Nutrient composition and in vitro ruminal fermentation of tropical legume mixtures with contrasting tannin contents

Various combinations of a low-tannin herbaceous legume (Vigna unguiculata) and foliage of tanniniferous shrub legumes (Calliandra calothyrsus, Flemingia macrophylla and Leucaena leucocephala) or a low-tannin shrub legume (Cratylia argentea), all mixed together with a low-quality tropical grass (Brachiaria humidicola), were tested in vitro for differences in the effects on ruminal fermentation. Two experiments with the gas transducer technique were carried out, where each forage mixture was tested either with or without polyethylene glycol in order to be able to identify tannin-related effects (n = 3). In Experiment 1, a stepwise replacement of V. unguiculata by C. calothyrsus (5:0, 4:1, 3:2, 2:3, 1:4, 0:5) at a legume proportion of 1/3 or 2/3 in the mixture was evaluated. Together with two grass-alone and four pure legume treatments this added up to 30 treatments. In Experiment 2, V. unguiculata was gradually replaced by each of the four shrub legumes (3:0, 2:1, 1:2, 0:3) in grass–legume ratios of 2:1, adding up, together with two grass-alone treatments, to 28 treatments. When added alone, V. unguiculata resulted in high fermentative activity as measured by gas production and kinetics as well as low proportion of undegraded crude protein. When V. unguiculata was replaced by the low-tannin C. argentea in Experiment 2, there was no noticeable difference (P>0.05) in fermentative activity. In both experiments, the effect of the substitution of V. unguiculata by tanniniferous shrub legumes resulted in a declining gas production and an increasing proportion of undegraded crude protein (P<0.001). However, the extent of these changes depended on the level of replacement and the shrub legume species (P<0.001). The results of Experiment 2 illustrate that this was the consequence not only of different tannin contents (less adverse effects with L. leucocephala than with C. calothyrsus) but also differences in the chemical properties of the tannins present in these shrub legume species (much less adverse effects with L. leucocephala than with F. macrophylla despite similar tannin contents). Furthermore these results indicate that, once the extent of the effects of a tanniniferous legume is known, one may calculate the maximal level of replacement of a low-tannin legume in a grass diet possible without negative effects on ruminal fermentation. This allows to improve dry season grass-based diets with as few as possible of the expensive and less well growing low-tannin legume.     

The application of the n-alkane technique for estimating the composition of diets consumed by equines and cattle feeding on upland vegetation communities

The application of n-alkanes as faecal markers to estimate diet composition of equines and cattle was studied. Twelve mature crossbreed mares (385 ± 47 kg live weight – LW) and six adult non-lactating cows (499 ± 36 kg LW) of Asturiana de los Valles breed were divided in groups of three animals (H1, H2, H3 and H4 in equines and C1 and C2 in cattle) and housed in individual stalls. Animals received a daily total amount of 1.0 kg DM/100 kg LW of different experimental diets composed of herbaceous (Lolium perenne L.) and woody species (Ulex gallii Planchon and heather: Erica spp. and Calluna vulgaris L.). Diet composition varied among treatments: H1 and C1 – L. perenne as sole component; H2 and C2 – L. perenne (0.70) and heather (0.30); H3 – L. perenne (0.70) and U. gallii (0.30); H4 – L. perenne (0.40), heather (0.30) and U. gallii (0.30).     

Chemical composition and rumen degradability of three corn hybrids treated with insecticides against the European corn borer (Ostrinia nubilalis)

This experiment determined the chemical composition, rumen degradability (aNDF in stalks and starch in kernels) and in vitro gas production of kernels from three corn hybrids treated (TT) or not treated (control, CTR) with insecticides against the European corn borer (ECB, Ostrinia nubilalis). Two whole-plant silage hybrids belonging to the FAO rating 600 and 700 maturity class (S600 and S700, respectively) and one selected for grain production (G600, FAO rating 600, Dekalb-Monsanto Agricoltura S.p.A., Lodi, Italy) were sown in two main plots (TT and CTR) of an experimental field. Two subsequent treatments of pyrethroids (25 and 1.2 g/ha of cyfluthrin and deltamethrin, respectively) were applied to the TT plots. The insecticide treatment reduced the number of damaged plants (4.5 broken plants/plot versus 0.3 broken plants/plot, P<0.01) and increased the total grain yield by 11% (13.8 t/ha versus 12.4 t/ha), while hybrids did not differ. ECB larvae which bored into the stalk tunnels modified the chemical composition of stalks and kernels. In stalks, total sugars content (i.e. glucose, fructose, sucrose) was about twice that in TT versus CTR plants (123 g/kg versus 60 g/kg DM, P<0.01), while aNDF content was higher in CTR stalks (765 versus 702 g/kg DM, P<0.01). DM degradability after 48 h of incubation of stalks was higher in TT than in CTR, both in vitro (0.360 versus 0.298, P<0.01) and in situ (0.370 versus 0.298, P<0.05), while there were no differences in aNDF degradability. Kernels from TT plots contained less DM (615 g/kg versus 651 g/kg, P<0.01) and more CP (84 g/kg and 78 g/kg DM, P<0.05) than those from CTR plots, while in situ rumen starch disappearance and in vitro gas production were similar. Corn hybrid selected for yield of grain (G600) differed from S600 and S700 due to a higher (P<0.01) content of aNDF, ADF and lignin(sa) in the stalks, and a higher starch content (696 g/kg versus 674 and 671 g/kg DM, P<0.01) and CP (87 g/kg versus 77 and 76 g/kg DM, P<0.05) in grain. The G600 hybrid produced stalks with a lower (P<0.01) aNDF rumen degradability than the S600 and S700.     

Microbial inoculant effects on silage and in vitro ruminal fermentation, and microbial biomass estimation for alfalfa, bmr corn, and corn silages

Whole crop third cut alfalfa, brown mid-rib (bmr) corn, and corn were chopped and inoculated with one of four microbial inoculants used. Uninoculated silage was the control treatment. Each crop was ensiled in four mini-silos (1 L glass jars) per treatment. All silos were fermented for 60 days at room temperature (22 °C), and then they were opened and analyzed for fermentation products, fiber constituents and N fractions. A fraction of wet silage was ground with a blender for 30 s. In vitro gas production was measured in 160 ml sealed serum vials at 3, 6, 9, 24, and 48 h using the wet ground silage. At 9 and 48 h, rumen fluid was analyzed for volatile fatty acids (VFA) and microbial biomass yield (MBY). In all the three crops, the four inoculants produced only minor changes in pH and fermentation products during ensiling. Of the variables measured, soluble nonprotein N fractions were the characteristics most often affected by some inoculants. At 9 h incubation, in vitro gas production and VFA did not differ between control and inoculated silages, but MBY did. Among crops, alfalfa and corn silages had higher MBY than did bmr corn silage. Among inoculants, three of the four inoculated silages produced more MBY than did control. At 48 h, alfalfa silage produced higher MBY than did corn or bmr silage, and two of the inoculated silages had more MBY than did the control. There was no inoculant by crop interaction. Results suggest that some silage inoculants are capable of altering rumen fermentation, even in cases where effects on silage fermentation are small, and that this effect may be linked to better preservation of crop protein during ensiling.     

Seasonal variations in the chemical composition and dry matter degradability of exclosure forages in the semi-arid region of northern Ethiopia

The present study was conduced at two sites (Tembien and Wukro) in the semi-arid region of Tigray in northern Ethiopia to investigate the seasonal dynamics in the chemical composition and dry matter digestibility of grass and browse species of exclosures. The browse species studied in Tembien and Wukro had a mean crude protein (CP) value of 166 and 117 g/kg dry matter (DM), respectively. The mean in vitro dry matter digestibility (IVDMD) coefficient and predicted metabolizable energy (ME) density of the browse species were 0.72 and 9.83 MJ/kg DM, respectively at Tembien, 0.62 and 8.38 MJ/kg DM, respectively, at Wukro. Neutral detergent fibre (NDF) and acid detergent fibre (ADF) values of the browse species varied from 192 to 437 and 127 to 391 g/kg DM, respectively. Acid detergent lignin (ADL) values ranged from 36 to 190 g/kg DM. The mean CP of the grass species in Tembien and Wukro during the long rainy season was 76 and 73 g/kg DM, respectively and values declined below a critical maintenance level during the dry and short rain seasons. Mean IVDMD and ME values for the two sites were 0.41 and 0.47, and 5.38 and 6.11 MJ/kg DM, respectively. The NDF, ADF, and lignin values of the grass species were generally above 700, 400, and 70 g/kg DM, respectively. The CP, IVDMD and ME values of the mixed grass samples differed (P<0.05) among harvesting months and values ranged from 20 to 103 g/kg DM, 0.47 to 0.72 MJ/kg DM, and 6.16 to 9.91 MJ/kg DM, respectively. The browse species could be used as useful dry season protein supplements to the N deficient native grass species. Especial emphasis should be given to propagate Maerua angolensis and Cadaba farinosa at community nursery sites. Harvesting in September, rather than the current extended harvest period that took place in October and November, can considerably improve the feeding value of native grass hay for smallholder ruminant production systems.     

Effect of zinc supplementation from two sources on growth,nutrient utilization and immune response in male crossbred cattle (Bos indicus×Bos taurus) bulls

To investigate effects of Zn supplementation on performance, mineral balance and immune response, 15 male crossbred cattle (Bos indicus×Bos taurus) bulls of about 14 ± 0.4 months of age and weighing 226.0 ± 9.1 kg were divided in to three groups of five. Bulls in the control group were fed wheat straw and a concentrate mixture (basal diet with 32.5 mg Zn/kg dry matter (DM)), and in ZnSO₄ and ZnProp groups 35 mg Zn/kg DM was added through Zn sulphate and Zn propionate, respectively. All bulls were fed their respective treatment diets for 180 days. Daily feed intake was recorded and bulls were weighed at every 15 days to determine change in body weight (BW). After 120 days of feeding, bulls were vaccinated with Brucella abortus strain 19, and cell mediated and humoral immune responses were assessed between 120 and 148 days of experimental feeding. After 150 days of feeding, a metabolism study of 6 days duration was completed to determine nutrient digestibility and mineral balances (i.e., Ca, P, Zn, Cu, Fe and Mn). Intake of total DM, digestibility of DM, crude protein, ether extract, neutral detergent fibre and acid detergent fibre, N balance, average daily gain, feed: gain did not differ between the groups. Intake, excretion and balance of Ca, P, Zn, Cu, Fe and Mn also did not differ between the groups. However, retention of Zn was higher (P<0.001) in the ZnProp group. Bulls supplemented with Zn propionate had higher cell mediated (P<0.01) and humoral (P<0.05) immune response, while there was no alteration in immune response due to Zn sulphate supplementation. Results indicate that a diet containing about 32.5 mg Zn/kg DM was adequate to support normal growth and digestibility, but a better immune response occurred when Zn propionate was added to the diet at 35 mg/kg DM versus Zn sulphate.     

Influence of urea calcium mixture supplementation on ruminal fermentation characteristics of beef cattle fed on concentrates containing high levels of cassava chips and rice straw

The purpose of this study was to evaluate the effects of various N sources in concentrates containing high levels of cassava chips, with rice straw as the basal forage, on rumen ecology, rumen microbial counts, microbial crude (CP) protein synthesis, and digestibility of nutrients. Four ruminally fistulated crossbred (Brahman × native) beef steers with initial body weight (BW) of 400 ± 40.2 kg were randomly assigned according to a 4 × 4 Latin square design. The dietary treatments were different sources of N in the concentrates and were: T1 = urea (control; urea); T2 = soybean meal (SBM); T3 = urea CaCl₂ mixture (U-Cal); T4 = urea CaSO₄ mixture (U-Cas). All steers were kept in individual pens and supplemented with concentrate at 5 g/kg of BW daily. The experiment was 4 periods, and each lasted 21 d. During the first 14 d, all steers were fed their respective diets ad libitum and for during the last 7 d, they were moved to metabolism crates for total urine and fecal collection. Dry matter intake ranged from 9.8 to 10.5 kg daily and was not altered by diet, while digestibility of NDF differed among treatments and was highest with U-Cas supplementation (P<0.05). Ruminal NH₃ N and plasma urea N with U-Cal, U-Cas, and SBM diets were lower compared with the urea supplemented group (P<0.05). Ruminal volatile fatty acid concentrations were not altered by treatments. Total viable, and cellulolytic bacteria, differed among treatments and were highest with U-Cas (9.1 × 10¹¹, and 4.0 × 10⁹ cfu/mL, respectively). In addition, efficiency of rumen microbial CP synthesis based on organic matter (OM) truly digested in the rumen was increased by SBM or U-Cal supplementation, and was highest with U-Cas supplementation (18.2 g of N/kg of OM truly digested in the rumen). Supplementation of U-Cas to a concentrate containing a high level of cassava chips improved rumen ecology and microbial CP synthesis in beef cattle, suggesting that urea calcium mixtures can replace soybean meal or urea in beef cattle diets without adverse affects on rumen fermentation and other rumen parameters.     

Chemical composition, intake by sheep, and in situ disappearance in cannulated cows of bermudagrass hayed at two moisture concentrations and treated with a non-viable Lactobacillus-lactic acid preservative

Bermudagrass [Cynodon dactylon (L.) Pers.] is commonly used for grazing and haying in the southern USA, but hay curing can be challenging due to frequent rainfall events during spring and early summer. An existing stand of ‘Greenfield’ bermudagrass was divided into 12 plots using a randomized complete block design with a 2×2 factorial treatment arrangement to evaluate the influence of a non-viable Lactobacillus-lactic acid preservative and moisture concentration at baling on chemical composition, intake by sheep, and in situ disappearance in cattle. At time of mowing, half of the plots in each block were either spray-treated (T) or not treated (U) with 81 mL/t forage dry matter (DM) of the preservative solution. Hay was then baled at target moisture concentrations of either 174 g/kg DM (L) or 267 g/kg DM (H). Maximum temperature and heating degree days were greater (P<0.05) from H compared with L during the 42-d storage period. An interaction between spray and moisture treatments tended (P<0.10) to affect recovery of DM; recoveries for LT (0.992) differed (P<0.10) from HT (0.913), but LU and HU were intermediate between the spray-treated hays, and did not differ from either (P>0.10). Post-storage nutritive value was largely influenced by moisture treatments only. Intake and digestibility, and in situ DM disappearance of these same hays were determined using 16 wether lambs (43 ± 3.7 kg initial BW), or six ruminally cannulated cows (617 ± 3.5 kg initial BW), respectively. Dry matter intake by sheep was not affected by either treatment factor (P>0.05), but DM digestibility and digestible DM intake were greater (P<0.05) from U compared with T. The in situ immediately soluble DM portion was greater from (P<0.05) L compared with H, but the reverse was true for the potentially degradable DM fraction. The lag time tended (P<0.10) to be greater from H compared with L. Treating bermudagrass with a non-viable Lactobacillus acidophilus-lactic acid spray product at time of baling may not offset the negative effects on forage quality and digestibility of baling bermudagrass hay at excessive moisture concentrations.     

Effect of harvest date and nitrogen fertilization rate on the nutritive value of amaranth forage (Amaranthus hypochondriacus)

This study was conducted to assess effects of harvest date (i.e., 40 and 60 d after planting) and N fertilization rate (i.e., 120, 180, 240 kg N/ha) on the nutritive value of amaranth forage (Amaranthus hypochondriacus) using a factorial experiment with a randomized complete block design. The content of dry matter (DM), crude protein (CP), true protein (TP), ether extract (EE), water soluble carbohydrates (WSC), ash-free neutral detergent fiber (NDFom), ash-free acid detergent fiber (ADFom), lignin(sa), ash, Ca, P, Na, K, oxalic acid and nitrate were determined. Soluble CP (SP) and protein fractions non-protein N (A), true protein rapidly degraded in the rumen (B₁), true protein degraded in the rumen at a moderate rate (B₂), true protein associated with the cell wall and slowly degraded in the rumen (B₃) and acid detergent insoluble CP (C) were measured according to the Cornell Net Carbohydrate and Protein System. In vitro gas production (IVGP), OM disappearance (OMD) and NDFom disappearance (NDFD) were determined using a gas production technique. Results showed that the later harvest date increased (P<0.05) DM, EE, WSC, NDFom, ADFom, lignin(sa), B₃ and C; while CP, TP, ash, Ca, P, K, SP, A, B₁, B₂, nitrate, total and soluble oxalic acid, IVGP, b (i.e., gas production from the insoluble fermentable fractions at 120 h), c (i.e., rate of gas production during incubation), OMD and NDFD decreased (P<0.05). With increasing N fertilization rate, CP, TP, EE, P, nitrate, oxalic acid, SP, A, b, OMD and NDFD increased (P<0.05), however B₂ declined (P<0.05). Increasing N fertilization increased yield, CP concentration and nutrient digestibility. At 40 d after planting use of amaranth forage as a ruminant feed is limited due to its high nitrate content. However, at 60 d, although a depression in digestibility and CP content occurred, this forage has the potential as a ruminant feed due to the much lower nitrate levels.     

Impacts of nutritional technology on feeds offered to horses: A review of effects of processing on voluntary intake,digesta characteristics and feed utilisation

Advances in feed processing technology applied to diet systems for ruminant livestock have been used extensively in the equine feed industry. The translation of these technologies is an important area of interest for the feed processing industry servicing the various sectors of the equine industry such as feeds for the racing, meat, milk and urine production, as well as supplements for leisure horse use. However, there are few reviews examining impacts of feed processing technologies on the processes controlling voluntary intake or utilisation of processed feeds by horses. In this paper, some of the specific features of feeds and impacts of feed processing on factors controlling meal pattern, frequency and size, and digestive physiology will be addressed. Three main areas are examined in this review, being impacts of feed processing on processes of “information gathering” (sensory and nutritional knowledge) by the horse, eating behaviour of the horse offered processed feeds (notably issues of preference and control of short-term ingestion rate), and implications of constraints of digestive physiology, process and function on voluntary intake and digestibility of processed feeds. The review highlights areas of future research and development for nutritional technology to increase knowledge of interactions between equine physiology and feed processing to enhance efficiency of capture of nutrients and maintain the welfare of horses managed in the housed environment.     

Nutritional characterization of Mucuna pruiriens: 2. In vitro ruminal fluid fermentability of Mucuna pruriens,Mucunal-dopa and soybean meal incubated with or without l-dopa

Three in vitro experiments were conducted to determine the rumen fermentability of Mucuna (M) pruriens (24 g 3,4-dihydroxy-l-phenylalanine (l-dopa)/kg dry matter (DM) and soybean meal treated with (SBD) or without (SB) 138 g l-dopa/kg DM). Additional objectives were to determine if l-dopa inhibits rumen fermentation, and if ruminal microbes can adapt to l-dopa or M. In Experiment 1, ground (1 mm) substrates were incubated in triplicate at 38 °C in 9 ml nutrient media and 1 ml rumen fluid in a series of six, 48 h, consecutive batch cultures. The first culture was inoculated with rumen fluid from two donor cows. Subsequent cultures were inoculated with fluid (1 ml) from the previous culture. The DM digestibility (DMD, 616 g/kg vs. 540 g/kg; P<0.01) and gas production (51.7 ml/g vs. 44.2 ml/g DM; P<0.05) were higher from fermentation of M versus SB but similar for SB and SBD (540 g/kg vs. 554 g/kg and 44.2 ml/g DM vs. 43.5 ml/g DM, respectively). The slopes of the relationships between DMD (g/kg) or gas production (ml/g DM) and fermentation period were not reduced by fermenting M (−0.014 DMD slope; 2.28 gas production slope) or SBD (−0.014 DMD slope; 0.459 gas production slope), instead of SB (−0.002 DMD slope; 1.039 gas production slope), indicating microbial adaptation to M and SBD. Total volatile fatty acid concentration (VFA; 53.7, 54.9 and 54.9 mmol/l) and molar proportions of VFA were similar among substrates. Gas production kinetics of M versus SB (Experiment 2), and SB versus SBD (Experiment 3) were also measured after substrates were incubated in triplicate in buffered rumen fluid for 24 h using a non-linear exponential model to fit the data. Residual l-dopa was measured after separate fermentation of substrates in triplicate for 0, 4, 8, 16 and 24 h. Fermentation of M versus SB produced more (P<0.05) gas (250 ml/g vs. 100 ml/g DM) and total VFA (203 mmol/l vs. 180 mmol/l) and a lower (P<0.05) acetate:propionate ratio (1.35 vs. 1.87; P<0.05). Adding l-dopa to SB increased (P<0.01) gas production (92 ml/g DM vs. 200 ml/g DM), and total VFA concentration (132 mmol/l vs. 188 mmol/l), but reduced (P<0.05) gas production rate (0.08 ml/h vs. 0.05 ml/h). The concentration of l-dopa in fermented M and SBD decreased by 53 and 47%, respectively during fermentation. In conclusion, M was more fermented than SB and degradation of l-dopa during ruminal fermentation and microbial adaptation to l-dopa were confirmed. Adding l-dopa to SB did not impair ruminal fermentation.     

In sacco degradation kinetics of fresh and field-cured peanut (Arachis hypogaea L.) forage harvested at different maturities

There is interest in growing peanut (Arachis hypogaea L.) for forage, but little is known about the nutritive value and forage quality of modern cultivars. The objective of this study was to compare the chemical composition and in sacco degradation kinetics of three cultivars of peanuts (cv. ‘C99-R’, ‘Georgia-01R’, and ‘York’) at either stage 2 or 8 maturities when fresh and field-cured. Herbage yield was at least 3000 kg DM/ha for all cultivars at both maturities. Crude protein (CP) was greater (P < 0.0001) at R2 stage than at R8 stage; whereas, neutral detergent fiber (aNDF), acid detergent fiber, and Lignin (sa) were greater (P < 0.01) at R8 than R2 maturity stages. Water soluble carbohydrate and acid detergent insoluble nitrogen was not different (P > 0.07) among cultivars, maturity stage, or harvest forms. In vitro true digestibility was greatest (P < 0.02) for C99-R and least for York. Undegradable intake protein concentration was greatest (P < 0.04) in York and least for C99-R. Maturity had a greater effect on the degradation kinetics than harvest form or cultivar. The dry matter (DM) and CP in the soluble wash fraction (A) and insoluble but degradable fraction (B) and the effective ruminal degradability were greater among all cultivars and both harvest forms of the R2 maturity stage than the R8. The undegradable DM, aNDF, and CP in the undegradable fraction were greatest (P < 0.002) for all three cultivars at R8 maturity. The rate of degradation of DM and CP in the B fraction was faster (P < 0.001) at R2 stage than at R8 stage; whereas, rate of aNDF degradation was not different (P > 0.09) among treatments. Lag of DM, aNDF, or CP degradation was not different (P > 0.1) among treatments. The cultivars C99-R and Georgia-01R are recommended for further feeding trials.     

Effect of monensin on performance in growing ruminants reared under different environmental temperatures

To evaluate the effect of monensin on the performance of growing cattle under different environmental temperatures, 24 male calves (81.9 ± 7.7 kg mean weight and 100 days old) were distributed in a 2 × 2 factorial arrangement, contrasting 0 or 85 mg monensin/animal per day at 24.3 or 33.2 °C (environmental temperatures). Monensin supplementation increased weight gain (P=0.036), improved feed efficiency (P=0.040), increased ruminal concentrations of volatile fatty acids (VFA; P=0.003) and decreased the molar proportion of butyrate (P=0.034); all effects irrespective of environmental temperatures. A temperature-dependent monensin effect was detected on nitrogen retention (P=0.018) and N retained:N absorbed ratio (P=0.012). Animals fed monensin retained higher N amounts than those of the non-supplemented ones when the environmental temperature was 33.2 °C. Environmental temperature and monensin supplementation showed an interaction effect on urine N concentration (P=0.003). Temperature did not affect N excretion in monensin-fed animals, but increased N excretion in the non-supplemented ones. Monensin increased the crude protein (CP) digestibility (P=0.094) for animals at both temperatures. In conclusion, monensin changes the metabolism of the heat-stressed animals by increasing rumen VFA concentration, digestibility and protein retention, thus improving food use and weight gain.     

Effect of feed restriction or feeding high-fibre diet during the rearing period on body composition, serum parameters and productive performance of rabbit does

This study evaluated the effect of different feeding regimes from 11 weeks of age to first parturition on feed intake, leptin, non-esterified fatty acids (NEFA) and total protein serum levels, as well as productive performance in young rabbit does. In addition, body composition was estimated by bioimpedance analysis. Thirty-six 11-week-old does were randomly distributed in three groups. The AL-C group was fed ad libitum a control diet containing 350 g neutral detergent fibre (aNDFom)/kg, 11.6 MJ digestible energy (DE)/kg and 173 g crude protein (CP)/kg, and the does were inseminated at 16 weeks of age. The R-C group was fed 150 g/d of the same diet until 16 weeks of age, one week before artificial insemination (AI) at 17 weeks of age, and then fed ad libitum. The AL-F group was fed a diet containing 475 g aNDFom/kg, 9.4 MJ DE/kg and 174 g CP/kg ad libitum, and was inseminated at 17 weeks of age. During rearing (11-16 weeks), does in the R-C group had the lowest DE (1.54 MJ/d; P<0.003) and digestible protein (DP, 17.9 g/d; P<0.001) intake, as well as the lowest protein (172 g/kg; P<0.05) and energy (5.9 MJ/kg) body contents, leptin concentration at 16 weeks of age (2.48 ng/ml; P<0.001) and fertility (P<0.02) at first AI. Daily feed intake during pregnancy and lactation, as well as prolificacy and litter weight, were similar among groups. The highest percentage of body fat was observed for all the does when were inseminated for the first time (135 g/kg; P<0.001), consistent with the highest leptin (4.48 ng/ml; P<0.001) and total protein serum levels (6.87 g/dl; P<0.001) at this time. Serum NEFA level around parturition was higher (P<0.05) in groups AL-C and R-C (1.11 and 0.85 mmol/l) than in group AL-F (0.71 mmol/l), suggesting a lower lipid mobilization that tended to improve fertility rate for AL-F does on day 11 post-parturition (P<0.09). In conclusion, feed restriction during the rearing period delays reproductive development in young rabbits. In nulliparous does, ad libitum feeding during rearing with a high-fibre diet allows a similar productive performance to that of feeding with a less fibrous diet. Nevertheless, the use of high fibre diets during rearing does not affect feed intake throughout the first pregnancy and lactation.     

Effects of hybrid and maturity on performance and nutritive characteristics of forage maize at high latitudes, estimated using the gas production technique

We evaluated effects of hybrid and advancing plant maturity on performance, chemical composition, and nutritional characteristics of whole plant forage maize as well as the relative contributions of its plant fractions at high latitudes. Three maize hybrids, Avenir (FAO 180), Isberi (FAO 190) and Burli (FAO 210), were grown in southern Sweden in a field experiment with a replicated complete randomized block design. Plants were harvested four times during maturation, and dry matter (DM) yield and DM as a proportion of fresh weight were recorded. Whole plants were separated into four morphological fractions representing stems, leaves, kernels and cobs and the contribution of each fraction to the DM of the whole plant was estimated. Plant material was subjected to chemical analysis followed by measurement of in vitro gas production (GP) in buffered rumen fluid and finally, by calculation of in vitro true digestibility of organic matter (OM) and neutral detergent fibre (aNDFom). The GP profiles were fitted to a first order kinetic model with a discrete lag. Parameters describing the GP profiles were used in a recently developed mechanistic two compartment rumen degradation model to estimate in vivo OM digestibility (OMD) and first order rate of degradation in the rumen. Hybrids were compared and effects of maturity were assessed by analysis of variance using DM concentration as covariate. There were differences (P<0.05) among the hybrids in DM yield and relative contributions of the plant fractions. Differences (P<0.05) in modelled in vivo digestibility of OM and rates of degradation also occurred among hybrids. Increased maturity caused a reduction in in vitro digestibility of aNDFom in all plant fractions (P<0.05), but increased the rate of rumen degradation of OM in the whole plant as evaluated from GP results. The DM yield had a quadratic relationship with increasing maturity, with maximum yield at a DM concentration of about 370 g/kg. In vitro GP can describe the nutritive characteristics of forage maize in relation to advancing maturity and increased maturity affected agronomic performance and plant composition as well as the nutritive characteristics of hybrids.