Effects of expander-treating a barley-based concentrate on ruminal fermentation, bacterial N synthesis, escape of dietary N, and performance of dairy cows

Three primiparous dairy cows in early lactation with cannulas in rumen, duodenum and ileum were used in a 3×3 Latin square design to study effects of expander treatment of a barley-based concentrate. The concentrate was either pelleted at 75–80°C or expander treated at 125–130°C prior to pelleting. The diets consisted of 6.7 kg DM of grass silage and 10 kg DM of (1) 100% pelleted, (2) 50% pelleted and 50% expanded or (3) 100% expanded concentrate. The diets were offered as a mixed ration in four equal meals daily. Ruminal fermentation, bacterial N synthesis, duodenal, ileal and faecal flow of nutrients, and animal performance were monitored. Expander treatment numerically increased ruminal digestion of starch, which explained the observed increase in ruminal VFA concentration and the lowered ruminal pH (P<0.05). The proportion of butyrate in rumen liquid increased, whereas the proportion of propionate decreased in the expanded compared to the pelleted treatment (P<0.05). Expander treatment tended to increase rumen volume and rumen NDF pool size. Ruminal digestion of NDF was numerically lower in the expanded than in the pelleted treatment. No differences in bacterial N synthesis or efficiency of synthesis were observed among treatments. Expander treatment numerically increased the duodenal flow of non-ammonia N (NAN) and amino acid N (AAN), and seemed to increase the flow of non-ammonia non-bacterial N (NANBN) to the duodenum to a similar extent as was indicated by nylon bag studies. Milk production and milk fat and protein content were increased by the expander treatment (P<0.05), indicating that expander treatment increased the supply of nutrients for milk production.     

Effects of replacing grass silage with either maize or whole-crop wheat silages on the performance and meat quality of beef cattle offered two levels of concentrates

A randomised design involving 66 continental cross beef steers (initial live weight 523 kg) was undertaken to evaluate the effects of the inclusion of maize or whole-crop wheat silages in grass silage-based diets on animal performance, carcass composition, and meat quality of beef cattle. Grass silage was offered either as the sole forage or in addition to either maize or whole-crop wheat silages at a ratio of 40:60, on a dry matter (DM) basis, alternative forage: grass silage. For the grass, maize, and whole-crop wheat silages, DM concentrations were 192, 276, and 319 g/kg, ammonia-nitrogen concentrations were 110, 90, and 150 g/kg nitrogen, starch concentrations were not determined, 225, and 209 g/kg DM and in vivo DM digestibilities were 0.69, 0.69, and 0.58; respectively. The forages were offered ad libitum following mixing in a paddle type complete diet mixer wagon once per day, supplemented with either 3 or 5 kg concentrates per steer per day, in two equal feeds, for 92 days. For the grass, grass plus maize and grass plus whole-crop wheat silage-based diets food intakes were 8.38, 9.08, and 9.14 kg DM per day, estimated carcass gains were 514, 602, and 496 g/day and carcass weights were 326, 334, and 325 kg; respectively. Altering the silage component of the diet did not influence carcass composition or meat eating quality. Increasing concentrate feed level tended ( P = 0.09) to increase estimated carcass fat concentration and increased sarcomere length ( P < 0.05), and lean a* ( P < 0.01), b* ( P < 0.05), and chroma ( P < 0.01). There were no significant silage type by concentrate feed level interactions for food intake, steer performance, carcass characteristics or meat eating quality. It is concluded that replacing grass silage with maize silage increased carcass gain, and weight due to higher intakes, and improved utilisation of metabolisable energy. Whilst replacing grass silage with whole-crop wheat silage increased live-weight gain, the reduced dressing proportion resulted in no beneficial effect on carcass gain, probably due to increased food intakes of lower digestible forage increasing gut fill. Meat quality or carcass composition were not altered by the inclusion of maize or whole-crop silages in grass silage based diets.     

Effects of mixtures of red clover and maize silages on the partitioning of dietary nitrogen between milk and urine by dairy cows

Eight multiparous lactating Holstein-Friesian cows were used to evaluate the partitioning of dietary nitrogen (N) from diets based on mixtures of red clover and maize silages in comparison with diets based on ryegrass silage. All cows received 4 kg/day of a standard dairy concentrate with one of four forage treatments in an incomplete changeover design with three 4-week periods. Three treatments were based on mixtures of red clover and maize silage. N intake was altered both by varying the ratio of these silages (40/60 and 25/75 on a dry matter (DM) basis) and by an additional treatment for which the DM intake of the 40/60 mixture was restricted to the level achieved with grass silage. Rumen passage rates were estimated from faecal excretion curves following a pulse oral dose of Dysprosium-labeled silage and urinary excretion of purine derivatives (PD) was used as an index of rumen microbial protein synthesis. Red clover silage mixtures led to significantly increased feed intake (21.5, 20.7 and 15.2 kg DM/day for 40/60 and 25/75 red clover/maize silage mixtures and grass silage, respectively), milk production (25.8, 27.8 and 20.0 kg/day for the same treatments, respectively) and milk component yields, but were without effect on milk fat and protein concentrations. The large increase in the yield of milk (24.5 kg/day) and milk components for the restricted red clover/maize silage treatment, in comparison with the grass silage treatment, was proportionately greater than the increase in DM intake (16.6 kg DM/day). There were no significant treatment effects on diet digestibility, while the higher intakes of red clover silage mixtures were associated with higher rumen passage rates (5.82%, 6.24% and 4.55%/h, respectively). There were significant effects of both N intake and forage source on the partitioning of dietary N between milk and urine. When dietary protein was diluted by the inclusion of maize silage, red clover silage led to increased milk N and reduced urinary N in comparison with grass silage. Improvements in N utilisation may be related to increased dietary starch and/or rumen passage rates leading to increased microbial protein synthesis for these treatments. Urinary excretion of PD was significantly higher for all diets based on mixtures of red clover and maize silages, in comparison with grass silage. Urinary N output was close to literature predictions based on N intake for the diet based on ryegrass silage, but 40 to 80 g/day (25% to 30%) less than predicted for the diets based on the mixtures of red clover and maize silages.     

Effects of replacing grass silage with maize silages differing in inclusion level and maturity on the performance,meat quality and concentrate-sparing effect of beef cattle

The effects of maturity of maize at harvest, level of inclusion and potential interactions on the performance, carcass composition, meat quality and potential concentrate-sparing effect when offered to finishing beef cattle were studied. Two maize silages were ensiled that had dry matter (DM) concentrations of 217 and 304 g/kg and starch concentrations of 55 and 258 g/kg DM, respectively. Grass silage was offered as the sole forage supplemented with either 4 or 8 kg concentrate/steer daily or in addition with one of the two maize silages at a ratio 0.5 : 0.5, on a DM basis, maize silage : grass silage supplemented with 4 kg concentrate daily. The two maize silages were also offered as the sole forage supplemented with 4 kg concentrate/steer daily. The forages were offered ad libitum. The six diets were offered to 72 steers (initial live weight 522 s.d. 23.5 kg) for 146 days. There were significant interactions (P < 0.05) between maize maturity and inclusion level for food intake, fibre digestibility and daily gain. For the grass silage supplemented with 4 or 8 kg concentrate, and the maize silages with DM concentrations of 217 and 304 g/kg offered as 0.5 or 1.0 of the forage component of the diet, total DM intakes were 8.3, 9.8, 8.9, 8.2, 9.2 and 9.8 kg DM/day (s.e. 0.27); live-weight gains were 0.74, 1.17, 0.86, 0.71, 0.88 and 1.03 kg/day (s.e. 0.057); and carcass gains were 0.48, 0.73, 0.56, 0.46, 0.56 and 0.63 kg/day (s.e. 0.037), respectively. Increasing the level of concentrate (offered with grass silage), maize maturity and level of maize inclusion reduced (P < 0.05) fat b* (yellowness). The potential daily concentrate-sparing effect, as determined by carcass gain, for the maize silages with DM concentrations of 217 and 304 g/kg offered as 0.5 and 1.0 of the forage component of the diet were 1.3, −0.3, 1.3 and 2.4 kg fresh weight, respectively. It is concluded that the response, in animal performance, including maize silage is dependent on the stage of maturity and level of inclusion in the diet. Maize silage with a DM of 304 g/kg offered ad libitum increased carcass gain by 31%, because of a combination of increased metabolizable energy (ME) intake and improved efficiency of utilization of ME, and produced carcasses with whiter fat.     

Effects of silage from maize crops differing in maturity at harvest,grass silage feed value and concentrate feed level on performance of finishing lambs

The effects of (i) medium and high feed value (MFV and HFV) maize silages and (ii) MFV and HFV grass silages, each in combination with a range of concentrate feed levels, on the performance of finishing lambs were evaluated using 280 Suffolk-X lambs (initial live weight 36.1 kg). The MFV and HFV maize silages represented crops with dry matter (DM) concentrations of 185 and 250 g/kg, respectively, at harvest, and had starch and metabolisable energy (ME) concentrations of 33 and 277 g/kg DM and 9.6 and 11.0 MJ/kg, respectively. HFV and MFV grass silages had DM and ME concentrations of 216 and 294 g/kg and 11.0 and 11.5 MJ/kg DM, respectively. A total of 13 treatments were involved. The four silages were offered ad libitum with daily concentrate supplements of 0.2, 0.5 or 0.8 kg per lamb. A final treatment consisted of concentrate offered ad libitum with 0.5 kg of the HFV grass silage daily. Increasing the feed value of grass silage increased (P < 0.001) forage intake, daily carcass and live weight gains, final live weight and carcass weight. Increasing maize silage feed value tended to increase (P = 0.07) daily carcass gain. Increasing concentrate feed level increased total food and ME intakes, and live weight and carcass gains. There was a significant interaction between silage feed value and the response to concentrate feed level. Relative to the HFV grass silage, the positive linear response to increasing concentrate feed level was greater with lambs offered the MFV grass silage for daily live weight gain (P < 0.001), daily carcass gain (P < 0.01) and final carcass weight (P < 0.01). Relative to the HFV maize silage, there was a greater response to increasing concentrate feed level from lambs offered the MFV maize silage in terms of daily carcass gain (P < 0.05) and daily live weight gain (P = 0.06). Forage type had no significant effect on the response to increased concentrate feed level. Relative to the MFV grass silage supplemented with 0.2 kg concentrate, the potential concentrate-sparing effect of the HFV grass silage, and the MFV and HFV maize silages was 0.41, 0.09 and 0.25 kg daily per lamb, respectively. It is concluded that increasing forage feed value increased forage intake and animal performance, and maize silage can replace MFV grass silage in the diet of finishing lambs as performance was equal to or better (depending on maturity of maize at harvest) than that for MFV grass silage.     

Effects of ensiled forage legumes on performance of store finishing lambs

Male Beulah speckled face lambs (initial live weight (LW) 28.8 ± 0.31 kg) were allocated to three dietary treatments to evaluate the performance of store lambs of a hill breed when offered ensiled lucerne (Medicago sativa), red clover (Trifolium pratense) or ryegrass. Second-cut silage bales (wilted and inoculated) were prepared from 3-year old lucerne and red clover stands and a 1-year old ryegrass sward. All the lambs were group-housed and offered ad libitum ryegrass silage during a 3-week co-variate period. This was followed by a week of dietary changeover period, after which the lambs were housed individually and offered their treatment diet ad libitum. All the lambs received a flat rate supplement of pelleted molassed sugarbeet (250 g fresh weight/day). Individual intakes were determined daily, and weekly measurements of LW and body condition score (CS) were made. Additional measurements were taken by scanning the lambs for depth of Longissimus dorsi (LD) muscle and subcutaneous fat. Over an experimental period of 7 weeks, the lambs offered red clover silage had a higher voluntary silage dry matter (DM) intake, total DM intake and metabolisable energy (ME) intake (P < 0.001) than lambs offered either lucerne or ryegrass silage. This resulted in a faster (P < 0.001) growth rate and increase (P < 0.001) in CS, with no difference between lucerne and ryegrass silages. The feed conversion efficiency (FCE) was 8.0 ± 0.61 kg feed/kg gain for lambs fed red clover silage, compared with 16.6 ± 2.82 and 10.6 ± 1.94 kg feed/kg gain for lucerne and ryegrass silage, respectively. The CP intake was higher (P < 0.001) for lambs fed the lucerne and red clover silages than for the ryegrass silage treatment. The concentration of plasma total protein (TP) was higher (P < 0.05) for lambs offered ryegrass silage versus lucerne and red clover silage. Urea concentrations were highest for lambs fed lucerne silage and lowest for those fed ryegrass silage (P < 0.05). The glucose concentration was higher (P < 0.05) for lambs offered red clover silage, whereas non-esterified fatty acids (NEFA) concentration was higher (P < 0.05) for lambs offered lucerne silage. Substituting ryegrass silage with red clover silage has the potential to improve the performance of finishing store lambs.     

Nitrogen metabolism and blood metabolites in three goat breeds fed increasing amounts of protein

Twelve wethers (27–33 kg and 12–14 months of age) representing meat (Nubian), milk (Alpine) and mohair (Angora) producing goats were used to evaluate breed differences in protein utilization with diets containing 9 (L), 15(M) or 21% CP (H) and 2.4 Mcal ME/kg DM in a digestion trial. Fecal N, urine N and absorbed N as percent of N intake were not affected (P>0.05) by breed. Retained N as percent of absorbed N was not different (P>0.05) between breeds. Ruminal propionate (molar %) was lower (P<0.05) in Angora, but other ruminal VFA and ammonia-N were not affected (P>0.05) by diet or breed. Plasma urea-N increased (P<0.01) with dietary CP level (8.3, 22.0 and 33.3 mg/dl for L, M and H, respectively), and concentrations were lowest for Angoras and highest for Nubians (18.5 vs. 21.2 vs. 23.9 mg/dl) (P<0.01). Plasma total protein (mean 69.7 g/l), glucose (mean 83.1 mg/dl), non-esterfied fatty acids (mean 101.4 μEq/l) and cortisol (mean 10.8 ng/ml) were not affected (P>0.05) by breed or diet. Plasma glucagon concentrations increased (P<0.05) with increasing CP intake (72.4, 167.6 and 239.1 pg/ml for L, M and H, respectively). The study indicated that there was no apparent breed difference between Nubian, Alpine and Angora goats in nitrogen utilization when goats were fed pelleted diets containing 9 to 21% CP.     

Effects of copper source and concentration on copper status and immune function in growing and finishing steers

Forty-eight individually fed purebred Angus steers (7±1.1 mo of age, 218±9.1 kg BW) were used to determine the effects of copper (Cu) source and concentration on Cu status and immune function. Steers were stratified by weight and initial liver Cu concentration and randomly assigned to one of five treatments. Treatments were: (1) control (no supplemental Cu), (2) 10 mg Cu/kg dry matter (DM) from Cu sulfate (CuSO₄), (3) 10 mg Cu/kg DM from a Cu-amino acid complex (Availa Cu; Zinpro Corporation, Eden Prairie, MN, USA), (4) 20 mg Cu/kg DM from CuSO₄, and (5) 20 mg Cu/kg DM from Availa Cu. Steers were housed in individual pens and fed an alfalfa-corn based growing diet (7.1 mg Cu/kg DM) for 56 d then gradually switched to a high concentrate diet (6.1 mg Cu/kg DM) for 144 d. On d 56 of the growing phase and d 112 of the finishing phase, liver Cu concentrations were higher (P<0.01) in Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher (P<0.01) liver Cu concentrations than steers receiving 10 mg Cu/kg DM. On d 112 of the finishing phase, steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P<0.01) liver Cu concentrations than steers supplemented 20 mg Cu/kg DM from CuSO₄. Cell mediated immune response to phytohemagglutinin was higher (P<0.01) in steers supplemented with 20 mg Cu/kg DM compared to steers supplemented with 10 mg Cu/kg DM. Total immunoglobulin (Ig) and immunoglobulin G (IgG) concentrations specific to pig red blood cells (PRBC) were higher (P<0.01) in steers supplemented with 10 mg Cu/kg DM from CuSO₄ than steers supplemented with 10 mg Cu/kg DM from Availa Cu. During the finishing phase, IgG concentrations specific to PRBC were higher (P<0.03) and antibody titers specific to ovalbumin (OVA) were lower (P<0.05) in control steers relative to Cu supplemented steers. Steers receiving 20 mg Cu/kg DM had higher (P<0.02) antibody titers specific to OVA than steers receiving 10 mg Cu/kg DM. Steers receiving 20 mg Cu/kg DM from Availa Cu had higher (P<0.01) antibody titers specific to OVA than steers supplemented with 20 mg Cu/kg DM from CuSO₄. Results indicate that the immune response to an antigen varies depending on the type of antigen administered as well as the concentration and source of Cu supplemented.     

Digestion, rumen fermentation and circulating concentrations of insulin, growth hormone and IGF-1 in steers fed diets based on different proportions of maize silage and grass silage

Replacing grass silage with maize silage results in a fundamental change in the ratio of structural to non-structural carbohydrates with commensurate changes in rumen fermentation patterns and nutrient utilisation. This study investigated the effects of feeding four forage mixtures, namely grass silage (G); 67 g/100 g grass silage + 33 g/100 g maize silage (GGM); 67 g/100 g maize silage + 33/100 g grass silage (MMG); maize silage (M) to four ruminally and duodenally canulated Holstein Friesian steers. All diets were formulated to be isonitrogenous (22.4 g N/kg DM) using a concentrate mixture. Dietary dry matter (DM) and organic matter (OM) digestibility increased with ascending maize silage inclusion (P < 0.1) whereas starch and neutral detergent fibre digestibility declined (P < 0.05). Ratio of non-glucogenic to glucogenic precursors in the rumen fluid increased with maize silage inclusion (P < 0.01) with a commensurate reduction in rumen pH (P < 0.05). Mean circulating concentrations of insulin were greatest and similar in diets MMG and GGM, lower in diet M and lowest in diet G (P < 0.01). There were no effects of diet on the mean circulating concentration of growth hormone (GH), or the frequency, amplitude and duration of GH pulses, or the mean circulating concentrations of IGF-1. Increasing levels of DM, OM and starch intakes with the substitution of grass silage with maize silage affected overall digestion, nutrient partitioning and subsequent circulating concentrations of insulin.     

Temperate forages ensiled with molasses or fresh cheese whey: Effects on conservation quality, effluent losses and ruminal degradation

Effects of ensiling and adding molasses or increasing levels of fresh cheese whey on the conservation and rumen degradability of temperate pasture silages were evaluated. Forage from three paddocks of mixed grass and legume pastures was used to make 45 silages (15 silages per paddock) with 5 treatments, including silage without additives (control), silage with 15 g/kg dehydrated molasses and silage with 20, 50 and 100 g/kg fresh cheese whey. The chemical composition and fermentation quality (i.e., pH, ammonia N, loss of dry matter (DM) and neutral detergent fibre (NDF), effluent production) of the silages were determined. Fresh and ensiled materials were evaluated for in situ rumen degradability. Ensiling reduced DM and NDF rumen degradability (P<0.01). When additives were employed, the reduction of DM degradability of the silages decreased (P≤0.03). Addition of molasses led to the lowest pH (P<0.01) and DM losses (P<0.01), and highest DM degradability (P<0.01). The conservation and DM degradation results of dried molasses silage was superior to those of fresh whey silages. In general, an increase in the level of whey increased DM degradability (P≤0.03), but linearly increased effluent production (P<0.01) and losses (P<0.01).     

Effects of oilseed meals and grain–urea supplements fed infrequently on digestion in sheep: 2. Cereal straw diets

An experiment examined the intake, growth responses and rumen digestion of young sheep fed ad libitum oat or barley straws alone or supplemented with approximately isonitrogenous amounts of barley grain and urea (Bar/N), safflower seed meal (SAF) or linseed meal (LIN) supplements provided at 3 day intervals. The supplements comprised 15–22% of total dry matter (DM) intake. Sheep offered either of the straws alone consumed 35.0–37.2 g DM/kg liveweight (LW^0.75) per day of straw and an estimated 2.03–2.07 MJ metabolizable energy (ME) per day, and lost 85–97 g LW per day. Supplements increased (P<0.05 or <0.001) voluntary intake of straw and of total DM, and the organic matter (OM) digestibility of the entire diet. Each of the supplements increased (P<0.001) the estimated ME intake to a similar extent and changed the rapid LW loss of sheep fed straw alone to approximate LW maintenance. Rumen ammonia concentrations in sheep fed barley and oat straws alone (12 and 24 mg NH₃/l, respectively) were expected to be deficient for microbial activity, but were increased (P<0.001) by provision of the supplements. Digestion of straw in synthetic fibre bags incubated in the rumen was markedly increased (P<0.01 or <0.001) when supplements were provided. Rumen pH was depressed briefly to pH <6.0 by the Bar/N, but not by the LIN or SAF, supplements. In young sheep fed cereal straws and losing LW rapidly the oilseed meal supplements increased wool growth more than the barley grain–urea supplements, but both types of supplement increased ME intake similarly and were equally effective to reduce the extent of LW loss.     

Milk production responses and rumen fermentation of dairy cows supplemented with summer brassicas

Forage brassicas, such as summer turnip (ST; Brassica rapa) and forage rape (FR; Brassica napus), are used as supplementary crops during summer. However, studies with lactating dairy cows fed these forages are limited and report inconsistent productive responses. The aim of this study was to determine dry matter intake, rumen fermentation and milk production responses of dairy cows in mid-lactation supplemented with and without summer (‘ST’ or ‘FR’) brassicas. Twelve multiparous lactating dairy cows were randomly allocated to three dietary treatments in a replicated 3 × 3 Latin square design balanced for residual effects over three 21-day periods. The control diet consisted of 16.2 kg DM of grass silage, 2.25 kg DM of commercial concentrate and 2.25 kg DM solvent-extracted soybean meal. For the other two dietary treatments, 25% of the amounts of silage and concentrates were replaced with FR or ST. The inclusion of forage brassicas had no effects on milk production (24.2 kg cow/day average) and composition (average milk fat and protein 43.2 and 33.6 g/l, respectively). Dry matter intake was 0.98 kg and 1.12 kg lower for cows supplemented with FR and ST, respectively, resulting in a greater feed conversion efficiency (1.35 kg milk/kg DM for ST and FR v. 1.27 kg milk/kg DM for the control diet). Intraruminal pH was lower for cows supplemented with ST compared to the control diet; however, it did not decrease below pH 5.8 at any time of the day. After feeding, the concentrations of total short-chain fatty acids (SCFAs) in rumen contents increased with ST supplementation compared to the control diet. Inclusion of FR in the diet increased the molar proportion of acetate (68.5 mmol/100 mmol) in total SCFA at the expense of propionate, measured 6 h after feeding of the forage. The molar proportion of butyric acid was greater with ST and FR supplementation (13.1 and 12 mmol/100 mmol, respectively) than in control cows. The estimated microbial nitrogen (N) flow was 89.1 g/day greater when supplementing FR compared to the control diet. Based on the haematological measures, the inclusion of summer brassica forages did not affect the health status of the animals. These results indicate that mid-lactation dairy cows fed brassicas are able to maintain production despite the reduced intake, probably due to improved rumen fermentation and therefore nutrient utilization.     

Evaluation of the factors affecting silage intake of dairy cows: a revision of the relative silage dry-matter intake index

An evaluation of the factors affecting silage dry-matter intake (SDMI) of dairy cows was conducted based on dietary treatment means. The data were divided into six subsets based on the silage treatments used in the experiments: concentration of digestible organic matter in dry matter (D-value) influenced by the maturity of grass ensiled (n = 81), fermentation quality influenced by silage additives (n = 240), dry matter (DM) concentration influenced by wilting of grass prior to ensiling (W; n = 85), comparison of silages made from primary growth or regrowth of grass (n = 46), and replacement of grass silage with legume (L; n = 53) or fermented whole-crop cereal (WC; n = 37) silages. The data were subjected to the mixed model regression analysis. Both silage D-value and fermentation quality significantly affected SDMI. The average effects of D-value and total acid (TA) concentration were 17.0 g and − 12.8 per 1 g/kg DM, respectively. At a given D-value, silage neutral-detergent fibre (NDF) concentration tended to decrease SDMI. Silage TA concentration was the best fermentation parameter predicting SDMI. Adding other parameters into the multivariate models did not improve the fit and the slopes of the other parameters remained insignificant. Total NDF intake was curvilinearly related to silage D-value the maximum intake being reached at a D-value of 640 g/kg DM. Results imply that physical fill is not limiting SDMI of highly digestible grass silages and that both physical and metabolic factors constrain total DM intake in an interactive manner. Silage DM concentration had an independent curvilinear effect on SDMI. Replacing primary growth silage with regrowth, L or WC silages affected SDMI significantly, the response to regrowth silage being linearly decreasing and to L and WC quadratically increasing. The outcome of factors affecting SDMI was used to update the relative SDMI index as follows: SDMI index = 100+10 × [(D-value − 680) × 0.0170 − (TA − 80) × 0.0128+(0.0198 ×  (DM − 250) − 0.00002364 × (DM² − 250 ²)) − 0.44 × a+4.13 × b − 2.58 × b²+5.90 × c − 6.14 × c² − 0.0023 × (550 − NDF)], where a, b and c represent the proportions (0–1) of regrowth, L or WC silages from total silage DM. For the whole data set, one index unit corresponded to the default value of 0.10 kg in SDMI. The SDMI index explained proportionally 0.852 of the variation in SDMI with 0.34 kg DM per day residual. The updated SDMI index provides improved basis for the practical dairy cow ration formulation and economic evaluation.     

Effects of Agave salmiana Otto Ex Salm-Dyck silage as forage on ruminal fermentation and growth in goats

Ensiling of Agave salmiana Otto Ex Salm-Dyck, a widespread plant in Mexico, as a viable preservation method to create a potential animal feed resource for ruminants was investigated. Fresh A. salmiana with 205 g dry matter (DM)/kg and wilted alfalfa with 602 g DM/kg were ensiled in combinations (DM:DM) of 1000:0, 500:500 and 350:650, to evaluate feeding value of agave:alfalfa silages on ruminal fermentation and growth of goats. Chemical composition and in situ ruminal disappearance of three total mixed rations (TMRs), which included 240 g/kg DM of each silage (1000:0, 500:500 and 350:650) were determined. The TMR were used to assess ruminal fermentation and growth of 15 goats (20 ± 2.2 kg body weight (BW)). Silage pH (≤4), lactate (>25 g/kg DM) and ammonia (<50 g/kg total N) concentrations indicate that silage quality was good. Lactic acid was the main acid in all silages, acetic acid concentrations were relatively low, and butyrate was only detected in only the 1000:0 agave:alfalfa silage. Potential DM disappearance of the TMR increased quadratically as the amount of alfalfa included in the silage mixture increased. The BW gain and feed efficiency were not changed by treatment, even though DM intake decreased and aNDF intake increased linearly as the amount of alfalfa included in the silage mixture increased. Ruminal pH and butyrate increased, and ammonia N, lactate and propionate decreased linearly as alfalfa proportion of alfalfa in the silage mixture was increased. The TMR ingredient selectivity by the goats may have limited goat performance when alfalfa was included in agave silage mixtures. Because the agave:alfalfa blend improved nutritional quality, ruminal digestibility and intake of agave silage, alfalfa inclusion may improve nutritional characteristics of agave plants silages for ruminants.     

Effects of oilseed meal and grain-urea supplements fed infrequently on digestion in sheep: 1. Low quality grass hay diets

An experiment examined intake, growth response and rumen digestion of young sheep fed ad libitum low quality grass hay alone or supplemented with approximately isonitrogenous amounts of barley grain and urea (Bar/N), safflower meal (SAF) or linseed meal (LIN) provided at 3 days intervals. Supplements comprised 13–20% of total DM intake. Sheep fed grass hay alone consumed 60.2 g DM/kg LW^0.75/day of hay and an estimated 6.09 MJ metabolizable energy (ME)/day, and were in liveweight (LW) maintenance. Hay intake was decreased (P<0.05) by the Bar/N supplement with a substitution rate of 0.9, but was not changed by the oilseed meal supplements. Each of the supplements increased (P<0.05) estimated ME intake to a similar extent, but LW gain and wool growth were lower (P<0.05) in sheep supplemented with Bar/N than those supplemented with LIN. Rumen degradabilities of the SAF and LIN CP were estimated to be 0.72 and 0.62, respectively. Rumen ammonia concentrations in sheep fed hay alone (average 97 mg NH₃/l) were expected to be adequate for microbial activity. Fractional outflow rate (FOR) of liquid from the rumen measured with Co-EDTA (mean 0.109 h⁻¹) was greater than that of Cr-mordanted supplements (mean 0.056 h⁻¹), which was in turn greater than the FOR of Cr-mordanted hay (mean 0.031 h⁻¹). Diet did not affect these FOR. Supplemented sheep accommodated increased DM intake on Day 1 of the 3 day supplementation cycle by increasing rumen digesta load rather than by increasing rate of passage of digesta. Results show that the LW gain of young sheep fed low quality hay was increased more by either oilseed meal than by equivalent amounts of barley grain/urea supplement, apparently due to more efficient utilization of ME for LW gain.     

Grass and lupin silage in rations for beef steers supplemented with barley or potatoes

Twenty-eight Simmental-cross steers weighing 200 (± 20.5) kg were used to evaluate grass and whole plant lupin silages in terms of growth rate, dry matter (DM) intake and carcass characteristics. The chemical composition of the silages was determined and Dacron bag procedures were used to estimate DM and protein degradability. The silages were supplemented with either rolled barley or crushed potato. The lupin silage had a lactic acid fermentation with lower DM, neutral detergent fiber (NDF) and protein nitrogen than the grass silage but higher crude protein. There were no statistically significant differences in gain, carcass weight, dressing percentage or backfat levels between steers fed lupin or grass silage. DM intake of the silages was not significantly different but there was a tendency for lower DM intake of lupin silage when supplemented with potatoes. There was no difference in DM degradability between lupin and grass silages. Lupin nitrogen degraded at a significantly faster rate (24.5% h⁻¹) compared with the grass (10.4% h⁻¹). The effective degradation of nitrogen at a ruminal fractional outflow rate of 0.05 h⁻¹ was 63.8% and 79.1% for grass and lupin silage, respectively. Ensiling whole plant lupin can produce a high quality silage for use in beef rations.     

The effects of barley, unmolassed sugar-beet pulp and molasses supplements on organic matter, nitrogen and fibre digestion in the rumen of cattle given a silage diet

In a 4 × 4 Latin-square experiment with a 2 × 2 factorial arrangement of treatments, 4 cattle fitted with a rumen and duodenal cannula were given four grass-containing diets [480 g kg⁻¹ of the total dry matter (DM) intake] and barley (BU), barley + molasses (2:1) (BM), sugar-beet pulp (SU) or sugar-beet pulp + molasses (SM). Duodenal flow was estimated using Cr-mordanted straw and CoEDTA as markers, and microbial nitrogen entering the small intestine using purine bases of nucleic acids.

Molasses-containing diets had a higher (P < 0.01) organic matter (OM) digestibility. The proportion of digestible OM apparently disappearing in the rumen averaged 0.72 and was not significantly affected by the diet. When cattle received molasses, the quantity of microbial N entering the small intestine was higher (P < 0.05) and there was a trend towards a higher efficiency of microbial N synthesis (28.8 vs. 25.6 g N kg⁻¹ OM apparently digested in the rumen). When S diets were consumed, total non-ammonia N flow at the duodenum exceeded N intake by 7.0 g day⁻¹ and when B diets were consumed, it was 0.7 g day⁻¹ less than N intake. Feed N degradability in the rumen and apparent N digestibility of S diets were lower (P < 0.05; P < 0.001) than those of B diets.

Rumen (P < 0.05) and total (P < 0.001) digestibility of neutral detergent fibre (NDF) and acid detergent fibre (ADF) was higher when S diets were given. The proportion of digestible fibre disappearing in the rumen was not affected by the diet. The rate and extent of silage and hay DM degradation were not significantly affected by the diet. However, dietary inclusion of molasses decreased (P < 0.05) the lag time of both hay and silage DM degradation.

The rumen dilution rate of liquid averaged 0.097 and that of particles, 0.049; neither was significantly different for either B and S diets or U and M diets. Duodenal liquid flow was higher (P < 0.05) for M diets.

Average rumen pH was not affected by the diet, but the molasses diets increased (P < 0.05) the range in rumen pH. The BM diet was associated with higher (P < 0.01) rumen ammonia concentration than the other diets. Low rumen ammonia concentrations (< 2 mM) were observed for long periods between feeds. The molar proportion of butyrate was higher on B diets and there was a trend towards a higher proportion of acetate and propionate on S diets. Molasses tended to increase the molar proportion of propionate and butyrate.     

Effect of the rate of increase in concentrate allowance with concentrates high or low in starch on the performance of dairy cows in early lactation

The effect of the rate of increase in concentrate allowance after calving with two concentrate mixes (A and B) differing in composition was evaluated using 64 Finnish Ayrshire cows during the first 100 days of lactation. After calving, the concentrate allowance of multiparous cows was increased stepwise from 4 to 17 kg/day, and of primiparous cows from 3 to 13.5 kg/day over 12 days (F rate of increase; multiparous 1.08 kg/day, primiparous 0.88 kg/day) or 24 days (S rate of increase; mutiparous 0.54 kg/day, primiparous 0.44 kg/day). The concentrates were formulated to have similar crude protein and metabolizable energy concentrations but differing starch and NDF concentrations. For concentrate A the starch and NDF concentrations were 421 and 167 g/kg dry matter (DM) and for concentrate B 258 and 251 g/kg DM. All cows received grass silage ad libitum. The higher concentrate intake during weeks 1 to 4 of lactation with F compared with the S rate of increase caused higher DM, energy and protein intake. The higher concentrate intake for F than for S treatment in early lactation did not cause a large decrease in silage intake (8.8 v. 8.3 kg DM/day). The intake of concentrate A and B after calving did not differ for S treatment. However, for F treatment the intake of fibrous concentrate B increased faster than starch-rich concentrate A during weeks 1 to 4 of lactation. The concentrate composition had no effect on energy-corrected milk (ECM) yield during weeks 1 to 4 of lactation for S treatments, but with F treatments the cows fed B concentrate produced more milk. The F rate of increase in concentrate allowance compared with the S rate increased the calculated energy balance after calving. The rate of increase in concentrate feeding post partum or concentrate composition had no effect on DM, energy or protein intake during the whole 100-day experiment. The average ECM yield over days 1 to 100 of lactation was higher for S than for F treatments and tended to be higher with concentrate B than A. Results of this study showed that by the fast rate of increase in concentrate allowance after calving on a grass silage diet, it was possible to improve the energy status of the cows in early lactation. This had, however, no effect on production later in lactation.     

Effect of volatile compounds in grass silage on voluntary intake by growing cattle

Twenty-four low dry matter (DM) silages differing in fermentation quality were harvested at the same time from a crop that consisted mainly of timothy (Phleum pratense), and meadow fescue (Festuca pratensis). The silage samples were analysed by gas chromatography (GC) - mass spectrometry and gas chromatography - flame ionisation detection in order to determine and quantify volatiles present in silage. The voluntary intake of the 24 silages had been measured in a previous feeding trial with growing steers of Norwegian Red. Thirteen esters, five aldehydes, three alcohols, and one sulphide were identified and quantified. A total of 51 variables describing the chemical composition of the silages were included in a partial least-squares regression, and the relationship of silage fermentation quality to voluntary intake was elucidated. The importance of variables describing silage fermentation quality in relation to intake was judged from a best combination procedure, jack-knifing, and empirical correlations of the variables to intake. The GC-analysed compounds were mainly present in poorly fermented silages. However, compared with other explanatory chemical variables none of these compounds was of importance for the voluntary intake as evaluated by partial least-squares regression. A validated variance of 71% in silage DM intake was explained with the selected variables: total acids (TA), total volatile fatty acids (TVFA), lactic acid/total acid ratio and propionic acid. In this study extent (by the variable TA) and type of silage fermentation (by TVFA) influenced intake. Further, it is suggested that by restricting the fermentation in low DM grass silages the potential intake of silage DM is maximised.     

Effects of grass and maize silage feed value,offering soybean meal with maize silage,and concentrate feed level in late pregnancy,on ewe and lamb performance

In many countries, daily herbage accumulation on pasture declines towards zero during the winter period; thus, many pregnant ewes are housed and offered conserved forages supplemented with concentrate prior to parturition. The effects of forage type and feed value (FV), offering soybean meal with maize silage during mid and late pregnancy, and concentrate feed level in late pregnancy on the performance of ewes and their progeny (to slaughter) were evaluated. Ewes (n = 151) were assigned to one of nine treatments from mid-pregnancy until lambing. Medium FV and high FV grass silages (metabolisable energy concentrations of 10.7 and 12.0 MJ/kg DM) were offered ad libitum supplemented with either 15 or 25 kg concentrate/ewe during late pregnancy. Low and high DM maize silages (starch concentrations of 80 and 315 g/kg DM) were offered ad libitum either alone or with soybean meal (200 g/d) and supplemented with 15 kg concentrate during late pregnancy. A final treatment consisted of high FV grass silage supplemented with 5 kg soybean/ewe over the final 4 weeks of pregnancy. Ewes and lambs were put to pasture in a rotational-grazing system within 3 days of lambing. There were no interactions (P > 0.05) between grass silage FV and concentrate feed level for ewe or lamb traits. Increasing grass silage FV increased food intake (P < 0.001) during late pregnancy, ewe BW and body condition score (BCS) at lambing (P < 0.001), lamb BW at birth (P < 0.001) and weaning (P < 0.05), and reduced age at slaughter (P = 0.06). Increasing concentrate feed level increased metabolisable energy (P < 0.05) intake during late pregnancy but had no effect (P > 0.05) on ewe or lamb performance. Increasing maize DM at harvest and offering soybean meal with maize silage increased food intake (P < 0.001) and ewe BW and BCS at lambing (P < 0.05 or P < 0.01). Offering soybean meal with maize silage increased lamb BW at birth (P < 0.01) and reduced age at slaughter (P < 0.05). Reducing supplementation of high FV grass silage to 5 kg of soybean meal had no effect (P > 0.05) on animal performance. Replacing grass silage with maize silage did not affect (P > 0.05) BW gain of lambs. It is concluded that increasing the FV of the grass silage offered during pregnancy had the greatest positive impact on ewe and lamb performance.