Six experiments were conducted to evaluate the use of fat in diets containing a high level of milk products for weanling pigs. In Exp. 1, 192 pigs (6.6 kg and 23 d) were used to determine whether milk products (0 or 40%) in the diet influenced the utilization of fat (0 or 10%). No fat x milk product interactions were found. Adding milk products to the diet improved (P < .01) ADG, ADFI, and gain/feed (G/F). Adding fat to the diet did not influence performance. In Exp. 2, 3, and 4, 576 pigs (6.0 kg and 20 d) were used to determine the influence of fat level on performance. Adding soybean oil (0, 3, 6, or 9%) to the diet from d 0 to 14 after weaning had no influence on growth performance. Increasing soybean oil (0, 2, 4, or 6%) in the diet from d 14 to 35 had no influence on ADG; however, G/F improved linearly (P < .001). In Exp. 5, 196 pigs (7.5 kg and 26 d) were used to determine the influence of fat source (soybean oil, corn oil, or tallow) on performance. Pig performance was not different among fat sources. In Exp. 6, 240 pigs (5.4 kg and 21 d) were used to determine the influence of fat and(or) milk product inclusion in the nursery diet on subsequent grow-finish performance. Adding milk products, but not fat, to the nursery diet improved (P < .08) overall performance to market weight. These results indicate adding fat to the diet from d 0 to 14 after weaning had no influence on performance. Adding fat to the diet from d 14 to 35 improved G/F; however, it did not improve ADG or overall performance to market. Diet composition during the nursery period can affect subsequent performance.

One hundred eighty-one maternal-line (Yorkshire x Landrace x Chester White or purebred Landrace) sows were used to determine effects of dietary protein concentration during lactation on voluntary feed intake of sows and sow and litter performance. Throughout gestation, sows received 1.8 kg/d of a 14% CP corn-soybean meal diet. Sows were assigned to dietary treatments based on parity (range = 1 to 9) and expected farrowing date. Treatments were corn-soybean meal diets that contained 13.6 (Low, L), 15.5 (Medium, M), 17.5 (High, H), or 19.2 (Very High, VH) % CP. Calculated lysine content of diets was .62 (L), .76 (M), .90 (H), and 1.05 (VH) %. Sows had ad libitum access to their assigned diets from the day of parturition until weaning (24.6 +/- .46 d postpartum). Pigs were cross-fostered irrespective of dietary treatment until d 3 postpartum. Diet had a cubic effect (P < .05) on the lactational weight change of sows (L, -9.1; M, -2.1; H, -4.6; VH, .8 kg; SE = 1.57) but had no effect on change in backfat depth during lactation or on voluntary feed intake of lactating sows (x = 6.0 kg/d). Litter size at weaning (9.6 +/- .17 pigs) was similar across dietary treatments; however, diet linearly affected (P < .05) daily litter weight gain (L, 2.01; M, 2.12; H, 2.18; VH, 2.14 kg; SE = .05). Postweaning interval to estrus averaged 5.2 +/- .25 d and was unaffected by dietary treatments. Our data suggest that dietary protein concentrations between 13.6 and 19.2% do not influence voluntary feed intake of lactating sows or weaning-to-estrus interval.(ABSTRACT TRUNCATED AT 250 WORDS)

One digestibility experiment (Exp. 1) and two growth experiments (Exp. 2 and 3) were conducted to evaluate the use of lecithin as an emulsifier of soy oil and(or) an energy source in a two-phase starter diet program. Phase 1 consisted of d 0 to 14 postweaning, and Phase 2 consisted of d 14 to 35 postweaning. Diets were based on corn, soybean meal, and 20% dried whey and contained a constant ME:lysine level. In Exp. 1 and 2, two levels of lecithin (0 and 2%) at two levels of soy oil (0 and 6%) were investigated. In both experiments, there was no interaction between lecithin and soy oil for any traits measured. In Exp. 1, the apparent digestibility of fat increased significantly with increased fat level in the diets. Addition of lecithin to diets improved (P < .05) nitrogen retention, and the addition of soy oil significantly improved apparent digestibility of DM, GE, fat, and CP. In Exp. 2, there was no significant effect of lecithin or soy oil on ADG. In Phase 2 and overall, the inclusion of lecithin and soy oil to diets significantly increased gain/feed but did not significantly improve gain/ME intake. In Exp. 3, pigs were fed diets containing 0, 1, 2, or 3% lecithin. The addition of lecithin to diets did not affect ADG, ADFI, gain/feed, or gain/ME intake during Phases 1, 2, or overall. These results fail to demonstrate that the addition of lecithin to diets for young pigs improves utilization of soy oil or growth performance.

Production and reproduction records that spanned a 24-yr period were used to study the effects of low coefficients of inbreeding in two experiment station Guernsey herds. Inbreeding ranged from 0 to 25.3% and averaged 4.1%. Milk and fat yields were all first lactations standardized to a mature equivalent, twice daily milking, and 305 d. Intrasire regressions of production traits on percent inbreeding were -23.8 kg of milk, -1.25 kg of fat, and .002% for fat percentage. Estimates of the effect of inbreeding on reproductive traits had large standard errors but suggested that inbreeding depressed reproductive performance. Age at first calving decreased 3.7 d per 1% increase in inbreeding.

Data were first lactation production and reproduction records initiated from 1958 to 1981 in two experiment station Guernsey herds. Heritability estimates using paternal half sib groups were .24 +/- .12 for milk yield, .27 +/- .12 for fat yield, and .77 +/- .15 for fat percentage. Heritability estimates for reproductive traits ranged from .01 to .04 for number of services, service period, conception rate, and days open, but were higher for days in milk at first breeding (.12) and age at first calving (.13). Except for age at first calving, coefficients of additive genetic variation were larger for reproductive traits than for productive traits. Genetic correlations between measures of production and reproduction were moderate to large and antagonistic, except that the relationship between production and age at first calving was favorable. Breeding value estimates for milk yield and reproduction were negatively correlated for sires with above average breeding values for milk yield. Huge phenotypic variances for reproductive traits masked substantial additive genetic variation for these traits. When all things are considered it seems unwise to ignore reproductive performance in selection programs for dairy cattle.