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Item Pasture brome and perennial ryegrass characteristics that influence ewe lamb dietary preference during different seasons and periods of the day(Elsevier BV on behalf of the Animal Consortium, 2023-07) García-Favre J; Cranston LM; López IF; Poli CHEC; Donaghy DJ; Caram N; Kemp PDUnder the current scenario for climate change, Bromus valdivianus Phil. (Bv), a drought-resistant species, is an option to complement Lolium perenne L. (Lp) in temperate pastures. However, little is known about animal preference for Bv. A randomised complete block design was used to study ewe lamb's preference between Lp and Bv during morning and afternoon grazing sessions in winter, spring, and summer by assessing the animal behaviour and pasture morphological and chemical attributes. Ewe lambs showed a higher preference for Lp in the afternoon in winter (P < 0.05) and summer (P < 0.01), while no differences were found in spring (P > 0.05). In winter, Bv, relative to Lp, had both greater ADF and NDF (P < 0.001), and lower pasture height (P < 0.01) which negatively affected its preference. The lack of differences in spring were due to an increase in ADF concentration in Lp. In summer, ewe lambs showed the typical daily preference pattern, selecting Lp in the morning to ensure a greater quality and showing no preference during the afternoon to fill the rumen with higher fibre content. In addition, greater sheath weight per tiller in Bv could make it less desirable, as the decrease in bite rate in the species was likely due to a higher shear strength and lower pasture sward mass per bite which increased foraging time. These results provided evidence on how Bv characteristics influence ewe lamb's preference; but more research is needed on how this will affect preference for Lp and Bv in a mixed pastureItem The effects of leaf shear breaking load on the feeding value of perennial ryegrass for sheep : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 1992) Inoue, TatsushiReducing physical resistance has been thought to be a key factor to increase efficiency of masticatory breakdown of forage, which may lead to faster rumen fractional outflow rates (FOR) and consequently to increased voluntary feed intake and hence improved feeding value (FV). Two selections of perennial ryegrass (PRG) were selected for low (LS) and high leaf shear breaking load (HS) based on the maximum load required to shear across the leaf, i.e. leaf shear breaking load (LSBL). The series of experiments were conducted to investigate the effects of LSBL on the FV of PRG for sheep. LSBL, morphological and anatomical parameters were measured on the LS and HS PRG selections grown under the optimum climatic conditions. LSBL for the LS PRG selection was approximately 41 % lower the HS PRG selection. However, the LS selection had shorter leaf lengths, narrower leaf widths and narrower leaf cross-sectional area (CSA) than the HS selection. Therefore, in leaf shear strength (LSS), the LS selection was estimated to be approximately 27 % less resistant to shear than the HS selection per unit of CSA. The lower LSS in the LS selection is due to the lower concentration of sclerenchyma tissues in leaf CSA compared with the HS selection. However, the differences in the total shear load required to breakdown a unit dry weight of leaves to 1 x 1 mm·particle size, namely, leaf index of masticatory load (IML) between the selections were influenced by the differences in m orphological characteristics of leaves between the two PRG selections. Comparisons were made between the LS and HS PRG selections in the efficiency of mastication by sheep on particle breakdown. There were no major effects of reduced LSBL in PRG on the efficiency of mastication during eating and during rumination. Although the LS PRG selection was approximately 29 % lower in LSBL than the HS PRG selection, the difference for the two PRG selections in IML was almost nil. Effects of LSBL in PRG on rumen fractional outflow rate (FOR) and apparent digestibilities were investigated in sheep fed at restricted feed intake levels. There were no effects of reduced LSBL on FOR, although the LS PRG selection was approximately 39 and 12 % lower than the HS PRG selection in LSBL and IML, respectively. The digestibility of the cellulose fractions was approximately 16 % lower in the LS PRG selection than the HS PRG selection. The leaf morphology in PRO may affect the efficiency of fibre digestibility. Two field trials were conducted to test the hypothesis that LSBL in PRG improves FOR and leads to higher voluntary feed intake, and hence achieves improved live weight gain and wool production, namely FV. Although the LS PRG selection had 25-30 % lower LSBL than the HS PRG selection, live weight gain and wool production of sheep were not improved by reduced LSBL. FOR in sheep showed no indications of difference and voluntary feed intake was similar between the animals grazing the LS and HS PRO selections. The lack of difference in IML between the LS and HS PRG selection can be considered as a main reason for this. The hypothesis, that reduced LSBL in PRG would improve its FV, was therefore rejected. In conclusion, there were no major effects of reduced LSBL in PRG on efficiency of masticatory particle breakdown, and consequently, FOR, feed intake and hence FV in sheep. This is due to the lack of selection effect of PRG in IML. IML is a determining fac tor for the efficiency of mastication both during eating and rumination. The selection of PRG for a lower IML will, therefore, be necessary in I order to increase efficiency of masticatory particle breakdown, FOR and hence FV of PRG.Item Response of chicory (Cichorium intybus L.) to defoliation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, New Zealand(Massey University, 1997) Li, Guangdi; Li, GuangdiChicory (Cichorium intybus L.) is a perennial herb which has long been used as a forage crop. However, only recently has this species been re-evaluated in terms of its agronomy and animal performance. The objectives of this research were to study the persistence and the seasonal patterns of herbage mass accumulation and morphological development of forage chicory under defoliation. A series of field and glasshouse experiments were conducted at the Pasture and Crop Research Unit (PCRU), the Deer Research Unit (DRU) and the Plant Growth Unit (PGU), Massey University, Palmerston North, New Zealand (latitude 40°23'S) from 1993 to 1996. 'Grasslands Puna' chicory was used in all experiments except for one of the glasshouse experiments (Chapters 6 and 7) where two contrasting cultivars, 'PG90' and 'Orchies', were also included. Under grazing, Puna chicory accumulated herbage masses of 8.5, 9.4 and 4.6 t dry matter (DM)/ha from November to April, with average plant densities of 66, 69 and 24 plants/m2 and plant sizes of 2.9, 2.7 and 6.7 shoots/plant, for 1,2 and 4 year old stands, respectively (Chapters 3, 4 and 5). It was concluded that the characteristics of a grazed chicory crop that had deteriorated to the point of not being able to accumulate half of its maximum herbage mass were 25 plants/m2, six or more shoots/plant, or less than 150 shoots/m2. Defoliation stimulated the development of secondary shoots, but suppressed the growth of the primary shoot. Axillary shoots, however, developed fully regardless of whether or not plants were defoliated. The main source of feed from chicory for livestock was primary leaves during spring, and secondary and axillary leaves during summer and autumn (Chapters 4, 6 and 7). Results from both field and glasshouse experiments suggested that Puna chicory was more sensitive to defoliation frequency than intensity. It was concluded that defoliation at 50-100 mm in height at 3 week intervals in spring, and at 100-150 mm at 5 week intervals in summer and autumn, maximised the leaf formation and minimised the stem development of chicory. Grazing decreased the plant density of chicory regardless of grazing intensity or frequency, with the significant decrease in late spring and early summer when primary shoots were controlled (Chapters 3 and 4). Autumn grazing, especially hard grazing, was detrimental to plant persistence (Chapters 4). It was concluded that less grazing pressure through the growing season cannot be used to improve persistence without compromising leaf growth rate, but that avoidance of grazing in late autumn will improve the persistence of chicory. In a comparison of three cultivars, Orchies was the most persistent cultivar but had the slowest growth rate, and PG90 was the least persistent but with the highest growth rate, whereas the performance of Puna was intermediate, due to their contrasting root sizes and different root carbohydrate reserves. It was suggested that to improve the persistence and enhance the leaf production of Puna by plant breeding the emphasis should be on increasing taproot size without unduly prejudicing herbage mass accumulation.Item Methane emissions from ruminants fed white clover and perennial ryegrass forages : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2011) Hammond, Kirsty JoanRuminant enteric methane (CH4) emissions account for ~35% of New Zealand’s total greenhouse gas (GHG) emissions and a commitment has been made for their reduction. Previous research suggested lower CH4 yields (g/kg dry matter intake; DMI) from sheep fed white clover (Trifolium repens) compared to perennial ryegrass (Lolium perenne; ryegrass), and the initial focus was to account for that difference. However, measurements undertaken here showed little difference between diets in CH4 yield. The objective of this thesis was amended to better understand causes of variation in CH4 emissions from ruminants fed white clover and ryegrass forages. A database analysis showed greater variation in CH4 yield from sheep fed ryegrass forages with measured intakes using the SF6 technique, compared to respiration chambers (23.4 ± 5.70 vs. 23.1 ± 2.90 g/kg DMI). The composition of ryegrass fed to sheep predicted <2% and 20% of the variation in CH4 yield when derived from SF6 and respiration chamber techniques, respectively. For cattle, the database of CH4 yields determined by SF6 found ryegrass composition accounted for 13% of the variation. Measurements in respiration chambers of CH4 yield from sheep in three experiments reported here, had similar values for white clover and ryegrass (22.6 g/kg DMI), despite higher concentrations of fibre and less crude protein in ryegrass. Feed composition predicted less than 19% of variation in CH4 yield. Measurements of CH4 emissions from sheep fed white clover or ryegrass at multiples of 0.8 to 2.5 the metabolisable energy requirements for maintenance (MEm) showed a decline in CH4 yield of 3.47 g/kg DMI for each multiple of MEm intake above maintenance. Measurements of rumen function and digesta kinetics, suggested the rate of liquid flow through the gastro-intestinal tract, and molar percentages of propionate were the main drivers of a change in CH4 yield with intake. This research has shown minor effects of forage composition on CH4 yield, and has highlighted the importance of digestive function to account for effects of intake and individual variation on methanogenesis. The benefits of high feed intakes for production will be complemented by a low CH4 yield and low emissions per unit of production.Item The influence of diet and intake level on hepatic ammonia metabolism and ureagenesis by the ovine liver : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2001) Greaney, Kenneth BarryThe New Zealand agricultural industry is based on the efficient utilisation of fresh forages, a characteristic of which is a high soluble protein content. A large proportion of the ingested protein is highly soluble in the rumen. A significant proportion of the ingested N is removed from the rumen as ammonia with the bulk of this ammonia being removed from the venous blood by the liver for detoxification to urea. Hepatic urea-N production, or ureagenesis, typically exceeds the rate of hepatic ammonia-N extraction, consequently it has been suggested that the shortfall in N required for ureagenesis is contributed by amino acid-N (Parker et al. 1995; Lobley et al., 1995). This study tested the hypothesis that elevated hepatic ammonia extraction would require a concomitant increase in hepatic amino acid catabolism to supply the additional N required for ureagenesis. In order to evaluate the level of rumen ammonia production and consequently the rates of hepatic ammonia extraction, ureagenesis and amino acid catabolism. the following feeding regimens were tested in sheep held indoors in metabolism crates in three separate experiments; Firstly, lucerne pellets (Medicago sativa) were compared with fresh white clover (Trifolium repens), secondly fresh white clover was offered at either a low or high intake and finally the daily allowance of fresh white clover was fed in two 2 hour periods per day. In each experiment, silicone based catheters were surgically inserted into the posterior aorta and the mesenteric (2), portal and hepatic veins. Following a ten day dietary adjustment period and a ten day nitrogen balance, the sheep were infused with para-aminohippurate (pAH) and 15NH4Cl via the mesenteric vein. The pAH was infused to allow the blood flow across the splanchnic tissues to be estimated, whilst the 15NH4Cl was infused to trace hepatic ammonia metabolism to urea. Blood samples were collected to determine the ammonia, urea, oxygen and amino acid concentrations in the mesenteric, portal and hepatic veins, as well as the posterior aorta. Despite similar DM intakes, the nitrogen intake of the sheep fed fresh white clover was 60% higher (P < 0.001) than that of the same animals fed lucerne pellets. The difference in rumen protein fermentation in these two contrasting diets resulted in higher (P < 0.001) rumen ammonia production in the animals offered fresh white clover. There was, however, only a trend (P = 0.072) toward elevated hepatic ammonia extraction in these animals and urea production was not significantly different to the animals fed lucerne pellets. Hepatic amino catabolism was not elevated in the sheep fed fresh white clover, nor was there a significant difference in the proportion of ME intake that was utilised for ureagenesis between the two groups. In the second experiment the DM intakes of the two groups were different (P < 0 001), with the sheep offered the low intake of fresh white clover consuming 807 g DM/d whilst the high intake group consumed 1118 g DM/d. Even with these differences in intake, portal vein ammonia and urea concentrations were similar. Therefore the rate of hepatic ammonia extraction and urea production were also similar between the two intake groups. However, hepatic extraction of 15N-ammonia was higher (P = 0.033) in the high intake group compared to the low intake group. There was no evidence to suggest that the level of hepatic amino acid catabolism increased with intake level, consequently the proportion of ME intake attributed to urea synthesis was similar for the two intake groups When the experimental animals were restricted to two 2 hour feeding periods per day the DM and N intake decreased by 31% from that of the low intake group in the second experiment. There was no significant effect of time after the onset of feeding on portal ammonia or urea concentrations, hepatic ammonia extraction or hepatic urea production. However portal ammonia concentration and consequently hepatic ammonia extraction and urea production tended to be higher 4-6 hours after ingestion of fresh white clover. However this trend was not observed when the 15N tracer data was used to calculate the hepatic ammonia transfer rate. The ammonia, urea and amino acid hepatic transfer values in this experiment were largely comparable to those recorded for the low and high intake treatments in the second experiment. In these studies, there was no evidence of elevated hepatic amino acid catabolism occurring in response to elevated rates of hepatic ammonia extraction and hence ureagenesis. Additionally there was no suggestion that ammonia provided both of the N atoms of the urea molecule. It is concluded that the liver adapted to the changes in dietary nitrogen supply without incurring significant increases in the metabolic cost of ammonia detoxification to urea. However the nutritional challenges presented to the liver may not have been severe enough to induce measurable changes in hepatic ammonia metabolism. A possible mechanism to account for these observations may be that the liver adapted to the changes in nitrogen supply by altering the activity of the primary regulator of the rate of ureagenesis, carbamoyl phosphate synthetase (CPSI).Item The metabolic cost of an intestinal parasite infection on amino acid kinetics in sheep fed fresh forages: a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 2004) Bermingham, Emma NatashaThere is mounting evidence that parasitic infections change nutrient utilisation within the tissues, and that this is responsible for the reduction in animal performance that has been observed. Feeding forages that contain condensed tannins (CT) are thought to alleviate the impact of parasite infection on amino acid (AA) and protein metabolism by improving protein supply post-ruminally. However, there has been no quantification of how nutrients are partitioned in the lamb fed fresh forages during a parasitic infection. Therefore, the objective of this study was to quantify the partitioning of AA between the gastrointestinal tract (GIT), liver and the hind limb tissues (muscle, skin, fat) in lambs during an established parasite infection. It was hypothesised that the feeding of CT would alter the partitioning of AA between the GIT, liver and hind limbs in lambs with an established parasite burden due to the increased availability of dietary AA to the small intestine. This hypothesis was tested in two separate experiments, which had a similar experimental design. In the first experiment (Experiment One; 1999) lambs were fed fresh Lucerne (Medicago sativa; contains no CT). In Experiment Two, which was conducted in 2000, the lambs were fed fresh Sulla (Hedysarum coronarium; 2.2% CT; Experiment Two). One week prior to infection, permanent indwelling catheters were placed in the mesenteric artery, and the mesenteric, portal and hepatic veins and vena cava for blood sampling. Additional permanent catheters were placed in the mesenteric vein (upstream from the sampling catheter) and abdominal aorta for infusion of para-aminohippuric acid (PAH) and indocyanin green (ICG) respectively, to measure plasma flow across the splanchnic tissues (PAH) and the hind limbs (ICG). A permanent Teflon cannula was fitted in the abomasum for the infusion of [1-13C]-valine and [35S]-cysteine (Chapters Five, Six and Seven only) on day 48 post infection to measure valine and cysteine kinetics across the mesenteric-drained viscera (MDV), portal-drained viscera (PDV), liver, total splanchnic tissues (TSP; PDV + liver) and hind limbs. A temporary catheter was inserted into the jugular vein two days before the start of blood sampling for the infusion of deuterium oxide (D2O), and [13C]-sodium bicarbonate and [35S]-sulfate (Chapters Five, Six and Seven only) on day 45 post infection, and [3,4-3H]-valine on day 48 post infection. Lambs were dosed with 6 000 L3 T. colubriformis larvae for 6 d (n=5) or kept as parasite free controls (n=6). Faecal egg production was monitored every second day from day 22 to day 48 post infection and total intestinal worm burdens were determined at slaughter. Blood was continuously collected from the mesenteric, portal and hepatic veins, the mesenteric artery and the vena cava in 2-hour aliquots. Plasma was harvested and AA and metabolite concentrations measured and the specific radioactivity (SRA) and isotopic enrichment (IE) of valine and cysteine were determined. After the completion of blood sampling, but while the [3, 4-3H]-valine infusate was still being administered, the sheep were euthanased by an intravenous overdose of sodium pentobarbitone. Tissue samples were rapidly collected from the sheep in the following order: skin, muscle (biceps femoris), liver, duodenum, ileum, spleen, mesenteric lymph nodes and thymus. Digesta was also sampled from the abomasum and ileum after slaughter in order for the apparent absorption of AA to be determined. The results from Experiment One (Lucerne-fed lambs) suggest that there is no re-partitioning of AA from the posterior hind limbs to the GIT and liver during an established infection- The changes that occurred within the PDV suggests that an established parasitic infection may trigger a localised alteration in AA metabolism and/or protein turnover without significantly changing the metabolism of AA and proteins in tissues peripheral to the TSP tissues and impacting negatively on the growth of the parasitised lambs. In Experiment Two (Sulla-fed lambs) a reduction in feed intake was likely to be the reason for the alterations in the first pass metabolism of AA in the TSP tissues due to the decreased apparent AA absorption by the MDV observed in the parasitised lambs. However, the results from this experiment are in agreement with those from Experiment One confirming that there is no increase in partitioning of AA from the hind limbs to the GIT or liver during an established parasite infection. Although a statistical comparison cannot be made between the data in Experiment One (Lucerne-fed) and Experiment Two (Sulla-fed), it appears that the beneficial effects of feeding CT during a parasitic infection is due to the reduction in larval establishment in the GIT of the lamb, rather than increased AA availability. In conclusion, an established infection imposes no measurable metabolic cost on the lamb, when feed intake is not reduced. When feed intake is reduced, there is no detectable mobilisation of protein from the hind limb. Therefore, localised or other sources of AA and/or energy substrates may be utilised.