Four digestibility and balance experiments were carried out in which 33 growing heifers were fed basal diets of low dry matter silage offered ad libitum, supplemented with various levels of barley and/or groundnut meal or urea.Voluntary intake of the silages was low although apparent digestibility of D.M. was high (66-75 %). There was a significant linear negative relationship between the intake of D.M. as supplement and silage D.M. intake.Apparent digestibility of crude fibre in the silages was high (74-83 %). It was depressed significantly by addition of barley but not by addition of groundnut. There was a highly significant linear relationship between the digestibility of D.M. and G.B. in the mixed silage concentrate diets used. Metabolizable energy (M.E.) values for the silages varied from 2-04 to 2-52 Mcal/kg (8-5-10-5 MJ/kg) D.M. Supplementation with barley at approximately 1 % of live weight, increased M.E. values of the mixed diets to 2-57-2-85 Mcal/kg (10-8-11-9 MJ/kg) D.M. Additional N had little effect on these values. Nitrogen retention was significantly increased in all experiments by barley supplementation. It was further significantly increased by groundnut in three experiments and by urea in one experiment.Multiple regression analysis showed that N retention was significantly related to both M.E. intake and intake of absorbed N, and to M.E. intake and intake of supplementary N.Apparent availabilities of Ca and Mg in silage based diets were low and the availability of Na varied with Na intake. Supplementation with either energy or nitrogen increased apparent availability and retention of Mg but did not exert consistent effects on availability or retention of Ca or Na.There was a highly significant linear relationship between ingested and digested Na but not for Ca or Mg. There was a highly significant linear relationship between absorbed and retained Ca and Mg, but not for Na.Animals fed second cut silages had rather low blood glucose levels and higher than normal levels of blood ketones.

Since, under Irish conditions, the source of protein used in pig rations often varies from one area to another, an experiment was conducted to determine the accumulation of copper in the tissues of pigs given the commonly-usedprotein sources in diets containing 250 ppm of supplemental copper. The protein sources compared were (a) white-fish meal (370 ppm Cu), (b) soya bean meal (17 ppm. Cu), (c) roller-dried skim milk (2 ppm Cu), and (d) a mixture of soya bean meal and meat and bone meal (5 ppm Cu) (Table 1). The minerals, vitamins and copper sulphate were premixed with about 5 kg. of barley and distributed over the total feed before mixing. The copper sulphate was sieved to remove coarse particles. Analyses of complete feed mixtures are shown in Table 1. As far as possible, the rations were balanced for crude protein, calcium and phosphorus.

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