Edward H. Clayton

Context: Grazing cattle and sheep regularly suffer from feed shortfalls, which can be addressed by supplementary or drought feeding. Tools such as GrazFeed are often used in these circumstances. However, their use is mainly by consultants because they can be complex and time-consuming to use, thereby preventing their adoption by many producers. Aims: To develop a simple to use phone application for iOS and Android systems for producers to estimate pasture intake and calculate the amount of supplement required for different classes of livestock. Methods: The equations used to estimate pasture intake and animal feed requirements were adapted from the current Australian Feeding Standards for Ruminants and utilised in GrazFeed. A number of assumptions were made to simplify the inputs and complexity of calculations required. Equations were developed in the Microsoft Excel spreadsheet program and implemented by a commercial software developer. Validation and testing of the App was undertaken by user testing, comparison with existing models as well as against experimental data. Key results: The prediction of intake as a percentage of maintenance energy requirements (MEm) was lower for the drought and supplementary feed calculator (DASFC) than for GrazFeed at low pasture availability (below 3 cm and 1000 kg DM ha−1) and higher for the DASFC at high pasture availability (above 8 cm and 2667 kg DM ha−1). Using an independent dataset for sheep and cattle, the relationship between observed and predicted intake was higher for the DASFC (sheep r2 = 0.58, cattle r2 = 0.82) than for GrazFeed (sheep r2 = 0.33, cattle r2 = 0.49) and the correlation between intakes predicted by both models was high (sheep r2 = 0.94, cattle r2 = 0.75). Conclusions: The DASFC phone application required fewer inputs than many other models and predicted pasture intake and supplementation requirements equally well compared with other programs when compared with experimental data. Further developments are suggested to improve the accuracy and functionality of the App. Implications: The DASFC is used by producers to estimate supplementary feed requirements for sheep and cattle of different classes. The DASFC phone application enables producers to make their own informed decisions, thereby improving the efficiency of feed provision and reducing overall costs.

Context: The weight of sheep and cattle can be measured in a number of ways, including straight off feed (full or liveweight, LWt) or after an overnight fast from feed and water (curfew weight). The use of curfew weight to estimate weight and average daily gain (ADG) has been studied in cattle, however, the effect of different weight measures on ADG in sheep has not previously been reported. Aims: To determine whether weight or ADG of sheep grazing different forage treatments was influenced by using LWt or curfew weight for different time intervals between weight measures. Methods: Eighty lambs grazed four different forage crops for 42 days: cereal only, cereal + brassica, cereal + legume or cereal + brassica + legume. The weight of lambs was measured straight off pasture (LWt) and after a 16 h overnight fast from feed and water (curfew weight). The ADG of lambs was calculated from LWt and curfew weight for 2, 4- and 6-week time intervals. Key results: The correlation between LWt and curfew weight was significant (P < 0.001) at each weight measurement (r2 = 0.92, 0.89, 0.95 and 0.94 for Days 0, 14, 28 and 42 of grazing, respectively). Mean ADG was higher when LWt rather than curfew weight was assessed for Day 0–28 (320.6 vs 294.9 ± 6.48 g day−1) and Day 0–42 (288.8 vs 267.1 ± 5.28 g day−1). The relationship between ADG calculated from LWt and curfew weight was higher between Days 0 and 42 (r2 = 0.87) compared with Days 0–28 (r2 = 0.85) or 0–14 (r2 = 0.57). Conclusions: The positive relationship between LWt and curfew weight indicates that LWt can be used confidently for animal husbandry practices. However, when average daily gain data is required, particularly for research studies examining different feeding treatments, curfew weight should be used to minimise the error associated with gut fill and to more accurately reflect the magnitude of gain. Implications: The number of sheep required to estimate ADG in grazing studies is less when curfew weight rather than LWt is used. If using LWt, the time interval between weight measures should be at least 28 days.

Context: The fatty acid profile of pasture-fed beef and lamb, in particular, omega-3 fatty acids, depends largely on the fatty acids available in grazed forages. Annual forage crops are used to provide high-quality fodder for livestock during typical autumn–winter feed-gaps in the south-east of Australia; however, their fatty acid content and the influence of these on the fatty acid profile of grazing lambs have not previously been examined. Aims: To determine the fatty acid profile of mixtures of annual species fodder crops and the relationship with the omega-3 content of lamb plasma following grazing. Methods: In total, 96 Dorset × Border Leicester × Merino lambs (44.3 ± 0.55 kg) were allocated to one of four treatment groups (n = 24/treatment), including a single-species brassica (canola, Br) or mixed species containing brassica and cereal (canola, turnip, radish, wheat, cereal rye, B + C), brassica and legume (canola, turnip, radish, vetch, arrowleaf clover, B + L), or brassica, cereal and legume (B + C + L). Changes in the fatty acid profile of forages and plasma was determined over a 5-week grazing period. Key results: The n-6:n-3 ratio was higher in the Br control (0.386 ± 0.010) than in any other forage treatment (B + C = 0.351 ± 0.011, B + L = 0.345 ± 0.010, B + C + L = 0.354 ± 0.010). Plasma total n-3 was higher for lambs grazing the Br control than for those grazing any other forage, whereas the n-6:n-3 ratio was highest when lambs grazed B + C + L (1.41 ± 0.02), compared with any other forage treatment (Br = 1.31 ± 0.02, B + C = 1.18 ± 0.02, B + L = 1.28 ± 0.02). Conclusions: The higher n-6:n-3 ratio in lambs grazing the B + C + L forage mix was not expected, given the fatty acid profile of the forage grazed; however, selective grazing of vetch or brassica roots could have influenced the results. The relationship between forage fatty acid profile and fatty acid intake with changes in meat fatty acids and other physiological outcomes should be examined. Implications: The total omega-3 content of animal tissue may be increased by grazing canola; however, if a lower n-6:n-3 ratio is optimal in meat for human consumption, grazing forage mixtures containing cereals may be more beneficial.

Context: Annual forage crops are commonly used to provide high quality fodder for livestock in the south-east of Australia. While the agronomic benefits of some forage mixes such as cereals and peas have been studied, the animal production benefits of grazing mixtures of annual species forage crops compared with a single species cereal control have not been examined. Aims: To determine average daily gain (ADG), rumen pH and volatile fatty acids (VFAs) when sheep grazed mixtures of annual fodder crops compared with a single species cereal control. Methods: Eighty Border Leicester × Merino lambs (mean = 44.3 ± 0.55 kg) were allocated to one of four forage treatments (n = 20 per treatment) based on liveweight and fat score: a single species cereal control (wheat; C) or annual forage species mixes containing cereal (wheat, cereal rye) and brassica (canola, turnip, radish; C + B), cereal and legume (vetch, arrowleaf clover; C + L) or cereal, brassica and legume (C + B + L). Liveweight was assessed over a 42 day grazing period and rumen fluid parameters over 28 days. Key results: Mean ADG from day 0–42 was higher for lambs grazing the C control (298.9 ± 9.7 g head−1 day−1) compared with the C + B (251.4 ± 9.7 g head−1 day−1) or C + L (240.0 ± 9.7 g head−1 day−1) mixes, but not the C + B + L mix (275.8 ± 9.7 g head−1 day−1). Rumen fluid pH was lower (P < 0.001) for sheep grazing forage mixes containing brassica (C + B = 6.71 ± 0.07; C + B + L = 6.79 ± 0.07) compared with cereal alone (7.13 ± 0.07) or C + L (7.14 ± 0.07). Average daily gain was significantly (P < 0.001) predicted by rumen pH and estimated methane (CH4) output (ADG = 58.1 × Rumen pH − 99.0 × CH4 + 236.4, r2 = 0.80, Root Mean Squared Error of Prediction = 16.9). Conclusions: The higher ADG in the C and C + B + L compared with C + L forage treatments was related to higher dry matter on offer and lower estimated CH4 output. Further research should determine whether the lower pH observed when sheep grazed mixes containing brassica compared with cereals is associated with inefficient utilisation of energy from these forages. Implications: Average daily gain can be similar for mixed forage species compared with cereal alone. Higher rumen pH and more efficient fermentation reducing CH4 may improve growth.

Context: Omega-3 in pasture-fed beef and lamb is related to its availability in the forage species grazed. The variation in omega-3 content of several forages has been examined in the USA and UK, but not in south-eastern Australia across different stages of maturity. Aims: This study aimed to determine the change in omega-3, at different stages of plant development, in four species of forage commonly grazed by ruminants in south-eastern Australia. Methods: Four species, oats (Avena sativa L. cv. Eurabbie), annual ryegrass (Lolium perenne L. cv. Rambo), phalaris (Phalaris aquatica L. cv HoldfastGT) and subterranean clover (Trifolium subterrraneum L. cv. Coolamon) were grown in a replicated pot trial and harvested at seven stages of maturity corresponding to early vegetative, late vegetative, stem elongation, boot, anthesis, soft dough and ripening for oats, phalaris and ryegrass, or relative to day of flowering in clover. Proximate analysis and the concentration of fatty acids including C18:3n-3 and C18:2n-6 as well as the ratio of n-6:n-3 was determined. Key results: The mean (±s.e.) proportion of C18:3n-3 was highest in clover (50.6 ± 0.8), and higher in ryegrass (45.1 ± 0.5) and phalaris (44.0 ± 0.6) compared with oats (39.4 ± 0.5). Omega-3 proportion decreased with increasing maturity for oats (13.9 ± 0.86 vs 64.3 ± 0.68), ryegrass (17.3 ± 0.86 vs 68.2 ± 0.65) and phalaris (21.6 ± 1.63 vs 65.1 ± 0.79) but not to the same extent for sub clover (41.5 ± 1.38 vs 57.4 ± 0.79). The proportion of omega-3 was positively correlated with crude protein content. Conclusions: Omega-3 levels decreased in forages during development and was positively related to crude protein content, which is likely associated with total leaf chloroplasts. Although crude protein content remained higher for clover compared with other species, this did not translate to a higher proportion of omega-3 for any crude protein level. Implications: Grazing forages at earlier stages of maturity and maximising the amount of crude protein available for growth will increase the amount of omega-3 in plant material. The availability of this omega-3 for incorporation into meat and milk should be examined.

Context: Annual forage crops provide high-quality fodder for livestock during typical autumn and winter feed-gaps in the south-east of Australia and benefits through rotations in cropping systems. While benefits from intercropping with cereals and pasture or mixing canola and peas have been studied in Australia, the potential animal-production benefits of grazing mixed annual species forage crops have not been examined. Aims: To determine average daily gain (ADG) and rumen fluid parameters when sheep graze mixtures of annual fodder crops compared with a single species. Methods: Ninety six Dorset × Border Leicester × Merino lambs (mean = 44.3 ± 0.55 kg) were allocated to one of the following four treatment groups (n = 24/treatment) on the basis of sex and liveweight; a single species brassica control (canola) (Br) or annual forage species mixes containing brassica (canola, turnip, radish) and cereal (wheat, cereal rye) (B + C), brassica and legume (vetch, arrowleaf clove) (B + L) or brassica, cereal and legume (B + C + L). Liveweight and rumen fluid parameters were assessed prior to grazing and again 21 and 35 days after the commencement of grazing. Key results: Mean ADG from Day 0 to Day 21 was lower for female, but not male, lambs grazing the Br control (231 ± 23 g head−1 day−1) than for those grazing any forage mix (B + C = 292 ± 23 g head−1 day−1, B + L = 296 ± 23 g head−1 day−1, B + C + L = 310 ± 22 g head−1 day−1). Liveweight change over 35 days of grazing was not different between any forage mixtures. Rumen fluid pH was higher (P < 0.001) for sheep grazing forages containing cereals (B + C = 6.97 ± 0.06, B + C + L = 6.86 ± 0.06) than for those grazing brassica or legume (Br = 6.59 ± 0.06, B + L = 6.68 ± 0.06). Total volatile fatty acid concentration was lower and rumen pH was higher when sheep grazed B + C than when they grazed any other forage mix. Conclusions: The higher ADG in females grazing mixtures than in those grazing the Br was related to higher dry matter on offer. Further research should determine whether the lower pH observed when sheep grazed brassica and legume than when grazing mixes containing cereals is associated with subacute rumen acidosis and reduced fibre degradation and forage energy utilisation. Implications: Mixed forage species can provide higher DM on offer and ADG. Improved rumen efficiency could be related to improved growth.

Gas chromatography (GC) analysis of fatty acid methyl esters (FAME) typically uses long capillary columns (100 m or greater) which can be expensive and time consuming. The current study determined whether the major FAME of interest for human health in lamb and beef can be quantify using a 30 m compared with 120 m moderately polar capillary (BPX70) column. Lamb and beef samples were selected to cover a range of total intramuscular fat content and from either grass- or grain-fed animals. Results from the current study indicated that all major long-chain FAME of human health importance, including omega-3 polyunsaturated fatty acids (n-3PUFA), omega-6 polyunsaturated fatty acids (n-6PUFA) and conjugated linoleic acid (CLA) isomers, could be identified on the 30 m BPX70 column. The correlation (r²) for fatty acid proportions between columns for both lamb and beef was > 0.98 for all major n-3PUFA and > 0.86 for all major CLAs. When animals were fed a grain-based diet, C18:1n-7t (vaccenic acid) could not be resolved from C18:1n-8t when analysed on the 30 m column. The FAME profile of lamb and beef, particularly those important for nutritional composition tables, can be determined using a 30 m BPX70 column, thereby saving time and expense compared with longer columns. Particular care should be employed when analysing samples from sheep or cattle that are grain-fed due to co-eluting of C18:1n-8t.

Context: Plasma fatty acid profiles provide evidence of short-term feeding, while red blood cells (RBC) indicate longer-term feeding effects. Information on the rate of change in fatty acid profiles of sheep blood over time after alterations in diet is lacking. This study monitored the short- and longer-term effects of feeding grain-based diets to lambs on changes to omega-3 polyunsaturated fatty acids (PUFA) in blood fractions over 21 days. The data provide a guide to managing omega-3 PUFA availability for adequate tissue accretion of these fatty acids. Aims: To determine the rate of depletion over 21 days of omega-3 PUFA in the blood fractions of sheep fed on grain-based diets. Methods: Blood samples were taken from ewes taken off pasture and fed grain-based diets for 21 days. Fatty acid profiles in the blood plasma and RBC were used to monitor the rate of depletion of omega-3 PUFA. Key results: Immediate changes in plasma omega-3 PUFA concentrations occurred from the first day of grain feeding. The omega-3 PUFA content declined continuously on all five grains, but with substantial differences among them. RBC omega-3 PUFA contents displayed great variation across individual sheep but depletion was not significant. Conclusions: Plasma omega-3 PUFA depletion immediately on grain feeding indicated a lower availability for tissue accretion in growing sheep following short-term changes in diet. The lack of change in RBC omega-3 PUFA concentrations over 21 days indicated a differential accumulation of these fatty acids in this lipid depot compared with plasma, and changes in other tissues should also be examined. Implications: The effect of these short- and long-term changes on LCn-3PUFA accumulation in meat and reproductive tissues warrants further investigation.

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