Effects of dry period energy intake on insulin resistance, metabolic adaptation, and production responses in transition dairy cows on grass silage-based diets.

High energy intake in the dry period has reportedly had adverse effects on mobilization of body reserves, dry matter intake, and productivity of dairy cows. We investigated whether grass silage (GS) fed ad libitum (high energy intake, HEI; 141% of daily metabolizable energy requirements) in an 8-wk dry period affects metabolic adaptation-specifically, peripheral insulin resistance-compared with a total mixed ration consisting of GS, wheat straw, and rapeseed meal (55/40/5%; controlled energy intake, CEI; 108% of metabolizable energy/d) fed ad libitum. Multiparous Ayrshire dairy cows (n = 16) were used in a randomized complete block design until 8 wk after parturition. Commercial concentrates were fed 1 and 2 kg/d during the last 10 to 6 and 5 to 0 d before the expected calving date, respectively. Postpartum, a similar lactation diet with ad libitum access to GS and increasing concentrate allowance (maximum of 16 kg/d) was offered to all. The HEI group gained more body weight and had higher plasma insulin, glucose, and ß-hydroxybutyrate concentrations than the CEI group prepartum. Postpartal plasma glucose tended to be higher and milk yield was greater from wk 5 onward for HEI compared with CEI cows. An intravenous glucose tolerance test (IVGTT) was performed at -13 ± 5 d and 9 ± 1 d relative to calving. The HEI cows had greater insulin response to glucose load and smaller area under the response curve for glucose than CEI cows in prepartal IVGTT. Thus, compensatory insulin secretion adapted to changes in insulin sensitivity of the peripheral tissues, preserving glucose tolerance of HEI cows. Higher insulin levels were needed in HEI cows than in CEI cows to elicit a similar decrement of nonesterified fatty acid concentration in prepartal IVGTT, suggesting reduced inhibition of lipolysis by insulin in HEI cows before parturition. In conclusion, high energy intake of moderately digestible GS with low concentrate feeding in the close-up dry period did not have adverse effects on metabolic adaptation, insulin sensitivity, and body mobilization after parturition. Instead, this feeding regimen was more beneficial to early-lactation performance than GS-based total mixed ration diluted with wheat straw.

Effects of dietary energy allowance and decline in dry matter intake during the dry period on responses to glucose and insulin in transition dairy cows.

We assessed whether high energy intake during the early dry period [144% of metabolizable energy (ME) requirements/d] followed by a gradual restriction of energy intake in the close-up dry period (119% of ME/d; HEI) impaired whole-body insulin sensitivity compared with a controlled energy intake (100% of ME/d; CEI) throughout the 6-wk dry period. Multiparous Ayrshire dairy cows (n = 16) were blocked by body weight, body condition score, and expected date of parturition and were used in a randomized complete block design until 10 d after parturition. Cows were fed either HEI or CEI diets based on grass silage during the first 3 wk of the dry period and grass silage supplemented with a commercial concentrate (30% of ME intake) during the final 3 wk of gestation. After calving, all cows were fed grass silage ad libitum and an increasing amount of commercial concentrate (maximum 9 kg at d 10 postpartum). Intravenous glucose tolerance tests (IVGTT) and intravenous insulin challenges were performed -10 ± 5 d (n = 15) and +10 ± 1 d (n = 14) relative to parturition. Following glucose injection, we did not find any treatment effects on glucose and insulin responses. The prepartal nonesterified fatty acid (NEFA) response of the HEI group was blunted, basal NEFA and the decrement of NEFA were smaller, and the area under the response curve (AUC) of NEFA was less negative in HEI cows than in CEI cows. The NEFA response reversed after parturition; the NEFA AUC of the HEI group was more negative than that of the CEI group. We did not find similar responses after insulin injection. Across the treatments, NEFA AUC correlated strongly with the basal NEFA concentration during the IVGTT pre- and postpartum. Calculated and model-based indices characterizing the overall glucose tolerance and ß-cell function and the insulin sensitivity were higher after parturition than during the dry period. Consistent with the lower basal insulin, the acute insulin release after the glucose infusion was smaller in postpartal IVGTT than in prepartal IVGTT. The results suggest that whole-body insulin sensitivity of the cows increased after parturition. However, the role of peripheral insulin sensitivity in the regulation of glucose partitioning seems to be minor relative to the major change in insulin secretion and clearance during the periparturient period.

Effect of prepartal ad libitum feeding of grass silage on transcriptional adaptations of the liver and subcutaneous adipose tissue in dairy cows during the periparturient period.

Prepartal energy overfeeding may predispose cows to a state of increased insulin resistance with greater lipolysis after parturition. The aim of the study was to evaluate the effects of prepartal overfeeding in terms of abundant grass silage ration on the liver and subcutaneous adipose tissue (SAT) gene expression around parturition. Sixteen multiparous Finnish Ayrshire dairy cows were fed ad libitum either grass silage [high energy, HE; 144 MJ/d of metabolizable energy (ME) intake, n=8] or a mixture of grass silage, wheat straw, and rapeseed meal [55:40:5 (CON), 109 MJ/d of ME, n=8] during the dry period (58.2±4.89 d, mean ± standard deviation). Tissue biopsies and blood samples were collected at -14 (±4.98), 1, and 7 d relative to the actual parturition date. The HE cows had greater total dry matter intake, ME intake, and ME balance during the dry period than the CON cows. Compared with CON, the increases in body weight and body condition score were greater in HE during the dry period. Milk yield during the first 2 wk of lactation was not different between the groups. Plasma glucose, nonesterified fatty acids, insulin, glucagon, and ß-hydroxybutyrate did not differ between the groups during the transition period. Dietary treatment did not affect hepatic triglyceride content; however, a delayed increase in hepatic total lipid content was observed in the HE cows at d 1 postpartum. Hepatic cytosolic phosphoenolpyruvate carboxykinase 1 mRNA expression was lower in HE than in CON at d 1 and 7 postpartum. Adiponectin receptor 1 and 2 mRNA abundance tended to be lower in SAT of HE than CON. Lower lipoprotein lipase, leptin, and stearoyl-coenzyme A desaturase mRNA abundances were observed at d 7 postpartum in SAT of the HE cows compared with the CON cows. We concluded that prepartal ad libitum feeding of grass silage may decrease insulin sensitivity and lipogenesis in SAT during peripartal period and may attenuate the increase of hepatic gluconeogenic capacity from propionate compared with a controlled-energy diet.

Prepartal dietary energy alters transcriptional adaptations of the liver and subcutaneous adipose tissue of dairy cows during the transition period.

Overfeeding during the dry period may predispose cows to increased insulin resistance (IR) with enhanced postpartum lipolysis. We studied gene expression in the liver and subcutaneous adipose tissue (SAT) of 16 Finnish Ayrshire dairy cows fed either a controlled energy diet [Con, 99 MJ/day metabolizable energy (ME)] during the last 6 wk of the dry period or high-energy diet (High, 141 MJ/day ME) for the first 3 wk and then gradually decreasing energy allowance during 3 wk to 99 MJ/day ME before the expected parturition. Tissue biopsies were collected at -10, 1, and 9 days, and blood samples at -10, 1, and 7 days relative to parturition. Overfed cows had greater dry matter, crude protein, and ME intakes and ME balance before parturition. Daily milk yield, live weight, and body condition score were not different between treatments. The High cows tended to have greater plasma insulin and lower glucagon/insulin ratio compared with Con cows. No differences in circulating glucose, glucagon, nonesterified fatty acids and ß-hydroxybutyrate concentrations, and hepatic triglyceride contents were observed between treatments. Overfeeding compared with Con resulted in lower CPT1A and PCK1 and a tendency for lower G6PC and PC expression in the liver. The High group tended to have lower RETN expression in SAT than Con. No other effects of overfeeding on the expression of genes related to IR in SAT were observed. In conclusion, overfeeding energy prepartum may have compromised hepatic gluconeogenic capacity and slightly affected IR in SAT based on gene expression.

Effects of abomasal infusion of tallow or camelina oil on responses to glucose and insulin in dairy cows during late pregnancy.

Late pregnancy is associated with moderate insulin resistance in ruminants. Reduced suppression of lipolysis by insulin facilitates mobilization of nonesterified fatty acids (NEFA) from adipose tissue, resulting in elevated plasma NEFA concentrations. Decrease in dry matter intake (DMI) before parturition leads to accelerated lipomobilization and increases plasma NEFA, which may further impair insulin sensitivity. The aim of the study was to evaluate the effects of elevation of plasma NEFA concentration by abomasal infusions tallow (TAL) or camelina oil (CAM) on whole-body responses to exogenous glucose and insulin. We further assessed whether CAM, rich in C18:3n-3, enhances whole-body insulin sensitivity compared with TAL. Six late-pregnant, second-parity, rumen-cannulated dry Ayrshire dairy cows fed grass silage to meet 95% of metabolizable energy requirements were used in a replicated 3 × 3 Latin square with 5-d periods and 5 recovery days between each period. Treatments consisted of abomasal infusion of 500 mL/d (430 g of lipids/d) of water (control), TAL, or CAM administered in 10 equal doses daily. Intravenous glucose tolerance test (IVGTT) and i.v. insulin challenge (IC) were performed on d 5 after 98 and 108 h of treatment infusions, respectively. Infusion of lipids increased basal plasma NEFA concentrations on d 5 (CAM: 0.25; TAL: 0.28; control: 0.17 mmol/L). Following glucose injection, the rate of glucose clearance (CR) was lower in lipid-treated cows (CAM: 1.34; TAL: 1.48; control: 1.74%/min) and time to reach half-maximal glucose concentration (T(1/2)) was longer (CAM: 54; TAL: 47; control: 42 min). Similar responses were observed after insulin injection. Increased plasma NEFA concentration tended to decrease insulin secretion in IVGTT. Infusion of CAM increased plasma C18:3n-3 content (CAM: 26.4; TAL: 16.1; control: 20.9 g/100g of fatty acids). Data suggest that CAM had an insulin-sensitizing effect, because the disposition index and insulin sensitivity index, derived from minimal model analysis, were higher in CAM than in TAL during IVGTT, and lower insulin concentrations during IC led to similar glucose clearance in CAM as in TAL. These results indicate that elevated plasma NEFA concentration per se induces whole-body insulin resistance in late-pregnant dry cows.

Empirical evaluation of genetic clustering methods using multilocus genotypes from 20 chicken breeds.

We tested the utility of genetic cluster analysis in ascertaining population structure of a large data set for which population structure was previously known. Each of 600 individuals representing 20 distinct chicken breeds was genotyped for 27 microsatellite loci, and individual multilocus genotypes were used to infer genetic clusters. Individuals from each breed were inferred to belong mostly to the same cluster. The clustering success rate, measuring the fraction of individuals that were properly inferred to belong to their correct breeds, was consistently approximately 98%. When markers of highest expected heterozygosity were used, genotypes that included at least 8-10 highly variable markers from among the 27 markers genotyped also achieved >95% clustering success. When 12-15 highly variable markers and only 15-20 of the 30 individuals per breed were used, clustering success was at least 90%. We suggest that in species for which population structure is of interest, databases of multilocus genotypes at highly variable markers should be compiled. These genotypes could then be used as training samples for genetic cluster analysis and to facilitate assignments of individuals of unknown origin to populations. The clustering algorithm has potential applications in defining the within-species genetic units that are useful in problems of conservation.

Mapping of multiple quantitative trait loci by simple regression in half-sib designs.

Detection of QTL in outbred half-sib family structures has mainly been based on interval mapping of single QTL on individual chromosomes. Methods to account for linked and unlinked QTL have been developed, but most of them are only applicable in designs with inbred species or pose great demands on computing facilities. This study describes a strategy that allows for rapid analysis, involving multiple QTL, of complete genomes. The methods combine information from individual analyses after which trait scores for a specific linkage group are adjusted for identified QTL at other linkage groups. Regression methods are used to estimate QTL positions and effects; permutation tests are used to obtain empirical threshold values. The description of the methods is complemented by an example of the combined analysis of 28 bovine chromosomes and their associations with milk yield in Finnish Ayrshire cattle. In this example, the individual analysis revealed five suggestive QTL affecting milk yield. Following the strategy presented in this paper, the final combined analysis showed eight significant QTL affecting milk yield. This clearly demonstrates the potential gain of using the combined analysis. The use of regression methods, with low demands on computing resources, makes this approach very practical for total genome scans.

Evaluation of genetic variability and genetic distances between eight chicken lines using microsatellite markers.

The genetic variability and divergence of eight chicken lines were evaluated using nine microsatellite markers. The chicken lines included three White Leghorn hybrids, three Finnish Landrace lines, a Rhode Island Red line, and a broiler hybrid line. All the microsatellite loci were found to be polymorphic, the number of alleles varying from 4 to 13 per locus and 1 to 10 per line, respectively. Observed heterozygosities ranged from 0.00 to 0.91. The highest (0.67) and lowest (0.29) mean heterozygosity per line was observed in the broiler and in White Leghorn of Mäkelä, respectively. Three of the microsatellite loci deviated from the Hardy-Weinberg equilibrium in some populations. F statistics indicated clearly the subdivision of the total population into different lines. The genetic distances confirmed the classification of Finnish Landraces into different lines. A phylogenetic consensus tree was constructed from resampled data (1,000 times) using the neighbor-joining method. According to the phylogenetic tree, the lines were grouped into three clusters, in which the White Leghorns formed one group, two Landraces a second group, and a Landrace, the Rhode Island Red, and the broiler lines a third group. Allele distribution at the loci does not support either the stepwise or the infinite alleles mutation model, but the distribution pattern was quite irregular at different loci.

Casein haplotypes and their association with milk production traits in the Finnish Ayrshire cattle.

Polymorphism of casein genes was studied in half-sib families of artificial insemination bulls of the Finnish Ayrshire dairy breed. Ten grandsires and 300 of their sons were genotyped for the following polymorphisms: alpha s1-casein (B, C), beta-casein (A1, A2), the microsatellite within the kappa-casein gene (ms5, ms4) and kappa-casein (A, B, E). Nine different combinations of these alleles, casein haplotypes, were found. Associations between casein haplotypes and milk production traits (milk and protein yield, fat and protein percentage and milking speed) were studied with ordinary least-squares analysis to find a direct effect of the haplotypes or an association within individual grandsire families using the granddaughter design. Estimated breeding values of sons were obtained from cow evaluation by animal model. No direct effect of the casein haplotypes on the traits was found. Within grandsire families, in one out of four families the chromosomal segment characterized by haplotype 3 (B-A2-ms4-A) was associated with an increase in milk yield (P < 0.01) and a decrease in fat percentage (P < 0.01) when contrasted with haplotype 8 (B-A1-ms4-E). The results provide evidence that in the Finnish Ayrshire breed at least one quantitative trait locus affecting the genetic variation in yields traits is segregating linked to either haplotype 3 (B-A2-ms4-A) or 8 (B-A1-ms4-E).

Polymorphism within the 3' flanking region of the bovine growth hormone receptor gene.

Growth hormone receptor (GHR) has a major role in the regulation of growth hormone action, and thus, is an obvious candidate gene associated with milk production traits in mammals. The present authors have sequenced 273 bp of the 3' flanking region of the bovine GHR, and found three length variants and one base substitution polymorphism in this region. Allele frequencies of the length variants differ between Finnish native and commercial dairy cattle breeds. The chromosomal localization of GHR was confirmed to bovine chromosome 20 by synteny mapping and linkage analysis.

Random amplified polymorphic DNA in cattle and sheep: application for detecting genetic variation.

The present study investigated the use of the random amplified polymorphic DNA (RAPD) method to detect genetic variation in cattle and sheep. The animals studied consisted of samples from five Finnish cattle breeds: native Eastern (18 animals), Northern (24), Western Finncattle (24), Finnish Ayrshire (24), and Finnish Friesian (18); as well as a white (6 animals) and a grey (9) colour type of Finnsheep. The cattle and sheep populations were analysed with 11 and 13 RAPD primers demonstrating the most repeatable amplification pattern. Two out of ten RAPD fragments tested by cross hybridization showed homology between the two species. The RAPD method did not prove efficient for finding new polymorphisms in either species, because we found only three polymorphic RAPD markers for cattle and seven markers for sheep with different allele frequencies between the breeds. Although there is a greater presence of polymorphic RAPD markers in sheep, according to the similarity indices the sheep populations showed a higher degree of homogeneity than the cattle breeds. However, the interbreed and intrabreed similarity indices for cattle did not suggest any significant differentiation of the Finnish breeds, contrary to earlier results based on blood group and protein polymorphism.

Multiple marker mapping of quantitative trait loci of Finnish dairy cattle by regression.

A total of 453 bulls belonging to 11 half-sib families of Finnish Ayrshires were genotyped for six microsatellite markers on chromosome 9. The data were used in an attempt to map quantitative trait loci applying regression as a multimarker approach. For association analysis with a granddaughter design, the EBV for 12 traits were used: milk yield, protein yield, fat percentage, protein percentage, daughter weight, bull growth, calf mortality, days open, fertility treatments, nonreturn rate, SCC, and clinical mastitis. The empirical values of significance thresholds were determined using a permutation test on the experimental data. Although no significant effects were found, the results indicate some support for the existence of a locus on chromosome 9 that affects milk and protein yields.

A quantitative trait locus for live weight maps to bovine chromosome 23.

A multiple-marker mapping approach was used to search for quantitative trait loci (QTLs) affecting production, health, and fertility traits in Finnish Ayrshire dairy cattle. As part of a whole-genome scan, altogether 469 bulls were genotyped for six microsatellite loci in 12 families on Chromosome (Chr) 23. Both multiple-marker interval mapping with regression and maximum-likelihood methods were applied with a granddaughter design. Eighteen traits, belonging to 11 trait groups, were included in the analysis. One QTL exceeded experiment level and one QTL genome level significance thresholds. Across-families analysis provided strong evidence (P(experiment) = 0.0314) for a QTL affecting live weight. The QTL for live weight maps between markers BM1258 and BoLA DRBP1. A QTL significant at genome level (P(genome) = 0.0087) was mapped for veterinary treatment, and the putative QTL probably affects susceptibility to milk fever or ketosis. In addition, three traits exceeded the chromosome 5% significance threshold: protein percentage of milk, calf mortality (sire), and milking speed. In within-family analyses, protein percentage was associated with markers in one family (LOD score = 4.5).

A search for quantitative trait loci for milk production traits on chromosome 6 in Finnish Ayrshire cattle.

Cattle chromosome 6 was scanned with 11 markers, ten microsatellites and the casein haplotype, to identify quantitative trait loci (QTLs) affecting the following milk production traits: milk yield, fat percentage, fat yield, protein percentage and protein yield. Twelve Finnish Ayrshire half-sib families with a total of 480 sons were genotyped and used in a grand-daughter design. Interval mapping was performed with a multiple-marker regression approach with a one-QTL and a two-QTL model, and the significance threshold values were determined empirically using a permutation test. Across-family analysis with the one-QTL model revealed an effect on protein percentage (P < 0.05) and on milk yield (P < 0.05). The analysis with the two-QTL model identified significant effects (P < 0.05) on protein percentage, milk yield, and fat yield. Comparing these two cases, the results suggest the existence of two QTLs on chromosome 6 with an effect on milk production traits. One of the QTLs was located around the casein genes. As the other QTL was similar in location and effect to a QTL found previously in Holstein-Friesians, an identity-by-descent approach could be applied to fine map this region.

Quantitative trait loci affecting milk production traits in Finnish Ayrshire dairy cattle.

A whole genome scan of Finnish Ayrshire was conducted to map quantitative trait loci (QTL) affecting milk production. The analysis included 12 half-sib families containing a total of 494 bulls in a granddaughter design. The families were genotyped with 150 markers to construct a 2764 cM (Haldane) male linkage map. In this study interval mapping with multiple-marker regression approach was extended to analyse multiple chromosomes simultaneously. The method uses identified QTL on other chromosomes as cofactors to increase mapping power. The existence of multiple QTL on the same linkage group was also analyzed by fitting a two-QTL model to the analysis. Empirical values for chromosome-wise significance thresholds were determined using a permutation test. Two genome-wise significant QTL were identified when chromosomes were analyzed individually, one affecting fat percentage on chromosome (BTA) 14 and another affecting fat yield on BTA12. The cofactor analysis revealed in total 31 genome-wise significant QTL. The result of two-QTL analysis suggests the existence of two QTL for fat percentage on BTA3. In general, most of the identified QTL confirm results from previous studies of Holstein-Friesian cattle. A new QTL for all yield components was identified on BTA12 in Finnish Ayrshire.

Consensus and comprehensive linkage maps of bovine chromosome 7.

The objective of this project was to integrate the currently available linkage maps for bovine chromosome 7 (BTA7) by combining data sets from eight research groups. A total of 54 unique markers were typed in eight pedigrees. Multilocus linkage analysis with CRI-MAP produced a bovine chromosome 7 consensus framework map of 27 loci ordered with odds greater than 1000:1. Furthermore, we present a bovine chromosome 7 comprehensive map integrating 54 loci. The locus order is in general agreement with the recently published linkage maps except for one discrepancy. The order of loci BM9289, BMS713, and ILSTS001 was reversed in the consensus framework map relative to the published USDA-MARC bovine chromosome 7 linkage map.

Report of the first workshop on the genetic map of bovine chromosome 1.

A report of the first workshop on the genetic map of bovine chromosome 1 (BTA1) is presented. Five laboratories contributed 31,962 informative meioses from 70 loci. Thirty-two loci which had been typed by at least two laboratories were used to construct a framework genetic map with a likelihood ratio support of at least 1000:1 for locus order. The resulting sex-averaged framework map contained 26 loci and spanned 163.6 CM. The lengths of the female and male maps were 159.5 CM and 165.3 CM, respectively, and there was evidence for an expansion in the telomeric one-third of the male map. Of the four cases where order for closely linked loci differed among the maps produced for each of the contributing laboratories, a consensus order was obtained for three in the framework map. The average genetic distance between framework loci on the sex-averaged map was 6.3 CM.