Forty-eight pigs, 16 each of boars, barrows, and gilts, were allotted at an average age of 41 days to two treatment groups based on dietary protein level, either 18% protein throughout or 16% protein in the growing period (start to 50 kg) and 13% protein in the finishing period (50–90 kg). Feed intake during the growing period was influenced by sex with boars eating less (P < 0.05) than barrows. No significant differences in feed intake were observed for the overall experiment but the trend established in the growing period still existed. In the overall experiment sex did not influence rate of gain, which averaged 0.72 kg/day. Higher dietary protein level improved (P < 0.01) gain in comparison with the lower levels. A significant interaction existed between sex and protein, boars responding more to high protein than barrows, and gilts being intermediate. Feed conversion was influenced (P < 0.05) by sex and protein level, boars being superior to barrows or gilts and pigs fed the higher protein diet (3.16 kg feed per kg gain) superior to those fed the lower protein diet (3.36 kg feed per kg gain). Barrows dressed 79.6% and gilts 79.3% both higher (P < 0.01) than boars, which dressed 75.9%. Boars had a grade index of 102.6 and gilts 101.4, both of which were higher (P < 0.01) than barrows with 97.9. Other carcass measurements generally ranked the sexes in order of superiority as boars, gilts, and barrows. Boar carcasses had more muscle and less fat (P < 0.01) than barrows, gilts being intermediate. Dietary protein level did not significantly influence carcass composition. Six muscles were analyzed for protein, fat, and ash. No significant differences between sexes were found, but higher protein level increased (P < 0.05) the percentage protein in the longissimus dorsi muscle. Fatty acid analyses of backfat showed no significant differences except in linoleic and linolenic acids, for which boars and gilts had higher percentages than barrows. Detectable sexual odor on cooking was judged to be present in 56% of boar carcasses. If procedures to eliminate sexual odor can be developed, boars offer promise as market animals, particularly if they are fed relatively high protein diets.
Effect of Prepartum Dietary Protein Level on Performance of Primigravid and Multiparous Holstein Dairy Cows
