Early lactation feed intake and milk yield responses of dairy cows offered grass silages harvested at early maturity stages

The main objective was to evaluate the potential of grass silages of very high quality to support a high milk yield with a low or moderate, or even without concentrate supplementation. Production responses to increased levels of concentrate supplementation with 3 primary growth grass silages differing in digestibility were studied using 66 Norwegian Red dairy cows. Roundbale silage was produced from a timothy-dominated sward at very early (H1), early (H2), and normal (H3) stages of crop maturity. Crops were rapidly wilted (<24h) and a formic acid-based additive was applied. All silages were restrictedly fermented. Silage digestible organic matter in dry matter (DM) values were 747, 708, and 647 g/kg of DM for H1, H2, and H3, respectively. Dietary treatments were fed in a 3×3 factorial arrangement of the 3 silages supplemented with 3 concentrate levels (4, 8, and 12 kg/d) and, additionally, H1 was offered without concentrates and H3 with 16 kg/d, giving a total of 11 diets. Cows, blocked according to parity and calving date, were introduced to the experiment before calving and kept in the experiment until wk 16 of lactation. Silage was offered ad libitum in loose housing and concentrate was available in automatic feed stations. Intake of grass silage when fed as the sole feed was 16.9 kg of DM on average for lactation wk 1 to 16. When H1 was supplemented with 4 or 8 kg of concentrates, silage DM intake did not change, but total DM intake increased to 20.6 and 23.7 kg/d, respectively. Energy-corrected milk (ECM) yield increased from 23.4 kg when H1 was offered without concentrate supplement to 29.1 and 32.8 kg when supplemented with 4 or 8 kg concentrate, respectively. None of the other diets equaled the yield obtained by H1 plus 8 kg of concentrate. Feed intake and yield of cows offered H3 plus 4 kg of concentrates were strongly constrained by high dietary fiber concentration. They consumed 16.5 g of neutral detergent fiber/kg of body weight and spent more time eating silage than cows offered other diets. The highest concentrate level within each silage quality produced similar or lower ECM yield than that with 4 kg less concentrates. The obtained milk yield responses suggest that provision of 8.0, 8.4, and 11.5 kg of concentrates to H1, H2, and H3, respectively, would maximize ECM yield within each silage type. However, H1 may successfully be used with less concentrates, or even without, if future conditions should limit the amount of concentrates available for ruminant production.     

Nitrogen metabolism in rumen and whole digestive tract of lactating dairy cows fed grass silage.

Effects of wilting of grass prior to ensiling on OM intake, ruminal digestibility, efficiency of bacterial protein synthesis, and amount and composition of duodenal N fraction were examined using four lactating Holstein cows. Direct-cut or wilted grass silages were fed for ad libitum intake and supplemented with 5.0 or 5.3 kg of concentrate, respectively. Milk yield was 18.1 and 21.2 kg/d with direct-cut versus wilted silage, and milk protein and fat contents were 2.63 and 4.60% with direct-cut versus 2.75 and 4.27% with wilted silage, respectively. Wilting of the grass (from 17 to 38% DM) increased OM intake but had no effect on ruminal digestibility. Total N flow and amounts of different AA in proximal duodenum were increased, and the difference was principally of bacterial origin. The efficiency of bacterial protein synthesis in rumen was related to dilution rate of liquid phase and to the time devoted to ruminating. These results indicate that the passage of bacterial protein to the lower digestive tract is a key factor for improving the assimilation of the soluble N fraction of grass silage and that this phenomenon is related to chewing activity.     

Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function

Two experiments were conducted to investigate the basis for higher voluntary intakes and increased alpha-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of isobutyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of alpha-linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of alpha-linolenic acid passing through the rumen. This explains the increased recovery of alpha-linolenic acid from feed into milk with diets based on red clover silage.     

Effects of silage species and supplemental vitamin E on the oxidative stability of milk

Two experiments were conducted to study the effects of feeding legume silages and providing supplemental vitamin E in concentrates on the oxidative stability of milk. In experiment 1, six multiparous Holstein-Friesian cows were offered 1 of 6 silage treatments in a cyclical changeover-design experiment, with four 4-wk periods. The silages were grass, red clover, white clover, alfalfa, grass and red clover mixture (50:50 on a DM basis), and grass and white clover mixture (50:50 on a DM basis). In experiment 2, 8 cows were used in a changeover-design experiment with three 4-wk periods. The 4 treatments were a factorial combination of forages (grass silage or red clover silage) and supplemental vitamin E in the form of all-rac-alpha-tocopheryl acetate (29 or 290 IU/kg of DM in the concentrate). All forages were offered ad libitum and a flat rate of concentrates (8 kg/d) was fed in both experiments. Red clover silage led to significantly higher forage intakes, milk yields, and milk protein percentage in experiment 2, which was in agreement with results from experiment 1. There was no effect of vitamin E on feed intake, milk production, or milk fat and protein percentage. Red clover silage also led to significant changes in milk fatty acid profiles, particularly increased levels of polyunsaturated fatty acids. Milk samples were stored at 4 degrees C and 20 degrees C and analyzed for alpha-tocopherol and thiobarbituric acid reactive substances at intervals to determine oxidative stability. Diets based on red clover and alfalfa silages were associated with more rapid loss of alpha-tocopherol and increased production of thiobarbituric acid reactive substances during the storage of milk in comparison with diets based on grass silage. The increased oxidative deterioration of milk produced from cows fed red clover silage was avoided by vitamin E supplementation.     

Fermentation acids, aerobic fungal growth, and intake of napiergrass ensiled with nonfiber carbohydrates

This study evaluated fermentation characteristics and fungal numbers of napiergrass silages prepared with and without added raw or heated corn meal (10%, fresh-weight basis) at ensiling. Corn was added to napiergrass so that the silage would contain concentrate similar to that of corn silage with minimum grain content. The silages treated with raw or heated corn were fed to dairy does to compare voluntary silage consumption. After 8 wk of fermentation, pH for silage treated with heated corn was lowest, and that for napiergrass ensiled alone was highest among the treatments. The addition of corn increased lactic acid, but propionic and butyric acids were also elevated. Acetic acid decreased in response to the supplementation of corn but remained the dominant acid for all silages. Numbers of fungi (yeasts plus molds) in silages did not differ significantly at silo opening or after 24 h of exposure to air. However, the numbers of fungi at 48 h in aerated silages containing corn were lower than were the fungi counts in the control silage. When the silages were offered free choice along with concentrate at a fixed rate, dairy does tended to consume more silage treated with heated corn than raw corn. Whole-tract nutrient digestibility and serum glucose and urea N were not altered. These results indicate that the addition of either raw or heated corn meal to napiergrass at ensiling was beneficial to silage fermentation quality because it decreased pH, increased lactic acid, and apparently suppressed fungal populations via elevated antifungal acids. A further advantage of heated corn vs. raw corn was increased silage intake.     

Forage intake,meal patterns,and milk production of lactating dairy cows fed grass silage or pea-wheat bi-crop silages

This study investigated the feed intake, milk production, and plasma nutrient status in dairy cows fed inter-cropped pea-wheat (bi-crop) silages comprised of contrasting ratios of pea to wheat. Spring peas (cv. Magnus) and wheat (cv. Axona) sown at either high (75:25) or low (25:75) pea inclusion rates were harvested after 13 (Cut 1) or 15 (Cut 2) wk. Eighteen Holstein-Friesian cows between wk 9 and 10 of lactation were used in a cyclical changeover design with three 28-d periods. Cows were fed the bi-crop silages and 6 kg of concentrates or second-cut grass silage supplemented with 6 (GS6) or 9 (GS9) kg/d of concentrates. Forage intakes were higher when bi-crops were fed (10.3 to 11.4 kg dry matter [DM]/d) than when grass silage was fed (8.6 kg DM/d). Total DM intake was similar among cows fed the bi-crop silages and GS9 diets, but intakes for GS6 were at least 1.7 kg DM/d lower. Increasing the pea inclusion rate increased the crude protein (CP) content of the ration, but it did not enhance forage quality or animal performance. The rate of intake of the different forages was similar, so that the higher intakes of bi-crop silages were associated with more time spent at the feedbunk and an increased number of meals. Diet digestibility ranged from 531 to 650 g/kg, and the highest value was given by the Cut 1 bi-crop silage diet. Milk yield tended to be similar for cows fed the Cut 2 bi-crop and GS9 diets, and these values were at least 1.7 kg higher than those for cows fed on other treatments. Generally, the bi-crop diets resulted in higher milk fat contents and lower polyunsaturated fatty acid contents. Milk protein content was highest for cows fed the GS9 diet. Blood metabolite content was unaffected by treatment except for blood urea nitrogen content, which was higher in cows fed the bi-crop silages, reflecting reduced N-use efficiency with these diets. The study showed that pea-wheat bi-crop silages can be used to replace moderate-quality grass silage in dairy cow rations, but their role as alternatives to high-quality forages requires additional investigation.     

In situ degradability of fresh grass and grass conserved under different harvesting methods.

The effects of forage conservation and harvesting method on DM and CP degradability of grass cut at the boot stage were determined using nylon bags incubated in the rumen of two fistulated lactating cows. Samples of fresh grass, wilted grass prior to and after ensiling in a stack silo and cut with either a cylinder-type forage harvester (11.3 mm of length cut) or a self-loading wagon (42.4 mm of length cut), wilted grass prior to and after ensiling in large round bales, and grass hay were obtained from the same field and used for determination of DM and CP degradability. The DM-soluble fraction of fresh grass was significantly lower than that of wilted grass and silage, but it was higher than that of hay. In general, the potentially degradable fraction of all treatments was related inversely to the readily soluble fraction in water. The effective degradability of DM of fresh grass was similar to that of hay but was lower than that of wilted grass and silage. The effective degradability of DM of silage was higher than that of wilted grass and hay. The disappearance rate of CP of fresh grass was similar to that of wilted grass, hay, and silage. Silage had a lower disappearance rate of CP than wilted grass. The effective degradability of CP was similar for fresh and wilted grasses. Protein degradability was greater for silages than for fresh and wilted grasses. Protein degradability of hay was similar to that of fresh grass and wilted grass.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of red clover and ryegrass silage for dry cows and influence on subsequent lactation performance

The objective of this study was to investigate the use of red clover (RC) silage as a forage for dry dairy cows, primarily relative to its impact on tissue mobilization and repletion during the transition period and performance during the first 10 wk of lactation. Forty multiparous lactating Holstein-Friesian dairy cows were divided into 2 paired groups at 70 d before predicted calving dates; a subset (n = 8) of the cows were used for N and P balance measurements twice during the study. From the start of the experiment until 4 wk before predicted calving date all cows were offered ad libitum access to a ryegrass (RG) silage with no concentrate. At 4 wk before predicted calving date, one group of cows remained on the same diet, and the other group was changed to a diet of ad libitum access to RC silage. There was no difference in feed intakes, but CP intake was higher in cows fed RC silage, whereas ME intake was higher in cows fed RG silage. Cows fed RG silage gained more weight over the last 4 wk of the dry period (DP) than those fed RC silage, but there was no treatment effect on BCS. During the DP fecal N excretion was higher for cows fed RC silage, and there were no treatment differences in urine N excretion or overall N balance. At birth, calves from cows fed the RC silage were heavier. After calving, all cows were offered the same diet of ad libitum access to the same RG silage and a standard lactation concentrate. During the first 10 wk of lactation there was no difference in feed intake between the 2 previous treatment groups, and feed intake reached a maximum at approximately 4 wk of lactation. Cows on the RG treatment during the DP gained more longissimus dorsi muscle depth during the DP and retained it during early lactation. Mobilization of this muscle occurred before calving, indicating repartitioning of amino acids to other body tissues. There were no carryover effects of DP treatment on apparent partitioning of N from diet to milk, urine, or feces at wk 3 of lactation. Feeding RC silage during the DP had almost no impact on subsequent performance of dairy cows in early lactation, probably because the 2 silages were nutritionally very similar.     

Food intake, milk production, and tissue changes of Holstein-Friesian and Jersey × Holstein-Friesian dairy cows within a medium-input grazing system and a high-input total confinement system

Although interest in crossbreeding within dairy systems has increased, the role of Jersey crossbred cows within high concentrate input systems has received little attention. This experiment was designed to examine the performance of Holstein-Friesian (HF) and Jersey × Holstein-Friesian (J × HF) cows within a high concentrate input total confinement system (CON) and a medium concentrate input grazing system (GRZ). Eighty spring-calving dairy cows were used in a 2 (cow genotype) × 2 (milk production system) factorial design experiment. The experiment commenced when cows calved and encompassed a full lactation. With GRZ, cows were offered diets containing grass silage and concentrates [70:30 dry matter (DM) ratio] until turnout, grazed grass plus 1.0 kg of concentrate/day during a 199-d grazing period, and grass silage and concentrates (75:25 DM ratio) following rehousing and until drying-off. With CON, cows were confined throughout the lactation and offered diets containing grass silage and concentrates (DM ratio; 40:60, 50:50, 40:40, and 75:25 during d 1 to 100, 101 to 200, 201 to 250, and 251 until drying-off, respectively). Full-lactation concentrate DM intakes were 791 and 2,905 kg/cow for systems GRZ and CON, respectively. Although HF cows had a higher lactation milk yield than J × HF cows, the latter produced milk with a higher fat and protein content, so that solids-corrected milk yield (SCM) was unaffected by genotype. Somatic cell score was higher with the J × HF cows. Throughout lactation, HF cows were on average 37 kg heavier than J × HF cows, whereas the J × HF cows had a higher body condition score. Within each system, food intake did not differ between genotypes, whereas full-lactation yields of milk, fat plus protein, and SCM were higher with CON than with GRZ. A significant genotype × environment interaction was observed for milk yield, and a trend was found for an interaction with SCM. Crossbred cows on CON gained more body condition than HF cows, and overall pregnancy rate was unaffected by either genotype or management system. In summary, milk and SCM yields were higher with CON than with GRZ, whereas genotype had no effect on SCM. However, HF cows exhibited a greater milk yield response and a trend toward a greater SCM yield response with increasing concentrate levels compared with the crossbred cows.     

Comparison of grass and legume silages for milk production. 1. Production responses with different levels of concentrate

Silages prepared from pure stands of ryegrass, alfalfa, white clover, and red clover over two successive year were offered to lactating dairy cows in two feeding experiments. Proportional mixtures of all cuts prepared in a yr were used to ensure that the forage treatments were representative of the crop. Additional treatments involved mixtures of grass silage with either white clover silage or red clover silage (50/50, on a DM basis). Silages were prepared in round bales, using a biological inoculant additive, and wilting for up to 48 h. Although the legumes were less suited to silage-making than grass, because of their higher buffering capacity and lower water-soluble carbohydrate content, all silages were well-fermented. A standard concentrate was offered at a flat-rate (8 kg/d in yr 1, and 4 or 8 kg/d in yr 2). All of the legume silages led to higher DM intake and milk yields than for the grass silage, with little effect on milk composition. Intake and production responses to legumes were similar at the two levels of concentrate feeding and with forage mixtures they were intermediate to those for the separate forages. An additional benefit of the clover silages, particularly red clover silage, was the increase in levels of polyunsaturated fatty acids, particularly alpha-linolenic acid, in milk. Legume silages also led to a lower palmitic acid percentage in milk. The efficiency of conversion of feed N into milk N declined with increasing levels of legume silage. White clover silage led to a higher N-use efficiency when the effect of N intake level is taken into account.     

Reducing concentrate supplementation in dairy cow diets while maintaining milk production with pea-wheat intercrops

In the first of 2 experiments, 40 dairy cows were used to evaluate the milk production potential and concentrate-sparing effect of feeding dairy cows a basal diet of pea-wheat intercrop silages instead of perennial rye-grass silage (GS). Dairy cows were offered GS or 2 intercrop silages prepared from wheat and either Magnus peas (MW, a tall-straw variety) or Setchey peas (SW, a short-straw variety) ad libitum. The respective intercrops were supplemented with 4 kg/d of a dairy concentrate (CP = 240 g/kg dry matter; MW4 and SW4), and the GS were supplemented with 4 (GS4) or 8 (GS8) kg/d of the same concentrate. The second experiment measured the forage DM intake, digestibility, rumen function, and microbial protein synthesis from the forages by offering them alone to 3, nonlactating cows (3 x 3 Latin square design with 21-d periods). Forage dry matter intake was greater in cows fed the intercrop silages than those fed GS. Milk production was greater in cows fed SW4 than those fed GS4 or MW4, but similar to cows fed GS8. Dietary treatment did not affect milk fat, protein, or lactose concentrations. The intercrops had greater N retention, and were more digestible than the GS, and these factors probably contributed to the greater forage DM intakes and greater milk production from the intercrop silages compared with the GS. Rumen volatile fatty acid concentrations were similar across forages, but urinary purine derivative excretion was greater in the cows fed the intercrop silages than the GS, suggesting that rumen microbial protein synthesis was enhanced by feeding the intercrops. In conclusion, similar milk yield and milk composition can be obtained by feeding SW and 4 kg of concentrates as that obtained with GS and 8 kg of concentrates. Feeding intercrop silages instead of GS with the same amount of concentrates increased forage intakes, N retention, and microbial protein synthesis.     

Nutritive value of maize silage in relation to dairy cow performance and milk quality

Maize silage has become the major forage component in the ration of dairy cows over the last few decades. This review provides information on the mean content and variability in chemical composition, fatty acid (FA) profile and ensiling quality of maize silages, and discusses the major factors which cause these variations. In addition, the effect of the broad range in chemical composition of maize silages on the total tract digestibility of dietary nutrients, milk production and milk composition of dairy cows is quantified and discussed. Finally, the optimum inclusion level of maize silage in the ration of dairy cows for milk production and composition is reviewed. The data showed that the nutritive value of maize silages is highly variable and that most of this variation is caused by large differences in maturity at harvest. Maize silages ensiled at a very early stage (dry matter (DM) < 250 g kg^?1) were particularly low in starch content and starch/neutral detergent fibre (NDF) ratio, and resulted in a lower DM intake (DMI), milk yield and milk protein content. The DMI, milk yield and milk protein content increased with advancing maturity, reaching an optimum level for maize silages ensiled at DM contents of 300–350 g kg^?1, and then declined slightly at further maturity beyond 350 g kg^?1. The increases in milk (R² = 0.599) and protein (R² = 0.605) yields with maturity of maize silages were positively related to the increase in starch/NDF ratio of the maize silages. On average, the inclusion of maize silage in grass silage‐based diets improved the forage DMI by 2 kg d^?1, milk yield by 1.9 kg d^?1 and milk protein content by 1.2 g kg^?1. Further comparisons showed that, in terms of milk and milk constituent yields, the optimum grass/maize silage ratio depends on the quality of both the grass and maize silages. Replacement of grass silage with maize silage in the ration, as well as an increasing maturity of the maize silages, altered the milk FA profile of the dairy cows, notably, the concentration of the cis‐unsaturated FAs, C18:3n‐3 and n‐3/n‐6 ratio decreased in milk fat. Despite variation in nutritive value, maize silage is rich in metabolizable energy and supports higher DMI and milk yield. Harvesting maize silages at a DM content between 300 and 350 g kg^?1 and feeding in combination with grass silage results in a higher milk yield of dairy cows. © 2014 Society of Chemical Industry     

Effect of concentrate feed level in late gestation on subsequent milk yield, milk composition, and fertility of dairy cows.

The effects of level of concentrate feeding in late gestation on feed intake, milk yield, milk composition, and fertility in the subsequent lactation were evaluated in a randomized block design experiment involving 60 cows. Grass silage was offered ad libitum for the last 28 d of gestation either as the sole diet (OC) or supplemented with 5 kg/d of concentrates (5C). Following calving, the cows were offered the same grass silages supplemented with 7 kg/d of concentrates. For treatments OC and 5C, total dry matter intakes were 9.28 and 11.03 kg/d of dry matter, respectively, during the last 4 wk of gestation. During wk 1 to 12 of the subsequent lactation, treatment 5C increased milk fat concentration but did not alter feed intake, milk yield, or protein concentration relative to treatment OC. Treatment 5C increased the interval to first progesterone rise and the number of services per conception relative to treatment OC. Cow parity, BF depth assessed at d 28 before parturition, and treatment provided the best fit relationships for the yields of fat and fat plus protein (R2 relationships = 0.65 and 0.64, respectively) during wk 1 to 4 of lactation. It was concluded that, other than milk fat concentration, supplementation with additional concentrates in late gestation did not alter milk yield or composition and dairy cow fertility. Furthermore, despite the very large differences in cow characteristics at d 28 before parturition, there was no evidence of any interaction between treatment and specific cow characteristics on animal performance in the first 12 wk of lactation.     

Replacing human-edible feed ingredients with by-products increases net food production efficiency in dairy cows

Global demand for food is increasing, and use of large amounts of potentially human-edible feedstuffs for dairy cows is an important concern. The present study examined whether feeding a by-product-based concentrate combined with high-quality grass silage to high-producing dairy cows affected feed intake and milk production compared with a conventional diet, as well as the effect on efficiency of human food production. In a changeover experiment with four 21-d periods, 24 dairy cows in mid-lactation were offered 9.6 kg of dry matter per day with 1 of 4 concentrates and high-quality grass silage ad libitum. The control concentrate was based on cereal grain (wheat, oat, and barley) and soybean meal, whereas the 3 by-product-based concentrates contained sugar beet pulp in combination with mainly heat-treated rapeseed meal, distillers grain, or a mixture of both. All diets were formulated to be isoenergetic and isonitrogenous. The cows had 10-fold higher starch intake when fed the control diet than when fed the by-product-based concentrates. Silage intake (13 kg of dry matter/d) and milk production (33 kg of energy-corrected milk/d) were not affected by the change in diet. Therefore, replacing cereals and soybean meal with human-inedible by-products in a high-quality forage diet to dairy cows increased net food protein production substantially without lowering milk production.     

Feeding concentrates with different protein sources to high-yielding,mid-lactation Norwegian Red cows: Effect on cheese ripening

Soybean meal is one of the most important protein sources in concentrate feeds for dairy cows. The objective of the present study was to provide knowledge on the effects of using a novel yeast microbial protein source (Candida utilis) in concentrate feed for dairy cows on the production and quality of a Gouda-type cheese. Forty-eight Norwegian Red dairy cows in early to mid lactation were fed a basal diet of grass silage, which was supplemented with 3 different concentrate feeds. The protein source of the concentrates was based on conventional soybean meal (SBM), novel yeast (C. utilis; YEA), or barley (BAR; used as negative control because barley has a lower protein content). The experiment was carried out for a period of 10 wk, with the first 2 wk as an adaptation period where all dairy cows were fed grass silage and the SBM concentrate. The cows were then randomly allocated to 1 of the 3 different compound feeds: SBM, yeast, or barley. Cheeses were made during wk 8 and 9 of the experiment, with 4 batches of cheese made from milk from each of the 3 groups. The cheeses made from milk from cows fed SBM concentrate (SBM cheese) had a higher content of dl-pyroglutamic acid and free amino acids than the other cheeses, indicating a faster ripening in the SBM cheeses. Despite these differences, the sensory properties, the microbiota, and the Lactococcus population at 15 wk of ripening were not significantly different between the cheeses. This experiment showed that although the raw materials used in the concentrate feed clearly influenced the ripening of the cheeses, this did not affect cheese quality. Yeast (C. utilis) as a protein source in concentrate feed for dairy cows can be used as a replacement for soybean meal without compromising the quality of Norwegian Gouda-type cheeses.     

The effect of temperature on ensilage

An experiment was carried out to study the chemical and bacteriological changes during the ensilage of fresh and partially wilted grass at two different temperature levels. In grass of low dry-matter content (15.2%) the effect of increasing the temperature to 42° resulted in a clostridial type fermentation, whereas in similar material kept at 20° a lactic acid fermentation occurred. Differences between the two wilted silages were less marked, although the wilted material at low temperature contained more lactic acid than the high-temperature silage. Results of digestibility trials with sheep did not show any marked variation between treatments, although the digestible crude protein contents were highest in the wet silages. The importance of maintaining low temperatures and of wilting crops prior to ensiling are discussed.     

Concentrate supplementation of a diet based on medium-quality grass silage for 4 weeks prepartum: Effects on cow performance,health, metabolic status,and immune function

Because negative energy balance (EB) contributes to transition-period immune dysfunction in dairy cows, dietary management strategies should aim to minimize negative EB during this time. Prepartum diets that oversupply energy may exacerbate negative EB in early lactation, with detrimental effects on immune function. However, with lower body condition score (BCS) cows, it has been shown that offering concentrates in addition to a grass silage-based diet when confined during an 8-wk dry period resulted in increased neutrophil function in early lactation. The aim of this study was to examine if similar benefits occur when concentrate feeding was restricted to a 4-wk period prepartum. Twenty-six multiparous and 22 primiparous Holstein-Friesian cows were offered ad libitum access to medium-quality grass silage until 28 d before their predicted calving dates (actual mean of 32 d prepartum; standard deviation = 6.4). At this time multiparous cows had a mean BCS of 2.9 (standard deviation = 0.12) and primiparous cows a mean BCS of 3.0 (standard deviation = 0.14) on a 1 to 5 scale. Cows were then allocated in a balanced manner to 1 of 2 treatments (13 multiparous cows and 11 primiparous cows on each treatment): silage only (SO) or silage plus concentrates (S+C) until calving. Cows on SO were offered the same grass silage ad libitum. Cows on S+C were offered an ad libitum mixed ration of the same grass silage and additional concentrates in a 60:40 dry matter (DM) ratio, which provided a mean concentrate DM intake (DMI) of 4.5 kg/cow per d. After calving, all cows were offered a common mixed ration (grass silage and concentrates, 40:60 DM ratio) for 70 d postpartum. Offering concentrates in addition to grass silage during the 4 wk prepartum increased prepartum DMI (12.0 versus 10.1 kg/cow per d), EB (+40.0 versus +10.6 MJ/cow per d), and body weight (BW; 640 versus 628 kg), and tended to increase BCS (3.02 versus 2.97). However, postpartum DMI, milk yield, milk composition, BW change, BCS change, serum nonesterified fatty acid, and β-hydroxybutryrate concentrations, health, and corpus luteum measures were unaffected by treatment. The in vitro assays of neutrophil phagocytosis, neutrophil oxidative burst, and interferon gamma production, conducted on blood samples obtained at d 14 prepartum and d 3, 7, 14, and 21 postpartum, were unaffected by treatment. Primiparous cows had higher phagocytic fluorescence intensity at d 14 prepartum and d 3 and 7 postpartum; a higher percentage of neutrophils undergoing oxidative burst at d 3, 7, and 21 postpartum; and a higher oxidative burst fluorescence intensity at d 14 prepartum and d 7, 14, and 21 postpartum compared with multiparous cows. This suggests that neutrophil function of primiparous cows was less sensitive to the changes occurring during the transition period than that of multiparous cows. In conclusion, offering concentrates during the 4-wk period prepartum had no effect on postpartum DMI, milk yield, body tissue mobilization, EB, measures of neutrophil or lymphocyte function, health, or corpus luteum activity.     

Effect of corn silage harvest maturity and concentrate type on milk fatty acid composition of dairy cows

The variation in maturity at harvest during grain filling has a major effect on the carbohydrate composition (starch:NDF ratio) and fatty acid (FA) content of corn silages, and can alter the FA composition of milk fat in dairy cows. This study evaluated the effect of silage corn (cv. Atrium) harvested and ensiled at targeted DM contents of 300, 340, 380, and 420 g/kg of fresh weight and fed to dairy cows in combination with a highly degradable carbohydrate (HC) or low-degradable carbohydrate concentrate, on the nutrient intake, milk yield, and composition of milk and milk fat. Sixty-four multiparous Holstein-Friesian dairy cows in their first week of lactation were assigned to the 8 dietary treatments according to a randomized complete block design. The 8 dietary treatments consisted of a factorial combination of the 4 corn silages and the 2 concentrates. Corn silages were offered ad libitum as part of a basal forage mixture, whereas the concentrates were given at the rate of 8.5 kg of DM/cow per day during the 15-wk experimental period. Dry matter, crude protein, and energy intakes did not differ across the corn silages. However, the intake of starch increased, and those of NDF and C18:3n-3 decreased with increasing maturation. Milk yield and composition were not different across the corn silages. Yield (kg/d) of milk, protein, and lactose was higher for low-degradable carbohydrate compared with HC concentrate-fed groups. Increasing maturity of corn silages decreased the content of C18:3n-3 and total n-3 and increased the n-6:n-3 ratio in milk fat. Concentrate type significantly altered the composition of all trans FA, except C18:2 trans-9,12. Inclusion of the HC concentrate in the diets increased the contents of all C18:1 trans isomers, C18:2 cis-9,trans-11, and C18:2 trans-10,cis-12 conjugated linoleic acid in milk fat. Milk fat composition was strongly influenced by the stage of lactation (wk 3 to 10). The content of all even short- and medium-chain FA changed with lactation, except C8:0 and C10:0. The content of C12:0, C14:0, and C16:0 and total saturated FA increased and the content of C18:0, C18:1 cis total, and total cis monounsaturated FA decreased with lactation. Maturity of the corn silages at harvest did not affect the production performance of dairy cows, but resulted in a decreased content of C18:3n-3, total n-3, and an increased n-6:n-3 ratio in the milk fat of dairy cows.     

A meta-analysis of feed digestion in dairy cows. 1. The effects of forage and concentrate factors on total diet digestibility

A meta-analysis based on published experiments with lactating dairy cows was conducted to study the effects of dietary forage and concentrate factors on apparent total diet digestibility. A data set was collected that included a total of 497 dietary treatment means from 92 studies. The diets were based on grass silage or on legume or whole-crop cereal silages partly or completely substituted for grass silage. The silages were supplemented with concentrates given at a flat rate within a dietary comparison. For the statistical evaluation, the data were divided into 5 subsets to quantify silage (digestibility, 42 diets in 17 studies; fermentation characteristics, 108 diets in 39 studies) and concentrate (amount of supplementation, 142 diets in 59 studies; concentration of crude protein, 215 diets in 82 studies; carbohydrate composition, 66 diets in 23 studies) factors on total diet digestibility. The diet digestibility of dairy cows was determined by total fecal collection or by using acid-insoluble ash as an internal marker. Diet organic matter digestibility (OMD) at a maintenance level of feeding (OMD_m) was estimated using sheep in vivo or corresponding in vitro digestibility values for the forage and reported ingredient and chemical composition values, with tabulated digestibility coefficients for the concentrate components of the diet. A mixed model regression analysis was used to detect the responses of different dietary factors on apparent total diet digestibility. Improved silage OMD_m resulting from earlier harvest was translated into improved production-level OMD in cows (OMD_p). The effects of silage fermentation characteristics on OMD_p were quantitatively small, although sometimes significant. Concentrate supplementation improved total diet OMD_m, but this was not realized in lactating dairy cows because of linearly decreased neutral detergent fiber (NDF) digestibility as concentrate intake increased. Increasing the concentrate crude protein amount quadratically improved OMD_p in cows, with the response being mostly due to improved NDF digestibility. Replacement of starchy concentrates with fibrous by-products slightly decreased OMD_p but tended to improve NDF digestibility. The true digestibility of cell solubles (OM - NDF) estimated by the Lucas test both from all data and from the data subsets was not significantly different from 1.00, suggesting that responses in OMD_p of dairy cows are mediated through changes in the concentration and digestibility of NDF.     

Effects of grass silage and soybean meal supplementation on milk production and milk fatty acid profiles of grazing dairy cows

The effects of supplementation with grass silage and replacement of some corn in the concentrate with soybean meal (SBM) on milk production, and milk fatty acid (FA) profiles were evaluated in a replicated 4 × 4 Latin square study using 16 dairy cows grazing pasture composed of ryegrass, Kentucky bluegrass, and white clover. Each experimental period lasted for 3 wk. The 4 dietary treatments were PC, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn-based concentrate mixture (96% corn; C); PCSB, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn- and SBM-based concentrate mixture (78% corn and 18% SBM; CSB); SC, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of C concentrate; and SCSB, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of CSB concentrate. The concentrate mixtures were offered twice each day in the milking parlor and were consumed completely. Grass silage supplementation reduced dietary crude protein and concentration of total sugars, and dietary SBM inclusion increased dietary crude protein concentration and decreased dietary starch concentration. Milk yield and energy-corrected milk were increased by SBM supplementation of cows with access to grass silage. Milk protein concentration was lower in cows offered grass silage, regardless of whether SBM was fed. Dietary SBM inclusion tended to increase milk fat concentration. Plasma urea N was reduced by silage feeding and increased by SBM supplementation. Supplementation with grass silage overnight could represent a useful strategy for periods of lower pasture availability. Dietary inclusion of SBM in solely grazing cows had no effects on milk production and composition, exacerbated the inefficient capture of dietary N, and increased diet cost. Grass silage supplementation affected milk FA profiles, increasing both the FA derived from de novo synthesis and those derived from rumen microbial biomass, and decreasing the sum of C18 FA (mostly derived from diet or from mobilization of adipose tissue reserves). Milk fat concentrations of conjugated linoleic acid cis-9, trans-11, vaccenic acid (18:1 trans-11), and linolenic acid (18:3n-3) were unaffected by grass silage supplementation, suggesting that partial replacement of pasture by unwilted grass silage does not compromise the dietary quality of milk fat for humans.