Kismul H.1,2, Eriksson T.1, Höglind M.3, Næss G.2, Spörndly E.1
1Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management; 2Nord University, Department of Business-, Social- and Environmental Sciences; 3Norwegian Institute of Bioeconomy Research; haldis.kismul@nord.no
Abstract
Legislation in Sweden and Norway requires that dairy cattle have outdoor access in summertime. Pasture utilization can be challenging with high yielding cattle and large herd-sizes. Therefore, many farmers choose to offer their cows access to an exercise- and recreation area only, rather than a full production pasture.
However, is an exercise paddock as attractive as production pasture for the cow? We compared part-time production and exercise grazing in an automated milking system, with outdoor access in the morning (4.5 h) and the evening (4 h). The production pasture group (P) was offered fresh production pasture daily (≥15 kg dry matter (DM) cow-1) and given a limited silage ration (6 kg DM) night-time. The exercise pasture group (E) was given access to a small exercise paddock (<1 kg DM cow-1) and were fed silage ad libitum 24 hours. Milk yield did not differ significantly: 36.1 kg for P and 36.0 kg for E. However, behaviour differed (P<0.0001), with 5.5 (P) and 2.6 h (E) spent outdoors, and 3.7 (P) and 0.6 h (E) grazing time. In conclusion, while milk-yields were similar between the groups, lower amounts of supplementary feed were needed for cows on treatment P, who also spent longer hours outdoors and grazing.
Keywords: dairy cows, automatic milking, grazing, restricted grazing, supplements
Introduction
Farmers in conventional dairy systems need to fetch the cattle twice a day for milking, but a cow in an automated milking (AM) system may visit the milking unit as she likes within the framework of the system settings. While the latter system may function very well during the non-grazing season, it may offer some challenges when the access area is extended to include the walkways and pasture. Longer walking distances have been shown to affect milking frequencies (MF) and milk yield (MY) (Spörndly and Wredle, 2004), and may cause the cows to act less independently, synchronizing their visits to the AM unit. This leads to an uneven robot utilization and long waiting hours before milking (Ketelaar-de Lauwere et al., 1999).
Variation in pasture quality and supply can make an adequate feed supplementation difficult.
Following the introduction of pasture legislation in Norway and Sweden, the use of exercise pasture rather than production pasture has become quite common amongst farmers. The argument is often to fulfil the requirement of having cattle on pasture, while not losing production due to sub-optimal feed supply.
Earlier studies (Ketelaar-de Lauwere et al., 1999; Spörndly et al., 2015) have shown promising results when offering the cows restricted access to pasture, indicating that restricted grazing may be a suitable way to combat the above-mentioned challenges in AM systems. A clear pattern of herd movement between pasture and stable was reported from both studies, and in the latter study a preference of staying indoors during the middle of the day, even when no silage was on offer, was found.
The present study compared production pasture with exercise pasture in an AM system with morning and evening grazing. The hypothesis was that a restricted access to production pasture during morning and evening, with restricted silage supplementation at night-time, would give (1) greater utilization of available outdoor time and (2) higher milk yield than restricted access to exercise pasture with 24 h ad libitum silage feeding.
Materials and methods
During a 7 week grazing trial, 41 cows – 22 of the Swedish Red Breed (SR) and 19 Swedish Holstein (SH) – were blocked and randomly assigned into two groups, similarly composed with regard to breed, parity, days in milk (DIM), and milk yield (MY). One group was given access to production pasture (P) and one was given access to exercise pasture (E). A group of non-experimental cows assigned to the P treatment were also included in the herd, to better mimic an AM farming situation with regard to cow numbers.
Treatment P: Cows were offered new pasture daily, at an allowance of ≥15 kg dry matter (DM) cow-1. During night-time, these cows received a restricted grass silage ration (6 kg DM day-1).
Treatment E: Cows had access to the same 0.2 ha field throughout the experiment, with a continuous, low sward height, and low daily allowance (<1 kg DM cow-1), and silage was available ad libitum throughout the 24 h period.
A selection gate at the stable exit directed cows to either E or P pasture areas. Cows in both groups were allowed to move freely between the indoor and outdoor areas for a period of 4.5 h in the morning (06-10.30 h), and 4 h in the evening (16-20 h). The remaining time, they were restricted to the stables. Drinking water and supplementary feed was available indoors for both groups. Silage and concentrates were fed and registered on an individual basis (Table 1). Concentrates were fed according to milk production before the experimental start, with rations adjusted every fortnight according the standardised weekly drop in MY (-0.125 kg week-1 for primiparous, -0.33 kg week-1 for multiparous) used in the Scandinavian feed system ‘NorFor’. A commercial concentrate was offered to all cows, and an additional protein-rich supplement for high yielders, Solid 620 and Unik 82 (Lantmännen, Sweden), respectively.
MY, MF, and supplementary feed intake indoors were registered automatically. The grazing behaviour of all cows outdoors was observed for a full outdoor-access period six times during the experiment. For each individual, location (walkway or pasture/paddock), position (standing or lying), and activity (grazing or other) were registered every 15 minutes.
P pasture height was measured daily, and used to calculate new pasture allowance. Samples of pasture and supplementary feed were collected daily for analysis to determine their nutrient composition. The E pasture was mowed at the lowest possible height prior to experiment start and on two subsequent occasions, leaving virtually no grass available for the cows.
The data were analysed in a mixed model using the SAS programme (ver. 9.4; SAS Institute Inc.). The model for analysis of the production parameter (MY) contained the variables treatment (P or E) and breed (SR or SH), using MY prior to experimental start as a covariate. Parity and DIM were excluded due to lack of significance. In analysis of MF and behaviour, the same model was used.
Results and discussion
The metabolisable energy (ME), dry matter (DM), crude protein (CP), and neutral detergent fibre (NDF) contents of the different feed sources are presented in Table 1.
There was no significant difference in the MY between the two experimental groups (Table 2). There were, however, differences in MF; the cows in the E-group visited the AM unit more frequently than did the cows in P-group. The cows in P-group, on the other hand, spent significantly more time outdoors than the E-group. They also spent a greater amount of time grazing while outdoors, and had a higher
total outdoor lying time. However, relative to the total outdoor time, the E-cows spent a greater fraction of it lying than the P-group.
In conclusion, the results support the hypothesis that cows on P-pasture spend more time outdoors and graze longer hours than cows on E-pasture. The data do not support the second hypothesis, however the results show that it is possible to maintain the same MY with a smaller supplementary feed allowance and an increased pasture ration.
Acknowledgements
The experiment was funded through the Swedish Farmer’s Foundation for Agricultural Research, and The Research Council of Norway.
References
Ketelaar-de Lauwere, C.C., Ipema, A.H., van Ouwerkerk, E.N-J., Hendriks, M.M.W.B., Metz, J.H.M., Noordhuizen, J.P.T.M. and Schouten, W.G.P. (1999) Voluntary milking in combination with grazing of dairy cows. Milking frequency and effects on behavior. Applied Animal Behaviour Science 64, 91-109.
Spörndly, E. and Wredle, E. (2004) Automatic milking and grazing – Effects of distance to pasture and level of supplements on milk yield and cow behavior. Journal of Dairy Science 87, 1702-1712.
Spörndly, E., Andersson, S., Pavard, N. and Le Goc, S. (2015) Production pasture versus exercise pasture for cows in automatic milking systems. Grassland Science in Europe 20, 125-127.
Table 1. Mean ± standard error composition (metabolisable energy (ME), dry matter (DM), crude protein (CP), neutral detergent fibre (NDF)) of feed and pasture, sward height, and intake of supplementary feeds for cows on production (P) or exercise (E) pasture.
Roughages Concentrates
Silage1 P-pasture2 Basal conc. Protein conc.
ME (MJ kg-1 DM) 11.6 (0.05) 10.7 (0.18) 13.2 (0.00) 14.0 (0.00)
DM (g kg-1) 321.0 (0.37) 894.8 (0.18) 889.9 (0.18)
CP (g kg-1) 156.9 (0.67) 161.5 (6.04) 177.8 (1.17) 295.5 (1.12)
NDF (g kg-1) 425 (4.8) 398 (9.2) 282 (4.9) 243 (0.9)
Sward height (cm) 15.8 (0.52)
Consumption P (kg DM) 5.6 (0.01) 8.7 (0.08) 1.7 (0.01)
Consumption E (kg DM) 14.6 (0.45) 8.3 (0.09) 1.7 (0.01)
1 NH4-N, % of total N: 6.4. Acids, g kg-1 DM: lactic acid 75.9, acetic acid 11.8, propionic acid 1.2, butyric acid 0.5, formic acid 1.44.
2 Exercise pasture was not sampled for chemical analysis as there was virtually no grass available to cows on this pasture.
Table 2. Production and behaviour data (mean ± standard error) for cows on production or exercise pasture.
Production Exercise Sign.
Milk Yield1 (kg) 36.1 (0.60) 36.0 (0.60) NS
Milking Frequency1 (n day-1) 2.4 (0.05) 2.7 (0.05) P=0.0004
Outdoor time2 (h) 5.5 (0.13) 2.6 (0.12) P<0.0001
Grazing time2 (h) 3.7 (0.07) 0.6 (0.07) P<0.0001
Lying outdoors2 (h) 1.7 (0.09) 1.4 (0.08) P=0.0079
1 Based on daily robot-recordings over 49 days.
2 Based on 6 observation studies.