Estimation of Myostatin gene effects on production traits and fatty acid contents in bovine milk

peer reviewedThe aim of this study was to estimate the genetic parameters of milk, fat, and protein yields, saturated (SFA) and monounsaturated fatty acid (MUFA) contents in bovine milk and to estimate the Myostatin (mh) gene effect on these traits. For this purpose, 51,614 test-day records (24,124, 16,145, and 11,345 for first, second and third lactation, respectively) of 3,098 dual purpose Belgian Blue cows in 38 herds from the Walloon Region of Belgium were used. Because only 2,301 animals, including 1,082 cows with test-day records, were genotyped for mh, the gene content of non-genotyped animals was predicted from animals with a known genotype using the relationships with these animals. Variance components were estimated using Restricted Maximum Likelihood. A 3-lactations, 5-traits random regression test-day mixed model, based on the official Walloon genetic evaluation model for production traits, was used with an additional fixed regression on mh gene content to estimate allele substitution effects. Daily heritability estimates (average of 3 lactations) were 0.34 for SFA and 0.16 for MUFA and were higher than those for production traits (0.11, 0.10, and 0.09 for milk, fat, and protein yields, respectively). Allele substitution effects approximate standard-errors) for mh through the three lactations were-0.628 (+0.343),-0.024 (0.014) and -0.021 (+0.009) kg per day for milk, fat, and protein yields, respectively. Concerning SFA and MUFA contents in milk, the average allele substitution effects were -0.001 (+0.027) and 0.029 (+0.023) g/dl of milk. To conclude, results from this study showed that milk performance traits and milk fatty acid profile are influenced by mh genotypes

Estimation of myostatin gene effects on production traits and fatty acid contents in bovine milk

peer reviewedThe aim of this study was to estimate the genetic parameters of milk, fat, and protein yields, saturated (SFA) and monounsaturated fatty acid (MUFA) contents in bovine milk and to estimate the Myostatin (mh) gene effect on these traits. For this purpose, 51,614 test-day records (24,124, 16,145, and 11,345 for first, second and third lactation, respectively) of 3,098 dual purpose Belgian Blue cows in 38 herds from the Walloon Region of Belgium were used. Because only 2,301 animals, including 1,082 cows with test-day records, were genotyped for mh, the gene content of non-genotyped animals was predicted from animals with a known genotype using the relationships with these animals. Variance components were estimated using Restricted Maximum Likelihood. A 3-lactations, 5-traits random regression test-day mixed model, based on the official Walloon genetic evaluation model for production traits, was used with an additional fixed regression on mh gene content to estimate allele substitution effects. Daily heritability estimates (average of 3 lactations) were 0.34 for SFA and 0.16 for MUFA and were higher than those for production traits (0.11, 0.10, and 0.09 for milk, fat, and protein yields, respectively). Allele substitution effects approximate standard-errors) for mh through the three lactations were-0.628 (+0.343),-0.024 (0.014) and -0.021 (+0.009) kg per day for milk, fat, and protein yields, respectively. Concerning SFA and MUFA contents in milk, the average allele substitution effects were -0.001 (+0.027) and 0.029 (+0.023) g/dl of milk. To conclude, results from this study showed that milk performance traits and milk fatty acid profile are influenced by mh genotypes

Large-scale predictions of methane emission and body weight as tools contributing potentially to the genetic improvement of environmental sustainability of milk production

Maximizing profitability of dairy farms ensuring also mitigation of cattle environmental footprint is a major concern in milk production. Improvement of dairy cows’ feed efficiency is of interest to achieve this goal as feed costs contribute largely to the variable costs in dairy sector and because feed efficiency is related to environmental concerns. As feed efficiency of dairy cows is influenced by several interconnected factors, many aspects of research could be addressed to improve it. For that, ample volume of reliable data from a lot of cows is required. Methane emission and body weight of lactating dairy cows have large influence on feed efficiency. However, these traits are difficult to measure at large scale in commercial farms. Therefore, the objective of this thesis was to improve predictions of daily methane emissions from milk mid-infrared spectra and body weights of lactating dairy cows in order to study the genetic variability of these traits and to investigate the opportunity of using them as tools to improve environmental sustainability of milk production. First, predictions of methane from milk mid-infrared spectra were improved by introducing the lactation stage information into the calibration process of the prediction equation in order to take into account the expected metabolic status of the cow. As milk mid-infrared spectra are collected routinely during milk recording, this equation allows to predict methane emissions of dairy cows at a large scale and at an individual level. High throughput screening of dairy cows for methane was conducted with mid-infrared methane predictions. Also, correlations between milk mid-infrared predicted methane and milk fatty acids were predicted throughout lactation. These correlations changed across lactation and these variations were related with the metabolic origins of milk fatty acids and then with the expected metabolic status of the cows over lactation allowing to confirm that integration of lactation stage in methane mid-infrared prediction equation was useful. Thereafter, a model was built to predict body weight of dairy cows throughout lactation from body weights estimated from linear conformation traits recorded at least once during the lactation. These predictions could be associated with milk production and composition as well as animal characteristics to estimate new traits related to feed efficiency like dry matter intake. Finally, this thesis demonstrated that methane emission and body weight of cows fulfill all criteria to be included in a breeding program in order to improve feed efficiency of dairy cows. To conclude, this thesis has shown that predictions of methane emission and body weight of dairy cows are traits of interest for widespread screening of herds in order to develop genetic selection tools to improve environmental sustainability of milk production

Effect of different dietary fat sources at the end of gestation on the performance of sows and their offsprings

peer reviewedFrom day 103 in gestation until farrowing, 4 successive groups of 15 sows received 70 g per day of one of the 3 following oils: 1) coconut oil (CO); 2) fish oil (FO) and 3) shark liver oil (SO). At day 102 of gestation, at farrowing and at weaning, backfat thickness of the sows was determined. The total number of piglets, the number of piglets born alive, stillborn and dead during the suckling period and the duration of gestation were measured. At birth as well as 24 hours, 14 days and 28 days (weaning) later, the piglets were weighed individually. Colostrum samples were collected at farrowing and 24 hours later for the determination of IgG and IgA contents and the fatty acid profile. Neither performance parameters of the sows nor IgG and IgA concentrations in colostrum were affected by the different dietary treatments. This was probably due to the short duration of trial period in which the oil supplements were administered. However, the colostral fatty acid profiles reflected very well the profiles of the supplemented oils. Furthermore, the different treatments affected the growth performances of the piglets. At weaning, the piglets from the FO treatment were respectively 263 and 329 g heavier than the piglets from the SO and CO treatments (P < 0.05). This corresponded to 4.2 % and 5.8 % increase of the ADG in comparison to the SO and CO treatments, respectively. These results show the importance of the fatty acid composition in colostrum on the performances of piglets and consequently the importance of the feeding of sows at the end of gestation

Genotype x Climate interactions for protein yield using four European Holstein Populations

peer reviewedReaction norm models were applied to investigate genetic variation in heat tolerance of Holsteins across environments using long term protein milk yield test-day records and weather variables as proxy of climate change. Data represented four European regions characterized by different management systems and environments. Daily protein yield changed across the trajectory of temperature humidity index (THI) for all studied populations, pointing out negative associations between warm conditions and cow performance. For most regions, additive genetic variances for daily protein yield decrease when THI increases. Antagonistic relationships between level and intercept were relatively limited for Slovenia compared to the three other regions. Rank correlations of estimated breeding values for three proposed heat tolerance measures ranged from 0.56 (Spain and Slovenia) to 0.81 (Walloon Region of Belgium and Luxembourg), indicating a possibility of genotype by environment (G x E) for some pairs of regions.Projet de chargé de recherches "DairyHeatStress

Estimating myostatin gene effect on milk performance traits using estimated gene content for a large number of non-genotyped cows

The objective of this study was to estimate the myostatin (mh) gene’s effect on milk, protein and fat yield in a large heterogeneous cow population, of which only a small portion was genotyped. For this purpose, a total of 13 992 889 test-day records derived from 799 778 cows were available. The mh gene effect was estimated via BLUP using a multi-lactation, multi-trait random regression test-day model with an additional fixed regression on mh gene content. As only 1416 animals, (of which 1183 cows had test-day records) were genotyped, more animals of additional breeds with assumed known genotype were added to estimate the genotype (gene content) of the remaining cows more reliably. This was carried out using the conventional pedigree information between genotyped animals and their non-genotyped relatives. Applying this rule, mean estimated gene content over all cows with test-day records was 0.104, showing that most cows were homozygous 1/1. In contrast, when gene content estimation was only based on genotyped animals, mean estimated gene content over all cows with test-day records was with 1.349 overestimated. Therefore, the applied method for gene content estimation in large populations needs additional genotype assumptions about additional animals representing genetic diversity when the breed composition in the complete population is heterogeneous and only a few animals from predominantly one breed are genotyped. Concerning allele substitution effects for one copy of the ‘mh’ gene variant, significant decreases of 276.1 kg milk, 23.6 kg fat and 22.8 kg protein/lactation were obtained on average when gene content estimation was additionally based on animals with assumed known genotype. Based on this result, knowledge of the mh genotypes and their effects has the potential to improve milk performance traits in cattle

Assessing meteorological conditions effects on MIR predicted methane emissions of Holstein cows under a temperate environment

MéthaMil