only in trial 2. Concentrate intake, faecal scores, milk yield and quality were similar between feeding groups. The milk urea content was lower in the “Faba” group (“Control” vs. “Faba”: 34.6 vs. 32.9mg/dl in trial 1, P<0.1; 27.4 vs. 23.4mg/dl in trial 2, P<0.01). The plasma urea was different only in trial 2 (“Control” vs. “Faba”: 3.9 vs. 3.0mmol/l, P<0.01). The inclusion of faba beans within the allowed limit of the Parmigiano-Reggiano Consortium for diet formulation could represent a feasible opportunity for a partial substitution of SBM.

Yield and Nutritive Value of ‘Spring Green’ Festulolium and ‘Jesup’ Endophyte‐Free Tall Fescue Stockpiled for Winter Pasture

Pasture‐based dairies in the Midwest have a difficult time providing high‐quality pasture during winter. Little is known about the yield and nutritive value of festulolium when stockpiled for winter grazing compared to tall fescue. In this study, the yield and nutritive value of ‘Jesup’ endophyte‐free tall fescue [Schedonorus phoenix (Scop.) Holub.] and ‘Spring Green’ festulolium [Festulolium loliaceum (Hudson) P.V. Fournier] were evaluated monthly from November to March over three years. The research was conducted near Mt. Vernon, MO, on a Gerald silt loam (fine, mixed, active, mesic Aeric Fragiaqualf). In two of the three years, stockpiled tall fescue out‐yielded festulolium by as much as 930 kg ha−1 Both tall fescue and festulolium yields decreased over winter by approximately the same percentage; losses from November to March ranged from 32 to &gt;75%. The nutritive value of stockpiled festulolium was consistently greater than stockpiled tall fescue during winter. Both stockpiled festulolium and tall fescue contain sufficient crude protein and total digestible nutrients at one times maintenance to maintain most small breed dairy cows during their dry period but would be severely lacking once lactation started. Despite the greater nutritive value of stockpiled Spring Green festulolium compared to Jesup tall fescue, the low forage yield of festulolium makes its use questionable for pasture‐based dairies.

The effect of breed and housing system on dairy cow feeding and lying behaviour

In Ireland there is growing interest in managing dairy cows on out-wintering pads (OWPs) during the winter, as a low cost alternative to housing indoors. This study investigated feeding and lying behaviour of two breeds of dairy cow (Holstein-Friesian and Norwegian Red) at pasture (PAS) and in winter (WIN) confinement. Cows ( n = 36) were managed as one herd while lactating at PAS, then dried off on entering WIN on 17 November 2005 and assigned to one of the three treatments using a randomised complete block design: (1) indoor matted cubicles [IC], (2) unsheltered OWP [UP] and (3) sheltered OWP [CP] (feed system = concrete feedface). Feeding behaviour was recorded for 1 × 24 h period during PAS and WIN using IGER grazing behaviour recorders. Standing/lying was recorded every 5 min for 2 × 24 h periods at PAS and 1 × 24 h period during WIN using modified voltage dataloggers (Tinytag Plus, Chichester, UK). Although not compared statistically, cows spent more time feeding at PAS (530.7 ± 69.66 min/day) than in any winter confinement system (UP, IC, CP = 453.9 ± 37.36, IC = 462.7 ± 37.31 and CP = 505.9 ± 37.36 min/day). In contrast, cows spent more time lying during the winter period (UP, IC, CP = 11.7 ± 0.45, IC = 10.8 ± 0.39 and CP = 11.0 ± 0.39 h/day) than when at PAS (9.4 h/day). Holstein-Friesian cows had a higher bite rate and fewer mastications while feeding, than Norwegian Red cows ( P < 0.05 for both). Shorter feeding times at WIN were likely primarily due to lower metabolic requirements associated with the dry period, although the higher fibre content of the silage may also have contributed. The increase in ruminating times between PAS and WIN is likely also due to the higher fibre content of silage than grass. Differences in feeding behaviour between breeds may be indicative of reduced motivation to ingest food quickly. This may be an indirect consequence of a selection index that has led to improvements in body condition and self-maintenance. The similarity in lying and feeding times during WIN indicates that during these winter weather conditions the feeding and lying behaviour of cows on unsheltered OWPs was not inhibited compared with sheltered cows.

Characterisation of single nucleotide polymorphisms identified in the bovine lactoferrin gene sequences across a range of dairy cow breeds

The lactoferrin gene sequences of 70 unrelated dairy cows representing six different dairy breeds were investigated for single nucleotide polymorphisms to establish a baseline of polymorphisms that exist within the Irish bovine population. Twenty-nine polymorphisms were identified within a 2.2 kb regulatory region. Nineteen novel polymorphisms were identified and some of these were found within transcription factor binding sites, including GATA-1 and SPI transcription factor sites. Forty-seven polymorphisms were identified within exon sequences with unique polymorphisms that were associated with amino acid substitutions. These included a T/A SNP, identified in a Holstein Friesian animal, which resulted in a valine to aspartic acid substitution (Val89Asp) in the mature lactoferrin protein. Other SNPs of interest were associated with amino acid substitutions in the lactoferricin B peptide sequence and an A/G SNP, identified in a Jersey animal, was associated with a tyrosine to cysteine change (Tyr181Cys). The polymorphisms identified in the promoter region may have implications relating to lactoferrin expression levels in cows and those identified in the coding sequence indicate the existence of protein variants in the Irish bovine population. The data presented in this study emphasises the potential for lactoferrin to serve as a candidate gene to select for mastitis resistance with the aim of improving animal health.

Absence of persistent methane emission differences in three breeds of dairy cows

In the present study, data from an experiment with 10 purebred Holstein, Simmental and Jersey cows each were analysed to test the assumption that there are genetically low methane-producing animals. Methane emission of cows offered forage ad libitum and some concentrate was measured for 3 days in open-circuit respiration chambers in weeks 8, 15, 23, 33 and 41 of lactation. Individual cow data were analysed in five different ways: (i) plotting the trend of methane per unit of dry matter intake (DMI) and milk yield over time; relating measured methane production to estimates derived from equations based on either; (ii) DMI or (iii) nutrient intake; (iv) relating residual feed intake (RFI) to methane emission; and (v) analysis of variance of cow × measurement interactions. The Holstein, Simmental and Jersey cows emitted on average 25, 25 and 26 g methane/kg DMI, respectively. There was no indication of individual cows with persistently low or high methane yield per kg DMI and per kg milk. Measured methane emissions differed from estimated values without a clear pattern, and the relationship between RFI and methane emission of the cows was weak. Finally, analysis of variance failed to show distinct patterns of methane per unit of DMI and milk for individual animals. The apparent lack of persistence of individual animal differences in methane yields suggests that genetic determination of this trait is of minor importance in dairy cows.

Sweating Rates of Dairy Cows and Beef Heifers in Hot Conditions

Sweating rates from heat-stressed dairy cows and beef heifers were measured using a Portable Calorimeter and a Bovine Evaporation Meter designed and fabricated for the studies reported herein. Measurements were taken when cows were in their natural habitat. The focus of the study was to compare sweating rates measured from different breeds of dairy cows and beef heifers, and determine the level of influence of environmental factors (air temperature, relative humidity, solar load, and air velocity) and hair-coat color on sweating rate. The cows were exposed to solar radiation greater than 500 W/m2 (average 833 132 W/m2), average THI was 82.7 1.64 for all studies except for the Nebraska data where the THI was 77.4 4. Air velocity in the sample area was between 0.8 and 1.2 m/s, and body (rectal) temperature was greater than 38.8C (threshold for heat stress). Sweating rates ranged between 189 84.6 and 522 127.7 g/m2-h. Body temperature ranged between 39.3 0.53C and 41.7 0.19C. Differences in sweating rates were statistically significant at P < 0.05 between breeds, between black and white hair coats, and changes in solar load, relative humidity, and air velocity. Wetting the skin surface and increasing air velocity profoundly increased evaporation rate by converting sensible heat to latent heat.

Effect of relocation on locomotion and cleanliness in dairy cows

This study was conducted to determine the effect that relocation to a new free stall barn had on locomotion and cleanliness of two breeds of dairy cows. The original facility before relocation had cows housed in an 8-row free stall barn. Cows were allocated in a new 4-row free stall facility: cows of two breeds (n=22 Holsteins and 22 Jerseys) were intermixed in the northwest section. Locomotion (scale 1-5) and cleanliness were scored (scale 1-4). Holsteins and Jerseys had no difference in locomotion score throughout 12 weeks following relocation. A lactation number by date interaction showed cows in third and greater lactations had significantly higher locomotion scores (more lameness) by day 86. Locomotion scores increased across breeds during the 86-d observation period, suggesting cows became lamer. Jerseys had cleaner lower legs than Holsteins (2.9+/-0.1 v. 3.5+/-0.1, respectively). Lactation number affected lower leg cleanliness, with scores decreasing as lactation number increased (3.4 v. 3.3 v. 2.9+/-0.10 for first, second and third and greater lactations, respectively; P<0.01). All cows were cleaner (lower scores) after relocation, suggesting that the new facility improved hygiene.

Genetics: Breeding dairy cows for a longer lifespan

LivestockVolume 12, Issue 6 p. 46-47 Genetics: Breeding dairy cows for a longer lifespan Marco Winters MSc, Marco Winters MSc DIRECTOR, MDC BREEDING+, MILK DEVELOPMENT COUNCIL, STROUD ROAD, CIRENCESTER. GL7 6JNSearch for more papers by this author Marco Winters MSc, Marco Winters MSc DIRECTOR, MDC BREEDING+, MILK DEVELOPMENT COUNCIL, STROUD ROAD, CIRENCESTER. GL7 6JNSearch for more papers by this author First published: 30 September 2010 https://doi.org/10.1111/j.2044-3870.2007.tb00126.xCitations: 1AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume12, Issue6October 2007Pages 46-47 RelatedInformation

175 TRANSCRIPTOME ANALYSIS OF BOVINE DAY 150 FETAL LIVER AND COTYLEDON REVEALS GENES INVOLVED IN FETAL GROWTH

Major problems in breeding of modern dairy cows include increasing rates of stillbirth and dystocia, associated with elevated costs for veterinary intervention (caesarean section) and loss of production animals (cows and calves). Rates of stillbirth as high as 12% have been reported, primarily caused by fetal overgrowth and increased birth weight. In order to discover molecular markers for selection against stillbirth, we developed a model for the inheritance of fetal growth traits. A Fleckvieh bull segregating for paternal stillbirth was used for insemination of 36 cows that were slaughtered at Day 150 of pregnancy in order to recover and phenotype the fetuses. The mode of inheritance indicated involvement of imprinting. Mapping results suggested an imprinted region on chromosome 9 as candidate for the stillbirth QTL. Due to the complexity of the trait, we opted for a holistic approach that is not restricted to the QTL candidate region but allows identification of genes and networks that influence fetal growth. Transcriptome profiles of liver and cotyledon samples from the fetuses with the highest (n = 10) and the lowest total weight n = 10) were analyzed using Affymetrix Bovine GeneChips (Affymetrix, Inc., Santa Clara, CA, USA). Analysis with the program SAM showed 41 up- and 4 down-regulated genes in liver samples of the heavy-weight group. Most of these genes are involved in immune response. Interestingly, many of these genes are reported to be regulated by vitamin D. Furthermore, vitamin D is closely connected to the IGF1 system and thus the most important fetal growth regulation circuit. Seasonal effects on vitamin D levels could mostly be excluded by the experimental design and did not correlate with growth traits. Most likely, the mRNA levels of our candidate genes were influenced by alterations in the IGF1/vitamin D circuit and did not cause the observed weight differences. The imprinted candidate genes showed no correlation with fetal weight. Gene set enrichment analysis indicated enhanced metabolic activity in the liver of heavy-weight fetuses. Genes from the QTL region showed a clear enrichment in correlation with fetal weight, confirming their involvement in fetal growth. The gene with the best correlation, GHITM (growth hormone inducible transmembrane protein), could give an explanation for the enhanced metabolic activity, as it is reported to function as a metabolic regulator. Simultaneous analysis of the data sets for liver and placenta in a linear model (R-package LIMMA; Smyth 2004 Stat. Applic. Genet. Mol. Biol. 3, art. 3) yielded essentially the same differentially expressed genes for liver and a higher number of differentially expressed genes for placenta (89 up- and 114 down-regulated), with little overlap between the two tissues. This work was supported by Grant BMBF FUGATO-Fertilink.

Breeding dairy cows for the future in New Zealand

A brief history of the breeding of dairy cattle in New Zealand is provided. Dairy farming in New Zealand is unique compared with the majority of dairy systems in the developed world. New Zealand has a dependence on grass-based diets and a strict requirement for a 365-day calving interval. Four main areas are discussed: future traits to evaluate, advances in genetic evaluation technologies, impacts of crossbreeding, and future progeny testing schemes. These areas are not independent, e.g. the trend of increasing numbers of crossbred cattle in the national herd will have major impacts on the design of breeding schemes. It is foreseeable that in the future there will be improvements in the national breeding goal to better reflect on-farm profitability, and in the definition of traits and methods of data capture within the national breeding goal. Methods of selection and genetic evaluation that are currently feasible for a small population will become feasible for large populations as computing power improves. Genetic improvement of cows in New Zealand will continue to be a critical component of the increased economic efficiency achieved on dairy farms in this country.

Heart rate variability in dairy cows—influences of breed and milking system

Heart rate variability parameters in the time, frequency and nonlinear domains were investigated in two breeds of dairy cows (Austrian Simmental and Brown Swiss) milked either in an automatic milking system with partially forced cow traffic or in a herringbone milking parlour. Recordings were made of 24 cows (six of each breed and milking system) during lying, standing idle, and standing being milked, and analysed with linear mixed effects models taking the covariates time of day, live body weight, milk yield, stage of lactation and stage of pregnancy into account. Heart rate and nonlinear deterministic shares were higher, and heart rate variability in the time and frequency domains was lower, later in the day, in cows with higher body weight and in Simmental compared to Brown Swiss cows. Differences in the linear and nonlinear domains during lying indicated an increased level of chronic stress in cows in the automatic milking system with partially forced cow traffic, compared to cows milked in the herringbone milking parlour. No effects of milking system were found during milking, indicating that the stressor in the automatic milking system was not the milking process itself.

Metabolic safety-margins do not differ between cows of high and low genetic merit for milk production.

Three galactopoietic stimuli, frequent milking (4X), bovine somatotrophin (bST) and thyroxine (T4) were used in an additive stair-step design to achieve maximum output (metabolic capacity) in six peak-lactation cows of high genetic merit (HT) and six of low genetic merit (LT). A further six of each merit were untreated controls (HC, LC). Milk yield was increased significantly by 4X, increased further by the combination of 4X and bST and increased further still and significantly by the full combination of 4X, bST and T4. The magnitude of the yield response to the sequence of treatments did not differ significantly between HT and LT. The yield response to 4X and bST was sustainable without significant loss of body weight or body condition score for the 6 weeks during which these stimuli were administered. The response to the full combination, which included T4, was accompanied by significantly elevated heart rate and significant loss of body weight and condition compared with the combination of 4X and bST. As a result, treatments were discontinued, on an individual cow basis, before completion of this 6-week phase. Time on experiment did not differ between HT and LT. The results do not support the commonly held belief that selective breeding of dairy cows for high milk production has rendered them markedly more susceptible to metabolic disturbances.