Silage Intake Research Articles

Effect of hybrid, maturity, and mechanical processing of corn silage on intake and digestibility by beef cattle.

A study involving a 2 x 2 x 2 factorial arrangement of treatments was conducted to evaluate effects of hybrid (Pioneer 3335 and 3489), maturity (half milkline and blacklayer), and mechanical processing (field chopper with and without on-board rollers engaged) on intake and digestibility of corn silage. Forty Angus steers (322 +/- 5.2 kg BW) were assigned to the eight silage treatments (five steers per treatment) and individually fed using electronic gates. Diets consisted of 60% corn silage and 40% chopped alfalfa hay (DM basis). Following a 5-d adaptation period, intake was measured for 7 d and subsequently fecal samples were collected for 5 d. Chromic oxide (5 g/d) was fed beginning 7 d before fecal sample collection and digestibility was determined by the ratio of Cr in the feed and feces. Steers were reallocated to treatments and these procedures were repeated, providing 10 observations per treatment. In addition, all silages were ruminally incubated in six mature cows for 0, 8, 16, 24, 48, and 96 h to determine extent and rate of DM, starch, NDF, and ADF disappearance. Processing increased DMI of hybrid 3489 but did not affect DMI of hybrid 3335 (hybrid x processing; P < 0.06). Total tract digestibility of DM, starch, NDF, and ADF decreased (P < 0.01) as plant maturity increased. Maturity tended to decrease starch digestibility more for hybrid 3489 than for hybrid 3335 (hybrid x maturity; P < 0.10). Processing increased (P < 0.01) starch digestibility but decreased (P < 0.01) NDF and ADF digestibility, resulting in no processing effect on DM digestibility. There was a numerical trend for processing to increase starch digestibility more for latethan for early-maturity corn silage (maturity x processing; P = 0.11). Processing increased in situ rates of DM and starch disappearance and maturity decreased in situ disappearance rates of starch and fiber. These data indicate that hybrid, maturity, and processing all affect corn silage digestibility. Mechanical processing of corn silage increased starch digestibility, which may have been associated with the observed decreased fiber digestibility.

Evaluation of legume silages offered to Holstein-Friesian cows with small amounts of concentrates

The high intake characteristics of red clover silage has been recognised for many years (e.g. Thomaset al., 1985). Our previous study (Dewhurstet al., 2000) demonstrated the considerable intake and milk production potential of clover silages made using a new approach based on preparation of big-bales from wilted material with the use of biological inoculant additives. The objective of this study was to verify the positive results obtained with red and white clover silages using material taken from a further series of cuts taken in a subsequent year and to evaluate the legume silages with low levels of concentrate feeding.

The development of a system based on near infrared spectroscopy to predict the intake of grass silage as the sole feed by the dairy cow

Grass silage remains the major forage component of winter dairy rations, yet its intake characteristics are particularly variable. Major research projects at SAC and ARINI over the past few years have produced two large datasets on ad libitum intake of grass silage and shown that improved silage characterisation methods (NIRS and electrometric titration) can substantially improve the accuracy of prediction of silage intake as the sole forage (Offer et al., 1994; Steen et al., 1995). The objective of this research programme was to integrate these two datasets to provide a common prediction system which would be appropriate for adoption across the United Kingdom

Feeding behaviour, food intake and milk production responses of lactating dairy cows to diets based on grass silage of high or low dry-matter content, supplemented with quickly and slowly fermentable energy sources

AbstractTwelve dairy cows in early lactation were offered low (L; 215 g/kg) or high (H; 449 g/kg) dry matter(DM) content silages, prepared using material from the same sward. In addition, all animals received 9 kg/day, of supplements based on barley (B), sugar-beet pulp (SB) or a 50: 50 mixture of the two (B: SB), in two equal portions at 07:30 and 14:30 h. The six treatments were offered in an incomplete Latin square design. Mean intakes of H (14·4 kg DM per day) were significantly higher than intakes observed for L (10·0 kg DM per day) (P &lt; 0·001). Within silage type, highest intakes were observed for cows receiving the SB supplement (P &lt; 0·01). Higher intakes of H were reflected in higher total milk yield (P &lt; 0·05) as well as fat (P &lt; 0·05) and protein (P &lt; 0·01) yield. Milk protein concentration was greater for animals receiving silage H (P &lt; 0·001), with lower values being observed for animals consuming SB (P &lt; 0·05), within silage type. Time spent eating, duration and number of meals were similar for either silage and the higher intakes of H silage reflected greater intake rates (g DM per min) (P &lt; 0·001) resulting in larger meal sizes (P &lt; 0·001). All chewing indices (time spent eating silage, ruminating and total time chewing per kg DM ingested) were greater for the L silage (P &lt; 0·001). It is concluded that the benefits in forage intake with higher DM grass silages, for high yielding dairy cows, are associated with consequential benefits in milk yield and milk protein content. The most likely explanation for the greater intakes is a faster particle breakdown in the rumen allowing larger meal sizes before animals became constrained. The higher intakes of silage when animals consumed the SB supplement may be due to a slower rate of fermentation of the supplement, which was more closely matched to that of silage. Although not significant there was a tendency for differences in silage intake between animals receiving B compared with SB supplements to be greater for animals receiving the H silage suggesting that supplementation strategies to ensure optimal forage utilization may differ for silages of differing DM content.

The potential of forage–maize intercrops in ruminant nutrition

Studies at the University of Reading (UK) compared silage quality, feed intake and digestibility of maize silage with maize–sunflower (MS), maize–kale (MK) and maize–runner bean (MRB) silage, when sunflowers, kale and runner beans represented 26, 7 and 16% of total silage dry matter (DM). All intercrop silages had higher crude protein values (MS, 137 g kg −1, MRB, 120 g kg −1, MK, 105 g kg −1) than maize (81 g kg −1). The neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents were higher and the neutral cellulase gamminase digestibility (NCGD) values lower for MRB and MS compared with maize and MS silage. All silages fermented well with pH ranging from 3.9 to 4.2 and ammonia-N content of less than 100 g kg −1 total nitrogen (TN). An in vivo digestibility study with sheep showed no significant difference in voluntary feed intake between the four silages, with the highest and lowest values of 68 and 62 g DM (kg BW 0.75) −1 per day being recorded for MK and MS silage. The highest and lowest values for in vivo DM digestibility (DMD) and organic matter digestibility (OMD) were recorded for MK and MS silages, with intermediate values for maize and MRB silage. The inclusion of all three intercrops significantly increased nitrogen digestibility when compared with maize silage. The metabolisable energy values for maize and MK silage were both substantially higher than those recorded for MRB and MS silage.

Relationship between dry matter, fibre and nitrogen degradation characteristics of silage and silage intake of steers

AbstractA study was carried out to examine the relationship between silage intake and rumen degradability characteristics of silage. The dry matter (DM), neutral-detergent fibre (NDF), acid-detergent fibre (ADF), hemicellulose and nitrogen (N) degradability characteristics of 136 silages were determined using polyester bags in three rumen fistulated beef cross steers. The bags were incubated for 0, 6, 12, 24, 48 and 72 h. Intakes of these silages, by steers, were reported by Steen et al., 1998. The relationships between silage DM intake (g/kg metabolic live weight) and DM, fibre and N degradability characteristics of the silages were poor (R2 &lt; 0·32). Degradability characteristics of the silages were highly negatively correlated with fibre concentration of the silages (R &lt; –0·82) and highly positively correlated with the soluble N minus ammonia concentration (R &lt; 0·77). Some of the degradability characteristics were highly correlated with organic matter digestibility, particularly the proportion of DM, fibre and N degraded after 72 h (R = 0·75 to 0·85). In view of the poor relationship between silage intake and degradability, the results of this study question the rôle of degradation characteristics of DM, fibre and N in the rumen on silage intake.

The effect of a silage additive and level of concentrate supplementation on silage intake, animal performance and carcass characteristics of finishing beef cattle

An experiment was carried out to examine silage fermentation, effluent production and aerobic stability in unwilted grass silage, which was either ensiled without additive or with a commercially available blend of ammonium hexamethanoate, ammonium hexapropionate and octanoic acid (6 l t−1, Maxgrass, BP Chemicals Ltd., Northwich, UK) and to determine alternative approaches to obtaining the same performance in finishing beef cattle. Seventy-two Limousin × Friesian and Charolais × Friesian steers (mean initial live weight 424 kg s.d. 28·3) were blocked into groups of nine according to live weight and previous performance and offered silage, either with or without the additive, and supplemented with 0, 1·5, 3·0 or 4·5 kg d−1 of a concentrate with a crude protein content of 150 g kg−1 DM or allocated to a pre-experimental slaughter group to enable calculation of daily carcass gain. Daily silage intakes were recorded for 112 days. At the end of the experiment, all cattle were slaughtered and daily carcass gain, omental, mesenteric, perinephric and retroperitoneal fat depots [kidney-knob and channel fat (KKCF)], fatness, conformation, subcutaneous fat depth over M. longissimus dorsi muscle and carcass fat, protein and bone contents were assessed. Across all levels of supplementation, cattle offered the silage with the additive showed significantly (P < 0·001) higher daily DM intakes than those offered the silage without additive. Cattle offered the silage with the additive but unsupplemented had significantly (P < 0·001) higher daily carcass gains than those offered the silage without additive and unsupplemented. The response in carcass gain was 76 and 35 g kg−1 additional concentrate for the silages with and without the additive respectively.

Prediction of silage feeding value from the analysis of the herbage at ensiling and effects of nitrogen fertilizer, date of harvest and additive treatment on grass silage composition

The prediction of silage feeding value from the analysis of herbage at ensiling and the effects of rate of nitrogen (N) fertilizer, date of harvest and treatment additive at ensiling on fermentation, dry matter (DM) recovery and effluent production were evaluated in a factorial experiment. Herbage was harvested from 75 plots, laid out in three replicate blocks of 25, from the primary growth of a predominantly perennial ryegrass sward. The plots received 72, 96, 120, 144 or 168 kg N/ha and were harvested on 10, 17, 24 or 31 May or 7 June. Herbage was ensiled for 176 days in laboratory silos (6 kg capacity), either untreated or treated with formic acid or a bacterial inoculant, each applied at 3 ml/kg herbage. Increasing the rate of N fertilizer and delaying harvest date increased herbage DM yield but decreased silage digestible organic matter digestibility (D-value) and intake potential (P &lt; 0·001).Increasing the rate of N fertilizer increased crude protein (CP), acid insoluble N (AIN) (P &lt; 0·001), acid detergent fibre (ADF) (P &lt; 0·01) and acid detergent lignin (ADL) concentrations but had no statistically significant effect (P &gt; 0·05) on pH or the concentrations of ammonia N, lactic or volatile fatty acids. Delaying harvesting date decreased CP, AIN and ADF concentrations (P &lt; 0·001) and effluent DM losses (P &lt; 0·001). Treatment with either formic acid or inoculant decreased silage pH and the concentrations of ammonia N, acetic acid and propanol and increased AIN, ethanol, neutral detergent fibre (NDF), ADF and cellulose concentrations, effluent volume, DM losses and intake potential. Formic acid treatment decreased D-value (P &lt; 0·001), whereas inoculant treatment was not statistically significant (P &gt; 0·05). For potential silage and metabolizable energy (ME) intakes and D- value, strong positive correlations (P &lt; 0·001) were identified with herbage pH, buffering capacity and concentrations of CP, AIN, true protein nitrogen (TP), while negative correlations (P &lt; 0·001) were identified with herbage yield and concentrations of NDF and hemicellulose. With untreated silages, strong positive correlations (P &lt; 0·001) were identified between silage pH and herbage pH and concentrations of AIN, buffering capacity, ash, TP and negative correlations (P &lt; 0·001) were identified with herbage DM yield and concentrations of DM and WSC. Herbage yield and concentrations of NDF, TP, DM and nitrate N provided the best linear relationship for predicting potential ME intake of the resultant untreated silages (R2 = 0·94). It is concluded that delaying harvest date had the most detrimental effect on silage feeding value, although this effect was partially overcome by reducing the rate of fertilizer N and use of either an inoculant or formic acid additive. Silage feed value was also highly correlated with the protein and fibre fractions, ash, buffering capacity and pH of the herbage at ensiling.

Choices by lactating cows between concentrates high or low in digestible undegraded protein

AbstractTo determine whether lactating cows select a nutritionally appropriate diet when given grass silagead libitumand a choice of concentrates high or low in digestible undegradable protein (DUP), 24 mid-lactation Holstein-Friesian cows were given, in different 3-week periods, a concentrate high in DUP (HP), one low in DUP (LP), or a choice between the two (CHOICE), all at an allowance of 5·4 kg dry matter per day. Milk yield was significantly lower, and silage intake slightly but significantly higher, on LP than on either HP or CHOICE. The mean proportion of HP taken in the CHOICE period was 0·47 which was greater than the proportion required to satisfy the cows’ calculated requirements for effective rumen degradable protein, DUP or metabolizable protein but not significantly different from the ratio of 0·50 expected if no choice was made. Individual cows had a strong tendency initially to continue to eat from the feeder from which they had obtained concentrates in the period before CHOICE but this changed to eating significant amounts of both foods within about a week. The fact that the relationship between the proportion of HP in the concentrate intake and milk protein output was significant and positive, and became more so as the CHOICE period progressed, supports the hypothesis that protein demand was directing diet selection but must be viewed with caution as it was heavily influenced by the results of one animal: the highest-yielding cow which also chose to eat the greatest proportion of HP.

Effects of supplementation of dairy cattle with fish oil on silage intake, milk yield and milk composition.

The effects of level of fish oil inclusion in the diet on grass silage intake, and milk yield and composition of dairy cows offered either 5 or 10 kg concentrates/d were evaluated in a ten treatment, partly balanced, changeover design experiment involving 50 cows in early lactation. Concentrates were prepared to provide 0, 150, 300 or 450 g fish oil/cow per d or 300 g fish oil/cow per d from a premix when each animal was offered 5 kg/d. The fish oil was predominantly from herring and mackerel caught in the North Atlantic while the fish oil premix was obtained from a commercial source and used palm kernel expeller as a carrier. Increasing fish oil supplementation decreased silage dry matter intake and the concentrations of milk fat and protein, and increased milk yield and diet digestibility. There were significant interactions between concentrate feed level and level of fish oil for silage intake and milk yield. Other than for the concentrations of milk fat and protein, and 20:4n-6 fatty acids, the source of fish oil did not affect forage intake or animal performance. Fish oil supplementation also decreased the concentrations of milk protein by 0.9 g/kg for each 100 g increase in fish oil supplementation, the depression being similar at each level of concentrate feeding. Supplementing the feed of dairy cows with 450 g fish oil/cow per d decreased the concentration of milk fat by 15 g/kg. This study also showed that feeding dairy cattle with fish oil is an efficient method of increasing eicosapentaenoic acid in the human diet through transfer into milk.

Factors influencing the response in intake of silage and animal performance after wilting of grass before ensiling: a review

This review examines the response in intake of silage and animal performance after wilting of grass before ensiling. It uses data from eighty‐five published comparisons. Initial analysis identified those variables having the greatest influence on the increase in dry‐matter (DM) intake of grass silage owing to wilting. Total water loss, drying rate of the wilted material and ammonia‐N concentration of the unwilted material were the variables most closely and positively correlated to the proportional increase in DM intake as a result of wilting, with r2 values of 0·344, 0·393 and 0·240 respectively. There was little evidence of curvilinearity in any of the relationships. Stepwise regression analysis was used to identify the best multiple linear regressions for predicting the proportional increase in intake owing to wilting. Factors associated with the extent and rate of water loss in the field (total water loss and drying rate) and the quality of the unwilted material ensiled and its subsequent fermentation pattern (DM digestibility, crude protein, ammonia‐N content of unwilted silage) were the key variables in the relationship. Subsequent analysis related the increase in output of milk energy of dairy cows and liveweight gain of beef cattle to the same independent variables. This indicated that variables shown to describe the response in DM intake in the previous analysis were among those most closely related to the increases in animal performance owing to wilting of grass. To assess whether the increase in animal performance owing to wilting could be explained as a direct response to increased metabolizable energy (ME) intake of wilted compared with unwilted silages, linear relationships were derived between the increase in milk and beef production parameters and the increase in ME intake owing to wilting. From these, it was concluded that there was no clear evidence that wilting reduced the efficiency of utilization of ME in beef or dairy cattle. The present study showed that the increase in milk energy output (measured in MJ) per increase in ME intake (measured in MJ) owing to wilting was linear, with a slope of 0·19. This response from additional ME intake owing to wilting is in line with what would be anticipated when increasing ME intake by other methods.

Effect of intensity of maceration on digestibility and intake of alfalfa hay and silage fed to sheep

A study was conducted to determine the influence of intensity of mechanical conditioning on the nutritive value of alfalfa conserved as hay or silage. Fresh alfalfa was mowed and conditioned at three levels of maceration prior to field wilting during 45 h for silage (29–39% DM) or 94 h for hay (87% DM, after barn-curing), under light rain conditions during the first 2 d. The conditioning treatments were: control (conventional mowing-conditioning), light maceration (one passage through three knurled steel rolls), medium maceration (two passages), and intense maceration (three passages). Concentrations of NDF, ADF, hemicellulose, CP-NDF, and CP-ADF increased linearly (P &lt; 0.001) with the level of maceration. Silage pH, acetic acid, propionic acid, and butyric acid increased, while lactic acid decreased (P &lt; 0.001), with the level of maceration. The effective rumen degradabilities of DM, CP, and NDF, measured with fistulated cows, were not affected (P &gt; 0.10) by the level of mechanical conditioning. Forty-eight male sheep (46.8 ± 6.7 kg BW) were fed a 100% forage diet according to a completely randomized design with a 2 × 4 factorial arrangement of treatments (two storage methods and four levels of conditioning). Under restricted feeding, DM, NDF, ADF, and hemicellulose digestibilities decreased linearly (P &lt; 0.001) with the level of maceration. However, the digestibility of CP-NDF increased with the level of maceration; the effect was more important in hay than in silage (P &lt; 0.001 for the interaction). When silages were fed ad libitum to 24 sheep, daily DMI was 2.31, 2.88, 2.76, and 2.41% of BW and DM digestibility was 60.8, 60.1, 56.2, and 46.7%, for control, light, medium, and intense maceration, respectively (P &lt; 0.01). The results suggest that light maceration increases DM intake while maintaining digestibility of forages fed to sheep. Because of humid conditions and potential soil contamination due to multiple windrow pickup, intense maceration caused severe nutrient loss, which might be avoided under dry field wilting and good storage conditions. Key words: Alfalfa, hay, silage, digestion, degradability, intake

Intake, digestibility, and composition of orchardgrass and alfalfa silages treated with cellulase, inoculant, and formic acid fed to lambs.

The objectives of this study were to determine the effect of a cellulase (from Trichoderma longibrachiatum) alone or combined with a bacterial inoculant (Lactobacillus plantarum and Pediococcus cerevisiae) or formic acid on composition, intake, and digestibility of orchardgrass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.) silages. Orchardgrass and alfalfa were harvested at the early heading stage and at the early bloom stage of maturity and wilted to approximately 22 and 32% DM, respectively. Forages were then ensiled in 100-L sealed barrels for at least 60 d before they were fed to lambs. Silage treated with cellulase had lower (P < .001) pH and lower (P < .001) acetic acid and NH3 N concentrations than untreated silage of both plant species and a higher (P = .004) lactic acid concentration than the control treatment of alfalfa silage. Fermentation characteristics of cellulase-treated silages, especially of alfalfa, were further enhanced by use of inoculant. Formic acid addition increased (P < .001), reducing sugar concentration of cellulase-treated orchardgrass and alfalfa silage by 90 and 154%, respectively, and decreased (P < .001) NH3 N concentration of cellulase-treated alfalfa silage by 19%. Averaged across plant species, cellulase, combined with inoculant or formic acid, resulted in 8 and 13% greater (P = .03) DMI, respectively, than the control silage. Extensive enzymatic cell-wall degradation during ensiling decreased (P = .003) NDF intake of cellulase-treated orchardgrass silage by 25% and decreased (P = .001) cellulose intake by 23%, when averaged across plant species. Addition of formic acid increased (P = .003) NDF intake of cellulase-treated orchardgrass silage by 19%. Averaged across species, cellulase application decreased (P < .05) silage NDF digestibility by 18%. Greater sugar and lower acetic acid, NH3 N, and NDF concentrations resulted in greater DMI of cellulase-treated silage than of control silage, when cellulase was combined with formic acid or inoculant.

The effect of slurry application timing on grass silage fermentation and intake by dairy cattle

Many farmers apply slurry to grassland as a fertiliser or a means of waste disposal. There is evidence that winter slurry application leads to higher losses of nitrogen due to leaching subsequently reducing the efficiency of slurry N utilisation when compared with spring applications (Smith et al 1995). This suggests that slurry applications should be undertaken in spring, but the effect of timing on the extent of grass contamination is unknown. When grassland is used for silage production, contamination of the sward can lead to reduced silage fermentation and acceptability (Boxem and Remmelink 1987). A study was conducted to investigate the effect of timing of slurry application on fermentation and dry matter intake of first and second cut grass silage.

Intake and apparent digestibility of hay, haylage, big bale and clamp silage by ponies

Grass hay is the traditional conserved fodder fed to horses in the UK, yet good quality hay is often scarce and expensive. Working or breeding equines often require a higher plane of nutrition than that provided by hay, yet feeding high levels of concentrates can lead to a number of metabolic disorders such as colic and laminitis. Furthermore, the high dust content of hay can elicit the onset of the debilitating disorder, chronic obstructive pulmonary disease. Thus, there is increasing interest in feeding horses forage-based diets which are both low in dust and have enhanced nutritive values. The aim of this experiment was to determine the intakes and digestibility of four types of conserved forage by ponies.

The effects of concentrate energy source on milk composition of lactating dairy cattle offered grass silage

AbstractTwo partially balanced change-over design experiments were undertaken to examine the effects of concentrate energy source on milk yield and composition of lactating diary cows offered a diverse range of grass silages. A total of nine silages differing in fermentation digestibility and intake characteristics were produced in experiments 1 and 2. Silage dry matter (DM) concentration ranged from 170 to 473 g/kg, ammonia nitrogen ranged from 58 to 356 g/kg nitrogen, digestible organic matter in the DM ranged from 551 to 724 g/kg and silage DM intake potential ranged from 57 to 103.8 g/kg w0.75 respectively. In experiment 1, 5 concentrates were formulated to contain similar concentrations of crude protein (CP), effective rumen degradable protein (ERDP), metabolizable energy (ME) and digestible undegradable protein (DUP) while three concentrates were formulated in experiment 2 to contain similar concentrations of CP, ME and DUP. The concentrates were prepared using barley, wheat, sugar beet pulp and citrus pulp as energy sources and formulated to achieve a wide range of starch concentrations. Starch concentrations ranged from 50 to 384 g/kg DM and 22 to 273 g/kg DM in experiments 1 and 2 respectively. There were no concentrate energy source by silage type interactions for silage intake, milk yield and composition. It is concluded that increasing starch intake resulted in positive and negative linear relationships for milk protein (P&lt;0.001, R2 = 0.96) and fat (P&lt;0.001, R2 = 0.85) concentrations respectively. Concentrate energy source had no effect on silage DM intake or milk yield.

Response of Dairy Cows Fed Grass Silage Diets to Abomasal Infusions of Histidine Alone or in Combinations with Methionine and Lysine

The response of dairy cows fed grass silage-based diets to the abomasal infusion of water (control) or 6.5g of His alone or in combination with either 6.0g of Met or 19.0g of Lys or both was studied in an incomplete 4 x 5 Latin square experiment with 14-d periods. Each cow received a basal diet of 8 kg/d of cereal concentrate [12.1% crude protein (CP)] and free access to grass silage (14.1% CP) ensiled with an acid-based additive. Postruminal infusions increased arterial plasma concentrations of the amino acids (AA) infused, but compared with control, only the infusion of His (18 vs. 57 µmol/L) was associated with significant increases in milk and milk protein yields. Infusions of His did not affect dry matter intake of grass silage, rumen fermentation, or diet digestibility. Milk protein content was unchanged by treatments, but His infusions decreased lactose and fat contents. The combinations of AA did not produce any further responses compared with His alone. However, milk protein percentage was slightly higher, and milk fat percentage tended to be higher when Met rather than Lys was infused with His. We concluded that His is the first-limiting AA when grass silage-based diets are supplemented with cereal concentrates, while neither Met nor Lys are the second-limiting AA with grass silage feeding.

Effects of maturity of silage and protein content of concentrates on milk production of ewes rearing twin or triplet lambs

Fifty-one Outaouais Arcott ewes were used to study the effects of silage maturity, protein level and number of lambs suckled on milk production and lamb growth in a 2 × 2 × 2 factorial design experiment. Ewes were given ad libitum access to either an early-bloom (EB) or full-bloom (FB) bromegrass silage supplemented with 725 g d−1 of a 15 or 21% CP concentrate. Number of lambs suckled were two or three per ewe. During the 6 wk of lactation, ewes receiving the EB silages consumed more DM (2.07 vs. 1.74 kg d−1, P &lt; 0.01), and gained more (1.3 and −2.7 kg, P &lt; 0.05) than ewes fed FB. Ewes that raised three lambs had greater silage intake (2.00 vs 1.86 kg d−1) and lost more weight during lactation (−2.8 vs. +0.3 kg) than those suckling twins. Milk yields of ewes offered the EB and FB silages were 2.42 and 2.28 kg d−1, respectively (P &lt; 0.05), for the first 4 wk of lactation. Ewes that raised three lambs produced less milk (2.25 vs. 2.43 kg d−1) than those nursing twins (P &lt; 0.05). Milk fat content (8.2%) was not influenced by treatments, whereas milk protein content was higher (P &lt; 0.05) from ewes receiving the EB silage compared with the FB silage (5.05 vs. 4.76%). At 4 and 6 wk of age, twin lambs were 2.6 kg (9.5 vs. 6.9 kg) and 3.5 kg (12.0 vs. 8.5 kg) heavier (P &lt; 0.01) than triplet lambs for EB and FB silages, respectively. However, at the end of the 6-wk period, ewes nursing triplets weaned 1.3 kg more lambs than did ewes nursing twins (P &lt; 0.05). Lambs from ewes that received the EB silage were 1.1 kg heavier at 6 wk (P &lt; 0.05) than those from ewes fed with the FB silage. Also, lambs from ewes receiving the 21% CP concentrate were 1.1 kg heavier at 6 wk (P &lt; 0.05) than the lambs from ewes fed the 15% CP. Litters were heavier at 6 wk with 21% CP concentrate compared with 15% (25.1 vs. 24.1 kg, P &lt; 0.05), and triplet litters were heavier (P &lt; 0.01) than twin with the EB silage. Within litter weight variation (weight difference between the biggest and the smallest lambs in a litter) proved to be greater (P &lt; 0.05) with triplets (4.2 kg) than twins (2.2 kg). In conclusion, providing a higher quality silage (lower ADF and higher CP contents) improved ewe feed intake, milk production, lamb growth and litter weight, while feeding a higher protein concentrate only improved lamb growth with the lower quality silage. Key words: Ewe, lamb, growth, milk production, silage, protein, triplet

Short Communication: The Effect of Duodenal Ammonia Infusions on Milk Production and Nitrogen Balance of the Dairy Cow

We hypothesized that an increased uptake of ammonia from the gut of dairy cows would increase the use of amino acids for urea synthesis and decrease the availability of amino acids for milk protein production, leading to a reduction in milk protein output. To test this hypothesis, four multiparous Holstein-Friesian dairy cows offered a constant diet based on grass silage were continuously infused with ammonium acetate (ammonia) or acetic acid (control) into the duodenum for 5 d in each period of a changeover design experiment. Silage intake, rumen ammonia, pH and volatile fatty acid concentrations, and feces N excretion and whole body N balance were all unaffected by treatment, although urinary N excretion increased. Similarly, there was no effect of treatment on milk yields or on milk constituent yields. We concluded that ammonia absorption represents a loss of protein to the animal, but that it is unlikely to result in reduced amino acid availability for productive purposes such as lactation.

The effects of wilting grass before ensiling on silage intake

Herbage, predominantly perennial ryegrass (Lolium perenne) grown in Northern Ireland, was harvested at four dates from June to October 1996 (H1, H2, H3 and H4). At each harvest approximately one‐fifth of the grass harvested was artificially dried and pelleted (G). The remainder of the grass was either wilted for 28–52 h (W), depending on the weather conditions, or ensiled directly, i.e. unwilted (UW). Within the W and UW treatments an inoculant or formic acid additive was applied to the herbage before ensiling. After a minimum ensiling period of 10 weeks, sixty steers, mean initial live weight 432 (s.d. 37) kg, were offered the twenty forages in a four‐period partially balanced changeover design experiment. Each period was of 2 weeks’ duration. Dry‐matter (DM) intakes were recorded daily, with intakes in the second week of each period used in the statistical analysis of the data. The digestibility of each of the forages was also determined in vivo using four castrated male sheep per silage. Wilting increased the DM content of the silage and the pH, the largest increase in DM content occurring at the second harvest. On average, wilting proportionally increased silage DM intake by 0·21 compared with the unwilted silage (P &lt; 0·001), but the intake of the wilted silage was not significantly different from that of the artificially dried and pelleted grass (P &gt; 0·05). The intake of the wilted silage was higher than that of the unwilted silage at each harvest, the proportional increases being 0·22 (P &lt; 0·001), 0·41 (P &lt; 0·001), 0·19 (P &lt; 0·001) and 0·05 (P &gt; 0·05) at harvests H1, H2, H3 and H4 respectively. Treatment of the grass with formic acid before ensiling resulted in a proportional increase in silage intake of 0·08 compared with the inoculant‐treated silage (P &lt; 0·05). Compared with the inoculant‐treated silage, formic acid increased silage intake by 0·08, 0·02, 0·14 and 0·10 at harvests H1 (P &gt; 0·05), H2 (P &gt; 0·05), H3 (P &lt; 0·01) and H4 (P &lt; 0·05). The results of this study indicate that the effect of wilting on silage intake varies across different harvests and additive treatments. The difference in response to wilting across different harvests is mainly a result of the prevailing weather conditions during wilting.