Requerimiento Técnico 154

O. Reksen

Norwegian School of Veterinary Science, Department of Production Animal Sciences, PO Box 8146, 0033 Oslo, Norway.

Abstract

The animal welfare aspect is one of the most important trademarks for organic products. The current paper focuses on reproductive performance in dairy cows as a measure of animal welfare. An epidemiological study of organic and conventional dairy farms revealed that energy requirements had not been adequately met to ensure optimal reproductive success in Norwegian organic dairy farming. Characteristics such as herd size, geographical distribution, breeding season, milk yield, parity, breed, and use of artificial insemination (AI) were taken into account in these analyses. Organic grain production is limited in Norway and breeding efficiency proved difficult to maintain among organic cows bred during winter, as these cows could not benefit from pasture during peak lactation. Organic husbandry proved more efficient than did conventional husbandry in converting roughage into milk, and cows in organic husbandry lived longer.

Keywords: Animal, welfare, organic, dairy, reproduction

Introduction

The public tend to associate the term “organic dairy husbandry” with superior management and high standards of animal welfare. This notion is, at least partly, true as low milk production levels might act to reduce production-related diseases such as hypocalcemia and mastitis (Strøm & Olesen 1997) and a low fraction of concentrate in the feed ration can prevent rumen acidosis and abomasal displacement (Goff & Horst 1997), and last but not least, cows in organic husbandry live longer (Reksen et al. 1999).

The animal welfare aspect is one of the most important trademarks for organic products. There are however some areas, which will require attention in order to maintain such high standards. As organic grain production is limited in Norway, a relevant question to ask is whether energy requirements are adequately met during peak lactation in organic cows. An additional constraint on the relationship between energy requirements and energy coverage is expected to take place when feeding of conventional grown concentrate will be prohibited in organic dairy farming from August 28 this year. My own research has focused on the effect of feeding on reproductive performance, and it has been demonstrated that there is room for improvement in organic dairy farming (Reksen et al. 1999).

Material and methods

This is a comparative cohort study of reproductive performance in organic and conventional dairy husbandry conducted using longitudinal data from the Norwegian Dairy Herd Recording during the period from January 1, 1994 to December 31, 1996 (Reksen et al. 1999). The organically managed cohort consisted of 998 lactation periods, and the conventionally managed cohort consisted of 3016 lactation periods. Both groups were similar in herd size and geographical distribution. The data was analysed both in univariate and multivariable analyses. In the latter, characteristics such as breeding season, milk yield, parity, breed, and use of artificial insemination (AI) were taken into account using a repeated measures mixed

model (PROC MIXED) of SAS (Littell et al. 1996). Significance (P<0.05) was assessed by the type III F-test. T-tests were used in the univariate analyses (Altman, 1996).

Results and discussion

Breeding and culling Practices

Univariate analyses revealed that natural breeding, during the period from 1994 to 1996, was used in 19 to 27% of the pregnancies in organic dairy husbandry and in 3 to 5% in conventional husbandry. Annual replacement was 23% in organic and 35% in conventional husbandry. Norwegian Red Cattle comprised 85% of organically managed and 97% of conventionally managed dairy cows. Winter was the main breeding period for conventional husbandry, and summer was the major breeding period for organic husbandry. The results from 1996 are reported in Table 1.

Milk yield and use of concentrate

The daily use of concentrate in the 305-d period after calving was estimated and the energy uptake given in feed units (FEM). One FEM was 6900 KJ net energy. 305-d milk yield was reported in Kg energy-adjusted milk (EKM) (Ekern 1991). Mean 305-day milk yield was significantly lower for organic husbandry than for conventional husbandry (Table 1). Conventionally managed farms used nearly twice as much FEM from concentrate per cow as did organic farms (Table 1). Energy consumption calculated as FEM (from concentrate) per 100 kg milk produced, was 33 % greater in conventional husbandry compared with organic husbandry (Table 1). Thus, organic husbandry proved more efficient than did conventional husbandry in converting roughage into milk.

TABLE 1. Mean calving interval, mean days open, mean interval from calving to first AI, mean energy adjusted 305-d milk yield, mean feed units (FEM) per day from concentrate, mean feed units (FEM) from concentrate/100 kg milk, mean % of cows bred during summer, and mean % of cows bred by natural service, distributed by class of husbandry systems during 1996.

Organic Conventional

Calving interval (days) 369.0* 374.1* Days open (days) 112.8* 130.5* Calving to first AI interval (days) 78.7 80.9 305 day milk yield (kg) 4554* 6040* FEM/day from concentrate 2.4* 5.3* FEM from concentrate per 100 kg milk 18.1* 27.1* Breeding in summer, % 52* 36*

Natural breeding, % 19 4

* Significant difference (P < 0.05) between organic and conventional husbandry assessed by the t-test (Altman, 1996).

Reproductive performance

In the univariate analyses, calving interval was shorter during 1996 in organic husbandry as compared to conventional husbandry (Table 1). The same relationship was found for days open during all three years of the study (Table 1). The interval from calving to first AI was not different between management category for either of the years of study. However, parity and the interaction between season and management (organic / conventional) were significantly related to calving interval, days open and calving to first AI in the multivariable

analyses (Table 2). The effect of the significant interaction term between season and management on the reproductive traits revealed that conventionally managed cows bred during winter showed the better breeding performance, and impaired performance was observed in organically managed cows bred during winter (Table 2). In these analyses level of milk yield, breeding season, service (AI / natural mating), and parity were taken into account. TABLE 2: Least square means of calving interval, days open and calving to first AI interval as predicted by the repeated measurement models (Littell et al. 1996). Significance (P<0.05) was assessed by the type III F-test.

Days open Calving

interval

Calving to AI interval

days P days P days P Breeding season Winter Summer 118.8 117.1 .59 379.0 377.7 .38 81.8 81.3 .67 Management Conventional Organic 116.7 119.2 .47 374.1 382.7 <.01 79.3 83.8 <.01 Parity Primiparous Multiparous 121.3 114.6 .02 383.3 373.4 <.01 84.4 78.7 <.01 Service Artificial Natural 132.1 103.8 <.01 379.3 377.4 .41 Season X management

Winter and conventional husbandry Winter and organic husbandry Summer and conventional husbandry Summer and organic husbandry

112.8 124.8 120.5 113.7 <.01 371.4 386.6 376.7 378.7 <.01 78.3 85.3 80.3 82.4 .03

The energy requirements might not have been fully met during winter, as the cows could not benefit from fresh pasture during peak lactation. Strøm and Olesen (1997) found that the energy requirements during winter were not adequately met in individual organic herds in a Norwegian survey. Hence, breeding in summer might be essential to balance genetic capacity for milk yield and energy needs in organic dairy husbandry in Norway. As breeding in winter would be necessary for year-round delivery of organic dairy products, and some organically managed cows inevitably will attain high milk yields, an improvement of the feeding regimens should be sought.

Conclusion

The current paper focuses on reproductive performance as a measure of animal welfare. Although there is a tendency among the public to associate the term “organic dairy husbandry” with superior management and high standards of animal welfare, there is room for improvement within this production system as the current study indicates that energy requirements had not been adequately met to ensure optimal reproductive success on Norwegian organic dairy farms. This situation will be even more challenged when

conventional grown concentrate will be prohibited in organic dairy farming from August 28 this year.

References

Altman, D.G. (1995). Practical statistics for medical research. 1. Chapman & Hall. London. Ekern, A. (1991). A new system of energy evaluation of food for ruminants. Norsk

Landbruksforskning, 5, 273-277.

Goff, J.P., R.L. Horst (1997). Physiological changes at parturition and their relationship to metabolic disorders. J. Dairy Sci. 80, 1260-1268.

Littell, R.C., G.A. Milliken, W.W. Stroup, R.D. Wolfinger (1996). SAS system for mixed models. SAS Inst., Cary, NC, USA..

Reksen, O., A. Tverdal, and E. Ropstad (1999). A comparative study of reproductive

performance in organic and conventional dairy husbandry. J. Dairy Sci. 82, 2605-2610. Strøm, T. and I. Olesen (1997). Mjølkekvalitet, helse og holdbarhet på kyrne ved omlegging

til økologisk mj¢lkeproduksjon (Milk quality, health and longevity of cows in organic dairy farming). Norsk senter for økologisk landbruk. Tingvoll, Norway.