The dairy farming systems of Western Europe are based on a simple feeding system composed of grazed and preserved grass, maize silage and concentrates in variable proportions. There is, nevertheless, a great diversity of feeding strategies between dairy farms. Over 5 years, we studied the direct and delayed effects of four feeding strategies on the lactation and reproduction performances of Holstein and Normande dairy cows. The four feeding strategies (denoted Hh, Hl, Lh and Ll) correspond to two total mixed rations applied in winter from calving to turnout (maize silage with 30% concentrate or grass silage with 15% concentrate), which were subsequently crossed with two levels of concentrate supplementation at grazing to 210 days. Each year, 72 dairy cows managed in grouped winter calving were assigned to the four strategies. Finally, the results of 325 lactations and 295 inseminated cows were analysed. The four strategies resulted in considerable variation in nutrient intake and, in particular, in differences in concentrates consumed, with values of 1407, 1026, 773 and 392 kg dry matter per cow for strategies Hh, Lh, Hl and Ll, respectively. Total milk production (7567, 7015, 6720 and 6238 kg per cow for treatments Hh, Lh, Hl and Ll, respectively), milk fat content (39.0, 37.1, 40.3 and 38.5 g/kg, respectively), milk protein content (33.0, 31.8, 33.1 and 31.6 g/kg, respectively), and the character of the lactation and body condition curves were all highly sensitive to the strategies applied. While no significant interaction was detected on total lactation yield, the Holstein cows reacted more dramatically to each dietary change at each period, compared with the Normande cows. Winter feeding did not affect the production of milk at pasture whereas, at pasture, the milk from the cows of the H groups in winter was higher in milk fat and protein content. Reproduction performance was unaffected by feeding strategy. The Holstein cows, well fed and producing the most milk (Hh and Hb), had the lowest rate of success at first artificial inseminations (21.5%). The dual-purpose Normande cows had a pregnancy rate 10 points higher than Holstein cows. This comparison of strongly contrasting feeding strategies confirms the immediate reactivity of dairy cows (in terms of milk performance and body condition) to variations of nutritive intake throughout lactation, with a weak carryover effect from feeding levels early in lactation. In contrast, reproduction performance was less sensitive to variation in nutrient supply. Keywords: dairy cows, feeding strategy, lactation, reproduction, breed ImplicationsThe main objective of this 5-year experiment was to describe the dairy cows' ability to adapt their lactation and reproductive functions to different feeding strategies applied during lactation. These original results provide practical information on breed, feeding system effects and their interaction, and will help advisors and farmers to choose the most efficient systems according to the economic circumstances. IntroductionIn Fra...

Much research has been carried out and published on dairy replacement management, in order to rear heifers as efficiently as possible, from both a technical and economical point of view. In most cases, the aim is to rear the heifers at the lowest cost possible without any deleterious effects on future performances. However, the importance of dairy heifer husbandry is not sufficiently well recognized and probably mishandled by most farmers. The present review aims to give an actual overview of rearing procedures in dairy heifers and possible ways to achieve optimal goals. For many years, it has been well known that rapid rearing lowers the age of sexual maturity and consequently may be an efficient way to reduce the non-producing period prior to conception. But this may impair mammary development and consequently future milk production, at least during first lactation. In addition, a growth rate that is too low may not only be costly but also result in animals that are too fat at first calving, creating problems such as calving difficulties, dystocia, etc. Genetic considerations must also be factored, i.e. frame, size, body weight, etc. have changed during the last 20 years and there are differences between breeds. As a result, some time-honoured recommendations may not be appropriate. The present paper reviews factors and management practices that may affect rearing and subsequent performance of dairy heifers.

Reproductive performance has decreased over the last decades in many dairy systems. This study aimed at comparing the effects of a high-and a low-feeding level on reproductive stages (cyclicity, oestrus and fertility) of Holstein and Normande cows in a grass-based winter compact calving system. High-fed cows received a total mixed ration composed of 55% maize silage, 15% dehydrated alfalfa pellets and 30% concentrate in winter and 4 kg/day concentrate supply at grazing. Low-fed cows only received 50% grass silage and 50% haylage in winter and no concentrate at grazing. Low-fed cows produced less milk over 44 weeks, but lost more body condition (BC) than high-fed ones (5207 v. 7457 kg, 21.28 v. 20.96 unit, P , 0.001). Normande cows produced less milk and lost less BC than Holstein ones (5596 v. 7068 kg, 20.89 v. 21.36 unit, P , 0.001). Post-partum ovarian activity was little affected by the feeding level. In both breeds, ovulation detection rate was higher in low-fed cows (74% v. 59%, P , 0.001) and detection relied more frequently on standing behaviour (67% v. 55%, P 5 0.022). In both breeds, the recalving rate following the first and second inseminations was not significantly affected by the feeding level, although more non-fertilisations or early embryo mortalities occurred in low-fed cows (43% v. 26%, P 5 0.004). For the Holstein breed, this was clearly explained by more late embryo mortalities in high-fed cows (30% v. 9%, P 5 0.004). Finally, pregnancy rate by the end of the 13-week breeding period was similar between feeding groups. Conversely, the Normande dual-purpose cows had a higher pregnancy rate by the end of the breeding period than the Holstein dairy cows (72% v. 54%, P 5 0.007), owing to a better ovarian activity (79% v. 54% normal, P , 0.001) and a higher recalving rate following insemination (53% v. 37%, P 5 0.007). In conclusion, this study demonstrates that feeding levels with converse effects on milk yield and BC score also have converse effects on reproductive stages and lead to quite similar final reproductive performance in compact calving systems. Normande cows benefit from an overall better reproductive performance, but do not suit high feeding levels for very compact calving systems owing to depressed oestrous behaviour.

The aim of this study was to investigate the effects of a severe nutrient restriction on mammary tissue morphology and remodeling, mammary epithelial cell (MEC) turnover and activity, and hormonal status in lactating dairy cows. We used 16 Holstein × Normande crossbred dairy cows, divided into 2 groups submitted to different feeding levels (basal and restricted) from 2 wk before calving to wk 11 postpartum. Restricted-diet cows had lower 11-wk average daily milk yield from calving to slaughter than did basal-diet cows (20.5 vs. 33.5 kg/d). Feed restriction decreased milk fat, protein, and lactose yields. Restriction also led to lower plasma insulin-like growth factor 1 and higher growth hormone concentrations. Restricted-diet cows had lighter mammary glands than did basal-diet cows. The total amount of DNA in the mammary gland and the size of the mammary acini were smaller in the restricted-diet group. Feed restriction had no significant effect on MEC proliferation at the time of slaughter but led to a higher level of apoptosis in the mammary gland. Gelatin zymography highlighted remodeling of the mammary extracellular matrix in restricted-diet cows. Udders from restricted-diet cows showed lower transcript expression of α-lactalbumin and kappa-casein. In conclusion, nutrient restriction resulted in lower milk yield in lactating dairy cows, partly due to modulation of MEC activity and a lower number of mammary cells. An association was found between feed restriction-induced changes in the growth hormone-insulin-like growth factor-1 axis and mammary epithelial cell dynamics.

There has been a significant decline in the reproductive performance of dairy cattle in recent decades. Cows, take longer time to return to the oestrus after calving, have poorer conception rates, and show fewer signs of oestrus. Achieving good reproductive performance is an increasing challenge for the dairy producer. In this study we focus on understanding the overall biological phenomena associated with nutritional sub-fertility rather than the underlying multiplicity of physiological interactions (already described in a number of recent studies). These phenomena are important because they represent the natural adaptations of the animal for dealing with variations in the nutritional environment. They can also be used to monitor and modulate reproductive performance on-farm. There is an underlying trade-off between two aspects of reproduction: investment in the viability of the current calf and investment in future offspring. As the investment in, and viability of, the current calf is related to maternal milk production, we can expect that level of milk production per se has effects on subsequent reproductive performance (investment in future offspring). Lactating cows have a lower proportion of viable embryos, which are of poorer quality, than do non-lactating cows. The same applies to high-compared to medium-genetic merit cows. Another important biological property is the adaptive use of body reserves in support of reproduction. Orchestrated endocrine changes in pregnancy and lactation facilitate the deposition of body lipid during pregnancy and mobilisation in early lactation. When the cow fails to accumulate the reserves she needs to safeguard reproduction she delays committing to further reproductive investment. But how does the cow 'know' that she is failing in energy terms? We argue that the cow does this by 'monitoring' both the body fat mobilisation and body fatness. Excessive body fat mobilisation indicates that current conditions are worse than expected. Body fatness indicates the future ability of the cow to safeguard her reproductive investment is compromised. Both delay further reproductive commitment. The relationship between reproductive performance and; milk production as an index of maternal investment, body fatness as an index of ability to safeguard reproductive investment, and body fat mobilisation as an index of the current nutritional environment -are examined. Nutritional strategies that seek to modulate body mobilisation and the endocrine environment by use of glucogenic and lipogenic diets, and the use of in-line progesterone profiles to monitor reproductive status are then discussed in this biological context.

Livestock farming is an essential activity in many rural areas, where it contributes to the maintenance of soil fertility and farmland biodiversity, as well as to a set of social public goods including food security, rural vitality and culture. However, livestock sustainability assessments tend to focus primarily on environmental and economic dimensions; therefore, these valuations might be limited because they do not consider the complete set of associated goods and services (GS). Hence, a need exists to recognise the multiple contributions provided by livestock to human well-being and society. The objective of this study was to analyse the provision of multiple GS derived from livestock across regions in France and empirically demonstrate sets of GS that repeatedly appeared together. We designated these multiple GS provided by livestock as contributions to productive, environmental, rural vitality and cultural benefits that human populations derive directly or indirectly from livestock agroecosystems. First, we combined expert knowledge with results of a literature review to define a bundle of GS provided by livestock. We then described indicators that quantified each good or service and screened national databases to determine the availability of supporting data. Finally, we assessed the GS and their relationships (synergies or trade-offs) on a nation-wide gradient in France at the department level (Nomenclature of Territorial Units for Statistics 3). Four main categories of GS were considered: provisioning (e.g. food quantity and quality), environmental quality (e.g. biodiversity, landscape heterogeneity, water quality), rural vitality (e.g. employment, rural dynamism) and culture (e.g. gastronomy and landscape heritage). Four major types of GS bundles were identified, which suggested strong contrasts among French rural areas in terms of the nature of the GS that occurred together and their levels of provision. GS bundles in France had a non-random spatial distribution. This study represents an initial step towards developing a methodology to consider GS bundles provided by livestock. Nonetheless, further research is needed to understand socio-economic, environmental, political and geographic determinants of the composition of GS bundles.

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, 21.17 unit from calving to nadir BCS), and low feed, which limited MY and triggered a large BC loss (5719 kg, 21.54 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 unsuitable.

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