This study examined effects on milk yield and composition, milk fatty acid concentrations and methane (CH4) emissions when dairy cows were offered diets containing different amounts of algal meal. The algal meal contained 20% docosahexaenoic acid (DHA) and cows were offered either 0, 125, 250, or 375 g/cow per d of algal meal corresponding to 0, 25, 50, or 75 g of DHA/cow per d. Thirty-two Holstein cows in mid lactation were allocated to 4 treatment groups, and cows in all groups were individually offered 5.9k g of dry matter (DM) per day of concentrates [683 g/kg of cracked wheat (Triticum aestivum), 250 g/kg of cold-pressed canola, 46 g/kg of granulated dried molasses, and 21 g/kg of mineral mix] and ad libitum alfalfa (Medicago sativa) hay. The algal meal supplement was added to the concentrate allowance and was fed during the morning and afternoon milking, whereas the alfalfa hay was fed individually in pens. Cows were gradually introduced to their diets over 7d and then fed their treatment diets for a further 16d. Dry matter intake and milk yield were measured daily, and milk composition was measured on a sample representative of the daily milk yield on Thursday of each week. For the last 2d of the experiment, cows were individually housed in respiration chambers to allow measurement of CH4 emissions. Dry matter intake, milk yield and milk composition were also measured while cows were in the respiration chambers. Cows ate all their offered concentrates, but measured intake of alfalfa decreased with increasing dose of DHA by 16.2, 16.4, 15.1, and 14.3 kg of DM/d, respectively. Milk yield (22.6, 23.5, 22.6, and 22.6 kg/cow per d) was not affected by DHA dose, but milk fat concentrations (49.7, 37.8, 37.0, and 38.3g/kg) and, consequently, milk fat yields (1.08, 0.90, 0.83, and 0.85 kg/d) decreased with addition of DHA. The feeding of algal meal high in DHA was associated with substantial increases in the concentrations of DHA (0.04, 0.36, 0.60, and 0.91 g/100g of milk fatty acids) and conjugated linoleic acid C18:2 cis-9,trans-11 (0.36, 1.09, 1.79, and 1.87 g/100g of milk fatty acids). Addition of DHA did not affect total emissions of CH4 (543, 563, 553, and 520 g/cow per d), nor emissions in terms of milk production (24.9, 22.1, 24.3, and 23.4 g of CH4/kg of milk), but emissions were increased with respect to total intake (22.6, 23.5, 24.5, and 24.4 g of CH4/kg of DM). These findings indicate that CH4 emissions were not reduced when dairy cows were fed a forage-based diet supplemented with DHA from algal meal.

Grape marc (the skins, seeds, stalk, and stems remaining after grapes have been pressed to make wine) is currently a by-product used as a feed supplement by the dairy and beef industries. Grape marc contains condensed tannins and has high concentrations of crude fat; both these substances can reduce enteric methane (CH4) production when fed to ruminants. This experiment examined the effects of dietary supplementation with either dried, pelleted grape marc or ensiled grape marc on yield and composition of milk, enteric CH4 emissions, and ruminal microbiota in dairy cows. Thirty-two Holstein dairy cows in late lactation were offered 1 of 3 diets: a control (CON) diet; a diet containing dried, pelleted grape marc (DGM); and a diet containing ensiled grape marc (EGM). The diet offered to cows in the CON group contained 14.0kg of alfalfa hay dry matter (DM)/d and 4.3kg of concentrate mix DM/d. Diets offered to cows in the DGM and EGM groups contained 9.0kg of alfalfa hay DM/d, 4.3kg of concentrate mix DM/d, and 5.0kg of dried or ensiled grape marc DM/d, respectively. These diets were offered individually to cows for 18d. Individual cow feed intake and milk yield were measured daily and milk composition measured on 4d/wk. Individual cow CH4 emissions were measured by the SF6 tracer technique on 2d at the end of the experiment. Ruminal bacterial, archaeal, fungal, and protozoan communities were quantified on the last day of the experiment. Cows offered the CON, DGM, and EGM diets, ate 95, 98, and 96%, respectively, of the DM offered. The mean milk yield of cows fed the EGM diet was 12.8kg/cow per day and was less than that of cows fed either the CON diet (14.6kg/cow per day) or the DGM diet (15.4kg/cow per day). Feeding DGM and EGM diets was associated with decreased milk fat yields, lower concentrations of saturated fatty acids, and enhanced concentrations of mono- and polyunsaturated fatty acids, in particular cis-9,trans-11 linoleic acid. The mean CH4 emissions were 470, 375, and 389g of CH4/cow per day for cows fed the CON, DGM, and EGM diets, respectively. Methane yields were 26.1, 20.2, and 21.5g of CH4/kg of DMI for cows fed the CON, DGM, and EGM diets, respectively. The ruminal bacterial and archaeal communities were altered by dietary supplementation with grape marc, but ruminal fungal and protozoan communities were not. Decreases of approximately 20% in CH4 emissions and CH4 yield indicate that feeding DGM and EGM could play a role in CH4 abatement.

Milk production responses of grazing cows offered supplements in different ways were measured. Holstein-Friesian cows, averaging 227 d in milk, were allocated into 6 groups of 36, with 2 groups randomly assigned to each of 3 feeding strategies: (1) cows grazed perennial ryegrass pasture supplemented with milled barley grain fed in the milking parlor and pasture silage offered in the paddock (control); (2) same pasture and allotment supplemented with the same amounts of milled barley grain and pasture silage, but presented as a mixed ration after each milking (PMR 1); and (3) same pasture and allotment, supplemented with a mixed ration of milled barley grain, alfalfa hay, corn silage, and crushed corn grain (PMR 2). For all strategies, supplements provided the same metabolizable energy and grain:forage ratio. [75:25, dry matter (DM) basis]. Each group of 36 cows was further allocated into 4 groups of 9, which were assigned to receive 6, 8, 10, or 12 kg of supplement DM/cow per day. Thus, there were 2 replicated groups per supplement amount per dietary strategy. The experiment had a 14-d adaptation period and an 11-d measurement period. Pasture allotment was approximately 14 kg of DM/d for all cows and was offered in addition to the supplement. Positive quadratic responses to increasing amounts of supplement were observed for yield of milk, energy-corrected milk (ECM), and fat and protein, and positive linear responses for concentrations of fat and protein for cows on all 3 supplement feeding strategies. No difference existed between feeding strategy groups in yield of milk, ECM, or protein at any amount of supplement offered, but yield and concentration of fat was higher in PMR 2 cows compared with control and PMR 1 cows at the highest amounts of supplementation. Responses in marginal ECM production per additional kilogram of supplement were also greater for PMR 2 than control and PMR 1 cows when large amounts of supplement were consumed. For all diets, marked daily variation occurred in ruminal fluid volatile fatty acids and pH, especially in cows fed the largest amounts of supplement. It was concluded that when supplements are fed to grazing dairy cows, a simple mix of grain and pasture silage has no benefit over traditional strategies of feeding grain in the parlor and forage in the paddock. However, yield of milk fat and marginal milk production responses can be greater if the strategy uses an isoenergetic ration that also contains alfalfa hay, corn silage, and corn grain.

Wheat is the most common concentrate fed to dairy cows in Australia, but few studies have examined the effects of wheat feeding on enteric methane emissions, and no studies have compared the relative potencies of wheat, corn, and barley for their effects on enteric methane production. In this 35-d experiment, 32 Holstein dairy cows were offered 1 of 4 diets: a corn diet (CRN) of 10.0 kg of dry matter (DM)/d of single-rolled corn grain, 1.8 kg of DM/d of canola meal, 0.2 kg of DM/d of minerals, and 11.0 kg of DM/d of chopped alfalfa hay; a wheat diet (WHT) similar to the CRN diet but with the corn replaced by single-rolled wheat; a barley diet (SRB) similar to the CRN diet but with the corn replaced by single-rolled barley; and a barley diet (DRB) similar to the CRN diet but with the corn replaced by double-rolled barley. Individual cow feed intakes, milk yields, and milk compositions were measured daily but reported for the last 5 d of the experiment. During the last 5 d of the experiment, individual cow methane emissions were measured using the SF tracer technique for all cows, and ruminal fluid pH was continuously measured by intraruminal sensors for 3 cows in each treatment group. The average DM intake of cows offered the CRN, WHT, SRB, and DRB diets was 22.2, 21.1, 22.6, and 22.6 kg/d. The mean energy-corrected milk of cows fed the WHT diet was less than that of cows fed the other diets. This occurred because the milk fat percentage of cows fed the WHT diet was significantly less than that of cows fed the other diets. The mean methane emissions and methane yields of cows fed the WHT diet were also significantly less than those of cows fed the other diets. Indeed, the CRN, SRB, and DRB diets were associated with 49, 73, and 78% greater methane emissions, respectively, compared with the emissions from the WHT diet. Methane yield was found to be most strongly related to the minimum daily ruminal fluid pH. This study showed that although the inclusion of wheat in the diet of dairy cows could be an effective strategy for substantially reducing their methane emissions, it also reduced their milk fat percentage and production of milk fat and energy-corrected milk.

For Australian and New Zealand dairy farms the primary source of home grown feed comes from grazed perennial pastures. The high consumption of perennial pasture is a key factor in the low cost of production of Australian and New Zealand dairy systems and hence their ability to maintain international competiveness. The major pasture species used are perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.), normally grown in a simple binary mixture. As pasture production has been further driven by increasing use of nitrogen fertilizer and irrigation, farms are getting closer to their economic optimum level of pasture consumption. Increasing inputs and intensification has also increased scrutiny on the environmental footprint of dairy production. Increasing the diversity of pasture species within dairy swards presents opportunities to further increase the productivity of the feedbase through additional forage production, extending the growing season, improving forage nutritive characteristics and ultimately increasing milk production per cow and/or per ha. Diverse pastures also present an opportunity to mitigate some of the environmental consequences associated with intensive pasture-based dairy systems. A consistent finding of experiments investigating diverse pastures is that their benefits are due to the attributes of the additional species, rather than increasing the number of species per se. Therefore the species that are best suited for inclusion into dairy pastures will be situation specific. Furthermore, the presence of additional species will generally require modification to the management principles of dairy pastures, particularly around nitrogen fertilizer and grazing, to ensure that the additional species remain productive and persistent.