Pasture Crude Protein Research Articles

Effect of pasture crude protein and fermentable energy supplementation on blood metabolite and progesterone concentrations and on embryo survival in heifers

AbstractSeasonal milk production systems rely on heavy inputs of nitrogenous fertilizer, which typically generate pastures with a high crude protein (CP) and low fermentable energy concentration. High intake of CP, particularly in association with low rumen fermentable energy, increases systemic ammonia and urea and has been associated with reduced fertility in cattle. The objective of this study was to examine the relationship between pasture protein intake and fermentable energy supplementation on a range of blood metabolites and on embryo survival and development in cattle.Oestrous synchronized, nulliparous beef heifers (no. = 175) were randomly assigned to one of four pasture-based dietary treatments in a 2✕2 factorial study carried out over 2 years. Animals were randomly allocated to either high (85 kg nitrogen (N) per ha; HN) or low (0·0 kg N per ha; LN) N fertilized pastures and within pasture treatment were randomly allocated to receive either zero or three (+3P) kg dry matter (DM) of molassed sugar-beet pulp (MSBP) per head per day as follows: (1) HN (no. = 44), (2) HN + 3P, (no. = 43), (3) LN (no. = 44), (4) LN + 3P (no. = 44). Blood samples were collected to measure systemic concentrations of ammonia, urea, insulin, glucose and progesterone. Heifers were artificially inseminated (AI) and pregnancy diagnosis was carried out by ultrasonography 30 days after AI. Subgroups of pregnant animals across treatments were slaughtered 40 days after AI to estimate conceptus development.The HN pasture had a higher CP (P< 0·001) and lower water-soluble carbohydrate (P< 0·01) concentration. Plasma concentrations of ammonia (P< 0·05) and urea (P< 0·001) were higher in the animals on the HN pastures and were reduced (P< 0·05) by MSBP supplementation, but only in animals on the HN pastures. Embryo survival rate across treatments was high overall (71%) and not related to pasture CP concentration, fermentable energy supplementation or systemic concentrations of ammonia, urea, glucose or insulin. There was no relationship between dietary treatment or systemic metabolites and any of the estimates of conceptus development. Systemic insulin was not affected by pasture N treatment or MSBP supplementation (P> 0·05). Systemic concentrations of glucose were not affected by pasture N treatment (P> 0·05) but were increased by MSBP supplementation (P< 0·05). Systemic progesterone was not affected by pasture CP or MSBP supplementation (P> 0·05) but at day 7 after AI was positively related (P< 0·05) to embryo survival. Intake of high CP herbage elevated systemic ammonia and urea but there was no association with embryo survival rate or embryo development in heifers.

Supplementing Pasture to Lactating Holsteins Fed a Total Mixed Ration Diet

Beginning in September 1997, a 6-week study was conducted to compare performance and income-over-feed cost of lactating Holsteins cows fed either a total mixed ration diet (TMR) only, compared to TMR in the afternoon and pasture in the morning, or TMR in the morning and pasture in the afternoon. Fifty-four Holstein cows in midlactation, averaging 28.1 kg/d of milk, were used in the study. Cows were on pasture for 8 h/d after either the p.m. or the a.m. milking. Predominantly orchardgrass with lesser amounts of white clover and Kentucky bluegrass were grazed. Pasture was sampled once per week, and weekly composites were analyzed. Compressed sward height and herbage dry matter (DM) yield were estimated once per week. Milk yield was electronically recorded and was sampled biweekly. Body condition score and body weight (BW) was recorded at the beginning and end of the study. Income-over-feed cost was calculated for each treatment. Compressed sward height and DM yield averaged 12.7cm and 1397kg/ha, respectively. Pasture crude protein, neutral detergent fiber, and acid detergent fiber averaged 27.0, 55.7, and 26.9%, respectively, and net energy-lactation was 1.65 Mcal/kg of dry matter. Milk production was greater for cows on the TMR treatment (29.1 vs. 28.2 and 27.6). No significant difference occurred in percentage of milk fat (3.54, 3.42, and 3.46%), or protein (3.28, 3.20, and 3.22%) for the above respective treatments. The SNF content (8.77 vs. 8.67 and 8.63%) was higher in TMR cows. While BW change did not differ among treatments (23, 32, and 22kg), body condition score change was greater in cows fed TMR only (0.14 vs. –0.06 and 0.01). As expected, TMR intake was greatest for cows fed TMR only and lowest for cows grazing after the p.m. milking (26.6 vs. 20.3 vs. 17.5 kg/ d dry matter). Income-over-feed cost differed between treatments and was approximately 18.6 and 7.5% higher for cows grazing high quality pasture during the afternoon and the morning, respectively, compared with cows on the TMR treatment.

Body condition at calving and the performance of dairy cows in early lactation under Australian conditions: a review

With the current increases in genetic merit and feeding occurring at farm level, dairy cows are under increasing nutritional stress in early lactation. Cows obtain their energy at this time from the feeds they eat and from body reserves. The relationship between body condition at calving and productivity of dairy cows has been reviewed, with particular emphasis on interactions between body condition and nutrition in early lactation. Recent research on the influence of body condition at calving on subsequent milk productivity, conducted mainly in the United Kingdom with complete diets fed indoors, has produced results in apparent conflict with the previous results from southern Australia and New Zealand where cows grazed pasture. In particular, the overseas research suggests considerably less advantage to improvements in body condition than had been previously thought. It is concluded that more information is needed concerning the interaction between body condition at calving and nutrition in early lactation, with dietary energy and protein both being important. There is a suggestion that, when complete diets are fed, it is better to achieve high energy concentrations in post-calving diets by the use of high-fibre concentrates with a fat supplement, rather than with high-starch concentrates. This has implications for dairying in Australia, since cereal grains are the major energy supplement used on many farms in early lactation and recent research has indicated that immediate marginal milk production responses to the use of concentrates may be poorer with fat cows than with thin cows. Reports from controlled feeding experiments indicate that fat cows need more dietary protein than thin cows and undegradable dietary protein might be of more concern than rumen degradable protein. However, in dairy systems where pasture is a considerable proportion of the diet, benefits of supplying specific undegradable dietary protein supplements still need to be established. Recent research has suggested that pasture appears to provide considerable quantities of undegradable dietary protein, even though the crude protein in pasture is potentially highly degradable in the rumen. Body condition at calving may also affect subsequent reproductive performance. This is due to its association with the degree of negative energy balance occurring in early lactation and because fat cows may be more susceptible to metabolic disease(s). While the mechanisms involved are probably quite complex, increases in animal productivity will generate more stress in cows at a time of their annual cycle when stress needs to be minimised. Further understanding is required to link the relevancy of overseas research to Australian dairy farming conditions where pasture is a key input.

Forage yield and crude protein of interseeded legume‐bermudagrass mixtures as affected by phosphorus fertilizer1

Bermudagrass (Cynodon dactylon L.) is a warm season perennial that is well adapted in the southern Great Plains. It is one of the region's most important forage crops used for livestock production, and is commonly grown without legume interseeding. Recent research has investigated ways of improving the quality and quantity of this forage. The objectives of this study were to determine the effect of interseeded legumes and phosphorus (P) fertilizer on bermudagrass pasture forage yield and crude protein content. One experiment was initiated in 1993 in eastern Oklahoma in an established bermudagrass pasture. Red clover (Trifolium pratense L.), ladino clover (Trifolium repens L.), and two varieties of alfalfa (Medicago sativah), ’alfagraze’ and'common’, were interseeded by hand into an established stand of bermudagrass. The effect of P on forage yield and crude protein was evaluated using a 30‐kg P ha‐1 rate applied at establishment versus no applied P. Forage yield was collected three times throughout the growing season each year from 1994 through 1997. When both alfalfa varieties were interseeded into a bermudagrass pasture without applying additional P fertilizer, forage yields for the legume‐grass mixtures decreased below those obtained from the monoculture bermudagrass in the first year of the stand. The alfalfa variety ‘alfagraze’ interseeded into established bermudagrass decreased total forage yield over the entire 4‐yr study. Interseeded red clover and ladino clover increased crude protein of the forage compared with monoculture bermudagrass the first two years of the study, with red clover continuing to increase crude protein in the fourth year. However, when 30 kg P ha‐1 was applied to the bermudagrass prior to establishment of the legumes, no change in yield or protein was observed for both alfalfa varieties’ interseeding treatments versus the unfertilized mixtures. Although forage yield may not be increased, interseeding legumes into established bermudagrass could provide an efficient way to improve pasture crude protein without the use of inorganic fertilizers. However, if alfalfa ('common’ or ‘alfagraze') is interseeded, additional P may need to be applied at legume establishment to prevent possible yield decreases.

Changes in the botanical composition and nutritive characteristics of pasture, and nutrient selection by dairy cows grazing rainfed pastures in western Victoria

Changes in pasture metabolisable energy (ME), crude protein (CP), neutral detergent fibre (NDF), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), sodium (Na) and chlorine (Cl) were measured at each grazing, in 4 paddocks on 2 farms (farm A and farm B) in western Victoria from May 1995 to March 1997. Selection differentials were calculated from quality parameters using measures of pre- and post-grazing masses. Changes in botanical composition and pasture allowance were also measured. The nutritive characteristics of pasture on both farms followed similar trends. Metabolisable energy and CP were highest in winter and early spring with values of over 11 MJ/kg DM and 250 g/kg DM respectively. The lowest concentrations of ME and CP in pasture on farm A (9.4 MJ/kg DM; 128 g/kg DM) were observed in April and February respectively. On farm B the corresponding lowest values (8.4 MJ/kg DM; 100 g/kg DM) were in March. In contrast, NDF values on farm A were lowest in June (466 g/kg DM) and on farm B (436 g/kg DM) in May, with highest values in February (648 g/kg DM) and March (692 g/kg DM) respectively. Concentrations of P, K, S and Cl in pasture followed a similar pattern to that of ME with highest values in winter and lowest in summer, while changes in Ca concentrations related more closely to changes in NDF. The concentrations of Mg and Na were highest in autumn and spring, respectively, with lowest values in late spring and summer. Selection differentials indicated that the ME of pasture consumed was 4–22% higher than the pasture on offer. For CP the range of selection differentials was always greater than 1, but varied widely (1.08–1.83). The selection differentials for NDF were always negative, with an average value of 0.84. Selection differentials for minerals varied little over the year, with values generally indicating a positive selection differential (P 1.12, 1.15; Ca 1.16, 1.16; Mg 1.15, 1.18; K 1.23, 1.27; Na 1.05, 1.07; Cl 1.16, 1.14; S 1.27, 1.28) for farms A and B. Pasture allowances ranged from 10–60 kg DM/cow.day and there was no relationship between selection differentials for all nutritive characteristics and pasture allowance. The results obtained in this study indicated that although the ME of pasture consumed throughout the year should be adequate to meet production of 30 L/cow.day in early lactation with minimal liveweight loss, it was associated with high levels of CP and potentially low concentrations of NDF in relation to cow requirements. Results therefore indicate a possible need for supplementing pasture diets in winter and spring to balance the diet for CP and NDF. In addition, it is likely that both Ca and Mg intake from pasture may be limiting in early lactation and therefore additional supplements of both minerals may be required during this period.

Effect of rate and time of nitrogen application from autumn to midwinter on perennial ryegrass - white clover dairy pastures in western Victoria. 2. Pasture nutritive value

Field experiments were carried out at 2 sites to study the effects of time and rate of nitrogen (N) application from autumn to midwinter on the nutritive value of perennial ryegrass–white clover dairy pastures in western Victoria. Nitrogen (0, 15, 25, 30, 45, and 60 kg/ha) was applied in mid-April, early May, mid-May, early June, and mid-June during 1996 onto a pasture which had been grazed and topped to a uniform height of 5 cm prior to imposition of treatments. Pasture samples to a height of 5 cm were collected when perennial ryegrass in the 45 kg N/ha treatment reached the 3-leaf stage of development. Samples were analysed for metabolisable energy (ME), crude protein (CP), neutral detergent fibre (NDF), and water-soluble carbohydrates (WSC). Increasing rates of N gave rise to a curvilinear (Site 1) and linear (Site 2) increase in pasture ME and CP content. The actual response of 0.007 MJ/kg DM. kg N at 45 kg N/ha was the same at both sites, regardless of N application time, and corresponded to an increase of 0.32 MJ/kg DM. At Site 1 the actual increase in CP content at 45 kg N/ha (0.067% per kg N applied) was the same for all application times and corresponded to an increase in CP content of 3%. For Site 2, the increase ranged from 0.040% (mid-April) to 0.098% (mid-May) per kg N, corresponding to a pasture CP content increase of 1.8 to 4.4% at 45 kg N/ha, respectively. The application of N gave rise to a curvilinear (Site 1) and linear (Site 2) decrease in pasture NDF. For Site 1 at 45 kg N/ha, the actual decrease ranged from –0.04% (early May) to –0.10% (mid-May) per kg N, corresponding to a pasture NDF content decrease of 1.69 to 4.61%, respectively. At Site 2, the actual decrease in NDF content (–0.04% per kg N applied) was the same for all application times and corresponded to a decrease of 1.58% at 45 kg N/ha. Apart from some exceptions, increasing rates of applied N gave rise to a linear (Sites 1 and 2) decrease in pasture WSC content. For Site 1, the change in pasture WSC content ranged from 0.007% (early May) to –0.032% (mid-June application) per kg N, corresponding to a change in pasture WSC content of 0.32 to –1.44% at 45 kg N/ha, respectively. At Site 2, the change in WSC content ranged from 0.0004% (mid-April) to –0.076% (mid-May) per kg N, corresponding to a change in pasture WSC content of 0.02 to –3.42% at 45 kg N/ha, respectively. In this study, N application had a positive effect on the nutritive value of dairy pastures in the autumn to midwinter, in western Victoria. This is particularly important for the provision of quality feed during this period as the majority of dairy herds in the region are calving at this time. Thus, the provision of an increased quantity of higher quality feed may lead to a reduction in the requirement for purchased feeds.

Spring and autumn nitrogen fertiliser effects, with and without phosphorus, potassium and sulphur, on dairy pastures: Pasture nutritive value and mineral content

Experiments were conducted at three sites to examine effects of applying different nitrogen (N) fertilisers at 45 kg N ha−1, with and without phosphorus (P), potassium (K) and sulphur (S) on dairy pasture nutritive value and mineral content in autumn and spring. Pasture nutritive value was assessed by measures of crude protein (CP), metabolisable energy (ME), water‐soluble carbohydrates (WSC) and neutral detergent fibre (NDF). Pasture mineral content was assessed by estimates of the major minerals phosphorus (P), potassium (K), sulphur (S), sodium (Na), calcium (Ca), and magnesium (Mg), and trace minerals manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn). Apart from some exceptions, applications of N, with and without additional P, K and S generally increased pasture CP and ME content in autumn and CP content in spring. Again with some exceptions, pasture WSC content was unaffected by fertiliser application in autumn, but was decreased by some treatments (containing N and N with P, K and S) in spring. Fertiliser treatments generally had no effect on pasture NDF content at Sites 1 and 3 during autumn and spring. At Site 2, some treatments (containing N and N with P, K and S) reduced pasture NDF content in autumn while during spring some treatments (containing N and N with P, K and S) increased pasture NDF content. Different N fertilisers applied at the same rate, with and without additional P, K and S, generally produced the same effect on pasture nutritive value. The application of P, K and S in the absence of N generally had no effect on pasture nutritive value. Apart from some exceptions, pasture P content was increased by fertiliser treatments including P, K and S, but N on its own did not influence pasture P content. Pasture K content was generally not influenced by treatment. At Site 1 during autumn and spring, and at Site 3 during spring, treatments containing P, K and S increased pasture S content while applications of N had no effect. At Site 2 during autumn, P, K and S increased pasture S content relative N only, while during spring pasture S content was generally increased by all treatments. At Site 3 during autumn, applications of N decreased pasture S content while P, K and S increased pasture S content relative to no fertiliser. Pasture Na and Ca content were generally not influenced by treatment. Pasture Mg content was not influenced by treatment at Sites 2 and 3. At Site 1 during autumn and spring, however, some treatments (containing N and N with P, K and S) increased pasture Mg content. Fertiliser treatments produced no consistent patterns or differences with respect to trace minerals (Mn, Fe, Cu and Zn).

Milk production from cows grazing on tropical grass pastures. 1. Effects of stocking rate and level of nitrogen fertilizer on the pasture and diet

A 3-year experiment was conducted at Kairi Research Station on the Atherton Tablelands, Queensland, to determine the effects of stocking rate and applied nitrogen fertilizer on the pasture yield and composition, diet selection by cows, and soil fertility of Gatton panic (Panicum maximum cv. Gatton) pastures. Thirty-two Friesian cows were used in a 4x2 factorial design: four stocking rates (2.0, 2.5, 3.0 and 3.5 cows/ha), each at two rates of fertilizer application 200 and 400 kg N/ha.year. The higher rate of fertilization increased the pasture green dry matter on offer at all samplings (P < 0.01); the increase ranged from 1 106 kg/ha in summer to 548 kg/ha in spring. Green dry matter decreased ( P< 0.0 1) with increasing stocking rate, with mean yields of 3736 and 2384 kg/ha at 2.0 and 3.5 cows/ha, respectively. Weed yields increased over the 3 years at the higher stocking rates for pastures receiving 200 kg N/ha.year. The crude protein content of leaf and stem increased with increasing stocking rate and amount of applied nitrogen fertilizer. Values ranged from 12.1 to 26.5% of dry matter (DM) in leaf and from 3.7 to 13.8% DM in stem. In leaf, sodium concentration (range 0.05-0.20% DM) was increased, while phosphorus concentration (range 0.21-0.44% DM) was decreased by the higher rate of fertilizer application. Plant sodium and phosphorus levels were inadequate for high levels of milk production. Dietary leaf content and crude protein contents were consistently increased by both a reduced stocking rate, and the higher rate of fertilization. Cows were able to select for leaf and at the lowest stocking rate, leaf in the diet averaged 38%; while the leaf content of the pasture was 20%. Dietary leaf content ranged from 38 to 57% in summer and from 11 to 36% in winter. Dietary crude protein ranged from 13 to 15% in summer and from 7 to 11% in winter and was positively correlated with pasture crude protein content and dietary leaf percentage. Soil pH decreased (P<0.05) from an overall mean of 6.3 in 1976 to 6.1 at 200 N and 5.8 at 400 N in 1979. Soil phosphorus status remained stable, while calcium and magnesium levels were lower (P<0.01) after 3 years.