Influence of Cutting Date on Phenotypic Variation in Fatty Acid Concentrations of Perennial Ryegrass Genotypes from a Breeding Population

Breeding forages for increased fatty acid (FA) concentrations has the potential to improve the FA profile of ruminant products (meat and milk). Twenty perennial ryegrass genotypes from an ‘experimental’ breeding population and four genotypes from a ‘benchmark’ mapping population were used to assess genotypic variation in FAs across a growing season. Mean total FA (TFA) concentration for cuts 1 through 5 were 29.0, 31.7, 31.1, 34.4 and 42.0 g kg−1 DM, respectively. Six main individual FAs, namely palmitic acid (C16:0), trans-3-hexadecenoic acid (C16:1Δt3), stearic acid (C18:0), oleic acid (C18:1Δc9), linoleic acid (C18:2Δc9,12) and α-linolenic acid (C18:3Δc9,12,15), accounted for between 90% to 96% of TFA. Population means differed (p < 0.001) for TFA and all individual FAs, expect for C18:2Δc9,12 (p = 0.106). ‘Benchmark’ mapping population on average had 8-44% higher FA concentrations compared to the ‘experimental’ breeding population, except for C18:0 where the mapping population had lower concentrations. Individual genotypes from each population differed for all individual FAs and TFA (p < 0.05); with differences between the lowest and highest concentrations ranging from 8 to 23% amongst the mapping population genotypes and between 20 and 39% for the breeding population genotypes. Cutting date had a strong effect on population and genotype means (p <0.001) with an overall trend for FA concentrations to increase through the season. However, several significant population and genotype x cutting date interactions were also found highlighting the need for further investigations to strengthen our knowledge and understanding of how genetics and environment interact for this particular trait. Nevertheless, candidate ‘high-lipid’ genotypes were able to be identified using multivariate analysis which could be taken forward into a breeding program aimed at increasing forage FAs

Meat eating and nutritional quality of lambs sired by high and low muscle density rams

Intramuscular fat (IMF) content affects eating and nutritional quality of lamb meat. Muscle density measured by computer tomography is an in vivo proxy measure of IMF content that affects eating and nutritional quality of lamb meat. Lambs sired by high muscle density (HMD) or low muscle density (LMD) rams, selected for slaughter on commercial criteria were measured for meat quality and nutritional traits. A restricted maximum likelihood model was used to compare lamb traits. Additionally, regression analysis of sire estimated breeding value (EBV) for muscle density was performed for each meat quality trait. Muscle density EBV had a negative regression with IMF content (P < 0.001). For each unit increase in muscle density EBV, there was a significant decrease in loin (− 1.69 mg/100 g fresh weight) and topside IMF (− 0.03 mg/100 g fresh weight). Muscle density EBV had a negative regression with grouped saturated and monounsaturated fatty acids concentration (and monounsaturated proportion P < 0.001). Muscle density EBV had a negative regression with loin sensory traits tenderness, juiciness and overall liking and many novel tenderness sensory traits measured (P < 0.05). Selecting for LMD EBV increased IMF content and favourable meat eating quality traits. In contrast, sire muscle density EBV had a positive regression with loin polyunsaturated:saturated fat ratio and grouped polyunsaturated proportion traits (including total polyunsaturated proportion, total omega-6 (n-6) and total omega-3 (n-3) fatty acids (P < 0.001). This is explained by the fact that as sire muscle density EBV increases, polyunsaturated fatty acid proportion increases and the proportion of saturated and monounsaturated fatty acid content decreases. Muscle density EBV had a positive regression with shear force and the novel toughness sensory traits (P < 0.05). Selection for HMD EBV's increased shear force and toughness traits, which is unfavourable for the consumer. Low muscle density sired meat had higher meat colour traits chroma/saturation (+ 0.64, SD 2.30, P = 0.012), redness (+ 0.52, SD 1.91, P = 0.012) and yellowness (+ 0.31, SD 1.49, P = 0.08) compared to HMD sired meat. Selection for LMD could be used within a breeding programme to increase IMF content and enhance both meat colour and improve eating quality parameters

Biohydrogenation and digestion of long chain fatty acids in steers fed on Lolium perenne bred for elevated levels of water-soluble carbohydrate

Grass is a rich source of alpha-linolenic acid (18: 3n-3) and in this study the effects on ruminal fatty acid metabolism of feeding beef steers zero-grazed Lolium perenne containing elevated levels of water-soluble carbohydrate (WSC) were investigated. Eight Hereford x Friesian steers were offered ad libitum access to one of two varieties of Lolium perenne, Ba11353, high WSC (HS) or AberElan, intermediate WSC ( experimental control) harvested at different times of the day ( 14: 00 and 10: 00 h, respectively) to accentuate WSC differentials. The grass was zero-grazed and fed for 21 days, after which the animals were offered ad libitum grass silage for 14 days to provide a covariate intake. The dry matter ( 202 vs. 167 g per kg fresh weight), WSC( 243 vs. 161 g per kg DM), total fatty acids (21.4 vs. 17.9 g per kg DM) and proportion of 18: 3n-3 (0.54 vs. 0.43) were greater and fibre content was lower ( 251 vs. 296 g ADF per kg DM) for HS compared with the control. DM intake and intake of total fatty acids and 18: 3n-3 was higher for HS (9.3 vs. 6.7 kg per d; 201 vs. 117 and 108.5 vs. 51.3 g per d, respectively). There was a trend ( P <0.1) for the flow of 18: 3n-3 at the duodenal to be higher on HS (8.5 vs. 5.7 g per d) but surprisingly there was no significant difference in the flows of 18: 0 or 18: 1 trans (58.5 vs. 48.8 and 11.1 vs. 9.1 g per d, respectively). This may be attributed to the net flows of fatty acids across the rumen ( duodenal flow - intake) which were positive on the control and negative on the HS. Biohydrogenation of 18: 2n-6 and 18: 3n-3 was not different between treatments and averaged 79.9 and 90.5%, respectively. Intestinal absorption as a proportion of duodenal flow of all the fatty acids were high ranging from 0.70 for 12: 0 to 0.96 for 18: 1 trans. In conclusion, treatment HS a Lolium perenne bred for elevated levels of WSC had higher total fatty acids and a higher proportion of the beneficial fatty acid 18: 3n-3 compared to a control. The higher DM intakes achieved when feeding the treatment HS along with the greater content of 18: 3n-3 resulted in a trend for greater intakes of this fatty acid and flow to and absorption from the small intestine

What is the current significance of low birthweight pigs on commercial farms in Northern Ireland in terms of impaired growth and mortality?

Publication history: Accepted - 25 July 2020; Published - 31 July 2020.There is little modern data addressing the differential lifetime growth of commercially reared low and average birthweight pigs born into large litters (>14 piglets). As such, the main aim of this study was to quantify the lifetime growth and mortality rate of low and average birthweight pigs on commercial farms in Northern Ireland. It was also aimed to analyse the level, stage and cause of mortality within each birthweight category. A total of 328 low birthweight (LOW BW; 0.05). The alimentary tract (27%) and respiratory tract (27%) were the most commonly implicated body systems following post-mortem examination of post-weaning deaths. In conclusion, this study quantified the inferior weight, growth rate and mortality of Low BW pigs, identifying the lactation and immediate post-weaning periods as having greatest potential in reducing this birthweight associated growth differential