title: Impact of adding nitrate or increasing the lipid content of two contrasting diets on blood methaemoglobin and performance of two breeds of finishing beef steers.
abstract: Adding nitrate to the diet or increasing the concentration of dietary lipid are effective strategies for reducing enteric methane emissions. This study investigated their effect on health and performance of finishing beef cattle. The experiment was a two×two×three factorial design comprising two breeds (CHX, crossbred Charolais; LU, Luing); two basal diets consisting of (g/kg dry matter (DM), forage to concentrate ratios) 520 : 480 (Mixed) or 84 : 916 (Concentrate); and three treatments: (i) control with rapeseed meal as the main protein source replaced with either (ii) calcium nitrate (18 g nitrate/kg diet DM) or (iii) rapeseed cake (RSC, increasing acid hydrolysed ether extract from 25 to 48 g/kg diet DM). Steers (n=84) were allocated to each of the six basal diet×treatments in equal numbers of each breed with feed offered ad libitum. Blood methaemoglobin (MetHb) concentrations (marker for nitrate poisoning) were monitored throughout the study in steers receiving nitrate. After dietary adaptation over 28 days, individual animal intake, performance and feed efficiency were recorded for a test period of 56 days. Blood MetHb concentrations were low and similar up to 14 g nitrate/kg diet DM but increased when nitrate increased to 18 g nitrate/kg diet DM (P0.05). Neither basal diet nor treatment affected carcass quality (P>0.05), but CHX steers achieved a greater killing out proportion (P<0.001) than LU steers. Thus, adding nitrate to the diet or increasing the level of dietary lipid through the use of cold-pressed RSC, did not adversely affect health or performance of finishing beef steers when used within the diets studied.
authors.affiliation: 1Beef and Sheep Research Centre,Future Farming Systems Group,SRUC,Kings Buildings,West Mains Road,Edinburgh,EH9 3JG,UK.
authors.forename: C-A
authors.initials: CA
authors.lastname: Duthie
authors.affiliation: 1Beef and Sheep Research Centre,Future Farming Systems Group,SRUC,Kings Buildings,West Mains Road,Edinburgh,EH9 3JG,UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Rooke
authors.affiliation: 1Beef and Sheep Research Centre,Future Farming Systems Group,SRUC,Kings Buildings,West Mains Road,Edinburgh,EH9 3JG,UK.
authors.forename: S
authors.initials: S
authors.lastname: Troy
authors.affiliation: 2Beef and Sheep Select,SAC Consulting Ltd.,SRUC,Kings Buildings,West Mains Road,Edinburgh,EH9 3JG,UK.
authors.forename: J J
authors.initials: JJ
authors.lastname: Hyslop
authors.affiliation: 1Beef and Sheep Research Centre,Future Farming Systems Group,SRUC,Kings Buildings,West Mains Road,Edinburgh,EH9 3JG,UK.
authors.forename: D W
authors.initials: DW
authors.lastname: Ross
authors.affiliation: 1Beef and Sheep Research Centre,Future Farming Systems Group,SRUC,Kings Buildings,West Mains Road,Edinburgh,EH9 3JG,UK.
authors.forename: A
authors.initials: A
authors.lastname: Waterhouse
authors.affiliation: 3Animal Breeding and Development,Animal and Veterinary Sciences Group,SRUC,Kings Buildings,West Mains Road,Edinburgh,EH9 3JG,UK.
authors.forename: R
authors.initials: R
authors.lastname: Roehe
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000822:Animal Husbandry; D000818:Animals; D029741:Brassica rapa / Q000737:chemistry*; D017610:Calcium Compounds / Q000378:metabolism*; D002417:Cattle / Q000235:genetics / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D050356:Lipid Metabolism; D008297:Male; D008706:Methemoglobin / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D000069466:Red Meat / Q000032:analysis
chemical_list: D017610:Calcium Compounds; D009566:Nitrates; D008706:Methemoglobin; C059948:calcium nitrate
keywords: beef cattle; lipid; methaemoglobin; nitrate; performance