Lactation Weight Research Articles

The effects of supplementation with sunflower and soybean oils on the fatty acid profile of milk fat from grazing dairy cows

The objective of this study was to observe the effect of supplementation with vegetable oils (VO) on the fatty acid profiles and conjugated linoleic acid (CLA) content of milk fat. Twelve dairy cows in mid lactation fed on pasture were blocked by body weight, milk production and days in lactation and randomly allocated from blocks to 3 treatments repeated in a Latin square design with periods of 28 day duration. The treatments were as follows: cows on pasture supplemented with 5 kg concentrate per head per day (C), supplemented with 4.5 kg concentrate + 0.5 kg sunflower oil per head per day (SFO) and supplemented with 4.5 kg concentrate + 0.5 kg soybean oil per head per day (SBO). The animals were grazed as a group and were stocked at 2.5 heads per hectare. The treat- ments had no effect on milk yield or protein yield and content, but decreased milk fat yield and content (P < 0.05). Milk fat from the cows supplemented with VO had a lower concentration of short and medium chain fatty acids (P < 0.05) and a higher concentration of long chain fatty acids (P < 0.05). The addition of VO to the diet also resulted in a reduction in saturated and an increase in unsaturated fatty acids of milk fat (P < 0.05). The hypercholesterolemic fatty acids in milk fat (i.e. C12:0, C14:0 and C16:0) decreased while the concentration of oleic and linoleic acids increased with VO (P < 0.05). There was no effect on linolenic acid. Finally, the inclusion of VO in the diet increased (P < 0.05) the contents in milk fat of the various cis/trans isomers of oleic acid (including trans-vacenic, TVA) and of CLA which increased by 61%. dairy cow / conjugated linoleic acid / fatty acids / pasture / vegetable oils

Zum Einfluss des Tier-Fressplatz-Verhältnisses in der Gruppenhaltung tragender Sauen bei ad libitum Fütterung auf Gesundheit, Verhalten und Leistung

Abstract. Title of the paper: Influence of animal/feeder-trough space ratio on health, behaviour and performance of group housed sows fed ad libitum The EU-Directive on the "Minimum requirements for the protection of pigs" prohibits the housing of gestating sows in individual crates. One alternative to individual housing of restricted fed sows is group-housing with ad libitum access to feed. The proposed animal/feeder-trough space ratio of 4:1 in the German legislation was taken from housing systems for growing pigs due to a lack of scientific data on sow to feeder-trough space ratios. The aim of this study was to evaluate practically meaningful animal/feeder-trough space ratios with respect to animal welfare. Therefore, different animal/feeder-trough space ratios between 8:1 and 20:1 were investigated on three farms. The behaviour at the feeder, as well as health (body scoring), weight gain, back fat thickness and fertility were recorded in gestating sows between days 35 and 110 of pregnancy. The frequency of aggressive interactions and displacements at the feeder was progressively reduced in all tests after grouping the sows. Furthermore, the results pointed out that narrowing the animal/feeder-trough space ratio positively influenced both the conditioning of the sows before lactation and birth weights of the piglets. No clear trend between the different animal/feeder-trough space ratios of group-housed sows was found for the total number born, live and dead born piglets. A small number of sows showed minor injuries, which are not unusual for group housing systems. The evaluated animal/feeder-trough space ratios did not show indications of an impaired well-being of the sows. Our data do not support the legal demand for a threshold of 4:1 for the animal/feeder-trough space ratio. However, further studies with varying group sizes, group densities and animal/feeder-trough space ratios are needed in order to provide detailed recommendations on acceptable ratios.

A regional evaluation of chromium tripicolinate supplementation of diets fed to reproducing sows1,2

A cooperative research study involving 353 litters was conducted at three stations to determine the effects of graded levels of supplemental Cr from chromium tripicolinate (CrPic) on reproductive performance of sows and preweaning performance of their pigs. Primiparous and multiparous sows were fed fortified corn-soybean meal diets with supplemental levels of 0, 200, 600, or 1,000 ppb Cr (as-fed basis). Each station used at least three of the supplemental Cr levels, with two of those levels being 0 and 200 ppb. Station effects were observed for sow gestation weight gain, lactation weight change, lactation feed intake, litter size at birth and weaning, and pig weight at birth and weaning (P = 0.001 to 0.087). Supplemental Cr increased the number of pigs born live per litter (9.49, 9.82, 10.94, and 10.07; quadratic, P = 0.05) and sow lactation weight change (-0.2, 0.8, -4.1, and -3.9 kg; linear, P = 0.01) but decreased individual birth weight of total pigs born (1.61, 1.57, 1.47, and 1.56 kg; quadratic, P = 0.10). Tissues were obtained from a subset of sows from one station after they had completed three parities on the study. The content of Cr in the adrenal gland (16.4, 20.0, 34.0, and 48.4 ppb), kidney (35.8, 56.4, 132.6, and 176.0 ppb), and liver (22.8, 37.4, 87.6, and 92.2 ppb) was increased linearly (P = 0.001 to 0.005) by increasing CrPic supplementation. The results suggest that the supplementation level that maximizes the biological response is above that currently allowed. Additionally, supplementation of Cr at 1,000 ppb (five times currently permitted supplementation levels) was not detrimental to sow performance, even when fed continuously for three parities. There may be merit to continued research to evaluate higher supplementation rates.

Effects of a novel carbohydrate and protein source on sow performance during lactation.

Ninety-one primiparous and multiparous sows and their pigs were used to evaluate the effects of a novel carbohydrate- and protein-based feed ingredient (Nutri-Pal, NP) on sow and litter performance during lactation. Nutri-Pal is a feed supplement for sows that consists of a blend of milk chocolate, brewer's yeast, whey products, and glucooligosaccharides. The dietary treatments consisted of a corn-soybean meal control and a corn-soybean meal plus 5% NP fed from d 110 of gestation to weaning. The diets were formulated to be equal in total Lys and ME. Sows were allotted to treatment based on parity, body weight, and the date of d 110 of gestation. There were 46 and 45 sows per treatment over four farrowing groups. Litters were standardized to 10 pigs and weighed within 1 d of farrowing, and all sows weaned at least 8 pigs at an average age of 21 d. Sows were weighed on d 110 of gestation, d 1 postfarrowing, and at weaning. Sows were fed three times daily during lactation. Sows were checked twice daily after weaning for signs of estrus. The weaning weight of sows fed NP was increased (P < 0.10) compared with those fed the control diet. Sows fed the control diet tended (P = 0.11) to lose more weight per day from d 110 of gestation to weaning than the sows fed NP. Otherwise, sow response variables (sow weight on d 110 of gestation and d 1 postfarrowing, d 110 of gestation to d 1 postfarrowing and lactation weight change per day, d 110 of gestation to d 1 postfarrowing, lactation, and total feed intake, days to estrus, pigs born alive or dead, and litter and average pig birth weight) were not affected (P > 0.10) by diet. There were no effects (P > 0.10) of diet on litter performance response variables (pigs weaned, litter and average pig weaning weight and gain, and survival percent). The NP feed ingredient had minor effects on sow productivity, but it did not affect litter productivity indices.

The effects of cold exposure, food allowance and litter size on immunity of periparturient sheep toTeladorsagia circumcinctaand Trichostrongylus colubriformis

AbstractSixty twin- and 60 single-bearing ewes were used in a 2 ✕ 2 ✕ 2 factorial design incorporating nutritional and shearing-cold exposure treatment (no. = 15 per subgroup) to study the effects on periparturient immunity against nematode infection. From week –8 to week –4 relative to parturition, animals grazed ryegrass-white clover pastures at allowances designed to provide either 0·8 (low allowance) or 1·2 (high allowance) of estimated metabolizable energy requirement for a ewe carrying 1·5 lambs. During week –4, half the sheep from each reproductive effort and nutritional group were shorn and exposed to artificial wind and rain for 4 h on each of 4 days consecutively. During the same week, all animals were challenged twice with 1·5 ✕ 104Teladorsagia circumcincta and 1·5 ✕ 104Trichostrongylus colubriformis infective third stage larvae to supplement the natural infection from pasture. From week –3 to week + 5 relative to parturition the sheep were run together and offered pasture at rates estimated to enable them to meet their nutrient requirement.Shearing and cold stress reduced ewe body weight (by up to 4·66 kg per sheep), and temporarily reduced the levels of IgA against T. circumcincta (by proportionately 0·24) and T. colubriformis (0·34), and raised faecal egg count (1·6 to 4·4 fold) but did not affect the parasite-specific total antibody levels in the serum. The low allowance during pregnancy was associated with a 6·09-kg decrease in ewe body weight, decrease in the levels of total antibody and of IgA against both T. circumcincta and T. colubriformis, and increased faecal egg count (by 1·5 to 10·6 fold) during pregnancy and lactation. Faecal egg count was consistently higher (up to 8·8 fold) in twin-bearing and rearing ewes than in single-bearing and rearing ewes except during the first 4 weeks of the experiment. A significant effect of litter size on antibody levels was relatively small when compared with short-term changes (reductions) in antibody levels immediately around parturition. There were significant negative correlations between faecal egg count during late pregnancy and ewe body weight in lactation and significant negative correlations between the levels of total antibody against T. colubriformis and faecal egg counts near the end of the experiment. We conclude that litter size is likely to have greater influence on the resistance of ewes to nematode infections in the periparturient period than either pasture allowance or cold stress within the range of parameters used in this work.

Rumen-protected choline administration to transition cows: effects on milk production and vitamin E status.

We investigated the influence of rumen-protected choline (RPC) supplementation on milk production, lipid metabolism and vitamin E status in dairy cows receiving a silage-based diet. Twenty-six Italian Holstein multiparous cows were assigned by weight and average production in the previous lactation, to one of two groups: control (no RPC supplementation) and RPC (supplemented with 20 g/day rumen-protected choline chloride). Treatment began 14 days before expected calving and continued for 30 days after parturition. Choline administration significantly increased milk production during the first month of lactation and also the concentration (and total secretion) of choline in milk, but did not affect fat or protein concentrations in milk, or plasma levels of glucose, beta-hydroxybutyrate, cholesterol and non-esterified fatty acids (NEFA). However, around parturition, NEFA concentrations in plasma were lower in treated animals than in controls, suggesting improved lipid metabolism as a result of choline supplementation. Choline supplementation also increased alpha-tocopherol plasma concentrations, suggesting a novel aspect in dairy cows.

Metaanalysis of Input/Output Kinetics in Lactating Dairy Cows

The kinetics of dry matter intake, raw milk yield, milk fat yield, and body weight of 140 treatment groups of cows reported in 37 articles published between 1959 and 1999 were collected in a database. The majority of these experiments were performed with Holstein-Friesian cows (primiparous: n=51, multiparous: n=89). Animals were fed with forages and concentrates, offered separately (n=98) or as a total mixed ration (n=42). Empty body weight was calculated assuming that an increase of 1kg in dry matter intake corresponded to an increase of 4kg in gastrointestinal tract content. Each kinetic, denoted Y, was fitted with the model proposed by Grossman (1999) for raw milk yield. This model allowed the partitioning of the kinetic into three stages (early, middle, and late stages of lactation), each characterized by its own linear tendency. Kinetics were therefore summarized with parameter estimates of the model: the plateau value of Y in middle stage, the slopes of Y in early and late stages, and the weeks of start and end of the middle stage. The following additional variables were also calculated: the total increase of Y in early stage, the extrapolated value of Y at calving, and the persistency of Y defined as the duration of the middle stage. Variability of these parameters for each kinetic across treatment groups was examined through mixed models including the year of publication as covariate, parity as a fixed between-group factor, and trial as a random factor. Correlations between parameters within a Y-kinetic and between different Y-kinetics were calculated by parity group and feed allocation system. Finally we propose predictive models which emphasized (1) the effect of empty body weight at calving on the depletion of empty body weight in early lactation, (2) the incidence of the kinetic of dry matter intake on the kinetic of raw milk yield in middle and late stages of lactation, and (3) the relationships between the kinetics of raw milk yield and milk fat yield in middle and late stages of lactation.

Restricted suckling of tropical dairy cows by their own calf or other cows' calves.

The objective of this study was to compare restricted suckling of tropical cows by their own or another cow's calf with artificial rearing of the calves and no suckling. In Exp. 1, cows were mechanically milked twice daily, after which for 15 min they were either suckled by their own calf (Treatment O) or multiple-suckled by other cows' calves (Treatment M) or unsuckled, with the calves reared artificially (Treatment A). Machine milk yield was similar for the three treatments, but in the two suckling treatments the additional milk consumed by the calf increased (P = 0.02) total production (2,682, 2,634, and 2,336 kg/lactation for Treatments O, M, and A, respectively). Machine milk fat concentration was reduced (P = 0.05) by suckling (2.90, 3.07, and 3.20% for Treatments 0, M, and A, respectively), but the milk sampled just before suckling (to represent that taken by the calves) had a high fat concentration (mean 7.9%). Machine milk somatic cell count was also reduced (P = 0.05) by suckling, from 106,000/mL (Treatment A) to 85,000/mL (Treatment M) and 95,000 (Treatment O). Cows suckling their own calf lost more weight and body condition than cows whose calves were reared artificially, with multiple-suckled calves intermediate. Cows suckling their own calf had postpartum interval to first estrus increased (P = 0.01) by 31 d and conception rates to first service of 44% compared to 77% for the other two treatments (P = 0.01). The growth of the suckled calves was compared with that of the artificially reared calves, which were given recommended milk allowances. The artificially reared calves consumed more milk and concentrates, which were available ad libitum to all calves, and gained (P = 0.03) 0.07 kg/d more weight than suckled calves. A second experiment determined that suckling once daily did not reduce reproductive performance compared to artificial rearing. We conclude that suckling cows twice daily increases total milk production but reduces body weight in early lactation. Cows suckling their own calves have reduced reproductive performance compared to those suckling other calves or reared artificially.

Effect of dietary methionine to lysine ratio on lactation performance of first and second parity Yorkshire and Hampshire lean genotype sows

A total of 196 Yorkshire (Y) sows, 137 of first and 59 of second parity, and 97 Hampshire (H) sows, 55 of first and 42 of second parity, were used to determine the effect of increased dietary amino acids and two methionine-to-lysine ratios on sow lactation performance. The three treatment diets were: (1) a barley-wheat-soybean meal diet containing lysine at 0.43 g MJ-1 DE with no supplemental amino acids, 2) the same as diet 1, except the lysine content was increased to 0.68 g MJ-1 DE with supplemental threonine and methionine providing threonine and methionine to lysine ratios of 0.60 and 0.26, respectively, and 3) the same as diet 2, except with an increased methionine-to-lysine ratio of 0.30. All diets were fed as pellets, ad libitum in self-feeders, with free access to drinking water during a 28-d lactation period. Nursing piglets were given creep feed after 14 d of age. The average daily feed intake increased during lactation, and it was higher (P &lt; 0.05) in the second than the first parity sows. Feeding diets 2 and 3 increased (P &lt; 0.05) sow lactation weight and backfat gains, compared to diet 1 for both breeds. Feeding diet 3 increased (P &lt; 0.05) the sow lactation weight and backfat gains and piglet weight gains in the second parity Y sows, but not H sows. Post-weaning sow weight loss and weaning to estrus interval were not different (P &gt; 0.10) among the diets in both breeds. Feeding diets 2 and 3 decreased (P &lt; 0.05) the serum urea nitrogen concentration in Y sows indicating less amino acid catabolism. The results indicated that a dietary methionine-to-lysine ratio higher than 0.27 was not beneficial in maximizing lactation performance of modern lean genotype sows. Key words: Sows, lactation, ideal amino acid, Yorkshire, Hampshire, piglet

Heterosis and recombination effects on pig reproductive traits

The objective was to estimate breed, heterosis, and recombination effects on pig reproductive traits in two different four-breed composite populations. Breeds included Yorkshire, Landrace, Large White, and Chester White in Exp. 1 and Duroc, Hampshire, Pietrain, and Spot in Exp. 2. Data were recorded on purebred pigs, two-breed cross pigs, and pigs from generations F1 through F6, where F1 pigs were the first generation of a four-breed cross. Litter traits were considered a trait of the gilt. There were 868 first parity litters in Exp. 1 and 865 in Exp. 2. Direct heterosis significantly increased sow weight at 110 d of gestation and litter weight at 14 and 28 d (weaning) in both experiments. Direct heterosis significantly increased number of nipples, weight at puberty, lactation weight loss, litter size, and litter birth weight in Exp. 2. Gestation length in Exp. 1 and age at puberty in Exp. 1 and Exp. 2 were significantly decreased by direct heterosis. Maternal heterosis significantly increased age at puberty in Exp. 2 and decreased sow weight at 110 d of gestation in Exp. 1. Recombination significantly increased sow weight at 110 d of gestation and tended to increase total number born and litter birth weight in Exp. 1. Recombination significantly decreased age at puberty in Exp. 2. Litter heterosis significantly increased number of pigs at 14 and 28 d; litter weights at birth, 14, and 28 d; and tended to increase lactation weight loss in Exp. 1. Litter heterosis decreased litter size in Exp. 2. Maternal heterosis and recombination effects had a sampling correlation of -0.97 in Exp. 1 and -0.91 in Exp. 2 for number of fully formed pigs. Therefore, maternal heterosis and recombination effects were summed, and their net effect was tested. This net effect tended to increase number of nipples, lactation weight loss, and litter birth weight and significantly increased number of fully formed pigs in Exp. 1. Direct, maternal, and litter heterosis and recombination effects significantly influenced reproductive traits.

Lactational performance and body weight change in cows fed the fungal treated wheat straw

In Iran, the availability of high quality forages is restricted. The use of wheat straw, which is accessible in a huge amount, is limited due to its low nutritional value. Recently, biological method using white-rot fungi to improve the nutritional value of straw have been reported (Zadrazil 1997). However, the data available have been obtained from in vitro works. Additionally, little information is available on the utilization of fungal treated straw fed to dairy cow. Therefore, this experiment was carried out to assess the effect of fungal treated wheat straw on the performance of lactating cows.

The influence of gestation feeding strategy on body composition of gilts at farrowing and response to dietary protein in a modified lactation.

Previous experiments have indicated that reproductive function in lean, modern genotypes may be more dependent on body protein mass than, as previously believed, on body lipid reserves. This was investigated in a 3 x 2 factorial arrangement of treatments, involving 60 first-parity sows, comparing three pregnancy feeding strategies and two lactation diets. During pregnancy, sows were fed either a basal diet (5 g lysine/kg, 13 MJ of DE/kg [C]) or the same quantity of basal diet + energy source [E], or additional basal diet supplying both protein and energy [A]. The level of supplement for E and A was adjusted weekly to achieve a backfat thickness measurement (P2 position) of 28 mm at farrowing. Isoenergetic lactation diets were fed to appetite and provided either high (180 g CP/kg, 9 g lysine/kg [H]) or low lysine (120 g CP/kg, 6 g lysine/kg [L]). From d 21 of lactation, sows were separated from their litters and housed next to a boar for 8 h each day; final weaning occurred on d 31. Pregnancy treatment differences in backfat and weight were achieved, with C sows having less backfat on d 1 of lactation than E and A sows (E = 28.1, A = 28.0, C = 22.7 kg, P < 0.001). Sows fed additional basal diet were heavier than E sows, which were heavier than C sows (E = 190, A = 201, C = 178 kg, P < 0.001). Average feed intake over lactation showed a pregnancy feeding effect, with E sows eating less than A or C sows (E = 4.9, A = 5.2, C = 5.4 kg/d, P < 0.005). Total lactation weight loss was affected by pregnancy feeding (E = 18.0, A = 19.0, C = 8.4 kg, P < 0.05) and by lactation diet (L = 19.0, H = 11.3 kg, P < 0.05), whereas total lactation backfat loss was affected only by pregnancy treatment (E = 6.9, A = 6.5, C = 4.6 mm, P < 0.05). No pregnancy treatment or lactation diet effects were observed for litter performance. Lactation diet affected weaning-to-estrus interval, with more sows on the H diet coming into estrus within 6 d of partial weaning (P < 0.05), but there was no pregnancy treatment effect. Therefore, voluntary feed intake during lactation was suppressed by increased fat reserves at a limited body protein mass but not when body protein mass was also increased. Partial weaning-to-estrus interval was increased by reduced dietary protein.

Effect of work applied at different stages of lactation on milk production, reproduction and live-weight change of F1 crossbred dairy cows used for draught

AbstractThis study examined whether work applied at different stages of lactation had any effect on reproduction of cows under two feeding regimes. Twenty-four F1 crossbred dairy cows (12 Friesian × Boran and 12 Simmental × Boran) were allocated one of two diets (H + 3: natural pasture hay + 3 kg concentrate per day; and H + 5: natural pasture hay + 5 kg concentrate per day) and one of three work treatments — starting 45 days (D45), 90 days (D90) and 135 days (D135) post partum — using a principal component analysis score based on milk yield, live weight, calving interval and parity. Cows pulled sledges for 50 days (pull = 108 N per 100 kg live weight). Over the experimental period of 315 days, cows on diet H + 5 travelled a similar distance and produced amounts of fat-corrected milk (FCM) similar to those of cows on diet H + 3. Total intake of dry matter per kg live weight 0·75 was higher for cows on diet H + 5 than for cows on diet H + 3 and was similar across work times. Hay dry-matter intake was greater for the H + 3 group than for the H + 5 group at 180 days post partum and thereafter. Cows on diet H + 5 lost less weight in early lactation and gained more in mid and late lactation than cows on diet H + 3. During the work period, live-weight change was similar across diets but it was different between work treatments D45 and D135. The interval from calving to conception decreased by 63 and 101 days when start of work was delayed from D45 to D90 and from D45 to D 135, respectively. Output/input ratios of metabolizable energy equivalents were 0·35 for H + 3 and 0·37 for H + 5 diet, and 0·34, 0·37 and 0·40 for work times D45, D90 and D135, respectively. These results indicate that work started in early lactation significantly increased days to conception and decreased overall productivity of lactating working cows. Farmers must weigh the relative importance and cost of delayed ploughing against those of delayed oestrus or against the cost of borrowing draught power.

Influence of feeding increasing levels of leucaena leaf meal on the performance of milch goats and metabolism of mimosine and 3-hydroxy-4 (1H) pyridone

Four crossbred (Alpine × Beetal) milch goats (24 months; 30 kg live weight) in early lactation received during 31 days increasing levels of Leucaena leucocephala leaf meal (LLM): 25, 50, 75 and 100% of dietary DM during first, second, third and fourth week onwards, respectively. Remaining dietary DM was supplied through green berseem and a concentrate mixture which constituted the whole diet after the 31 days feeding on LLM. Mimosine and 3-hydroxy-4 (1H) pyridone (3,4 DHP) contents of the LLM were 1.88 and 0.78% respectively. Daily average mimosine, 3,4 DHP and total toxin intake was 196, 82 and 278; 339, 141 and 480; 553, 230 and 783; and 648, 269 and 971 g kg −1 live weight (W) during first, second, third and from fourth week onwards, respectively. DM intake on sole feeding of LLM was 65.9 g kg −1 W 0.75. No clinical toxicity symptoms were noted. Milk yield started declining from Day 27 onwards and reached the lowest level on Day 33 though LLM was discontinued from Day 31 onwards. Milk yield started improving from Day 37 and reached a peak by Day 49. The milk samples were free of mimosine and DHP, possibly due to some kind of barrier between blood and udder. Mimosine was not detectable in blood serum samples. The 3,4 DHP concentration in the blood serum, however, ranged from 97 on Day 8 to 402 μg ml −1 on Day 29 and disappeared completely by Day 36 when animals were on conventional diet. During metabolism trial faecal excretion of mimosine and 3,4 DHP was 4.43 and 17.9% of total toxin intake, respectively. Urinary excretion of mimosine was 1.59% while that of 3,4 DHP and 2,3 DHP through faeces and urine was 52.17% of total toxin consumed. DCP and TDN values of LLM in goats were 16.03 and 61.58%, respectively. Goats were in positive N balance. The T 3 and T 4 levels declined but DM intake was not affected. The SGOT and SGPT values were in the normal range. The study indicated that LLM could form a substantial portion of milch goat ration and milk of such goats being free of mimosine and DHP should be fit for human consumption.

Differences in health characteristics between native Japanese and Japanese-Americans.

Health characteristics were compared among 1193 Japanese in Hiroshima, and 2306 Japanese-Americans in Hawaii. Japanese women experienced later menarche, earlier menopause, and a shorter interval between menarche and menopause than Japanese-Americans. Japanese men and women were shorter and lighter and the men bad lower body mass index than Japanese-Americans. Differences between populations were also found for the prevalence of artificial menopause, number of live births, lactation period, smoking, and alcohol consumption. Within one or both populations, significant trends with birth year were found for age at menarche, age at menopause, interval between menarche and menopause, lactation period, height, weight, and body mass index, suggesting the existence of cohort effects. Some of these trends may also reflect age-related changes. Environmental factors likely contribute to the differences in physique and reproductive factors, which may explain differences in frequency of osteoporosis, cardiovascular diseases, and cancer between the two populations.

Lactation Yields and Accuracies Computed from Test Day Yields and (Co)Variances by Best Prediction

Lactation records are calculated from data on milk, fat, and protein obtained from one or more milkings on several days during the lactation. The test interval method, which estimated missing daily milk yields by simple interpolation, was used for many years for standard monthly data but may not be as useful for the wider variety of test plans now being proposed. More accurate 305-d yields can be computed using best prediction, which has optimum properties if means and (co)variances are known and distribution is multivariate normal. The covariance of test day and 305-d yields is multiplied by the inverse of the test day (co)variance matrix, which is then multiplied by the test day deviation vector. This predicted 305-d deviation plus the mean 305-d yield equals the predicted 305-d yield. Similar algebraic methods are used to compute the correlation of true and estimated 305-d yields, which is needed to calculate lactation weights. Computation times were affordable but not trivial; they ranged from 0.001 to 1s per lactation. Equations were modified to account for differing accuracies of data for partial days, means for multiple days, and data for unsupervised tests. Complete or incomplete lactations recorded with very different testing plans can be graphed and compared by best prediction.

The Effect of Dietary Energy Source During Mid to Late Lactation on Liver Triglyceride and Lactation Performance of Dairy Cows

Control [1.61 Mcal of net energy for lactation (NEL)/kg of dry matter (DM)], high grain (1.70 Mcal of NEL/kg of DM), or high fat [1.70 Mcal of NEL/ kg of DM with 2.3% tallow (DM basis)] diets were fed to 43 cows (150±3.1 d in milk) during mid to late lactation to determine effects on performance characteristics, metabolic parameters, or both during mid to late lactation, the dry period, and the first 100 d of the next lactation. All cows received identical diets during the dry period and during early lactation. Increasing the energy density of the diets during mid to late lactation increased DM intake (DMI), plasma nonesterified fatty acid concentration, milk production, and milk protein yield. Compared with the high grain diets, fat supplementation decreased DMI and the percentage of milk protein but increased plasma nonesterified fatty acid concentration without causing elevation of liver triglyceride at the end of mid to late lactation. Increased energy density of the diets did not affect body condition score during mid to late lactation. There were no residual effects for any of the treatments on DMI, lactation performance, or body weight in the subsequent lactation. However, energy supplementation during mid to late lactation increased liver triglyceride content after calving. Compared with high fat diets, high grain diets fed during mid to late lactation increased plasma β-hydroxybutyrate concentration in the subsequent lactation. High energy diets fed during mid to late lactation may influence lipid metabolism during the following lactation.

Predicting empty body composition and composition of empty body weight changes in mature cattle

Data on empty body chemical composition of 18 breeds or breed crosses of non-lactating, non-pregnant mature cows, were used to estimate a standard reference empty body weight (SREBW) for each breed. The SREBW was defined as the empty body weight at skeletal maturity that contained 25% fat. Relationship between empty body fat percentage (EBFP) and empty body weight as a fraction of SREBW ( μ E ) was, EBFP = −15·7 + 40·7 ∗μ E( r 2 = 0·77) . This relationship was not significantly different among breeds. An evaluation with chemical composition data of five breeds of mature non-lactating cows showed no significant difference in the relationship between EBFP and μ E . Data from five experiments showed that cows that lose empty body weight in early lactation had a leaner empty body composition in mid-lactation compared with non-lactating cows at the same value of μ E . Equations were formulated to adjust predictions of body composition changes for lactating cows.

Effect of feeding various dietary vitamin B6 concentrations during gestation and lactation on vitamin B6 level in liver and carcass of rat dams.

The present investigation was designed to determine the vitamin B6 concentration in liver and carcass of rat dams fed various dietary vitamin B6 levels during gestation and lactation. Therefore, gravid female rats received 0.6, 3, 6, 18 or 180 mg vitamin B6 per kg diet. After parturition each group was divided into 2 groups of 8 dams each, which received then a diet with 3, respectively 6 mg/kg vitamin B6 during lactation. At the end of the experiment at day 14 of lactation weight gain and food consumption as well as liver and carcass weights did not differ within the groups. The present data clearly show that both in liver and carcass of lactating rats, there exists only a slight dose-response-relationship between the dietary vitamin B6 intake and the vitamin B6 concentration in body tissue. Moreover, liver reflects the various vitamin B6 supplies during gestation and lactation somewhat better than carcass. The distribution of the vitamins did not differ among the groups and was therefore independent of the vitamin B6 supply. The present findings, especially regarding the liver, elucidate, that an adequate vitamin B6 supply during lactation can not compensate for a lack of vitamin B6 during gestation and vice versa a high dose of vitamin B6 during gestation did not completely protect against a suboptimal vitamin B6 during lactation.

Lifetime productivity in gilts previously selected for decreased age at puberty

AbstractA study was conducted to evaluate the effect of decreasing age of puberty on lifetime productivity in sows. Two lines of gilts from the Nebraska Gene Pool population were used in this study: a line that had been selected for decreased age at puberty (AP) and a line in which selection had been random (RS). The study was conducted in two parts. In part one, 75 gilts were mated at second oestrus and the productivity measured over five parities. A second experiment utilizing 68 gilts was conducted to provide further data for comparing litter size at parity 1, and also to compare ovulation rates in the two lines at second oestrus. Results showed that litter size was similar in both lines across parities. After five parities the percentage of sows farrowing relative to parity 1 was 58-8% for the AP line but only 39·4% for the RS line (P = 0·17). Litter birth weight, litter size and weight at 21 days, number weaned, and lactation food consumption were similar for both lines. Lactation weight loss was not significantly different between the two lines (60·9 (s.e. 5·9) v. 527 (s.e. 5·0) kg, for RS and AP gilts, respectively) but was consistent with the slightly longer weaning to remating intervals in the RS line (7·8 (s.e. 0·7) v. 6·6 (s.e. 0·7) days, P = 0·22). Ovulation rate at second oestrus did not differ between the two lines (14·1 (s.e. 0·9) v. 14·3 (s.e. 0·5), for RS and AP gilts, respectively). The regression of mean accumulative productivity on time was in favour of the AP line (P = 0·05). These results suggest that reproductive performance is not impaired in gilts which have been selected to reach puberty at earlier ages, and productivity at a specific age may be enhanced.