THE EFFECTS OF FISH MEAL SUPPLEMENTATION UPON THE PERFORMANCE OF FINISHING LAMBS FED MAIZE SILAGE DIETS

Mohamad  A.  KOSSAIBATI

A preliminary trial with store lambs given diets based on maize silage demonstrated that fishmeal supplementation promoted greater live‑weight gain and silage intake, than urea or soyabean meal. The objective of this thesis was to examine further the effect of fish meal and energy supplementation of maize silage upon voluntary intake and growth of lambs.

Store lambs were fed maize silage diets with forage to concentrate ratio of 90:10 or 60:40. Urea or fishmeal (two levels) provided supplementary nitrogen. Live‑weight gain, carcass weight, nitrogen balance, but not silage intake were increased by fishmeal but most of the response was obtained with the first increment. The higher ratio of concentrate did not affect live‑weight gain but increased carcass weight and nitrogen balance and reduced silage intake, though total energy intake was maintained.

In another experiment with 60:40 maize silage to concentrate ratio, the concentrate contained rapeseed meal (two levels) or fishmeal. Supplementation with fishmeal reduced silage intake, but had no effect on live‑weight gain, carcass gain or body composition. Supplementation with the high level of rapeseed meal lowered silage intake, live‑weight and carcass gains and fat deposition but did not affect protein deposition.

A third experiment investigated the effect of protein and energy supplements on urinary excretion of allantion, as an index of rumen microbial protein synthesis. Mature ewes were offered maize silage diets of 90:10 or 60:40 forage to concentrate ratio. Supplementary nitrogen was provided by urea, rapeseed meal or fishmeal. Food intake was highly variable. Date from animals with normal intake suggested that fishmeal and barley increased excretion of allantoin.

It was concluded that supplementation of maize silage with fishmeal rather than non‑protein nitrogen has a beneficial effect on live‑weight and carcass gains. Supplementation with barley appears to increase carcass weight.