Gwyddorau Biolegol, Amgylcheddol a Gwledig / Biological, Environmental & Rural Sciences

Protein supplementation of grass silages of differing digestibility for growing steers

2013-05-13T14:00:22Z

Protein supplementation of grass silages of differing digestibility for growing steers Scollan, Nigel D.; Sargeant, A.; McAllan, A. B.; Dhanoa, M. S. Previous studies have demonstrated that protein sources which are primarily degraded in the rumen such as rapeseed meal or soyabean meal may be as effective as a less rumen degradable protein source such as fishmeal in supporting higher levels of animal performance in young steers fed on grass silage. However, the response to type of protein supplement is likely to be influenced by the composition of the basal diet. This study has examined the effect of supplementing silages prepared from early (EH) and late (LH) harvested grass with two protein sources of differing rumen degradability, rapeseed meal (RSM) and fishmeal (FM) or a mixture of the two (M), thus creating eight experimental diets of LH, LHRSM, LHFM, LHM, EH, EHRSM, EHFM and EHM. Silage was offered ad libitum and supplements were included at 100 g fresh weight/kg silage DM intake. The RSM and M diets were made isonitrogenous with FM diets by the addition of urea. Animals remained on diets for 18 weeks and liveweights were monitored for a further 13 weeks while the animals were at pasture. Dry matter (DM) intakes and liveweight gains were higher with EH than with LH silage (P <0·001). Response to type of protein supplement was dependent on silage quality. On LH silage, higher intakes were noted on FM and M (82·4 and 82·8 g DM/unit metabolic liveweight/day, respectively) relative to silage only (75·8 g DM/unit metabolic liveweight/day) and this contributed towards higher liveweight gains (P <0·01). Liveweight gains tended to be higher on LH silage supplemented with FM compared to RSM (0·76 v. 0·67 kg/day, respectively, P = 0·08). In comparison, on EH silage, relative to EH unsupplemented, the intake was highest on M (89·2 v. 96·6 g DM/unit metabolic liveweight/day), but liveweight gains were not significantly different between supplements. On turnout to pasture, those animals fed on silage alone exhibited compensatory growth (P <0·025) with the result that those fed on LH silage only grew faster and achieved the same liveweight after 13 weeks at grass as those supplemented with RSM or M. There was a tendency for those fed on FM to maintain an advantage in liveweight after the period at pasture. On EH silage, at the end of the grazing period no significant differences in liveweight existed between the different supplements and on average were 23 kg heavier than EH silage unsupplemented. In conclusion, silage type (stage of harvest and quality) and protein supplementation influenced animal performance. On late harvest and poorer digestibility silage, there was some indication that feeding fishmeal was better than rapeseed but this was less evident on early harvest and higher digestibility silage. However, considering the price differential between these two supplements and small difference in animal performance it is concluded that rapeseed meal is as effective as fishmeal when used as a protein supplement for growing cattle fed on grass silage. Scollan, N. D., Sargeant, A., McAllan, A. B., Dhanoa, M. S. (2001). Protein supplementation of grass silages of differing digestibility for growing steers. Journal of Agricultural Science, 136, 89-98. Sponsorship: MAFF

Biohydrogenation and digestion of long chain fatty acids in steers fed on different sources of lipid

2013-05-13T14:00:01Z

Biohydrogenation and digestion of long chain fatty acids in steers fed on different sources of lipid Scollan, Nigel D.; Dhanoa, M. S.; Choi, Nag-Jin; Maeng, W. J.; Enser, Mike; Wood, J. D. Rumen biohydrogenation of dietary polyunsaturated fatty acids (PUFA) is a significant limitation on any attempt to manipulate the PUFA content of ruminant products (meat or milk). This study examined rumen biohydrogenation of PUFA, the effects of PUFA on other aspects of rumen metabolism and fatty acid flow to and digestion in the small intestine of steers fed on different sources of lipid. Animals were fed ad libitum on grass silage and one of four concentrates (60:40 forage:concentrate on a dry matter basis) containing differing sources of lipid: megalac (rich in C16:0; M), linseed (rich in C18:3n-3; L), fish oil (rich in C20:5n-3 and C22:6n-3; FO) and a mixture of linseed/fish oil (LFO). Diets were formulated so that total dietary oil intake was approximately 60 g/kg of the DM intake, approximately half of which was from the experimental test oil. Rumen NH3-N (P = 0·09) and total VFA concentrations (P = 0·007) were higher on L, FO and LFO compared to M. Dry matter intakes did not differ across treatments and averaged 7·2 kg/day. Intake and flow of fatty acids to the duodenum was 323, 438, 344 and 381 (S.E.M. 9·1; P <0·001) and 432, 489, 412 and 465 (S.E.M. 18·5; P <0·1) g/day for M, L, FO and LFO, respectively. Biohydrogenation of C18:1n-9 was lower than all the other unsaturated fatty acids and it was lower of FO and LFO compared to M and L, on average 66·1 and 72·2 %, respectively. Biohydrogenation of C18:2n-6 averaged 89·8 % across treatments and was lower (P <0·05) on M compared to L and FO. Biohydrogenation of C18:3n-3 averaged 92·1 % across treatments and was lowest on M (88·8 %) and highest on L and LFO (94·3 %). Biohydrogenation of C20:5n-3 and C22:6n-3 averaged approximately 91 and 89 % across the treatments, respectively. Small intestinal digestibilities of all fatty acids were high. In conclusion, feeding different sources of lipid with different fatty acid composition had significant effects on rumen function. The PUFA in whole linseed were only partially protected from biohydrogenation by the seed coat and in contrast to previous reports the C20 PUFA in fish oil were biohydrogenated to a large extent. Scollan, N. D., Dhanoa, M. S., Choi, N.-J., Maeng, W. J., Enser, M., Wood, J. D. (2001). Biohydrogenation and digestion of long chain fatty acids in steers fed on different sources of lipid. Journal of Agricultural Science, 136, (3), 345-355

Effect of a grass-based and a concentrate feeding system on meat quality characteristics and fatty acid composition of longissimus muscle in different cattle breeds

2013-05-13T13:59:25Z

Effect of a grass-based and a concentrate feeding system on meat quality characteristics and fatty acid composition of longissimus muscle in different cattle breeds Nuernberg, Karin; Dannenberger, Dirk; Nuernberg, Gerd; Ender, Klaus; Voigt, J.; Scollan, Nigel D.; Wood, J.; Nute, G.; Richardson, R. Ian The objective of this study was to examine the effects of feeding system and breed on the content of the beneficial n-3 polyunsaturated fatty acids and conjugated linoleic acids (CLA) in beef muscle. German Simmental (GS) (n=31) and German Holstein (GH) (n=33) bulls were produced on either an indoor concentrate system or a grass-based system consisting of a period of summer pasture feeding followed by a winter indoor period on grass silage and a concentrate containing linseed. All animals were slaughtered at 620 kg. The grass-based system increased (P Nuernberg, K., Dannenberger, D., Nuernberg, G., Ender, K., Voigt, J., Scollan, N. D., Wood, J., Nute, G., Richardson, I. (2005). Effect of a grass-based and a concentrate feeding system on meat quality characteristics and fatty acid composition of longissimus muscle in different cattle breeds. Livestock Production Science, 94,(1-2), 137-147. Sponsorship: European Commission (Research project QRLT-2000-31423).

Progress in breeding perennial clovers for temperate agriculture

2013-05-13T13:59:07Z

Progress in breeding perennial clovers for temperate agriculture Abberton, Michael T.; Marshall, Athole H. White clover (Trifolium repens L.) and red clover (T. pratense L.) are the most important legumes of temperate pastures. The former is used largely in systems based around sheep or cattle grazing and is grown together with a companion grass. Breeding aims to optimize the white clover contribution to the sward. This means that yield per se is not the aim but rather to take full advantage of the benefits of white clover; in particular, nitrogen fixation, high protein content, digestibility, mineral content and high intake. The objective is an agronomically and, as far as possible, nutritionally balanced sward, thus persistence of white clover and yield stability over a number of years are key goals. A considerable focus of germplasm improvement has therefore been overcoming biotic and abiotic stresses to clover performance. The former include not only pests and diseases but also the impact of the ruminant animal and the competitive interaction with the companion grass, while abiotic stress could be loosely defined as ‘winter hardiness’ and ‘summer survival’ depending on the site. In recent years the focus of many breeding efforts has shifted to give more consideration to the effects of variation within white clover germplasm on animal performance and the environment. Beneficial effects on productivity have been known for many years, but recent studies of the impact of forage diets on meat and milk quality have opened up new opportunities for improvement. Diffuse pollution of nitrogen and phosphorus from agricultural sources is high on the environmental protection agenda of many governments. Breeding efforts are now being made to reduce the contribution of clovers to both direct (leaching) and indirect (through animal returns) pollution. In particular, recent insights into mechanisms affecting protein breakdown in the rumen and silo offer new prospects for breeding interventions to reduce environmental impacts. Molecular marker methods are being developed in white clover and the transfer and use of resources and information accumulating in the model legumes Medicago truncatula and Lotus japonicus is likely to be a major route by which the power of genomic approaches is translated into forage legume improvement. Hybrids of white clover and related species have been developed to introgress key traits; namely, drought tolerance, grazing tolerance of large leaf types and enhanced seed yield, for which only limited genetic variation is present within the white clover gene pool. Red clover is less persistent than white clover, is typically cut three or more times in a season and is used to make silage for winter feed. Although it is often grown with a companion grass, monocultures are common and yield per se as well as persistency and pest and disease resistance are major breeding aims. Fewer agronomic studies and less germplasm improvement have been carried out in this species and molecular studies are not as well advanced although, as with white clover, future developments are likely to benefit greatly from a close relationship to model legumes. Red clover brings considerable benefits in terms of animal production and meat and milk quality. These aspects, alongside approaches to reduce nitrogenous pollution from the silo, represent considerable opportunities for variety development. Abberton, M. T., Marshall, A. H. (2005). Progress in breeding perennial clovers for temperate agriculture: centenary review. Journal of Agricultural Science, 143 (2-3), 117-135