Dietary yeast culture supplementation of mares during late gestation and early lactation: Effects on milk production, milk composition, weight gain and linear growth of nursing foals

This study examined the effects of dietary supplementation of pregnant and lactating mares with concentrated dried live yeast culture on the nutrient content and rate of production of milk during early lactation and on the growth of their nursing foals. Pregnant mares were fed the same diets, with or without 20 g/day of yeast culture, from 4 weeks before foaling through the eighth week of lactation. Milk production at the onset of lactation, as measured by the weigh-suckle-weigh technique, was significantly stimulated by yeast culture supplementation, although the effect was only temporary. However, the nutrient composition of mares milk was altered by continued yeast culture supplementation through at least the eighth week of lactation. Gross energy (kcal/100 g milk), sugar, fat, protein and total amino acid contents (g/100 g milk) were significantly increased. The concentrations of a number of individual amino acids tended to be greater in the milk of supplemented mares, but most of these individual differences were not statistically significant. The intakes of energy (Mcal/day), sugars, fat, protein, total amino acids, leucine, lysine, serine and valine (g/day) were significantly greater by the foals nursing supplemented mares through 8 weeks. The foals nursing supplemented mares exhibited significantly greater rates of gain by the fourth week of life, and faster growth at the withers after 6 weeks. The efficiency of converting mare feed to neonatal body mass was 24% greater in the foals of supplemented mares, These data indicate that supplementing mares with dietary yeast culture during early lactation resulted in more efficient and rapid growth of their nurslings.     

饲喂不同钙、磷水平饲粮对泌乳期伊犁马乳成分、乳脂脂肪酸组成和马驹生长发育、血浆生理生化指标的影响

本试验旨在研究饲喂不同钙、磷水平饲粮对泌乳期伊犁马乳成分、乳脂脂肪酸组成及马驹生长发育、血浆生理生化指标的影响,为进一步探讨伊犁马钙、磷营养提供参考。选取年龄、体重和胎次接近的处于第2泌乳月末的伊犁马25匹,根据母马体重和马驹体重随机分为5组,每组5匹。5组马匹饲粮钙、磷水平分别设为45.0、30.0 g/d(Ⅰ组),48.5、32.0 g/d(Ⅱ组),52.0、34.0 g/d(Ⅲ组),55.5、36.0 g/d(Ⅳ组),59.0、38.0 g/d(Ⅴ组)。试验为期90 d,每30 d为1个试验周期。结果显示:饲粮钙、磷水平显著影响每次平均挤奶量及估计日产奶量(P0.05),对乳中乳脂率、乳蛋白率、乳糖率和乳总固形物含量无显著影响(P0.05)。Ⅲ组每次平均挤奶量分别比Ⅰ和Ⅳ组提高了20.65%(P0.05)和15.22%(P0.05),而Ⅲ组乳中钙含量比Ⅰ组低21.54%(P0.05)。不同钙、磷水平饲粮对乳脂中肉豆蔻脑酸(C14∶1)、棕榈油酸(C16∶1)、亚油酸(C18∶2n6c)、花生酸(C20∶0)、顺-11-二十碳烯酸(C20∶1)和α-亚麻酸(C18∶3n3)的含量均有显著影响(P0.05);随着饲粮钙、磷水平的增加,乳脂中饱和脂肪酸含量增加而不饱和脂肪酸含量下降。母马饲喂不同钙、磷水平饲粮对马驹体重、体长、体高和管围等生长发育指标以及血浆钙、磷、甲状旁腺素、骨钙素含量均无显著影响(P0.05),而胸围则随着饲粮钙、磷水平的增加有不同程度的下降。Ⅰ组马驹血浆降钙素含量显著高于Ⅱ、Ⅲ和Ⅳ组(P0.05),分别增加34.24%、24.89%和23.64%。由此得出,增加饲粮钙、磷水平可提高伊犁马的产奶量,但使乳中钙含量降低;饲粮钙、磷水平不影响乳成分,但增加乳脂中饱和脂肪酸的含量,减少不饱和脂肪酸的含量;由于乳中钙含量降低,导致马驹血浆降钙素含量下降、胸围发育较慢。     

Effects of dietary yeast culture supplementation of lactating mares on the digestibility and retention of the nutrients delivered to nursing foals via milk

Eight pregnant Thoroughbred mares were randomly allotted to 2 diets, 4 weeks prior to their anticipated dates of foaling. The diets consisted of 30% timothy hay, 20% alfalfa hay, 17.5% whole corn, 17.5% oats, 9% barley, 2.5% molasses, 2.5% soybean mean and 1% calcium carbonate, with or without 20 g/day of a commercial yeast culture preparation. The digestibilities of dietary energy, crude protein, hemicellulose, cellulose and phosphorus were significantly greater in the supplemented mares. The supplemented mares produced 12% more milk during the third week of lactation (p<.01), and their milk contained more energy, sugars, lipids, protein and amino acids per 100 g. Consequently, their foals ingested more of these nutrients per day. The digestibilities of milk energy, nitrogen, calcium and phosphorus were not affected by yeast culture supplementation. However, because of their increased nutrient intakes the foals of the supplemented mares retained 19.6 g more nitrogen (p<.01), 2.1 g more phosphorus (P<.01) and 0.9 g more calcium (p<.05).     

Homotypic and heterotypic serum and milk antibody to rotavirus in normal, infected and vaccinated horses.

The homotypic and heterotypic antibody response to rotavirus was determined in three pony mares and their foals. The normal concentrations of anti-rotavirus antibodies in mares' milk and mares' and foals' serum over the first 10 weeks post-partum were measured using IgA, IgG and rotavirus serotype-specific enzyme linked immunosorbent assays. Experimental infection of the foals with serotype 3 equine rotavirus produced a rapid, serotype-specific response which peaked 10 days after infection and a slower heterotypic response which peaked 32 days later. In contrast, vaccination of the mares with an inactivated, adjuvanted serotype 6 bovine rotavirus produced a heterotypic response similar to that of the homotypic response in both serum and milk, although the predominant response in serum was IgG, while in milk it was IgA. These results suggest that non serotype-restricted passive protection of foals against rotavirus may be achieved by parenteral vaccination of mares.     

Fat and cholesterol content and fatty acid composition of mares' colostrums and milk during five lactation months

In this study, the effect of the lactation stage on changes in the fat and cholesterol content and fatty acid composition of colostrum and milk of Wielkopolska mares' was investigated. Colostrum and milk samples from 10 lactating mares were collected at the beginning of lactation, on the 1st and 2nd day after foaling and then, starting from the first month of lactation, at 4 weeks' intervals up to the fifth month of lactation. Statistically significant differences were found between mares' colostrum and milk in the fat and cholesterol content as well as in the percentage rate of total fatty acids which occurred in significant quantities. Together with the lengthening of the lactation time, the content of fat and cholesterol in the mares' milk was observed to decrease. The authors also found a significant impact of the lactation period on changes in the ratio of polyenoic fatty acids from the n-6 to n-3 family. Bearing in mind the fat and cholesterol content and a more favourable (from the nutritional point of view) ratio of fatty acids from the family of n-6 to n-3, it is recommended to collect milk from mares in the 4th and 5th month of lactation.     

Milk and water intakes of foals sucking grazing mares.

Intakes of milk and milk nutrients were determined for 8 foals at 11-18 days of age and for 10 foals at 30-44 days and 60-74 days of age while sucking grazing mares. Water intakes (sources other than milk) of the foals were determined at 30-44 days and 60-74 days of age. Five of the 10 mares were fed a protein supplement (24% crude protein) in addition to grazing during the stud season. The protein supplement did not influence foal intakes of milk and milk nutrients, milk composition, weight gains of the mares or the growth rate of the foals. Foal milk intakes increased (P less than 0.05) from 16.9 kg/day at 11-18 days to 18.1 kg/day at 60-74 days of age. The water intakes of the foals increased (P less than 0.01) from 3.9 kg/day at 30-44 days to 5.5 kg/day at 60-74 days of age. Total fluid intakes per kg foal liveweight were 246, 202 and 172 g at 11-18, 30-44 and 60-74 days of age, respectively. For each kg of weight gain, foals consumed 12.8, 15.7 and 16.4 kg milk at 11-18, 30-44 and 60-74 days of age. Stage of lactation had a significant effect on the total solids, lactose and protein content of milk. The fat and gross energy content of milk remained constant.     

Lactation and reproductive performance of mares fed added dietary fat during late gestation and early lactation

Eighteen pregnant mares were randomly allotted to one of two treatment groups. The control group was fed a conventional concentrate and the fat group was fed a concentrate containing 5% feed-grade rendered fat. Both concentrates had the same nutrient:calorie ratio and were fed in amounts required to maintain zero change in percent body fat of the mares. During the study, which began 60 d prior to expected foaling date and ended 60 d postpartum, mares were monitored for feed intake, body weight, rump fat thickness, ration digestibility, plasma glucose and lipid concentrations, milk composition and reproductive efficiency. Birth weight, growth rate, and plasma glucose and lipid concentrations were also measured in foals. Mares fed fat consumed less concentrate (P<.09 during the last 60 d of gestation but consumed similar amounts of concentrate over 60 d of lactation. Protein and ether extract digestion was higher (P<.05 and P<.09, respectively) in the mares fed fat during the postpartum period. Dietary treatment had no influence on plasma glucose or lipid concentrations of the mares or plasma glucose concentrations of their foals, but foals whose dams were fed fat had higher plasma lipid concentrations at birth (P<.01), d 10 and d 30 (P<.05). Percent fat was higher in milk samples from mares fed fat at d 10 (P<.09, 1.23 vs .99%) and d 60 (P<.01, .72 vs .43%) of lactation. Reproductive performance was not significantly different between treatment groups, however there was a trend for a shorter postpartum interval and fewer cycles per pregnancy in the mares fed added fat. Foals from both groups were of similar size and weight at birth and had similar weight gains over 60 d, however, foals nursing mares fed fat tended to gain more weight in the first week of life (1.85 vs 1.56 kg/d) and have more rump fat at d 60 (.53 vs .44 cm) than foals nursing control mares.     

A first estimate of the amino acid requirement for milk production of the high-producing female mink (Mustela vison)

Thirty mink dams nursing litters of six kits were assigned to one of three dietary treatments [high protein (HP), medium protein (MP) and low protein (LP)], fed ad libitum for 4 week from parturition, to investigate the effects of protein supply on milk yield and milk composition in order to estimate the amino acid requirement of the lactating mink. Twelve dams were held in an intensive care unit and subjected to balance experiments and the kits were injected with deuterium oxide to determine water kinetics and milk yield. Eighteen dams were kept under normal farm conditions but with feed intake of dams and live weight gain of kits being determined and milk samples collected. The ME intake was higher (p < 0.05) in dams fed the LP and MP diets than in dams fed the HP diet, whereas the amino acid intake (g/day) was lowest (p < 0.05) in dams fed the LP diet. In the third and fourth weeks of lactation milk yield was higher (p < 0.05) in dams fed the LP and MP diets than in dams fed the HP diet. Chemical composition of milk was not affected (p > 0.05) by dietary treatment. However, protein content tended (p = 0.06) to be lower in dams fed the LP diet. Amino acid content (g/16 g N) of milk was higher (p < 0.05) in dams fed the LP and MP diets than in dams fed the HP diet. This resulted in the highest (p < 0.05) amino acid intake and highest (p < 0.001) live weights of kits nursed by dams fed the LP and MP diets, which may be explained by a combined effect of higher ME intake and reduced energetic costs for glucose production through less amino acids being used in gluconeogenesis. In conclusion, the improved performance of dams fed the LP diet suggested that their requirement of essential amino acids and non-specific N were covered, and the requirement of digestible amino acids of lactating mink (kg(0.75)) was, thereby, estimated by use of a factorial approach including the amino acid excretion in milk of LP dams.     

Blood metabolite profiles of broodmares and foals

Serum amino acid profiles and other serum characteristics of broodmares and their foals wee studied. Compared with mares, foals had significantly higher concentrations of serum leucine, threonine, aspartic acid, asparagine, glutamic acid, glutamine, proline and tyrosine, glucose, cholesterol, creatinine and phosphorus. Foals had significantly less serum histidine, glycine, cystine, taurine, protein and urea nitrogen. Lysine and/or methionine supplementation of pregnant and lactating broodmare diets were conducted. Changes in serum amino acid profiles caused by dietary amino acid supplemented were then quantified. Changes in concentrations of 19 amino acids as well as of ammonia occurred from the first bleeding period (12 weeks prepartum) to the second bleeding period (seven weeks prepartum) in mares supplemented with methionine. When blood samples were collected at 2 h intervals post feeding, after a preliminary rise, a large decrease in serum amino acid levels occurred over a 19 h pot feeding period.     

Nitrogen balance in lactating sows fed on diets containing soybean oil meal or horsebean (Vicia faba) as a protein concentrate

An experiment was carried out on multiparous sows to study the possibility of total substitution of soybean oil meal by whole horsebean in the lactation diet. Two groups of five sows were kept in metabolism crates during a 5-week long lactation, and their total excreta were collected for 5 days each week. The animals received a diet mainly composed of barley, in which the protein concentrate was soybean oil meal (“soybean” group), or whole horsebean (“horsebean” group) supplemented with d-l methionine (Table I). The two diets were isonitrogenous (14% protein). Milk production and gros composition were estimated at different stages of lactation. The amino acid content of the milk and the plasma level of free amino acids were determined around day 21 of lactation.The performance of the two groups of sows were similar (Table II): the litters were equalized at farrowing, the number of piglets weaned (8.8) and their mean weight at different stages of lactation were identical. Milk production, composition (Table III) and amino acid content (Table IV), and the output of milk constituents were similar. There was some tendancy for the apparent protein digestibility of the “soybean” diet to be higher (81.5% vs 79.6%), partly due to the greater digestibility of dry matter (82.3% vs 81.8%) caused by the lower crude fibre content of this meal. The nitrogen retention coefficient and nitrogen production in the milk were the same in the two groups of sows (Table V). The amino acid availability, estimated with the plasma level of free amino acids, did not show important differences between the diets. The similarity of the results allows the conclusion that whole horsebean supplemented with d-l methionine can be used as the sole protein concentrate in the diets of lactating sows. Moreover, the null nitrogen balances obtained during lactation with a daily intake of 700 g protein may lead to a possible lowering of the protein recommendations, while insisting on the energy supply during the same period.     

Influence of Ruminally Undegraded Protein and Zinc Methionine on Milk Production,Hoof Growth and Composition,and Selected Plasma Metabolites of High Producing Dairy Cows

Thirty-six first or later lactation Holstein cows were grouped according to their 305-d mature equivalent milk yield and used in a 240-d 2 × 3 factorial design experiment. Objectives were to determine the effect of supplemental Zn-Met and ruminally undegraded protein (RUP) on milk production, hoof growth and composition, and selected plasma metabolites of high producing dairy cows. During the dry period, cows received rations supplemented with 1) ZnSO₄ (DT1) or 2) Zn-Met (DT2). Treatments during lactation were 1) soybean meal (SBM) (LT1), 2) ZnSO₄-treated SBM (LT2) (Consolidated Nutrition L. C., Ft. Wayne, IN), and 3) ZnSO₄-treated SBM plus supplemental Zn-Met (LT3) (Zinpro Corp., Eden Prairie, MN). All rations were formulated to contain equal amounts of Zn. Cows receiving DT1 had higher 3.5% fat-corrected milk (FCM) and milk fat percentage when compared with those receiving DT2 (P<0.05). Hoof growth was greater during the dry period for cows receiving DT2 (0.22 mm/d) than for those receiving DT1 (0.20 mm/d). The ZnSO₄-treated SBM and LT3 had no effect on hoof growth during lactation. Mean hoof CP content was lowest at peak lactation (85.6%) and highest at calving (90.4%). Cows receiving LT3 had the highest hoof Zn content during lactation. Glucose was higher later in lactation and at feeding; whereas, insulin and plasma essential amino acids (AA) were highest at peak lactation. For high producing dairy cows, especially those with hoof problems, supplemental RUP and Zn-Met may provide nutrients needed for hoof growth and increase production by helping maintain hoof health and DMI.     

Donkey Feeding During Maintenance,Pregnancy, and Lactation: Effects on Body Weight,Milk Production,and Foal Growth

We evaluated the daily intake in donkeys during maintenance, late pregnancy, and early lactation. The growth curves of the foals in the first eight weeks of life and the milk production in lactating jennies were also investigated. Donkeys were separated into two groups: seven pregnant jennies (group 1: pregnant/lactating) and seven nonpregnant, nonlactating jennies (group 2). The groups were fed two different diets each. The feeding period for group 1 covered eight weeks before parturition and eight weeks postpartum. Group 2 was managed during the same time period (16 weeks). Diet 1 consisted of ad libitum hay, which was fed to group 1 during late pregnancy and to group 2 from weeks 1–8. Diet 2 consisted of the same ad libitum hay supplemented with 2 kg/head/day of concentrate, which was fed to group 1 during lactation and to group 2 from weeks 9–16. The daily dry matter intake (diet 1) was 2.56 kg/100 kg of body weight (BW) for nonpregnant jennies and 31% lower in the pregnant donkeys. In the lactating jennies, the total dry matter intake was similar to the nonpregnant group fed diet 2. The nonpregnant jennies lost 1.9% of their initial BW when fed diet 1, whereas they gained 8.4% of their initial BW when fed with diet 2. A weight loss was also found in the lactating donkeys. The foals more than doubled in their birth weight within two months.     

Escape protein for beef cows: I. Source and level in corn plant diets

Two gestating cow winter grazing trials and two lactating cow drylot trials were conducted to evaluate the use of a slowly degraded protein source in corn plant diets for mature beef cows. Gestating beef cows grazing cornstalks were supplemented with .86 kg/(cow.d) of a 20% crude protein equivalent (CPE) pellet (DM basis). In Trial 1 cows fed diets containing 80% dehydrated alfalfa meal (high DEHY) gained more weight (P less than .05) than those fed diets containing 40% dehydrated alfalfa meal (low DEHY) or urea but not more than the cows fed soybean meal (SBM); however, no differences among treatments were observed in Trial 2. Four lactation diets composed of ground corncobs and corn silage were supplemented with either urea, SBM, or two levels of dehydrated alfalfa meal (DEHY) as N sources. The same amount of supplemental N was fed in both trials, consisting of .31 kg of natural protein for the SBM and low DEHY treatments or .42 kg for high DEHY. Ammoniated corncobs replaced 35% of the ground corncobs in Trial 4. Diets were calculated to contain (DM basis) 55% TDN and 9% CPE in Trial 3 and 11% CPE in Trial 4. In Trial 3, lactating cows supplemented with DEHY gained more weight (P less than .10) than those fed the urea supplement but not more than those fed SBM. Gains by cows fed the urea- and SBM-supplemented diets were not different (P greater than .10). Cow weight gains in Trial 4 were not affected by type of protein supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)     

不同品种泌乳母马不同泌乳月产奶量及乳成分的比较

[目的]研究伊犁马和哈萨克马泌乳母马在不同泌乳月产奶量及乳成分的差异,为开发利用伊犁马和哈萨克马乳用特性提供参考。[方法]随机选择年龄和胎次相近、产驹时间接近、健康的伊犁母马和哈萨克母马各12匹,在日粮营养水平和饲养管理水平相同的条件下,记录2个品种母马在泌乳30、60、90 d的产奶量;采集乳样,测定2个品种母马不同泌乳时间的乳中体细胞数、乳脂率、乳蛋白率、乳糖率和总固形物含量。[结果]泌乳30 d时,哈萨克马的产奶量高于伊犁马（P>0.05）,乳脂率极显著（P<0.01）高于伊犁马,乳中体细胞数显著（P<0.05）高于伊犁马,其他乳成分指标高于伊犁马（P>0.05）。泌乳60 d时,伊犁马的产奶量和乳糖率极显著（P<0.01）高于哈萨克马,乳脂率和乳蛋白率高于哈萨克马（P>0.05）,乳中体细胞数和总固形物含量低于哈萨克马（P>0.05）。泌乳90 d时,伊犁马的产奶量显著（P<0.05）高于哈萨克马,乳糖率、总固形物含量极显著（P<0.01）高于哈萨克马,乳脂率和乳体细胞数极显著（P<0.01）低于哈萨克马,乳蛋白率高于哈萨克马（P>0.05）。[结论]泌乳初期（30 d）,哈萨克马的产奶量和乳营养成分含量高于伊犁马;泌乳中期（60、90 d）,伊犁马的泌乳性能整体优于哈萨克马。在观察期内,哈萨克马的乳体细胞数大于伊犁马。     

Evaluating the suitability of field beans as a substitute for soybean meal in early-lactating dairy cow: Production and metabolic responses

Twenty-four multiparous Holstein cows were utilized in a completely randomized design to examine the effect of feeding field beans (FB, Vicia faba L. var. minor) as substitute for soybean meal (SBM) on lactation performance and metabolic response during the early lactation period. Cows were individually divided into two equal groups and fed for 16 weeks on one each of the two experimental diets. The controls were fed pelleted concentrate contained 150 g/kg dry matter (DM) of SBM as the main protein source, whereas the experimental concentrate contained 345 g/kg DM of FB. Oat hay was offered ad libitum to cows and water was freely available. Blood samples were assayed for their content of: urea, glucose, triglycerides, cholesterol, total protein, albumin, calcium and phosphorus, aspartate aminotransferase (AST) and alanine aminotransferase (ALT), nonesterified fatty acids (NEFA) and β-hydroxybutyrate (BHBA). Inclusion of FB had no detectable effects on DM intake (DMI), body weight (BW), or body condition score (BCS). Neither milk yield nor quality were influenced by dietary treatment, except for milk urea nitrogen (MU) that was reduced in cows fed the FB diet (P < 0.05). Clotting properties of milk were not affected adversely by added dietary FB. Concentration of blood urea (BU) was lower in cows fed the FB diet than in those fed the control SBM diet (P < 0.05). These findings indicate that feeding FB in a lactation diet supported lactation performance similar to cows fed traditional SBM-based diet, and the results may elicit great interest for countries where soybean utilization is adversely influenced by high supply costs.     

Importance of milk replacer intake and composition in rearing orphan foals

Effects of milk replacer composition and intake on the growth of orphan foals were evaluated. Twenty foals were assigned to four treatments: 1) mare-nursed, 2) commercial foal milk replacer at recommended intakes (standard), 3) commercial foal milk replacer at high intakes (high), and 4) acidified replacer at recommended intakes (acidified). Foals fed milk replacer diets were weaned at 12-24 hours postpartum and fed milk replacer for 50 days. Mare-nursed foals were weaned between 52 and 56 days of age. Foals fed replacer diets gained 12% to 28% less weight than mare-nursed foals up to two weeks of age. However, by four months of age, weights of replacer-fed foals were similar to those of mare-nursed foals and 32 other mare-nursed foals at the farm weaned between three and four months postparium. Foals drank 10 to 12 L/100 kg body weight (BW) in fluid replacer daily over the trial period. During the first week, high intake foals consumed 26% more replacer (p<0.05) than foals fed acidified or standard diets. This higher intake resulted in diarrhea earlier (6-11 days vs 11-22 days) and for a longer time (6.3 days vs 2.5-3.6 days) than in foals fed recommended amounts. Mare-nursed foals developed “foal heat scours” in the second week postpartum. After the first week, foals fed high replacer diet voluntarily consumed the same volume of fluid replacer as foals fed the standard intake. Foals ate less than 1 kg grain mix/100 kg BW daily to one month of age, then increased intake to 1.5-2 kg/ 100 kg BW to weaning. Water intake was 20-40% of daily fluid intake and was correlated (r = 0.85) to dry matter intake. Foals in the high intake group ate less (p<0.05) solid feed and drank less water than foals fed the standard and acidified diets. The foal's stomach capacity appears to limit meal size and thus replacer intake. If recommended feeding intervals are used, replacer intakes by foals are less than 15% BW daily. High volume intakes appeared to prolong diarrhea. Normal growth rates occur when replacer and good-quality feeds are fed concurrently.     

Supplemental silicon increases plasma and milk silicon concentrations in horses.

The primary objective of this research was to determine the effect of supplemental dietary silicon (Si) on plasma and milk Si concentrations of lactating mares and the subsequent effect on plasma Si concentrations in nursing foals. Additionally, the role of Si on altering biochemical markers of bone turnover was investigated, because supplemental Si may be advantageous in enhancing bone health. Twelve Arabian mare/foal units were pair-matched by foaling date and randomly assigned to two groups, Si-supplemented (Supplemented) or control (Control). Blood and milk samples were taken on d 0, 15, 30, and 45, d 0 being the 1st d after parturition. Plasma and milk (or colostrum) Si concentrations were determined and serum was analyzed for osteocalcin, carboxy-terminal pyridinoline cross-linked telopeptide region of type I collagen, and pyridinoline and deoxypyridinoline crosslinks. All Supplemented mares had higher (P < 0.01) plasma Si concentrations than Control by d 30, and Supplemented mares' milk had higher (P < 0.01) Si concentrations on d 45 than Control mares' milk. By d 45, foals of Supplemented mares had higher (P < 0.01) plasma Si concentrations than foals of Control mares. Supplemental Si did not influence (P > 0.36) bone metabolism in foals; however, trends (P < 0.10) for altered bone metabolism were observed in postpartum mares. Results indicate that supplemental Si increases plasma and milk Si concentrations. Further research is required to determine whether Si has a role in altering serum biochemical markers of bone and collagen activity.     

Nutritional value and physiological effects of soya-free diets fed to rats during growth and reproduction

The objective of the study was to assess the effects of substitution milk and egg for soya products in breeding diets for rats, with concomitant decrease of the dietary protein level and supplementation with amino acids. Soya-containing (S) and two soya-free (NS and NSA) diets were evaluated as protein and energy sources, and their effects on reproductive performance during two cycles, and on the quality of the offspring were assessed. Organ weights were registered in females and blood parameters were determined in males. In the offspring males from S and NS groups, plasma LH, testosterone and prolactin levels were measured on the 22nd and the 60th day of life. The S diet contained more protein of smaller concentration of methionine and cystine and lower biological value than both NS and NSA diets and promoted similar post-weaning growth rate, similar body weight changes of dams during gestation and lactation and slightly lower mating efficiency. Within each reproductive cycle, the number and individual and total body weight of newborn and weanling pups did not differ but in two cycles mean number of neonates per litter and mean litter weight were significantly lower on S than on NSA diet. Plasma concentration of hormones did not differ in 22-day-old offspring males while in the older ones LH and prolactin levels were higher in animals fed on S than on NS diet. It is concluded that replacing soya protein by milk and egg protein with concomitant lowering dietary protein level and amino acid supplementation does not impair the growth rate and tends to improve reproductive performance. Feeding soya-free vs. soya-containing diets differentiates hormonal status of young males.     

Epidermal growth factor-like activity in mares' milk.

Epidermal growth factor (EGF)-like activity was measured in mares' colostrum and milk by radioreceptor assay. Milk samples were collected from 22 mares 1 or more times during early lactation. Samples of colostrum were taken after parturition and before the foal first suckled (presuckle), within 6 hours after the foal first suckled (postsuckle), and on days 1, 2, 4, and 8 of lactation. In the 5 mares from which milk samples were obtained at each sampling time, presuckle colostral mean EGF-like activity (17.8 ng/ml) was greatest (P less than 0.05). The mean values for EGF-like activity at all other sampling times were not significantly different from each other (postsuckle colostrum, 9.7 ng/ml; day 1, 9.6 ng/ml; day 2, 8.5 ng/ml; day 4, 8.0 ng/ml; day 8, 7.8 ng/ml).     

Matua bromegrass hay for mares in gestation and lactation

Matua bromegrass hay (Bromus willdenowii Kunth) is a high quality forage, but its value for mares during gestation and lactation is not well known. Intake, rate of passage, performance, and reproduction by gestating and lactating Quarter Horse mares fed the hay was investigated. In this experiment, 12, 2- to 12-yr-old gravid mares (mean BW = 553 kg, SD = 36) were fed Matua hay (CP = 11.5%) or alfalfa hay (Medicago sativa L.) (CP = 15.4%) for variable days prepartum (mean 59.9 d; SD = 23.5) and for 70 d postpartum. Matua and alfalfa hay were fed as the roughage portion of the diet with a grain supplement. Mares, blocked by age, expected date of foaling, and BW, were assigned randomly within blocks to treatments (six mares per treatment). Forage type did not affect intake, gestation length, birth weight, number of foals, foal weight gain, day of first postpartum ovulation, cycles per conception, or pregnancy rate at 70 d. On d 1, milk from mares fed alfalfa hay contained less (P < 0.03) CP than milk from mares fed Matua hay. Milk CP decreased (P < 0.01) in all mares over time. In a separate experiment, voluntary intake and rate of passage of Matua (CP = 15.5%), alfalfa (CP = 24.9%), and Timothy (Phleum pratense L.) (CP = 4.1%) hays were determined in nine 2-yr-old pregnant mares (mean BW = 447 kg; SD = 21). Diets were 100% forage. Timothy hay did not meet CP requirements for mares. Voluntary intake of alfalfa hay was higher (P < 0.01) than Matua hay. Intake of Timothy hay was lower (P < 0.01) than the mean of alfalfa and Matua hay. Rate of passage offorage was measured by passage of Cr-mordanted fiber. Passage rate and retention time did not differ between Matua and alfalfa hay; however, the retention times of Matua and alfalfa hays were shorter (P < 0.01) than for Timothy hay. Our results indicate that Matua hay is a forage that can be used safely for mares during gestation and early lactation and for their young foals.