1.1 Introduction.
Organic market in wealthy countries is experiencing dramatic growth since 1990s. For instance, according to Swedish EPA by the year 2021 country is required to produce 75% of milk in organic way (Cederberg&Mattson 2000). Consumers demand safe, good quality food, which production does not harm the environment and respects animal welfare. System which seems to correspond with all these requirements is organic farming which has potential to lower the environmental impact from agricultural activities (Boer, 2003). On the other hand, critical reviews about organic systems outline the fact that the environmental impact per unit of area is lower, however impact per product unit might be even higher (Tuomisto et al.
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2012). The reason for that is lower yield coming from organic production, requirements to build fertility of soil and more land required to produce the same amount of food (Meier et al. 2015; Tuomisto et al. 2012). The fodder of livestock consists of crops and crops products which are converted into high-nutritional food for people. Particularly ruminants are able to consume very wide range of products, including these once, which are not available for humans. However, a significant part of many livestock diets are raw materials such as cereals or pulses, potentially human-edible feeds, which conversion by dairy cows presents low efficiency (Ertl&Knaus, 2015; Wilkinson, 2011).
It creates a concern especially in the context of growing population and competition for the resources and arable land. Dairy sector will be able to provide demanded amount of products only by increasing the feed efficiency of the animals (Arndt et al., 2015; Wilkinson 2011). In 2030 the demand for animal products will be higher by 50% comparing to the year 2000, while milk consumption is expected to be doubled by the year 2050 (Noya et al., 2018; Wagenberg et al., 2017).
The livestock production is challenged to increase the productivity and decrease the environmental impact at the same time (Wagenberg et al., 2017). One of the agricultural activities which causes the most concerning multiple side effects after meat is milk production (Noya et al., 2018). According to Guerci et al. (2013) feed efficiency was the parameter which presented the most significant negative correlation to the categories such as: „global warming”, „acidification” and „eutrophication” (Guerci et al., 2013).
Another aspect which should be taken under consideration if it comes to the feed efficiency is the total cost of milk production in which the cost of feed for dairy cows plays the main role (Fry, 2011). However, in dairy sector feed is considered mostly from nutritional point of view and the monitoring of feed efficiency in dairy cows is new comparing to the other livestock systems (Fry, 2011; Korver, 1988). 1.2 Objectives.The aim of this article is to analyze differences in feed conversion rate and feed efficiency between organic and conventional dairy herds and determine which system is more sustainable in terms of feed efficiency; outline the importance of feed efficiency in the milk production in terms of environmental changes; present changes needed in the dairy management which can improve feed efficiency in dairy herds. 1.3 Hypothesis.
Organic dairy herds are characterized by higher feed efficiency than cows in conventional systems due to better herd management. 2. Methods.This report was based on the literature research. Sources, such as scientific articles, reports and recommendations for dairy farmers were searched in journal databases, subject specific professional websites and newspaper databases.
Articles that compared organic and conventional milk production; explained feed efficiency or feed conversion rate in the dairy herds, were analyzed. Terms used when searching for articles: “organic milk production”, “conventional milk production”,”organic vs conventional milk production”, “feed conversion rate”, “feed efficiency”, “feed conversion efficiency”, “feed efficiency in dairy herds”, “cows’ nutrition”, “dairy farming”, “environmental impact” and similar. Articles must have been directly related to the topic which means they had to concern milk production with special focus on the feed efficiency and differences between organic and conventional dairy production in terms of feed efficiency.
Most of the articles were not older than 10 years.3. Results.3.1 Feed Conversion Rate and Feed Efficiency.
Term „feed efficiency” should not be used as synonymous to „production efficiency”. Monitoring of the efficiency might be a useful breeding tool, it might help to create new management strategies, such as diet, and it enables to keep herd’s health under control (Berry&Crowley, 2013). There are different possibilities to define efficiency. The most common expression used in the non-ruminant livestock systems is Feed Conversion Rate, FCR, defined as „animal’s efficiency of converting feed to productive body weight mass” (Fry, 2011; Wilkinson, 2011). According to Wilkinson (2011) animal product output can be presented, for instance, as: average daily weight gain, liquid milk yield, edible energy and edible protein (Wilkinson, 2011). On the other hand, feed intake may be measured as: total input of crude protein (CP), metabolisable energy (ME), dry matter (DM) or edible protein and edible energy (Wilkinson, 2011). , Hall (2011) proposes to calculate it as: „amount of dry matter intake required to make a pound of butterfat and milk” (Hall, 2011).
In this way of calculating FCR the higher value of FCR, the lower efficiency of the conversion (Wagenberg et al. 2017). Achieving FCR 1.0 or lower means that the livestock produces more edible energy or protein that it consumes and, if it comes to the milk production, bigger proportion of feed goes into milk instead of body growth or maintenance (circulation, respiration etc.) (Wilkinson, 2011; VandeHaar et al., 2016). However, very low values of the rate may also appear when the consumed forage and by-products are ignored and not included into assessments.
In such situation, actual efficiency is underestimated (Wilkinson, 2011). This way of calculating FCR creates also another problem in the milk production. The research of Wilkinson (2011) outlines the fact that the feed conversion rate for milk presents very low values and it is hard to compare it with the rate of ruminant and non-ruminant meat production.
Table 1 presents total and edible input per unit of output comparison between milk, pig meat and upland suckler beef. As it can be seen, FCR for all feed dry matter of milk stands at 1.1, whereas the pig meat presents FCR of 3.
6 and the global value for non-ruminant meat is 3.8 (Galloway et al. 2007; Wilkinson, 2011).
High value for upland suckler beef, 27.5, might be correlated with the high proportion of grass in the feed used in production (Wilkinson, 2011). Differences could be also observed in terms of edible concentrate FCR.
Edible concentrate FCR shows the proportion of cereal grains and edible feeds in the concentrate mix (Wilkinson, 2011). Only milk presents the value (~ 0.1) which was lower than 1.0, which means that the output of milk was higher than the concentrate input (Wilkinson, 2011).
The reason of that is a low amount of dry matter per kg fresh weight and since the final product consists mostly of water (87% of milk) FCR is very low (Fry, 2011; Wilkinson 2011). FCR values between milk and meat would differ from each other only slightly when the comparison is made per unit of energy and per unit of protein in the edible product. Tab 1.: Total and edible input per unit of output, FCR. (Wilkinson, 2011)Total feed protein conversion rate for milk is greater than the other values of FCR: 5.6 kg of protein in the cows’ feed is needed to produce 1 kg of protein in milk. It indicates that proteins from the feed are used inefficiently to produce edible protein in the final product and it creates one of the biggest challenges for the animal nutritionists (Wilkinson, 2011).
Low proportion of grain in the feed was the cause of the lower edible energy rate in milk, 0.47, comparing to the values presented by CAST (1999), 0.93.
In the case of edible feed protein conversion ratio, value is lower than 1.0, which means more edible protein was produced than consumed (Wilkinson, 2011). To overcome the problem with low FCR due to the low dry matter content in milk, dairy sector adopted the inverse calculation of FCR- feed efficiency. Often referred to dry matter efficiency (DME), it is calculated as pounds of milk produced divided by dry matter consumed (Fry, 2011; Hutjens, 2012). Contrary to FCR, the higher value of DME, the more efficient is the animal (Fry, 2011).
Measure of feed efficiency in lactating animals is also more complicated than in growing animals, which are characterized by the linear phase of growth. Cows present so called „lactation cycles”, which contain periods of rapid catabolism and anabolism (Berry, Crowley, 2013). Due to that DME may differ as cows move through the lactation curve (Fry, 2011). If the stage of lactation, genetics, season and breed are taken under consideration, more accurate measurement of feed efficiency would be energy corrected dry matter efficiency, which means adjusting milk to standardized protein and butterfat content (ECM, energy corrected milk) (Fry, 2011).
3.2 Feed efficiency in the organic and conventional dairy systems.Feed conversion rate or feed efficiency is a new way to monitor dairy herds. Therefore, not much of data has been found especially in the terms of comparison between organic and conventional milk production. For instance, Wagenberg et al. (2017) compared conventional and organic livestock production based on 3 sectors: economic, social and environmental sustainability. Economic pillar was related to the productivity aspects and one of the indicators was FCR.
FCR was used to compare organic and conventional production of: fattening pigs, broilers and laying hens; and was calculated in the way proposed by Wilkinson (2011): „animal’s efficiency of converting feed to productive body weight mass”, which means lower values were preferable (Wilkinson, 2011). Conventional systems presented lower value of FCR comparing to the organic system, feed in conventional groups was used in more efficient way. Comparison of organic and conventional milk production did not include the FCR indicator.However, few other researches, which the goal was to investigate the influence of e.g diet, genetics, management on the feed efficiency in dairy cows, have been found.
It enabled to present the values of feed efficiency in conventional and organic dairy herds, compare them and draw conclusions which system seems to be more sustainable if it comes to the feed conversion rate. In the researches of VandeHaar (1998,2016), Sehested et al. (2003) and Kristensen&Mogensen (1999) inverse calculation of FCR- feed efficiency- was used, therefore the higher presented value, the more efficient is the animal.In the research of VandeHaar (1998,2016) few management changes were proposed to improve the feed efficiency of the cows. One of them was to increase the average daily milk production by 10% which supposed to surge the efficiency by ~0.
7% (VandeHaar 1998). Research made by Thomassen et al. (2008) shows that the milk yield in the conventional dairy farms is 40% greater than the yield from the organic farms. Taking into account the effects suggested by VandeHaar (1998) and data presented by Thomassen et al. (2008) it might be expected that conventional dairy farms with higher milk yield are more sustainable for the environment since the higher productivity increases efficiency (Thomassen et al. 2008, VandeHaar 1998, 2016). Different findings brings the research of Sehested et al.
(2003) which compared the effects of reducing concentrate intake to organic dairy cows on milk production and efficiency. Three groups were investigated, group with no supplementation, L, and normal supplementation, N, were presented in the table 2.Tab. 2.: Milk production efficiency in winter periods in two groups with different concentrate level (Sehested et al. 2003).
As it can been seen in table 2 the milk production decreases with lower level of concentrate, whereas the feed efficiency increases and the highest feed efficiency was observed in the group with 0% of concentrate. The level of concentrate is correlated negatively with the feed efficiency of the animal, which means the more concentrate is used in the fodder the worse feed efficiency cow presents. It might lead to the conclusion that organic milk production, with lower level of concentrate (about half comparing to the conventional system (Rosati,&Aumaitre, 2004)) presents better feed efficiency comparing to the conventional herds (Rosati&Aumaitre, 2004; Sehested et al.
, 2003). This deduction is compatible with the result of VandeHaar (1998) about the protein overfeeding. In the model VandeHaar (1998) outlined that the most significant effect in increasing the lifetime protein efficiency of cows (by ~1.
3%) is diet with 2% less protein (VandeHaar, 1998). The reason of that is low overall efficiency of dietary protein conversion (Wilkinson, 2011). As it can been seen in table 1, the conversion rate for protein in milk production is 5 times greater than total feed dry matter conversion rate, which means 5 times more protein is consumed that produced (Wilkinson, 2011).Kristensen&Mogensen (1999) collected data from organic and conventional herds in Denmark between years 1990 to 1993. In the organic dairy cattle production clover grass was the most significant protein and energy source.
Feed efficiency was investigated to measure the effect of feeding, management and production practices. Table 3 presents the feed efficiency and differences in the feeding strategies in organic and conventional dairy cattle herds. Class variables such as housing, farming system and breed were taken under consideration. As it can been seen in table 3, lower level of concentrates in the organic system resulted in lower energy intake, whereas the percentage of the roughage intake was 10% higher in the organic herd. The feed efficiency was higher by almost 3% in the organic herds compared to the conventional groups in all three ways of measuring the efficiency (Kristensen&Mogensen, 1999).
Level of feed intake and high number of calvings were also correlated negatively with the efficiency of the animal. (Kristensen&Mogensen, 1999). Therefore lowering the feed intake, increasing the calving interval and proper feeding management during calving period might be the way to improve feed efficiency (Kristensen&Mogensen, 1999).
The aim of the research of Guerci et al. (2013) was to analyze the environmental impact of 12 dairy farms in Denmark, Germany and Italy, among which two danish farms were organic (DK-1, DK-2).Tab. 4.: Characteristics of the studied dairy farms in Denmark (DK), Germany (GER), Italy (IT) (after Guerci et al., 2013) Table 4 presents characteristics of mentioned farms.
The feed efficiency (here, in terms of feed conversion rate; lower values are preferable) of two organic Danish farms had lower values than the feed efficiency of three conventional Danish herds. Obviously, also the level of concentrate was lower in organic farms, what once again confirms findings of Sehested et al. (2003) about reduction of concentrate intake. The lowest value, 0.82, was presented by the Italian conventional farm where the confinement feeding was one part of management (Guerci et al. 2013).
The negative correlation between feed intake and feed efficiency was confirmed in the research of Kristensen&Mogensen (1999); lower feed intake was proposed as a solution to improve the feed efficiency of cows (Kristensen& Mogensen, 1999). 3.3 Improvements in feed efficiency. The major challenge in terms of feed conversion rate is to obtain more edible protein and energy than the livestock consumes (Wilkinson, 2011). Feed efficiency is mostly influenced by nutrition, management, physiological state, environmental factors and genetic ability (Korver, 1988, VandeHaar et al.
2016). Genetic selection for high yielding herds improved considerably feed conversion efficiency (Arndt et al. 2015). For instance, over past 100 years feed efficiency in US dairy sector has more than doubled (VandeHaar et al.
2016). However, as Arndt et al. (2015) suggests, it will not be the perfect solution for the future due to the loss of digestible energy and high rate of passage in high yielding cows (Arndt et al.
2015). Moreover, the knowledge about genetic aspects of nutrient utilization is based mostly on the experimental herds (in which it is feasible to measure intake of individual cow) and not on the field trials or milk-recording programs (Korver, 1988). According to Hall (2011) there are few aspects which are able to improve the feed efficiency, such as proper management of rumen acidosis or overall ration digestibility.
Good quality forage minimizes the feed out losses (Hall, 2011). Various management changes which increase the feed efficiency were proposed in the paper of VandeHaar (1998), as follows: reducing feed use; lowering age of first calving; increasing lifetime productivity. The most significant effect could be achieved by avoiding overfeeding cows with proteins (VandeHaar, 1998). The increase of productivity seems to be a questionable solution, since Berry&Crowley (2013) underline the fact that „feed efficiency” can not be understood as „production efficiency”, and this statement was proved in few other researches were the feed efficiency was correlated negatively with productivity (Guerci et al., 2013; Kristensen&Mogensen, 1999; Sehested et al. 2003).
Kristensen&Mogensen (1999) point out the organic system, as a way to improve the feed conversion rate in dairy cows. According to their research, organic feeding and feed ratio used in organic herds lead to better efficiency than in conventional milk production (Kristensen&Mogensen, 1999). Efficiency of dairy cattle depends on the net energy intake. Increased level of cell wall substances in the feed reduces digestibility. This reduction in digestibility may be compensated by lowering losses of energy in urine and methane (Kristensen&Mogensen, 1999). Also Wilkinson (2011) gives importance to the diet and proposes reducing the amount of cereal grain, soya bean meal in feeds and most importantly, the substitution of concentrate by forage.
Such practice is commonly use in organic systems, where currently minimum 60% of good quality forage is required (Tame, 2009). 4. Discussion.
As many researches showed, feed efficiency is still comparatively new way of monitoring herd in dairy production (Berry&Crowley, 2013; Fry, 2011; Hutjens 2012; Wilkinson, 2011). However, the usefulness of it is gaining the importance and several researches, investigating the feed efficiency in dairy organic and conventional farms, have been found.In the research of Kristensen&Mogensen (1999) conventional and organic dairy systems were compared directly in terms of feed efficiency. According to the results organic herds presented better feed efficiency by almost 3%. Also in the research of Guerci et al. (2013), where the environmental impact of the dairy farms in three different countries was investigated, Danish organic farms presented lower feed conversion rate than the Danish conventional systems.
Sehested et al. (2003) monitored the feed efficiency in the groups with different level of concentrate in feed. The amount of concentrate in feed was correlated negatively with the feed efficiency and the highest feed efficiency was obtained in the group with 0% concentrate. It might lead to the conclusion that organic herds with significantly lower level of concentrate would be characterized by better feed efficiency than the conventional dairy cows. Only VandeHaar (1998) claimed that higher herd productivity leads to the higher feed efficiency, which would suggest that high productive conventional herds would be more efficient than the organic systems with lower productivity.
However, what has to be keep in mind, according to Berry&Crowley (2013), the feed efficiency is not equivalent with production efficiency, therefore findings of VandeHaar (1998) seem to be questionable. Tab. 5.: Managements improving feed efficiency in dairy production and systems in which they are practiced (own elaboration).Interesting conclusions might be drawn from the researches about the improvement of feed efficiency.
Table 5 presents changes in management which improve the feed efficiency in dairy herds and systems in which these practices are used. Almost all proposed changes are currently used in organic systems. Aspects such as: importance of forage, avoiding protein overfeeding, decreasing feeding ration, higher calving intervals were pointed out as a method to increase feed efficiency of animals (Guerci et al.
, 2013; Hall, 2011; Kristensen&Mogensen, 1999; Sehested et al. 2003; Wilkinson, 2011; VandeHaar 1998). 5.
Conclusion.In terms of growing population, food shortages and increasing demand for animal products, with the strong emphasis on dairy products, it is crucial to understand the importance of feed efficiency of animals. As it was mentioned by Berry&Crowley (2013) measuring the feed efficiency in lactating animals is difficult and complex, however it is a very useful tool to monitor the herd (Berry&Crowley, 2013).Due to the limited amount of data it is not feasible to establish fully which dairy system, conventional or organic, is more sustainable if it comes to feed efficiency. Nevertheless, taking under consideration researches which have been described in the paper and summed up in table 5, especially researches concerning possible improvement in feed efficiency, we might conclude that organic dairy system with its all management requirements is more feed efficient than the conventional milk production.
This case needs further investigation within the herds from the same countries since the feed efficiency may also vary depending on location, environment and genetic factors (Korver, 1988, VandeHaar et al. 2016).
