Superestructura

L. Mogensen and T. Kristensen

Danish Institute of Agricultural Sciences, Department of Agroecolocy, Research centre Foulum, PO Box 50, DK-8830 Tjele, Denmark

Abstract

Since the summer of 2001, 100% organically grown feed has been a requirement from the majority of the dairy industry in Denmark. This has increased focus on homegrown feed. In the present paper the consequences of different types of supplement feed (cereal, rapeseed/cereal, rapeseed cake/cereal or grass pellets) and of different production systems (increased grazing, increased grazing combined with spring calving or an increased calving interval) were investigated at farm level. Type of supplement feed should be chosen based more on crop yield potential than on milk yield potential. Alternative production systems like spring calving or increased calving intervals have the potential of increasing both productivity and financial result on an organic dairy farm.

Keywords: dairy, feed production, production system, self-sufficiency, whole farm

Introduction

Today, organic herds produce 10% of the milk delivered to dairies in Denmark. The organic herds are in general larger than the conventional ones (93 cows versus 77 cows) and mainly housed in loose-housing systems (94% versus 61% of the conventional herds). However, milk production per cow per year is about 8% lower in organic than in conventional herds (Danish Holstein: 8,065 versus 8,736 kg ECM). A lower level of feeding may explain the lower milk production in organic herds. The principles and standards in organic farming have as a result that feeding of the organic dairy herd is very different from feeding of the conventional dairy herd. Within the organic system, crop yields higher in roughage than in crops for concentrated feed have increased focus on roughage even more than in the conventional system. Grass- clover covers 43% of the area in rotations on organic dairy farms and makes up more than half the total energy intake of the cows during the summer period, and in the winter period grass-clover silage covers an average of 62% of the total roughage intake. It is also a characteristic that the organic dairy cows are given large amounts of cereals, 922 SFU/cow/year as an average.

Milk production based entirely on organically grown feed was introduced in the summer of 2001 because of a requirement from the majority of the dairy industry in Denmark. Most farmers tried to maintain the feeding level and milk yield per cow after introducing 100% organically grown feed (Mogensen, 2004). The proportion of roughage in the ration was typical increased, as was the proportion of grass-clover in whole crop silage. Cereal supplement was typically increased as well. The aim of the present paper is to describe the consequences for productivity and financial result on organic dairy farms using different strategies for homegrown feed.

Materials and methods

A fixed farm size (200 ha in rotation) is assumed for all strategies. All farms are self- sufficient with feed and manure, but straw and minerals can be imported. In each strategy the size of the herd depends on the actual feed production on the 200 ha. The herd includes only cows and heifers as bull calves are sold as young. The size of the stable is adjusted to the actual herd size, and capacity cost is a fixed amount per cow, 8,000 DKK/cow/year. All fieldwork is done by machine pool at standard costs. Land is paid with an interest rate of 3,000 DKK/ha. The financial result is the balance for paying the owner for the work in the stable.

Milk yield response of different types of supplement is based on results from production experiments on private, organic farms (Mogensen & Kristensen, 2002; Mogensen & Kristensen, 2003; Mogensen et al., 2004) and the milk yield from cows on increased calving interval is based on results from an experiment at the organic research station Rugballegård (Christiansen & Danfær, 2005).

Results

Preliminary calculations of strategies with an increasing share of grass-clover in the crop rotation and feed ration showed a positive effect on feed intake and milk production per cow, as well as on the financial result of the farm (Mogensen, 2004). The reason for this is that crop yield potential (SFU/ha) in grass-clover is high. Furthermore, the digestibility of grass- clover silage is often higher than the digestibility of whole crop silage. In the present strategies, the share of grass-clover in rotation is high – 60% of the area. If the share of grass- clover is increased further, it may result in a reduction in yield .

In the basic strategy (No 1 in Table 1), supplement for cows in early lactation consists of 6 kg cereals per day. The roughage is based solely on high quality grass-clover silage with a digestibility of organic matter of 78.5%. During the summer, cows are at pasture for 185 days eating a total of 1,500 SFU fresh grass-clover supplied with silage and cereals at the stable. The milk production is 8,000 kg ECM per cow per year.

Table 1. Effect of different types of supplement feed and different production system

Strategy Type of supplement Production system

1 Cereal Rapeseed 2 cake/cereal 3 Rapeseed/ cereal 4 Grass pellets 5 Increased grazing 6 Spring calving 7 Increased calving interval Cow level SFU/cow/year 6143 6190 6278 5996 6143 6141 6302 ECM/cow/year, kg 8000 8070 8193 7781 8000 7874 8206 Herd level No of cows 124 109 120 130 123 131 130 Gross margin/cow/year, DKK 10246 10315 10513 9729 10247 9950 10737 Field level Ha/cow 1.62 1.84 1.67 1.54 1.62 1.52 1.54 SFU/ha 4739 4202 4690 4886 4730 4915 4774 Grass-clover, % of ha 59 54 59 60 59 64 59 Gross margin/ha/year, DKK 2770 2230 2675 2995 2825 3190 2820 Farm level ECM/ha/year 4946 4392 4918 5049 4937 5168 5325 Financial result, 1000 DKK 232 120 238 219 243 285 304

To grow the said ration, 59% of the area is grown with grass-clover and the remaining part with cereals. In strategy 1, crop yield in grass-clover is assumed to be 5,600 SFU/ha (6,040 kg dry matter) and 3,500 SFU/ha (3,680 kg) of cereals. Given the feed ration per cow and crop yield in actual crops, the area needed to grow the ration is 1.62 ha/cow (Table 1). On 200 ha, feed for 124 cows can be grown. The manure production is 181 kg N/milk producing unit (MPU)/year. 72 kg N is secreted at pasture and the remaining part for spreading amounts to 59 kg N per ha. The total milk production of the herd is 990,000 kg ECM or 4,946 kg ECM/ha. With a milk price of 2.51 DKK/kg ECM and an internal cost of feed of 1.20 DKK/SFU, the resulting gross margin is 10,246 DKK/cow/year. Similar gross margin of the fields is 2,770 DKK/ha/year. The financial result is 232,000 DKK.

In strategy 2, the supplement for high yielding cows during the winter period is 2.5 SFU from rapeseed cake and 3.5 SFU from cereals. Even though milk yield of high yielding cows is increased during the winter, milk yield per cow per year is only increased by 1%. As the financial result is almost halved, it is not attractive to grow rapeseed to produce own rapeseed cakes and sell oil. With a yield of 2,000 kg rapeseed per ha, only 1,500 SFU of rapeseed cakes can be produced. Therefore, there is only feed for 109 cows and milk production per ha decreases.

In strategy 3, once again rapeseed and cereals are grown for supplement feed. When srapeseeds are rolled and fed together with cereals the productivity and financial results are very similar to strategy 1 with supplement of cereals. The assumption is that crop yield in cereal and rapeseed both are 3,400 SFU/ha.

With supplement of grass pellets in strategy 4, feeding level/cow and therefore milk production per cow decreases due to a higher fill of grass pellets when compared with cereals. Higher crop yield in grass-clover compared with cereals increases number of cows that can be fed from the crop production at the 200 ha. Despite the fact that milk production is increased compared with strategy 1, the financial result is decreased because of the costs connected with having more cows.

The level of grazing of 1,500 SFU grass-clover/cow/year used in strategies 1 to 4 corresponds to the average level in Danish organic dairy herds. The level of grazing is increased to 1,700 SFU/cow/year in strategy 5 and to 1,950 SFU/cow/year in strategy 6. In strategy 6, spring calving is introduced at the same time, to synchronize a high demand for feed of cows in early lactation with the maximum grass growth in the springtime. Feeding level is the same in strategies 1, 5 and 6. Milk production per cow per year is 8,000 kg ECM in strategies 1 and 5, but decreases to 7,870 in strategy 6. This is because of the fact that heifers are only 24 months at calving compared with 27.3 months in the other strategies. As these heifers are smaller at calving they have to grow more in 1st lactation and milk production is reducedbecomes lower. In strategy 5, the financial result is 5% higher than in strategy 1, mainly because of saved costs when more feed is grazed and less is ensiled. In strategy 6 with spring calving, share of grass-clover, both fresh and silage, is increased as well as share of grass-clover in rotation. Because grass-clover has the highest expected crop yield, the total feed production is increased. So is total number of cows, total milk production and financial result by 23%. In strategy 7 with an increased calving interval of 17.5 months the total milk production is 11,500 kg ECM from 475 days in milk. That corresponds to 8,206 kg ECM/cow/year. The 56 days dry per lactation is reduced to 38 days dry/cow/year. Only 0.7 calf/cow/year is born versus 1.0 in the other strategies. With increased calving interval there is fewer days/cow/year

in early lactation. Therefore, the share of roughage in the ration/cow/year can be increased. At the same time, the total need for fsome feed for heifers is lowersaved as fewer heifers per cow are produced. So, even though the milk production/cow is increased the need for feed/MPU is decreased. The financial result is increased by 30%.

Discussion and conclusions

In a situation with entirely home produced feed, different type of supplement feed result in almost similar productivity and economic result. This is on the assumption that the milk yield response from supplement rich in protein is lower than the response traditionally used (Madsen et al. 2003). A ration with a high proportion of easily digestible clover-grass silage and plenty of fermentable carbohydrates may stimulate the microbial protein synthesis in the rumen, and the utilization of the digestible protein in rumen may reach a higher level of amino acids absorbed from the small intestine (AAT) than calculated. Furthermore, it is assumed that a ration based solely on cereal and grass-clover does not affect cows health negatively.

Alternative production systems like spring calving or increased calving intervals have the potential of increasing both productivity and financial result on an organic dairy farm. Increased level of grazing presumes that the farm has the right conditions, and concentrated spring calving implies increased focus on reproduction. In the system with increased calving interval is assumed that health, and involuntary replacement are unaffected.

References

Christiansen, H.C., A. Danfær and J. Sehested (2005). Koens reaktion på forskelle i planlagt kælvningsinterval og energiforsyning. In: T. Kristensen (eds.) Økologisk

mælkeproduktion. DARCOF Report 20, 13-26.

Madsen, J., Misciattelli, L., Kristensen, V.F. & Hvelplund, T. 2003. Proteinforsyning til malkekøer. In: Strudsholm, F. & Sejrsen, K. (Eds.) Kvægets ernæring og fysiologi Bind 2 - Fodring og produktion. DJF rapport Husdyrbrug nr. 54. 113-132.

Mogensen, L. (2004). Organic milk production based entirely on home-grown feed. Ph.D thesis, The Royal Veterinary and Agricultural University, Copenhagen, 158 pp. Mogensen, L. and T. Kristensen (2002). Effect of barley or rapeseed cake as supplement to

silage for high-yielding organic dairy cows. Acta Agric. Scand., Sect. A, Animal Sci., 52:4, 243-252.

Mogensen, L. and T. Kristensen (2003). Concentrate mixture, grass pellets, fodder beets, or barley as supplements to silage ad libitum for high-yielding dairy cows on organic farms. Acta Agric. Scand., Sect. A, Animal Sci., 53: 4, 186-196.

Mogensen, L., K.L. Ingvartsen, T. Kristensen, S. Seested and S.M. Thamsborg (2004).

Organic dairy production based on rapeseed, rapeseed cakes, or cereals as supplement to silage ad libitum. Acta Agric. Scand., Sect A, Animal Sci., 54, 81-93.

Acknowledgements

This project was a part of the project “Organic dairy production systems“ funded by the research program “Research in organic farming 2000-2005 (DACOF II)”.