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Dairy system in Argentina is based on grazing. Feeding consists, on average, of 56% forage, 17% whole corn plant silo and 27% balanced feed or grains. Holstein breed is the most widely used and is found in 98% of the establishments (Capellini 2011). It is the result, mainly, of artificial insemination with semen from the USA and Canada (Etcheverry 2012). In most dairy establishments of the country, farmers are unaware of the values of productive and reproductive indicators and, therefore, it is difficult to estimate their impact on the final economic result.
Milk production per cow is one of the main factors influencing economics of dairy cattle production (Nemeckova et al. 2015 and Krpalkova et al. 2016). High milk yields can mean high incomes, but they can also affect health and fertility of cows and, as a result, contribute to an increase of the percentage of culled cows (Horvath et al. 2017a). Profitability of dairy establishments also depends, to a large extent, on reproductive efficiency, calving interval length, age at first calving and other indicators that are not always considered (Dono et al. 2013). Involuntary culling cows, before the optimal time, reduces profitability (de Vries 2004). Likewise, longevity is another factor that affects the economic results of dairy establishments (Horvath et al. 2017b). This fact makes it difficult to make decisions aimed at improving the expected economic results.
The use of indexes has been a common practice to evaluate efficiency of dairy farming in different parts of the world (Lopes et al. 2009). Age at first calving, calving interval, mortality and birth and culling percentage constitute technical and managerial indexes of significant importance, as indicators of herd productivity, performance and evolution, as well as of milk production system profitability (Lopes et al. 2004, 2005).
Profitability of the livestock activity can be evaluated from the calculation of zootechnical indexes, because these are related to production and, consequently, to the main income source for the farmer. At the same time, farmers and technicians who advise this activity, must pay particular attention to the values of these zootechnical indexes, so that they can identify those aspects that threaten a better profitability of the activity, by not allowing to maximize production, minimize costs, or both (Lopes et al. 2009).
The objective of this study was to evaluate the importance of a group of indicators, not always valued, in the economic results of a milk production system based on grazing.
Materials and Methods
Retrospective data were used, corresponding to lactations of 1,785 primiparous Holstein cows, American-Canadian biotype, collected between 1999-2016, in two commercial establishments of the same company, located in Villa Elisa town, Colón department, Entre Ríos province, Argentina. Establishment 1 is located at 32°04'21.0" South and 58°38'13.8" West. Establishment 2 is located at 32°07'53.7" South and 58°36'22.7" West. During the cited period, all cows were subjected to the same management and the same milking facilities were used.
For the purposes of analysis, only those records corresponding to cows with information from their birth to the date of their culling or death, and with a second calving, were included. This last criterion was included to ensure that comparison was not affected by the presence of cows with a failed first lactation.
Of the cows that met the inclusion criteria, those with less than 671 days or more than 1,098 days at first calving, with a first lactation less than 150 days, a first calving-second calving interval less than 310 days, or both, were excluded.
Out of the total number of cows that met inclusion and exclusion criteria, those that gave birth to their first calf at 24, 27 and 32 months of age were identified, and then 50 members of each of these groups were randomly chosen.
Each cow, belonging to the three established groups: group 1) age at first calving 750 d (24 months), group 2) age at first calving 840 d (27 months) and group 3) age at first calving 1,098 d (32 months), was characterized based on the values of the following indicators:
Productive indicators. Age at first calving (EPP): first calving date - birth date, d.
Total Productive Life (VPT): culling or death date - birth date, period of time (days) from birth to culling or death.
Total milk production (PLT): ∑ liters of milk per completed lactations, total liters of milk produced during the productive life.
Milk index (IL): total for their productive life, il: PLT / VPT (Marini and Oyarzabal 2002 a, b).
Productive days (PD): VPT - EPP, d.
Number of calvings (NP): (DP / IPPp) + 1
Production per lactation (PL): PLT / NP, L
Reproductive indicators. Mean calving interval (IPPp): age at culling or death, d - age at first calving, d / number of calvings - 1
Indicators and costs. For the analysis of the economic balance, an establishment with 100 cows was modeled from the results and the following indicators and costs were considered:
PL (L): PL * 100 cows
Births: estimate of births adjusted to one year, according to Magnasco (1998)
Born females: births / 2, the result of which was rounded towards the female
Percentage of losses (Hailiang Zhang et al. 2019)
Actual females: born females - 18% losses (from birth to first calving)
-
Suitable females: suitable females for replacement
In this indicator, 24 months was estimated as the expected optimum time (Krpalkova et al. 2017). The amount of 100 was established as value, and as values moved away, it was calculated as (value of EPP of each group in months * 100) / 24 months as optimal value (Marini et al. 2018).
Replacement: 100 cows / (NP * 100)
Missing or surplus heifers: replacement - suitable females
Milk: total PL * price of milk liter paid to the farmer. Price of a milk liter paid to the farmer $ 19.10 (Mercado de Liniers 2020)
-
Culled cow: (weight of culled cow * replacement) * price per kg of culled cow
Discard cow weight: 550 kg
Price of a kilogram of culled cow $ 55 (Mercado de Liniers 2020)
-
Calf: calf weight * price per kg of calf
Calf weight: 80 kg at weaning
Price per kilogram: $ 80 (Mercado de Liniers 2020)
Heifers: number of heifers * heifer price $ 120,000 (Mercado de Liniers 2020)
Expenses: need to purchase a category
Balance: Income (milk + culling + cow + calf + heifer) - Expenditure (heifer)
1 dollar = 70 pesos (https://www.lanacion.com.ar/economia/divisas)
The effect of the age category at the first calving on the different variables was evaluated with an analysis of variance and a classification criterion followed by Tukey multiple comparison test. Statistical analyzes were performed using the JMP Program Statistical Discovery from SAS (JMP® 2003) version 5.0 for Windows.
Results
Table 1 shows values of productive and reproductive indicators registered and calculated in the three groups of cows, according to age at first calving.
Table 1 Productive and reproductive indicators of Holstein cows, according to age at first calving
| Age groups at first calving | ||||
|---|---|---|---|---|
| Variables | Early 24 months | Ideal 27 months | Late 32 months | |
| Actual data | EPP (days) | 749 ± 0.32a | 840 ± 0.31b | 982 ± 0.87c |
| VPT (days) | 2.001 ± 66a | 2.212 ± 87ab | 2.368 ± 87b | |
| IPPp (days) | 566 ± 26.6a | 625 ± 38.3a | 532 ± 26.7a | |
| PTL (liters) | 25.961 ± 1.653a | 30.080 ± 2.059a | 32.150 ± 2.290a | |
| IL (liters) | 12.4 ± 0.45a | 12.9 ± 0.50a | 12.8 ± 0.57a | |
| Calculated data | DP(VPT-EPP) days | 1.252 | 1.372 | 1.386 |
| NP(DP/IPPp) +1 | 3 | 3 | 4 | |
| PL (PLT/NP) liters | 8.082 | 9.414 | 8.918 | |
All values correspond to the arithmetic mean ± standard error
Sample size, n = 50 cows per group
a, b, cValues with different letters differ by at least 0.05 for comparisons among age groups at first calving (Tukey multiple comparison test)
PTL: total production of liters during its life
VPT: total productive life
IPPp: mean calving interval
EPP: age at first calving
DP: actual productive days
PN: number of calvings
PL: production per lactation
IL milk index
Groups were obviously differentiated by their EPP (classification criterion). Out of the remaining variables, only statistically significant differences (P <0.05) were observed for VPT. Table 2 summarizes the results of economic analysis. Cows in the late calving age group had higher incomes. This group had more births, fewer suitable heifers, and required less replacement.
Table 2 Economic calculation, according to cow category for a model of 100 cows with the analyzed indicators
| Groups | Early 24 months | Ideal 27 months | Late 32 months | |
|---|---|---|---|---|
| Model for 100 cows | Total PL (liters)1 | 808,247 | 941,412 | 891,752 |
| Births2 | 45 | 29 | 55 | |
| Born females3 | 23 | 15 | 28 | |
| Constant | Percentage of losses4 | 4 | 3 | 5 |
| Actual females5 | 19 | 12 | 23 | |
| Percentage of suitable females6 | 98 | 85 | 66 | |
| Definitive heifers | 18 | 10 | 15 | |
| Replacement7 | 33 | 33 | 25 | |
| Heifers to be replaced8 | -15 | -23 | -10 | |
| Incomes | Milk9 | 15.437.513 | 17.98.0971 | 17.032.460 |
| Culled cow10 | 998.250 | 998.250 | 756.250 | |
| Calves11 | 145.137 | 93.552 | 174.863 | |
| Heifers12 | 0 | 0 | 0 | |
| 16.580.900 | 19.072.773 | 17.963.573 | ||
| Expenditures13 | Heifers | 1.780.348 | 2.733.856 | 1.229.687 |
| Balance14 | 14.800.551 | 16.338.917 | 16.733.886 |
Results are compared per row
1. PL (liters): PL * 100 cows
2. Births: estimate of births adjusted to one year, according to Magnasco (1998)
3. Born females: births / 2, the result of which was rounded towards the female
4. Percentage of losses (Hailiang Zhang et al. 2019)
5. Actual females: born females - 18% losses (from birth to first calving)
6. Suitable females: suitable females for replacement. The amount of 24 months was estimated as the expected optimum time (Krpalkova et al. 2017). As values moved away, it was calculated as (value of EPP of each group in months * 100) / 24 months as optimal value (Marini et al. 2018).
7. Replacement: 100 cows / (NP * 100)
8. Missing or surplus heifers: replacement - suitable females
9. Milk: total PL * price of milk liter paid to the farmer. Price of a milk liter paid to the farmer $ 19.10 (Mercado de Liniers 2020)
10. Culled cow: (weight of culled cow * replacement) * price per kg of culled cow. Discard cow weight: 550 kg. Price of a kilogram of culled cow $ 55 (Mercado de Liniers 2020)
11. Calf: calf weight * price per kg of calf. Calf weight: 80 kg at weaning. Price per kilogram: $ 80 (Mercado de Liniers 2020)
12. Heifers: number of heifers * heifer price $ 120,000 (Mercado de Liniers 2020)
13. Expenses: need to purchase a category
14. Balance: Income (milk + culling + cow + calf + heifer) - Expenditure (heifer)
15. 1 dollar = 70 pesos (https://www.lanacion.com.ar/economia/divisas)
Discussion
Although health and animal welfare, together with sustainability and low input use, are necessary elements for current dairy production, during the last decades. In the case of dairy cows, the goal of maximizing individual yield of milk and early pregnancy of heifers has been pursued (Horn et al. 2012).
With the use of group criterion, according to age at first calving, and considering the entire productive life of cow, it was observed that there were no differences among groups for the variables analyzed, with the exception of total productive life. However, after modeling three establishments, 100 cows each, their annual projection based on the evaluated indicators and the new derived variables, the highest incomes corresponded to the group of late age at first calving, despite the fact that they are comparatively similar in level of production and reproductive efficiency regarding the two remaining groups, although they present greater longevity (greater number of calvings). This performance evidenced the set of variables that are not usually taken into consideration when using pre-established economic calculations, which only consider income from milk sale.
Although the highest proportion of income (94%) comes from milk sale, there are other components that contribute to the final result, such as sale of culled cows (5%) and sale of male calves (1.7%). Furthermore, a proportion of total income may be represented by the sale of surplus heifers, which is not presented in any of the three modeled cases.
Analyzing the variables with the greatest impact, fitting the analysis to a calendar year, as in this case, the first variable that arises is the calving interval. Meanwhile, for each month of delay in calving date, the impact on income is 8%, due to the lower number of annual births. This result agrees with what several authors suggest, who show that changes in the calving interval are directly reflected on production costs (Freitas et al. 2002, Marques et al. 2002, Giordano et al. 2012 and Galvao et al. 2013).
Losses that occur from birth to first calving, which mean fewer heifers to generate gains from milking or selling, were not an evaluated indicator, so their value (18%) came from other published studies. A study in the United Kingdom concluded that 15% of female calves born live never reached the first lactation, and only 19% of them had one parturition (Brickell et al. 2009 and Brickell and Wathes 2011). Any heifer that dies or is slaughtered before calving, means a financial problem, as long as that involuntary outlay is not recovered, and must be covered by the income obtained in another area to equalize the loss (Boulton et al. 2017).
The third factor is the age at first calving, which would impact on final result by 4% for each month of delay in the first calving due to the lower number of heifers available to replace, increase the stock or sell.
The previous information agrees with Lemos et al. (1992), who referred that the age at first calving is an index of reproductive efficiency due to its relationship with sexual precocity, which marks the beginning of the productive life of a dairy female and, therefore, has obvious economic significance. Its importance is linked to the impact on replacement costs.
Lastly, cow longevity should be mentioned, expressed in number of calvings. The decrease in a calving would represent between 5 and 30% of annual replacement and, consequently, a smaller number of heifers available for sale.
Shafer (2006) argued that farmers have known, for a long time, that cow longevity is an important piece of the profitability puzzle. Lopes et al. (2009), after analyzing the influence of different zootechnical indices on composition and evolution of dairy herds over the years, concluded that the calving interval has the greatest influence, and is followed by age at first calving and mortality rate.
Results of this study coincide with previous studies carried out by Marini and Oyarzabal (2002b), for whom the highest milk production would not be enough to guarantee higher income. They also agree with reports of Marini et al. (2018), which showed that economic efficiency of groups of Holstein cows is not only determined by milk production, but by other variables such as longevity and reproduction.
These results also coincide with those published by Horn et al. (2012). According to these authors, a decrease in milk production does not necessarily lead to lower earnings, if it is accompanied by increased longevity. The economic advantage of longevity lies primarily in retaining productive cows for as long as possible. And it ensures, in turn, that less productive cows are replaced as soon as possible, from an economic point of view (Rogers et al. 1988).
According to Rogers et al. (1988), the reduction of involuntary slaughter causes replacement costs to be reduced and production to increase, due to a lower frequency of low-yielding cows, and a longer productive life of high-yielding cows.
Although the presented analysis is not a traditional economic balance, it demonstrated the influence of different indicators that, despite their ease of recording, are not always valued. It is emphasized that global productive efficiency of a dairy farm is not always related to milk production, but to the performance of other variables, related to reproductive field and longevity, that is, to the adaptation of cows to specific conditions of the grazing system.
For grazing-based systems, it would be helpful to have cows that, as defined by Mancuso (2017), produce the highest amounts of solids from the lowest amounts of financial and physical inputs, with the ability to walk and graze, with the aptitude for be milked with a minimum of labor and greater reproductive efficiency. This type of animal would allow the genuine growth of dairy herds, with better inclusion of heifers to the herd, without involuntary culling, an essential aspect for sustainability of this type of establishment.
Conclusions
The inclusion of productive-reproductive indicators, such as the calving interval, rearing efficiency, age at first calving and longevity, all of which can be easily recorded in an elementary model that exceeds the simple consideration of milk production, makes it possible to evaluate its impact on the final economic result, and enables technical and managerial decision making, which tend to improve profitability of dairy farms from a systemic perspective.
