Kikuyu over-sown with ryegrass and clover: dry matter production,botanical composition and nutritional value

The seasonality of growth and low nutritional value of kikuyu (Pennisetum clandestinum) pasture restrict milk production. The aim of the study was to determine the dry matter yield, botanical composition and nutritional value of irrigated kikuyu over-sown with annual ryegrass (Lolium multiflorum var. westerwoldicum), white clover (Trifolium repens) and red clover (T. pratense) or a mixture of perennial ryegrass (Lolium perenne) with white and red clovers under intensive grazing conditions with dairy cows. The incorporation of annual ryegrass, perennial clover or perennial ryegrass–clover into kikuyu pasture changed the seasonal fodder flow and increased the spring dry matter (DM) production. The over-sowing of kikuyu with annual ryegrass had no effect on the DM production of kikuyu during the summer and autumn. Kikuyu and kikuyu–ryegrass, fertilised with nitrogen fertiliser, had a higher DM production rate than kikuyu–clover pastures. Kikuyu–ryegrass pasture transformed from ryegrass-dominant in spring to kikuyu-dominant in summer and only kikuyu in autumn. This led to a decrease in metabolisable energy (ME) and increase in neutral detergent fibre (NDF) content of the pasture during spring, summer and autumn as kikuyu became more dominant. The clover content of kikuyu over-sown with clover decreased annually but was still higher than 30% at the end of two years after establishment. As the kikuyu content of the kikuyu–clover pastures increased, the seasonal growth rate changed from a low autumn growth (37.9 kg DM ha^?1 d^?1) in the first year to a higher autumn growth (48.5 kg DM ha^?1 d^?1) in the second year. The over-sowing of kikuyu with clover resulted in lower DM production and NDF values and higher crude protein (CP), ME and calcium (Ca) values. The lowest CP content in kikuyu–ryegrass pasture was during summer and autumn when kikuyu was dominant. The Ca content of the grass pastures (kikuyu and kikuyu–ryegrass) was low. The phosphorus (P) content of both the kikuyu–clover and grass pastures exceeded the requirement needed for dairy production (0.38%). The mean Ca:P ratio of the kikuyu–clover pasture meets the 1.6:1 ratio needed by dairy cows. The kikuyu and kikuyu–ryegrass pasture had a Ca:P ratio lower than 1:1 and Ca supplementation would be needed for dairy cows. The incorporation of annual ryegrass, perennial clover or perennial ryegrass–clover into kikuyu pasture improved the seasonal DM production and nutritional value of the pasture.     

四川阿坝县不同地区与不同海拔秋季牧草营养成分分析

摘要：为了给四川阿坝县反刍家畜的补饲和草地的合理利用提供科学依据,采取实地采样与实验室分析相结合的方法测定了四川阿坝县麦尔玛乡三大队牧场、麦昆乡草原村、贾柯河乡四大队和贾柯河牧场秋季（9月）牧草营养成分。结果表明,阿坝县秋季牧草粗蛋白质（CP)平均含量为10.30%,粗脂肪(EE)平均含量为2.92%,粗纤维（CF）平均含量为29.24%,粗灰分(Ash)平均含量为6.86%,中性洗涤纤维(NDF)平均含量为57.21%,酸性洗涤纤维(ADF)平均含量为35.47%,钙（Ca）平均含量为0.71 %、磷（P）平均含量为0.14%。不同地区秋季牧草CP、EE、CF、ADF、NDF、Ash和Ca的含量差异不显著（P>0.05）,P的含量差异显著（P<0.05）。把海拔3 400～3 800 m的采样区范围分成 3 400～3 500、3 500～3 600、3 700～3 800 m 3个层次,不同海拔牧草CP、EE、CF、ADF、NDF和Ash的含量差异不显著（P>0.05）,Ca和P的含量差异显著（P<0.05）。其营养成分适合阿坝县反刍动物的秋季放牧生产的要求,但不能以单纯放牧的形式来满足反刍动物的营养需求,需要补饲。     

肉用绵羊饲粮营养物质消化率和代谢能预测模型的研究

本试验旨在建立肉用绵羊饲粮营养物质消化率和代谢能(ME)的预测模型。选用66只体重为(45.0±2.0)kg的体况良好的杜泊×小尾寒羊F1代杂交肉用羯羊,随机分为11个处理,每个处理6个重复,每个重复1只羊。采用随机区组设计,分别测定11种不同粗饲料组成的饲粮的营养物质含量,通过物质代谢试验和气体代谢试验测定这11种饲粮的营养物质消化率、消化能(DE)及ME,在分析饲粮营养物质含量、可消化营养物质、DE和ME的基础上,筛选出最佳估测因子并建立估测方程。结果表明:饲粮干物质(DM)、有机物(OM)、粗蛋白质(CP)、总能(GE)消化率与饲粮中CP、GE和OM含量呈显著或极显著正相关(P0.05或P0.01),与中性洗涤纤维(NDF)含量呈显著负相关(P0.05);饲粮NDF消化率与饲粮中DM、OM、CP、GE含量达到显著或极显著负相关(P0.05或P0.01),与NDF含量达到极显著正相关(P0.01)。利用饲粮中营养物质含量对ME进行估测的最佳方程为ME=-49.593+0.594OM-0.107NDF(R2=0.949,P0.01)。由此得出,饲粮营养物质消化率、ME与营养物质含量均有较强的相关性,可通过营养物质含量对饲粮的营养物质消化率、ME进行合理估测。     

Nutrient digestibility and energy value of sheep rations differing in protein level, main protein source and non-forage fibre source

Two in vivo digestion trials were conducted to evaluate the effects of diet's crude protein (CP) level, N degradability, and non-forage fibre source (NFFS) on nutrient digestibility and energy value of sheep rations. In each trial, rams were fed four isocaloric and isofibrous rations, differing in main protein and/or NFFS source. At the first trial, mean CP/metabolizable energy (ME) ratio of the diets was 17 g/MJ ME and at the second trial, 13 g/MJ ME. At both trials, the first ration contained cotton seed cake (CSC) and wheat bran (WB), the second CSC and corn gluten feed (CGF), the third corn gluten meal (CGM) and WB and the fourth CGM and CGF. Data of both trials were analysed in common as 2 x 2 x 2 factorial experimental design. Low N degradability (CGM) had positive effect on CP, neutral detergent fibre (NDF) and acid detergent fibre (ADF) digestibility of the ration. Those results suggest that an increase in rumen undegradable protein (RUP) content does not negatively affect nutrient digestibility of sheep rations. Corn gluten feed significantly elevated crude fibre (CF) digestibility, in comparison with WB. Rations having high CP/ME ratio had higher digestibility of CP in comparison with those having low CP/ME ratio; the opposite was true for ether extract, CF, NDF and ADF digestibilities. CP level x N degradability interaction negatively affected energy value of the rations that had high CP level and high N degradability. Former suggest that when CP content is high then N degradability should be low otherwise ration's ME is negatively affected. CP digestibility and coefficient q of the rations containing WB and having high N degradability (N degradability x NFFS interaction) were the lowest suggesting that the combination of CSC and WB negatively affected CP digestibility and energy value of the ration. This could be explained by a reduced microbial CP synthesis, or lower RUP digestibility or both.     

Nonstructural carbohydrate supplementation of yearling heifers and range beef cows

A digestion study with 28 yearling heifers (428 +/- 9.9 kg; Exp. 1) and a 2-yr winter grazing trial with 60 crossbred cows (552 +/- 6.9 kg; Exp. 2) were used to determine the effects of level of nonstructural carbohydrate (NSC) supplementation on intake and digestibility of low-quality forage. Treatments were as follows: 1) control, no supplement; 2) 0.32 kg of NSC (1.8 kg/d of soybean hulls and soybean meal; DM basis); 3) 0.64 kg of NSC (1.7 kg/d of wheat middlings; DM basis); and 4) 0.96 kg of NSC (1.7 kg/d of barley and soybean meal; DM basis). Supplements provided 0.34 kg of CP/d and 5.1 Mcal of ME/d. In Exp. 1, heifers were individually fed hay (5.5% CP, DM basis) and their respective supplements in Calan gates for 28 d. Data were analyzed as a completely randomized design. In Exp. 2, cows were individually fed supplement on alternate days, and grazed a single rangeland pasture stocked at 1.8 ha/ animal unit month. Two ruminally cannulated cows were used per treatment to obtain forage extrusa and to measure in situ DM disappearance (DMD) and carboxymethylcellulase (CMCase) activity of particle-associated ruminal microbes. Data were analyzed as a completely randomized design with the effects of treatment, year, and their interaction. In both experiments, Cr2O3 boluses were used to determine fecal output, individual animal was the experimental unit, and contrasts were used to test linear and quadratic effects of NSC level and control vs. supplemented treatments. In Exp. 1, hay and diet DM, NDF, and CP intakes and digestibilities were increased (P < 0.01) by NSC supplementation compared with the control. In Exp. 2, 72-h in situ DMD and CMCase were decreased linearly (P < 0.08) with increasing NSC supplementation. Intake of forage DM, NDF, and CP was decreased linearly (P < 0.01) with increasing NSC supplementation during both years. Supplementation with NSC decreased (P = 0.01) cow BW loss compared with the control in yr 1, whereas in yr 2, cow BW loss was linearly increased (P = 0.03) by increasing NSC supplementation. Supplements containing NSC improved forage digestion and intake when heifers consumed forage deficient in CP relative to energy (digestible OM:CP > 7), but decreased forage digestion and intake when cows grazed forage with adequate CP relative to energy (digestible OM:CP < 7). Forage and supplement digestible OM:CP seemed to be superior predictors of response to supplementation with NSC compared with forage CP levels alone.     

Effect of partly replacing cottonseed cake with Mucuna spp. (var. Ghana) hay on feed intake and digestibility, milk yield and milk composition of zebu cows

The effect of partly replacing cottonseed cake with Mucuna hay (Mucuna spp. var. Ghana) on feed intake, digestibility and milk production of dairy cows was studied using six Zebu cows randomly assigned to three dietary treatments in a replicated Latin square design. All cows were fed hay from natural pastures ad libitum and 1.1 kg molasses as a basal diet, which was supplemented with: (1) 2 kg cottonseed cake (control diet), (2) 1.5 kg cottonseed cake and 1.2 kg Mucuna hay (low Mucuna, LM), and (3) 1.0 kg cottonseed cake and 3.3 kg Mucuna hay (high Mucuna, HM). Dry matter (DM) and crude protein (CP) intake were similar for all the diets. The addition of Mucuna significantly increased DM and organic matter digestibility, whereas CP, acid detergent fibre and neutral detergent fibre digestibility were similar among the diets. The treatments had no effect on daily milk yield (3.38, 3.43 and 3.38 kg milk) or milk composition (41.1, 43.7 and 42.7 g fat/kg milk; 35.1, 36.4 and 35.9 g protein/kg milk; and 46.1, 45.8 and 45.3 g lactose/kg milk, respectively, for cows fed control, LM and HM diets). The treatments had no significant effect on live weight changes. The results showed that replacing 50% of the cottonseed cake with Mucuna hay had no negative effects on feed intake and digestibility, milk yield or milk composition.     

Effect of cereal-based concentrates on productivity of Holstein–Friesian cows grazing short-rotation ryegrass (Lolium multiflorum) or kikuyu (Pennesitum clandestinum) pastures

In this study, the effect of increasing the proportion of concentrate in the diet, on efficiency of feed utilisation, was determined when Holstein–Friesian cows grazed short-rotation ryegrass (Lolium multiflorum) or kikuyu (Pennisetum clandestinum) pastures. The concentrates were energy-dense dairy pellets fed twice-a-day at milking and the roughage component was lucerne hay and the pasture.When cows grazed ryegrass, there was no effect on animal performance as the proportion of concentrate in the diet increased from 0.23 to 0.35 (4.75 to 7.50 kg concentrate/cow/day). The substitution rate of concentrates for pasture for the first 1.57 kg concentrate/cow/day fed was 0.58 but rose to 1.18 for the next 1.28 kg concentrate/cow/day.When cows grazed kikuyu, there was also no effect of increasing the proportion of concentrate in the diet on total dry matter intake (DMI) or milk production. However, there was a substantial increase in the in vivo digestibility of whole diet, pasture and acid detergent fibre (ADF) was observed when the proportion of concentrate in the diet increased from 0.08 to 0.25. However, there was a marked decline in pasture digestibility (72% to 64%), and more so in ADF digestibility (61.3% to 48.4%), as the proportion of concentrate in the diet increased further to 0.29 (5.52 kg/cow/day). The intake of kikuyu, when determined by difference between pre- and post-grazing pasture mass, was substantially underestimated compared to the use of the n-alkane technique, and this discrepancy increased as the pasture on offer increased.On both pasture types, the neutral detergent fibre intake, as a % of bodyweight varying from 1.6% to 2.2% for kikuyu and 1.5% to 1.6% for ryegrass was far above the values claimed of 1.2% to restrict intake.The results of this study highlight the limits to the amount of concentrate that can be fed on a typical Australian dairy farm where concentrates can only be fed twice-a-day at milking. The results also provide a more appropriate benchmark for fibre limitation in the ration when cows graze pasture, particularly poorer quality tropical grasses, and this value is well above that found in more intense feeding situations.     

Review of the relationship between nutrition and lameness in pasture-fed dairy cattle

Lameness of dairy cattle fed predominantly on pasture is increasingly recognised as one of the most costly disease conditions affecting dairy herds in New Zealand and Australia. Numerous risk factors are involved in the aetiology of claw lameness, including environment and factors associated with the conformation of individual cows. The role of nutrition requires further definition. Australasian pastures are characterised by low levels of fibre and effective fibre, rapid rates of fibre degradation, high water content, and high concentrations of rumen degradable protein during the autumn, winter and spring months. Relationships between high-quality vegetative pastures and ruminal acidosis may increase the risk of laminitis, particularly where pasture is supplemented with grains or other feeds containing significant amounts of starch. This article reviews the incidence, prevalence and pathophysiology of ruminal acidosis and laminitis and considers mechanisms by which acidosis may occur in pasture-fed cows. Techniques for diagnosing ruminal acidosis are reviewed, and practical strategies to avoid it are proposed. Currently, there is little information on the incidence and prevalence of ruminal acidosis and laminitis in pasture-fed cattle. The evidence gathered in this review suggests that ruminal acidosis and laminitis should be considered in the aetiology of lameness in pasture-fed dairy herds.     

Effects of herbage intake on goat performance in the mediterranean type natural pastures

This study aimed at identifying changes in natural pastures during the grazing season and investigating the effects of these changes on pasture feeding potential for high yielding dairy goats. During the study, 12 dairy goats were grazed on a 1.5 ha natural pasture for three months from April to June in 2003, 2004 and 2005. The goats were fed 0.5 kg/day of concentrate as a supplement during the grazing season. Botanical composition, herbage production and intake, crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of the pasture were determined. Live weight, milk yield, milk dry matter (DM) and fat content of the goats were monitored. The data were analyzed using a linear model, which evaluated the effects of grazing seasons in each year. Based on the three-year average, 87% of pasture was herbaceous plants and the remaining was shrubs in DM basis with Cistus creticus , Quercus ithaburensis , Pistacia atlantica and Asparagus acutifolius being the major shrub species. The herbage yield in June was significantly lower than in other months in all years ( P  = 0.001). In all experimental years, the CP content of the pasture decreased but the structural carbohydrates increased as the grazing season proceeded. While live weight was not affected by grazing periods except for 2004 ( P  = 0.001), milk yield significantly decreased with advancing grazing period ( P  = 0.001). The results of the present study indicate that natural pasture has a supportive effect in April and May on the milk yield of lactating goats which are in mid-lactation, and suggested that supplementary feeding is required in consecutive grazing periods.     

体外产气法评价青海高原燕麦青干草与天然牧草组合效应

本研究采用体外产气法评价了青海高原反刍家畜补饲用燕麦青干草分别与藏嵩草、金露梅+珠芽蓼、线叶嵩草3种天然牧草均按0∶100,25∶75,50∶50,75∶25,100∶0的比例两两组合后的发酵产气特性。结果表明,48 h产气量、理论最大产气量与NDS(P＜0.01)呈正相关关系,而与NDF(P＜0.01)、HC(P＜0.01)呈负相关关系;产气速率常数与HC(P＜0.01)呈负相关关系;产气延滞时间与ADF(P＜0.001)、NDF(P＜0.05)呈正相关关系,而与CP(P＜0.01)、NDS(P＜0.05)呈负相关关系。不同牧草组合在发酵12～24 h的正组合效应较高,且随着发酵时间的延长,各组合均呈组合效应量逐渐减弱的变化趋势;且以燕麦青干草作为补饲草进行该地区天然草地反刍家畜的冷季营养补饲时,燕麦青干草分别与藏嵩草、金露梅+珠芽蓼、线叶嵩草草地型牧草均以50∶50比例组合较为合适。因此,做好牧草间的科学搭配组合是提高青海高原天然草地冷季牧草利用率的有效途径之一。     

Effects of stage of maturity on ensiling characteristics and ruminal nutrient degradability of oat silage.

A study was conducted to determine the effects of stage of maturity on ensiling characteristics and ruminal nutrient degradability of oat silage. Oat was field grown and forage was harvested at the boot or soft dough stage and ensiled in mini-silos for 0, 2, 4, 8, 16 and 45 days. Two lactating Holstein cows fitted with ruminal fistulas were used determine ruminal nutrient degradability. Regardless of the stage of maturity, ensiled forages went through a rapid fermentation with a sharp decline in pH during the first 2 days of ensiling. Extensive proteolysis took place between 0 and 2 days as indicated by a reduction in true protein and neutral detergent insoluble protein (NDICP) and an increase in non-protein nitrogen (NPN). Chemical analysis of the 45 days silage showed that stage of maturity had no effect on neutral detergent fibre (NDF) and acid detergent fibre (ADF) of oat silage. However, oat harvested at the boot stage contained more crude protein (CP) and less starch than that harvested at the soft dough stage. Distribution of protein fractions showed that oat harvested at the boot stage contained lower NPN, NDICP and acid detergent insoluble protein than oat harvested at the soft dough stage. Results of the in situ incubation experiment indicated that oat harvested at the soft dough stage had lower ruminal dry matter (60.6 vs. 66.4%). CP (81.3 vs. 88.7%) and NDF (35.4 vs. 42.2%) degradabilities than oat harvested at the boot stage. It was concluded that chemical composition and ruminal nutrient degradability of oat silage are significantly influenced by stage of maturity.     

Feeding value of pastures for ruminants

Perennial ryegrass is the primary forage component of ruminant diets in New Zealand. It is persistent and palatable, and immature ryegrass has a high nutritive value (NV). However, seed-head development substantially lowers its feeding value (FV) as fibre concentration increases, the rate and extent of digestibility decreases, and voluntary intake declines. Ryegrass pastures are susceptible to accumulation of endophytic and saprophytic fungi in dead material at the base of the sward, especially when mature and laxly grazed. Feeding forage legumes to ruminants grazing grass-dominant pastures will improve animal performance and lessen the reliance on a single species to meet all nutritional requirements.

The FV of forage is a function of intake and NV, measured by chemical analyses and animal feeding trials. Performance of individual animals grazing forages is usually limited by energy intake because structural fibre can slow digestion and clearance from the rumen and because of competition between individuals for available feed. The use of metabolisable energy (ME) content of forage to signify FV can give a reasonable indication of animal performance, but it should be used in conjunction with chemical analyses to improve the accuracy of predictions.

The relationship between FV, pasture production, animal performance and profitability is complex. The importance of skilled management to maintain pasture quality and optimise animal performance under inconsistent climatic conditions should not be underestimated. Acceptable animal performance with minimal veterinary intervention requires good nutrition, but the genetic potential of livestock in New Zealand cannot be met solely by grazing pasture, especially when a high utilisation of pasture is required to maintain quality and profitability.

Producers are responding to industry demands to reduce the seasonality in supply of milk and meat by changing lambing and calving dates, and extending lactation length in dairy cows. Social changes include adoption of once-daily milking in the dairy industry. Some changes have necessitated increased use of supplements and others can be met by feeding forages with a higher FV than ryegrass, all of which require an improved knowledge of feed quality. This information is available through rapid and inexpensive near infrared spectroscopy (NIRS) analysis, enabling animal nutritional needs to be balanced by appropriate nutrient supply. It is essential that producers continue to improve animal welfare, limit excessive use of fertilisers and meet the demands of overseas consumers. Good nutrition, with an increased use of legumes and other forages to complement ryegrass pastures, will enable these objectives to be achieved.     

Feeding value of pastures for ruminants

Perennial ryegrass is the primary forage component of ruminant diets in New Zealand. It is persistent and palatable, and immature ryegrass has a high nutritive value (NV). However, seedhead development substantially lowers its feeding value (FV) as fibre concentration increases, the rate and extent of digestibility decreases, and voluntary intake declines. Ryegrass pastures are susceptible to accumulation of endophytic and saprophytic fungi in dead material at the base of the sward, especially when mature and laxly grazed. Feeding forage legumes to ruminants grazing grass-dominant pastures will improve animal performance and lessen the reliance on a single species to meet all nutritional requirements. The FV of forage is a function of intake and NV, measured by chemical analyses and animal feeding trials. Performance of individual animals grazing forages is usually limited by energy intake because structural fibre can slow digestion and clearance from the rumen and because of competition between individuals for available feed. The use of metabolisable energy (ME) content of forage to signify FV can give a reasonable indication of animal performance, but it should be used in conjunction with chemical analyses to improve the accuracy of predictions. The relationship between FV, pasture production, animal performance and profitability is complex. The importance of skilled management to maintain pasture quality and optimise animal performance under inconsistent climatic conditions should not be underestimated. Acceptable animal performance with minimal veterinary intervention requires good nutrition, but the genetic potential of livestock in New Zealand cannot be met solely by grazing pasture, especially when a high utilisation of pasture is required to maintain quality and profitability. Producers are responding to industry demands to reduce the seasonality in supply of milk and meat by changing lambing and calving dates, and extending lactation length in dairy cows. Social changes include adoption of once-daily milking in the dairy industry. Some changes have necessitated increased use of supplements and others can be met by feeding forages with a higher FV than ryegrass, all of which require an improved knowledge of feed quality. This information is available through rapid and inexpensive near infrared spectroscopy (NIRS) analysis, enabling animal nutritional needs to be balanced by appropriate nutrient supply. It is essential that producers continue to improve animal welfare, limit excessive use of fertilisers and meet the demands of overseas consumers. Good nutrition, with an increased use of legumes and other forages to complement ryegrass pastures, will enable these objectives to be achieved.     

三江源区不同季节放牧草场天然牧草营养价值评定及载畜量研究

为探究三江源区不同季节放牧草场天然牧草营养供给潜力和载畜量,选用3头安装永久性瘤胃瘘管的成年大通牦牛为瘤胃液供体动物,采用概略养分分析法和体外产气法,结合产草量对放牧草场牧草进行综合评定并确定其载畜量。结果表明,1)夏、秋及冬春放牧草场的可食风干草的最高产量分别为(123.83±17.88),(256.88±29.90)和(246.83±66.73) g/m²。2)夏、秋及冬春草场天然牧草的最高粗蛋白(CP)含量分别为(12.69±0.13)%,(10.54±1.22)%和(8.65±0.64)%,其含量随牧草生长而逐渐降低;夏、秋及冬春草场天然牧草EE的最高含量分别为(2.95±0.10)%,(4.38±0.17)%及(3.74±0.70)%;NDS含量的变化趋势与CP一致,而NDF和ADF含量的变化与CP相反,随牧草生长含量不断增加。3)体外发酵pH和氨氮浓度均在正常范围内;夏季草场牧草的48 h产气量、24 h产气估测消化能(DM)、代谢能(ME)和有机物质降解率(OMD)的最大值分别为(57.50±4.27) mL、(9.32±0.59) MJ/kg、(7.98±0.62) MJ/kg和(57.93±3.23)%;秋季草场牧草分别为(54.67±5.35) mL、(8.83±0.64) MJ/kg、(7.47±0.68) MJ/kg及(55.26±3.52)%;冬春草场牧草分别为(58.83±4.51) mL、(9.56±0.60) MJ/kg、(8.24±0.63) MJ/kg及(52.69±5.14)%。4)无补饲条件下,夏、秋及冬春天然放牧草场载畜量分别按数量载畜量、数量载畜量和DCP载畜量核算放牧科学,其最适载畜量分别为7.05,19.51和2.47 SU/hm²;有良好补饲情况下,夏、秋及冬春天然放牧草场载畜量按DCP载畜量、ME载畜量和ME载畜量核算放牧科学,其最适载畜量分别为14.85,29.00和5.03 SU/hm²。因此,三江源区牧草产量和品质季节性差异大,能-氮不平衡,通过补饲可以使夏、秋及冬春放牧草场的载畜量分别提高1.1,0.5和1.0倍左右,有利于促进当地畜牧业发展和生态保护。     

Analysis of the Relativity Between the Nutrient Content of Pasturage and the Relative Frequency of Feeding in Leizhou Goat Grazing on Natural Grassland

In order to understand the correlation between the grazing behavior of Leizhou goat and natural meadow nutrient content, the pasture behavior of Leizhou goats were tracked and recorded for 7 consecutive days, then the grass samples were collected according to the feeding conditions. The results showed that the relative feeding frequency of Pharbitis nil, Eleusine indica, Isachne globosa and Imperata cylindrica for Leizhou goats were 55.51%,28.70%, 8.13% and 1.18%,respectively.Among the determinated pastures, the contents of dry matter (DM)(P < 0.05),neutral detergent fiber (NDF)(P < 0.05) and acid detergent fiber (ADF) in Imperata cylindrica were the highest; Bidens pilosa had the highest contents of crude protein (CP)(P < 0.05),calcium (Ca)(P < 0.05),phosphorus (P)(P < 0.05), crude ash (ASH) and crude fat (EE);The crude fiber (CF) content in Isachne globosa was the highest. The correlation coefficient between the content of grass CP,CF,ADF,NDF,Ca as well as P and relative feeding frequency was 0.793(P < 0.05),-0.813(P < 0.05), -0.328(P > 0.05), -0.945(P < 0.01),0.804(P < 0.05),0.735(P < 0.05),respectively. In conclusion, there were significant positive correlation between the relative feeding frequency of Leizhou goats and the cotent of CP, Ca and P in native grass, and had a significant or extremely significant negtive correlation with CF and NDF content.     

A beef herd model for simulating feed intake, animal performance, and manure excretion in farm systems

A beef herd submodel was created for integration with other farm components to form a whole-farm model capable of simulating a wide range of beef production systems. This herd submodel determined the best available feed or feed mix to meet the fiber, energy, and protein requirements for each of up to six animal groups on the farm. The groups comprised any combination of cows, nursing calves, young heifers, yearling heifers, stockers, and finishing cattle. Protein, energy, and mineral requirements were determined for each group using the Cornell Net Carbohydrate and Protein System, Level 1. Diets were formulated to meet these requirements with available feeds, and the resulting feed intake, growth, and manure DM and nutrient (N, P, and K) excretions were predicted. Required feed characteristics included CP, ruminally degradable protein, acid detergent insoluble protein, NDF, P, and K concentrations. Feed intake was predicted by considering energy intake, potentially limited by fill, and exceeding a minimum roughage requirement. Fill and roughage limits were functions of feed NDF concentrations adjusted to consider particle size distribution and the relative rate of ruminal digestibility or the physical effectiveness of the fiber. The herd submodel was verified to predict feed intakes, nutrient requirements, diets, and manure excretions similar to those recommended or measured for beef animals. Incorporation of the beef herd submodel with other farm components, including crop growth (alfalfa, grass, corn, small grain, and soybean), harvest, storage, feeding, grazing, and manure handling, provided the Integrated Farm System Model. This comprehensive farm-simulation model is a useful research and teaching tool for evaluating and comparing the long-term performance, economics, and environmental impact of beef, dairy, and crop production systems.     

雷州山羊喜食牧草养分含量及其与相对采食频度相关性分析

为了解南方地区天然草场放牧雷州山羊牧食行为,以及天然牧草养分含量与其相对采食频度的相关性,连续7 d跟踪放牧观察记录雷州山羊牧食行为,并且根据雷州山羊采食情况采集牧草样本。试验结果表明,雷州山羊对于大花牵牛、牛筋草、柳叶箬和白茅的相对采食频度分别为55.51%、28.70%、8.13%和（P<0.05）1.18%;在测定的几种牧草中,白茅的干物质（DM）（P<0.05）、中性洗涤纤维（NDF）（P<0.05）和酸性洗涤纤维（ADF）最高,鬼针草的粗蛋白质（CP）（P < 0.05）、钙（Ca）（P < 0.05）、磷（P）（P < 0.05）、粗灰分（Ash）和粗脂肪（EE）最高,柳叶箬的粗纤维（CF）含量最高;雷州山羊的相对采食频度与牧草CP含量的相关系数为0.793（P < 0.05）,与CF含量的相关系数为-0.813（P < 0.05）,与ADF含量的相关系数为-0.328（P > 0.05）,与NDF含量的相关系数为-0.945（P < 0.01）,与Ca含量的相关性系数为0.804（P < 0.05）,与P含量的相关系数为0.735（P < 0.05）。综上可得,雷州山羊的相对采食频度与天然草场牧草中的CP、Ca和P含量具有显著的正相关关系;与CF、NDF含量具有显著或极显著的负相关关系。     

饲粮NDF/NFC对泌乳后期奶牛瘤胃甲烷排放量、营养物质表观消化率及生产性能的影响

为研究不同中性洗涤纤维/非纤维性碳水化合物(NDF/NFC)饲粮对泌乳后期奶牛甲烷排放量、营养物质消化率和生产性能的影响,试验选用体重(777.46±27.31)kg、胎次(1.5±0.15)胎、泌乳天数(242.92±15.28)d、产奶量(18.75±0.62)kg/d的奶牛12头,随机分配到3组,每组4头。各组饲粮NDF/NFC分别为2.10(精粗比为42:58)、1.96(精粗比为37:63)、1.52(精粗比为30:70),采用六氟化硫(SF_6)示踪技术测定自然状态下泌乳奶牛甲烷排放量。预试期14 d,正试期9 d。结果表明:饲喂不同NDF/NFC饲粮的泌乳后期奶牛甲烷排放量、甲烷能、单位干物质采食量的甲烷排放量以及单位总能摄入量的甲烷能均有显著差异;随着NDF/NFC降低,奶牛生产性能、饲料转化率和营养物质消化率无显著差异。综上,在不影响奶牛健康和生产性能的前提下,NDF/NFC为1.52的低NDF组饲料能显著降低泌乳后期奶牛瘤胃甲烷排放量。     

Nutrient digestibility and prediction of metabolizable energy in total mixed rations for ruminants.

The aim of the present study was to determine equations that predict ME in total mixed rations (TMR) based on routine methods. The ME content of 30 TMR for dairy cows was determined based on digestible crude nutrients obtained with wether sheep. Concentrations in the TMR (in g/kg DM) varied between 118 and 234 for crude protein, 26 and 48 for crude lipid, 131 and 250 for crude fibre, 281 and 488 for NDF, and 173 and 304 for ADF. Gas production ranged from 40.7 to 54.1 ml/200 mg DM, and enzymatically degraded organic matter from 652 to 800 g/kg DM. Digestibility [%] ranged from 68.6 to 84.0 for organic matter, from 55.6 to 84.3 for crude lipid, from 55.0 to 77.8 for crude fibre, from 57.6 to 77.0 for NDF and from 53.1 to 79.6 for ADF. ME ranged from 9.6 to 11.9 MJ/kg DM, and NEL from 5.7 to 7.4 MJ/kg DM. ME content was highly correlated with the concentration of both crude fibre and enzymatically degradable organic matter as well as with organic matter digestibility. A multiple regression equation based on crude fibre and crude lipid predicted ME with a reasonable goodness of fit (r2 = 0.81; s(y.x) = 2.4%). The inclusion of other nutrients, of neutral and acid detergent fibre, neither of gas production did improve the goodness of fit. The best prediction was achieved with inclusion of enzymatically degraded organic matter (r2 = 0.90; s(y.x) = 1.7%).     

Effects of application in spring of urea fertiliser on aspects of reproductive performance of pasture-fed dairy cows

AIMS: To assess if raising concentrations of crude protein (CP) in pasture in spring by the frequent application of urea fertiliser would affect ovarian follicular dynamics, luteal function, onset of oestrus and reproductive performance of dairy cows under farming conditions in New Zealand. METHODS: Spring-calved dairy cows were grazed for 101 days in paddocks that were either not fertilised (Control; n=20) during the course of the study, or were fertilised with 40-50 kg nitrogen (N)/ha every 4-6 weeks (High-N; n=20). Similar generous pasture allowances were offered to both groups. Concentrations of CP in pasture, urea in serum and progesterone in milk were measured. Ovarian follicular and luteal dynamics were determined using ultrasonography. Oestrous behaviour and the number, time and outcome of inseminations were also recorded. RESULTS: Mean concentrations of CP in pasture and urea in serum was higher in the High-N than the Control group (25.2 vs 21.6 and 8.3 vs 5.4 mmol/L for CP and urea, respectively; p<0.001). Intervals between calving and first oestrus, first insemination and conception, the time of first emergence of a dominant follicle, milk progesterone concentration, and the diameter of the corpus luteum (CL) in the first luteal phase did not differ significantly between groups. The interval from calving to first ovulation tended (p=0.10) to be lower and the diameter of the dominant follicle of the oestrous cycle at which cows conceived was greater (p=0.02) in Control than High-N cows. CONCLUSIONS: The use of large amounts of urea fertiliser during spring and the consequent increases in concentrations of CP in pasture and urea in serum did not negatively affect any of the parameters of reproductive performance of pasture-fed dairy cows that were assessed in this study.