G. E. Lamming

The influence of castration on the growth of male pigs in relation to high levels of dietary protein

1. A factorial split-plot experiment was conducted to investigate the growth of entire and castrate male pigs on conventional diets and diets containing higher levels of protein. Thirty-two Large White pigs were fed ad libitum from 50 lb to slaughter at 260 lb live weight. The carcasses were dissected. 2. The live-weight gain of entire males was the same as that of castrates on the conventional diet, but they grew non-significantly faster than castrates on the higher protein diet. 3. The entire males had a lower dressing percentage and less fat in the carcass than the castrates, but more lean, bone and rind, and a similar lean: bone ratio. The leanness of the entire males was increased on the higher level of dietary protein whereas the leanness of the castrates was unaffected except in the leg. The interactions were not significant. 4. The carcasses of the entire males were proportionately heavier in the head and shoulders and lighter in the middle than those of the castrates. 5. The majority of the entire males had flesh with a slightly tainted flavour.

Studies on the nutrition of ruminants. 5. The effect of diets containing up to 70% ground barley straw on the live-weight gain and carcass composition of yearling Friesian cattle.

1. Three groups, each of eight steers, were fed on pelleted diets containing 30, 50 or 70% ground barley straw, maize and soya bean meal. On an air-dry basis the diets contained 12% crude protein. 2. Daily live-weight gain was 1·29, 1·19 and 1·02 kg/day for the 30, 50 and 70% straw diets respectively, and was negatively related to the percentage of crude fibre in the dry matter ( r = −0·61, P 3. The apparent digestibility of dry matter, determined in sheep at the maintenance level of feeding was negatively related to percentage crude fibre in the dry matter ( r = −0·91, P 4. All animals were killed at approximately the same live weight, which was reached on average in 140,153 and 163 days by the 30, 50 and 70% groups, respectively. 5. The differences in mean carcass weight between treatments were significant ( P P 6. The proportion of straw in the diet had no direct effect on the composition of carcass gain. 7. The results are discussed in relation to the intake of digestible energy.

Studies on the nutrition of ruminants. 4. The use of ground straw of different particle sizes for cattle from twelve weeks of age.

Twenty-four Friesian calves were fed from twelve weeks of age on six diets containing 15 or 30% ground barley straw, the straw being ground through screens of and in. From twelve weeks to seven months of age (120–250 kg) the calves had mean growth rates of 1·15 kg/day with a feed conversion ratio of 4·15: 1. From seven to eleven months of age (250–380 kg) the corresponding figures were 1·16 kg/day and 5·53: 1, and in the final fattening period of 11–14 months (380–500 kg), 0·92 kg/day and 8·19: 1. These differences between stages of fattening were highly significant. There were no differences in performance due to the particle size of the straw or to the proportion of straw in the diet.

The influence on growth rate and slaughter characteristics of implanting fattening male hoggets with various levels of hexoestrol and diethylstilboestrol

In three trials involving 288 hoggets the influence on growth rate of implanting 15 mg. hexoestrol or 12 mg. stilboestrol was compared. In one trial the influence of adding excipient to either stilboestrol or hexoestrol to increase the surface area of the implant was also assessed. Live-weight gain was calculated for each time interval after implantation and it was concluded that after approximately 140 days the influence of implantation had largely disappeared. For optimum benefit to live-weight gain implantations should be made approximately 100 days prior to slaughter. In all trials, implantation with synthetic oestrogens resulted in extra daily live-weight gain, the increase for all animals amounting to 31% extra daily gain for hexoestrol and 26% for stilboestrol. The addition of excipient to the implant diminished the initial growth response and reduced the extra gain achieved. Implantation with the synthetic oestrogens significantly increased the final live-weight on the farm, live-weight before slaughter and carcass weights when groups of animals from each treatment were slaughtered together. Stilboestrol and hexoestrol implantation resulted in an extra 4·7 and 6·1 lb. full live-weight; 3·7 and 5·3 lb. empty live-weight and 1·3 and 2·8 lb. extra carcass weight respectively, compared to controls killed at the same time. Where hoggets had received a high-plane diet, treatment did not affect killing-out percentage, but where the level of nutrition was lower a decrease of up to 1% was observed. In all trials treatment with the synthetic oestrogens resulted in an increase in pelt weight and in one trial this increase was up to 2 lb. Implantation with hexoestrol and stilboestrol increased the size of the gut full and empty in two of the trials. The differences were reduced when the gut weights were corrected to 100 lb. empty live-weight. The weight of the thyroid gland or the total weight of the trachea, heart and lungs were not affected by treatment. The approximate rate of uptake of hormone from a 12 mg. implant of stilboestrol was assessed by the decrease in the weight of dried tablet removed at slaughter from 30 to 200 days after implantation. The linear regression y (uptake in mg.)=3·029+0·039x (days from implantation) fitted the data best, giving an approximate average uptake over this period of 39 micrograms of stilboestrol per day.

A note on the substitution of protein by non-protein nitrogen in beef rations.

Many observations have been made on the metabolic effects of urea ( see reviews by Reid, 1953; McLaren, 1964) and on the problem of urea poisoning (Repp, Hale and Burroughs, 1955), but little information is available on the use of urea for fattening beef cattle under conventional intensive systems. There has been considerable interest shown in the use of biuret as a source of non-protein nitrogen (NPN) as it has been found to be less poisonous than urea when consumed in large quantities (Berry, Riggs and Kunkel, 1956).