Feeding British rapeseed meals to pregnant and lactating ewes

Abstract

ABSTRACTThree types of high glucosinolate British rapeseed meal (RSM) — extracted, expeller and extruded — were incorporated in ewe diets at 200 g/kg; soya-bean meal (SBM) at 165 g/kg replaced RSM in a control diet. Eighty housed Suffolk-Mule ewes were divided into four equal groups and given one of four diets, A (control SBM), B (extracted RSM), C (expeller RSM) or D (extruded RSM) for one reproductive cycle. Diets A and B were compared for a second season. The ewes were given a maximum of 2·5 kg diet per day during lactation. Barley straw was available ad libitum. The ewes were mated in November and December. Lambs were weaned at 42 days of age; they were given creep food similar in composition to their dams' lactation diets.There were no dietary effects on ewes in overall health, live weight, oestrous activity, conception, number of lambs born alive or lamb birth weights. A mean of 1·6 lambs were weaned per ewe mated and 58% of these were twins, in year 1. In year 2, 1·8 lambs were reared and 79% were twins. The mean milk yield over the first 4 weeks of lactation was 3·2 1 and there were no significant dietary effects. Fat concentration in milk was very variable, but in general was slightly depressed by the RSM diets, significantly so at three sampling dates. Protein concentration was consistently lower in milk from RSM than SBM groups, significantly lower at four of the weekly samplings. Thiocyanate levels in plasma and milk were related to glucosinolate intake, but were not associated with any detrimental effects. At all sampling dates, values for RSM groups were significantly greater than for SBM ewes. Plasma thyroxine values were similar regardless of diet