Shawn McGrath

The effect of forage type on lamb carcass traits, meat quality and sensory traits.

The aim of this study was to evaluate the effect of different forage-types on lamb carcass, meat quality and sensory attributes. Sixty-two, White Dorper lambs finished on bladder clover, brassica, chicory+arrowleaf clover, lucerne+phalaris or lucerne, were slaughtered at a commercial abattoir. At 24h post-mortem, the m. longissimus thoracis et lumborum (LL) was removed from the left side and sliced into three equal sub-samples, vacuum packaged and randomly assigned to ageing periods (5, 12 or 40days) and the right side was aged for 5days. The m. semimembranosus and m. adductor femoris were removed and, the former was then aged for 40days. Lambs fed chicory+arrowleaf clover or lucerne had a higher dressing percentage and fat depth. Bladder clover gave the highest level of glycogen in the LL. No sensory or other meat quality trait differences were found between the treatments. In general, no treatments showed any unfavourable effect on the traits examined.

Mineral supplementation of lambing ewes grazing dual-purpose wheat

Lambing ewes were grazed on dual-purpose wheat in two experiments in 2010 and 2011 with or without access to a mineral supplement. The calcium, magnesium and sodium content of wheat forage was below the requirements of ewes during late pregnancy and lactation; however, no clinical cases of hypocalcaemia or hypomagnesaemia were observed in either experiment. Blood serum assays identified eight hypocalcaemic ewes and one hypomagnesaemic ewe in Experiment 1, and one hypocalcaemic ewe in Experiment 2, and the provision of a mineral supplement comprising of magnesium oxide, calcium carbonate and coarse salt had no effect on blood magnesium, total calcium, phosphorus or sodium. Lamb birthweight and survival were not affected by provision of the mineral supplement in either experiment; however, the growth rate to marking (mean 38 ± 10 days of age) of twin-born lambs was higher in Experiment 1 when the supplement was provided to ewes grazing wheat (259 vs 243 g/head.day; P = 0.002).

Factors involved in high ewe losses in winter lambing flocks grazing dual-purpose wheat in southern New South Wales: a producer survey

A comparative survey was undertaken with 43 sheep producers in southern New South Wales using a semi-structured interview to investigate factors associated with high ewe mortality rates in winter lambing flocks grazing dual-purpose wheat. Participants were classified as either control (n = 23), who had not observed abnormally high ewe deaths, or case (n = 20), who had observed abnormally high ewe mortality rates when sheep grazed dual-purpose wheat. Ewe losses associated with grazing wheat were higher in the case group compared with the control group (8.6 vs 1.8%; P < 0.001) and there was also more deaths attributed to metabolic disease (3.4 vs 0.6%; P < 0.05). A higher proportion of control respondents had provided magnesium or sodium supplementation to ewes grazing wheat (P < 0.05). The body condition score of ewes entering the grazing period was significantly higher in the control group (3.2 vs 2.8; P < 0.05). The proportion of respondents who fed roughage to ewes grazing wheat did not differ significantly between control and case groups (48 vs 35%). A higher proportion of respondents in the case group had supplied grain to ewes (25 vs 0%; P < 0.05), which may have been associated with the lower body condition of sheep in these flocks compared with the control group. It was concluded that supplying ad libitum access to mineral supplements that include magnesium, sodium and possibly calcium, and maintaining adequate body condition score can reduce the risk of high ewe mortality rates when reproducing ewes graze dual-purpose wheat.

Modelling the effect on stocking rate and lamb production of allowing ewes to graze a dual-purpose wheat crop in southern New South Wales

Slow pasture growth rates during winter limit the potential gross margins from autumn and early winter lambing in southern New South Wales (NSW) by limiting stocking rates and/or increasing supplementary feed requirements. Dual-purpose crops can reduce the winter feed gap in mixed-farming systems by increasing the available feed in winter. The simulation software AusFarm was used to model a mixed-farming system at Wagga Wagga with Merino ewes joined to terminal sires and grazing lucerne-subterranean clover pasture over a 41-year period. A paddock of dual-purpose wheat was then added to the system, and ewes were allowed to graze the wheat crop when feed on offer reached 850 kg DM/ha and before GS31. Weaned lambs were sold after late August if lamb growth rates fell below 20 g/head.day, mean lamb weight reached 45 kg or production feeding of lambs was required. Lambing in June resulted in the highest median gross margin whether or not ewes were able to graze the wheat crop during winter. Grazing of a dual-purpose wheat crop resulted in greater proportional increases in gross margins as stocking rate was increased, increased lamb production and reduced supplementary feeding costs, and reduced interannual variability in gross margin returns.