The effects of maternal calcium status during late gestation on lamb growth and survival in twin-bearing Merino ewes grazing pasture

Our project aimed to investigate whether low maternal calcium status during late gestation decreased weight, growth and survival of lambs born to twin-bearing Merino ewes grazing pasture. On day 130 of gestation, approximately a 10 mL blood sample was collected from 108 twin-bearing Merino ewes. Blood pH and calcium ion concentration were measured in whole blood and serum was analysed for calcium, magnesium, phosphate, beta hydroxy butyrate, non-esterified fatty acids and cholesterol. Six to 18 h after birth and at 49 days of age, lamb live weight was recorded. Ewe serum calcium level at day 130 of gestation were divided into tertiles (1.58-2.13, 2.14-2.30, and 2.31-2.99 mmol/L) with ewes classified as either Low, Med or High (n = 36 per group). A general linear mixed model was used to analyse the data. Survival to 1, 2, 3 and 7 days of age was lower for lambs born to ewes in the Low calcium group compared with those born in the Med and High calcium groups (P < 0.05). At day 49 of age, lamb survival tended to be lower for lambs in the Low (73.6%) compared with Med (86.8%) and High (85.3%) calcium groups (P < 0.1). There were no differences in lamb body weight (P > 0.05). Calcium levels of ewes in the Low calcium group were, on average, indicative of subclinical hypocalcaemia, with this group of ewes also having the lowest lamb survival rate, suggesting that maternal subclinical hypocalcaemia reduces lamb survival. Further studies, particularly on improving maternal calcium levels, are warranted.

Long-term liming changes pasture mineral profile

There is limited information on changes of pasture mineral concentrations over the long-term in response to liming. A long-term field experiment was conducted to assess the influence of lime application on (a) changes in pasture mineral composition over time; and (b) key pasture mineral concentrations and ratios important to animal health. Perennial and annual pastures with or without lime application were sampled annually over 12 years and analysed for macro- and micro-minerals. Mineral ratios and indices were calculated to assess the potential impact on animal health. Liming increased the concentrations of calcium, sodium and silicon, but decreased the concentrations of micro-nutrients including copper, zinc and manganese. The same trend was found in both annual and perennial pastures although there were some fluctuations between years. Liming increased the calcium:phosphorus ratio and the dietary cation-anion difference but reduced the tetany index on both annual and perennial pastures. These findings suggest a potential benefit to improve animal health outcomes for some disorders on the limed pastures. However, the reduced concentrations of some trace elements following liming potentially decreases antioxidant capacity and requires further research.

Evaluating the effect of calcium, magnesium and sodium supplementation of Merino ewes on their lambs' growth

Our study aimed to investigate responses to supplementation of calcium (Ca), magnesium (Mg) and sodium (Na) to lactating ewes and lambs grazing barley forage from lamb marking to weaning. A 10-ha paddock sown to barley was subdivided into eight plots as four replicates of two treatments. Merino ewes (n = 104) with lambs at foot were stratified to the eight plots (13 ewes and 21 lambs/plot) based on number of lambs (twin or single) and ewes' weight. Supplemented groups had access to mineral supplements (30 g/ewe/day) supplying 12 g/ewe/day ground limestone, 12 g/ewe/day Causmag® and 6 g/ewe/day coarse salt in a ratio of 2: 2: 1 by weight (as fed) from day 0 (a day before lamb marking) after sample collection. Control groups were not supplemented with minerals. Blood, milk and urine samples from ewes and blood from lambs were collected at different time points, namely, a day prior to lamb marking (day 0), 14 days after the commencement of study (day 14), and 28 days after the commencement of study (day 28). Weight of the lambs was also recorded at each time point. We found that the concentration of the forage minerals (Ca, Mg and potassium (K)) was lower on day 28 than on day 0 (P < 0.025). Liveweight gain was greater in the first 14 days compared with the second weight gain period (P < 0.001). The interaction of time and treatment was significant for liveweight (P < 0.001). Due to the improvement in weight gain of supplemented lambs, we recommend that mineral supplementation during late lactation is beneficial considering the low cost of minerals, even though the mineral content of the forage was not deficient.

Growth of young cattle grazing high-moisture winter forages in a temperate environment was not affected by access to drinking water

Context Early sown, annual ryegrass pastures and winter crops provide a high-quality feed for livestock and also have a high water content during autumn and early winter compared with typical temperate pastures. Aim We hypothesised that beef cattle grazing annual ryegrass or forage oats would not need additional access to drinking water to maintain their intake and growth. Methods In Experiment 1, 48 weaned, castrated male Hereford calves with liveweight 154 kg (±6.7 kg; s.d.) grazed Italian ryegrass at a daily allowance of 4.5 kg dry matter (DM)/100 kg liveweight in two treatments including with or without access to drinking water. In Experiment 2, 60 Hereford steers with liveweight 382 kg (±20.6 kg; s.d.) were offered a daily allowance of 5 kg DM/100 kg liveweight of forage oats in a 2 × 2 factorial design either with or without access to drinking water and with or without sorghum grain silage supplemented at 1% of liveweight. The experiments were analysed as a completely randomised design, with individual pasture plots as the experimental unit. Key results Daily growth rates of calves in the two treatments were similar (P > 0.05); however, calves with access to drinking water consumed 60% more water than did the calves without drinking water (P < 0.001). Access to drinking water had no effect (P > 0.05) on the daily growth rate of steers (P > 0.05); however, the daily growth rate of supplemented steers was 9% higher than that of the unsupplemented steers (P < 0.05). Total water intake was affected by access to drinking water (P < 0.005) but not access to supplementation (P > 0.05). Conclusions Both calves and steers derived no production benefits by having access to drinking water when grazing actively growing annual ryegrass pasture or forage oats. Nevertheless, livestock should be monitored closely so that appropriate interventions can be made if there are changes in the pasture availability or weather. Implications Grazing early sown winter forages by livestock can help circumvent the autumn–winter feed gap and these forages can be utilised more cost-effectively by not having to provide drinking water when the DM content is low.

Seasonal Dynamics of Copper Deficiency in Wumeng Semi-Fine Wool Sheep

A study of the seasonal dynamics of copper (Cu) deficiency and its effects on the antioxidant system in Wumeng semi-fine wool sheep in Weining county was conducted. In addition, the concentrations of mineral elements in soil, grass, and blood of affected and healthy Wumeng semi-fine wool sheep were determined, and blood indices were measured. The results showed that Cu contents in soil, grass, and sheep blood from the experimental pasture were significantly lower than those from the control pasture (P < 0.05), while the Mo content in the samples from the experimental pasture were higher than those from the control pasture (P < 0.05). Hb, RBC, PCV, and MDA values in the blood of affected sheep were significantly higher than those of healthy sheep, the content of TP was significantly lower (P < 0.05), and the activities of CAT, GSH-Px, CP, SOD, POD, and TP in the blood of affected sheep were lower than those in healthy sheep (P < 0.05). A comparison of different months showed that the Cu content in soil was higher in November than in June and September. Hb, RBC, PCV, WBC, and the content of MDA in the blood of affected sheep was higher in November than in June and September; however, the change in CP, CAT, GSH-Px, POD, and TP showed the opposite trend. The content of Cu and Mo in soil, grass, and blood showed seasonal changes. Therefore, it is concluded that the seasonal dynamics of Cu deficiency in Wumeng semi-fine wool sheep in Weining was due to the content of Mo and Cu in soil and grass in different seasons, and high Mo concentration in grass affected Cu deficiency in sheep. The function of the antioxidant system of Wumeng semi-fine wool sheep was reduced as a result.

A reconnaissance survey of farmers' awareness of hypomagnesaemic tetany in UK cattle and sheep farms

Hypomagnesaemic tetany (HypoMgT) in ruminants is a physiological disorder caused by inadequate intake or impaired absorption of magnesium (Mg) in the gut. If it is not detected and treated in time, HypoMgT can cause the death of the affected animal. A semi-structured questionnaire survey was conducted from July 2016–2017 to assess farmers’ awareness of HypoMgT in cattle and sheep in the UK. The questionnaire was distributed to farmers at farm business events and agricultural shows, and through a collaborative group of independent veterinary practices to their clients. Farmers were asked about (i) the incidence of presumed HypoMgT (PHT); (ii) their strategies to treat or prevent HypoMgT; (iii) mineral tests on animals, forage and soil, and (iv) farm enterprise type. A total of 285 responses were received from 82 cattle, 157 mixed cattle and sheep, and 46 sheep farmers, of whom 39% reported HypoMgT in their livestock, affecting 1–30 animals. Treatment and/or prevention against HypoMgT was reported by 96% respondents with PHT and 79% of those without. Mineral tests on animal, forage, and soil was conducted by 24%, 53%, and 66% of the respondents, respectively, regardless of PHT. There was a highly significant association between the use of interventions to tackle HypoMgT and the incidence of PHT (p < 0.01). The top three treatment/prevention strategies used were reported as being free access supplementation (149), in feed supplementation (59) and direct to animal treatments (drenches, boluses and injections) (45) although these did vary by farm type. Although some (9) reported using Mg-lime, no other pasture management interventions were reported (e.g., Mg-fertilisation or sward composition). Generally, the results indicate that UK farmers are aware of the risks of HypoMgT. A more integrated soil-forage-animal assessment may improve the effectiveness of tackling HypoMgT and help highlight the root causes of the problem.