Results

3.1 Evaluation of the ability of the model to represent mixed milk/meat bovine herd systems

In the farm type simulation, we observed some small differences between the farm type data and simulation results (Table 6). Purchases (excluding forage) and sales (excluding animal products) are not taken into account for the evaluation of the model because they are adjustment variables. Purchases are made to balance animal feed in terms of volume and energy content. Sales occur either when there are surplus (marketable) products or when these products are more profitable for sale than for use with livestock.

To evaluate the model’s ability to deal with bovine mixed milk/meat herd breeding systems, we compare the simulation results with the 2 reference farm types whose herd compositions are close to the 50D scenario. The maximum relative difference (in absolute value) between simulation result and their corresponding value in the farm-types is 22%, but the average difference is 10%. We can conclude that the modified model represents properly the farm types.

107 Table 6. Differences between simulation results and reference farm data.

Simul: Simulation results

Diff: Relative difference between simulation result and his corresponding value of the farm type

3.2 Effect of herd cattle type mixes on production, feeding and grazed grass utilization rate

Table 7 resumes the parameters related to milk and meat production, grass and concentrate consumption, grazing rates, and the corresponding use of the agricultural area by area (ha) - exclusive pasture (pasture), 1 cut of hay followed by pasture (1C_

hay + pasture), 1 late cut of silage followed by pasture (1C_ late silage + pasture), early cut of silage followed by 1 cut of hay followed by pasture (silage + hay + pasture).

3.3 Animal products: meat and milk production

For Farm_1 the LUs reach their maximum for the 25D scenario with 82 LUs while for Farm_2 the maximum LU is reached at 50D with137 LUs. For each farm type, with scenario 75D we have at least half of the maximum production of meat (meat production in 0D) (Table 7). The difference in meat yields compared to maximum meat production are 37%, 21% and 10% respectively for the 75D, 50D, and 25D scenarios for Farm_1. For Farm_2, these differences are respectively 42%, 24% and 11% for the 75D, 50D, and 25D scenarios. Because dairy herds produce meat in addition to milk, meat production from 75D progressively approaches maximum meat production (production of specialized herds 0D). 0D systems have limited milk production. In the 100D scenario, little meat production is observed due to the exclusive presence of dairy herds in the farm. For the 2 farm types, milk production shows an almost linear decrease from 100D to 0D, from maximum production of milk to zero in the 2 cases.

Farms Farm_1 Farm_2

Parameters Farm type Simul Diff (%) Farm type Simul Diff (%)

Total product (k€) 136 115 -15 192 150 -22

Total grazed grass (tDM) 167 176 5 285 324 13

Grazed grass per LU(tDM/LU) 1.90 2.00 5 2.25 2.56 14

Fodder per LU (tDM/LU) 2.11 1.77 -16 2.58 2.4 -7

Milk production (kL/year) 180 180 0 300 329 10

108 Table 7. Table of indicators of production, feeding, pasture and grazed grass utilization.

3.4 Grass and concentrate consumption

For the 2 farm types, the total fodder consumption (total of silage, wrapping, hay, and grass) per LU is around 4tDM/LU for all the scenarios. For both farm types there is a variation in concentrate consumption per LU shown by a decrease of concentrate consumption with the reduction of dairy LU in herds. The combination of a dairy and a suckling herd maximizes the total number of LUs on the farm in a context of forage autonomy while reducing consumption of concentrate. Suckling herds are less demanding from the nutritional standpoint, hence the advantage of being able to reduce the intake of concentrate. A specialised dairy herd consumes more concentrate than a mixed herd breeding system composed of dairy and suckling cattle, with an equal total number of LUs as shown by the results of Farm_1. Thus, the reduction in concentrate consumption per LU depends more on the proportion of dairy LU than on the total LU. Overall the use of concentrate tends to decrease with the decrease in the percentage of dairy cattle LU in the farm. However, this decline in concentrate Levels of grass valorization by grazing and correspondent use of the agricultural area

Total pasture grass available (tDM) 247 239 230 219 202 276 310 344 340 348

109 scenarios of Farm_2 and these scenarios have big stocking rate increases of +22%

and +11% respectively for the 50D and 75D compared to the 100D stocking rate. Also, their total fodder consumption is slightly lower at 4.64 tDM/LU for 75D and 4.28 tDM/LU for 50D, compared to 4.79 tDM/LU for 100D (Table 7). Generally, the use of concentrate is positively related to the number of dairy cow LUs in the system.

3.5 Grazed grass utilization rate

The hay and silage harvests are conditioned by the mechanization decisions through the technical itinerary (TI). For Farm_1 the maximum grazed grass utilization rate is 85% for the 50D system. For Farm_2 the maximun grazed grass utilization rate is 100% for the 25D system (Table 7). Compared to the 50D (Farm_1) and the 75D (Farm_2) systems, the grazing rates are lower for the specialized systems with the minimum values for specialised milk systems, being 58% for Farm_1 and 72% for Farm_2. The maximun grazed grass per LU is with the 50D for Farm_1 and 75D for Farm_2, and the maximum amount of grass harvested per LU (tDM/LU) corresponds to the specialised dairy systems for both farm types (Table 7). The differences in grazing rates are due to the fact that suckling herds are able to consume low quality fodder, and graze grassland areas away from the farm headquarters. In contrast, dairy herds are more demanding of food and have limited access to grassland areas away from the farm headquarters due to the twice a day milking at the headquarters’ milking parlour. The diet of dairy herds is based more on harvested grass than the diet suckling herds which is based more on grazing.

3.6 Economic performance

We can see in Table 8 that in both cases the economic performance and the gross margin of the farm decrease with the decreases of dairy LUs (increase of suckling LUs) on the farm. The difference corresponds to the total costs which decrease with the decreases of dairy LUs on the farm. Unlike 0D systems, 100D systems have a higher output with heavy costs. Hence the costs decline with the increase of suckling LUs in herds (Table 8).

110 Table 8. Table of economic results.

Farms Farm_1 Farm_2 Operating profit (€) 8,147.62 8,897.45 8,966.17 7,825.46 4,725.31 39,530.87 43,266.22 45,916.10 40,342.13 33,127.01 Operating profit / MWU 6,511 7,215 7,647 7,671 5,786 18,824 20,603 21,865 22,342 22,023 SD operating profit / MWU 1,127.76 1,135.34 1,232.37 1,333.99 1,662.86 1,314.61 1,337.01 1,437.03 1,463.26 1,751.47

The total product = meat, milk, and crops receipt + subsidies

The Gross margin = (total product + Subsidies) – (Operating cost + Structural cost) Total loads = Structural cost + Operating cost + depreciation + taxes + salary

Operating profit = Gross margin – (depreciation + taxes+ salary)

The operating profit per Man Work Unit Human Work Unit (MWU) for Farm_1 and Farm_2 are at the maximum for the 25D distributions. From the 25D distributions, the operating profit per MWU decreases with the decreases of dairy LU in the farm.

However, in both cases the operating profit per MWU is close between 50D and 25D systems with respective differences of -0.3% for Farm_1 and -2% for Farm_2. There are moderate costs with good economic performances and operating profit for these mixed herd systems. For these systems, less MWUs are used as the dairy LUs decrease, which contributes to a reduction of costs when the number of dairy LU decreases. At the same time, subsidies increase with the increase of suckling herd LUs, because premiums per suckling cow increase with the number of suckling cows.

For systems with suckling cows this reduction in labor contributes to a reduction of costs when the number of dairy cows decreases on the farm.