Rosanna Lombardelli

Some new aspects of nutrition, health conditions and fertility of intensively reared dairy cows.

Abstract Speaking in terms of the general relationship between nutrition and reproduction, many different aspects are more or less involved depending on geographical areas, species, production systems, technological levels etc. There are deficiency conditions: energy, proteins, vitamins and minerals; but also some excesses (namely protein and few minerals) or toxic substances such as micotoxins or plant compounds (i.e. phyto-oestrogens). Their relevance is different in the intensive systems for better feeds and relative easiness to create appropriate diets. Nevertheless, intensification does not reduce the nutritional risks for livestock reproduction for several reasons: namely, a suspected higher susceptibility of high genetic merit cows to the usual stresses. There is also a new risk: metabolic stress (e.g. negative energy balance). The latter is particularly relevant when early lactation and new pregnancy are close (as in dairy cows), however, of great importance are also oxidative stress and disease stress (pro-inflammatory cytokines). In dairy cows, inflammatory phenomena around calving - when an immune response occurs in spite of clinical symptoms are missing - are significantly related to a lower pregnancy rate. A possible explanation can be seen in the pro-inflammatory cytokines, which modify liver synthesis and seem to impair energy balance thereby reducing feed intake and increasing energy expenditure. This suggests that in order to improve fertility not only better feeding mecahnisms, but any husbandry tool that can reduce diseases and health disorders are needed.

Relation of inflammation and liver function with the plasma cortisol response to adrenocorticotropin in early lactating dairy cows

In this study we examined the relationship between cortisol and inflammatory status in early lactating dairy cows after a stimulation test of the adrenal cortex. Twenty-four cows were grouped into quartiles (6 cows per each quartile) in accordance with the liver activity index (based on plasma concentration of negative acute phase proteins in early lactation); the quartiles were lower (LO; cows with the lowest liver functionality), intermediate lower, intermediate upper, and upper (UP; cows with the highest liver functionality). Each cow was injected i.v. with 20 µg of a synthetic analog of ACTH at 35 d in milk (DIM). Blood samples were taken to assess inflammatory status, and at 0, 30, and 60 min after ACTH challenge to measure total cortisol. The free cortisol fraction was analyzed in the LO and UP quartiles and the bound cortisol fraction was estimated as the difference between total and free cortisol. The LO, in comparison with the other quartiles, suffered a more severe inflammatory status, with the highest values of haptoglobin, reactive oxygen metabolites, and total nitric oxide metabolites and the lowest concentration of direct or indirect markers of negative acute phase proteins. The cows in the LO quartile had the highest values of plasma nonesterified fatty acids and β-hydroxybutyrate at 7 DIM, suggesting a more severe body lipid mobilization. The LO quartile cows showed the highest frequency of health problems and the lowest milk yield in the first 35 DIM. Thirty minutes after the ACTH treatment, the concentration of total cortisol was lower in LO in comparison to other groups. Similarly, the bound cortisol fraction was lower in LO versus UP. The adrenal response appeared inversely related with health status after calving (e.g., lower in LO cows, experiencing the most severe inflammatory status). The lower increase in cortisol after the ACTH challenge in cows with greater inflammation (LO quartile) seems a consequence of the lower availability of cortisol-binding globulin synthetized by the liver, but other mechanisms can be involved (e.g., rate of cortisol production, secretion, and metabolic clearance). Our data provide evidence that inflammation and metabolic changes reduce the concentration of circulating plasma cortisol during an acute stress. Hence, the acute phase response in dairy cows should be taken into account to interpret the results obtained from stimulation tests of the adrenal cortex.

Plasma cortisol variations in dairy cows after some usual or unusual manipulations

Riassunto Variazioni del cortisolo ematico in bovine da latte a seguito di varie operazioni di stalla. Con lo scopo di meglio chiarire le interferenze sulla cortisolemia dovute alle tecniche di prelievo, alla manipolazione degli animali ed all’interazione uomo/bovina, sono state realizzate 4 prove per valutare l’effetto delle seguenti operazioni: prelievo ematico in bovine abituate o meno alla presenza umana, pulizia, mungitura, pesata e mascalcia. I valori basali di cortisolo hanno evidenziato l’usuale variabilità. Dopo 15 minuti dall’inizio delle operazioni la cortisolemia ha mostrato generalmente un picco. L’aumento è stato maggiore negli animali non avvezzi all’interazione con l’uomo ed in rapporto alla “invasività” delle operazioni; anche tra quelli assuefatti si è peraltro riscontrata una notevole variabilità della risposta. La valutazione della cortisolemia nella bovina da latte richiede grande cautela e una meticolosa standardizzazione metodologica.

Change of digesta passage rate in dairy cows after different acute stress situations

Abstract Six dairy cows received 3 treatments after morning meal, in a double Latin square design. Treatments were ACTH challenge (SYN), hoof trimming (TRIM) and saline (CTR). Measurements included: plasma cortisol and metabolic profile during the 24 h after treatments; the rate of digesta passage, faecal dry matter and pH. Both acute stress situations vs CTR caused a rapid and similar rise in plasma cortisol (P<0.001), while plasma glucose increased only in response to TRIM. Plasma concentrations of urea and BHB were increased for several hours after both stress situations. Most importantly, the transit time of digesta was reduced with SYN and TRIM (P<0.05). Our data demonstrate a reduced forestomach motility during acute stress and confirm a possible negative linkage between stress and gut functions, perhaps independent of diet composition. The mechanism seems linked to increased ACTH or cortisol rather than corticotrophin-releasing factor.

Adrenal responsiveness to a low-dose ACTH challenge in early and late lactating dairy cows.

To improve the evaluation of the chronic stress conditions, the adrenal responsiveness to low dose ACTH stimulation, in different lactation stages, was checked in 56 multiparous dairy cows from 2 herds (25-350 days in milk). Cows were retrospectively ranked in 3 stages: early (<75) average (75-150) and late (<150 DIM) lactation. Herd B (vs. herd A) showed higher basal cortisol and frequency of inflammation. Early stage (vs. others) showed higher basal cortisol, bilirubin, ceruloplasmin and haptoglobin, as well as lower ones of cholesterol and lower rise of plasma cortisol during ACTH challenge (P< 0.001). Cortisol peak was also correlated negatively with ceruloplasmin, bilirubin, ROM, and positively with cholesterol, vitamin A and E. Both, basal cortisol and cortisol response to ACTH, are associated to inflammation but in opposite way: basal cortisol positively and cortisol response negatively. This latter results are likely due to lower transcortin synthesis, that could be ensued in early lactating cows suffering inflammation.

Basal levels and diurnal variations of some hormones and metabolites in blood of dairy cows treated daily with rbSTin early and late lactation

Abstract The variations of basal value (before morning feeding at 3-4 days interval) and daily pattern (on 4th and 18th day of treatment with 8 blood collections within 24h) of hormones and metabolites were studied in four dairy cows; 2 in early and 2 in late lactation, which were alternatively injected daily for a period of 21 days with 26.3 mg rbST or saline. The rbST injection significantly increased the basal and daily levels of GH, IGF-I in both stages of lactation. Daily levels of NEFA were significantly increased by rbST in both stages of lactation and their variations, due to the effect of meals, were counteracted by the rbST; the higher level of NEFA allowed a greater sparing of glucose, the blood level of which resulted higher (P<0.05) in late lactation (mainly for less lactose yield), as well as a sparing of amino acid that resulted in a lower blood urea level (P<0.05, only in late lactation). Moreover, these metabolic changes in late lactating cows, and in particular the high availability of glucose, determined a significantly higher blood level of insulin and T3, and lower level of glucagon. Despite the similar GH, IGF-I and NEFA increases observed in the cows treated in early and late lactation, other metabolic and endocrine consequences resulted more evident in late lactation. Furthermore, some of these variations were affected by the forage meals. It can be concluded, therefore, that the changes occurring in the blood subsequent to a rbST treatment are not equal to those which occur at the start of lactation; moreover, they are affected by the daily feeding pattern and perhaps by the stage of lactation.

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.