Gerald P. Cosgrove

Intramuscular fatty acid composition of neutral and polar lipids for heavy-weight Angus and Simmental steers finished on pasture or grain

Samples of M longissimus thoracis et lumborum from 78 heavy steers (41 Angus, 37 Simmental) finished on three feed types (26 on annual pasture, 25 on perennial pasture, 27 on 70% grain) were analysed for fatty acid composition of triacylglycerols and polar lipids. High levels and a wide range of intramuscular lipid (105.8 g kg−1, SD = 34.8) were due to the very high mean carcass weight of 504.5 kg. Intramuscular lipid levels did not differ significantly between breeds or feed types. Significant differences between breeds and feed types were shown for most of the fatty acids measured in both triacylglycerols and polar lipids, with significant interactions for five polar lipid fatty acids. Levels of triacylglycerols and polar lipids were not affected by feed or breed. In addition to higher levels of 18:3, lipid from pasture groups also had higher levels of other n-3 acids including 20:5 and 22:5. Differences between the pasture groups were also found, but these were smaller than the differences between pasture-and grain-fed cattle. For several fatty acids, and particularly those in polar lipids, levels varied with overall lipid level. These results with very heavy cattle and a wide range of intramuscular fat levels show clearly that variability in intramuscular fatty acid composition may arise from differences in breed of cattle, feed type or lipid level in the muscle.

Effect of interval from castration of bulls to slaughter on carcass characteristics and meat quality

Abstract A trial was conducted to see whether reducing the interval from castration to slaughter could produce steer‐like carcasses but retain the weight advantage of bulls. Ninety Angus, Friesian × Hereford, and Friesian × Simmental bulls were allocated to nine groups. Four groups were castrated at 8 months of age (steers), and three groups were castrated on January 17 (Day 0) at 17 months of age (castrates). One group of bulls and one group of steers were slaughtered on Day 5, groups of steers and castrates were slaughtered on Days 62, 111, and 166, and the remaining group of bulls was also slaughtered on Day 166. On Day 0, bulls and steers were 455 ± 6 and 426 ± 5 kg liveweight, respectively. Liveweight gain of castrates was lower than that of steers for 106 days following castration and the carcass weight (CW) advantage of bulls over steers at 17 months of age was lost in castrates slaughtered at Day 62. The rate of change in carcass, meat, and fat characteristics varied with the attribute under consi...

Effect of method of castrating bulls on their growth rate and liveweight

Abstract Bulls were castrated surgically or using a Callicrate™ Bander (Bander) to compare the effects on growth rate and liveweight. In Experiment 1, 20 bulls were castrated surgically (SCasts) at 14 months of age and 19 bulls were castrated with the Bander (BCasts). Within 7 days of castration the BCasts had large wounds above the band. Growth rates were lower (P < 0.01) over the first 29 days after castration for BCasts than for SCasts and both groups grew slower (P < 0.05) than steers castrated at weaning. There was no significant difference in liveweight between groups 108 days after castration. In Experiment 2, 10 bulls were castrated surgically at 8–9 months of age and 10 bulls were castrated with the Bander. BCasts grew slower (P < 0.05) over the first 35 days after castration than SCasts, resulting in lower liveweight for BCasts than SCasts (P < 0.05) 35–122 days after castration. No lesions occurred in the BCasts. The banding technique does not prevent the slow growth rates found after surgical castration and banding should only be used on bulls less than 14 months of age.

Effect of age of pre‐ and post‐pubertal castration of bulls on growth rates and carcass quality

Abstract Groups of bulls were castrated at birth (CB), 6 months of age (C6), or 12 months of age (C12) to test the hypothesis that age at castration had no effect on subsequent liveweight or carcass weight but can be used to manipulate carcass fatness. There was no significant difference in carcass weight among the groups (287, 292, and 288 ± 3 kg for CB, C6, and C12, respectively). Liveweight gain (LWG) from birth to 6 months was lower for CB than for C6 or C12 (1.08 ±0.02 kg d‐1 versus 1.15 ± 0.02 kg d‐1 P < 0.01). For several measures of carcass fatness there was a linear trend for increasing fatness with decreasing age at castration. For example, fat depth increased (6.9, 7.7, and 9.3 ± 0.06 mm, P < 0.05) and weight of channel fat increased (7.95, 8.64, and 9.03 ± 0.55) for the C12, C6, and CB treatments, respectively. Varying the age of castration may be used as a tool to manipulate carcass fatness to meet market specifications.

Evaluation of refractive index for measuring urinary nitrogen concentration in a sensor worn by grazing female cattle

ABSTRACT A urine sensor has been developed to measure the volume and nitrogen (N) concentration of individual urination events from female cattle in the field. The objective of this paper was to establish that the sensor’s refractive index (RI) value could be used to accurately estimate urinary-N concentration. Individual urine samples (168 in total) were collected from 18 cows that were fed monocultures (ryegrass, clover or turnips) or from cattle that grazed conventional mixed pasture (ryegrass/white clover) in the field. Regression analysis of urine sensor RI values with either urinary-N or potassium (K) concentrations yielded strong linear relationships (P < 0.001) for all feed types. However, individual regression lines varied between feed types, particularly for turnips. We conclude the use of RI in the sensor provides an accurate estimate of urinary-N but site-specific calibration of the sensor is warranted due to different feed types affecting urine K:N ratio and, by inference, other aspects of composition.

Implications of grass–clover interactions in dairy pastures for forage indexing systems. 3. Manawatu

ABSTRACT The implementation and monitoring of the treatments in the core experiment (eight perennial ryegrass cultivars grown under four combinations of plus/minus clover and high/low nitrogen (N)) at a dryland Manawatu site are described. Herbage accumulation (HA) was significantly greater for high N than for low N in 14 out of 21 annual and seasonal totals. There were no significant main effects of clover and there were no interactions between clover and N level. With the exception of autumn 2016, there were significant differences among ryegrass cultivars in all seasons, but no clover × cultivar or N × cultivar interactions for HA or nutritive value (NV). With the caveat that successive droughts reduced the proportion of white clover to low levels, the hypothesis that relative HA or NV rankings of ryegrass cultivars do not differ when ryegrass is grown in monoculture or in mixtures with white clover is supported.

Implications of grass–clover interactions in dairy pastures for forage value indexing systems. 1. Context and rationale

ABSTRACT The development of economic indexing systems for ranking cultivars of forage species requires new knowledge of factors that may influence the scaling of agronomic data collected in controlled, small-plot evaluation trials to whole farm systems. In the case of perennial ryegrass indexing, one such knowledge gap is the effect of growing clover with ryegrass on the relative rankings of different ryegrass cultivars. The objective of the investigation reported in this series was to test whether the relative yield rankings of perennial ryegrass (Lolium perenne L.) cultivars representing the range in phenotypes now available to New Zealand farmers as a result of recent breeding differed when those cultivars were grown in monocultures (as per standard protocols for cultivar yield trialling systems such as the National Forage Variety Trials) versus mixtures of grass and clover. This paper presents the rationale for the investigation by reviewing developments in perennial ryegrass breeding and evaluation in the context of grass–clover relationships in grazed pasture systems. The papers that follow report results from a multi-year, multi-site investigation comparing the yield, nutritive value and other productivity-related variables of eight perennial ryegrass cultivars grown with or without white clover (monoculture versus mixture respectively) at two levels of nitrogen fertiliser. Key considerations in the design of the experiment on which the investigation was based are discussed.

Implications of grass–clover interactions in dairy pastures for forage value indexing systems. 6. Cross-site analysis and general discussion

ABSTRACT Herbage accumulation (HA) data from four sites were combined to (1) address the hypothesis that adjustments to the New Zealand Forage Value Index to account for grass–clover interactions are not required and (2) explore the main effects of clover and nitrogen (N) fertiliser treatments on pasture productivity. In summer and autumn, pastures based on mid-season heading ryegrass cultivars consistently supported a greater clover content than pastures based on late heading cultivars. However, the clover ×  cultivar interaction was significant in only 2 of 17 HA data sets available for analysis. Thus, the hypothesis is supported. Compared with ryegrass monocultures, mixtures yielded an additional 2.4 (in the Low-N treatment) and 1.2 (High-N treatment) t DM/ha/year. Apparent N transfer from clover to grass was 79 (Low N) and 27 (High N) kg N/ha/year, derived from estimated N fixation efficiencies of 66 (Low N) and 50 (High N) kg N/t clover DM grown.

Effects of endophytic and saprophytic fungi on in vitro methanogenesis

Abstract The predominance of pasture in the diet of ruminants in New Zealand presents specific challenges for mitigation of enteric methane emissions. However, there is preliminary evidence from both laboratory and animal-based studies that some fungi may suppress enteric methanogenesis. This study determined the antimethanogenic potential of a range of endophytic (Neotyphodium species) and saprophytic (Geotrichum, Monascus, Mortierella and Penicillium species) fungi. Candidate fungi were selected on the basis of their production of various classes of secondary compounds and screened in an in vitro batch-culture fermentation assay. No strains of endophyte in ryegrass or tall fescue suppressed methanogenesis compared with their endophyte-free controls. The supernatant fractions from three strains of Mortierella wolfii were the most promising fungi identified. They suppressed methanogenesis as effectively as an inhibitor of methanogenesis (bromoethane sulphonate at 30 µmoles/L), without also reducing overall fermentation. These strains should be investigated further by screening fresh cultures grown under contrasting conditions to establish some variation in putative bioactive compounds.

Selection of a legume to use in a low phosphorus loss pasture

ABSTRACT Phosphorus loss from pastures can impair surface water quality. Losses can be partly minimised by maintaining a low soil Olsen P concentration, but there is still potential to reduce these further by minimising P lost from plant shoot material. Furthermore, although ryegrass can produce well at low Olsen P, many legumes cannot. We tested and categorised the potential for P losses (as water extractable P) from shoot material for 10 species (ryegrass, legumes and herbs) and the supporting Pallic soil over a range of Olsen P concentrations. White clover was categorised as having low potential for P loss from shoot material while exhibiting high yield relative to other species. This was especially the case at an Olsen P concentration of 15 mg kg−1—targeted as the minimum Olsen P required for good ryegrass yield, but requiring little P inputs, and likely to lose little P to surface water. However, other legumes may be more suitable under different soil or climatic conditions.