1. Robustness and energy efficiency of french beef cows
International conference: steps to sustainable livestock Bristol, 12th-15th January 2016
Robustness and energy efficiency of french beef cows
A. De La Torre, F. Blanc, P. D’Hour, J. Agabriel
INRA, UMR Herbivores & INRA, UE Herbipôle

2. Low-input production systems
What ways to increase
sustainability of
beef productions?
Low-input production systems
What kind of feed?
What kind of animals?
GRASS
Robustness & Efficiency
As you know, feed represents the major variable cost in beef production and the amounts of concentrate in the ruminants diets has dramatically increased during the last decades.
Nowadays, famers are likely to develop low inputs production systems to reduce production costs, to cope with climate change and social expectations, For that, it will rely on the grass ressource either preserved or grazed and at the animal scale, the properties of robustness and aefficiency have to be required.
Use of local feed ressources
 Animals’ abilities to adapt to diets varying in quantity & quality

3. What kind of animals? To be EFFICIENT with regard to energy supply
E milk
E intake + E tissues
Effi_milk =
 Increase in the outputs/inputs ratio,
 be resilient in a broad variety of environments
Strandberg, 2009; Ten Napel 2011
Kitano, 2004
 maintain its functionning despite external or internal perturbations
To be ROBUST
we want firstly efficient cows which correspond to a cow with a high ouput input ratio. and we can calculate the milk efficiency ratio which is the energy of milk produced divided by the energy provided by intake and tissues.
And secondly we want robust cows. The robustness can be defined as the ability of cows to maintain its functionning and to be resilient in a large variety of environments.
Under changing environment, we wonder how cows allocate energy and is this allocation similar according to the type of cows : hardy breed or specialized breed.

4. E. intake …based on the analysis of changes in E. allocation
An evaluation of the energy efficiency
of beef cows …
REPRODUCTION
BODY RESERVES
Non-productive functions
LACTATION
E. intake
This work focused then on the evaluation of E. efficiency and robustness of suclkling cows submitted to feed restriction. This evaluation is based on the analysis of changes in E. allocation between functions.
…based on the analysis of changes in E. allocation
between functions to determine priorities

5. Salers (hardy breed, n=31) Charolais (specialized breed, n=34)
A nutritional challenge to investigate the robustness and E. efficiency
2 breeds
Salers (hardy breed, n=31)
Charolais (specialized breed, n=34)
65 primiparous beef cows
2 nutritional trajectories x
Constraining period
(indoors)
Energy
(%, INRA requirements)
days
post-partum
125 15
Calving
70%
Recovery period
(at grass)
185
120%
To apprehend these two properties, we have set up an experimental framework called a nutritional challenge. 65 PP beef cows either Salers or Charolais cows were submitted to 2 nutritional trajectories.
The low E trajectory corresponds to 70 percent of energy requirements and the control trajectory corresponds to one hundred and twenty percent of energy requirements. After the constraining period, all the cow were put together on the same permanent pasture.

6. What was measured and estimated?
- Compocow model
(Garcia & Agabriel, 2008)
- Adipose cell size
measurements
E. tissues
in net Energy for lactation in MJ/d
E. non-productive functions
Eresid = Eintake – Elactation – Efoetus +/– Etissues
E. Lactation
Weight-suckle-Weight method (Le Neindre, 1973)
E lact. =3,2MJ x kg
E. intake
E. Fœtus = 0
Progesterone profile
Interval Calving-Cyclity (ICC)
- Feed offered and refused
For that, the E of intake was measured or estimated at grass, The energy for milk production was measured by the weight suckle weight method and the efficiency of milk production was calculated as previously presented. We have made the asumption that the energy for gravid uterus was equal to zera nevertheless we have measured plasmatic progesterone concentration to determine the interval calving cyclicity. The energy retained or mobilized in tissues was measured with the adipose cell diameter and the compocow model. And the E. for non productive functions, residual energy, was calculated as the E. intake minus the E. of productive functions
E milk
E intake + E tissues
Effi_milk =

7. Result: end of the challenge (restriction and refeeding period)
Indoors
Grazing
Charolais, 120%
Salers, 120%
Salers, 70%
Body Weight (kg)
Charolais, 70%
Concerning the overall challenge, after only 6 weeks of refeeding period at grass we observed no impact of feed restriction on cows performances and no failure of breeding. Nevertheless dynamics of responses differ according to the feeding energy level.
Post-partum weeks
Feed restriction did not impact the future performances (BW, BCS):
No failure of breeding was observed
BUT dynamics of adaptive responses differ

8. Result: effect of feed restriction on E. allocation
Charolais, 120%
Charolais, 70%
Etissue= -4.6 MJ/db
Eresid=
54.1 MJ/da
Eresid=
30.6 MJ/d b
Etissue=
5.9 MJ/d a
Emilk= 23 MJ/d a
Emilk= 19 MJ/db
Ei = 83
MJ/da
Ei = 45
MJ/d b
Adaptive abilities resulted in :
- a prioritization towards milk production
42 %
28 %
Let’s go to the result part. The first one to illustrate the effect of feed restriction. When a charolais cow experienced a control energy trajectory , the cow allocate 23 MJ/d of energy for milk production, deposit around 6 mj/d in tissues and the E of non productive functions is close to 55 MJ / d.
In constrast, under feed restriction, cows allocated 19 MJ/d for milk production, mobilized 4,6 MJ / d from tissues and the E allocated for non productive functions is around 30 MJ/d.
Underfed cows presented a higher interval of calving –cyclicity close to 1 month but they are more efficient is milk production since efficiency of milk is 1,5 fold higher than in well-fed cows.
To conclude, the adaptive abilities of cows to cope with feed restriction resulted in priority give to milk prodiuction, a mobilization of body reserves and a decrease of energy allocated for non productive functions.
ICC = 86 daysa
ICC = 112 daysb
- a decrease in Energy of non-productive functions
- a body reserves mobilization
Effi_milk = 0.30a
Effi_milk = 0.38b

9. Result: Breed differences in changes in E
Result: Breed differences in changes in E. allocation over the feed restriction
Salers, 70%
Eresid= 30.6 MJ/d
Ei= 48.6 MJ/d
Charolais, 70%
Etissue= -4.6 MJ/d b
Emilk= 25 MJ/d a
Etissue=
-7.2 MJ/d a
Eresid= 30.6 MJ/d
Ei= 45 MJ/d
42 %
Underfed Salers cows are more efficient than Charolais cows :
capacity to mobilize body reserves (15 % of Ei vs 10 % of Ei)
prioritization towards milk production
no delay in the interval calving cyclicity
52 %
Emilk= 19 MJ/d b
If we compared now the energy allocation between breed.
Here the previous results concerning underfed charolais cows. For the same amount of Energy intake, Salers cows allocated similar amount of E. for non productive functions but the energy allocated for milk production is higher as well as the E. provided by the mobilization of body reserves.
The interval of calving –cyclicity is significantly lower and the efficiency for milk production is 1,2 fold higher than that of Charolais cows,
So, underfed salers cows are more efficient than charolais cows and this because they have higher ability to mobilize body reserves for milk production and no impact on reproductive performance has been observed.
ICC = 75 daysa
ICC = 112 daysb
Effi_milk = 0.38
+18%
Effi_milk = 0.45

10. Nutritional challenge (restriction and refeeding periods)
Take home messages
Nutritional challenge (restriction and refeeding periods)
An experimental framework to apprehend the robustness of cows
relying on priorities between life functions
 Refeeding period integrate the dynamic responses of cows after constraints
Suckling beef cows save milk production in priority
Mobilization of body reserves
Decrease in energy allocated to non-productive functions
Salers are more E. efficient than Charolais
High variability of responses within breed
Opportunity to develop selection on robustness and efficiency

11. Thank you for your attention