SAINFOIN SILAGE BENEFITS NITROGEN UTILIZATION, METHANE EMISSION AND MILK YIELD IN DAIRY COWS

Sainfoin (Onobrychis viciifolia) is a legume containing tannins and therefore from a nutritional point of view has potential as some of its protein has by-pass characteristics, and from a health point of view the tannins will prevent bloat when sainfoin is grazed and will reduce nematode larval attachment. These benefits amongst others should improve nitrogen (N) utilization and reduce greenhouse gas emissions (GHG). These benefits to a varying degree have been shown in studies with sheep, but sainfoin as a fodder crop in dairy cow rations has received little attention. As a result, Dr N.T. Huyen and colleagues studied sainfoin silage in dairy cow rations, their results being published in the Journal of Dairy Science, Volume 99 of 2016, pages 3566 to 3577, with the title: Inclusion of sainfoin (Onobrychis viciifolia) silage in dairy cow rations affects nutrient digestibility, nitrogen utilization, energy balance, and methane emissions.                                                                                                                                             

The objective of their study was to evaluate the effect on nutrient digestibility, animal performance, energy and N utilization and methane production when sainfoin silage was included in the ration. Six rumen-cannulated, lactating dairy cows were randomly assigned to either a control or a sainfoin-based diet over two experimental periods of 25 days each in a crossover design. The control diet was a mixture of grass silage, maize silage, concentrate, and linseed. In the sainfoin diet, 50% of the grass silage dry matter (DM) of the control diet was substituted for sainfoin silage. The cows were adapted for a 21-day period before being housed in climate-controlled respiration chambers for four days, during which time feed intake, apparent total-tract digestibility, N and energy balance, and methane production was determined.                                                                                                                                      

The total daily DM, organic matter and neutral detergent fibre intake did not differ between the two diets. The apparent digestibility of DM, organic matter, neutral detergent fibre and acid detergent fibre (two fibre components) were, respectively: 5.7, 4.0, 15.7 and 14.8% lower for the sainfoin diet, which is expected because of the tannins. Methane production per kilogram of DM intake was lower for the sainfoin diet and tended to be lower as a percentage of gross energy intake. Milk yield was greater for the sainfoin diet. Nitrogen intake, N retention and energy retained in body protein were greater for the sainfoin than for the control diet. Nitrogen retention as a percentage of N intake tended to be greater for the sainfoin diet.                                                                                                        

The improved milk yield and nitrogen utilization apparently resulted because the protein by-pass characteristics resulted in more amino acids being absorbed from the small intestine. Although the cows used in the experiment would have been drenched, one can imagine that in practice the toxicity of tannins to nematode larvae will be positive to cow immunity and further absorption of nutrients to the benefit of milk production. Thus, clearly, sainfoin should be considered for pasture-based systems.