Maria Grazia Maianti

Seasonal variations of some enzyme activities of cow milk

Riassunto Variazioni stagionali di alcune attività enzimatiche del latte bovino. La ricerca è stata condotta presso un allevamento commerciale di bovine Frisone italiane. La prova è iniziata in marzo ed è terminata nel febbraio dell’anno successivo. I controlli hanno riguardato il latte di massa (ogni 15 giorni) ed il latte individuale (ogni mese) di 21 bovine equamente distribuite in tre diverse fasi della lattazione (30-60, 80-120 e 150-200 giorni di lattazione). Le analisi sul latte hanno riguardato i macrocomponenti, le cellule somatiche, il pH e l’acidità titolabile, l’affioramento del grasso, la lattodinamometria, la velocità di acidificazione, i tiocianati, l’attività di lattoperossidasi, GOT, GGT e LDH. Per tutti i parametri controllati, con eccezione di grasso e lattoperossidasi, si sono osservate variazioni stagionali significative. Nella stagione estiva, oltre alle note variazioni nei macrocomponenti, acidità e parametri reologici, si sono osservati valori significativamente più bassi di tiocianati e di GGT e significativamente più elevati di GOT ed LDH.

Effect of some disease stress on cow milk yield and features

Riassunto Effetti indotti da diversi problemi di salute sulla produzione e caratteristiche del latte bovino. 9 bovine con problemi infiammatori sono state divise in due gruppi in funzione del calo di ingestione di alimenti e produzione di latte: 5 non hanno evidenziato alcun calo (IG); 4 un calo marcato (AG). Il latte è stato controllato per 21 giorni prima e 21 dopo l’evidenza dei problemi. In entrambi i gruppi nel periodo di manifestazione dei problemi il tenore in proteina del latte non è variato, l’acidità è diminuita significativamente, mentre le caratteristiche reologiche sono peggiorate e in AG questo si è protratto sino a 7 giorni dopo. A livello delle frazioni proteiche la variazione che parrebbe giustificare questo peggioramento è stata la riduzione della β-caseina, osservata in entrambi i gruppi e solo in AG sino al termine dei controlli. I dati ottenuti confermano che lo stress infiammatorio determina condizioni che modificano le caratteristiche del latte, tra cui anche la frazione proteica, e che le alterazioni sono più marcate in concomitanza di fenomeni di anoressia.

Effect of a different concentrate-forage sequence on digesta passage rate, faeces traits and milk features of dairy cows

Abstract To ascertain the effects of a different feed sequence, which could modify digestion rate and sites as well as metabolic - endocrine status and milk features, 6 lactating dairy cows have received the same diet with a different time of concentrate administration when close to the two daily forage meals: 30’ before or 60’ after them. Cows were tied in a barn with controlled temperature, humidity and light, individually fed and monitored for: daily dry matter intake, milk yield and its features at 2 milkings, concentrate passage rate and faecal traits. The results have showed that DMI, feeding behaviour, milk yield and milk features were not significantly affected (except fat content, increased when forage was supplied as first feed). The digesta passage rate was also different: concentrate escaped more rapidly from the rumen when fed before forage or 4 hours after them. This effect has not modified the faeces, but some endocrine and /or metabolic changes can be hypothesized, because milk fat content was increased when concentrate was supplied after forage.

Application of FT-IR spectroscopy to analyze casein in cow milk

Abstract Infrared spectrometry is, at present, the most frequently applied methodology for the composition analysis of milk and dairy products. The determination of fat, protein and lactose has been described during recent decades. The introduction of Fourier Transform Infra-red (FT-IR) technology in combination with the application of multi-dimensional procedures (i.e. principal component regression, partial least squares) has improved this methodology, opening new perspectives for the simultaneous and routinely determination of many new parameters such as casein, urea, specific sugars, etc.. The aim of our study was to develop on MilkoScanTM FT 120 (Foss Electric, Hillerød, Denmark) a calibration curve for the analysis of casein in cow milk and to execute a preliminary validation. The calibration curve was developed on 89 individual milk samples collected from 4 dairy herds in the Grana-Padano cheese district. In order to obtain a higher variability of milk protein content and composition, in each herd milk samples from cows in early and late lactation were collected. On milk samples, casein separated at pH 4.6 and protein content were measured using Kjeldahl method (N x 6.38) and the results, expressed as casein percentage of whole milk, were used as reference values. On each milk sample the full spectra with MilkoScanTM FT 120 was collected twice. The samples were sorted according to casein content and homogenously subdivided in two data subset: the 1st (2/3 of the samples) was used to develop the calibration curve; the 2nd (1/3 of the samples) was used, as external dataset, to validate the calibration curve by cross validation. These elaborations were performed using Regression and Partial Least Squares procedures of SAS. The casein content in milk samples used to develop the calibration curve ranged between 2 and 3.5% (w/v) with a mean value of 2.64%. The calibration curve that better fits the casein reference values considers 13 different wavelength areas included in 7 factors. The standard error of the calibration curve was 0.054 as absolute value and 2% as relative value. The intercept of this curve was 0.0001 with a slope of 0.999. Also the standard error of prediction obtained with the cross validation using the external dataset was very low (0.057). The intercept and the slope of the validation curve were close to the optimal values and respectively 0.1 and 0.97. The repeatability parameters, evaluated on all samples, were very low (sr=0.011 as absolute value and RSDr=0.42% as relative value). The results obtained in this study, considering the scarcity of literature information in this area, seem very promising. The calibration curve, after a better validation in different conditions, could be included in the milk routine analysis with different purposes.

Effect of diets with different content of starch and protein fed to dairy cows in early lactation on milk yield and traits

Abstract With the aim to study the effect on milk yield and its traits of 2 different levels of fermentable carbohydrates (LS: 25.5%, and HS: 29.5% DM) combined with 2 protein levels (LP: 15.5% and HP: 16.5% DM), 4 Italian Friesian dairy cows in early lactation housed in a tied stall were used. The experimental diets were obtained adjusting in 4 supplements the proportion of high energy fibrous (beet pulp, soybean hull) or starchy (corn meal) feeds and of meal protein more (soybean meal) or less (Soy-Pass®: xylose-treated soybean meal) degradable. The highest DMI was observed in HSHP which showed also a low content of NDF. Milk yield resulted over 45 kg/d throughout the study and higher when HSHP diet was fed (46.1 kg). Milk fat was always at high level and the lowest value (3.89%) with HSHP and the highest (4.08%) with LSLP were observed. The diets did not modified milk protein (their average levels resulted of 3.25%) and lactose content. Milk acidity and renneting traits were higher when HSLP was fed, and resulted at adequate levels when all the diets were fed. When the diets for dairy cow are formulated to cover the animal requirements and respect their digestion physiology, it is possible to reach high milk yield level and maintaining, at the same time, a high milk quality .