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Recipient beef heifers, pregnant with single demi-embryos, were paired according to identical twin or full-sib embryo. Within pair, recipient heifers were assigned to one of two isocaloric diets containing a control or restricted level of protein (91 vs 55% of National Research Council recommendations) on d 190 of gestation. Following parturition, calves were weighed, fed 1 liter of colostrum, dried and placed in a metabolic chamber at 5 h of age for an 8-h determination of heat production (HP). Maternal body weight gains (P<.001) during the last trimester and body condition scores at parturition (P<.05) were reduced in heifers fed the protein-restricted diet. Calves born to heifers fed the protein-restricted diet had 11.4% lower (P<.05) HP than calves born to control heifers (43.7 vs 49.3 kcal•kg−1•d−1). Birth weights, respiratory quotients and rectal temperatures of newborn calves were not significantly affected by prepartum protein restriction. Within treatment groups, the relationship between HP and weight Was described by the equation: HP (kcal/d) = 2.30 wt1.86. The allometric exponent of 1.86 ± .26 implied that weight-specific metabolic rate was higher rather than lower in larger weight calves. We concluded that the thermogenic ability of neonatal calves may be compromised by prepartum protein restriction and (or) small birth weights.

Swine feces from finishing hogs were fed in two metabolism trials by substituting for 21.7 and 37.3% (dry matter) of a basal corn-soybean meal ration. Unprocessed feces (fresh) were used in one trial and dried feces were used in the other trial.Feces collected from gilts fed rations containing feces had significantly higher levels of crude fiber, ether extract and gross energy, and significantly lower levels of crude protein and true protein than feces collected from gilts fed the basal ration. The fecal concentration of ash, NFE and nonprotein nitrogen tended to remain constant as percent of feces inceased in the ration. The fecal concentration of amino acids in most cases decreased as feces were substituted. Although the intake of all minerals increased as the percent of feces increased in the ration, only the fecal concentration of magnesium, copper and zinc were significantly higher with the concentrations of calcium, phosphorus and potassium remaining about constant. Phosphorus was the only urinary component which significantly increased as the level of feces substituted in the basal ration increased. Output of feces increased as the amount of feces substituted for the basal ration was increased with no differences in urinary output.Swine feces were found to be of less nutritive value than a basal corn-soybean meal ration. Digestibilities for dry matter, energy, ash, crude fiber, ether extract, crude protein, true protein and nitrogen-free extract, calculated by difference using the percentage of that nutrient which was from feces, were: 48.0, 46.7, 31.6, 40.9, 54.1, 60.1, 51.4 and 45.9%, respectively. With the exception of serine, glycine and cystine, in which the digestion coefficients were lower, the digestibilities of the other amino acids ranged from 51.2 to 65.1%. The apparent absorption of most minerals analyzed was reduced as the level of dietary feces substituted increased (the intake of all minerals increased as feces substituted increased), but absorption and retention, in grams per day, were similar or greater as feces were substituted for the basal ration.

We compared pregnancy rates of beef cows subjected to the traditional Syncro-Mate-B®protocol or the new Ovsynch protocol and timed insemination. Multiparous Angus cows (n = 436) were stratified by age, postpartum interval, and AI sire and were randomly divided into two treatment groups for synchronization of estrus/ovulation. Approximately half of the cows (n = 216) received the traditional Syncro-Mate-B protocol with 48-h calf removal from the time of implant removal until breeding. The remaining cows (n = 220) received the Ovsynch protocol, which consists of an injection of GnRH (100 µg) on d −10, an injection of PGF2α(25 mg) and 48-h calf removal on d −3, another injection of GnRH and calf return on d −1, and timed insemination 24 h later (d 0). Blood samples were collected from all cows before treatment to identify anestrous and cyclic females. Pregnancy rates were higher (P< .025) for Ovsynch-treated cows (54%) than for Syncro-Mate-B-treated cows (42%). Pregnancy rates of cyclic Ovsynch-treated cows (59%) were higher (P< .005) than pregnancy rates of cyclic Syncro-Mate-B-treated cows (38%). Pregnancy rates of anestrous cows also tended to favor synchronization with the Ovsynch protocol. From these data, we conclude that the Ovsynch protocol is capable of inducing a fertile ovulation in cyclic and anestrous beef cows and that pregnancy rates to a timed insemination are higher than those obtained with synchronization of estrus using Syncro-Mate-B.

Eight steers from a group of 14 were fed ad libitum from 240 to 510 kg live weight, gaining at 1.4 ± .2 kg/d. The six other steers were diet-restricted and grew at .37 ± .09 kg/d from 240 to 307 kg, prior to ad libitum realimentation on the same diet to a final weight of 510 kg. Blood samples taken during the growth phases from both treatments were analyzed for insulin-like growth factor-I (IGF-I), triiodothyronine (T3), thyroxine (T4), glucose (GLU), nonesterified fatty acids (NEFA), and blood urea nitrogen (BUN) and(or) growth hormone (GH). During restricted growth, mean serum concentrations of GH were elevated (45.6 vs 23.4 ng/ml; P< .05), serum concentrations of IGF-I decreased (108 vs 167 ng/ml; P< .05) compared with control steers with ad libitum access to feed. Levels of T4and GLU also were lower (P< .05) during restricted than during normal growth. During early realimentation, levels of GLU (P< .05), IGF-I (P< .01), T4and BUN (P< .01) increased. Levels of T3remained unchanged, whereas concentration of NEFA declined (P< .001). Blood urea nitrogen decreased during early realimentation despite a large increase in diet protein intake and in protein storage, suggesting an increased efficiency of nitrogen use for protein synthesis. During realimentation, IGF-I levels rose above those of control steers and remained higher at the final weight of 510 kg (P< .05). Levels of IGF-I paralleled growth rate and may explain why GH levels can be elevated during periods of reduced growth rate in beef cattle.

Serum samples and BW were obtained from 2-yr-old beef heifers, pregnant with either single (SF, n = 12) or twin (TF, n = 7) fetuses, at 7-d intervals from d 190 of gestation until calving. Serum insulin-like growth factor I (IGF-I) concentrations of SF heifers gradually declined from d 190 (69.9 ± 1.0 ng/ml) to d 263 (55.6 ± .8 ng/ml), then exhibited a slight increase by d 277 (63.4 ± 1.1 ng/ml). Serum IGF-I concentrations of TF heifers essentially paralleled, yet were lower (P< .05) than, concentrations in SF heifers for all days tested except d 197 and 205. The SF heifers pregnant with heifer fetuses (n = 6) had higher IGF-I concentrations (P< .1) than heifers pregnant with bull fetuses (n = 6) for all days tested except d 214 and 235. Instantaneous absolute growth rate (IGR) of SF heifers declined from 1.485 kg/d at d 190 to .257 kg/d by d 277. Rate of decline in IGR of TF heifers was much greater (P< .0001). Correlations between serum IGF-I concentrations and IGR for SF and TF heifers were .79 (P< .001) and .59 (P< .05), respectively. These data suggest that number and sex of fetus influence maternal concentrations of IGF-I and that the combined growth rate of the dam and conceptus during gestation is related to serum IGF-I concentration.