Biochemical aspects of energy utilisation in ruminants

The activities of acetyl-CoA hydrolase and acetyl-CoA synthetase and the influence of diet and feeding level on them were investigated in various ovine tissues and used to determine both the potential rate of substrate cycling between acetate and acetyl-CoA and the contribution of this cycle to energy expenditure in the ruminant. Two experiments, using lambs, were conducted in an attempt to further understand biochemical pathways which may influence the efficiency of utilisation of ME and explain why this is lower for fibre (sugarbeet pulp) when compared to starch (barley) based diets. The influence of carbohydrate source, feeding level and protein level on plasma concentrations of acetate, glucose and insulin and the rates of acetate incorporation into CC>2 and lipid were studied.ATP-stimulated acetyl-CoA hydrolase is present in rumen epithelium, muscle and the cytoplasm of ovine liver but not in perirenal adipose tissue, and it is not inactivated by cold. "Mitochondrial" acetyl-CoA hydrolase was detected in all tissues investigated. The activities of acetyl-CoA hydrolase and acetyl-CoA synthetase tended to be higher in perirenal adipose tissue of lambs fed on sugarbeet diets and their activities decreased with increasing level of feeding (P2 and lipid were influenced by acetate (P2 (P<0.05).A technique involving open column ion exchange chromatography, freeze drying and HPLC was developed for the concentration and separation of plasma organic acids. Organic acid recoveries were 43-69%.An experiment was conducted to investigate the activity of the substrate cycle between acetate and acetyl-CoA in calf liver in vivo. Several problems were encountered, notably huge variation in blood flows (including negative rates). This introduced large variation into the calculated fluxes and no meaningful conclusions were made.It was calculated from enzyme measurements made in vitro, that the substrate cycle in ovine liver may potentially account for 2.5% of basal heat production. It is suggested that the efficiency of utilisation of ME is related to glucose homeostasis, involving VFA and protein metabolism

Effects of chicory / ryegrass swards compared with ryegrass swards on the performance and carcass quality of grazing beef steers

An experiment investigated whether the inclusion of chicory (Cichorium intybus) in swards grazed by beef steers altered their performance, carcass characteristics or parasitism when compared to steers grazing perennial ryegrass (Lolium perenne). Triplicate 2-ha plots were established with a chicory/ryegrass mix or ryegrass control. Forty-eight Belgian Blue-cross steers were used in the first grazing season and a core group (n = 36) were retained for finishing in the second grazing season. The experiment comprised of a standardisation and measurement period. During standardisation, steers grazed a ryegrass/white clover pasture as one group. Animals were allocated to treatment on the basis of liveweight, body condition and faecal egg counts (FEC) determined 7 days prior to the measurement period. The measurement period ran from 25 May until 28 September 2010 and 12 April until 11 October 2011in the first and second grazing year. Steers were weighed every 14 days at pasture or 28 days during housing. In the first grazing year, faecal samples were collected for FEC and parasite cultures. At the end of the first grazing year, individual blood samples were taken to determine O. ostertagi antibody and plasma pepsinogen levels. During winter, animals were housed as one group and fed silage. In the second grazing year, steers were slaughtered when deemed to reach fat class 3. Data on steer performance showed no differences in daily live-weight gain which averaged 1.04 kg/day. The conformation, fat grade and killing out proportion of beef steers grazing chicory/ryegrass or ryegrass were not found to differ. No differences in FEC, O. ostertagi antibody or plasma pepsinogen levels of beef steers grazing either chicory/ryegrass or ryegrass were observed. Overall, there were no detrimental effects of including chicory in swards grazed by beef cattle on their performance, carcass characteristics or helminth parasitism, when compared with steers grazing ryegrass

Addressing global ruminant agricultural challenges through understanding the rumen microbiome::Past, present and future

The rumen is a complex ecosystem composed of anaerobic bacteria, protozoa, fungi, methanogenic archaea and phages. These microbes interact closely to breakdown plant material that cannot be digested by humans, whilst providing metabolic energy to the host and, in the case of archaea, producing methane. Consequently, ruminants produce meat and milk, which are rich in high-quality protein, vitamins and minerals, and therefore contribute to food security. As the world population is predicted to reach approximately 9.7 billion by 2050, an increase in ruminant production to satisfy global protein demand is necessary, despite limited land availability, and whilst ensuring environmental impact is minimized. Although challenging, these goals can be met, but depend on our understanding of the rumen microbiome. Attempts to manipulate the rumen microbiome to benefit global agricultural challenges have been ongoing for decades with limited success, mostly due to the lack of a detailed understanding of this microbiome and our limited ability to culture most of these microbes outside the rumen. The potential to manipulate the rumen microbiome and meet global livestock challenges through animal breeding and introduction of dietary interventions during early life have recently emerged as promising new technologies. Our inability to phenotype ruminants in a high-throughput manner has also hampered progress, although the recent increase in “omic” data may allow further development of mathematical models and rumen microbial gene biomarkers as proxies. Advances in computational tools, high-throughput sequencing technologies and cultivation-independent “omics” approaches continue to revolutionize our understanding of the rumen microbiome. This will ultimately provide the knowledge framework needed to solve current and future ruminant livestock challenges

Recent developments in altering the fatty acid composition of ruminant-derived foods

There is increasing evidence to indicate that nutrition is an important factor involved in the onset and development of several chronic human diseases including cancer, cardiovascular disease (CVD), type II diabetes and obesity. Clinical studies implicate excessive consumption of medium-chain saturated fatty acids (SFA) and trans-fatty acids (TFA) as risk factors for CVD, and in the aetiology of other chronic conditions. Ruminant-derived foods are significant sources of medium-chain SFA and TFA in the human diet, but also provide high-quality protein, essential micronutrients and several bioactive lipids. Altering the fatty acid composition of ruminant-derived foods offers the opportunity to align the consumption of fatty acids in human populations with public health policies without the need for substantial changes in eating habits. Replacing conserved forages with fresh grass or dietary plant oil and oilseed supplements can be used to lower medium-chain and total SFA content and increase cis-9 18:1, total conjugated linoleic acid (CLA), n-3 and n-6 polyunsaturated fatty acids (PUFA) to a variable extent in ruminant milk. However, inclusion of fish oil or marine algae in the ruminant diet results in marginal enrichment of 20- or 22-carbon PUFA in milk. Studies in growing ruminants have confirmed that the same nutritional strategies improve the balance of n-6/n-3 PUFA, and increase CLA and long-chain n-3 PUFA in ruminant meat, but the potential to lower medium-chain and total SFA is limited. Attempts to alter meat and milk fatty acid composition through changes in the diet fed to ruminants are often accompanied by several-fold increases in TFA concentrations. In extreme cases, the distribution of trans 18:1 and 18:2 isomers in ruminant foods may resemble that of partially hydrogenated plant oils. Changes in milk fat or muscle lipid composition in response to diet are now known to be accompanied by tissue-specific alterations in the expression of one or more lipogenic genes. Breed influences both milk and muscle fat content, although recent studies have confirmed the occurrence of genetic variability in transcript abundance and activity of enzymes involved in lipid synthesis and identified polymorphisms for several key lipogenic genes in lactating and growing cattle. Although nutrition is the major factor influencing the fatty acid composition of ruminant-derived foods, further progress can be expected through the use of genomic or marker-assisted selection to increase the frequency of favourable genotypes and the formulation of diets to exploit this genetic potential

Production and utilization of ensiled forages by beef cattle, dairy cows, pregnant ewes and finishing lambs - a review

This paper reviews the production of, and factors affecting the performance of dairy cows, beef cattle and sheep offered silage based diets in Ireland and UK. Digestibility is the most important factor influencing the feed value of grass silage and consequently animal performance. Each 10 g kg(-1) increase in digestive organic matter in the dry matter (DOMD) increases milk yield of dairy cows by 0.33 kg d(-1), carcass gain of beef cattle by 23.8 g d(-1), carcass gain of finishing lambs by 9.3 g d(-1), lamb birth weight by 52.3 g and ewe weight post lambing by 1.3 kg, respectively. Factors influencing feed value of grass silage are discussed including harvest date, wilting, fertilizer management, chop length and use of additives at ensiling. Maize silage increases the performance of cattle and sheep whilst whole crop wheat silage has no beneficial effect. Advances in silage technology, has enabled the ensiling high protein forages, such as red clover, lucerne and kale

Production and utilization of ensiled forages by beef cattle, dairy cows, pregnant ewes and finishing lambs - a review

This paper reviews the production of, and factors affecting the performance of dairy cows, beef cattle and sheep offered silage based diets in Ireland and UK. Digestibility is the most important factor influencing the feed value of grass silage and consequently animal performance. Each 10 g kg(-1) increase in digestive organic matter in the dry matter (DOMD) increases milk yield of dairy cows by 0.33 kg d(-1), carcass gain of beef cattle by 23.8 g d(-1), carcass gain of finishing lambs by 9.3 g d(-1), lamb birth weight by 52.3 g and ewe weight post lambing by 1.3 kg, respectively. Factors influencing feed value of grass silage are discussed including harvest date, wilting, fertilizer management, chop length and use of additives at ensiling. Maize silage increases the performance of cattle and sheep whilst whole crop wheat silage has no beneficial effect. Advances in silage technology, has enabled the ensiling high protein forages, such as red clover, lucerne and kale

Fishmeal supplementation of steers fed on grass silage: effects on rumen function, nutrient flow to and disappearance from the small intestine

International audienceFour Hereford Yen Friesian mature steers equipped with rumen, duodenal and ileal cannulas were fed on either grass silage alone (S) or silage supplemented with fishmeal (150 g$\cdot$kg$^{-1}$ silage dry matter intake; SFM) to assess effects on rumen fermentation, nutrient flow to and disappearance from the small intestine. The silage was a primary growth of perennial ryegrass with a total-N content of 24.5 g$\cdot$kg$^{-1}$ dry matter (DM). Ruminal concentrations of acetate, butyrate and ammonia-N were not different between treatments and averaged 51.7, 8.9 and 8.4 mmol$\cdot$l$^{-1}$, respectively. However, molar proportion of propionate was higher on SFM compared to S, 18.7 and 17.6 (SEM 0.18, $P < 0.05$), respectively. The amount and efficiency of microbial protein synthesis were not different between treatments and averaged 71.0 g$\cdot$d$^{-1}$ and 35.8 g N$\cdot$kg$^{-1}$ organic matter digested in the rumen, respectively. Fishmeal supplementation increased the flow of total-N ($P < 0.05$), non-ammonia-N ($P < 0.05$), and total amino acids ($P < 0.05$) at the duodenum. Amino acid disappearance was increased by fishmeal supplementation, 488 and 717 g$\cdot$d$^{-1}$ (SEM 28.6, $P < 0.05$) for S and SFM, respectively. The apparent absorption coefficient for the total amino acids from the small intestine [(expressed as duodenal - ileal)/duodenal] was also increased, 0.57 and 0.72 (SEM 0.028, $P < 0.06$) for S and SFM, respectively.Complémentation d'un ensilage d'herbe avec de la farine de poisson : effets sur la fermentation dans le rumen, le flux des nutriments et leur disparition dans l'intestin grêle chez des bœufs matures. Quatre bœufs matures Hereford $\times$ Frison munis de canules du rumen, du duodénum et de l'iléon ont été alimentés soit avec de l'ensilage d'herbe seul (S) ou de l'ensilage supplémenté par de la farine de poisson (à raison de 150 g$\cdot$kg$^{-1}$ de matière sèche d'ensilage ingéré ; SFM) pour évaluer les effets sur la fermentation dans le rumen, le flux des nutriments et leur disparition dans l'intestin grêle. L'ensilage était un ray-grass anglais récolté au 1$^{{\rm er}}$ cycle de végétation avec une teneur en azote total de 24,5 g$\cdot$kg$^{-1}$ de matière sèche. Les concentrations ruminales d'acétate, de butyrate et d'azote ammoniacal n'ont pas été différentes entre les traitements et ont été en moyenne de 51,7, 8,9 et 8,4 mmol$\cdot$l$^{-1}$, respectivement. En revanche, la proportion molaire de propionate a été plus élevée avec SFM comparé à S, respectivement, 18,7 et 17,6 (SEM 0,18, $P < 0,05$). Le flux d'azote microbien et l'efficacité de la synthèse protéique microbienne n'ont pas été différents entre les traitements et ont été, respectivement, en moyenne de 71,0 g$\cdot$j$^{-1}$ et 35,8 g N$\cdot$kg$^{-1}$ de matière organique digérée dans le rumen. La supplémentation en farine de poisson a augmenté le flux d'azote total ($P < 0,05$), d'azote non-ammoniacal ($P < 0,05$) et des acides aminés totaux ($P < 0,05$) au niveau du duodénum. La disparition des acides aminés a été augmentée lors de la supplémentation en farine de poisson, 488 et 717 g$\cdot$j$^{-1}$ (SEM 28,6, $P < 0,05$) pour S et SFM, respectivement. Le coefficient de digestibilité apparente des acides aminés totaux au niveau de l'intestin grêle [(exprimé par le rapport duodénal - iléal)/duodénal] a aussi été augmenté, 0,57 pour S et 0,72 pour SFM (SEM 0,028, $P < 0,06$)