Salvatore Pier Giacomo Rassu

The mathematical description of lactation curves in dairy cattle

This review gives an overview of the mathematical modelling of lactation curves in dairy cattle. Over the last ninety years, the development of this field of study has followed the main requirements of the dairy cattle industry. Non-linear parametric functions have represented the preferred tools for modelling average curves of homogeneous groups of animals, with the main aim of predicting yields for management purposes. The increased availability of records per individual lactations and the genetic evaluation based on test day records has shifted the interest of modellers towards more flexible and general linear functions, as polynomials or splines. Thus the main interest of modelling is no longer the reconstruction of the general pattern of the phenomenon but the fitting of individual deviations from an average curve. Other specific approaches based on the modelling of the correlation structure of test day records within lactation, such as mixed linear models or principal component analysis, have been used to test the statistical significance of fixed effects in dairy experiments or to create new variables expressing main lactation curve traits. The adequacy of a model is not an absolute requisite, because it has to be assessed according to the specific purpose it is used for. Occurrence of extended lactations and of new productive and functional traits to be described and the increase of records coming from automatic milking systems likely will represent some of the future challenges for the mathematical modelling of the lactation curve in dairy cattle.

Effect of extruded linseed supplementation on blood metabolic profile and milk performance of Saanen goats

This study assessed the effects of dietary supplementation with extruded linseed on milk yield and composition, milk fatty acid (FA) profile and renal and hepatic metabolism of grazing goats in mid-lactation. Forty Saanen goats were divided into two isoproductive groups: one group was fed the control diet (CON) composed of hay and pelleted concentrate and the other group was supplemented with additional 180 g/day of extruded linseed (LIN; dry matter basis), which supplied 70 g/day of fat per head for 9 weeks. Animals grazed on pasture for ∼3 h/day after the first of the 2 daily milkings. Milk samples were collected weekly and analyzed for fat, protein, lactose, milk urea nitrogen (MUN) and somatic cell count. Blood samples were collected every 2 weeks and analyzed for total bilirubin, creatinine, aspartate transaminase (AST), alanine transaminase (ALT), gamma glutamyl transpeptidase, alkaline phosphatase, total protein and urea nitrogen. Milk yield was higher in the LIN than in the CON group (2369 v. 2052 g/day). LIN group had higher milk fat (37.7 v. 33.4 g/kg) and protein (30.7 v. 29.1 g/kg) concentration and lower MUN (35.0 v. 43.3 mg/dl) than CON group. Goats fed LIN had greater proportions of 18:1 trans11, 18:2 cis9trans11 and total polyunsatured fatty acids n-3 in milk fat, because of higher 18:3n-3 and 20:5n-3 FA, and lower proportions of short- and medium-chain FAs than goats fed CON. All kidney and liver function biomarkers in serum did not differ between dietary groups, except for AST and ALT, which tended to differ. Extruded linseed supplementation to grazing mid-lactating goats for 2 months can enhance the milk performance and nutritional profile of milk lipids, without altering the general hepatic and renal metabolism.

Monitoring the on-farm welfare of sheep and goats

Abstract Schemes for on-farm welfare assessment in sheep and goats are not yet available. Factors responsible for this lack of availability are discussed in the first part of this review. Requisites for reliable methods of welfare assessment to be used in sheep and goat farms are discussed, taking into account the peculiarities of the small ruminant production systems in terms of flock management and farm location. Some housing parameters related to structures, design and micro-environment are reviewed and could be included in schemes of welfare assessment on farm. Human-animal interaction, health status of the animals in terms of body condition scoring, skin and hair conditions, lameness and injuries, and management practices in relation to cleanliness, animal handling and moving, milking procedures and abnormal behaviours, are proposed as potential animal-based indicators. When available, validity, reliability and feasibility of the proposed parameters are discussed. The voluntary adhesion to welfare standards in Sardinia and the application of a scientifically validated protocol in Basilicata are reported as examples of practical experiences.

Excretion pattern of aflatoxin M1 in milk of goats fed a single dose of aflatoxin B1.

The feedstuffs used in dairy animals must be able to give consumers confidence about the wholesomeness of milk with regard to aflatoxin contamination. The aim of this study was to determine the excretion patterns of aflatoxin M(1) (AFM1) in the milk of dairy goats fed a single dose of pure aflatoxin B(1) (AFB1), which can occasionally occur if feeds are infected by hot-spot growth of molds that produce aflatoxins. Five dairy goats in midlactation were administered 0.8 mg of AFB1 orally. Individual milk samples were collected for 84 h after AFB1 dosage. Aflatoxin M(1) was found in milk in the highest concentration. In all goats, AFM1 was not detected in milk before AFB1 administration, but was detected in the first milking following AFB1 administration. The excretion pattern of AFM1 concentration in milk was very similar in all goats even if the values of the concentration differed between animals. The peak values for AFM1 concentration in milk was observed in milk collected during the milking at 3 and 6h. After the peak, the AFM1 in milk disappeared with a trend that fitted well a monoexponential decreasing function, and the toxin was not detected after 84 h. Only about 0.17% of the amount of AFB1 administered was detected as AFM1 in milk, and about 50% of this was excreted in the first liter of milk yielded after AFB1 intake. Correct procedures to prevent growth of molds, and consequent AFB1 contamination, on the feedstuffs for lactating goats represent the key to providing consumers a guarantee that milk is not contaminated by AFM1.

Non-nutritional factors affecting lactation persistency in dairy ewes: a review

Abstract Milk production is largely related to the shape of the lactation curve. Key elements of the lactation pattern are peak yield, which is the maximum daily yield reached during lactation, and lactation persistency, which is the medium rate of milk yield decrease after the lactation peak. The ideal lactation curve should have a reasonably high peak and a flat trend afterwards. A more persistent lactation is desirable because it is related to better animal health and reduction of feeding costs. Effective strategies to improve lactation persistency require a deep understanding of the main factors that affect this trait, including genetics, hormonal status and administration, udder morphology, seasonal changes, management, animal health (e.g. mastitis), stress and nutrition. This review covers the effects of non-nutritional factors on lactation persistency in dairy sheep.

Influence of outdoor and indoor rearing system of suckling lambs on fatty acid profile and lipid oxidation stability of raw and cooked meat

Effect of outdoor (OUT) or indoor (IND) rearing systems (RS) of 48 male and female Sarda suckling lambs on fatty acid (FA) composition and lipid oxidation of raw and cooked meat was studied. Ewes grazed daily on natural pasture for 6 h. During grazing time of ewes, IND lambs were kept indoors whereas OUT lambs followed the mother. Slaughter age was 28 days. RS did not affect meat chemical composition, pH, cooking loss and FA profile. Microwave cooking changed markedly the concentrations of almost all meat FAs and FA classes: short (-28%) and medium chain fatty acids (-11%), saturated fatty acids (-7.6%), odd-number carbon and branched-chain FA (-11.8%), proportion of long chain fatty acids (+5.3%) and PUFAn3 (+37.3%) and PUFAn6 (+26.1%) class. Sex influenced significantly the concentration of the main odd-number carbon and branched chain fatty acid. OUT rearing system increased MDA concentration (P<0.01). RS × cooking interaction affected PUFA and MDA, which were higher in cooked samples of OUT than IND lambs. The results evidenced that the meat composition of suckling lambs is affected by the feeding system of the mother rather than the management system of lambs.

The effect of different time epoch settings on the classification of sheep behaviour using tri-axial accelerometry

Abstract Monitoring behaviour of grazing animals is important for the management of grazing systems. A study was run to discriminate between the main behaviours (grazing, ruminating and other activities) of sheep at pasture wearing a halter equipped with an accelerometer (BEHARUM device), and to identify the epoch setting (5, 10, 30, 60, 120, 180 and 300 s) with the best performance. The BEHARUM device includes a three-axial accelerometer sensor and a force sensor positioned under the lower jaw of the animal. The halter was fitted to eight Sarda dairy sheep that rotationally grazed either a spatial association (mixture) or a time association of berseem clover ( Trifolium alexandrinum L.) and Italian ryegrass ( Lolium multiflorum Lam.) for 6 h day −1 . The behaviour of the animals was also video-recorded. The raw acceleration and force data were processed for each epoch setting to create 15 variables: the mean, variance and inverse coefficient of variation (ICV; mean/standard deviation) per minute for the X-, Y-, Z-axis and force, and the resultant. Multivariate statistical techniques were used to discriminate between the three behavioural activities: canonical discriminant analysis (CDA), and discriminant analysis (DA). To validate the derived discriminant functions, a bootstrap procedure was run. To evaluate the performance of DA in discriminating between the three activities, the sensitivity, specificity, precision, accuracy and Coehn’s k coefficient were calculated, based on the error distribution in assignment. Results show that a discriminant analysis can accurately classify important behaviours such as grazing, ruminating and other activities in sheep at pasture. The prediction model has demonstrated a better performance in classifying grazing behaviour than ruminating and other activities for all epochs. The 30 s epoch length yielded the most accurate classification in terms of accuracy and Coehn’s k coefficient. Nevertheless, 60 and 120 s may increase the potential recording time without causing serious lack of accuracy.

Machine milking management and milk nitrogen fractions in primiparous ewes

Abstract Little work has been carried out on management techniques to reduce stress of first machine milking in ewes. The aim of this work was to evaluate the effect of milking parlour training before weaning on sheep milk yield and milk protein fractions. One week before weaning, an experimental group (EG) was introduced into the machine milking parlour and hand-milked once a day, to adapt them to the new environment and noise of the milking machine, while a control group (CG) was hand-milked once a day in a traditional fold parlour until weaning. After weaning, both groups were machine milked, separately, twice a day in the milking parlour. Milk yield and nitrogen fractions were recorded for the first 10 days of machine milking. Differences between samplings within group were observed for all parameters considered. Only on the first day of machine milking, differences between groups occurred for total nitrogen, total protein and casein. Higher content of nitrogen fractions in the milk of EG was due to its lower milk production. In fact, daily production of nitrogen fractions was higher in CG than in EG. High variability for most parameters was observed during the first 5 days of machine milking in both groups. A week of training to machine milking parlour was not enough to reduce the negative effects of weaning and machine milking stresses on primiparous ewes. (interaction?)