Cows Fed Corn Silage Research Articles

Different forage sources for F1 Holstein × Gir dairy cows

We evaluated the effect of four different forage sources on the performance of crossbred dairy cows under tropical conditions. The experiment was carried out on the Experimental Farm of the Agricultural Research Company of Minas Gerais, in Felixlândia-MG, Brazil. Twelve crossbred F1 Holstein×Gir cows were allocated to a triplicated 4×4 Latin square, balanced for residual effect, with each diet assigned to one group of three cows each period. The experiment had four treatments and five experimental periods of 21days, with 14days for adaptation and 7days for data collection. The treatments included sorghum silage, corn silage, fresh sugarcane and sugarcane silage treated with 1% calcium oxide. Three markers LIPE®, titanium dioxide and iADF were used to estimate the individual intake and the apparent digestibility of the feed for the cows in each group. The data were subjected to analysis of variance and compared by a Tukey's test at 5% probability using the PROC GLM of SAS, version 8.0 for Windows software. The dry matter intake (DMI) and organic matter intake (OMI) were highest (P<0.05) for cows consuming corn silage (P<0.05) than for cows consuming sorghum silage, fresh sugarcane and sugarcane silage. The DMI for fresh sugarcane was lower than for corn silage and sorghum silage (P<0.05). DMI was least when cows were fed sugarcane silage (P<0.05). The dry matter digestibility (DMd) and organic matter digestibility (OMd) of corn silage, sorghum silage and fresh sugarcane were similar (P>0.05) but all were higher than for the sugarcane silage-based diet (P<0.05). Milk yield by cows fed corn silage and sorghum silage was similar (P>0.05) but both were higher than for cows fed sugarcane silage and fresh sugarcane. Non-esterified fatty acids in the plasma were the greatest (P<0.05) for cows fed sugarcane silage. Nitrogen balance was the greatest for cows fed corn and sorghum silage, followed by fresh sugarcane and then sugarcane silage (P<0.05). The sugarcane silage-based diet resulted in low intake, low digestibility, low efficiency of nitrogen utilization, and high mobilization of body reserves by F1 Holstein×Gir cows, but supported a milk production similar to cows fed fresh sugarcane. Corn silage and sorghum silage resulted in satisfactory cow performance and nitrogen utilization, even when the forage:concentrate ratio was high.

Maximizing profit on New England organic dairy farms: An economic comparison of 4 total mixed rations for organic Holsteins and Jerseys

The objective of these experiments was to compare 4 total mixed rations fed to USDA-certified organic dairy cows in New England. Forty-eight Jersey cows from the University of New Hampshire (UNH) and 64 Holstein cows from the University of Maine (UMaine) were assigned to a 2 × 2 factorial arrangement of treatments testing the main effects of corn silage versus grass silage as the forage base and commodity concentrates versus a complete pelleted concentrate mixture. Treatment diets were fed as a total mixed ration for 8 wk during the winter and spring months of 2007, 2008, and 2009. Milk yield, component, and quality data were recorded and used to calculate the value of the milk produced for each cow. The dry matter intake (DMI) was recorded and used to calculate the average cost per cow per day of each diet. Income over feed costs were calculated for each diet using milk value and feed cost data. Feed cost and income over feed cost data were resampled using bootstrap methodology to examine potential patterns. Milk yield, milk fat and true protein concentrations, and SCC were similar among treatments. Cows at UNH fed corn silage tended to have higher DMI and lower milk urea nitrogen than did cows fed grass silage, whereas cows fed pellets had higher DMI than cows fed commodities. Cows at UNH fed commodities tended to have higher body condition scores than those fed pellets. Cows at UMaine fed commodities tended to have higher DMI than did cows fed pellets, and cows fed corn silage had lower milk urea nitrogen than did cows fed grass silage. Body weights and body condition scores were not different for cows at UMaine. Feed costs were significantly higher for corn silage diets and diets at UNH containing pellets, but not at UMaine. The calculated value of the milk and income over feed costs did not differ among treatments at either university. Bootstrap replications indicated that the corn silage with commodities diet generally had the highest feed cost at both UNH and UMaine, whereas grass silage diets containing commodities generally had the lowest cost. In contrast, the grass silage with commodities diets had the highest income over feed cost in the majority of the replications at both UNH and UMaine replications, whereas the corn silage with commodities diets had the lowest rank. Similar results were observed when forage prices were increased or decreased by 5, 10, and 25% above or below the actual feed price. Feeding a grass silage-based diet supplemented with commodity concentrates may have an economic advantage for dairy producers in New England operating under an organic system of production.

The effects of forage proportion and rapidly degradable dry matter from concentrate on ruminal digestion in dairy cows fed corn silage–based diets with fixed neutral detergent fiber and starch contents

This study investigated the effects of the forage-to-concentrate (F:C) ratio and the rate of ruminal degradation of carbohydrates from the concentrate on digestion in dairy cows fed corn silage–based diets. Six cows with ruminal cannulas were assigned to 6 treatments in a 6×6 Latin square. Treatments were arranged in a 3×2 factorial design. Three proportions of neutral detergent fiber from forage [FNDF; 7.6, 13.2, and 18.9% of dry matter (DM)] were obtained by modifying F:C (20:80, 35:65, and 50:50). These F:C were combined with concentrates with either high or low content of rapidly degradable carbohydrates. The dietary content of rapidly degradable carbohydrates from the concentrate was estimated from the DM disappearance of concentrate after 4h of in sacco incubation (CRDM). Thus, 2 proportions of CRDM were tested (20 and 30% of DM). Wheat and corn grain were used as rapidly and slowly degradable starch sources, respectively. Soybean hulls and citrus pulp were used as slowly and rapidly degradable fiber sources, respectively. Concentrate composition was adjusted to maintain dietary starch and neutral detergent fiber contents at 35.9 and 28.9% of DM, respectively. There was no effect of the interaction between F:C and CRDM on DM intake (DMI), ruminal fermentation, chewing activity, and fibrolytic activity. When F:C decreased, DMI increased, the mean ruminal pH linearly decreased, and the pH range linearly increased from 0.95 to 1.27 pH unit. At the same time, the acetate-to-propionate ratio decreased linearly. Decreasing F:C linearly decreased the average time spent chewing per kilogram of DMI from 35.2 to 19.5min/kg of DMI and decreased ruminal liquid outflow from 11.6 to 9.2L/kg of DMI, suggesting a decrease in the salivary flow. Increasing CRDM decreased DMI and increased the time during which pH was below 6.0 (3.1 vs. 4.8h), the pH range (0.90 vs. 1.33), and the initial rate of pH drop. It also increased the volatile fatty acid range (35 vs. 59mM), thus suggesting an increased rate of fermentation. It also decreased the acetate-to-propionate ratio (2.9 vs. 1.8). Increasing CRDM barely affected the average time spent chewing per kilogram of DMI and the ruminal liquid outflow. These results suggest that rumen pH is controlled by different mechanisms when F:C is decreased or when CRDM is increased. Consequently, FNDF is a good predictor of the chewing time, whereas CRDM is a good predictor of the pH range and volatile fatty acid profiles. Finally, considering both FNDF and CRDM improves the prediction of mean pH.

Avaliação de indicadores em estudos com ruminantes: digestibilidade

Foram conduzidos dois experimentos com o objetivo de avaliar os indicadores internos fibra em detergente neutro indigestível (FDNi) e fibra em detergente ácido (FDAi), obtidos por incubação in situ durante seis dias, e os indicadores externos óxido crômico (Cr2O3), dióxido de titânio (TiO2) e lignina isolada, purificada e enriquecida (LIPE®) em dois esquemas de coleta total de fezes (3 ou 5 dias) para estimativa da digestibilidade em bovinos. O delineamento experimental foi o de blocos ao acaso com parcelas subdivididas. No primeiro experimento, foram utilizadas cinco novilhas mestiças alimentadas com cana-de-açúcar com 1% de ureia/sulfato de amônio e concentrado (1% do peso vivo). Não houve diferenças entre as metodologias de coleta para a digestibilidade da matéria seca. Quando estimada utilizando-se FDAi, a digestibilidade dos nutrientes foi subestimada, mas, quando estimada utilizando-se FDNi e os indicadores externos (óxido crômico, dióxido de titânio e LIPE®), não diferiu significativamente daquela determinada por coleta total de fezes. No segundo experimento, foram utilizadas oito vacas em lactação alimentadas com silagem de milho e 4 kg de concentrado. Não houve diferença na digestibilidade da matéria seca entre os períodos de coleta. A digestibilidade dos nutrientes, quando estimada utilizando-se FDNi, foi superestimada, mas, quando estimada utilizando-se FDAi e os indicadores externos (óxido crômico, dióxido de titânio e LIPE®), não diferiu significativamente daquela determinada por coleta total de fezes. Três dias de coleta são suficientes para estimativa da digestibilidade e os indicadores testados são eficientes na determinação da digestibilidade.

Impact of NDF content and digestibility of diets based on corn silage and alfalfa on intake and milk yield of dairy cows

A meta analysis (22 studies, 83 dietary treatments) evaluated the impact of neutral detergent fiber (NDF) content and whole tract NDF digestibility (NDFD) on dry matter intake (DMI) and milk yield (MY) in high producing dairy cows fed corn silage and alfalfa based diets. Experimental diets were ingested at high levels to support high MY (24.1 and 37.3 kg/d, respectively of DM and MY). The average NDFD was of 42.9% (range: 20.0-68.0 %; within study standard error: ±4.0 %). DMI was negatively related with the dietary NDF (e.g. ± % of NDF caused ±160 g/d of DMI; r 1.0 2=0.51;P<0.01), while NDFD and NDF were positively related (r2=0.74; P<0.01; ±1.0 % of NDF caused approximately ±1.0 % of NDFD). MY was not influenced by dietary NDF. Considering a subset of 5 studies, the regression between NDFD and corn silage:alfalfa ratio in the diet (r2=0.84; P<0.01) allowed to estimate the NDFD of diets containing only alfalfa hay (55%) or corn silage (44%). In conclusion, the dietary NDF concentration influences the NDFD and this has implications both for DMI and MY of cows. Diets based on alfalfa hay have higher NDFD than those based on corn silage.

Impact of NDF degradability of corn silage on the milk yield potential of dairy cows

The neutral detergent fibre (NDF) degradability of corn silage samples, measured in vitro (ivNDFd) by a filter bag system, was used to examine (i) the relationship between the ivNDFd and that calculated from acid detergent lignin (L) content (NDFd) and (ii) the impact of ivNDFd variations on the predicted milk yield (MY) of dairy cows fed corn silage based diets. A total of 173 samples of corn silage were collected during a period of three years (2001-03) in different dairy farms of the Po Valley (Northern Italy). Each sample was analysed for chemical composition and was also tested in triplicate for the ivNDFd using the DaisyII incubator (Ankom, Tech. Co., Fairport, NY, USA) with incubation time of 48hs. Moreover, the NDFd of samples was calculated from the L contents, while the measured ivNDFd values were used to estimate the NEl, the potential dry matter intakes (DMI) and to predict the MY of cows.Corn silage samples of the three years were similar for NDF and starch contents (44.2 and 30.7% DM, on average, respectively) while samples from 2003, in comparison with 2001 and 2002, had lower crude protein (6.9 vs 8.3-8.4% DM, P<0.01) and L contents (3.3 vs 3.6-3.9% DM, P<0.01) and higher ivNDFd values (53.3 vs 45.6-47.8%, P<0.01). The relationship between ivNDFd and NDFd was weak (R2=0.09, not significant). The MY predicted from the NEl content and DMI of corn silage (5.5 MJ/kg DM and 8.9 kg/d) minus the maintenance energy costs, was 11.5 kg/d on average (coefficient of variation 20%). Our simulations indicate that a variation of ivNDFd by +1.0% changes the NEl of corn silage to have an expected variation in milk yield of +0.15 kg/d. If the ivNDFd is also used to predict the corn silage DMI then a +1.0% variation in ivNDFd of corn silage produces an overall +0.23 kg/d MY variation.The present results indicate that ivNDFd is highly variable in corn silage populations and differences in this nutritional parameter have an appreciable impact on the predicted milk yield from dairy cows.

Valor alimentício das silagens de milho e de sorgo e sua influência no desempenho de vacas leiteiras

Objetivou-se avaliar os efeitos das silagens de sorgo granífero, sorgo sacarino e milho sobre a ingestão, produção e composição química do leite e a digestibilidade dos nutrientes em vacas em lactação. Foram utilizadas 24 vacas da raça Prim'Holstein (PO), divididas em três lotes de oito vacas para avaliação das seguintes silagens: silagem de milho (SM); silagem de sorgo granífero (SG); e silagem de sorgo sacarino (SS). As silagens foram fornecidas à vontade com dois concentrados comerciais, distribuídos de acordo com o nível de produção leiteira. A silagem de sorgo granífero promoveu maior ingestão de MS (22,98 kg/dia) em comparação às silagens de milho (21,95 kg/dia) e de sorgo sacarino (19,43 kg/dia). A ingestão de água (litros/vaca/dia) foi semelhante entre os animais alimentados com silagem de milho (71,91) e de sorgo granífero (76,30) e menor nos animais alimentados com silagem de sorgo sacarino (56,95). A produção de leite total (28,81; 24,69 e 24,14 kg/dia) corrigida a 4% de gordura (30,65; 25,63 e 26,10 kg/dia) foi maior entre as vacas alimentadas com silagem de milho, no entanto, a porcentagem de gordura do leite das vacas alimentadas com silagem de sorgo sacarino foi maior (4,56%) em comparação àquelas alimentadas com silagem de milho (4,39%) e silagem de sorgo granífero (4,31%). A porcentagem de proteína foi maior (3,25%) no leite das vacas alimentadas com silagem de milho, intermediária no leite das vacas alimentadas com silagem de sorgo sacarino (3,05%) e menor no leite das vacas alimentadas com silagem de sorgo granífero (2,97%). Os coeficientes de digestibilidade dos nutrientes foram maiores nas vacas alimentadas com a ração à base de silagem de sorgo sacarino em comparação às rações à base de silagem de sorgo granífero e de milho.

Effects of Alfalfa Particle Size and Specific Gravity on Chewing Activity, Digestibility, and Performance of Holstein Dairy Cows

Two experiments were carried out to test the effects of alfalfa particle size and functional specific gravity (FSG) on chewing activity, digestibility, rumen kinetics, and production of lactating dairy cows fed corn silage based rations. In experiment 1, water-holding capacity (WHC), insoluble dry matter, hydration rate, and FSG changes were determined in alfalfa hay (varying in particle size) and corn silage. Reduction of particle size increased bulk density, FSG, and the rate of hydration, and decreased WHC of alfalfa. In experiment 2, 9 midlactation Holstein dairy cows fed total mixed rations containing 3 sizes of alfalfa hay (with geometric mean 7.83, 4.04, and 1.14mm) were used in a replicated 3×3 Latin square design. The diets contained 20, 20, 35, 7, 7.5, 10, 0.3, 0.1, and 0.1% of DM alfalfa, corn silage, barley, soybean meal, beet pulp, wheat bran, dicalcium phosphate, vitamin premix, and salt, respectively. The geometric means (GM) of rations were 3.34, 2.47, and 1.66mm in long, medium, and fine alfalfa treatments, respectively. Reduction of particle size increased daily NDF intake (kg), but decreased the proportion of physically effective factor (pef) and physically effective NDF (peNDF) in the ingested rations. Reduction of particle size increased the FSG of rations and intake of DM but reduced digestibility of NDF and ash. Reduction of particle size decreased ruminal mean retention time (RMRT), but increased the ruminal particulate passage rate. Milk and FCM yield were not affected by treatments. The rumen pH, total chewing activity, rumination, eating time, and milk fat were reduced as particle size decreased, but milk protein increased. This study showed that reduction of forage particle size increased bulk density, FSG, and hydration rate of alfalfa and was the most influential factor affecting DMI, milk composition, and chewing behavior. Reduction of forage particle size had minimal impact on digestibility and milk production.

Protein Level for Alfalfa and Corn Silage-Based Diets: I. Lactational Response and Milk Urea Nitrogen

This study was designed to evaluate lactational responses of cows fed corn silage (CS) or alfalfa silage (AS) as primary forage source when the diet was balanced for recommended (RP) or excessive (HP) amounts of rumen degradable protein (RDP) and undegradable protein (RUP) according to the recommendations of the National Research Council (NRC). A second objective was to evaluate different sources of variations in milk urea N (MUN). The total mixed rations included 55% forage on a dry matter (DM) basis as either 14% CS and 41% AS or 14% AS and 41% CS. Diets were offered to 48 multiparous Holstein cows (body weight = 652kg) that were assigned randomly to treatments arranged as a 2×2 factorial in 12 complete blocks based on calving date. Data collected during wk 4 to 12 of lactation were adjusted to those obtained from a pretreatment diet fed during wk 1 to 3. Crude protein (CP) averaged 16.5, 18.0, 16.2, and 17.1% of DM in the AS-RP; AS-HP; CS-RP; and CS-HP diets, respectively. Overall DM intake (DMI) was 1.5kg/d lower than predicted by NRC (24.6 vs. 26.1kg/d), but 3.5% fat-corrected milk (FCM) was higher than expected (46.1 vs. 45.0kg/d). The responses to a reduction in dietary protein were independent of primary forage source, except for milk true protein (TP) percentage. Primary forage source did not influence DMI, 3.5% FCM, TP yield, or MUN. However, compared with the AS-based diets, cows fed CS-based diets produced more milk (49.0 vs. 46.4kg/d), less fat (3.07% vs. 3.54% and 1500 vs. 1651g/d), and tended to gain more body weight. There were no benefits to feeding diets above NRC protein recommendations, regardless of forage source. Reducing CP from 17.5 to 16.4% of diet DM did not alter milk yield (47.7kg/d) or milk TP yield (1293g/d), but lowered N intake by 65g/d (700 vs. 635g/d) and lowered MUN by 1unit (12.7 vs. 11.7mg/dL). A positive correlation between MUN and production efficiency (3.5% FCM/DMI) on wk 3 of lactation suggested that body protein mobilization might impact MUN in early lactation. The correlation between MUN and DMI tended to be negative in wk 3, but was positive in wk 6 to 12 of lactation. The same was true for the correlation between MUN and somatic cell score. Regression analysis of the postpeak lactation data of this study indicated that the expected MUN was essentially 12mg/dL when NRC-predicted RDP and RUP balances were 0g/d, with a linear deviation of 0.1 and 0.03mg/dL per 10g of change in RDP and RUP balance, respectively.

Influence of feeding different types of roughage on the oxidative stability of milk

The variation in susceptibility to light-induced lipid and protein oxidation was studied in relation to the concentration of riboflavin, fatty acid composition, α-, γ-, and δ-tocopherol and β-carotene, lutein and zeaxanthine in milk from cows fed diets with roughage containing either grass silage or corn silage mixed with concentrates. The results show that milk from cows fed grass silage had a higher concentration of the antioxidants measured. The contents of unsaturated C18 fatty acids were significantly different in the two types of milk, showing that the compositions of antioxidants and fatty acids were influenced by the feeding. Despite a higher antioxidative capacity in the milk from cows fed grass silage, lipid oxidation was higher in this milk compared to milk from cows fed corn silage. The results indicate that quenching of singlet oxygen by the antioxidants did not prevent lipid oxidation. The degree of unsaturation in linolenic acid, C18:3, is proposed to be important for the higher accumulation of lipid hydroperoxides in milk from cows fed grass silage. In contrast to milk from cows fed grass silage being more vulnerable to lipid oxidation, milk from cows fed corn silage is more vulnerable to protein oxidation. The results indicate that protein oxidation occurs independently of lipid oxidation. It is concluded that the higher concentration of antioxidants in milk from cows fed grass silage is able to extend the lag phase of protein oxidation and delay the formation of dityrosine.

Southeastern Pasture-Based Dairy Systems: Housing, Posilac, and Supplemental Silage Effects on Cow Performance

This experiment tested performance and physiological responses to evaporative cooling, bovine somatotropin (bST), and supplemental silage of lactating cows grazing bermudagrass (Tifton 85; Cynodon dactylon ×C. nlemfuensis cv.) pastures. Multiparous (n = 32) cows (196 d in milk) were assigned one of five treatments arranged in two replicates. Treatments were 1) cows maintained continuously on pasture with access to shade, 2) treatment 1 + bST, 3) night housing on pasture, then free-stall housing with fans and misters from 0730 to 1630h, 4) treatment 3 + bST, and 5) treatment 4 + corn silage fed at 0.5% of body weight (dry matter basis) in the barn. A grain supplement was fed at a rate of 0.5 kg/kg of milk produced. Time spent grazing ranged from 4 to 7.2 h/d, with cows fed corn silage spending the least amount of time. Cows given bST grazed 45 min/d longer than controls, but intake of bermudagrass was unchanged. Intake of bermudagrass ranged from 7.4 to 9.5 kg/d of organic matter, with the lowest intake by cows fed corn silage. With the exception of cows fed corn silage, cows kept in a cooling barn during the day ate equivalent amounts of pasture as those given unlimited access to pasture. Production of 4% fat-corrected milk was greater by cows injected with bST (17.7 vs. 15.8 kg/d) compared with controls and tended to be greater for cows given daytime cooling compared with cows on pasture continuously (17.2 vs. 16.3 kg/d). Cows provided evaporative cooling did not lose weight compared with continually pastured cows (6.3 vs. –10.9 kg/24 d). Cows injected with bST compared with controls maintained their body weight better (2.5 vs. –7.1 kg/24 d). Cows given bST had increased concentration of plasma insulin-like growth factor-I (142 vs. 89ng/ml), insulin (0.60 vs. 0.56ng/ml), and nonesterified fatty acids (318 vs. 239 mEq/L). Cows given bST and those continually on pasture had greater diurnal body temperatures. Use of barn cooling systems and bST treatments as management tools provided limited improvement in performance of midlactation cows managed in pasture-based systems.

Brown midrib sorghum in diets for lactating dairy cows.

In Experiment 1, 16 Holstein cows were assigned to one of four diets in replicated 4 x 4 Latin squares with 4-wk periods to measure dietary effect on short-term lactational performance. Additionally, 3 fistulated cows were assigned to the same diets in a 3 x 4 Youden square design with 4-wk periods to measure ruminal rate and extent of fiber digestion, fractional passage rate of fiber, ruminal pH, and concentration of volatile fatty acids. Diets comprised 65% of brown midrib (BMR) forage sorghum, standard forage sorghum, alfalfa or corn silages and 35% concentrate. Experiment 2 was conducted with 30 Holstein cows in early lactation to evaluate the same BMR sorghum hybrid in a 10-wk study with 35.3% standard sorghum, BMR sorghum, or corn silages as dietary treatments. Milk production was significantly higher for brown midrib than for standard sorghum in Experiment 1. Ruminal pH and acetate to propionate ratio did not differ among diets. The fractional passage rate of silage was not significantly different among the forages. In situ extent of ruminal fiber digestion was significantly higher for BMR than for standard sorghum, but rate of fiber digestion was not different. Similarly, in Experiment 2, in vitro extent of fiber digestion was significantly higher for BMR sorghum than for standard sorghum. Dry matter intake and body condition score were not significantly different between cows fed BMR and standard sorghum, but cows fed BMR sorghum resulted in long-term milk production greater than cows fed standard sorghum and similar to cows fed corn silage.

Effect of Corn Silage Supplementation on Intake and Milk Production in Cows Grazing Grass Pasture

The objective was to determine the effects on milk production and DMI of 2.3 kg/d of corn silage DM fed to lactating cows grazing grass pasture and fed supplemental grain. Thirty Holstein cows, averaging 32kg of milk at the start of the trial, intensively grazed grass pasture for 8 wk. One-half of the cows received 2.3 kg/d of corn silage DM in two equal feedings, and one-half of the cows were used as controls (no corn silage). All cows were fed grain at 1kg of grain DM/4kg of milk. Corn silage had no effect on milk production or milk composition. Cows fed corn silage did not have improved BW gain or body condition score. Each unit of corn silage consumed replaced 1.2 units of pasture, but total DMI was not different because of supplementation with corn silage. Blood urea N concentrations were lower for cows fed corn silage. Supplementation of high producing Holsteins grazing grass pastures with 2.3 kg/d of corn silage DM had no effect on milk production, milk composition, or total DMI.

Nutritional evaluation of ensilage made from intercropped corn and sunflowers

The feeding value of sunflower–corn silage relative to that of corn silage as the only forage fed lactating cows was established using 12 lactating Holstein cows in an experiment with a 2 × 2 Latin square design. Treatment periods were 5 wk and there was no changeover period between treatments. A constant grain intake to milk yield ratio of 1:4 was maintained. The comparison was based on dry matter (DM) intake, milk yield and composition, body-weight change, rumen pH and molar proportions of volatile fatty acids and plasma metabolites. The sunflower–corn silage was lower in DM content (25.4 vs. 29.2%), but higher in protein (11.5 vs. 8.0%), acid detergent fiber (33.2 vs. 29.2%), fat (8.1 vs. 2.1%) and total ash (10.6 vs. 4.9%). Silage DM intake was the same for both silages, but milk yield was significantly greater (P &lt; 0.05) (32.7 vs. 31.2 kg d−1) for cows fed sunflower–corn silage. However, both milk fat (3.19 vs. 3.87%) and milk protein (3.04 vs. 3.26%) were lower (P &lt; 0.05) for cows fed sunflower–corn silage, resulting in a higher (P &lt; 0.05) fat-corrected milk yield (30.5 vs. 28.4 kg d−1) for the cows fed corn silage. Type of silage fed did not alter rumen pH, but the molar percentage of acetic acid was higher (P &lt; 0.05) and the molar percentages of isovaleric and valeric acids were lower when sunflower–corn silage was fed. The feeding of sunflower–corn silage resulted in a significant increase (P &lt; 0.05) in plasma urea nitrogen (10.60 vs. 7.53 mg 100−1), cholesterol (7.36 vs. 5.63 mmol L−1) and triglyceride (0.20 vs. 0.18 mmol L−1). Plasma levels of methionine (29.9 vs. 18.5 mmol mL−1) and valine (208.0 vs. 191.0 N mol mL−1) were greater for cows fed the sunflower–corn silage. It was concluded from this study that intercropped sunflower–corn harvested and preserved as silage is an acceptable source of forage for lactating cows, but when fed as the only source of forage it may have a negative impact on milk composition. Key words: lactating cows, sunflower–corn silage, milk yield, milk composition

Effect of Protein Source and Energy on Milk Composition in Midlactation Dairy Cows

Thirty multiparous Holsteins and 12 multiparous Jerseys (90±15 d in lactation) were assigned in a 3×2 factorial design. Diets containing 0, 1, or 2kg fish meal at 70 or 75% TDN were fed for 8 wk. Dry matter intake was greater on the high TDN diet. Milk and FCM yields were not different. Percentage of milk fat, percentage of protein, and protein yield decreased with inclusion of fish meal in the diet.In Experiment 2, 30 primiparous Holsteins (106±24 d in lactation) were assigned one of two diets in an incomplete block design for two consecutive 32-d periods. Corn silage-based diets varied in CP and source as follows: 12% CP, soybean meal; 20% CP, soybean meal; 20% CP, fish meal; 20% CP, corn gluten meal; 20% CP, gluten:soybean; and 20% CP, fish meal:soybean. Milk fat and milk lactose percentages and FCM yield (kg) were higher on corn gluten meal (3.13, 5.30, 23.0) than on fish meal (2.11, 5.00, 20.5). Milk protein yield was affected by amount and source of protein. Rumen ammonia and plasma urea were greater on high (13.5, 16.2mg/dl) than on low soybean meal (7.3, 6.4mg/dl). Results indicate protein source may affect milk composition in cows fed corn silage diets.

Effect of Feeding Corn-Sunflower Silage on Milk Production, Milk Composition, and Rumen Fermentation of Lactating Dairy Cows

Corn, corn-sunflower intercropped, and sunflower silages were evaluated as roughage sources for high producing dairy cows. Thirty multiparous Holstein cows were started in a 3×3 Latin square design with 3-wk periods. Treatments were: 1) corn, 2) sunflower, and 3) corn-sunflower intercropping. Cows were fed once a day a total mixed ration consisting of a 50:50 concentrate:roughage (dry basis) with silage included as 60% of the forage. Cows fed corn silage had the lowest milk production compared with those fed corn-sunflower and sunflower (29.3, 30.1, and 30.0kg/d). Four percent FCM was not different for corn and corn-sunflower; sunflower was lower than both. Corn did not differ in total fat production or fat test from corn-sunflower; sunflower was the lowest of the three. No differences were observed for total protein production, protein test, or total or individual rumen VFA concentration. Dry matter intake for corn-sunflower was 4.5% lower than for corn and 11.3% lower than for sunflower. Daily intake of NE was similar for corn and corn-sunflower treatments and greatest for the sunflower treatment. No significant differences were observed for blood serum FFA, cholesterol, or triglycerides. Oleic and linoleic percent in milk were greater for sunflower, intermediate for corn-sunflower, and the lowest for corn.

Effects of Adding Beta-Carotene to Rations of Lactating Cows Consuming Different Forages1,2

Thirty-six Holstein cows fed a corn silage-based ration and 34 fed an alfalfagrass silage-based ration were assigned according to calving date to receive either 300 mg/head per day of synthetic betacarotene in a gelatin capsule or an empty gelatin capsule daily for the first 100 days postpartum. Supplemental vitamin A was provided at 3919 IU/kg of ration dry matter. Cervix diameters for cows supplemented with betacarotene were smaller at 21 days and 28 days postpartum. Days from parturition to first observed estrus were less when betacarotene was added and less when corn silage was fed. Means of other reproductive traits were more favorable for cows treated with beta-carotene (fewer services per conception and shorter intervals between parturition and conception). Milk progesterone at 21 and 28 days postpartum was not affected by either roughage or beta-carotene treatment. Milk from cows receiving alfalfa-grass silage contained lower somatic cell concentrations than that produced by cows fed corn silage. Milk somatic cell concentrations were lower in both roughage treatment groups for cows supplemented with beta-carotene. No effects of roughage or beta-carotene on milk production or milk fat percentages were significant.

Comparison of Soybean-Grain Sorghum Silage with Corn Silage for Lactating Cows

Data were collected in a 3-yr experiment to compare the intake, milk production, and return above feed cost of cows fed soybean-grain sorghum silage with those of cows fed corn silage. In the last yr, soybean-grain sorghum was harvested at the flower stage of the soybean plants. In the 2nd and 3rd yr, soybean-grain sorghum was harvested at both the flower and early bean stages. In all 3 yr corn silage was harvested in the dent stage of maturity. Ten cows in early lactation were on each treatment in each of the 3 yr (80 cows) to evaluate the silages. Cows fed corn silage consumed 10, 12, and 20% more dry matter and produced 1.8, 1.9, and .8kg more fat-corrected milk daily than those fed flower stage soybean-grain sorghum for yr 1 to 3. Cows fed corn silage consumed 3 and 14% more dry matter and produced 1.8 and 2.0kg more fat-corrected milk than cows fed the early stage bean. Corn cost more per hectare than soybean-grain sorghum to grow each year, but the cost per unit silage produced was less. Higher daily milk production coupled with lower silage cost resulted in consistently greater return above feed cost for corn silage.

Changes of Tocopherols in Blood Serum of Cows Fed Hay or Silage

The purpose was to determine if cows fed corn silage during gestation have calves with low serum tocopherol and high erythrocyte hemolytic rates. Ten cows were fed hay, six fed corn silage with one vitamin E injection, and six fed corn silage with no injection beginning with the 6th mo of gestation. Hay intakes were adjusted to equalize intakes of dry matter. Analysis of tocopherol isomers was by reverse phase, high performance liquid chromatography. Alpha-tocopherol and potassium were lower for hay-fed cows than for cows fed predominantly corn silage, but creatinine phosphokinase, glutamic-oxaloacetic transaminase, and glucose were higher. Calves from hay-fed cows had lower α-tocopherol and higher glutamic-oxaloacetic transaminase. No consistent histopathological changes of muscle tissue were seen. Erythrocyte hemolytic rates were low. Serum vitamin E of cows may change during gestation because of type of forage fed. Specific enzyme changes may give an early indication of a change of tocopherol status of cattle.

Feeding Value of a High Oil Variety of Sunflowers as Silage to Lactating Dairy Cows

Whole-plant sunflowers (oilseed) were chopped and stored as silage and compared to corn silage as the sole forage to 20 lactating Holsteins in a switch-back design of three 5-wk periods. Cows fed sunflower silage produced less milk (22.4 vs. 20.5 kg/day) but similar amounts of 4% fat-corrected milk. Cows fed sunflower silage had greater fat, less protein, and less total solids in milk. Cows consumed 4.0 kg/day less dry matter from sunflower silage than from corn silage. Oleic and linolenic increased, and myristic and palmitic fatty acids decreased in milk fat from cows fed sunflower silage. Cholesterol in serum (mg/dl) was 321 and 160 for cows fed sunflower silage and corn silage. Cows fed sunflower silage had higher molar percentage of acetate, isobutyrate, isovalerate, and a wider acetate propionate ratio with concomitant lower molar percentage of propionate, butyrate, valerate, and less total acids in rumen fluid than cows fed corn silage. Rumen fluid pH was 6.98 and 6.83 for cows fed sunflower silage and corn silage. Acceptable quality silage can be made from whole oilseed sunflowers. For maximum milk production, sunflower silage should not be fed as the only forage to dairy cows.