Towards a better understanding of the respective effects of milk yield and body condition dynamics on reproduction in Holstein dairy cows

The overall reproductive performance has decreased over the last decades, involving changes in cyclicity, oestrous behaviour and fertility. High milk yield (MY), low body condition score (BCS) and large body condition (BC) loss have been identified as risk factors. However, these effects are often confounded, as high MY and body lipid reserve mobilization are correlated. The aim of this study was to evaluate the respective effects of MY and BC on post-partum ovarian cyclicity, oestrus and fertility of Holstein cows. This study provides novel information, as MY and BC change were uncoupled in the overall dataset that included 98 lactations and milk progesterone profiles. Cows were assigned to two feeding-level groups: high feed, which achieved high MY and moderate BC loss throughout lactation (8410 kg, −1.17 unit from calving to nadir BCS), and low feed, which limited MY and triggered a large BC loss (5719 kg, −1.54 unit). MY and BC had different effects at different stages of the reproductive process. Cyclicity as well as non-fertilization and early embryo mortality were mainly driven by body lipid reserves, whereas oestrous behaviour and late embryo mortality were related to MY. The results point to possible uncoupling between cyclicity, oestrus and early and late embryo survival allowing compensation along the reproductive process and leading to similar final reproductive performance. In compact calving systems, which require high pregnancy rates within a short period, higher MY strategies appear unsuitable even where BCS is maintained, owing to depressed oestrous behaviour and probably increased late embryo mortality, which delays rebreeding. Similarly, strategies that compromise cyclicity and fertility by excessively low BCS are unsuitabl

An individual reproduction model sensitive to milk yield and body condition in Holstein dairy cows

To simulate the consequences of management in dairy herds, the use of individual-based herd models is very useful and has become common. Reproduction is a key driver of milk production and herd dynamics, whose influence has been magnified by the decrease in reproductive performance over the last decades. Moreover, feeding management influences milk yield (MY) and body reserves, which in turn influence reproductive performance. Therefore, our objective was to build an up-to-date animal reproduction model sensitive to both MY and body condition score (BCS). A dynamic and stochastic individual reproduction model was built mainly from data of a single recent long-term experiment. This model covers the whole reproductive process and is composed of a succession of discrete stochastic events, mainly calving, ovulations, conception and embryonic loss. Each reproductive step is sensitive to MY or BCS levels or changes. The model takes into account recent evolutions of reproductive performance, particularly concerning calving-to-first ovulation interval, cyclicity (normal cycle length, prevalence of prolonged luteal phase), oestrus expression and pregnancy (conception, early and late embryonic loss). A sensitivity analysis of the model to MY and BCS at calving was performed. The simulated performance was compared with observed data from the database used to build the model and from the bibliography to validate the model. Despite comprising a whole series of reproductive steps, the model made it possible to simulate realistic global reproduction outputs. It was able to well simulate the overall reproductive performance observed in farms in terms of both success rate (recalving rate) and reproduction delays (calving interval). This model has the purpose to be integrated in herd simulation models to usefully test the impact of management strategies on herd reproductive performance, and thus on calving patterns and culling rate

Ovarian activity in Fleckvieh, Brown Swiss and two strains of Holstein-Friesian cows in pasture-based, seasonal calving dairy systems

The objectives of the study were to compare the ovarian activity of Holstein-Friesian (CH HF), Fleckvieh (CH FV) and Brown Swiss (CH BS) dairy cows of Swiss origin with that of Holstein-Friesian (NZ HF) dairy cows of New Zealand origin, the latter being used as a reference for reproductive performance in pasture-based seasonal calving systems. Fifty, second-lactation NZ HF cows were each paired with a second-lactation Swiss cow (17, 15 and 18 CH HF, CH FV and CH BS respectively) in 13 pasture-based, seasonal-calving commercial dairy farms in Switzerland. Ovarian activity was monitored by progesterone profiling from calving to first breeding service. CH BS cows produced less energy-corrected milk (mean 22·8 kg/d) than the other breeds (26·0-26·5 kg/d) during the first 100 d of lactation. CH HF cows had the lowest body condition score (BCS) at calving and the greatest BCS loss from calving to 30 d post partum. Commencement of luteal activity (CLA) was later for NZ HF than for CH FV (51·5 v. 29·2 d; P <0·01), with CH HF and CH BS intermediate (43 d). On average, NZ HF and CH HF cows had one oestrous cycle before the onset of the seasonal breeding period; this was less (P<0·01) than either CH FV (1·7) or CH BS (1·6). There was a low prevalence of luteal persistency (3%) among the studied cows. First and second oestrous cycle inter-ovulatory intervals did not differ between breeds (20·5-22·6 d). The luteal phase length of CH BS during the second cycle was shorter (10·6 d) than that of the other breeds (13·8-16·0 d), but the inter-luteal interval was longer (9·8 d v. 7·0-8·0 d). The results suggest that the Swiss breeds investigated have a shorter interval from calving to CLA than NZ HF cow

Genetic analysis of atypical progesterone profiles in Holstein-Friesian cows from experimental research herds

AbstractThe objective of this study was to quantify the genetic variation in normal and atypical progesterone profiles and investigate if this information could be useful in an improved genetic evaluation for fertility for dairy cows. The phenotypes derived from normal profiles included cycle length traits, including commencement of luteal activity (C-LA), interluteal interval, luteal phase length. and interovulatory interval. In total, 44,977 progesterone test-day records were available from 1,612 lactations on 1,122 primiparous and multiparous Holstein-Friesian cows from Ireland, the Netherlands, Sweden, and the United Kingdom. The atypical progesterone profiles studied were delayed cyclicity, prolonged luteal phase, and cessation of cyclicity. Variance components for the atypical progesterone profiles were estimated using a sire linear mixed model, whereas an animal linear mixed model was used to estimate variance components for the cycle length traits. Heritability was moderate for delayed cyclicity (0.24±0.05) and C-LA (0.18±0.04) but low for prolonged luteal phase (0.02±0.04), luteal phase length (0.08±0.05), interluteal interval (0.08±0.14), and interovulatory interval (0.03±0.04). No genetic variation was detected for cessation of cyclicity. Commencement of luteal activity, luteal phase length, and interovulatory interval were moderately to strongly genetically correlated with days from calving to first service (0.35±0.12, 0.25±0.14, and 0.76±0.24, respectively). Delayed cyclicity and C-LA are traits that can be important in both genetic evaluations and management of fertility to detect (earlier) cows at risk of compromised fertility. Delayed cyclicity and C-LA were both strongly genetically correlated with milk yield in early lactation (0.57±0.14 and 0.45±0.09, respectively), which may imply deterioration in these traits with selection for greater milk yield without cognizance of other traits

Concurrence entre lactation et reproduction chez la vache laitière ([thèse soutenue sur un ensemble de travaux])

Toutes les étapes du processus de reproduction des vaches laitières se sont dégradées, conjointement à l augmentation du niveau de production. L'objectif de cette thèse est d'identifier les effets de la production laitière à chaque étape. Au-delà des effets directement imputables à la corrélation génétique négative entre production et reproduction, la concurrence est communément expliquée par l'amaigrissement post-partum. Deux hypothèses sont testées : à génétique donnée, le niveau de production a un effet propre non expliqué par la gestion des réserves corporelles, et la hiérarchie des effets diffère selon l étape. Pour dissocier ces effets, un protocole mobilisant deux traitements alimentaires a été appliqué à des vaches de races Holstein et Normande conduites en vêlages groupés. Le traitement Haut induit une production élevée et un amaigrissement modéré, le traitement Bas une production bridée et un amaigrissement important. Seule la race influence le taux de gestation final. L œstrus est mieux détecté dans le lot Bas, en cohérence avec une production d œstradiol exacerbée dans les follicules pré-ovulatoires de vaches soumises à ce régime. Les échecs précoces de gestation sont plus fréquents dans le lot Bas ; les mortalités embryonnaires tardives plus fréquentes dans le lot Haut pour la seule race Holstein. Œstrus et développement embryonnaire tardif sont principalement pilotés par le niveau et la dynamique de production laitière ; cyclicité, fécondation ou développement embryonnaire précoce par la gestion des réserves corporelles. Ce travail a donc permis de préciser la concurrence entre production laitière et reproduction chez la vache laitière.As milk production increased, reproductive performance of the dairy cows has decreased at each reproductive step (cyclicity, oestrus, fertility). The aim of this thesis is to identify milk production effects at each reproductive step. Apart from the direct genetic effects, body reserves level and dynamic are generally though to explain the adverse effects of high milk yield. Two hypotheses are tested: at a given genetic value, milk yield has an effect per se which is not mediated through body reserves evolution, and the hierarchy of these two effects varies according to the reproductive step. In order to uncouple these effects, Holstein and Normande cows bred in a compact calving system were submitted to two feeding strategies. The High feeding level allows high milk yield and moderate body condition loss. The Low one limits milk yield but triggers a deep body condition loss. Only the breed influenced final pregnancy rate. Oestrus was better detected in the Low group, in agreement with an enhanced oestradiol production by pre-ovulatory follicles of cows submitted to this feeding strategy. Early pregnancy failures were more frequent in the Low group; late embryo mortalities were more frequent in the High group for the Holstein breed only. Oestrus and early embryo development appear milk yield level and dynamic driven. Cyclicity, fertilization or early embryo development appear body reserves evolution driven. Consequently, this work leads to a better understanding of the competition between milk production and reproduction in the dairy cow.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

The effect of breed on heat detection and fertility of dairy cows maintained on 2 feeding levels

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Facteurs de variation de la détection des chaleurs chez la vache laitière conduite en vêlages groupés

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