C. Peris

Quantitative estimation of the impact of caprine arthritis encephalitis virus infection on milk production by dairy goats

This retrospective study investigated milk production losses associated with serological evidence (serostatus) of caprine arthritis encephalitis virus (CAEV) infection over one lactation in 4543 Murciano-Granadina goats from 22 herds in Spain. The seroprevalence of infection was 18%, ranging from 0% to 2% in 11 herds, 7% to 60% in 10 herds and was 100% in one herd. Seropositive does had significantly shorter lactations, produced less milk and milk fat, lactose and dry extract and had higher somatic cell counts than their seronegative counterparts, although differences in milk production between seropositive and seronegative animals were noted between herds. Mixed regression models confirmed the association between CAEV seropositivity and reduced milk production. The adjusted, least squares mean (LSM) test-day milk yield was 10% less in seropositive compared to seronegative does and this difference varied according to lactation number. In contrast, differences in the LSM of milk fat, lactose and dry extract percentages between seropositive and seronegative goats were only between 0.1% and 0.2% and did not increase with lactation number. The findings of this study provide strong evidence that CAEV-infection can be a major cause of reduction in milk yield in goats and its control should be considered as part of dairy goat herd health schemes.

Quantification of milk yield and composition changes as affected by subclinical mastitis during the current lactation in sheep

The aim of this work was to quantify, on a half-udder basis, the changes in ewe milk yield and composition caused by unilateral subclinical mastitis within the current lactation. Fluctuations due to production level, infection severity, time from the onset of infection, and lactation curves were also studied. Yield and composition of milk from half-udders of unilateral infected ewes were compared between them and with a set of healthy halves using a mixed model. The experiment was completed with a whole-udder approach on the same animals. To test the effect of intramammary infection (IMI) in the 7 wk following the onset of infection, 20 ewes that acquired unilateral subclinical mastitis during lactation and 40 healthy ewes were used. Another group of 20 unilaterally infected ewes from wk 1 of lactation and other 40 healthy ewes were studied to test the effect of IMI on lactational milk yield and composition. The individual milk loss in ewes infected during lactation was 15% for the 7 wk following the onset of infection, and 6.6% more milk was produced by the uninfected half to compensate milk lost by the infected half. Lactational milk yield loss in ewes infected from wk 1 postpartum was 17%. The changes in milk yield were noticed from the week of infection diagnosis. The production level of animals influenced the milk yield changes caused by IMI in such a way that the more productive ewes lost more milk, although these losses were proportional to their production level. On the other hand, infection severity affected milk loss between glands, being more pronounced as somatic cell count increased. A clear decrease of lactose content and casein:protein ratio due to subclinical IMI was observed and it remained throughout the postinfection period. Improving udder health status is necessary to maintain milk production and quality in dairy ewes during lactation.

Effect of mid-line or low-line milking systems on milking characteristics in goats

Two experiments were carried out to compare mechanical milking in mid-level (ML) and low-level (LL) milkline in goats. The first trial used 40 intramammary infection (IMI)-free goats that had been milked in ML during a pre-experimental period of 4±1 weeks post partum. These animals were divided into two groups (n=20), randomly assigning each group to ML or LL milking for a 17-week experimental period. During this period, several strategies were applied to increase teat exposure to pathogens in both experimental groups. The IMI rate was the same in both experimental groups (30% of goats), although the majority of new infections appeared earlier in ML (weeks 1-5) than in LL (weeks 7-16). Teat-end vacuum range (maximum minus minimum vacuum) was higher in ML than in LL, but no significant differences were found in the remaining variables [milk production and composition, somatic cell count (SCC), frequency of liner slips+teatcups fall off]. In the second experiment, in a crossover design (54 goats in fourth month of lactation; 2 treatments, ML and LL, in 2 experimental periods each lasting 1 week) it was observed that both the milk fractioning (reduced machine milk and increased machine stripping) and average machine milk flow worsened slightly in ML milking; in contrast, no differences were observed in total milking time or teat thickness changes after milking. It was concluded that the differences found between ML and LL are not sufficiently important to discourage breeders from using ML in goat milking.

Accuracy of BRT and Delvotest microbial inhibition tests as affected by composition of ewe's milk.

The presence of drug residues in ewes milk samples can be determined by microbial assays. The main limitation of these tests is the large number of false-positive results associated with them. False-positive results can be explained by the interaction of certain substances naturally existing in ewes milk with the growth of the microorganism used in the test. In this study, milk chemical composition (fat, protein, lactose, total solids), somatic cell counts (SCCs), free fatty acid concentrations, and lactoperoxidase system components were determined in order to investigate their influence on the rate of false-positive results for the BRT and Delvotest microbiological inhibitor tests. Milk samples were obtained after morning milking of Manchega ewes at 15, 30, 45, 60, 75, 90, 105, 120, and 135 days after parturition. The animals did not receive any kind of treatment or medicated feed throughout the experiment. The false-positive rates for BRT and Delvotest were 3.75 and 2.4%, respectively. When the logistic regression model was applied, the percentages of total solids for positive samples were significantly different from those for negative samples (16.90 versus 18.42% for BRT, 16.05 versus 18.45% for Delvotest), while the SCC logarithmic transformation was significantly higher for the positive samples than for the negative samples (5.38 versus 5.11 log units for BRT, 5.32 versus 5.11 log units for Delvotest). Moreover, Delvotest-positive samples exhibited thiocyanate concentrations higher than those of Delvotest-negative samples (8.18 mg/liter versus 6.85 mg/liter). Further analyses are needed to confirm the possible presence of antimicrobial residues in this particular type of milk sample.

Short communication: Effect of subclinical mastitis on proteolysis in ovine milk.

The aim of this work was to evaluate the effect of intramammary infection (IMI) on the endogenous proteolysis of milk. Four control checks were carried out in the half-udder milk of 10 ewes that acquired unilateral subclinical mastitis. Two of these checks were conducted before the infection was established and 2 after. Ten healthy ewes were tested as a control group. The presence of a subclinical IMI involved an increase of the products of casein hydrolysis, the proteose-peptone (p-p) fraction and minor (m) caseins, and a decrease of β-casein. As a result, a significant increase in the proteolysis index (PI), calculated as the ratio of m-casein to the sum of caseins (α + β + κ), took place. α-Casein and κ-casein were not significantly affected by IMI. Correlations confirmed the scenario: log(10) of somatic cell count (SCC) was positively correlated with p-p content and negatively with β-casein, whereas log(10) SCC was not correlated with α-casein or κ-casein. On the other hand, p-p content was positively correlated with m-casein and PI and negatively with β-casein, but no correlation was detected between p-p content and α- or κ-casein. Furthermore, between casein fractions, m-casein was only significantly correlated with β-casein. These results suggest that use of indices of proteolysis of caseins such as p-p, m-casein, and PI, could be applied together with SCC to evaluate the cheese-making quality of milk.

Effect of estrus synchronization on daily somatic cell count variation in goats according to lactation number and udder health status

Two repeated experiments were carried out in 2 different years to study the effect of estrus on somatic cell count (SCC) in dairy goats. In the first year, 36 Murciano-Granadina goats were used [12 primiparous and 24 multiparous; 22 healthy and 14 with an intramammary infection (IMI)] and, after a 6-d pre-experimental period, were divided into 2 groups according to lactation number, udder health status, SCC, and milk production. One group was kept as a control, whereas the other received an estrus synchronization hormonal treatment lasting 11d. At 24, 48, and 72h after cessation of the hormone treatment, goats were placed in contact with a buck to confirm that they were in estrus. For 32 consecutive days (6 pre-experimental, 11 in hormone treatment, and 15 post-treatment) the SCC per gland and udder were monitored in all animals. In the second year, we repeated the same experimental design using a total of 38 Murciano-Granadina breed goats (12 primiparous and 26 multiparous; 26 healthy and 12 with IMI). Throughout this experiment, milk yield and composition were also recorded daily for each goat. Upon termination of the hormonal treatment, the SCC in udder milk increased significantly in the treatment group compared with the control group over 3 consecutive days. This increase was observed for year (1 and 2), parity (primiparous and multiparous), and udder health status (healthy and IMI). The log10 SCC (cells/mL) increased from 5.5±0.09 before estrus to 6.04±0.09 during treatment; therefore, the geometric mean of the SCC increased 3.5 times during treatment. The maximum values obtained in healthy glands of primiparous goats (geometric mean=0.37 million cells/mL) were lower than in healthy glands (1.1 million cells/mL) or infected glands (1.7 million cells/mL) of multiparous goats. The increase in SCC observed during estrus (200% increase in geometric means) could not be explained by the changes in milk production, which only fell by 13%. During estrus, the percentage of protein and dry matter in the milk also increased significantly. We concluded that it is necessary to consider the presence of estrus to correctly interpret milk SCC, as an indirect method for detecting IMI or as a commercial milk quality parameter.

Variation in milk cortisol during lactation in Murciano-Granadina goats.

Fifty-seven goats were included in an experiment designed to study the effect of lactation stage, parity number, and mammary gland health status on milk cortisol concentration as a method to assess the welfare of Murciano-Granadina goats. The relationships of milk cortisol concentration with different production parameters (milk yield, milk composition, and mechanical milking ability: milk fractioning during milking and milking time) were also studied. The experiment lasted 8 mo and monthly samplings were carried out to determine total milk yield (MY), fractioning during milking (machine milk, MM; machine stripping milk, MSM), and milking time (MT), and a sample was taken from the total milk yield to determine milk cortisol concentration, somatic cell count, and milk composition (fat, protein, and lactose). To determine the infection status of the gland, an aseptic sample was taken for bacteriological analysis before each monthly sampling. Third-parity goats presented higher concentrations of milk cortisol than those of 1, 2, or ≥ 4 parities. Intramammary infection had no effect on milk cortisol concentration, and somatic cell count did not correlate with cortisol concentration. Cortisol presented a significant correlation with MY and MM, but showed no significant correlation with MSM, MT, or milk composition parameters. Variations in milk cortisol concentration in goats may be associated with different physiological factors in the animal (e.g., milk production level, lactation stage, and parity number) and therefore need not always indicate stress for the animal.

Factors affecting milking speed in Murciano-Granadina breed goats

Milk flow during the first minute of milking was analyzed using data from 1,132 Murciano-Granadina breed goats belonging to 17 herds. During the individual lactations, 2 test days were scheduled for recording several milk flow traits, total milk, milk composition (fat and protein percentages), and somatic cell count. Average lag time from teatcup attachment to arrival of milk at the milk claw (T0) was 4.9 s and at the milk meter (T1) was 15.8 s. Average milk flow after 30 s (MF0.5) was 0.29kg/30 s (0 to 1.1kg/30 s) and milk flow at 60 s or milking speed (MF1) was 0.67kg/min (0.1 to 2.1kg/min). Repeatabilities of T0, T1, MF0.5, and MF1 were 0.45, 0.58, 0.62, and 0.68, respectively. The MF1 showed high phenotypic correlation withT1(-0.63) and MF0.5 (0.90), medium values withT0(-0.42) and total milk (0.22), and very low values (-0.04 to -0.12) with fat, protein, and somatic cell count. We found no differences between flows during the first 3 lactations, with a reduction as the lactation number increased. Months in milk since parturition affected MF1, being highest in the first 3mo (0.67-0.71kg/min) and decreasing until the end of lactation (0.58kg/min). The effect of herd-test day was significant for all traits. Inclusion of all these effects for the analysis of milk flow traits is considered necessary.

Teatcups with automatic valves in machine milking of goats

This Research Paper addresses the hypothesis that using teatcups with automatic valves, without cutting off the vacuum prior to cluster removal, could increases the risk of mastitis and affect other milking variables on goats. A first trial used 46 intramammary infection (IMI)-free goats that had been milked with normal teatcups (without automatic valves) during a pre-experimental period of 8 ± 2 d postpartum. These animals were divided into two groups ( n = 23), randomly assigning each group to teatcups with automatic valves (teatcups A ) or without automatic valves (teatcups B ) for a 20-week experimental period. During this period, several strategies were applied to increase teat exposure to pathogens in both experimental groups. In the first eight weeks of the experimental period, the new IMI rate per gland was significantly higher ( P A (6 of 46; 13%) than in the group milked with teatcups B (1 of 46; 2%). However, throughout the rest of the experimental period the same number of glands appeared with new IMI ( n = 7) in both animal groups. SCC was higher in goats milked with teatcups A , but no significant differences were found in the remaining variables (milk production and composition, frequency of liner slips + teatcup fall-off). In a second experiment, in a crossover design (54 goats in fourth month of lactation, 2 treatments – teatcups A and B – in 2 experimental periods each lasting 1 week), no differences were observed in total milk, average milk flow, total milking time or teat thickness changes after milking between both teatcups. However, teatcups A worsened slightly the maximum milk flow. We concluded that the use of teatcups with automatic valves, without cutting off the vacuum prior to cluster removal, increases the risk of mastitis on goat livestock farms.

Effect of male and cooled storage time in the sperm motility rate and kinetics in Boer male goats

AIM Identify signals of fat deposition and adaptation through genome-wide scan of the Barbaresca fat-tail sheep. ANIMALS Barbaresca in an ancient Sicilian fat-tail sheep, highly endangered at present. Of the 35 000 heads of 1980, abour 1 300 are left nowadays in 20 flocks. The breed originated from crosses between Barbary sheep from North Africa and the Pinzirita breed at times of the Arab settling in Sicily (9th century). The breed is reared in a very restricted area in central Sicily on smalland medium-sized farms under a semi-extensive farming system. It is a dual-purpose breed: milk for cheese and meat. Barbaresca is one of the only two fat-tail sheep of Italy. METHODS Genotypic data were obtained with the OvineSNP50K array. Fst values of differentiation for 43072 markers were calculated in pairwise comparisons of Barbaresca with each of 13 Italian thin tail breeds. Fat-tail sheep still represent twenty-five percent of the world sheep population; they are predominant in pastoral, transhumant and low input systems. In Western countries and in high input systems they are generally endangered. Fat-tail sheep preserved genetic variability for functional adaptation. The identification of the genes with a role in the fat-tail phenotype contributes to the understanding of the physiology of fat deposition as well as the mechanisms of adaptation and is essential for maintaining future breeding options. Heritability estimates for the 1st litter size, pregnancy rate and whelping success were low (0.05-0.14)  Grading size and quality had moderate heritability estimates 0.27 and 0.21, respectively  Genetic correlations between animal grading size and fertility traits were unfavourable (from -0.15 to -0.53)  Grading quality and guard hair coverage had antagonistic relationships with all the studied fertility traits (from -0.21 to -0.54) Genetic parameters of fertility and grading traits in Finnish blue foxTrabajo presentado al: 68th Annual Meeting of the European Federation of Animal Science (EAAP). (Tallin, Estonia. 28 agosto - 2 septiembre).Trabajo presentado al: 68th Annual Meeting of the European Federation of Animal Science (EAAP). (Tallin, Estonia. 28 agosto - 2 septiembre).