Mammary growth patterns in guinea pigs during puberty, pregnancy and lactation

Mammary gland growth patterns were studied in 110 guinea pigs during the growth phase, pregnancy and lactation. Body weight changes were studied and, in addition, mammary indices were wet weight, dry fat-free tissue (DFFT), deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Statistical analyses were mathematical regression models to best fit the actual data. These included linear, quadratic, cubic, and several forms of exponential regression models. Data were separated into growth phase (60 guinea pigs in 10 age groups), pregnancy (20 guinea pigs in 4 groups), and lactation (30 guinea pigs in 6 groups). Data during pregnancy and the first 5 days of lactation were pooled and analyzed also because mammary growth continued beyond pregnancy to Day 5 of lactation. Mammary wet weight increased according to a cubic expression in the growth phase, while mammary DFFT, DNA and RNA were rectilinear through 200 days of age. During pregnancy and the first 5 days of lactation, mammary growth parameters followed the pattern of an exponential equation. Daily rates of increase for mammary DFFT and DNA were twice the rate for mammary wet weight. During lactation, mammary gland indices increased to Day 5 and then decreased gradually from Day 10 to Day 20. The best mathematical models for these change were those which are used to describe lactation curves, but all mammary gland indices decreased later and more gradually than milk production. Comparisons in growth rates of guinea pig mammary glands were made with those published for dairy goats and dairy cows. Rates of mammary DNA changed inversely to lengths of gestation in these 3 species.     

Short- and long-term effects of high milking frequency during the first 21 days of lactation on production and reproductive performance in high-lactating cows

We examined short- and long-term effects of high milking frequency (HMF) for the first 21 days of lactation. The study included 122 Israeli Holstein cows – 32 pregnant heifers, 40 cows in second lactation and 50 cows in >second lactation. Heifers were paired according to predicted transmitting ability and cows according to energy-corrected milk (ECM) production, age, days in milk and expected calving date. Thin cows (body condition score <2.75) were not included. One cow from each pair was arbitrarily allocated to a control group milked three times daily (3× milking cows) and the counterpart to an experimental group milked six times daily for the first 21 days of lactation and then three times daily for the rest of the lactation (6× milking cows). During the first 21 days of lactation, 6× milking cows produced 9.3 kg more milk (26.5%) and 7.16 kg more ECM (19%) than the 3× milking cows. The higher milk production persisted throughout the entire lactation (305 days), as reflected by treatment×age interaction showing higher milk production for the first and second (7%) but not >second lactation cows relative to their control counterparts (−0.37%); ECM production was also higher in 6× milking first and second lactation (7.6% and 5%, respectively) but not for >second lactation cows. Furthermore, HMF had long-lasting effects, expressed as significantly higher milk production through the succeeding lactation in the previous first lactation cows (10%); a tendency toward significance in the second lactation cows relative to the controls (4.7%), but a deleterious effect on the >second lactation cows, reflected by lower milk production (−5.25%) than in controls; similar patterns were found for the ECM. For the entire 305 days of lactation, fat and protein yields were higher for first and second lactation cows, whereas protein yield for >second lactation cows was lower in the 6× milking v. control group. Given that HMF during the first 21 days of first or second lactation increases milk and ECM yields throughout the concurrent and successive lactation with no adverse effect on energy balance, mastitis, metabolic diseases or reproduction, it seems to be economically beneficial. However, caution should be paid for >second lactation cows due to absence of significant effect in the entire of the first HMF applied lactation and the deleterious effect in the succeeding lactation.     

Insulin-like growth factor I (somatomedin C) in goats during normal lactation and in response to somatotropin treatment

1. Two experiments were performed. In Experiment 1, IGF-I concentrations in serum were followed in four lactating dairy goats during normal lactation and before, during and after 14 days of daily administration of 10 IU recombinant bovine somatotropin, starting 10 weeks post-partum. In Experiment 2, IGF-I was measured in single blood samples obtained from 40 dairy goats in the first part of lactation. 2. Measured IGF-I concentrations ranged from 4.4-9.0 nM. Concentrations varied during the day with coefficients of variation from 8.9 to 18.4% in the four goats in Experiment 1. There were no systematic trends in the diurnal variations (P greater than 0.75). 3. Concentrations of IGF-I remained fairly constant in all goats in Experiment 1 during the lactational period, and were not related to the changes in milk yield (P greater than 0.65). Similarly, no relationship was found in Experiment 2 between level of milk production and IGF-I concentration in serum. 4. Somatotropin treatment stimulated milk yields by 14 +/- 2.9% (P less than 0.05) and IGF-I concentration by 27.9 +/- 6.7% (P less than 0.05). 5. IGF-I is the most likely factor which increases mammary gland synthetic capacity in response to somatotropin treatment, and thus is responsible for the galactopoietic effect of this hormone being exerted. 6. However, serum IGF-I may primarily be involved in regulation of nutrient partitioning during normal lactation, but a paracrine synthesis with local effect on the mammary gland cannot be ruled out.     

The activities and intracellular distributions of enzymes of carbohydrate, lipid and ketone-body metabolism in lactating mammary glands from ruminants and non-ruminants.

1. The activities of several enzymes of carbohydrate, lipid, acetate and ketone-body metabolism were measured in lactating mammary glands from rats, mice, rabbits, guinea pigs, sows, sheep, cows and goats. The intracellular distributions of many of the enzymes were measured by fractional extraction. 2. Acetyl-CoA synthetase was predominantly cytoplasmic in rats and guinea pigs, but was more mitochondrial in the other species. The different location of this enzyme in rats and mice is discussed in relation to the disposal of reducing equivalents. 3. 3-Oxo acid CoA-transferase and acetoacetyl-CoA thiolase assayed at 600 microM-CoA were predominantly mitochondrial in all species investigated. Acetoacetyl-CoA thiolase assayed at 8 microM-CoA was predominantly cytoplasmic, except in rabbits and guinea pigs. Ruminants appeared to possess little, if any, of the cytoplasmic enzyme. 4. The activities and distributions of NADP-isocitrate dehydrogenase were consistent with a role in supplying cytoplasmic NADPH in ruminant tissue, and indicated that this system may also occur in guinea pigs.     

Grazing behaviour and performance of lactating suckler cows, ewes and goats on partially improved heathlands

The foraging behaviour (grazing time and diet composition), live-weight (LW) changes and parasitic infection (faecal egg counts of gastrointestinal nematodes) of 12 beef cows, 84 ewes and 84 goats suckling their offspring, managed in mixed grazing on heathlands with 24% of improved pasture of perennial ryegrass-white clover, were studied during the years 2003 and 2006. The results showed that goats tended to graze for a longer time, and utilised significantly more heathland vegetation than cattle and sheep, including in their diet in an average of 0.39 herbaceous plants, 0.11 gorse and 0.51 heather over the grazing season, comparing with respective mean values of 0.85, 0.02 and 0.13 in cattle and sheep. Dietary overlap was higher between cattle and sheep (0.76) than between sheep and goats (0.53) or between cattle and goats (0.47). Despite the high performance of autumn-calving cows in spring, sheep had the best LW changes per livestock unit (LU) during the whole grazing season. Goats' performance per LU was lower than in sheep but higher than in spring-calving cows. Regarding offspring production, lambs had higher LW gains per LU than calves and kids. Mean nematode eggs/g fresh faeces (epg) during the grazing season were higher in goats (91 epg) compared with sheep (34 epg) and cattle (14 epg), particularly from September to December. In conclusion, sheep performed best on these heathlands with improved pasture areas if the entire grazing season was considered, despite the good level of production in spring from autumn-calving cows. The results suggested the complementary use of goats in order to increase the effective utilisation of the available vegetation, achieving production levels similar to those from spring-calving cows. Therefore, mixed flocks of sheep and goats would be the most appropriate sustainable systems from the animal production and vegetation use points of view.     

Performance of dairy cows milked twice daily at contrasting intervals

The time constraints of the classic twice-daily milking routine are less easily endured by individual dairy farmers, because of their impact on quality of life. Our aim was to evaluate milk production responses by dairy cows milked twice daily at contrasting intervals. In experiments 1 (20 cows) and 2 (28 cows), four milking regimes were compared during a 3-week period beginning after the peak of lactation. Three groups of five cows were milked twice daily (TDM) with milking intervals of 11 : 13, 7 : 17 and 3 : 21 h in experiment 1, and three groups of seven cows at 11 : 13, 5 : 19 and 2.5 : 21.5 h in experiment 2. One group (five and seven cows respectively) was milked once daily (ODM) in each experiment. In experiment 3 (three groups, 12 cows per group), one group was milked at 10 : 14 h and one at 5 : 19 h, and the third group once daily. Milking treatments began during the second week of lactation and continued for an average of 23 weeks. In experiments 1 and 2, daily milk yields were reduced by 4.1%, 11.5% and 28%, for the 5 : 19, 3 : 21 and ODM milking treatments compared with the 11 : 13 h interval. In experiment 3, the decrease in daily milk yields for 5 : 19 h and ODM was 10% and 40% compared with the 10 : 14 h time interval. In the average daily milk, fat and protein contents and somatic cell counts were not different between the TDM groups, and the ODM group had (or tended to have) a higher fat and protein content. For a given milking, milk fat content decreased from about 60 to 32 g/kg as the preceding milking interval increased from 2.5 to 3 h up to 12 h. It then levelled out and even increased, mainly after 18 to 20 h. Somatic cell count showed a similar trend, and protein content did not change steadily. Dry matter intake, body weight and body condition score were not affected by contrasting milking intervals. After resumption of TDM with conventional intervals, productions of milk, fat and protein no longer differed between the TDM groups. Milk yield of previously ODM cows remained lower by 2 kg/day (P = 0.15) in experiments 1 and 2, and by 7 kg/day (P < 0.05) in experiment 3. These results suggest that TDM at contrasting intervals up to 5 : 19 h is feasible as it decreases milk yield only moderately, especially if implemented from peak of lactation.     

Effects of stage of pregnancy on variance components,daily milk yields and 305-day milk yield in Holstein cows,as estimated by using a test-day model

Pregnancy and calving are elements indispensable for dairy production, but the daily milk yield of cows decline as pregnancy progresses, especially during the late stages. Therefore, the effect of stage of pregnancy on daily milk yield must be clarified to accurately estimate the breeding values and lifetime productivity of cows. To improve the genetic evaluation model for daily milk yield and determine the effect of the timing of pregnancy on productivity, we used a test-day model to assess the effects of stage of pregnancy on variance component estimates, daily milk yields and 305-day milk yield during the first three lactations of Holstein cows. Data were 10 646 333 test-day records for the first lactation; 8 222 661 records for the second; and 5 513 039 records for the third. The data were analyzed within each lactation by using three single-trait random regression animal models: one model that did not account for the stage of pregnancy effect and two models that did. The effect of stage of pregnancy on test-day milk yield was included in the model by applying a regression on days pregnant or fitting a separate lactation curve for each days open (days from calving to pregnancy) class (eight levels). Stage of pregnancy did not affect the heritability estimates of daily milk yield, although the additive genetic and permanent environmental variances in late lactation were decreased by accounting for the stage of pregnancy effect. The effects of days pregnant on daily milk yield during late lactation were larger in the second and third lactations than in the first lactation. The rates of reduction of the 305-day milk yield of cows that conceived fewer than 90 days after the second or third calving were significantly (P<0.05) greater than that after the first calving. Therefore, we conclude that differences between the negative effects of early pregnancy in the first, compared with later, lactations should be included when determining the optimal number of days open to maximize lifetime productivity in dairy cows.     

Effects of rumen-protected choline supplementation on milk production and choline supply of periparturient dairy cows

The objective of the present study was to determine the effects of rumen-protected choline (RPC) supplementation on body condition, milk production and milk choline content during the periparturient period. Thirty-two Holstein cows were allocated into two groups (RPC group - with RPC supplementation, and control group - without RPC supplementation) 28 days before the expected calving. Cows were fed the experimental diet from 21 days before expected calving until 60 days of lactation. The daily diet of the RPC group contained 100 g of RPC from 21 days before calving until calving and 200 g RPC after calving for 60 days of lactation, which provided 25 g and 50 g per day choline, respectively. Body condition was scored on days -21, 7, 35 and 60 relative to calving. Milk production was measured at every milking; milk fat, protein and choline content were determined on days 7, 35 and 60 of lactation. Body condition was not affected by RPC supplementation. Milk yield was 4.4 kg higher for the group of cows receiving supplementary choline during the 60 days experimental period and 4% fat-corrected milk production was also increased by 2.5 kg/day. Milk fat content was not altered by treatment, but fat yield was increased by 0.10 kg/day as a consequence of higher milk yield in the RPC-treated group. Milk protein content tended to increase by RPC supplementation and a 0.18 kg/day significant improvement of protein yield was detected. Milk choline content increased in both groups after calving as the lactating period advanced. However, milk choline content and choline yield were significantly higher in the RPC group than in the control group. The improved milk choline and choline yield provide evidence that some of the applied RPC escaped ruminal degradation, was absorbed from the small intestine and improved the choline supply of the cows and contributed to the changes of production variables.     

A comparison of energy balance and metabolic profiles of the New Zealand and North American strains of Holstein Friesian dairy cow

The milk production, energy balance (EB), endocrine and metabolite profiles of 10 New Zealand Holstein Friesian (NZ) cows and 10 North American Holstein Friesian (NA) cows were compared. The NA cows had greater peak milk yields and total lactation milk yields (7387 v. 6208 kg; s.e.d. = 359), lower milk fat and similar protein concentrations compared with the NZ cows. Body weight (BW) was greater for NA cows compared with NZ cows throughout lactation (596 v. 544 kg; s.e.d. = 15.5), while body condition score (BCS) tended to be lower. The NA strain tended to have greater dry matter intake (DMI) (17.2 v. 15.7 kg/day; s.e.d. = 0.78) for week 1 to 20 of lactation, though DMI as a proportion of metabolic BW was similar for both strains. No differences were observed between the strains in the timing and magnitude of the EB nadir, interval to neutral EB, or mean daily EB for week 1 to 20 of lactation. Plasma concentrations of glucose and insulin were greater for NA cows during the transition period (day 14 pre partum to day 28 post partum). Plasma IGF-I concentrations were similar for the strains at this time, but NZ cows had greater plasma IGF-I concentration from day 29 to day 100 of lactation, despite similar calculated EB. In conclusion, the results of this study do not support the premise that the NZ strain has a more favourable metabolic status during the transition period. The results, however, indicate that NZ cows begin to partition nutrients towards body reserves during mid-lactation, whereas NA cows continue to partition nutrients to milk production.     

High- and low-purity glycerine supplementation to dairy cows in early lactation: effects on silage intake,milk production and metabolism

This study evaluated the effects of supplemental low- and high-purity glycerine on silage intake, milk yield and composition, plasma metabolites and body condition score (BCS) in dairy cows. A total of 42 cows of the Swedish Red Breed, housed in individual tie stalls, were fed 0.25 kg of low- or high-purity glycerine on top of concentrate, twice daily, during the first 4 weeks of lactation. One-third of the cows acted as controls, receiving no glycerine. Silage was fed for ad libitum intake and concentrate was fed at restricted level of intake, about 6 kg/day for primiparous cows and 7 kg/day for multiparous cows. Feed refusals were weighed daily. Cows were milked twice daily, milk yield was recorded on four occasions per week and milk samples were collected simultaneously. Blood samples were drawn from the coccygeal vessel once a week. Low- and high-purity glycerine had no effect on silage or total dry matter intake (P = 0.38 and P = 0.75, respectively) or on BCS (P = 0.45). Cows fed high-purity glycerine tended to have higher milk yield than control cows (P = 0.06). Milk composition tended to differ among treatments. No main effects of treatment on concentration of glycerine (P = 0.44), glucose (P = 0.78), insulin (P = 0.33), non-esterified fatty acids (P = 0.33) and β-hydroxybutyrate (P = 0.15) in plasma. These data indicate that high-purity glycerine has the potential to increase milk yield, as well as enhance the milk protein concentration and milk fat + protein yield.     

Rates of passage of digesta and water absorption along the larg intestines of sheep, cows and pigs.

In 5 cows, the mean length of the large intestine was only slightly greater than that of 21 sheep and 3 pigs. At about one-fifth of the way along the large intestine of the sheep and cows, corresponding to the end of the proximal colon and start of the spiral colon, there were marked reductions in the amount of digesta present and in the lumen diameter. In pigs these parameters decreased gradually along the large intestine. In all parts of the large intestine, the cows had more water in the digesta than did the sheep or the pigs. Nevertheless, the decrease in water content between the caecum and the rectum was similar for the cows and the sheep but less in the pigs. The rate of passage of digesta increased gradually along the large intestine of the pigs, but in the cows and sheep the rate was least in the caecum and proximal colon and greatest in the spiral colon. The total retention time for digesta in the large intestine was approximately 30, 20, and 9 h in the pigs, sheep, and cows respectively. The rate of water absorption from the large intestine was most rapid in the cows and slowest in the pigs. Differences in faecal water content between the species were not due to differences in retention times in the large intestine.     

Short communication: Variance and autocorrelation of deviations in daily milk yield are related with clinical mastitis in dairy cows

Daily milk production, and fluctuations therein, can provide information on health and resilience of dairy cows. We studied variance and autocorrelation of deviations in daily milk yield in relation to the occurrence of clinical mastitis (no, early or later in lactation). Individual lactation curves were fitted to 305-d lactations of 414 dairy cows using quantile regression. Log-transformed variance (lnVar) and autocorrelation of the quantile residuals of daily milk yield (predicted – observed) were evaluated for intervals until 30 and until 305 days in milk (DIM). Cows were classified as having no mastitis (n = 249), early mastitis that first occurred before 30 DIM (n = 29); or later mastitis (n = 136). Subsequently, linear models were used to assess effects of mastitis and parity class (primiparous or multiparous) on lnVar and autocorrelations; and logistic regression analyses were performed to predict mastitis from lnVar or autocorrelation and parity. From 10 to 30 DIM, lnVar was greater for cows with early mastitis than for cows with no or late mastitis, and autocorrelation tended to be lower for cows with early mastitis than for cows with no mastitis. The lnVar and autocorrelation from 10 to 30 DIM were not predictive of late mastitis. From 10 to 305 DIM, lnVar was greater and autocorrelation was lower for both cows with early and late mastitis than for cows with no mastitis; and both were predictive of having mastitis in the 305-d lactation. Primiparous cows had lower lnVar than multiparous cows. In cows without mastitis, autocorrelation values were positively correlated with lnVar. Results confirm that increased lnVar is associated with clinical mastitis.     

Variations During Lactation in Total and Differential Leukocyte Counts,N-acetyl-ß-D-glucosaminidase,Antitrypsin and Serum Albumin in Foremilk and Residual Milk from Non-infected Quarters in the Bovine

Quarter samples of foremilk and residual milk were taken approximately every second week from 2 days post partum (pp) throughout lactation month 9, from 5 dairy cows in their second lactation period. Bacteriologically positive milk samples were excluded. The aim was to study the variation in total and differential leukocyte counts, N-acetyl-ß-D-glucosaminidase (NAGase), antitrypsin (ATR) and serum albumin (BSA) in milk during the lactation period and different stages of oestrous cycle. Also the between milkings variation was studied from lactation month 4 to 9. At 2 days pp, each fraction of milk contained significantly higher numbers of leukocytes and had a higher activity of NAGase and ATR than later in the lactation period. In foremilk the highest content of BSA was also recorded at 2 days pp. From lactation month 2 to 9, stage of lactation had, in general, a slight effect on the variation in the variables measured. The total leukocyte count in residual milk tended to increase as lactation proceeded. The proportion of monocyte-macrophages in foremilk was significantly decreased during the last 4 months. NAGase and BSA in both fractions and ATR in residual milk increased significantly towards the end of the lactation period. From lactation month 4 to 9 the highest recorded ranges of variation between milkings, within quarter and stage of lactation, in the total leukocyte count, proportions of neutrophils, lymphocytes, monocyte-macrophages, NAGase, ATR and BSA in foremilk were 215 × 103ml, 42 %, 34 %, 54 %, 6.68 units, 0.36 units and 0.14 mg/ml respectively. The corresponding figures in residual milk were higher except for the variation in BSA which was slightly lower in residual milk than in foremilk. In residual milk there was a positive correlation between the proportion of neutrophils and the total leukocyte count, when calculated on data from all cows and the entire experimental period. During the oestrous periods, the proportion of neutrophils in residual milk was higher than during the dioestrous periods. Foremilk and residual milk differed in the total as well as the differential leukocyte counts in all the various stages of lactation, whereas the contents of NAGase, ATR and BSA were equal in both fractions. The exception was 2 days pp when the proportions of lymphocytes were equal in both fractions and BSA-significantly higher in foremilk than in residual milk.     

Specific antibodies to hemoglobin A1 (anti-Glu) and hemoglobin S (anti-Val) in the guinea pig: immunologic and structural correlations.

Like goats and sheep, guinea pigs can produce, in response to human sickle cell hemoglobin (beta6 Glu leads to Val), an antibody population (anti-Val) that will bind sickle cell hemoglobin but not normal hemoglobin HbA. Unlike goats and sheep, guinea pigs can produce in response to human hemoglobin A1 an antibody fraction, anti-Glu, that will not react with human sickle cell hemoglobin. These anti-Glu antibodies have been isolated by affinity chromatography and their specificity confirmed by fluorescence-quenching titrations. The sequence of the first 10 amino acids of the beta-chain of guinea pig hemoglobin has been determined. This sequence differs from those of both hemoglobin HbA and sickle cell hemoglobin by two residues, those at positions 5 and 6. This explains the similarity of the immunogenicity of this site on the two human hemoglobins when administered to guinea pigs. Both goats and sheep are identical to hemoglobin A1 at the beta-6 position.     

Total and free thyroxine and triiodothyronine in blood serum of mammals

1. Blood samples were obtained from seven species of mammals: horses, cattle, sheep, goats, pigs, guinea pigs and rats for determination of total and free thyroxine and triiodothyronine. Total thyroxine in the order listed above in ng/ml was: 15, 60, 79, 185, 53, 45 and 79. Free thyroxine in pg/ml was: 5.9, 10.0, 19.2, 32.1, 21.7, 6.7 and 51.3. 2. Total triiodothyronine in pg/ml was: 677, 1290, 979, 3170, 760, 317 and 1747. Free triiodothyronine in pg/ml was: 3.22, 4.40, 2.60, 6.74, 2.74, 2.42 and 10.88. 3. Percent free thyroxine was high in rats and low in guinea pigs, while percent free triiodothyronine was high in guinea pigs and low in goats. 4. Free thyroxine and percent free thyroxine were higher in some groups of horses, particularly stallions, than in other groups.     

Effects of feeding propylene glycol on dry matter intake, lactation performance, energy balance and blood metabolites in early lactation dairy cows

The objectives of this study were to evaluate effects of feeding propylene glycol (PG) on feed intake, milk yield and milk composition, blood metabolites and energy balance in Holstein dairy cows from 1 to 63 days in milk. Thirty-two multiparous cows, blocked by lactation number, previous 305-day milk production and expected calving date, were arranged into four groups in a randomized block design. Treatments were: control, low PG, medium PG and high PG with 0, 150, 300 and 450 ml PG per cow per day, respectively. The supplement of food grade PG (0.998 g/g PG) was hand-mixed into the top one-third of the daily ration. Cows were fed ad libitum a total mixed ration consisting of forage and concentrate (50 : 50, dry matter basis). Feed intake, milk yield and milk components were not affected (P > 0.05) by PG supplementation. Overall, body weight (BW) loss tended (P < 0.08) to be linearly reduced, and energy status was linearly improved with increasing PG supplementation. Concentrations of glucose in plasma were higher for cows fed PG relative to control (55.6 v. 58.9 mg/dl) and linearly increased (P < 0.01) with increasing PG supplementation. Plasma concentrations of non-esterified fatty acids and beta-hydroxybutyrate were linearly increased, but urine acetoacetate concentration was quadratically changed with the highest for control diet and the lowest for 450 ml/day of PG. These results indicated that supplementation of PG in the early lactating cow diets had minimal effects on feed intake and milk production, but may potentially reduce contents of milk fat and milk protein. Supplementation of early lactating dairy cow diets with PG is beneficial in terms of improving energy status and reducing BW loss.     

Effects of feeding dry propylene glycol to early postpartum Holstein dairy cows on production and blood parameters

In all, 18 multiparous and 19 primiparous Holstein dairy cows were used in a completely randomized design with restrictions to evaluate the effects of feeding propylene glycol (PG) as a dry product, via two delivery methods, on production and blood parameters. PG treatments were administered from parturition through 21 days postpartum. Treatments were: (i) control, no PG; (ii) top dress, 162.5 g PG/day by top dressing onto the total mixed ration (TMR) and; (iii) mixing, 162.5 g PG/day as a part of the TMR by incorporating it into the TMR. PG used was a dry product which contained 65% pure PG and 35% silicon dioxide as the dry carrier. Coccygeal blood was sampled on 4, 7, 14 and 21 days in milk (±1.50 pooled s.d.). Supplementation of dry PG by top dressing onto, or incorporating into, the TMR had no effects on average dry matter intake, milk yield and composition, serum insulin, serum and plasma metabolites and milk ketones. Concentrations of urine ketones tended (P = 0.10) to be reduced by PG supplementation from 41.5 to 15.2 mg/dl. Supplementation of PG tended (P = 0.07) to decrease the incidence for subclinical ketosis from 39% to 24% and 13% for cows fed a TMR supplemented with no dry PG, with dry PG as a top dress and dry PG as a part of the TMR, respectively. It is concluded that supplementing PG as a dry product via incorporating into the TMR is as effective as when used as a top dress, based on the efficacies of both delivery methods to numerically reduce urine ketones concentrations and, therefore, the incidence for subclinical ketosis during the first 21 days of lactation. However, it should be noted that the number of cows used in the current study was minimal, and more cows are needed to confirm the efficacy of supplementing PG as a dry product on reducing the prevalence of subclinical ketosis in dairy cows during the first month of lactation.     

The significance of water absorption and fibre digestion in the omasum of sheep, goats and cattle

1. The omasal dry matter contents constituted 0.6, 1.2 and 3.3% of the body weight in the sheep, goats and cows, respectively. 2. A large part of the fluid leaving the reticulo-rumen passed quickly through or along the omasum to the abomasum in sheep (43%). The proportion was much less in goats (17%). 3. The absorption of water from the fluid delayed in the omasum was low: 15, 18 and 19% in sheep, goats and cows, respectively. 4. Little or no acid detergent fibre was degraded in the omasum.     

Local intra-arterial infusion of growth hormone into the mammary glands of sheep and goats: effects on milk yield and composition, plasma hormones and metabolites

Lactating goats and sheep were fitted with catheters in the external pudendal arteries supplying both mammary glands. Saline was infused continuously into one artery whereas the other artery received continuous infusions, over successive 4-day periods, of either saline or growth hormone (GH)-doses increasing twofold between successive periods from 100 to 400 micrograms/day in goats and 400 to 3200 micrograms/day in sheep. Local infusion of GH at up to 1600 micrograms/day in sheep did not affect milk yield or composition nor peripheral plasma concentrations of GH, insulin, glucose, urea and non-esterified fatty acids (NEFA). Infusion of GH at 3200 micrograms/day in sheep increased peripheral plasma concentrations of GH, tended to increase milk yield and peripheral plasma NEFA but there were no changes in peripheral plasma insulin, glucose and urea. It is concluded that GH does not exert direct effects on the mammary glands of sheep and goats in situations where the hormone is administered over short periods.     

Seroprevalence of Toxoplasma gondii in pigs, sheep, goats, and cattle from Grenada and Carriacou, West Indies

Prevalence of Toxoplasma gondii infection in pregnant women in Grenada is considered high. Little is known of the epidemiology of T. gondii infection in Caribbean Islands. Serum samples of 750 food animals in Grenada and Carriacou were tested for antibodies to T. gondii by the modified agglutination test (MAT). Antibodies to T. gondii (MAT, 1∶25 or higher) were found in 23.1% of 247 pigs, 44.1% of 204 sheep, 42.8% of 180 goats, and 8.4% of 119 cattle. Seroprevalence increased with age, indicating postnatal acquisition of T. gondii. Antibody titers of 1∶200 or higher were present in 65 of 90 seropositive sheep, 61 of 77 seropositive goats, and 23 of 57 seropositive pigs. However, none of the cattle had a MAT titer of 1∶200, suggesting that bovines are a poor host for T. gondii. Results indicate that pigs, sheep, and goats could be important sources of T. gondii infection if their meat is consumed undercooked.