• Adding value to milk by increasing its protein and CLA contents

      Murphy, J.J.; Stanton, Catherine; O'Donovan, Michael; Kavanagh, S.; Maher, J.; Patton, Joe; Mohammed, Riaz (Teagasc, 2008-08-01)
      The mid-summer milk protein study was undertaken on 34 commercial dairy farms in 2005 to evaluate the influence of dietary and management variables on milk protein content in mid-season. Data on grass composition, genetic merit of the herds and milk protein content were collected and analysed by multiple regression. Both calving date and genetic merit for milk protein content were significantly associated with milk protein content and were used as adjustment factors when evaluating the association between measures of grass quality and milk protein content. Milk protein content was associated with grass OMD (P = 0.04) and NDF content (P = 0.02) but not with CP content (P = 0.80). It is concluded that herds calving earlier, with a greater genetic merit for milk protein content and consuming better quality pasture would have greater milk protein contents in mid-season.
    • Adding value to milk by increasing its protein and CLA contents.

      Murphy, J.J.; Stanton, Catherine; O'Donovan, Michael; Kavanagh, S.; Maher, J.; Patton, J.; Mohammed, R. (Teagasc, 2008-08-01)
      Five experiments were undertaken in this project; one on mid-summer milk protein and four on milk CLA content. Thus the two main objectives of this project were to determine the factors associated with milk protein concentration in mid-summer and to investigate potential further strategies to increase the CLA content of pasture produced milk.
    • Effects of daily herbage allowance and stage of lactation on the intake and performance of dairy cows in early summer

      Stakelum, G.; Maher, J.; Rath, M. (Teagasc, Oak Park, Carlow, Ireland, 2007)
      The aim of this study was to investigate the relationship between daily herbage allowance (DHA) and the performance of dairy cows at two stages of lactation. Spring-calving (n=42, mean calving date 17 February) and autumn-calving (n=42, mean calving date 22 September) Friesian cows were divided into three equal groups and assigned to three levels of DHA (above a cutting height of 35 mm), 17 (L), 20 (M) and 23 (H) kg of dry matter (DM) per head, from late April to late June, 1996. The spring-calving cows grazed to sward heights (mm) of 47, 56 and 65 (s.e. 0.6) and residual herbage organic matter (OM) masses (above 35 mm) of 294, 408 and 528 (s.e. 12.1) kg/ha for L, M and H, respectively. The autumn-calving cows grazed to corresponding sward heights of 51, 60 and 69 (s.e. 1.1) mm and leftresidual herbage OM masses of 364, 445 and 555 (s.e. 12.9) kg/ha for L, M and H, respectively. Pastures were mechanically topped post grazing. Spring-calving cows consumed 13.3, 14.7 and 15.5 kg OM (s.e. 0.47) per day, and autumn-calving cows consumed 13.3, 13.8 and 14.9 kg OM (s.e. 0.43) per day for L, M and H, respectively. Mean daily solids-corrected milk yield was 23.1, 23.8 and 24.8 (s.e. 0.34) kg for the spring-calving cows, and 17.5, 18.4 and 18.7 (s.e. 0.35) kg for the autumncalving cows, for L, M and H, respectively. Milk yield could be predicted from preexperimental yield (PMY) and daily herbage organic matter allowance (DOMA, kg) according to the following equation: y = −1.13 + 0.76 (s.e. 0.030) PMY + 0.22 (s.e. 0.057) DOMA (r.s.d. 1.32, R2 0.89). The results indicate that high individual cow and herd production levels can be achieved from high quality herbage alone during early summer at a DHA of 23 kg DM for spring-calving cows and 20 kg DM for autumn-calving cows.
    • Reducing the nitrate content of protected lettuce.

      Byrne, C.; Maher, J.; Hennerty, J.; Mahon, J.; Walshe, A. (Teagasc, 2001-03-01)
      A research project was carried out jointly between Teagasc, Kinsealy Research Centre and University College Dublin, Department of Crop Science, Horticulture and Forestry which studied the effects of cultivar, nitrogen fertilisation and light intensity on the nitrate content of protected butterhead lettuce. In a series of cultivar trials of winter and summer butterhead lettuce, significant differences in the nitrate content of the lettuce between cultivars were found only in one experiment. In this instance, the differences were not consistent between successive harvests. It was concluded that screening lettuce cultivars for tissue nitrate level is unlikely to contribute to an overall reduction of nitrate levels. The application of N in a liquid feed throughout the cropping period resulted in higher nitrate levels in lettuce plants grown in soil filled containers compared with a similar amount of N applied to the soil before planting. Withdrawing N for the final 10 days of the cropping period did not affect the nitrate content of the lettuce. In an experiment studying nitrogen source and rate on lettuce grown in containers, the use of calcium cyanamide as a N source resulted in lower nitrate levels in the lettuce and gave a reduced head weight compared with calcium ammonium nitrate (CAN) or ammonium sulphate. Increasing the rate of CAN or ammonium sulphate gave higher lettuce nitrate levels. A nitrification inhibitor reduced the soil nitrate levels especially with sulphate of ammonia as the N source but did not affect the plant nitrate levels significantly. The addition of chloride to the soil reduced nitrate levels in the lettuce. In a further fertilisation study using containers, calcium cyanamide again resulted in lower plant nitrate levels than CAN. Increasing the rate of CAN increased soil nitrate levels, lettuce head weight and plant nitrate levels. The relationship between soil nitrate levels, lettuce head weight and plant nitrate level indicates that the level of 100-150 mg·L-1 of nitrate N in the soil, advocated in the Code of Good Practice, is a compromise between maximising plant growth and minimising lettuce nitrate content. A comparison between CAN and calcium cyanamide in a border soil experiment again showed that the latter N source resulted in lower lettuce nitrate levels. In this experiment the addition of chloride to the soil did not affect plant nitrate levels. Lettuce was grown, in late summer, in small tunnels using a range of polyethylene cladding materials. Head weight correlated well with the overall light transmission of the materials. In one of the materials that had a low light transmission, lettuce nitrate content was doubled compared with those grown under the materials with high light transmission. Under both winter and summer conditions, the nitrate content of lettuce heads was not influenced by the time of day at which harvest took place. In experiments in which multiple harvests were carried out there was no consistent trend in nitrate content as the heads developed and matured. Within individual heads of lettuce there was a steep concentration gradient with the older outer leaves having much higher concentrations of nitrate than the younger inner leaves. Herbicides commonly used in protected lettuce production did not influence the nitrate content of the lettuce.