Tall fescue as an alternative to timothy fed with or without alfalfa to dairy cows.

Tall fescue might be an alternative to timothy in northeastern North America because of its tolerance of recurring drought periods and its good summer regrowth, but is not always considered as an option in dairy rations because of its possible lack of palatability. The objective of this study was to evaluate the effects on the performance of lactating dairy cows of (1) replacing timothy silage by tall fescue silage, offered as sole forage in the diet or in combination with alfalfa silage, and (2) feeding tall fescue as silage (35% dry matter, DM) or haylage (55% DM). Experimental diets with a forage-to-concentrate ratio of 70:30 were (1) 100% timothy silage (TS); (2) 100% tall fescue silage (TFS); (3) 55:45 timothy:alfalfa silages (TS + AS); (4) 55:45 tall fescue:alfalfa silages (TFS + AS); and (5) 100% tall fescue haylage (TFH). Fifteen Holstein cows in mid-lactation (5 fitted with a rumen fistula) were randomly assigned to treatments in a triple 5 × 5 Latin square design with treatment periods of 21 d. Preplanned contrasts were timothy versus tall fescue silages, sole grass species versus grass-alfalfa, interaction between sole grass species and grass-alfalfa, and TFS versus TFH. Grass species did not affect dry matter intake (DMI) or milk yield and fat concentration. Milk protein concentration was not affected by grass species when offered in combination with alfalfa, but it was higher with the TS diet than the TFS diet when offered as sole forages. Adding alfalfa to either tall fescue or timothy silage resulted in greater DMI and milk yield, but lower milk fat concentration, than when the grass silages were the sole forage in the diet. The molar proportion of propionate in the rumen was greater when cows were fed diets with tall fescue silage compared with timothy silage, which resulted in a lower acetate-to-propionate ratio. Milk fat concentrations of fatty acids from microbial origin, namely branched-chain fatty acids, were greater when grass silage, and especially timothy silage, were fed as sole forages rather than with alfalfa silage. Feeding TFH rather than TFS caused a decrease in DMI and tended to lower milk protein concentration, but did not affect milk yield. A more fibrolytic fermentation profile was observed in rumen of cows fed TFH compared with TFS, as indicated by the increase in the molar proportion of acetate and the higher acetate-to-propionate ratio in rumen fluid, and a concomitant increase in branched-chain fatty acid concentration in milk fat. Tall fescue as silage or haylage is a valuable alternative to timothy silage for lactating dairy cows.

Richard AM ，Gervais R ，Tremblay GF ，Bélanger G ，Charbonneau É ... -  《-》

Effects of harvest date and grass species on silage cell wall components and lactation performance of dairy cows.

This study evaluated the effect of harvest date and forage species on the concentration of hydroxycinnamic acids in silage and its relationship to dairy cow performance. Tall fescue and timothy were harvested at a regular date on June 27 and July 8, respectively, or at a late date on July 8 and 25, respectively, in the first regrowth. Forage was treated with a salt-based additive and ensiled in hard-pressed round bales. Forty-seven lactating dairy cows were used in a block design. Cows received 1 of 4 treatments: (1) tall fescue harvested at regular date (RTF), (2) timothy harvested at regular date (RTI), (3) tall fescue harvested at late date (LTF), and (4) timothy harvested at late date (LTI). Diets were formulated to have the same forage-to-concentrate ratio (46:54 on a dry matter basis). Harvesting at late date increased fiber components, but only for timothy, where LTI contained greater neutral detergent fiber, acid detergent fiber, and acid detergent lignin concentrations than the other silages. Concentrations of hydroxycinnamic acids were affected by forage species, where concentrations of esterified ferulic acid and p-coumaric acid were greater for tall fescue silages than for timothy silages. Cows fed the RTI diet showed the greatest intakes of dry matter, organic matter, and crude protein. Feeding diets containing timothy silages increased milk yield and energy-corrected milk yield compared with tall fescue diets when averaged over harvest dates. Cows fed the RTI diet had greater milk protein yield than cows fed the RTF and LTF diets, and milk lactose yield was greater for cows fed diets containing timothy silage compared with tall fescue silage when averaged over harvest dates. Cows fed the LTF diet showed greater urinary N excretion compared with the LTI diet, but RTI showed the lowest urinary N and urea N excretions when calculated as percent of N intake. Cows fed diets containing timothy silage excreted more uric acid than cows fed tall fescue diets. Allantoin excretion was greater for cows eating the RTI and LTI diets compared with cows eating the RTF diet. Cows fed the RTI diet had a greater estimated microbial N flow and a greater excretion of hippuric acid than the RTF and LTF groups. In conclusion, besides the effect of harvest date on increasing the fiber components of timothy, concentrations of hydroxycinnamic acids were mainly affected by forage species; consequently, milk production was only affected by forage species. This indicates that hydroxycinnamic acids, such as ferulic acid, which cross-links to glucuronoarabinoxylans, was a major factor regulating milk production of cows fed tall fescue- and timothy silage-based diets, where lower hydroxycinnamic acid concentrations were responsible for greater milk yield.

Sousa DO ，Murphy M ，Hatfield R ，Nadeau E ... -  《-》

Effects of grass species and harvest date on cell wall components and feed efficiency of dairy cows.

There is a balance between DM yield and feed value when choosing types of grasses on a farm depending on the acreages of farmland and types of ruminants to be fed. Therefore, optimisation of the harvest strategy for grass silage is important for profitable dairy farming. Tall fescue has high DM yield and can replace traditional grasses, such as timothy, in Northern Europe in a changing climate as it has been shown to be more drought tolerant. As differences in climate responses previously have been related to differences in cell wall structure between grass species and, consequently, in digestibility, it is highly relevant to compare these species at similar maturity stages and to investigate if a very early harvest date will diminish potential differences between the species. This study evaluated the effects of harvest date and forage species on the concentration of hydroxycinnamic acids in silages and its relationship to feed efficiency of dairy cows. Tall fescue and timothy were harvested at very early date on May 25 or at early date on May 31 in the spring growth cycle. Forty lactating dairy cows were used in a block design. Cows received 1 of 4 treatments: (1) tall fescue harvested at very early date, (2) timothy harvested at very early date, (3) tall fescue harvested at early date, and (4) timothy harvested at early date. Diets were formulated to have the same forage-to-concentrate ratio (49:51 on DM basis). Tall fescue silages showed greater concentrations of DM, ash, and CP than timothy silages. Grasses harvested at early date showed greater concentrations of NDF, ADL, and cell wall than grasses harvested at very early date. Tall fescue silages showed greater concentration of p-coumaric acid and lower in vitro organic matter digestibility (IVOMD) compared to timothy silages. Milk production and composition were not affected by treatments but cows fed tall fescue-based diets showed lower milk protein yield and greater milk urea nitrogen than when timothy-based diets were fed. Furthermore, cows receiving timothy-based diets showed greater feed efficiency compared to cows receiving tall fescue-based diets. Thus, the lower concentration of p-coumaric acid and the higher IVOMD was associated with greater feed efficiency of cows fed timothy-based diets compared to tall fescue-based diets.

Sousa D ，Murphy M ，Hatfield R ，Nadeau E ... -  《-》

Methane production, nutrient digestion, ruminal fermentation, N balance, and milk production of cows fed timothy silage- or alfalfa silage-based diets.

The objective of this study was to investigate the effects of changing forage source in dairy cow diets from timothy silage (TS) to alfalfa silage (AS) on enteric CH₄ emissions, ruminal fermentation characteristics, digestion, milk production, and N balance. Nine ruminally cannulated lactating cows were used in a replicated 3 × 3 Latin square design (32-d period) and fed (ad libitum) a total mixed ration (TMR; forage:concentrate ratio of 60:40, dry matter basis), with the forage portion consisting of either TS (0% AS; 0% AS and 54.4% TS in the TMR), a 50:50 mixture of both silages (50% AS; 27.2% AS and 27.2% TS in the TMR), or AS (100% AS; 54.4% AS and 0% TS in the TMR). Compared with TS, AS contained less (36.9 vs. 52.1%) neutral detergent fiber but more (20.5 vs. 13.6%) crude protein (CP). In sacco 24-h ruminal degradability of organic matter (OM) was higher for AS than for TS (73.5 vs. 66.9%). Replacement of TS with AS in the diet entailed increasing proportions of corn grain and bypass protein supplement at the expense of soybean meal. As the dietary proportion of AS increased, CP and starch concentrations increased, whereas fiber content declined in the TMR. Dry matter intake increased linearly with increasing AS proportions in the diet. Apparent total-tract digestibility of OM and gross energy remained unaffected, whereas CP digestibility increased linearly and that of fiber decreased linearly with increasing inclusion of AS in the diet. The acetate-to-propionate ratio was not affected, whereas ruminal concentration of ammonia (NH₃) and molar proportion of branched-chain VFA increased as the proportion of AS in the diet increased. Daily CH₄ emissions tended to increase (476, 483, and 491 g/d for cows fed 0% AS, 50% AS, and 100% AS, respectively) linearly as cows were fed increasing proportions of AS. Methane production adjusted for dry matter intake (average=19.8 g/kg) or gross energy intake (average=5.83%) was not affected by increasing AS inclusion in the diet. When expressed on a fat-corrected milk or energy-corrected milk yield basis, CH₄ production increased linearly with increasing AS dietary proportion. Urinary N excretion (g/d) increased linearly when cows were fed increasing amounts of AS in the diet, suggesting a potential for higher nitrous oxide (N₂O) and NH₃ emissions. Efficiency of dietary N use for milk protein secretion (g of milk N/g of N intake) declined with the inclusion of AS in the diet. Despite marked differences in chemical composition and ruminal degradability, under the conditions of this study, replacing TS with AS in dairy cow diets was not effective in reducing CH₄ energy losses.

Hassanat F ，Gervais R ，Massé DI ，Petit HV ，Benchaar C ... -  《-》

Utilization of kura clover-reed canarygrass silage versus alfalfa silage by lactating dairy cows.

Kammes KL ，Heemink GB ，Albrecht KA ，Combs DK ... -  《-》