Forage Dry Matter Intake Research Articles

Dry Matter Intake and Apparent Digestibility of Nutrients in the Ration of Mangalarga Marchador Weanling Horses Fed Sorghum Silage Versus Grass Hay

In central Brazil, there are two well-defined climatic periods, the rain and the dry season, the latter being marked by massive forage shortages in pastures. In this context, forage conservation such as making hay and silage for herbivores is imperative during the dry season. Grass hay is most commonly used for horses, but sorghum silage is often used for ruminants. The objective was to compare the nutrient digestibility, fecal production, and dry matter intake (DMI) of sorghum silage (Sorghum bicolor l. Moench CV. BRS 655) to that of vaquero hay (Cynodon CV. 90160 CD × CV. Mirage). Twelve Mangalarga Marchador fillies (8 months of age) were divided into two groups: S (sorghum silage, n = 6) and F (vaquero hay, n = 6). The ration was formulated to supply 3.0% body weight in dry matter (DM) per day, with a forage:concentrate ratio of 50:50 on a DM basis. The concentrate used was a corn-based ration formulated to meet or exceed requirements for growth when fed at 1.5% body weight DM to young horses. The animals were housed in individual stalls (3 × 3m) for a period of 25 days, with 21 days for adaptation, followed by 4 days of total collection of feces. During the collection period, an external marker of digestibility, Purified and Enriched Lignin (LIPE), was added to the concentrate as an external marker to determine the apparent digestibility coefficients of DM, crude protein, gross energy, neutral detergent fiber, acid detergent fiber, hemicelluloses, and cellulose. The forage DMI was calculated by subtracting the quantity supplied at each meal minus the amount of forage that was not eaten by the next meal (orts). The measures of digestibility of the sorghum silage were not different (P > .05) from that of vaquero hay. However, DMI of the sorghum silage was lower (P < .05) than the vaquero hay and may be of concern if fed for prolonged periods of time and not supplemented with carefully balanced concentrates. Purified and Enriched Lignin can be used as a marker for evaluation of digestibility of nutrients in weanling horses.

Assessment of dietary ratios of red clover and corn silages on milk production and milk quality in dairy cows.

Twenty-four multiparous Holstein-Friesian dairy cows were used in a replicated 3×3 Latin square changeover design experiment to test the effects of changing from corn (Zea mays) silage to red clover (Trifolium pratense) silage in graded proportions on feed intakes, milk production, and whole-body N and P partitioning. Three dietary treatments with ad libitum access to 1 of 3 forage mixtures plus a standard allowance of 4kg/d dairy concentrates were offered. The 3 treatment forage mixtures were, on a dry matter (DM) basis: (1) R10: 90% corn silage and 10% red clover silage, (2) R50: 50% corn silage and 50% red clover silage, and (3) R90: 10% corn silage and 90% red clover silage. In each of 3 experimental periods, there were 21d for adaptation to diets, and 7d for measurements. Diet crude protein intakes increased, and starch intakes decreased, as the silage mixture changed from 90% corn to 90% red clover, although the highest forage DM intakes and milk yields were achieved on diet R50. Although milk fat yields were unaffected by diet, milk protein yields were highest with the R 0250 diet. Whole-body partitioning of N was measured in a subset of cows (n=9), and both the daily amount and proportion of N consumed that was excreted in feces and urine increased as the proportion of red clover silage in the diet increased. However, the apparent efficiency of utilization of feed N for milk protein production decreased from 0.33g/g for diet R10 to 0.25g/g for diet R90. The urinary excretion of purine derivatives (sum of allantoin and uric acid) tended to increase, suggesting greater flow of microbial protein from the rumen, as the proportion of red clover silage in the diet increased, and urinary creatinine excretion was affected by diet. Fecal shedding of E. coli was not affected by dietary treatment. In conclusion, even though microbial protein flow may have been greatest from the R 0450 diet, optimum feed intakes and milk yields were achieved on a diet that contained a 1:1 DM mixture of corn and red clover silages.

Evaluation of a method to predict negative feedstuff associative effects in meat goats consuming diets with different forage sources and levels of concentrate

ABSTRACTEffects of dietary concentrate level and grass hay source were determined to evaluate a method (www2.luresext.edu/goats/research/suppconc.html) of predicting negative associative effects between feedstuffs in Boer goat wethers. Forage DM intake (g/kg BW0.75) was similar (P = .157) between growing and yearling wethers (34.9 and 30.8) and ranked 0 and 15 > 30 > 45 g/kg BW0.75 of concentrate dry matter (48.5, 41.8, 25.9, and 15.2, respectively). Age and concentrate level interacted in neutral detergent fibre digestibility (57.3%, 60.6%, 61.4%, and 58.4% for growing and 56.6, 62.9, 56.8, and 30.0% for yearling wethers with 0, 15, 30, and 45 g/kg BW0.75, respectively). There was a tendency (P = .074) for an interaction in metabolizable energy (ME) intake between age and concentrate level (361, 530, 634, and 709 for growing and 363, 547, 541, and 555 kJ/kg BW0.75 for yearling wethers with 0, 15, 30, and 45 g/kg BW0.75); values predicted for treatments with concentrate were 563, 631, and 619 for growing and 575, 684, and 697 kJ/kg BW0.75 for yearling wethers with 15, 30, and 45 g/kg BW0.75, respectively. In conclusion, ME intake was accurately predicted for the low level of concentrate with both animal types and the moderate level with growing wethers.

Biological implications of longevity in dairy cows: 2. Changes in methane emissions and efficiency with age

Previous studies indicated that absolute CH4 emissions and CH4 yield might increase and that milk production efficiency might decrease with age in cattle. Both would make strategies to increase longevity in dairy cattle less attractive. These aspects were experimentally determined in Brown Swiss cattle distributed continuously across a large age range. Thirty lactating dairy cows (876–3,648 d of age) received diets consisting of hay, corn silage, and grass pellets supplemented with 0 or 5kg of concentrate per day. Twelve heifers (199–778 d of age) received hay only. Cows and heifers were members of herds subjected to the 2 different feeding regimens (with or without concentrate) for the past 10 yr. Methane emissions were measured individually for 2 d in open-circuit respiration chambers, followed by quantifying individual feed intake and milk yield over 8 d. Additional data on digestibility, rumination time, and passage time of feed of all experimental animals were available. Regression analyses were applied to evaluate effects of age and feeding regimen. Body weight, milk yield, and the hay proportion of forage dry matter intake were considered as covariates. Methane emissions per unit of intake, body weight, and milk yield were significantly related to age. Their development in the cows with age was characterized by an increase to maximum at around 2,000 d of age, followed by a decline. This response was not accompanied by corresponding age-related changes in intake, chewing activity, digesta passage time, and digestibility of organic matter, which would have explained shifts in CH4. However, fiber digestibility showed a similar change with age as methane emissions, resulting in quite stable methane emissions per unit of digestible fiber. As expected, methane emissions intensity per unit of milk produced was greater by 8% without concentrate than with concentrate, but no difference was noted in the response to age when the animals were subjected to different feeding regimens. The efficiency of milk production was only marginally influenced by age and diet, and no different response was observed for age in the 2 dietary regimens. In conclusion, life cycle analyses of milk production systems focusing on longevity should consider changing methane yields with age in addition to the variation in environmental costs for replacements of culled cows.

Short communication: Intake, milk production, and milk fatty acid profile of dairy cows fed diets combining fresh forage with a total mixed ration

To establish the effects of access time to high-quality temperate fresh forage (FF) on intake and performance of cows fed a total mixed ration (TMR), 9 Holstein cows were assigned to three 3×3 Latin squares with 20-d periods with sampling in the last 10 d. The following treatments were evaluated: 0 (T0), 4 (T4), and 8 (T8) h of daily access to FF. Forage (Lolium multiflorum) was cut daily and offered ad libitum beginning at 0800h in individual stalls, and a TMR was offered ad libitum during the period when cows had no access to FF. Fresh forage dry matter intake (DMI) increased and TMR DMI decreased with the access time to FF, whereas total DMI was 3.0kg higher for T4 than for T8; no differences were detected with T0. Compared with T0, 8h/d of access to FF decreased milk, protein, and casein yields, and tended to decrease fat and lactose yields, but treatment had no effect on milk composition or feed efficiency. The milk fatty acid profile in T8 had a higher content of rumenic, vaccenic, and linolenic acids compared with T0. We concluded that cows with 4h of access to high-quality FF had similar DMI and milk yields as cows fed only the TMR, but more than 4h of access reduced DMI and performance without changes in feed efficiency, although milk fat had enhanced levels of beneficial fatty acids.

Faecal characteristics and milk production of dairy cows in early-lactation fed diets differing in forage types in commercial herds

ABSTRACTEffects of grass–clover silage (GCS) alone or combined with whole-crop cereal silage, maize silage (MS) or ensiled pressed sugar beet pulp (EPSB) on faecal characteristics and performance of early-lactation dairy cows were studied in 26 herds. Data were analysed with herd as the experimental unit and correlation coefficients among the variables were estimated. Feeding MS combined with GCS resulted in faeces of a firmer consistency (P < .05), containing more undigested fibre compared to feeding GCS alone or with EPSB (P < .05). There was a strong positive correlation between the number of grains and starch concentration in faeces (r = 0.83, P < .001). Increasing forage dry matter (DM) intake decreased faecal DM concentration (r = −0.54, P < .01) but seems to result in cleaner cows, whereas increasing DM intake of concentrate increased faecal DM concentration (r = 0.63, P < .01) but might result in dirtier cows.

BILL E. KUNKLE INTERDISCIPLINARY BEEF SYMPOSIUM: A meta-analysis of research efforts aimed at reducing the impact of fescue toxicosis on cattle weight gain and feed intake.

The objective of this paper is to present a systematic review and meta-analysis of research efforts aimed at recovering cattle production losses attributed to toxic endophyte-infected [ (Morgan-Jones & Gams.) Glenn, Bacon, & Hanlin comb. Nov.] tall fescue [ (Schreb.) Darbysh.]. The strategies presented include those 1) applied with forage systems, 2) based on pharmacological compounds and functional foods, and 3) based on supplemental dietary nutrients. Cattle BW gain and DM intake was the dependent response evaluated. Among the forage systems reviewed, studies with nontoxic, endophyte-infected tall fescue as a total replacement forage system demonstrated the greatest improvement in per-hectare (152 ± 27.5 kg/ha) and per-animal (0.29 ± 0.03 kg/d) BW gain. Studies with interseeded legumes have exhibited a small and highly variable BW gain effect size per hectare (52 ± 24.1 kg/ha) and per animal (0.11 ± 0.03 kg/d). The legume response was seasonal, with summer exhibiting the greatest benefit. Studies with chemicals that suppress plant growth demonstrated BW gain responses (0.17 ± 0.06 kg/d) equal to or greater than the response observed with legume studies. Cattle grazing toxic tall fescue responded well to anthelmentics, antimicrobial feed additives, and steroid implants, and the use of these technologies may additively help recover production losses. As a group, functional foods have not improved BW gain ( = 0.85). Studies with cattle supplemented with highly digestible fiber supplements observed a 0.15 kg greater BW gain compared with studies using starch- and sugar-based supplements ( < 0.05). Weight gain was positively impacted by the level of supplementation (0.06 kg/DM intake as percent BW). Supplement feed conversion was estimated at 6:1 for the highly digestible fiber supplements compared with 11:1 for starch-based supplements. Tall fescue forage DM intake was predicted to maximize at a supplemental feeding rate of 0.24% BW with a breakpoint at 0.5% BW, and total maximum DM intake (forage plus supplement) occurred at 2.7% BW when supplemental feeding approached 0.9% BW. Results from this meta-analysis should be useful for 1) establishing and comparing measured responses to theoretical improvements in BW gain when additive strategies are considered, 2) research planning, and 3) producer education.

Effect of post-weaning residual feed intake classification on grazed grass intake and performance in pregnant beef heifers

Manafiazar, G., Basarab, J. A., Baron, V. S., McKeown, L., Doce, R. R., Swift, M., Undi, M., Wittenberg, K. and Ominski, K. 2015. Effect of post-weaning residual feed intake classification on grazed grass intake and performance in pregnant beef heifers. Can. J. Anim. Sci. 95: 369–381. There is limited knowledge of how cattle tested for feed efficiency under drylot conditions perform when they graze on summer pasture. Residual feed intake adjusted for end of test backfat thickness (RFIfat) was determined on 171 beef crossbred heifers under drylot conditions over 2 yr using an automated system. Upon completion of the test, the 10 lowest and 10 highest RFIfat (–0.54±0.17 vs. 0.58±0.15 kg DM d−1) heifers in 2012, and the 14 lowest and 14 highest RFIfat (−0.47±0.16 vs. 0.53±0.19 kg DM d−1) heifers in 2013 were selected and placed on meadow bromegrass pasture to investigate the effect of RFIfat ranking on their grass intake and performance on the pasture. The pasture adaptation period (8 d in 2012 and 19 d in 2013) was followed by a pasture feed intake experiment during which heifers were dosed twice daily (0815 and 1415) with 500 g of C32-labeled feed pellet for 13 d (day 0 to 12) and fecal sampled twice daily (0815 and 1415) from day 8 to 12. Forage DM intake on pasture for each heifer was determined using the double alkane (C31/C32) methodology. High and low RFIfat heifers were similar in body weight (BW), backfat and rump fat thickness, and average daily gain (ADG) during the grazing trial period, except backfat thickness at the end of test period. However, low RFIfat heifers consumed 5.3% less forage when expressed as kg DM d−1 (8.20±0.08 vs. 8.66±0.09, P&lt;0.001) and 5.1% less when expressed as a percentage of body weight (1.86±0.02 vs. 1.96±0.02% of BW, P&lt;0.001) compared with high RFIfat heifers. RFIfat measured under drylot conditions in growing heifers was positively correlated to grazed RFIfat determined in pregnant heifers (rp=0.30, P=0.04). These results suggest that beef heifers classified as low RFIfat during the post-weaning drylot period had lower dry matter intake as heifers in their first pregnancy grazing tame pasture, with no negative impact on their body weight, back-fat thickness, and ADG compared with their high RFIfat herdmates.

Apparent recovery of C18 polyunsaturated fatty acids from feed in cow milk: A meta-analysis of the importance of dietary fatty acids and feeding regimens in diets without fat supplementation

A meta-analysis was conducted using the results of 82 experiments (78 publications, 266 treatments) to investigate the importance of dietary C18 fatty acids (FA) and feeding regimen for milk C18 FA profile and apparent recovery of selected FA relative to intake of these FA or their precursors. Feeding treatments based on lipid-supplemented diets were excluded. Feeding regimens were defined as grazing [including partial and full-time grazing, at dietary concentrate proportions from 0 to 44% dry matter (DM)], forage-based indoor feeding [>65% forage of total DM intake (DMI)], and concentrate-based indoor feeding (forage DMI ≤65% of DMI). Linoleic acid (LLA), α-linolenic acid (ALA), and total C18 FA proportions in milk fat increased linearly with the respective dietary FA content in all feeding regimens tested. This effect was highest in the forage-based indoor feeding. Slopes were lowest for the grazing regimens, especially regarding ALA and the sum of all C18 FA, whereas the intercepts of the prediction equations of milk ALA and total C18 FA proportions were highest for grazing regimens. This indicates that, in grazing cows, factors other than dietary FA contents determine the C18 FA composition of the milk fat. At equal dietary LLA contents, the type of feeding regimen showed no significant effect on LLA proportion in milk fat. Milk fat proportions of rumenic acid and vaccenic acid were positively related to the sum of dietary ALA and LLA contents. Grazing regimens led to the strongest enrichment of rumenic acid and vaccenic acid in milk fat. The apparent recovery of ALA, LLA, and total C18 FA (secreted, % of intake), an estimate for transfer efficiency, decreased with increasing dietary content. This relationship followed a nonlinear decay function. When the dietary content of these FA exceeded a certain threshold (about 0.2, 0.8, and 2.8% of DM for ALA, LLA, and total C18 FA, respectively) the recovery in milk remained constant at about 5, 10, and 82% of the ingested ALA, LLA, and total C18 FA, respectively. At dietary proportions below 0.01% ALA and 1.5% total C18 FA of DM, their apparent recovery in milk fat exceeded 100%. In conclusion, a general inverse relationship between dietary C18 FA and the corresponding apparent recovery in milk fat seems to exist. Within this frame, the effect of different types of feeding regimens on the eventual milk C18 FA profile varies. Among them, grazing pasture appears to provide the most variable properties.

Use of Stochastic Simulation to Evaluate the Reduction in Methane Emissions and Improvement in Reproductive Efficiency from Routine Hormonal Interventions in Dairy Herds.

This study predicts the magnitude and between herd variation in changes of methane emissions and production efficiency associated with interventions to improve reproductive efficiency in dairy cows. Data for 10,000 herds of 200 cows were simulated. Probability of conception was predicted daily from the start of the study (parturition) for each cow up to day 300 of lactation. Four scenarios of differing first insemination management were simulated for each herd using the same theoretical cows: A baseline scenario based on breeding from observed oestrus only, synchronisation of oestrus for pre-set first insemination using 2 methods, and a regime using prostaglandin treatments followed by first insemination to observed oestrus. Cows that did not conceive to first insemination were re-inseminated following detection of oestrus. For cows that conceived, gestation length was 280 days with cessation of milking 60 days before calving. Those cows not pregnant after 300 days of lactation were culled and replaced by a heifer. Daily milk yield was calculated for 730 days from the start of the study for each cow. Change in mean reproductive and economic outputs were summarised for each herd following the 3 interventions. For each scenario, methane emissions were determined by daily forage dry matter intake, forage quality, and cow replacement risk. Linear regression was used to summarise relationships. In some circumstances improvement in reproductive efficiency using the programmes investigated was associated with reduced cost and methane emissions compared to reliance on detection of oestrus. Efficiency of oestrus detection and the time to commencement of breeding after calving influenced variability in changes in cost and methane emissions. For an average UK herd this was a saving of at least £50 per cow and a 3.6% reduction in methane emissions per L of milk when timing of first insemination was pre-set.

Effect of rumen degradable energy supplementation on forage utilization and performance of steers grazing stockpiled cool season perennial grass pastures

Añez-Osuna, F., Penner, G. B., Larson, K., Jefferson, P. G., Lardner, H. A. and McKinnon, J. J. 2015. Effect of rumen degradable energy supplementation on forage utilization and performance of steers grazing stockpiled cool season perennial grass pastures. Can. J. Anim. Sci. 95: 255–265. The objective of this study was to evaluate the effects of supplementing rumen degradable energy using blended by-product pellets that differed in starch and degradable fiber content on forage utilization and performance of steers grazing stockpiled cool-season perennial grass (CSPG) pastures. Forty-five yearling crossbred steers (334±23.5 kg) stratified by body weight (BW) were randomly assigned to one of nine pastures (five steers/pasture) of mature cool-season perennial grasses. Each pasture was randomly assigned (n=3) to one of three treatments: no supplement (CON); low-starch/high degradable-fibre (LSHF; 40.3% starch; 29.5% NDF) pellet and high-starch/low-degradable fibre (HSLF; 48.6% starch; 22.8% NDF) pellet, both fed daily at 0.6% of BW (DM basis). The grazing period lasted 70 d (from early-August to mid-October). Over the 70-d study, forage CP decreased from 9.9±0.82 to 6.9±0.59% of DM and digestible energy content decreased from 2.6±0.04 to 2.2±0.04 Mcal kg−1of DM. Treatment did not affect forage utilization (P=0.50; 73.4±3.15%) or forage DM intake (P=0.90; 9.0±1.54 kg d−1). Final BW and average daily gain (ADG) were not different (P&gt;0.05) between LSHF (435±6.4 kg and 1.4±0.10 kg d−1) and HSLF (439±10.4 kg and 1.5±0.14 kg d−1) treatments. However, supplemented steers had higher (P&lt;0.05) final BW and ADG than the control steers (402±5.6 kg and 1.0±0.09 kg d−1). These results show that unsupplemented beef steers grazing stockpiled CSPG pastures were limited in both energy and protein intake and that supplementation with by-product feed pellets formulated to supply protein and energy either as starch or degradable fibre equally improved animal performance.

Consumo y digestibilidad en novillos cebuínos en un sistema silvopastoril intensivo

La determinación del consumo voluntario de materia seca (CMS) por los animales, es indispensable para determinar su capacidad productiva y su estado nutricional. Existen muchas técnicas para la estimación del CMS, siendo una de ellas la técnica de n-alcanos la cual permite además estimar la selectividad de los forrajes consumidos. El presente trabajo tuvo como objetivo estimar el consumo voluntario y la excreción fecal de nutrientes por novillos cebuínos alimentados en un sistema silvopastoril intensivo (SSPi). El estudio se realizó en el Centro Experimental Cotové, propiedad de la Universidad Nacional de Colombia. Se evaluaron seis novillos castrados con un peso promedio de 381±12 kg y se utilizó la técnica de alcanos para determinar CMS. El CMS promedio de forraje fue de 9,54 kg dia-1, del cual, el 75,24 % correspondió a consumo de gramíneas y el 24,76 % a consumo de leguminosa. En promedio, el consumo de nutrientes (kg) fue de 1,33; 5,8; 4,02; 1,13; 0,058 y 0,021 para PC, FDN, FDA, Cenizas, Ca y P respectivamente. Estos consumos fueron adecuados para el tipo de animales del estudio aportando una dieta de buena calidad nutricional. La digestibilidad fue del 53 % para el tratamiento sin inclusión del suplemento y del 58 % para el tratamiento con suplemento, lo que junto con el CMS, permite afirmar que los animales satisficieron sus requerimientos de los principales nutrientes. Las cantidades excretadas (kg) fueron 4,15; 0,44; 2,56; 1,78; 0,8; 0,054 y 0,02 para MS, PC, FDN, FDA, Cenizas, Ca y P, respectivamente. La excreción fecal de N por animal al año se calculó en 29,9 kg, contribuyendo a la producción de biomasa de las gramíneas acompañantes en el SSPi.

Suplementos múltiplos para novilhas de corte a pasto no período seco: características nutricionais

The objective was to evaluate levels of multiple supplements supplied to beef heifers in low supply of pasture on intake and nutrients digestibility, pH and concentration of ruminal ammonia nitrogen, nitrogen balance, synthesis and microbial efficiency. Five Nellore heifers with initial body weight of 344.00 ± 21.10 kg and average initial age of 22 months were used. The following supplements were evaluated as fed to the animals: control (mineral supplement) and supplementation levels of 2, 4, 6 and 8 kg/animal/day, composing the following percentages of body weight (BW): 0.55, 1.11, 1.66 and 2.22%, respectively. The experimental design was a Latin square with five replications and five supplements. Intakes of total dry matter, crude protein (CP) and total digestible nutrients, and total apparent digestibility of dry matter, crude protein, total carbohydrates and no fiber carbohydrates increased linearly (P &lt;0.0001) and dry matter intake of forage decreased (P &lt;0.0001) with supplementation levels. Supplementation strategies promoted reduction on ruminal pH (P = 0.0343) and increased concentration of ruminal ammonia nitrogen (NH3-N) (P = 0.0004) before the supply of supplements, and after, this NH3-N presented quadratic behavior (P = 0.0023). Nitrogen intake, excretion of urea in urine and nitrogen excretion in feces increased linearly (P &lt;0.0001) according to supplementation levels. The supply of high levels of multiple supplements reduces forage intake and presents itself as an alternative to cattle maintained in a systems with low supply of pasture in the dry season.

Individual mineral supplement intake by ewes swath grazing or confinement fed pea-barley forage

Previous research has reported high variation in intake of self-fed protein and/or energy supplements by individual animals, however little is known about variation in consumption of mineral supplements. Sixty mature range ewes (non-pregnant, non-lactating) were used in a completely randomized design repeated 2 years to determine if feeding method of intercropped field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) forage (swath grazed or fed as hay in confinement) affected individual ewe mineral consumption. Thirty ewes were allocated to 3 confinement pens (10 ewes/pen) and 30 ewes were allocated to 3 grazing plots (10 ewes/plot). Ewes had ad libitum access to feed, water, and a mineral supplement containing 1% titanium dioxide as an external marker. Forage dry matter intake (DMI) was calculated using estimates of fecal output, and in vitro 48-h forage DM digestibility. Ewe supplement intake was determined from fecal and supplement Ti concentrations, and fecal output. Forage and mineral intakes were analyzed using ewe as the experimental unit, and plot or pen as the experimental unit for intake variation. A year×treatment interaction (P<0.01) existed for DM forage and mineral intake. Ewes in confinement consumed more forage DM than grazing ewes in 2010, but less than grazing ewes in 2011. Mean mineral intake was highest (P<0.01) by grazing ewes in 2011 and 2010 (average 69g/day), intermediate by confinement ewes in 2010 (57g/day), and lowest by confinement ewes in 2011 (31g/day). A year×treatment interaction (P=0.05) existed for mineral intake CV which was higher (P=0.04) for confinement ewes in 2011 (67 vs. 34%), but was not different (P>0.05) between treatments in 2010. In this study, variation in individual ewe intake of mineral supplement was large in both grazing ewes and ewes fed hay in confinement.

Evaluation of external markers to estimate fecal excretion, intake, and digestibility in dairy cows.

The objective of this study was to compare the use of an external marker titanium dioxide (TiO₂) as an alternative to chromic oxide (Cr₂O₃) in dairy cows. Four dairy cows were allocated in individual pens and fed concentrate supplement and Pennisetum purpureum cv. Cameroon cut daily. Fecal excretion, forage and total dry matter (DM) intakes, and digestibility were measured and estimated with TiO₂ and Cr₂O₃. Chromic oxide overestimated and TiO₂ tended to overestimate fecal excretion compared with total fecal collection. Forage and total DM intakes were overestimated by Cr₂O₃. The apparent DM digestibility was underestimated by Cr₂O₃ and TiO₂. The organic matter (OM) digestibility was underestimated by both markers. There were greater mean bias, mean squared prediction error, and root of the mean squared prediction errors for all parameters estimated with Cr₂O₃. In conclusion, estimates using TiO₂ were more precise and accurate indicating that it can replace Cr₂O₃ as an external marker for grazing dairy cows.

Consumo, tempo de pastejo e desempenho de novilhos suplementados em pastos de Brachiaria decumbens, durante o período seco

The objective of this study was to evaluate the supplementation with mineral salt (SALT), proteic and mineral salt (PMS) and energetic-proteic supplement (EPS), respectively, provided ad libitum, 0.2% and 0.8% of body weight (BW) on dry matter forage intake (DMFI), grazing time and performance of cattle during the dry season (June to August). The performance was evaluated in 48 steers with an average initial BW of 310 + 50 kg, distributed in 15 paddocks of Brachiaria decumbens, with the DMFI and grazing time evaluated in 18 steers. Compared with animals consuming SALT, the DMFI was reduced in 26% for those supplemented with EPS, without differences with the animals supplemented with PMS. Grazing time was reduced in 16 and 90 minutes day-1, respectively, for animals supplemented with PMS and EPS, compared to animals without supplementation. There was an interaction (P&lt;0.01) treatment x period for average daily gain (ADG) not being different in the initial month (0.76 kg animal-1 day-1), however, in the second month the animals receiving SALT gained 0.07 kg animal-1 day-1, significantly (P&lt;0.01) less than the animals of PMS and EPS, in which the ADG was 0.56 and 0.73 kg animal-1 day-1, respectively. The use of pasture supplementation with PMS and EPS is interesting to aim higher weight gains of cattle during the dry season, but supplementation with PMS did not alter the DMFI, being one efficient way to supply the nutrients to the animals during this period.

Methane emissions among individual dairy cows during milking quantified by eructation peaks or ratio with carbon dioxide

The aims of this study were to compare methods for examining measurements of CH4 and CO2 emissions of dairy cows during milking and to assess repeatability and variation of CH4 emissions among individual dairy cows. Measurements of CH4 and CO2 emissions from 36 cows were collected in 3 consecutive feeding periods. In the first period, cows were fed a commercial partial mixed ration (PMR) containing 69% forage. In the second and third periods, the same 36 cows were fed a high-forage PMR ration containing 75% forage, with either a high grass silage or high maize silage content. Emissions of CH4 during each milking were examined using 2 methods. First, peaks in CH4 concentration due to eructations during milking were quantified. Second, ratios of CH4 and CO2 average concentrations during milking were calculated. A linear mixed model was used to assess differences between PMR. Variation in CH4 emissions was observed among cows after adjusting for effects of lactation number, week of lactation, diet, individual cow, and feeding period, with coefficients of variation estimated from variance components ranging from 11 to 14% across diets and methods of quantifying emissions. No significant difference was detected between the 3 PMR in CH4 emissions estimated by either method. Emissions of CH4 calculated from eructation peaks or as CH4 to CO2 ratio were positively associated with forage dry matter intake. Ranking of cows according to CH4 emissions on different diets was correlated for both methods, although rank correlations and repeatability were greater for CH4 concentration from eructation peaks than for CH4-to-CO2 ratio. We conclude that quantifying enteric CH4 emissions either using eructation peaks in concentration or as CH4-to-CO2 ratio can provide highly repeatable phenotypes for ranking cows on CH4 output.

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 (R(2) = 0.599) and protein (R(2) = 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.

&lt;b&gt;Performance of dairy heifers grazing on &lt;i&gt;Urochloa decumbens&lt;/i&gt; pastures deferred for two periods&lt;/b&gt;

Voluntary intake and performance of dairy heifers grazing on Urochloa decumbens pastures with two deferral periods are evaluated. The totally randomized experimental design consisted of two treatments and seven replications, with two deferral periods: T1 = 95 and T2 = 140 days. Fourteen Holstein-Zebu heifers, average body weight (BW) 300 kg, were used. Intake of forage dry matter was 2.5% and 1.2 BW respectively for treatments 95 and 140 days. In treatment T2 the animals had an intake of only 139.5 g of CP, due to low nutrient content, or rather, 3.4% of CP in the forage available. There was an intake of NDF of 1.7% and 1.0 of BW for T1 and T2, respectively. The average daily weight gain was 785.8 g day -1 for T1 and average weight loss of -31.1 g day -1 for T2. Deferral of pastures Urochloa decumbens for 95 days to allow a 1.5 lodging index provides greater consumption and performance of dairy heifers. Deferral of Urochloa decumbens pastures to allow a 1.5 lodging index provides greater intake and performance of dairy heifers.

Evaluation of different feed intake models for dairy cows

The objective of the current study was to evaluate feed intake prediction models of varying complexity using individual observations of lactating cows subjected to experimental dietary treatments in periodic sequences (i.e., change-over trials). Observed or previous period animal data were combined with the current period feed data in the evaluations of the different feed intake prediction models. This would illustrate the situation and amount of available data when formulating rations for dairy cows in practice and test the robustness of the models when milk yield is used in feed intake predictions. The models to be evaluated in the current study were chosen based on the input data required in the models and the applicability to Nordic conditions. A data set comprising 2,161 total individual observations was constructed from 24 trials conducted at research barns in Denmark, Finland, Norway, and Sweden. Prediction models were evaluated by residual analysis using mixed and simple model regression. Great variation in animal and feed factors was observed in the data set, with ranges in total dry matter intake (DMI) from 10.4 to 30.8kg/d, forage DMI from 4.1 to 23.0kg/d, and milk yield from 8.4 to 51.1kg/d. The mean biases of DMI predictions for the National Research Council, the Cornell Net Carbohydrate and Protein System, the British, Finnish, and Scandinavian models were −1.71, 0.67, 2.80, 0.83, −0.60kg/d with prediction errors of 2.33, 1.71, 3.19, 1.62, and 2.03kg/d, respectively, when observed milk yield was used in the predictions. The performance of the models were ranked the same, using either mixed or simple model regression analysis, but generally the random contribution to the prediction error increased with simple rather than mixed model regression analysis. The prediction error of all models was generally greater when using previous period data compared with the observed milk yield. When the average milk yield over all periods was used in the predictions of feed intake, the increase in prediction error of all models was generally less than when compared with previous period animal data combined with current feed data. Milk yield as a model input in intake predictions can be substantially affected by current dietary factors. Milk yield can be used as model input when formulating rations aiming to sustain a given milk yield, but can generate large errors in estimates of future feed intake and milk production if the economically optimal diet deviates from the current diet.