Meanwhile,
Cow does not express its:
Reproduction in dairy cattle herds is sometimes penalized by discreet heator silentin cows. Furthermore, Unlike the year (absence of cyclicity. therefore heat), the cow is once again cycle but it does not express heat; We talk about sub-anœstrus. For example, It is important to distinguish the resumption of cyclicity. For example, the expression of the heat, because cows are sometimes reformed for infertility when they are perhaps only subjected to discreet heat. Nevertheless, If an expressed heat is always associated with ovulation. Meanwhile, the reverse is not true: ovulation will not always trigger an expressed heat. Moreover, This can be linked to the cow, but also to the practices of Chaleur detection used by the breeder.
To try to better understand the problem. For example, a study was conducted at the Derval experimental farm (Loire-Atlantique) equipped with a Delaval VMS310 processing robot with cow does not express its the function progesterone dosage (to locate ovulation). Similarly, The exploitation is also equipped with Activimeter necklaces Heatime. Therefore, Breeding has 75 Prim’Holstein cows in corn. Furthermore, grazing silage system, with calving all year round, and an average production level of 9,500 liters/year.
Significant impact of the level of dairy production – Cow does not express its
The data studied spread from 2021 to 2024, or 127 lactations and 558 ovulations in total. For example, The resumption of cyclicity concerns 25 % of cows 20 days after calving; 54 % to 30 days; 88 % to 50 days; the last reaching 90 days. At 50 days. the dynamic of recovery of Cyclicity is the same, whatever the rank of lactation and dairy production at the peak.
In the herd, 2 out of 3 cows express at least silent heat
Out of 127 lactations, Two -thirds have at least silent heat. The level of dairy production at the peak of lactation seems cow does not express its to have a significant impact. Indeed, less than 35 liters/day (25 % of lactations), there are 47 % of lactations with discreet heat. This rate rises to 71 % for peaks from 35 to 45 liters/day (50 % of lactations). and up to 81 % for peaks at more than 45 liters/day (25 % of lactations). On the other hand. the row of lactation and the time to recover Cyclicity do not influence the discreet heat rate.
In addition, out of 558 ovulations, a quarter are associated with silent heat. There either, the row of lactation and the time to take over Cyclicity do not show an impact. On the other hand. we find the effect of dairy production (Table 1), as well as the ovulation rank (Table 2) and the temperature-humidity index (Thi, Table 3).
Table 1: Effect of dairy production (source: Derval farm – Idele/Chamber cow does not express its Agriculture Pays de la Loire)
|
Lactation peak |
% discreet heat (pour 558 ovulations) |
|
< 32 kg/jour |
19 % |
|
32 to 37 kg/day |
25 % |
|
> 37 kg/jour |
31 % |
Table 2: Effect of ovulation rank (source: Derval farm – Idele/Chamber Agriculture Pays de la Loire)
|
Rang d’ovulation |
% discreet heat (pour 558 ovulations) |
|
1 et 2 |
31 % |
|
3 |
26 % |
|
4. more |
15 % |
Table 3: Effect of weather conditions (source: Derval farm – Idele/Chamber Agriculture Pays de la Loire)
|
50 % humidity |
Number of ovulations |
% discreet heat |
|
< 22°C Neutral conditions |
377 |
22 % |
|
22-25°C Light stress |
57 |
25 % |
|
25-30°C Moderate stress |
93 |
31 % |
|
30-34,5°C Severe stress |
31 |
45 % |
Cow does not express its
18 lost fertility points
The consequences of silent heat on the reproduction of the herd can be significant. We saw that at 50 days after calving, 88 % of the cow does not express its cows found their cyclicity for 127 lactations. Among them, 42 % are not subject to discreet heat; 34 % know one (three weeks lost); And 20 % know two (or lost 1.5 months). These heat expression absences impact the fertility of the herdand cause an extension suffered from lactations.
Regarding fertility (success of the AI), it is also impacted. In the Derval study. 206 ovulations (out of the total of 558) were the subject of an AI knowing that all were not associated with expressed heat (ovulation identified via the progesterone dosage of the robot). Gold. The AI success rate went from 49 % for ovulations with expressed heat, to 31 % for ovulation with silent heat, 18 points of less fertility!
Evaluate the phenomenon in its breeding
“It is important that breeders are aware of the existence of these discreet heat which reflect a Dragment of the reproduction functionconclude the authors of cow does not express its the Anaïs Gaigeard study. in charge of experimentation in Derval, and Fabrice Bidan, manager of the reproduction of ruminants at the Institute of Livestock. Indeed. if they trigger AI on the basis of the observation of cows and activity, the success rate will be good, despite a time of breaking for penalized reproduction. While if they are based on the detection of ovulations by the dosage of progesterone to the robot. it risks degrading the success rate due to the discreet heat. »»
To try to assess the phenomenon in its breeding. producers may note The lack of heat between two cycles After a first heat expressed. If they are equipped with the dosage of progesterone. they can cross it with observation in order to identify if certain ovulations are done without heat expression.
More broadly. breeders must ensure the level of production of cows (the production function being in competition with cow does not express its that of reproduction); Be vigilant on the first ovulations because the row of ovulation has an impact on discreet heat; And take into account the stress generated by high temperatures at certain seasons.
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