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 ... -  《-》

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 replacing grass silage with forage pearl millet silage on milk yield, nutrient digestion, and ruminal fermentation of lactating dairy cows.

This study investigated the effects of dietary replacement of grass silage (GS) with forage millet silages that were harvested at 2 stages of maturity [i.e., vegetative stage and dough to ripe seed (mature) stage] on milk production, apparent total-tract digestibility, and ruminal fermentation characteristics of dairy cows. Fifteen lactating Holstein cows were used in a replicated 3 × 3 Latin square experiment and fed (ad libitum) a total mixed ration (60:40 forage:concentrate ratio). Dietary treatments included control (GS), vegetative millet silage (EM), and mature millet silage (MM) diets. Experimental silages comprised 24% of dietary dry matter (DM). Soybean meal and slow-release urea were added in millet diets to balance for crude protein (CP). Three additional ruminally fistulated cows were used to determine the effect of treatments on ruminal fermentation and total-tract nutrient utilization. Cows fed the GS diet consumed more DM (22.9 vs. 21.7 ± 1.02 kg/d) and CP (3.3 vs. 3.1 ± 0.19 kg/d), and similar starch (4.9 ± 0.39 kg/d) and neutral detergent fiber (NDF; 8.0 ± 0.27 kg/d) compared with cows fed the MM diet. Replacing the EM diet with the MM diet did not affect DM, NDF, or CP intakes. Cows fed the MM diet produced less milk (26.1 vs. 29.1 ± 0.79 kg/d), energy-corrected milk (28.0 vs.30.5 ± 0.92 kg/d), and 4% fat-corrected milk (26.5 vs. 28.3 ± 0.92 kg/d) yields than cows fed the GS diet. However, cows fed diets with EM and GS produced similar yields of milk, energy-corrected milk, and 4% fat-corrected milk. Feed efficiency (milk yield:DM intake) was greater only for cows fed the GS diet than those fed the MM diet. Milk protein yield and concentration were greater among cows fed the GS diet compared with those fed the EM or MM diets. Milk fat and lactose concentrations were not influenced by diet. However, milk urea N was lower for cows fed the GS diet than for those fed the MM diet. Ruminal NH3-N was greater for cows fed the EM diet than for those fed the GS diet. Total-tract-digestibility of DM (average = 66.1 ± 3.3%), NDF (average = 55.1 ± 2.4%), CP (average = 63.6 ± 4.2%), and gross energy (average = 64.5 ± 2.6%) were not influenced by experimental diets. We concluded that cows fed GS and EM diets had comparable performance, whereas milk yield was significantly reduced with the MM diet, likely because reduced intakes of DM and net energy for lactation.

Brunette T ，Baurhoo B ，Mustafa AF 《-》

Replacing corn silage with different forage millet silage cultivars: effects on milk yield, nutrient digestion, and ruminal fermentation of lactating dairy cows.

This study investigated the effects of dietary replacement of corn silage (CS) with 2 cultivars of forage millet silages [i.e., regular millet (RM) and sweet millet (SM)] on milk production, apparent total-tract digestibility, and ruminal fermentation characteristics of dairy cows. Fifteen lactating Holstein cows were used in a replicated 3 × 3 Latin square experiment and fed (ad libitum) a high-forage total mixed ration (68:32 forage:concentrate ratio). Dietary treatments included CS (control), RM, and SM diets. Experimental silages constituted 37% of each diet DM. Three ruminally fistulated cows were used to determine the effect of dietary treatments on ruminal fermentation and total-tract nutrient utilization. Relative to CS, RM and SM silages contained 36% more crude protein, 66% more neutral detergent fiber (NDF), and 88% more acid detergent fiber. Cows fed CS consumed more dry matter (DM; 24.4 vs. 22.7 kg/d) and starch (5.7 vs. 3.7 kg/d), but less NDF (7.9 vs. 8.7 kg/d) than cows fed RM or SM. However, DM, starch and NDF intakes were not different between forage millet silage types. Feeding RM relative to CS reduced milk yield (32.7 vs. 35.2 kg/d), energy-corrected milk (35.8 vs. 38.0 kg/d) and SCM (32.7 vs. 35.3 kg/d). However, cows fed SM had similar milk, energy-corrected milk, and solids-corrected milk yields than cows fed CS or RM. Milk efficiency was not affected by dietary treatments. Milk protein concentration was greatest for cows fed CS, intermediate for cows fed SM, and lowest for cows fed RM. Milk concentration of solids-not-fat was lesser, whereas milk urea nitrogen was greater for cows fed RM than for those fed CS. However, millet silage type had no effect on milk solids-not-fat and milk urea nitrogen levels. Concentrations of milk fat, lactose and total solids were not affected by silage type. Ruminal pH and ruminal NH3-N were greater for cows fed RM and SM than for cows fed CS. Total-tract digestibility of DM (average=67.9%), NDF (average=53.9%), crude protein (average=63.3%), and gross energy (average=67.9%) were not influenced by dietary treatments. It was concluded that cows fed CS performed better than those fed RM or SM likely due to the higher starch and lower NDF intakes. However, no major differences were noted between the 2 forage millet silage cultivars.

Brunette T ，Baurhoo B ，Mustafa AF 《-》