Grass Intake Research Articles

Effects of wet soya waste supplementation on the intake, growth and reproduction of goats fed Napier grass

This study evaluated the effects of different levels of soya waste on the intake, growth rates, reproduction and feed conversion efficiency of adult goats, as well as the daily body weight (BW) gain of pre-weaning kids. Two experiments were conducted with Boer crossbred (Boer×local) and Jermasia goats. In experiment (Exp.) 1, 20 goats were divided into four groups (A, B, C and D), with five goats in each group. Groups A, B and C were given soya waste at a rate of 0.5, 1.0 and 2.0% of BW/day on a dry matter (DM) basis. Group D received soya waste ad libitum. In Exp. 2, 14 Jermasia does were split into a control group and a treatment group, with seven does in each group. The control group was fed pelleted compound feed at a rate of 2.0% of BW/day, and the treatment group was fed soya waste at a rate of 2.0% of BW/day. In both experiments, the animals were offered Napier grass ad libitum. In Exp. 1, with the increased dietary level of soya waste, the animals’ grass intake declined, but their intake of total DM and nutrients tended to increase. The intakes of DM, crude protein (CP) and metabolisable energy (ME) were higher (P<0.05) in Group C compared to Group A. The digestibility of DM and nutrients also tended to increase with the increased level of soya waste, and the digestibility of DM, organic matter, CP and neutral detergent fibre were higher (P<0.05) in Group C compared to Group A. The average daily BW gain increased (P<0.05) with the increased dietary level of soya waste. In Exp. 2, the DM and ME intakes of the does were the same in the control and treatment groups. However, the CP intake was higher (P<0.05) in the treatment group compared to the animals in the control group. The BW and reproductive performance of the does fed the treatment feed were similar (P>0.05) to those fed the control feed. The birth weight of the kids did not differ (P>0.05) between the control and treatment groups. However, the BW gain of the pre-weaning kids fed the treatment feed was higher (P<0.05) than that of the pre-weaning kids fed the control feed. Based on this 14-month long feeding study, high levels of soya waste (up to 2.0% DM of BW) did not have detrimental effects on the feed intake, weight gain and reproductive performance of goats, suggesting that soya waste supplementation is a viable replacement for scarce feedstuffs, such as grass, and expensive commercially produced compound feed.

Preference and behavior of lactating dairy cows given free access to pasture at two herbage masses and two distances.

A number of factors influence dairy cow preference to be indoors or at pasture. The study reported here investigated whether herbage mass and distance affects preference and if continuously housed cows exhibited behavioral and production differences compared to cows that had free access to pasture. Dairy cows (n = 16) were offered a free choice of being in cubicle housing (1.5 cubicles/cow) or at pasture with a high (3,000 ± 200 kg DM/ha) vs. low (1,800 ± 200 kg DM/ha) herbage mass. A control group (n = 16) was confined to cubicle housing for the duration of the study. Each herbage mass was offered at either a near (38 m) or far (254 m) distance in a 2 × 2 factorial crossover design to determine motivation to access pasture. Overall, dairy cows expressed a partial preference to be at pasture, spending 68.7% of their time at pasture. This was not affected (P > 0.05) by herbage mass. Both grass intake (P = 0.001) and grazing time (P = 0.039) was greater when cows were offered the high herbage mass. Neither total mixed ration intake (P > 0.05) nor milk yield (P > 0.05) was affected by herbage mass or distance. Additionally, no interaction existed between herbage mass and distance (P > 0.05). Distance affected preference: overall time on pasture was greater at the near distance (P = 0.002); however, nighttime use was not affected by distance (P = 0.184). Housed cows produced less milk than free-choice cows and this was potentially due to a combination of decreased lying time in housed cows (P < 0.001) and grass intake (1.22 kg/d) in free-choice cows. This study shows that herbage mass is not a major factor driving dairy cow preference for pasture, but distance does affect preference for pasture during the day. Additionally, there are clear production and welfare benefits for providing cows with a choice to be at pasture or cubicle housing over being continuously housed. Further research is necessary to quantify the effect of lying time on milk yields.

Trophic interactions between the native guanaco (Lama guanicoe) and the exotic donkey (Equus asinus) in the hyper-arid Monte desert (Ischigualasto Park, Argentina)

Exotic herbivores have detrimental effects on the ecosystems where they are introduced, at the level of plant communities and ecosystem processes. The native guanaco Lama guanicoe and the exotic feral donkey Equus asinus coexist in Ischigualasto Provincial Park. We quantified food availability in a plant community in the park during the wet and dry seasons, analyzed diet composition of both herbivores (by microhistological analysis of feces), and assessed the relationship between diet and plant availability and the overlap between donkey and guanaco diets. In both seasons, shrub species represented the most abundant cover type in the area, whereas grasses were the lowest plant cover during the wet season and almost non-existent in the dry season. The diet of the exotic donkey showed a high intake of grasses, and the trophic niche breadth did not change along the year. The guanaco’s diet was based on the most abundant food resources (shrubs), which constituted at least 60% of the diet; it was less diverse during the dry season. The diets of donkey and guanaco showed high overlap during the dry season. We can assume, at least during the dry season, the existence of a potential competition between guanaco and donkey, which may be higher if the donkey density increases.

Inhibition effects of volatile organic compounds from Artemisia frigida Willd. on the pasture grass intake by lambs

Plants release a wide spectrum of volatile organic compounds (VOCs) which can defense against herbivores. In previous studies, we found that VOCs from Artemisia frigida Willd. had strong allelopathic effects on local plants, which facilitated A. frigida dominance in heavily grazed and degraded grasslands. However, it is unknown whether these VOCs from A. frigida can affect the ingesting behavior of sheep. In this study, we analyzed the composition of VOCs from A. frigida grown in heavily grazed and degraded grasslands. The food intake, feeding time and feeding rate were determined after the lambs were supplied with local pasture grasses mixed with A. frigida shoots or sprayed with 1,8-cineole, β-pinene and α-terpineol, respectively. Terpenoids, which were the abundant compounds among A. frigida VOCs, mainly included 1,8-cineole, β-pinene, α-terpineol, m-cymene, camphor, ρ-menth-1-en-4-ol and β-terpineol. When local pasture grasses were mixed with A. frigida shoots, the food intake by lambs, according feeding time and feeding rate were inhibited markedly, with the inhibitory effect of 51.8%, 20.0% and 39.8%, respectively, in the treatment with 30% A. frigida. The inhibitory effects were also found in the treatments with 1,8-cineole, β-pinene and α-terpineol, in which 1,8-cineole had the strongest effects on the ingestion. These results showed that the VOCs (mainly terpenoids) can protect A. frigida from intake by sheep, which might also promote the plant to become the dominant species in heavily grazed and degraded grasslands. We suspected that the intense odor of terpenoids from A. frigida might influence pasture grass intake by sheep and even livestock production.

The energy expenditure of 2 Holstein cow strains in an organic grazing system

Until recently, measurements of energy expenditure (EE; herein defined as heat production) in respiration chambers did not account for the extra energy requirements of grazing dairy cows on pasture. As energy is first limiting in most pasture-based milk production systems, its efficient use is important. Therefore, the aim of the present study was to compare EE, which can be affected by differences in body weight (BW), body composition, grazing behavior, physical activity, and milk production level, in 2 Holstein cow strains. Twelve Swiss Holstein-Friesian (HCH; 616kg of BW) and 12 New Zealand Holstein-Friesian (HNZ; 570kg of BW) cows in the third stage of lactation were paired according to their stage of lactation and kept in a rotational, full-time grazing system without concentrate supplementation. After adaption, the daily milk yield, grass intake using the alkane double-indicator technique, nutrient digestibility, physical activity, and grazing behavior recorded by an automatic jaw movement recorder were investigated over 7d. Using the 13C bicarbonate dilution technique in combination with an automatic blood sampling system, EE based on measured carbon dioxide production was determined in 1 cow pair per day between 0800 to 1400h. The HCH were heavier and had a lower body condition score compared with HNZ, but the difference in BW was smaller compared with former studies. Milk production, grass intake, and nutrient digestibility did not differ between the 2 cow strains, but HCH grazed for a longer time during the 6-h measurement period and performed more grazing mastication compared with the HNZ. No difference was found between the 2 cow strains with regard to EE (291±15.6kJ) per kilogram of metabolic BW, mainly due to a high between-animal variation in EE. As efficiency and energy use are important in sustainable, pasture-based, organic milk production systems, the determining factors for EE, such as methodology, genetics, physical activity, grazing behavior, and pasture quality, should be investigated and quantified in more detail in future studies.

The effect of livestock production system and concentrate level on carcass traits and meat quality of foals slaughtered at 18 months of age

This trial was conducted to study the effect of livestock production system (freedom extensive system (FES) v. semi extensive system (SES)) and amount of finishing feed (1.5 v. 3.0 kg of commercial feed) in SES on carcass characteristics, meat quality and nutritional value of meat foal slaughtered at 18 months of age. For this study, a total of 49 foals (21 from FES and 28 from SES) were used. The obtained results showed that SES had a positive influence on carcass characteristic because these foals showed the best values for live weight, carcass weight, dressing percentage, perimeter of leg (PL) and carcass compactness index. On the other hand, finishing feeding also had a significant (P<0.05) effect on PL and lean thickness, as the highest values were obtained in foals finished with 3 kg of commercial fodder. The physico-chemical properties were significantly affected by the livestock production system with the exception of ashes content (P>0.05). Foals finished in SES increased in 408% the intramuscular fat content (0.23 v. 1.17%, for foals reared in FES and SES, respectively). On the other hand, L*-value and a*-value were significantly (P<0.01) affected by livestock production system, as foals from the FES group had a more intense redder color (higher CIE a*-value) and higher lightness (higher CIE L*-value) compared with those from the SES group. Finally, meat nutritional value was significantly affected by livestock production system, as foals from an extensive production system on wood pasture could be considered as healthier in relation to their fatty acid profiles (low n-6/n-3 ratio and high hypocholesterolemic/hypercholesterolemic ratio) as a result of the beneficial grass intake on meat fatty acid profile.

Estimation of grass intake on pasture for dairy cows using tightly and loosely mounted di- and tri-axial accelerometers combined with bite count

The aim of the present study was to investigate the use of accelerometer sensors to estimate grazing time. The estimated grazing time was furthermore combined with bite frequency data in order to model grass intake. Differing levels of stocking densities and grass height were used. Two field experiments were conducted: one in 2009 (EX1) using 20 Holstein cows with 7h daily grazing and ad libitum feeding inside, and another in 2010 (EX2) using 10 Holstein cows with 7.5h daily grazing and restricted feeding inside. For both experiments, data collected were (i) activity data measured by accelerometers, (ii) manually registered bite counts and (iii) estimation of grass intake from energy requirements. In EX2 the necessity of tight sensor fixation was tested. Head mounted accelerometers were used for estimation of grazing time, which was computed using threshold values of raw downloaded data from one axis.Loosely mounted sensors attached to and hanging from the neck collar, compared to tightly mounted sensors on the head of cows did not result in significantly different estimations of grazing time. Bite count recordings showed cow individual differences in bite frequency (ranging from 48 to 62bitesmin−1) for the same day on the same paddock. The best estimation of grass intake was for cows which were fed restricted indoors (≈30% of diet). This was modelled by using grazing time and bite frequency and resulted in prediction intervals ranging from ±1.2 to ±1.4kgDMcow−1day−1 for continuous grazing with an initial grass height of 11cm. Adding individual bite frequency per cow to the model together with the grazing time, reduced the intake prediction interval from an average of ±2.3kgDMcow−1day−1 to ±1.3kgDMcow−1day−1 in a continuous grazing system.

English

Timor deer ( Rusa timorensis ) is a wild native animal to Indonesia. The stags produce a high economic value of velvet antler (VA). This study was designed to evaluate the feed preference, nutrient consumption, age and morphometric of deer in relation to their velvet antler product (weigth and length) and quality (mineral and amino acids). Five stags with three ages classes were offered 3 combinations of 4 grasses in a captive area. Grasses were offered for 3 periods of 12 consecutive days during velvet antler growth period. Velvet antlers were harvested at 36 days old and analysed for their chemical content. The result showed that Timor deer had different preference to the grasses offered. Deer had a high preference on the combination of Pennisetum purpureum , Commelina benghalensis, Hierochloe horsfieldii, and Sorghum caudatum. High intake of grasses increased body weight. The regresion equation between the weight or length of velvet antler withage (year) and girth size (cm) were: Y (velvet antler weight)= 0.43 + 0.03 (age), r 2 = 0.99, P<0.05, and Y (length of velvet antler) = 5.7 + 0.31 (girth size), r 2 = 0.99, P<0.05. Aspartic acid, glutamic acid, and proline content of velvel antler were high in the older deer. The older deer having high girth size had the higher quality of velvet antler.

Effect of methionine supplementation on the growth performance of rabbit

The present study was conducted to evaluate the effect of different levels of methionine supplementation on feed intake, nutrient digestibility and growth performance of growing rabbit. Sixteen weaned crossbred New Zealand White (NZW) growing rabbits (30-35 d) were distributed into four treatment groups having four replications in each group using a Completely Randomized Design (CRD). Basal diet composed of green grass (dhal grass) and concentrate mixture which was offered ad libitum basis for 56 days period. Four levels of methionine such as 0.0% (control), 0.15%, 0.25%, and 0.35% were supplemented randomly to rabbits. Results showed that supplementation of methionine did not affect green grass intake. Cumulative as well as daily concentrate and DM intake were significantly (p&lt;0.05) higher for all methionine groups than control group. Final body weight gain as well as daily, weekly and cumulative body weight gains were improved significantly with increasing level of methionine. It was found that methionine had significant (p&lt;0.01) effect on digestibility of DM, CP, NFE and EE but CF digestibility did not differ significantly. Digestibility was improved with increasing the level of methionine. Feed conversion ratio also decreased significantly with methionine supplementation, and 0.25% methionine group showed the best performance among the four treatments. DOI: http://dx.doi.org/10.3329/bjas.v42i1.15777 Bang. J. Anim. Sci. 2013. 42 (1): 40 43

The effects of husbandry system on the grass intake and egg nutritive characteristics of laying hens

The aim of this study was to determine the effect of husbandry system and season on the grass intake and egg quality in laying hens considering that characteristics of organic eggs obtained in a system with no grass in the external area are similar conventional ones. Three hundred and sixty Ancona hens were randomly assigned to three groups: a control group (C), with the hens kept in cages under standard housing conditions; the organic group (O), with the hens kept under an organic production system (4 m² per hen) and the organic-plus group (OP), with the hens maintained under organic conditions but with a larger grass paddock availability (10 m² per hen). The estimated intake of forage, carotenoids and flavonoids of the OP hens was very high as the amounts deposited in eggs, mainly in the spring season. The fatty acid composition of the yolk was significantly affected by pasture. The OP eggs showed lower concentrations of polyunsaturated fatty acids (PUFA) n-6 and a higher percentage of PUFA n-3. The results showed that the grass intake was largely affected by the husbandry system and highlighted the seasonal effect of grass availability on the nutritional quality of eggs produced in organic systems.

The effects of additives in napier grass silages on chemical composition, feed intake, nutrient digestibility and rumen fermentation.

The effect of silage additives on ensiling characteristics and nutritive value of Napier grass (Pennisetum purpureum) silages was studied. Napier grass silages were made with no additive, fermented juice of epiphytic lactic acid bacteria (FJLB), molasses or cassava meal. The ensiling characteristics were determined by ensiling Napier grass silages in airtight plastic pouches for 2, 4, 7, 14, 21 and 45 d. The effect of Napier grass silages treated with these additives on voluntary feed intake, digestibility, rumen fermentation and microbial rumen fermentation was determined in 4 fistulated cows using 4×4 Latin square design. The pH value of the treated silages rapidly decreased, and reached to the lowest value within 7 d of the start of fermentation, as compared to the control. Lactic acid content of silages treated with FJLB was stable at 14 d of fermentation and constant until 45 d of ensiling. At 45 d of ensiling, neutral detergent fiber (NDF) and acid detergent fiber (ADF) of silage treated with cassava meal were significantly lower (p<0.05) than the others. In the feeding trial, the intake of silage increased (p<0.05) in the cow fed with the treated silage. Among the treatments, dry matter intake was the lowest in the silage treated with cassava meal. The organic matter, crude protein and NDF digestibility of the silage treated with molasses was higher than the silage without additive and the silage treated with FJLB. The rumen parameters: ruminal pH, ammonia-nitrogen (NH3-N), volatile fatty acid (VFA), blood urea nitrogen (BUN) and bacterial populations were not significantly different among the treatments. In conclusion, these studies confirmed that the applying of molasses improved fermentative quality, feed intake and digestibility of Napier grass.

Restricting grass intake

Clare Barfoot Nutritionist at SPILLERS explores the options

Comparison of intake and digestibility of fresh Digitaria decumbens grass fed to sheep, indoors or at pasture, at two different stages of regrowth

The effect of two feeding systems (indoors and at pasture) on intake and digestion of fresh grass was studied at two stages of regrowth (21 and 35 days of regrowth) in two parallel experiments. In Experiment 1, 10 adult Martinik rams weighing, on average, 50.5 (±0.9) kg, including four fitted with rumen cannula, were randomly allocated to two groups according to a 2 × 2 Latin Square design. These rams consumed a 21-day regrowth of Digitaria decumbens grass diet during two successive 28-day periods, indoors (five rams) or at pasture (five tethered rams). In Experiment 2, 10 other Martinik rams weighing, on average, 45.5 (±0.9) kg, including four fitted with rumen cannula, were randomly allocated to two groups according to a 2 × 2 Latin Square design. These rams consumed a 35-day regrowth of D. decumbens grass diet during two successive 28-day periods, either indoors (five rams) or at pasture (five tethered rams). For the indoors groups, in vivo organic matter digestibility (OMD) was measured by total collection of feces. In addition, OMD was estimated indoors and at pasture using the fecal CP (CPf) method (OMDCPf). Organic matter intake (OMI) was then estimated using OMDCPf and fecal organic matter output (OMICPf). Correlations of 0.49 and 0.77 were found between in vivo OMD and OMDCPf (P < 0.05) and between OMI and OMICPf (P < 0.001), respectively. OMDCPf was 1.8% (P < 0.05) and 2.7% (P < 0.01) lower indoors than at pasture at 21 and 35 days of regrowth, respectively, whereas OMICPf indoors was 1.1 and 1.16 times that registered at pasture at 21 and 35 days of regrowth, respectively. The higher OMDCPf at pasture was linked to the higher selective behavior of rams at pasture, whereas the differences in OMICPf between the two feeding systems were linked to differences in the total bulk density of the grass. These studies show that differences in OMDCPf and OMICPf exist between animals fed indoors and at pasture with the same forage and that these differences may vary according to the stage of regrowth of the grass offered.

Seasonal changes and muscle type effect on the nutritional quality of intramuscular fat in Mirandesa-PDO veal

The influence of slaughter season and muscle type on the detailed fatty acid composition, including conjugated linoleic acid isomers, and contents of total cholesterol and lipid-soluble antioxidant vitamins (α-tocopherol and β-carotene) in Mirandesa-PDO veal was assessed. Mirandesa purebred calves (n=29) were raised in a traditional production semi-extensive system, slaughtered in late spring (June) or early autumn (October) and the longissimus lumborum and semitendinosus muscles were sampled for analysis. Although the lipid composition of PDO veal was only slightly affected by the slaughter season, it was markedly changed by the muscle type. However, PDO veal had values of pasture-fed cattle for lipid grass intake indicators, in both seasons and muscles. From a human health standpoint, intramuscular fat in Mirandesa-PDO veal has a high nutritional value throughout the year, with favorable ratios of n−6/n−3 and contents of n−3 PUFA and α-tocopherol, as a result of the beneficial effects of grass feeding.

A herbivore's food landscape: seasonal dynamics and nutritional implications of diet selection by a red deer population in contrasting Alpine habitats

AbstractDietary constraints for large herbivores tend to be most strongly linked to quality of the forage available. In highly seasonal environments, such as mountain areas, both plant quality and available biomass may act as constraints. However, studies addressing the nutritional basis of diet selection of wild large herbivores under harsh conditions in sufficiently large spatial and temporal frameworks are scarce. We studied the functional importance of relative variability in plant quality and biomass for diet selection by a migratory population of Alpine red deer (Cervus elaphus) at the landscape scale and across an annual cycle. Botanical diet composition at plant group level did not show a particular ‘Alpine pattern’ but was similar to known patterns from lowland areas. Sources of variability were season, habitat (either open land or forest) and sex. Red deer foraged selectively in all seasons, and preferences for plant groups were negatively linked to plant abundances. Use and selection of plant groups were associated with high nutritional value (high crude protein and organic matter, low fibre), but partly also with high levels of active tannins. In the cold season, deer made strong nocturnal use of fertilized valley floor meadows offering high‐quality grass, but still showed some selection for tannin‐ and fibre‐rich coniferous browse, indicating a need for supplementing grass intake. Altogether, the nutritional value of the diet exceeded that of the forage available in the forested habitat, which was at or below the lower threshold for fulfilling metabolic needs of red deer. High‐quality grass on farmed meadows may thus be a critical source of food in mountainous areas during winter.

Tensile fracture properties of seven tropical grasses at different phenological stages

AbstractThe intake of forage grasses by grazing ruminants is closely related to the mechanical fracture properties of grasses. The relationship between the tensile fracture properties of grasses and foraging behaviour is of particular importance in tropical reproductive swards composed of both stems and leaves. This study (i) quantified and compared the tensile fracture properties of stems and leaves of seven tropical grass species and (ii) provided insight into the underlying plant traits that explain differences in fracture properties between species. Fracture force, tensile strength, fracture energy and toughness of stems (in various phenological stages) and leaves were measured and compared among five introduced tropical grasses (Cenchrus ciliaris, Chloris gayana, Digitaria milanjiana, Megathyrsus maximus (syn. Panicum maximum), Setaria sphacelata) and two native tropical grasses (Setaria surgens and Dichanthium sericeum). Species differed significantly in fracture force and fracture energy, with stems and leaves of C. ciliaris and S. surgens requiring less force and energy to fracture and stems and leaves of M. maximus and S. sphacelata requiring more force and energy to fracture in comparison with the other species. Differences in tensile strength and toughness were less pronounced. The differences among species in fracture force and energy mainly resulted from differences in cross‐sectional area of plant parts rather than from differences in tensile strength and toughness.

Sustainability evaluation of automatic and conventional milking systems on organic dairy farms in Denmark

Organic dairy farmers in Denmark currently are implementing automatic milking systems (AMS) to save labour costs. As organic agriculture aims at sustainable production, the introduction of a new technology such as AMS should be evaluated regarding its economic viability, environmental impact, and social acceptability, i.e., its contribution to sustainable development. The objective of this research, therefore, was to evaluate sustainability of AMS use on organic dairy farms in Denmark, by comparing results of a set of sustainability indicators for nine farms using AMS with nine farms using conventional milking systems (CMS). Sustainability indicators were quantified for economic performance of the farm, on-farm eutrophication, on-farm biodiversity, animal welfare (including health), grazing time, milk composition and labour time. Milk yield per cow per year was higher for AMS farms (9021kg energy corrected milk [ECM] per cow per year) than for CMS farms (7664kg ECM), but did not result in a higher net profit or gross margin per cow for AMS farms. Nitrogen surplus per hectare of available land was higher for AMS farms (110kgNha−1) than for CMS farms (66kgNha−1). This difference was not due to the use of AMS but was caused by a higher export of manure by the CMS farms. The number of veterinary treatments per cow per year was unaffected by AMS use, but culling rate was higher for the AMS farms (38%) than for the CMS farms (32%). There was no difference between the AMS and CMS farms in milk composition indicators such as somatic cell count, clostridium spores, and urea. The acid degree value (ADV), measuring free fatty acids (FFA) in the milk, was higher in the milk from the AMS farms (0.78meql−l) compared with the CMS farms (0.49meql−l). Labour time measured in hours of work per dairy cow per day, was only half for the AMS compared with the CMS users; i.e., 2.3min per cow per day. Grass intake by grazing as percentage of total feed intake was reduced by AMS (5.1kg DM per cow per day for the AMS farms against 6.8kg DM per cow per day for the CMS farms). From this quantification of selected sustainability indicators it can be concluded that organic dairy farms using AMS, in spite of the substantial decrease in grazing time, show the potential of economic and environmental sustainable development within the range of herd sizes investigated (65–157 cows per farm). Even though the lower number of grazing hours per cow per year on the AMS farms did not affect indicator scores for animal health or milk quality, this reduction in grazing hours might be a problem for consumers to accept AMS use.

Energetic efficiency of milk synthesis in dual-purpose cows grazing tropical pastures

The aim of this study was to assess the energetic efficiency of milk synthesis by grazing dual-purpose cows with or without a starch-based supplement in tropical South Mexico. Forty-six Holstein × Zebu cows were used in a 2 × 2 × 2 factorial design. Factors analysed were diet (supplemented, unsupplemented), age (young: 1-2 calvings, mature: >3 calvings) and day of lactation (21 and 84 days post-calving). The supplement represented about 30% of estimated dry matter (DM) intake. Grass intake was measured using the n-alkane technique at 21 and 84 days post-calving when calculations of efficiency were performed. Efficiency for milk synthesis was reported as feed conversion efficiency (FCE, kilograms of milk per kilogram of DM intake), gross energetic efficiency (GEE, milk energy output/metabolisable energy (ME) intake) and efficiency of ME use for lactation (k(l), adjusted to zero energy balance). There were no interactions between factors. FCE and GEE were not different between diets, but supplemented cows had a lower (p < 0.01) k(l) value (0.62) than unsupplemented cows (0.67), suggesting a diverted partition of nutrients towards body tissue. Mature cows were more efficient (p < 0.001) than young cows in terms of FCE (1.13 vs 0.87) and GEE (0.34 vs 0.26), but equal in terms of k(l) (0.65). FCE (1.10 vs 0.90) and GEE (0.34 vs 0.27) were both higher on day 21 compared with day 84 post-calving, with a trend for a higher k(l) in early lactation. Dual-purpose cows used tropical grasses efficiently for milk synthesis, and higher milk yield observed in supplemented cows was due to a higher intake of nutrients rather than a higher energetic efficiency.

Effect of supplementation with urea, blood meal, and rumen-protected methionine on growth performance of Holstein heifers grazing kikuyu pasture

Supplements with corn grain, molasses cane, and different nitrogen sources were evaluated in 16 growing Hosltein heifers [227 ± 33 kg body weight (BW)] grazing kikuyu (Pennisetum clandestinum) pasture in a 10-ha sward (rotational grazing with electric fences) during 90 days in the summer season. The nitrogen sources were urea (U); urea and blood meal (U+BM); and urea, blood meal, and rumen-protected methionine (U+BM +RPM). Heifers were randomly assigned to four experimental supplements defined as follows: control (no supplementation), U, U+BM, and U+BM +RPM. Two kilograms (as fed) of supplement was offered daily. The final BW of heifers fed U+BM +RPM was higher (P<0.05) than heifers not supplemented. The total and average daily weight gain of heifers supplemented with U+BM +RPM were higher than heifers not supplemented or supplemented with U and U+BM (P<0.05). The average daily gain of heifers supplemented with U and U+BM were higher than heifers not supplemented (P<0.05). Grass intake was not affected by supplementation, but total dry matter intake was increased by supplements with U, U+BM, and U+BM +RPM (P<0.05). Feed conversion was improved by U+BM +RPM (P<0.05). Total tract digestion was not affected by supplements. Blood urea nitrogen concentrations of heifers supplemented with U, U+BM, and U+BM +RPM were higher than heifers not supplemented (P<0.05). It is concluded that supplements with U+BM +RPM improved growth performance and feed conversion in heifers grazing kikuyu pasture.

Landscape-scale feeding patterns of African elephant inferred from carbon isotope analysis of feces

The African elephant (Loxodonta africana) is a large-bodied, generalist herbivore that eats both browse and grass. The proportions of browse and grass consumed are largely expected to reflect the relative availability of these resources. We investigated variations in browse (C(3) biomass) and grass (C(4)) intake of the African elephant across seasons and habitats by stable carbon isotope analysis of elephant feces collected from Kruger National Park, South Africa. The results reflect a shift in diet from higher C(4) grass intake during wet season months to more C(3) browse-dominated diets in the dry season. Seasonal trends were correlated with changes in rainfall and with nitrogen (%N) content of available grasses, supporting predictions that grass is favored when its availability and nutritional value increase. However, switches to dry season browsing were significantly smaller in woodland and grassland habitats where tree communities are dominated by mopane (Colophospermum mopane), suggesting that grasses were favored here even in the dry season. Regional differences in diet did not reflect differences in grass biomass, tree density, or canopy cover. There was a consistent relationship between %C(4) intake and tree species diversity, implying that extensive browsing is avoided in habitats characterized by low tree species diversity and strong dominance patterns, i.e., mopane-dominated habitats. Although mopane is known to be a preferred species, maintaining dietary diversity appears to be a constraint to elephants, which they can overcome by supplementing their diets with less abundant resources (dry season grass). Such variations in feeding behavior likely influence the degree of impact on plant communities and can therefore provide key information for managing elephants over large, spatially diverse, areas.