Forage-based Diets Research Articles

Quantification of melamine absorption, distribution to tissues, and excretion by sheep1

Eight Döhne Merino rams were used to quantify apparent absorption, distribution to tissues, and excretion of dietary melamine in sheep. Two batches of concentrate pellets were made; one (CON) contained corn gluten meal with no detectable melamine and the other (MEL) contained corn gluten meal that was previously found to be highly contaminated with melamine at 15,117 mg/kg. The MEL pellets contained 1,149 mg/kg of melamine. During a 10-d adaptation period, all the animals received a forage-based diet supplemented with 600 g/d of the CON pellets. This was followed by an 8-d collection period during which 6 of the animals received MEL pellets and 2 received CON pellets. Melamine intake of sheep that received MEL pellets was 0.69 g/d. Blood samples were taken before first ingestion of MEL pellets on d 1 and again on d 3, 6, and 8 of the collection period for melamine and serum creatinine analyses. Feces and urine were collected quantitatively over the 8 d for proximate and melamine analyses. All the animals were slaughtered at the end of the trial, and samples of the LM, liver, kidneys, and abdominal fat were taken for melamine analysis. Data of the 2 sheep that received CON pellets for the duration of the trial confirmed that no melamine was detected in any of the samples, and no statistical analyses were performed on these data. The apparent digestibility or efficiency of absorption of ingested melamine was 76.7%. Melamine was detected in the urine, blood, muscle (LM), and fat tissue of all the sheep that received MEL pellets. Serum melamine concentrations reached 5.4 mg/kg on d 8 of the collection period, and the meat (LM) contained 9.6 mg/kg of melamine. Calculations on the partitioning of ingested melamine suggested that urine is the major excretion route accounting for 53.2%, whereas feces accounted for 23.3% of ingested melamine. Approximately 3.5% of the ingested melamine was detected in muscle. It was concluded that ingested melamine is highly absorbable from the small intestine and that a pathway exists for the distribution of dietary melamine to meat.

Effects of Concentrate- Versus Forage-Based Finishing Diet on Carcass Traits, Beef Palatability, and Color Stability in Longissimus Muscle from Angus Heifers

ABSTRACT The objective was to determine the effects of finishing diet on carcass traits, beef palatability, and color stability of LM from Angus heifers. Half-siblings were obtained from a herd selected for increased intramuscular fat, ribeye area, and percentage of retail product, and decreased backfat and were randomly assigned to a forage- or concentrate-based finishing diet. Longissimus muscle samples (n = 155) were obtained and fabricated into steaks for trained sensory panel, Warner-Bratzler shear force, thiobarbituric acid-reactive substances (TBARS), and simulated retail display evaluation. Data were analyzed using the MIXED procedures of SAS using slaughter age as a covariate. Carcasses from concentrate-finished heifers had greater adjusted fat thickness (1.86 vs. 0.87 cm), greater percentage of KPH (2.14 vs. 1.35%), greater numerical YG (3.38 vs. 2.25), and greater marbling scores (modest 90 vs. traces 70) than forage-finished heifers (P 0.05) between diets after 7 d in retail display. Of the color measurements, only L* values differed between diets; they were greater (38.36 vs. 32.25; P

Growth performance and carcass characteristics of Dorset lambs fed different concentrates: Forage ratios or fresh grass

Forty male Dorset lambs were divided at weaning into four dietary treatment groups: ad libitum concentrates (C), restricted concentrates (RC), zero grazing (ZGR) and grazing (GR). All the lambs were weaned and slaughtered at similar weights, 24 kg for weaning and 47 kg for slaughter. The average daily gain (ADG) of the RC-fed lambs (347 g/d) was lower than that of the C-fed lambs (449 g/d) but higher than that of the lambs in the ZGR (267 g/d) and GR (295 g/d) treatments ( P < 0.0001). There was no significant difference between the ZGR and GR lambs for ADG. To reach slaughter weight, the RC and ZGR-GR lambs required 20 and 40 additional days, respectively ( P < 0.0001), compared to the C-fed lambs. The lambs fed C had better feed efficiency than the lambs on mixed (RC) or forage-based (ZGR, GR) diets ( P < 0.0001). Values for body score, in vivo ( P < 0.05) back fat thickness ( P < 0.0001), and back fat thickness after slaughter ( P < 0.05) were higher in the carcasses of the C-fed lambs compared to the values obtained with the other dietary treatments. No difference was observed among the treatments for leg and shoulder muscle classification ( P > 0.05). However, the loins of the C-fed lambs obtained a higher classification score than those of the lambs raised under ZGR or GR ( P < 0.05). Carcass yield was greater ( P < 0.0001) for the C-fed lambs compared to the RC and ZGR lambs, mostly because of a lighter full digestive tract ( P = 0.0007). The carcasses of the grazing lambs obtained a lower global rating classification ( P < 0.05), mainly because of a lack of back fat thickness. Feeding system had a significant effect on subcutaneous fat lightness (L*) ( P = 0.004) and yellowness (b*) ( P < 0.0001) but did not affect redness (a*). Overall, forage-based diets may prevent excessive carcass fat in heavy lambs while producing similar muscle development, resulting in a leaner product for consumers.

Decrease of ruminal methane production in Rusitec fermenters through the addition of plant material from rhubarb (Rheum spp.) and alder buckthorn (Frangula alnus)

Roots of rhubarb (Rheum spp.) and bark of alder buckthorn (Frangula alnus) were tested as feed additives for decreasing ruminal methane production released from anaerobic fermentation of a forage-based diet in a rumen-simulating fermenter (Rusitec). Sixteen fermentation units (vessels) were set up for the experiment lasting 19 d. Treated vessels were supplied with 1g/d of rhubarb or alder buckthorn (4 vessels per plant species); another 4 vessels received 12μM sodium monensin (positive control), and the remaining 4 vessels were controls (no additive). Upon termination of the experimental period, batch cultures were inoculated with the liquid contents of the vessels for examining in vitro fermentation kinetics of cellulose, starch, barley straw, and the same substrate used in the Rusitec cultures. Monensin induced changes in fermentation in agreement with those reported in the literature, and inocula from those cultures decreased the fermentation rate and total gas produced in the gas kinetics study. Rhubarb decreased methane production, associated with limited changes in the profile of volatile fatty acids throughout the duration of the study, whereas digestibility and total volatile fatty acids production were not affected. Rhubarb inocula did not affect gas production kinetics except for cellulose. Alder buckthorn decreased only methane concentration in fermentation gas, and this effect was not always significant. The use of rhubarb (milled rhizomes of Rheum spp.) in the diets of ruminants may effectively modulate ruminal fermentation by abating methane production, thus potentially involving productive and environmental benefits.

Fatty acid profile of hind leg muscle in female and male nutria (Myocastor coypus Mol.), fed green forage diet

The study describes the profile of fatty acids in hind leg muscle of 18 female and 12 male nutria reared on an extensive system farm in eastern Poland with a diet based on fresh forage. When compared to results from nutrias from an intensive production system from the literature, the forage-fed animals had lower proportions of saturated fatty acids, and higher proportions of n3-fatty acids in their muscle tissue; in particular, n6:n3-fatty acid ratios were lower (2.6-3.0) in forage-fed animals compared to intensively reared animals (16.8-28.9). These findings underline that using forage-based diets is feasible in nutrias, and an economic way to improve the fatty acid composition of their meat.

Effects of winter growing program on visceral organ mass, composition, and oxygen consumption of beef steers during growing and finishing12

The purpose of this experiment was to investigate the effects of winter growing program on organ mass, composition, and oxygen consumption in beef steers. A total of 46 steers were used for the experiment. Four steers were randomly selected as an initial slaughter group. Remaining steers were randomly allotted to 1 of 4 treatment groups: 1) fed a high-concentrate diet for ad libitum intake (CF); 2) grazed on wheat pasture (WP); 3) fed a sorghum silage-based growing diet (SF); or 4) program fed a high-concentrate diet (PF). Steers in the WP, SF, and PF groups were managed to achieve approximately equal rates of BW gain during the growing phase. After the growing phase (112 d), steers in the WP, SF, and PF treatments were adapted to a high-concentrate diet for finishing. Steers from all treatments were slaughtered at a fat thickness of 1.27 cm as estimated by ultrasound. In addition, 6 steers from each treatment were randomly selected for slaughter at the end of the growing phase. Weights of all individual organs were measured and tissue samples of duodenum and liver collected. At the end of the growing phase, WP steers had greater (P < 0.05) small intestine, liver, and kidney mass than SF and PF steers. In contrast, mesenteric fat mass and total visceral fat content were greatest (P < 0.01) for PF, intermediate for SF, and least for WP steers. Mass of total viscera and total splanchnic tissues (TST) did not differ (P > 0.10) among treatments. At final slaughter, mass of mesenteric fat, total viscera, and TST were similar among treatments, but liver weights remained greatest (g/kg of empty BW; P < 0.01) for WP steers. There were no differences in oxygen consumption of duodenum or liver tissue on an equal weight basis (microL.min(-1.)g(-1)) at the end of either period. Growing program affected mass of components of the TST at the end of the growing phase, which contributed to differences in rate of splanchnic organ growth during finishing. We conclude that program feeding a high-concentrate diet during the growing phase may result in greater ADG and G:F during the subsequent finishing period compared with forage-based diets due to less accretion of visceral organ mass resulting in reduced maintenance energy requirements during finishing.

204 FATTY ACID COMPOSITION OF FOLLICULAR FLUID FROM DAIRY COWS FED TROPICAL FORAGE-BASED DIETS SUPPLEMENTED WITH INCREASING LEVELS OF SOYBEAN OIL

Recent studies have shown that dietary supplementation with sources rich in polyunsaturated fatty acids (PUFA) can improve reproductive perfor-mance of lactating dairy cows. However, no studies have reported the fatty acids composition of follicular fluid (FF) from dairy cows fed high-PUFA diets. This study aimed to evaluate the fatty acids composition of FF from dairy cows fed tropical forage-based diets containing different levels of soybean oil (SO). Four multiparous Holstein-Zebu cows in midlactation (90 ± 25 days in milk) were assigned to 1 of the following dietary treatments (on a dry matter basis): (1) T1 (control) = no SO; (2) T2 = diets containing 1.5% of SO; (3) T3 = diets containing 3.0% of SO; and (4) T4 = diets containing 4.5% of SO. Diets were composed of chopped elephant grass and a concentrate mixture and the forage concentrate ratio was 55 : 45 (dry matter basis). The experimental design was a 4 × 4 Latin square in which each period lasted 21 days. All cows received intravaginal progesterone-releasing devices and follicular waves were synchronized with 0.5 mg of gonadorelin. The FF from dominant follicles was collected by transvaginal ultrasound-guided aspiration on the last day of each period (Day 21) and centrifuged (10000 × g, 1 min) and the supernatant was frozen at -80°C until fatty acid analysis. Extraction and methylation of fatty acids in FF were performed according to the 1-step simplified method described by Masood A et al. (2005 J. Lipid Res. 46, 2299-2305). The fatty acid profile from FF was determined by gas chromatography as described by Cruz-Hernandez C et al. (2007 J. Dairy Sci. 90, 3786-3801). Treatment effects were determined by regression analysis using the REG procedure of SAS (SAS Institute, Cary, NC, USA) and declared significant at P &lt; 0.05. Nearly 30 different fatty acids (70% of the total area) were identified in the FF samples. The most representative fatty acids (% total area) for the 4 dietary treatments (T1, T2, T3, and T4, respectively) were C18 : 2 cis - 9, cis - 12 (19.8, 20.3, 16.1, and 24.2), C18 : 0 (17.7, 16.6, 19.5, and 16.8), C16 : 0 (12.2, 10.7, 11.3, and 17.8), and C18 :1 cis - 9 (6.5, 7.3, 5.5, and 7.7). Inclusion of SO in the diet linearly reduced (P &lt; 0.05) concentrations of C16 : 1 cis - 9 (0.8, 0.7, 0.4, and 0.5) and C20 : 3 (1.2, 1.1, 0.5, and 0.7), but linearly increased (P &lt; 0.05) concentrations of C18 : 1 trans - 11 (0.4, 0.4, 0.6, and 1.4), C18 : 1 cis - 11 (0.4, 0.5, 0.4, and 0.9), and C18 : 1 cis - 12 (0.2, 0.5, 0.5, and 0.7) isomers in FF. The increase in the concentration of C18 : 1 trans - 11 in FF from cows fed higher levels of SO was not accompanied by an increase in the proportion of CLA cis - 9, trans - 11 (0.9, 1.0, 0.7, and 0.9 for T1, T2, T3, and T4, respectively). It suggests the absence or low activity of A9-desaturase enzyme in the follicular environment, unlike that observed in the mammary gland. In general, our results indicate that fatty acid composition of follicular fluid from lactating dairy cows is sensitive to changes in dietary supply of PUFA. Financial support: FAPEMIG (CVZ1815/06).

Effect of dietary cation-anion difference on measures of acid-base physiology and performance in beef cattle1

Dietary constituents can affect cow acid-base physiology and uterine pH. Dietary cation-anion difference (DCAD) has been shown to affect cow acid-base physiology, but the effect on uterine pH has not been demonstrated. The objective of this work was to determine if DCAD [(Na + K + 0.15Ca + 0.15Mg) - (Cl + 0.60S + 0.50P)] could affect cow DMI, acid-base physiology, and uterine pH, and second, to determine if dietary supplements could alleviate any negative effects of DCAD on these variables. In Exp. 1, 21 cows were utilized to determine the effect of a negative DCAD (-0.9 mEq/100 g of DM; low-DCAD) or positive DCAD (+25.0 mEq/100 g of DM; high-DCAD) diet on cow BW, DMI, and pH of blood, urine, and uterine flush fluid. In Exp. 2, 21 cows were randomly allotted to 1 of 3 treatments: control (-3.1 mEq/100 g of DM), molasses (+2.9 mEq/100 g of DM), or molasses+buffer (+25.8 mEq/100 g of DM) to determine if supplemental liquid molasses or liquid molasses with a buffer could alleviate the effects of a negative DCAD, forage-based diet. Cows were individually fed their respective diets for 42 d in both experiments. Cow BW, blood, urine, and uterine flush were collected on d 0, 21, and 42 during both experiments. Cow ADG was not different (P = 0.71) in Exp. 1 or Exp. 2 (P = 0.47). Hay DMI did not differ (P < 0.70) between high-DCAD and low-DCAD cows before d 28, but was greater (P < 0.001) for high-DCAD cows after d 28 in Exp. 1. In Exp. 2, mean hay DMI did not differ (P = 0.39) among treatments. In Exp. 1, a treatment x day interaction (P < 0.05) was apparent for blood, pH, base excess, bicarbonate, pCO(2), and urine pH. Blood gas and pH measures peaked on d 21 for high-DCAD and declined from d 0 to 42 in low-DCAD cows. High-DCAD cows had greater (P = 0.08) uterine flush pH compared with low-DCAD cows. In contrast, during Exp. 2 there were no differences (P > 0.14) among treatments for blood, pH, base excess, pCO(2), or uterine flush pH. Urine pH exhibited a treatment x day interaction (P < 0.0001). On d 21 molasses supplemented cow urine pH was greater (P < 0.0001) than control cows, whereas on d 42 molasses+buffer had greater (P = 0.01) urine pH compared with control and molasses cows. Dietary cation-anion difference and the use of molasses-based supplements had minimal effect on forage-fed beef cow DMI. However, DCAD has the capacity to alter forage-fed beef cow acid-base physiology and potentially affect uterine physiology.

Effects of increasing levels of corn distillers dried grains with solubles to steers offered moderate-quality forage1

Supplementation of forage-fed livestock has been studied for decades; however, as by-products become available research is needed to determine optimal feeding rates for increased efficiency. Five ruminally and duodenally cannulated beef steers (446 +/- 42 kg of initial BW) were used in a 5 x 5 Latin square to evaluate effects of increasing level of supplemental corn distillers dried grains with solubles (DDGS; 25.4% CP, 9.8% fat, DM basis) on DMI, rate and site of digestion, ruminal fermentation, and microbial efficiency. Diets consisted of ad libitum quantities of moderate-quality smooth brome hay (10.6% CP; DM basis), free access to water and trace mineral salt block, and 1 of 5 levels of DDGS (0, 0.3, 0.6, 0.9, and 1.2% of BW daily of DDGS; DM basis). Diets were formulated to meet or exceed the estimated rumen degradable protein requirements (assumed microbial yield = 10.5%). All supplements were fed at 0600 h before forage was fed. Steers were adapted to diets for 14 d followed by a 7-d collection period. Hay OM intake decreased (linear; P < 0.001), whereas total OM intake increased (linear; P < 0.001) with increasing DDGS level. Total CP intake, duodenal OM and CP flows, and total tract OM and NDF digestibilities increased (linear; P <or= 0.01) with increasing level of DDGS. Apparent ruminal and true ruminal CP digestibilities increased linearly (P <or= 0.007), and total-tract CP digestibility increased quadratically (P = 0.02) with increasing DDGS level. Average ruminal pH was not different (P = 0.89) among treatments. Ammonia concentration increased (quadratic; P = 0.02) with increasing DDGS. Acetate proportions (molar %) decreased linearly (P < 0.001), whereas butyrate (molar %) increased linearly (P = 0.007), and propionate (molar %) increased quadratically (P = 0.04) with increasing DDGS. Ruminal DM fill decreased quadratically (P = 0.03), whereas fluid dilution rate tended to increase cubically (P = 0.08) with increasing DDGS. In situ rate of hay and DDGS DM disappearance responded cubically (P <or= 0.03) with greatest disappearance occurring with the 0.9% treatment. In situ rate of ruminal CP degradation of hay and DDGS increased (linear; P <or= 0.003) with increasing DDGS. Feeding 0.3% up to 1.2% of BW daily of DDGS as a supplement to forage-based diets resulted in no adverse effects on forage digestion or fermentation and resulted in increased nutrient supply in steers fed moderate-quality smooth brome hay.

Effect of Methionine Source and Level on Performance of Growing Beef Calves Consuming Forage-Based Diets

The effects of level and source of supplemental sulfur-containing amino acids (SAA) on the performance of growing beef calves were evaluated. In Exp. 1, 128 calves (BW = 277 ± 20 kg) were offered supplements containing 0, 2, 4, and 6 g/d of SAA from corn gluten meal (CGM), or 2, 4, 6, or 8 g/d of SAA using 88% 2-hydroxy-4-methylthio butanoic acid (Alimet, Novus International Inc. St. Louis, MO) in liquid molasses slurries for 113 d. Hay was offered as large round bales; supplements were limit-fed at 2.1 kg DM/d. Calf ADG was greater (P < 0.05) for calves supplemented with CGM or 2 and 6 g/d from Alimet than for control calves. Calves provided 2, 4, and 6 g/d of SAA from Alimet and 4 g/d of SAA from CGM had greater (P < 0.05) TDN intake than control calves. In Exp. 2, 72 heifers (BW = 371 ± 3 kg) were assigned to 1 of 3 soybean hull-based supplements that provided 0, 7.5, or 15 g/d of Alimet, which supplied 0, 2.5, or 5.3 g/d of additional SAA. Heifers were offered ad libitum access to water and hay; supplements were limit-fed at 2.3 kg DM/d. Reproductive tract score and pelvic area were measured on d 85. Supplementing 15 g/d of Alimet increased (P < 0.05) ADG during the first 30 d compared with the control diet. Heifers fed 15 g of Alimet daily tended to have greater (P = 0.08) reproductive tract scores. Alimet was effective as a source of supplemental SAA for improving the performance of growing beef calves provided forage-based diets.

Building beef cow nutritional programs with the 1996 NRC beef cattle requirements model.

Designing a sound cow-calf nutritional program requires knowledge of nutrient requirements, diet quality, and intake. Effectively using the NRC (1996) beef cattle requirements model (1996NRC) also requires knowledge of dietary degradable intake protein (DIP) and microbial efficiency. Objectives of this paper are to 1) describe a framework in which 1996NRC-applicable data can be generated, 2) describe seasonal changes in nutrients on native range, 3) use the 1996NRC to predict nutrient balance for cattle grazing these forages, and 4) make recommendations for using the 1996NRC for forage-fed cattle. Extrusa samples were collected over 2 yr on native upland range and subirrigated meadow in the Nebraska Sandhills. Samples were analyzed for CP, in vitro OM digestibility (IVOMD), and DIP. Regression equations to predict nutrients were developed from these data. The 1996NRC was used to predict nutrient balances based on the dietary nutrient analyses. Recommendations for model users were also developed. On subirrigated meadow, CP and IVOMD increased rapidly during March and April. On native range, CP and IVOMD increased from April through June but decreased rapidly from August through September. Degradable intake protein (DM basis) followed trends similar to CP for both native range and subirrigated meadow. Predicted nutrient balances for spring- and summer-calving cows agreed with reported values in the literature, provided that IVOMD values were converted to DE before use in the model (1.07 x IVOMD - 8.13). When the IVOMD-to-DE conversion was not used, the model gave unrealistically high NE(m) balances. To effectively use the 1996NRC to estimate protein requirements, users should focus on three key estimates: DIP, microbial efficiency, and TDN intake. Consequently, efforts should be focused on adequately describing seasonal changes in forage nutrient content. In order to increase use of the 1996NRC, research is needed in the following areas: 1) cost-effective and accurate commercial laboratory procedures to estimate DIP, 2) reliable estimates or indicators of microbial efficiency for various forage types and qualities, 3) improved estimates of dietary TDN for forage-based diets, 4) validation work to improve estimates of DIP and MP requirements, and 5) incorporation of nitrogen recycling estimates.

The Substitution of Corn with Soybean Hulls and Subsequent Impact on Digestibility of a Forage-Based Diet Offered to Beef Cattle

To better understand the impact of corn and soybean hull supplementation on bermudagrass hay utilization, a digestion trial was conducted using 6 ruminally cannulated steers receiving bermudagrass hay supplemented with soybean hulls (HULLS), cracked corn (CORN), or soybean hulls and cracked corn (MIX; 75% and 25%, respectively) in a 3 × 3 Latin rectangle arrangement. Total DMI was not different among treatments as measured by kilograms per day (P = 0.06; from 6.52 to 7.48 kg/d) and percentage of BW per day (P = 0.67; from 2.41 to 2.79% BW/d). Similarly, hay DMI did not differ but tended to decrease (P = 0.06) among steers receiving HULLS (2.88 kg/d; 1.08% BW/d). Apparent NDF, ADF, and hemicellulose digestibilities were greatest (P < 0.001) among steers consuming HULLS (64.92, 65.39, and 64.01%, respectively) or MIX (62.66, 63.21, and 61.78%, respectively). Total ruminal VFA production was not different (P = 0.97) among treatments (232.6 to 289.7mM); likewise, ruminal pH did not differ (P = 0.31; 6.8 to 6.0). Acetate-to-propionate ratios did not differ (P = 0.46; 3.7 to 4.7), whereas NH3-N concentrations were greater (P = 0.05) among steers consuming HULLS and decreased for all diets 4 to 8h post-feeding. Data seem to indicate that replacing a portion of corn with soybean hulls may successfully improve fiber digestion and improve ruminal N utilization.

Effects on fluid balance, digestion and exercise response in Standardbred horses fed silage, haylage and hay

The objectives were to investigate the effects on fluid balance, digestion and exercise response in Standardbred horses in race training when feeding silage, haylage or hay-only diets. In experiment (exp) 1, five Standardbred geldings were fed forage-only diets: hay (82% dry matter, DM) and silage (45% DM) for 23 days in a crossover design. Total collection of faeces and urine was performed. In exp 2, six Standardbred geldings were fed forage-based diets: haylage (68% DM) and silage (41% DM) for 17 days in a crossover design. On day 17, an incremental interval exercise test was performed on an oval racetrack. In exp 1, horses drank more on the hay than on the silage diet, but total water intake (drinking+water in feed) was higher and resting values of total plasma protein (TPP) was lower on the silage diet. Total water output per day did not differ and therefore the estimated evaporation was larger on the silage than the hay diet. The apparent digestibility was higher on the silage than the hay diet. In exp 2, heart and respiratory rate, TPP and lactate and blood pH did not differ between the haylage and silage diets during and after the exercise test. In conclusion, feeding silage did not affect faecal water content, but apparent digestibility and estimated evaporative fluid loss were higher on the silage diet compared with the hay diet. The silage did not adversely affect the response to intensive exercise compared with haylage. However, the estimated higher evaporative fluid loss on the silage diet compared with the hay diet might cause an unnecessary challenge during more prolonged exercise.

Milk yield, milk composition, eating behavior, and lamb performance of ewes fed diets containing soybean hulls replacing coastcross (Cynodon species) hay1,2

The objective of this experiment was to evaluate the effects of replacing coastcross hay NDF by soybean hull (SH) NDF on the lactation performance and eating behavior of ewes and also on the performance of their lambs. Fifty-six Santa Inês lactating ewes (56.1 +/- 6.8 kg of initial BW; mean +/- SD) were penned individually and used in a randomized complete block design with 14 blocks and 4 treatments. Diets were formulated to provide similar concentrations of NDF (56%) and CP (16%). The SH NDF replaced 33 (SH33), 67 (SH67), or 100% (SH100) of the NDF contributed by coastcross hay in a 70% forage-based diet (SH0), resulting in SH inclusion rates of 0, 25, 54, and 85% of the dietary DM. Once a week, from the second to the eighth week of lactation (weaning time), ewes were separated from their lambs, stimulated by a 6-IU i.v. oxytocin injection, and hand milked to empty the udder. After 3 h, milk production was obtained after the same procedure. Quadratic effect for milk production (142.4, 179.8, 212.6, and 202.9 g/3 h) and cubic effect for DMI (2.27, 2.69, 3.25, and 3.00 kg/d) were observed as SH inclusion increased from 0 to 85% of the dietary DM. Milk fat (7.59, 7.86, 7.59, and 7.74%), protein (4.53, 4.43, 4.40, and 4.55%), and total solids (18.24, 18.54, 18.39, and 18.64%) did not differ among the 70% forage-based diet and diets with SH NDF replacing 33, 67, or 100% of the NDF. A linear increase in lactose concentration was observed with SH inclusion. Ewe BW gain during the trial showed a cubic response (0.37, 0.03, 4.80, and 2.80 kg) with SH inclusion. The preweaning ADG of lambs increased linearly, and ADG of lambs after weaning decreased linearly with SH inclusion. Final BW of lambs (2 wk after weaning) did not differ among treatments. Eating behavior observations were conducted with 44 ewes. The same facilities, experimental design, dietary treatments, and feeding management were used. Observations were visually recorded every 5 min for a 24-h period when ewes were 46 +/- 6.8 d in milk. Eating time (min/d, min/g of DMI, and min/g of NDF intake) and time expended in rumination and chewing activities (min/g of DMI and min/g of NDF intake) decreased linearly with the addition of SH in the diets. The inclusion of SH improved DMI and milk production, also reflecting on the BW of lambs at weaning. Milk performance was not affected when SH NDF replaced 100% of hay NDF.

Fecal crude protein content as an estimate for the digestibility of forage in grazing sheep

Regression equations were developed to predict the organic matter (OM) digestibility of forage-based diets from contents of crude protein (CP) and acid detergent soluble CP (ADSCP) in feces, with data (721 observations of nine types of diets) obtained from in vivo digestibility trials ( n = 159) with sheep conducted at the Federal Research Centre of Agriculture, Braunschweig, Germany and in Inner Mongolia, China. Using the non-linear mixed model procedure, the developed regression equation was: OM digestibility = 0.899 − 0.644 × exp (−0.5774 × fecal CP (g/kg OM)/100). The probability values of estimated parameters of the equation were higher than 0.05, and a random effect of diet was not observed (P=0.131). The mean prediction error (MPE) as proportion of observed mean was 0.071, indicating that the equation fits the data reasonably well. The equation slightly under-predicts the OM digestibility with a small mean bias of −0.014, representing 0.089 of the total mean square prediction error (MSPE). The difference between estimated and measured OM digestibility was mainly caused by random variation (0.899). This indicates that the developed equation is accurate and can be used to predict the OM digestibility of forage ingested by sheep grazing on heterogeneous pasture. Although inclusion of ADSCP instead of CP in the prediction equation results in a slightly lower under-prediction (mean bias of −0.011, representing 0.062 of MSPE), the prediction accuracy is not improved.

Substituição do milho por casca de soja: consumo, rendimento e características de carcaça e rendimento da buchada de caprinos

Thirty-two Anglo-Nubian crossbred castrated male goats were utilized in a completely randomized design to evaluate the effect of replacing corn with soybean hull in diets based on cactus forage (Nopalea cochenilifera Salm Dyck) at levels of 0, 33, 66 and 100%, measured for intake and carcass yield. The rise in soybean hull levels increased neutral detergent fiber intake linearly (p < 0.05) and reduced the intake of non-fiber carbohydrates. However, live slaughter weight, empty body weight, freezing losses, hot carcass weight and yield, cold carcass and “buchada” (gut) were not influenced. Fasting losses presented quadratic behavior (p < 0.05) while true and freezing yields increased linearly (p < 0.05). The carcass compactness index, the cuts and their respective yields were not influenced by the replacement of corn with soybean hull level, except for the shoulder cut, which presented quadratic behavior (p < 0.05). Total replacement of corn reduced feeding costs by 15.4%. Soybean hull can represent an alternative in the feeding of goats in confinement fed a cactus forage-based diet.

Influence of level of supplemental whole flaxseed on forage intake and site and extent of digestion in beef heifers consuming native grass hay1,2

The objectives of this study were to evaluate the influence of supplemental whole flaxseed level on intake and site and extent of digestion in beef cattle consuming native grass hay. Nine Angus heifers (303 +/- 6.7 kg of BW) fitted with ruminal and duodenal cannulas were used in a triplicated 3 x 3 Latin square. Cattle were given ad libitum access to chopped native grass hay (9.6% CP and 77.5% NDF, OM basis). All animals were randomly allotted to 1 of 3 experimental treatments of hay plus no supplement (control); 0.91 kg/d whole flaxseed (23.0% CP, 36.3% NDF, and 25.5% total fatty acid, OM basis); or 1.82 kg/d whole flaxseed on a DM basis. Supplemental flaxseed tended to decrease (linear, P = 0.06) forage OM intake. However, total OM intake did not differ (P = 0.29) with increasing levels of flaxseed. Total duodenal OM flow increased (linear, P = 0.05) with additional flaxseed in the diet, and no differences (P = 0.29) were observed for microbial OM flow. True ruminal OM disappearance was not affected (P = 0.14) by supplemental flaxseed. Apparent lower tract OM digestibility increased (linear, P = 0.01) with level of whole flaxseed. Apparent total tract OM digestibility was not different (P = 0.41) among treatments. Nitrogen intake increased (linear, P < 0.001) with supplemental flaxseed. In addition, total duodenal N flow tended (P = 0.08) to increase with additional dietary flaxseed. However, true ruminal N digestibility did not differ (P = 0.11) across treatment. Supplemental whole flaxseed did not influence ruminal (P = 0.13) or total tract (P = 0.23) NDF digestibility. Ruminal molar proportion of propionate responded quadratically (P < 0.001) with increasing levels of whole flaxseed. An increase in the duodenal supply of 18:3n-3 (P < 0.001), total unsaturated fatty acids (P < 0.001), and total fatty acids (P < 0.001) was observed with additional dietary whole flaxseed. Apparent postruminal 18:3n-3 disappearance tended to decrease (P = 0.07) as intake of flaxseed increased. Overall, the inclusion of 1.82 kg/d of flaxseed does not appear to negatively influence nutrient digestibility of a forage-based diet and therefore can be used as an effective supplement to increase intestinal supply of key fatty acids important to human health.

Comparison of alternative beef production systems based on forage finishing or grain-forage diets with or without growth promotants: 2. Meat quality, fatty acid composition, and overall palatability

Five beef cattle management regimens were evaluated for their effect on meat quality, fatty acid composition, and overall palatability of the longis-simus dorsi (LD) muscle in Angus cross steers. A 98-d growing phase was conducted using grass silage with or without supplementation of growth promotants (Revalor G and Rumensin) or soybean meal. Dietary treatments in the finishing phase were developed with or without supplementation of growth promotants based on exclusive feeding of forages with no grain supplementation, or the feeding of grain:forage (70:30) diets. Growth promotants increased (P < 0.01) shear force and tended (P = 0.06) to increase toughness of the LD muscle due to limited postmortem proteolytic activity (lower myofibrillar fragmentation index value; P = 0.02). Grain feeding increased DM and intramuscular fat content (P = 0.03 and P = 0.05, respectively) in the LD but decreased the sensory panel tenderness score (P = 0.01). Growth promotants increased (P </= 0.05) the proportion of C18:0, C20:0, trans isomers of C18:1, and cis-9, trans-11 C18:2. Exclusive feeding of forages increased the proportion of cis-9, cis-12, cis-15 C18:3 as well as several other isomers of the n-3 family and decreased in the ratio of n-6 to n-3 fatty acids in the LD muscle as compared with supplementing grain (P < 0.05). In addition, the forage-based diet increased (P < 0.01) the concentration in the intramuscular fat of several intermediates (cis-9, trans-11, cis-15 C18:3; trans-11, cis-15 C18:2; trans-11 C18:1) of ruminal biohydrogenation. Forage feeding also increased the proportion of cis-9, trans-11 C18:2 (P < 0.01) and decreased the concentration of trans-10 C18:1 in the LD muscle (P = 0.03). It is concluded that quality demands of health-conscious consumers can be met through a forage-finishing and growth promotants-free beef production system.

Magnesium Absorption by Lactating Dairy Cows on a Grass Silage-Based Diet Supplied with Different Potassium and Magnesium Levels

The objective of the present study was to investigate the interactions of dietary K intake typical for forage-based diets on Mg balance in lactating dairy cows. Six lactating multiparous cows of the Swedish Red and White breed in midlactation were used. Two concentrations of Mg (1.9 and 4.3 g/kg of dry matter) and 3 concentrations of K (19, 28, and 37g of K/kg of dry matter) were obtained by adding appropriate amounts of MgO and KHCO3 to the diet. The experimental setup was a 6×6 Latin square design with a 2×3 factorial arrangement of treatments. Each experimental period lasted 14 d (9-d treatment adaptation period and 5-d data collection). There was no effect of Mg or K dietary supplementation on milk yield. Supplementing the ration with K did not significantly affect the Mg apparent absorption, urinary Mg excretion, or plasma Mg concentration. The Mg balance, estimated as the Mg losses in milk and urine, was positively related to Mg intake but not affected by K intake. The amount of apparently digested Mg was related to the Mg balance. The apparent digestibility ranged from 0.12 to 0.24 with no effect of mineral supplementation. There was a significant curvilinear relationship between plasma Mg and urinary Mg excretion, with a more marked increase in urinary Mg excretion at higher plasma levels of Mg.

A decade of developments in the area of fat supplementation research with beef cattle and sheep1

Supplementing ruminant animal diets with fat has been investigated as a means to influence a variety of physiological processes or to alter fatty acid composition of food products derived from ruminant animals. Several digestion experiments have been conducted with beef cattle and sheep to elucidate the effects of supplemental fat on utilization of other dietary components. Negative associative effects are not likely to be observed in ruminants consuming forage-based diets with supplemental fat at < or = 2% of DMI. Inclusion of supplemental fat at < or = 3% of DM is recommended to obtain the most benefit from the energy contained within the fat and other dietary components in high-forage diets. For ruminants fed high-concentrate diets, supplementing fat at 6% of diet DM is expected to have minimal impacts on utilization of other dietary components. Although there is greater potential to supply the ruminant animal with unsaturated fatty acids from dietary origin if fat is added to high-concentrate diets, incomplete ruminal biohydrogenation of C18 unsaturated fatty acids results in an increase in duodenal flow of 18:1 trans fatty acids regardless of basal diet consumed by the animal. The biohydrogenation intermediate 18:1 trans-11 (trans-vaccenic acid) is the likely precursor to cis-9, trans-11 CLA because the magnitude of increase in CLA content in tissues or milk of ruminants fed fat is much greater than the increase in CLA presented to the small intestine of ruminants fed fat supplements. Duodenal flow of trans-vaccenic acid is also substantially greater than CLA. Increasing unsaturated fatty acids status of ruminants imparts physiological responses that are separate than the energy value of supplemental fat. Manipulating maternal diet to improve unsaturated fatty acid status of the neonate has practical benefits for animals experiencing stress due to exposure to cold environments or conditions which mount an immune response. Supplementing fat to provide an additional 16 to 18 g/d of 18:2n-6 to the small intestine of beef cows for the first 60 to 90 d of lactation will have negative impacts on reproduction and may impair immune function of the suckling calf. Consequences of the suckling animal increasing its intake of unsaturated fatty acids because of manipulation of maternal diet warrants further investigation.