Browsing by Author "Blair HT"
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- ItemAssociation of Single Nucleotide Polymorphism in the DGAT1 Gene with the Fatty Acid Composition of Cows Milked Once and Twice a Day(MDPI (Basel, Switzerland), 2023-03-21) Sanjayaranj I; MacGibbon AKH; Holroyd SE; Janssen PWM; Blair HT; Lopez-Villalobos NA single nucleotide polymorphism (SNP) rs109421300 of the diacylglycerol acyltransferase 1 (DGAT1) on bovine chromosome 14 is associated with fat yield, fat percentage, and protein percentage. This study aimed to investigate the effect of SNP rs109421300 on production traits and the fatty acid composition of milk from cows milked once a day (OAD) and twice a day (TAD) under New Zealand grazing conditions. Between September 2020 and March 2021, 232 cows from a OAD herd and 182 cows from a TAD herd were genotyped. The CC genotype of SNP rs109421300 was associated with significantly (p < 0.05) higher fat yield, fat percentage, and protein percentage, and lower milk and protein yields in both milking frequencies. The CC genotype was also associated with significantly (p < 0.05) higher proportions of C16:0 and C18:0, higher predicted solid fat content at 10 °C (SFC10), and lower proportions of C4:0 and C18:1 cis-9 in both milking frequencies. The association of SNP with fatty acids was similar in both milking frequencies, with differences in magnitudes. The SFC10 of cows milked OAD was lower than cows milked TAD for all three SNP genotypes suggesting the suitability of OAD milk for producing easily spreadable butter. These results demonstrate that selecting cows with the CC genotype is beneficial for New Zealand dairy farmers with the current payment system, however, this would likely result in less spreadable butter.
- ItemEffect of Breed on the Fatty Acid Composition of Milk from Dairy Cows Milked Once and Twice a Day in Different Stages of Lactation(MDPI (Basel, Switzerland), 2022-09) Sanjayaranj I; Lopez-Villalobos N; Blair HT; Janssen PWM; Holroyd SE; MacGibbon AKH; Ametaj BThe objective of this study was to evaluate the effect of breed on the overall composition and fatty acid composition of milk from cows milked once a day (OAD) and twice a day (TAD) in different stages of lactation. Milk samples were taken from 39 Holstein-Friesian (F), 27 Jersey (J), and 34 Holstein-Friesian × Jersey (F × J) crossbred cows from a OAD milking herd and 104 F and 83 F × J cows from a TAD milking herd in early (49 ± 15 days in milk), mid (129 ± 12 days in milk), and late (229 ± 13 days in milk) lactation. Calibration equations to predict the concentrations of individual fatty acids were developed using mid-infrared (MIR) spectroscopy. There was a significant interaction between breed within the milking frequency and stage of lactation for the production traits and composition traits. Holstein-Friesian cows milked OAD produced milk with lower concentrations of C18:0 in early and mid lactations compared to F × J and J cows. Holstein-Friesian cows milked TAD produced lower concentrations of C18:0 in early lactation and lower concentrations of C16:0 and C18:0 in late lactation compared to F × J. Lower concentrations of these fatty acids would reduce the hardness of the butter when the milk is processed. In the OAD milking herd, F cows were superior for daily milk yield compared to J cows, but Jersey cows produced significantly (p < 0.05) higher percentages of fat and a higher concentration of C18:0 fatty acid. The relative concentrations of C18:0 and C18 cis-9 in F and J cows milked OAD imply there is no breed effect on the activity of delta-9-desaturase, whereas stages of lactation likely have an effect. These results can be used to assist with selecting breeds and cows that are suitable for either OAD or TAD milking, allowing closer alignment with milk processing needs.
- ItemFatty Acid Composition of Dairy Milk: A Case Study Comparing Once- and Twice-a-Day Milking of Pasture-Fed Cows at Different Stages of Lactation(MDPI (Basel, Switzerland), 2022-03) Sanjayaranj I; Lopez-Villalobos N; Blair HT; Janssen PWM; Holroyd SE; MacGibbon AKHIn this case study, we compared the gross composition and fatty acid (FA) composition of milk from cows milked once a day (OAD) and twice a day (TAD) at different stages of lactation in real farm conditions with no control on feed. Seventy-two cows from a OAD milking herd and 181 cows from a TAD milking herd were sampled in early, mid and late lactation. Calibration equations were developed to enable the prediction of proportions of individual FAs using mid-infrared (MIR) spectroscopy. Cows milked OAD produced 25% lower daily milk yield (MY) compared to cows milked TAD. Percentages of fat and protein were 21% and 9% higher in cows milked OAD compared to cows milked TAD, respectively. The proportion of saturated fatty acids (SFA) (molecules with unbranched hydrocarbon chains and all single bonds) was significantly lower, while the proportions of de novo synthesised FAs from C8:0 to C14:0 were significantly higher, in cows milked OAD compared to cows milked TAD. OAD milking improved the energy balance of cows, which led to higher proportions of de novo synthesised FAs and lower proportions of long-chain fatty acids (16:0 and above). The proportion of SFA was significantly higher in mid lactation (ML) compared to early lactation (EL) and late lactation (LL) in cows milked OAD and TAD. In EL, the proportions of C4:0 to C12:0 FAs in cows milked OAD were significantly higher compared to the cows milked TAD due to the improved energy status of cows milked OAD. Understanding the proportions of individual FAs in cows milked OAD and TAD will enable further studies on milk fat characteristics and on butter hardness and coagulation properties of milk.
- ItemGenome-Wide Association Studies of Live Weight at First Breeding at Eight Months of Age and Pregnancy Status of Ewe Lambs(MDPI (Basel, Switzerland), 2023-03-27) Haslin E; Pettigrew EJ; Hickson RE; Kenyon PR; Gedye KR; Lopez-Villalobos N; Jayawardana JMDR; Morris ST; Blair HT; Ahmad SMThis study estimated genetic parameters and identified candidate genes associated with live weight, and the occurrence of pregnancy in 1327 Romney ewe lambs using genome-wide association studies. Phenotypic traits considered were the occurrence of pregnancy in ewe lambs and live weight at eight months of age. Genetic parameters were estimated, and genomic variation was assessed using 13,500 single-nucleotide polymorphic markers (SNPs). Ewe lamb live weight had medium genomic heritability and was positively genetically correlated with occurrence of pregnancy. This suggests that selection for heavier ewe lambs is possible and would likely improve the occurrence of pregnancy in ewe lambs. No SNPs were associated with the occurrence of pregnancy; however, three candidate genes were associated with ewe lamb live weight. Tenascin C (TNC), TNF superfamily member 8 (TNFSF8) and Collagen type XXVIII alpha 1 chain (COL28A1) are involved in extracellular matrix organization and regulation of cell fate in the immune system. TNC may be involved in ewe lamb growth, and therefore, could be of interest for selection of ewe lamb replacements. The association between ewe lamb live weight and TNFSF8 and COL28A1 is unclear. Further research is needed using a larger population to determine whether the genes identified can be used for genomic selection of replacement ewe lambs.
- ItemIncreased Dietary Protein to Energy Ratio in Pre-Weaning Lambs Increases Average Daily Gain and Cortical Bone Thickness in the Tibia(MDPI (Basel, Switzerland), 2022-12) Gibson MJ; Adams BR; Back PJ; Dittmer KE; Herath HMGP; Pain SJ; Kenyon PR; Morel PCH; Blair HT; Rogers CWThe objective of this study was to examine if diets differing in crude protein (CP) to metabolizable energy (ME) ratio (CP:ME) pre-weaning altered peripheral quantitative computed tomography (pQCT) measures of bone mass and strength in lambs. The left hind leg of lambs were available at the completion of a trial designed to examine the effect that altering the CP:ME ratio in milk replacer had on growth and body composition of pre-weaned lambs reared artificially. Treatments consisted of either normal commercial milk replacer (CMR, n = 10) containing 240 g/kg CP and 21.89 MJ/kg ME, high protein milk replacer (HPM, n = 9) containing CMR with additional milk protein concentrate to reach 478.7 g/kg CP and 19.15 MJ/kg ME or a mix of normal milk replacer and milk protein concentrate adjusted twice-weekly to match optimal CP:ME requirements (MB, n = 8) based on maintenance plus 300 g/d liveweight gain. At 22 kg live weight, lambs were euthanized and the tibia including the surrounding muscle was collected and scanned using pQCT at the mid-diaphysis. Lambs on the HPM and MB diets had a greater average daily gain (p < 0.01). There were limited differences in bone morphology and muscle mass, though notably the higher protein diets (MB and HPM) were associated with greater cortical thickness (p < 0.05) and, therefore, potentially greater peak bone mass at maturity This finding demonstrates that pre-weaning diets, and the protein content in particular, may influence the developmental potential of long bones and attainment of peak bone mass at maturity.
- ItemPredicting the Feed Intake of Artificially Reared Pre-Weaned Lambs from Faecal and Dietary Chemical Composition(MDPI (Basel, Switzerland), 2022-06) Anim-Jnr AS; Morel PCH; Kenyon PR; Blair HT; Leury BJPredicting feed intake in suckling lambs consuming both milk and pasture can be challenging, and thus intake values are often derived from solely milk or solid feed consumption. The present study investigated if dry matter (DM), organic matter (OM), and metabolisable energy (ME) intakes of lambs given a combination of milk and pellets under controlled conditions could be predicted with enough precision using dietary and faecal chemical composition. A total of 34 pre-weaned lambs bottle-fed milk replacer with or without access to pellets and kept in metabolic cages for four days were used. To develop the prediction equations, 54 faecal samples with detailed information on their chemical compositions, and the feed consumed by the lambs, were used. Pellet DMI was predicted from neutral detergent fibre concentration in faeces and pellets, pellets %DM, and live weight (LW) of lambs. Milk DMI was predicted from faecal Nitrogen concentration and LW. Milk and pellet DMI and their ME content were combined to predict DMI/d and ME intake/d. The equations developed were validated against 40 spot faecal samples randomly selected from the lambs. DM, OM, and ME intakes were predicted with high accuracy and precision. The results showed that the developed equations can be used with enough accuracy to predict ME, OM, and DM intakes in pre-weaned lambs ingesting milk and pellets concurrently, thus the results revealed that the established equations may be used to predict ME, OM, and DM intakes in pre-weaned lambs drinking milk and pellets at the same time, allowing feeding regimens for young lambs to be developed.