Comparison between two Norwegian cattle breeds only fed on roughage

Liv Lønne Dille

Occasionally, there are claims that old cattle breeds with a moderate milk performance potential are better adapted to an extensive feeding regime than breeds selected for high milk yields.

The main objective of this study was thus to compare the two Norwegian cattle breeds Norwegian Red (NRF) and Sided Trønder and Nordland (STN) with regard to milk performance, milk quality, body weight changes, feed efficiency, health and fertility traits in early lactation in a feeding regime of ad-lib access to grass/clover silage and about ½ kg of hay per day.

The trials were performed at the Animal Production Experimental Centre of the Norwegian University of Life Sciences (UMB). Nine NRF and nine STN cows were jointly kept under the same physical conditions in a loose-housing system. The cows were selected to ensure that the mean calving date and lactation number were the same for each of the two groups. Measurements started at calving and were terminated after about 100 days of lactation. In the beginning, the cows were fed roundbale grass/clover silage (3rd cut), and in the latter part of the trial, they were fed grass/clover silage (1st cut) from a tower silo. Throughout the entire experimental period, silage quality was excellent, with an average energy concentration of about 1.0 FEm and a crude protein content of 160 g per kg DM.

Preliminary results show that both breeds ingested large quantities of roughage. The total daily DM intake was 17.8 kg for the NRF cows and 13.6 kg for STN. There was a large difference in live weight between the two breeds: whereas NRF cows averaged 585 kg, the STN cows had an average weight of 455 kg. Measured per kg body weight or metabolic body weight, there was no significant difference in the intake of neutral detergent fibre (NDF) between the breeds. Daily milk yields averaged 26.3 kg for NRF and 16.1 kg for STN, a difference that was statistically significant. However, the STN cows gave milk with significantly higher contents of fat, protein and lactose than the NRF cows. For protein, the difference between breeds was 0.2 percentage points (3.33 % vs. 3.11 %). There was nevertheless a considerable and significant difference in the daily yield of energy-corrected milk (ECM); 25.4 kg for NRF and 16.3 for STN. Due to this difference in milk performance, the NRF cows produced significantly more milk protein, fat and lactose than the STN cows. In the course of the trial period, the NRF cows showed a weight loss of 475 g per day, while the STN cows gained an average of 60 g per day.

Analyses of fatty acid composition in milk fat of the two breeds show small and non-significant differences for most fatty acids. The milk protein fractions were also analysed, but as of writing, the results are not available.

Feed conversion and feed efficiency can be calculated in different ways. A commonly used measure is total efficiency, calculated as the total production of ECM per kg ingested DM or FEm. Total efficiency (kg ECM/kg ingested DM) was significantly higher for the NRF cows (1.44) than for the STN group (1.17). The difference remained even when taking the difference in live weight between breeds into consideration, i.e., when calculating ECM performance per kg metabolic body weight. Nitrogen efficiency, measured as the ratio between nitrogen discharge in milk and total nitrogen intake from feed, was also significantly higher for the NRF (30 %) than for the STN cows (24 %). It can be argued that part of the extra ECM yield of the NRF cows is due to breakdown of body tissue. Thus, if one calculates feed efficiency (%) or FEm/kg ECM under consideration of the energy derived from body tissue breakdown in the NRF cows, there were merely small, non-significant differences between the two breeds.

With only nine cows in each test group, it is not possible to make significant statements on health and fertility trait differences between the breeds. In each group, one cow was treated for milk fever, whereas three NRF and two STN cows were treated for mastitis. There are indications that STN had slightly better fertility than the NRF cows. However, all test data are still being processed for final publication.

Updated: 14.05.09
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