Four multiparous cows with cannulas in the rumen and proximal duodenum were used in early lactation in a 4 x 4 Latin square experiment to investigate the effect of method of application of a fibrolytic enzyme product on digestive processes and milk production. The cows were given ad libitum a total mixed ration (TMR) composed of 57% (dry matter basis) forage (3:1 corn silage:grass silage) and 43% concentrates. The TMR contained (g/kg dry matter): 274 neutral detergent fiber, 295 starch, 180 crude protein. Treatments were TMR alone or TMR with the enzyme product added (2 kg/1000 kg TMR dry matter) either sprayed on the TMR 1 h before the morning feed (TMR-E), sprayed only on the concentrate the day before feeding (Concs-E), or infused into the rumen for 14 h/d (Rumen-E). There was no significant effect on either feed intake or milk yield but both were highest on TMR-E. Rumen digestibility of dry matter, organic matter, and starch was unaffected by the enzyme. Digestibility of NDF was lowest on TMR-E in the rumen but highest postruminally. Total tract digestibility was highest on TMR-E for dry matter, organic matter, and starch but treatment differences were nonsignificant for neutral detergent fiber. Corn silage stover retention time in the rumen was reduced by all enzyme treatments but postruminal transit time was increased so the decline in total tract retention time with enzymes was not significant. It is suggested that the tendency for enzymes to reduce particle retention time in the rumen may, by reducing the time available for fibrolysis to occur, at least partly explain the variability in the reported responses to enzyme treatment.

Two trials were conducted to evaluate effects of feeding supplemental fibrolytic enzymes or soluble sugars and malic acid on milk production. In trial 1, 257 cows at four sites were fed a basal diet consisting of no more than 60% of forage DM as corn silage and less than 40% as alfalfa hay. Cows were assigned randomly within site, parity, and two stages of lactation to: 1) control; 2) enzyme A; 3) enzyme B; and 4) soluble sugars and malic acid. There was a 14-d pretreatment and an 84-d treatment period. Enzyme solutions were sprayed on either the forage component or the TMR each day while mixing feed. Trial 2 was similar, except 122 cows at one site in the United Kingdom were fed diets containing forage that was 75% corn silage and 25% grass silage, and all cows began the study between 25 to 31 DIM. Mean milk productions for 233 cows that completed trial 1 were 32.9, 32.5, 32.4, and 32.9 kg/d for control, enzyme A, enzyme B, and soluble sugars and malic acid, respectively. Mean milk productions for 116 cows that completed trial 2 were 28.2, 27.9, 28.8, and 28.4 kg/d, respectively. In vitro analyses of the activities of enzyme solutions indicated that all major cellulose and hemicellulose degrading activities were present; however, the pH optima (approximate pH = 4 to 5) were more acidic, and the temperature optimum (approximately 50 degrees C) was greater than normal pH and temperature in the rumen. If fibrolytic activity in the rumen is a major mechanism of action of supplemental fibrolytic enzymes, it appears that considerable activity of these preparations was lost due to conditions in the rumen. In conclusion, feeding supplemental fibrolytic enzymes or malic acid with soluble sugars had no effect on milk production under the conditions used in this study.

Eighty Holstein cows (first, second, or third lactation) were used to evaluate the efficacy of a prolonged-release formulation for sometribove (n-methionyl bovine somatotropin). Cows were fed ad libitum a complete mixed diet and milked twice daily. Cows were allocated randomly by parity to two treatment groups receiving 500 mg sometribove in a prolonged release formulation or excipient at 14-d intervals starting at 60 +/- 3 d postpartum and continuing for 36 wk. Treatment with sometribove increased FCM yield to a similar extent (11.4%, +3.1 kg/d) in primiparous and multiparous animals. Milk content of lactose, fat, ash, and Ca was not affected, but protein and phosphorous were slightly greater (less than 5%) in milk from sometribove-treated cows. Within a 14-d injection interval, animals treated with sometribove displayed a cyclic pattern in milk yield, but a similar pattern was not evident in feed intake.

The relationships of maternal nutrition and progesterone secretion to prenatal fetal loss and neonatal survival and growth were investigated in domesticated pigs that normally experience 40% fetal loss. Yorkshire pigs were subjected to prolonged starvation (40 days; 0 kcal/day; water only) in either the middle third or last third of pregnancy and then gradually realimented to a full diet and allowed to advance to parturition; controls received a full diet (7,028 kcal/day) throughout gestation. Pregnancies were maintained in 74% of the pigs starved during either middle or late gestation compared to 100% in controls. In dams starved from days 30--70, progesterone levels remained similar to controls, but were maintained at lower levels during realimentation between days 72 and 99. Progesterone levels in dams starved days 50--90 and controls were similar from days 50 to 130. At parturition, litter size in starved dams (9.4) was similar to full-diet controls (8.0) although birth weight and neonatal growth of piglets were reduced markedly from dams starved in middle or late pregnancy. These results indicate that severe maternal nutrient deprivation during the middle or last third of gestation has little effect on ovarian progesterone secretion and is not a major limitation to fetal survival in this litter-bearing species. Maternal nutrient deprivation imposes a significant detrimental effect, however, on birth weight and neonatal growth to 80 days of age.

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