The present study aimed to investigate the relationships between each step of the reproductive process (cyclicity, estrus, and fertility) and both milk production and body reserves management. The database included 102 studies and 300 treatments collected on electronic databases. Coding for each type of experimental factor enabled within and between experiment variation to be distinguished, and to select subsets of experiments with common objectives in order to avoid inappropriate aggregation of results across studies with very different objectives. Finally, the models were based on limited numbers of experiments (from 14 to 30 treatments originating from 7 to 15 distinct experiments) because (i) only data coded for diet and genetic factors were analyzed, separately (studies on other factors such as milking frequency and parity were too scarce); (ii) a minimum of variation of the explanatory variable was set to enable the quantification of the relationship; (iii) few studies reported comparable reproductive, production and body reserves traits. The results of the meta-analyses showed that the commencement of luteal activity (C-LA) was not associated with milk yield and that the relationship between C-LA and body condition score (BCS) at calving was quadratic (with an optimal BCS at calving around 3.10 on a 0-5 scale). Although the interval from calving to first observed estrus (COE1) is partly composed of CLA, it was not associated with BCS. For each additional 1 kg of milk yield produced at both peak and over the initial 14 weeks of lactation, COE1 was delayed by 1.1 days. The conception rate to first insemination (CRAB.) was reduced by 2.0% (of inseminated cows) and by 2.2% for each additional 1 kg of milk yield at peak and at service respectively. Moreover, CRAM was increased by 38.2% and 22.0% for each additional 1 score of BCS at service and at nadir (i.e. lowest BCS) respectively. Finally, risk of pregnancy (PR) was not associated with milk yield. However, PR was increased by 42.8% (of cows) and 16.8% for each additional unit of BCS at calving and at nadir, respectively. This meta-analysis showed that postpartum cyclicity of dairy cows was mainly associated with BCS at calving, whereas estrus expression was mainly associated with milk yield and fertility with both BCS and milk yield. Genetic and nutritional strategies that target a BCS of 3.10 and limit both BCS loss and peak milk yield could be an effective way to improve reproduction.

L’objectif de cette etude etait de quantifier les relations entre chaque etape du processus de reproduction (cyclicite, chaleurs et fertilite), la production laitiere et la gestion des reserves corporelles chez la vache laitiere. Pour cela, 102 etudes soient 300 observations de traitements ont ete collectees dans des articles obtenus sur des plateformes en ligne (ISI Web of Knowledge et Google Scholar). Afin d’eviter d’agreger des donnees issues d’etudes mobilisant des facteurs experimentaux trop differents pour etre analyses ensemble, un systeme de codage a ete mis en place pour les distinguer et travailler sur des sous-ensembles de donnees. Les resultats des meta-analyses montrent que le delai de reprise de cyclicite est associe a la note d’etat corporel (NEC) au velage. Cette relation est quadratique et indique qu’une NEC au velage proche de 3 points (sur l’echelle 0-5) est associee a un delai de reprise de cyclicite raccourci (23 j). Aucun lien entre le delai de reprise de cyclicite et le niveau de production laitiere n’a ete detecte dans ces analyses. Bien que le delai de reprise de cyclicite conditionne en partie l’intervalle entre le velage et l’apparition des premieres chaleurs (IVCHAL1), aucun lien avec la NEC n’a ete observe dans cette etude. Pour chaque kilogramme de lait supplementaire au pic de lactation, l’IVCHAL1 est retarde de plus d’une journee. La probabilite de reussite a la premiere insemination (TRIA1) est reduite de 2 % pour chaque kilogramme de lait supplementaire au pic de lactation. Le TRIA1 est ameliore de 22 % pour chaque point de NEC supplementaire (entre 1,50 et 3,00), au moment ou l’embonpoint est au plus bas. La probabilite de gestation est augmentee de 43 % pour chaque point de NEC supplementaire au velage (sur une plage variant de 2,50 a 3,50) et de 17 % pour chaque point de NEC supplementaire au minimum (sur une plage variant de 1,50 a 3,00). Aucune relation entre la probabilite de gestation et la production laitiere n’a ete mise en evidence dans cette etude. En conclusion, cette meta-analyse a demontre que le delai de reprise de cyclicite des vaches laitieres serait d’abord lie a la NEC au velage, alors que l’expression des chaleurs serait en premier lieu associee au niveau de production laitiere, et que la fertilite pourrait dependre a la fois du niveau de production laitiere et de la gestion des reserves corporelles. Les strategies de conduite d’elevage visant une NEC proche de 3 points au velage, et qui limitent a la fois l’amaigrissement et le pic de production laitiere pourraient permettre d’ameliorer les performances de reproduction des vaches laitieres.

The feeding strategy and the feed self-sufficiency of 34 commercial dairy farms in the western part of Switzerland were investigated throughout the year 2010. Feed ration composition of farms from the lowlands with relatively high proportions of maize were compared to farms from the mountain area with relatively high proportions of herbage in the rations. Dairy feeds were categorized into herbage, whole-plant maize and concentrate. The proportions of dry matter (DM), net energy for lactation (NEL) and metabolizable protein (MP) sourced from herbage, maize and concentrates were calculated. Dairy farms located in the mountain area had higher proportions of herbage DM in the ration than farms located in the lowland (70% vs. 51 %), as well as herbage-sourced NEL (66 % vs. 47%) and herbage-sourced MP (68% vs. 49%). In contrast, lowland farms showed a higher proportion of maize DM in the ration (31% vs. 17 %). The degree of self-sufficiency of the total feed ration of mountain farms was shown to be larger for DM, NEL and especially MP. A general negative relationship between the proportion of maize DM in the ration and the dairy herd MP self-sufficiency could be observed.

Efficiency of forage surface area in dairy systems in the canton of Fribourg, SwitzerlandMilk output per hectare of forage surface area is a means of measuring the efficiency of dairy production. The aim of this study is to identify which factors are decisive in the variation of surface-area productivity practised in the canton of Fribourg in Switzerland. The analysis is based on a survey of 266 dairy farms which was conducted during the period 2002-2009. Altitude is, as expected, a significant structural factor, constraining milk output per hectare because of lower grassland yield and quality. Lowland farms which use maize silage and moderate amounts of concentrate are, on average, more efficient. Some of the grass-based farms achieve similar levels of efficiency, but many still have room for improvement. Although high efficiency is attainable with individually-medium-yielding cows, a positive correlation was observed between milk output per hectare and cows' forage-based milk yield. In conclusion, it appears that irrespective of local pedoclimatic factors and type of system, surface-area productivity is highly dependent on farmers' ability to optimise their own production system.

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 cows.

L'objectif de cette etude etait de comparer, en systemes pâturants avec velages groupes de fin d'hiver, les performances de production, de reproduction et de sante de vaches laitieres suisses de races Holstein (CH HF), Fleckvieh (CH FV) et Brown Swiss (CH BS) a des Holstein- Friesian d'origine neo-zelandaise (NZ HF) prises comme reference pour ce type de systeme. De 2007 a 2009, des vaches NZ HF ont ete apparieesavec des vaches suisses sur 15 fermes commerciales, incluant au final 259 lactations de 134 vaches. Les vaches CH HF et NZ HF ont eu des meilleures performances laitieres que les CH FV et CH BS (50,2 et 52,1 kg ECM / kg PV0,75 contre 44,3 et 43,6 kg; P < 0,05). La proportionde vaches CH FV gestantes en 6 semaines de reproduction etait tendanciellement plus elevee que pour les vaches CH HF (81 % contre 46 %, P < 0,10), NZ HF et CH BS etant intermediaires (66 et 64 %). Les vaches CH HF presentent aujourd'hui des performances de reproduction insuffisantes pour les systemes en velages groupes. Inversement, les vaches mixtes CH FV sont moins efficaces en termes de production laitiere mais apparaissent adaptees a ces systemes de par leurs bonnes performances de reproduction.

Der Versuch hatte zum Ziel, die Schweizer Rassen Holstein, Fleckvieh und Brown Swiss mit derjenigen neuseelandischer Holstein- Friesian auf Vollweidebetrieben mit saisonaler Abkalbung Ende Winter zu vergleichen. Die zwei Holsteintypen wiesen die besseren Milchleistungen auf, die Schweizer Fleckvieh des Versuchs dagegen eine optimale Fruchtbarkeit. Die Schweizer Holstein ist auch in Low-Input-Systemen eine effiziente Milchkuh, sie musste jedoch fur Blockabkalbung bessere Fruchtbarkeitsleistungen aufweisen, obwohl unsere Modellrechnungen allerdings darauf hin deuten, dass die Milchproduktion einen grosseren Einfluss als die Fruchtbarkeit oder die Fleischleistung hat, was hier den zwei milchbetonteren Holsteintypen einen wirtschaftlichen Vorteil verschafft. Die erhobenen Datensatze fur diese spezifische Systeme mussen jedoch vervollstandigt werden. Die Wahl von Produktionssystemen und effizienten Tieren fur diese Systeme bleibt ein grosses und sich weiter entwickelndes Forschungsfeld. Die Effizienz eines Tieres hangt vom System ab und die Definition t der «Ressourcen- Effizienz» selbst entwickelt sich mit den wissenschaftlichen Fortschritten in der Tierproduktion, der menschlichen Ernahrung, der Klimatologie und Okologie weiter.

Which cow for pasture-based production systems?: Production, reproduction and health The objective of the study was to compare, within pasture-based seasonal-calving systems, the production and reproduction performances of Swiss Holstein-Friesian (CH HF), Fleckvieh (CH FV) and Brown Swiss (CH BS) dairy cows with New Zealand Holstein-Friesian (NZ HF) dairy cows, taken as reference for such systems. From 2007 to 2009, NZ HF cows were paired with Swiss cows on 15 Swiss commercial farms, including in total 259 lactations from 134 cows. CH HF and NZ HF cows had better milk performance than CH FV and CH BS (50,2 and 52,1 kg ECM/kg LW(0,75) versus 44,3 and 43,6 kg; P < 0,05). The CH FV cows had the best reproduction performance, tending to have more pregnant cows 6 weeks after the planned start of mating than the CH HF cows (81% versus 46%, P < 0,10), NZ HF and CH BS cows were intermediate (66 and 64%). The poor reproductive performance of the CH HF cows compromised their suitability for pasture-based seasonal-calving systems. Conversely the dual-purpose CH FV were less efficient in term of milk production but seem to be suitable for these systems owing their good reproductive performance.

L'ensemble des performances de reproduction se sont degradees au cours des 30 dernieres annees, et ce dans de nombreux systemes laitiers. L'objectif de notre etude est d'evaluer la reproduction de vaches laitieres conduites en velages groupes d'hiver, soumises a deux strategies d'alimentation, pour les deux races Holstein et Normande. L'etude des etapes successives du processus reproductif (cyclicite, chaleurs, fertilite) a ete permise par la combinaison d'un dosage tri-hebdomadaire de la progesterone dans le lait, d'un suivi des chaleurs et de diagnostics de gestation. Sur 3 annees, les consequences d'un niveau d'apport alimentaire Haut ou Bas ont ete evaluees sur l'ensemble des etapes. Le lot Haut a recu une ration complete composee de 55 % d'ensilage de mais, 15 % de luzerne deshydratee, 30 % de concentre en periode hivernale et 4 kg de concentre durant la periode de pâturage. Le lot Bas a ete nourri sans concentre : 50 % d'ensilage d'herbe et 50 % de mi-fane en hiver, puis de l'herbe pâturee seule. Le lot Bas a produit moins de lait sur 44 semaines mais plus maigri apres velage que le lot Haut (5207 vs 7457 kg, -1,28 vs -0,96 point d'etat d'engraissement, P < 0,001). Les Normandes ont produit moins de lait et moins maigri que les Holstein. Le regime alimentaire n'a pas eu d'effet significatif sur la cyclicite, mais des effets notables sur les chaleurs dans les deux races et sur la fertilite en race Holstein. Dans le lot Bas, les ovulations ont ete mieux detectees (74 vs 59 %, P < 0,001). En race Holstein, suite aux 1ere et 2e inseminations, les non-fecondations ou mortalites embryonnaires precoces ont ete bien plus frequentes dans le lot Bas que dans le lot Haut (52 vs 27 %, P < 0,001), mais les mortalites embryonnaires tardives ont ete plus frequentes dans le lot Haut (30 vs 9 %, P = 0,004). En fin de campagne, le taux de vaches gestantes n'a donc pas differe entre les deux strategies alimentaires. Plus de Normandes ont ete gestantes en fin de campagne (72 vs 54 %, P = 0,007), cette race ayant presente moins d'anomalies de cyclicite et moins de mortalites embryonnaires tardives. Pour cette seule race, les vaches ont ete gestantes plus rapidement dans le lot Bas que dans le lot Haut, du fait d'ovulations mieux detectees. En conclusion, une meme strategie d'alimentation peut avoir des effets benefiques a certaines etapes du cycle de reproduction, des effets negatifs a d'autres ; ces effets peuvent etre marques pour une race, sans reel impact pour une autre.

The objective of this study was to evaluate the respective effects of milk yield and body condition (BC) loss on cows' postpartum reproductive status taking breed differences into account. 105 Normande (dual-purpose) and 98 Holstein cows were assigned to a low or high feeding level (L-group: 50% grass silage and 50% haylage in winter, no concentrate at grazing; H-group: 55% maize silage, 15% alfalfa hay and 30% concentrate, 4kg concentrate at grazing). Milk progesterone assays led to determine commencement of luteal activity (CLA), postpartum ovarian activity profile, ovulation detection rate and late embryo mortality. Data were analysed by variance-covariance and logistic regression models. In both breeds, L-group cows had a lower 100-day average daily milk yield (MY) than the H-group cows but lost more BC (0-5 scale) (21.5 vs. 30.9 kg/day, -1.38 vs. -0.94 unit, N=102 and 101; P 0.25). Owing to feeding level effects, MY and BC loss could affect reproduction at different stages. Consistent with the literature, a greater BC loss coincides with reduced conception rate. High milk yield coincides with depressed ovulation detection and embryo survival.

Does a low feeding level enhance estradiol synthesis in preovulatory follicles of Holstein x Normande dairy cows?

As oestrous expression of dairy cows has decreased over the last decades oestrus detection has become more difficult. The objective of this study is to identify the main factors that affect oestrus detection in seasonal calving dairy cows, and to establish their relative importance. In each of 5 years 36 Normande and 36 Holstein cows were assigned to a Low or High winter-feeding level group. Half of each group was then assigned to a Low or High pasture-feeding group. The Low–Low strategy resulted in the lowest milk yield and the greatest body condition (BC) loss from calving to nadir BC score (6302kg; −0.98unit). The High–High strategy had the converse effect (7549kg; −0.75units). Low–High and High–Low strategies had intermediate values. The Normande cows had lower milk yield and BC loss than Holstein cows (6153kg versus 7620kg; −0.82unit versus −1.20unit). A database of 415 observed spontaneous oestruses was created. Oestruses were classified according to detection signs: (1) standing to be mounted, (2) mounting without standing, (3) other signs without standing or mounting (slight signs). Presence of another cow in oestrus, access to pasture, Normande breed and Low–Low strategy increased standing detection. In the Normande breed, 97% of oestruses were detected by standing while combining the presence of a herdmate in oestrus and access to pasture with a milk production of less than 6550kg. Holstein cows had a higher frequency of slight signs oestruses than Normande ones, which was associated with a decreased subsequent calving rate (P<0.05). In multiparous Holstein cows, the odds of slight signs detection was multiplied by 7.8 for the High–High group in comparison with the Low–Low group (P<0.05). In our study milk yield had an effect on oestrus detection which was not explained by BC loss. As High–High cows produced more milk than others, we logically found that an increase in milk yield increased slight signs detection. Conversely, as they lost less BC than others, BC loss improved the chance of standing or mounting detection. These two results show that an increase in milk yield may reduce oestrous behaviour even if BC loss is moderate. Oestrus detection is crucial in seasonal compact calving systems. High phenotypic milk yields appear unsuitable with such systems in regard to depressed oestrous behaviour.

Afin de comparer la cyclicite post-partum de vaches des races Abondance, Charolaise, Montbeliarde, Normande et Prim'Holstein, une base de quatre cent trente trois donnees a ete creee a partir des resultats de dosages bi ou tri-hebdomadaires de progesterone du plasma ou du lait issus de quatre fermes experimentales de 2006 a 2008. La date de reprise de cyclicite, la normalite des profils de cyclicite et la duree des cycles normaux ont ete examinees pour chaque race et par parite (primipares, multipares) pour les trois races a plus fort effectif (Charolaise, Normande et Prim'Holstein). En races laitieres, les vaches de races Abondance et Normande se distinguent par la regularite de leur cyclicite post-partum. Alors que, les vaches Prim'Holstein cumulent les handicaps: difficulte de reprise de cyclicite des primipares, nombreux profils anormaux et duree des cycles allongee. La race Montbeliarde semble presenter une situation intermediaire, avec de frequents retards et interruptions de cyclicite. En race Charolaise, le retour d'activite cyclique est le plus long a s'etablir, surtout chez les primipares. En revanche, une fois la cyclicite etablie, aucune anomalie de profil n'est decelee.