Abstract
Simple SummaryWhole milk contains low levels of iron, as such this trial examined iron deficiency anaemia in dairy calves fed whole milk. Our trial evaluated the effect of iron supplementation on growth rate and haemoglobin (Hb) levels of these calves. We enrolled 237 calves across six farms, each farm had half of its calves injected with iron and half without. Calves were weighed three times throughout the study and had haemoglobin levels measured at one and six weeks old. Iron caused an average increase in growth rate of 78 g/d (Standard Deviation (SD) 18 g/d) in injected calves compared with control calves. Iron caused a significant increase of haemoglobin levels by six weeks, and haemoglobin levels in the calves that had not received the iron, the iron dropped by an average of 12.1 g/L (SD 15.1). Calves with a higher growth rate in the first six weeks were also more likely to have low Hb levels at six weeks. There was variation in the growth rate differences and haemoglobin levels on each farm. However, overall across all farms, iron makes a difference to daily weight gain (DG) in the first six weeks but the magnitude of effect seems to be farm-specific, as there is a notable difference between farm DG variations. Anaemia caused by iron deficiency has long been reported in dairy calves. This study investigated iron deficiency anaemia on UK dairy farms feeding whole milk and evaluated the effect of iron supplementation on the daily weight gain (DG) and haemoglobin (Hb) levels of these calves. Two-hundred-and-thirty-seven calves were enrolled across six farms. At enrolment, calves were randomly allocated to either receive treatment with iron injection (INJ; n = 120) consisting of 5 mL (1 g iron) of iron dextran (Uniferon 20% Injection, Pharmacosmos) or no injection, control (CON; n = 117). Calves were blood-sampled for Hb and total proteins and weighed at weeks one, six and 12 of age. Iron had a significant effect on DG from one to six weeks, with an average 78 g/d (SD 18 g/d, n = 188, 95% Confidence interval: 44–112 g/d, p < 0.001) DG increase in the INJ calves. Iron had a significant effect on Hb concentration at six weeks between the INJ group and CON group (110.7 (SD 12.4) versus 94.9 g/L (SD 13.2), respectively). Calves with a higher growth rate from one to six weeks were more likely to have low Hb levels at six weeks. There was farm variation in both Hb levels and DG, however, despite this, there was an effect of iron across all farms.
Highlights
Anaemia caused by iron deficiency has long been reported in dairy calves [1,2]
Calves with a higher growth rate from one to six weeks were significantly more likely to be under the 90 g/L threshold (Odds Ratio (OR) 5.0, 95% Confidence Interval (CI):1.7–14.2, p = 0.003)
The effect of increased daily weight gain (DG) pre-weaning is well known to have long-term benefits. This data has shown that calves on whole milk diets injected with iron have a significantly increased DG in the first six weeks
Summary
Anaemia caused by iron deficiency has long been reported in dairy calves [1,2]. Iron is primarily sourced from recycled red blood cells at 24 mg/d and diet at 1–2 mg/d [3]. Iron primarily functions as a Animals 2020, 10, 853; doi:10.3390/ani10050853 www.mdpi.com/journal/animals. Animals 2020, 10, 853 component of heme, an essential component to haemoglobin’s structure. A deficiency in iron results in reduced haemoglobin (Hb) synthesis, causing reduced red blood cell production and anaemia. New-born calves and piglets are born with finite stores of iron, relying on dietary supplementation once these are used [4]. Whole milk contains 0.5 mg of iron/kg (range 0.3 to 0.6 mg/kg) [5]. The most recent dietary guidelines from the National Research Council (2001) suggest that a six-week-old calf growing at
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