A note on energy intake and nitrogen balance of fattening lambs given all-concrate diets

Four levels of a proprietary concentrate (0, 100, 200 and 400 g/day) were offered to Welsh Mountain ewe lambs receiving hay or straw ad libitum for 14 weeks. The apparent digestibility of the energy and nitrogen in the various diets was determined in a concurrent digestibility trial. The voluntary intakes of the straw and hay dry matter when given alone were 242 and 451 g/day respectively (28-4 and 49-2 g/kg W 0 " 73 per day). Straw intake increased with an increase in concentrate feeding up to a level of 25 % concentrate in the total dry matter and then declined. Hay intake declined linearly with increasing concentrate level (3 g/day decline per unit increase in the percentage of concentrate). In each case the total intake of dry matter and digestible energy increased with an increase in concentrate level. There was a positive within-treatment relationship between initial live weight and voluntary intake, an additional 0-019 Meal ME/day being consumed per kg increase in live weight. Within treatment groups lambs consuming relatively more food also made relatively higher weight gains. Estimates based on published standards of the metabolizable energy intakes required to produce the live weight changes observed on each treatment were considerably higher than the intakes recorded in the trial. Recent experiments by Blaxter and Wilson (1963), Holmes, Jones, Drake-Brockman and White (1965) and Campling and Murdoch (1966) support the opposite conclusion, that the higher the quality of the roughage the greater the depression in intake when concentrates are given.

Section: Discussionmentioning

confidence: 80%

The voluntary intake and utilization of roughage–concentrate diets by sheep. 1. Concentrate supplements for hay and straw

Crabtree

Williams

1971

The effect of cereal and protein source on the energy intake and nitrogen balance of fattening lambs given all-concentrate diets

Davies

1968

Energy intake and nitrogen balance studies have been conducted on 12 lambs fed ad libitum on four all-concentrate diets of equal crude-protein content in an experiment of latin square design. Each diet contained one cereal, either barley or oats and one protein supplement, either white-fish meal or soya bean meal.Protein supplements had no influence on energy intake, but intake was significantly higher when the lambs were given barley rather than oat diets.There were highly significant differences in the degree of utilization of digested nitrogen between diets containing fish meal and soya bean meal, and between diets containing barley and oats.The energy: nitrogen ratio of urine was inversely related to the proportion of urinary nitrogen present as urea and directly related to the degree of utilization of digested nitrogen.

A study of protein utilization by weaned lambs

Robinson¹,

Forbes²

1970

SUMMARYFifty weaned store lambs approximately 7-month-old were used in an experiment designed to assess their protein requirements and utilization. At the beginning of the experiment a random sample of 10 animals were slaughtered and their loin joints analysed. The remaining 40 were allocated at random to four dietary treatments (T1, T2, T3, T4) comprising four crude protein intakes at a constant energy intake. The experiment was divided into two periods. During period 1 (48 days) the dietary crude protein intakes were 58 (T1), 111 (T2), 170 (T3), and 198 (T4) g/day with a mean digestible organic matter intake (DOMI) of 578 g/day. During period 2 (55 days) the corresponding crude protein intakes were 89, 157, 215, 251 and the DOMI was 678 g/day.Digestibility and nitrogen balance trials were carried out on two animals from each treatment in period 1 and on six animals on each treatment in period 2. At slaughter the loin joints from five animals on each dietary treatment were chemically analysed.The only significant effect on live-weight gain of varying protein intake was a lower gain on the lowest protein intake (T1) in period 1. It was estimated that the optimum ratio of digestible protein intake (g) to digestible energy intake (meals) for live-weight gain in period 1 was approximately 30 : 1 and in period 2 approximately 21 : 1. There was a significant increase in killing-out percentage with increasing crude protein intake. The digestibility of dry matter and nitrogen increased with increasing crude protein intake. There was a significant quadratic relationship between the apparently digested nitrogen intake in g/day (X) and nitrogen retained in g/day (Y). The regression equation wasY= −0·008X2+ 0·537X+ 0·682Liver copper levels decreased with increasing crude protein con-centration in the diets.