Marcella Avondo

Effect of morning vs. afternoon grazing on intramuscular fatty acid composition in lamb.

The aim of this study was to assess whether different grazing management affect animal performance and meat fatty acid composition. Thirty-five lambs were divided into three groups: 12 lambs grazed from 9 am to 5 pm (8 h group); 11 lambs grazed from 9 am to 1 pm (4hAM group) and 12 lambs grazed from 1 pm to 5 pm (4hPM group). The trial was conducted over 72 days. The 8 h lambs had greater DMI (P<0.0005) and final body weight (P<0.05) than the 4hPM and 4hAM lambs while carcass weight was not different between the three groups. The meat of the 4hPM lambs contained greater (P<0.05) percentages of polyunsaturated fatty acids, C18:2 cis-9 trans-11 and lower saturated fatty acids and C18:0 than the meat of the 8 h and 4hAM lambs. It is concluded that allowing lambs to graze during the afternoon rather than during 8 h does not compromise the carcass yield and results in a healthier meat fatty acid profile.

The restriction of grazing duration does not compromise lamb meat colour and oxidative stability.

Over 72 days, 33 lambs were fed: concentrates in stall (S), grass at pasture for 8 hours (8 h), or grass at pasture for 4 hours in the afternoon (4h-PM). The 4h-PM treatment did not affect the carcass yield compared to the 8h treatment. Meat colour development after blooming was unaffected by the treatments. The 4 h-PM treatment increased the proportion of polyunsaturated fatty acids (PUFA; P<0.0005) and of the highly peroxidizable fatty acids (HP-PUFA; P<0.001) in meat compared to the 8h treatment. The S treatment increased lipid oxidation (higher TBARS values) and impaired colour stability (higher H* values) of meat over storage compared to the 8h and 4 h-PM treatments (P<0.0005 and P=0.003, respectively). No difference in meat oxidative stability was found between the 8h and the 4h-PM treatments. In conclusion, growing lambs can tolerate a restriction of grazing duration without detrimental effects on performances and meat oxidative stability.

Milk quality as affected by grazing time of day in Mediterranean goats.

We evaluated the effect of grazing time of day on goat milk chemical composition, renneting properties and milk fatty acid profile in a Mediterranean grazing system. Sixteen lactating Girgentana goats were divided into two experimental groups and housed in individual pens, where they received 500 g/d of barley grain. For 5 weeks the two groups were left to graze in two fenced plots on a ryegrass sward as follows: morning group (AM), from 9.00 to 13.00; afternoon group (PM), from 12.00 to 16.00. In selected herbage, water-soluble carbohydrates (WSC) increased in the afternoon (204 v. 174 g/kg dry matter, DM; P=0.01), whereas crude protein (CP) and linolenic acid decreased (respectively, 16.7 v. 19.8% DM; P<0.01 and 26.8 v. 30.4 g/kg DM; P<0.01). Pasture dry matter intake (DMI) was significantly higher in the afternoon (0.82 v. 0.75 kg/d; P=0.026). Fat corrected milk production (FCM), milk fat and lactose content were not affected by treatment, whereas protein and titrable acidity ( degrees SH) increased in the PM group (respectively 3.56 v. 3.42%; P=0.01; 3.55 v. 3.22 degrees SH/50 ml; P=0.01). In contrast, milk urea content was significantly higher in the AM group (381 v. 358 mg/l; P=0.037). The results seem to indicate that an improvement in ruminal efficiency might be obtained by shifting grazing time from morning to afternoon, as a consequence of a more balanced ratio between nitrogenous compounds and sugars. Indeed, the higher linolenic acid and the lower conjugated linoleic acid (CLA) (respectively 1.02 v. 0.90, P=0.037; 0.71 v. 0.81% of total fatty acids, P=0.022) in the milk of goats grazing in the afternoon seem to indicate a reduced biohydrogenation activity in the PM group.

A simple model to predict the herbage intake of grazing dairy ewes in semi-extensive Mediterranean systems

The objective of this study was to develop a model to predict herbage intake of dairy lactating ewes during grazing in semi-extensive Mediterranean systems. For this purpose a total of 670 individual intakes from 210 Comisana and Pinzirita lactating ewes were collected in Sicily over 8 years of trials. The relationships between herbage intake and characteristics of the pasture (biomass availability, DM, CP and NDF content, herbage height), the animal (live weight, milk production) and the supplement (grams of DM and CP supplied daily to each animal) were investigated. Processing of data resulted in the formulation of two linear equations diversified for two qualitative levels of the pasture recognizable from the CP content of the herbage (CP >16% DM and CP ≤16% DM). Of the variables analysed, biomass, herbage height, herbage DM content, milk production and feed supplement, expressed as grams of CP individually offered each day, were those significantly correlated with ingestion. Inclusion of these variables in the model provides good reliability in predicting ingestion. The r2 values were 0.45 for CP ≤16% and 0.54 for CP >16%.

Effect of CSN1S1 genotype and its interaction with diet energy level on milk production and quality in Girgentana goats fed ad libitum

A study was carried out to evaluate how the energy level of the diet can affect milk production and quality in Girgentana lactating goats in relation to polymorphism at the alphas1-casein (CSN1S1) genotype locus. Twenty-seven goats, homogeneous for milk production (1.5+/-0.3 kg/d), days of lactation (90+/-10 d) and body weight (35.8+/-5.5 kg) were selected on the basis of their CSN1S1 genotype, as follows: nine goats homozygous for strong (AA) alleles, nine goats homozygous for weak alleles (FF) and nine goats heterozygous (AF). The goats were used in a 3x3 factorial arrangement of treatments, with three genotypes (AA, FF, AF) and three diets at different energy levels (100%, 65% and 30% of hay inclusion). The experiment consisted of three simultaneous 3x3 Latin squares for the three genotypes, with one square for each level of hay inclusion in the diet. All the animals were housed in individual pens. Each experimental period lasted 23 d and consisted of 15 d for adaptation and 8 d for data and sample collection, during which the goats received the scheduled diet ad libitum. The animals were fed three different diets designed to have the same crude protein content (about 15%) but different energy levels: a pelleted alfalfa hay (H100) and two feeds including 65% (H65) and 30% (H30) of alfalfa hay (respectively 1099, 1386 and 1590 kcal NE for lactation/kg DM). All the diets were ground and pelleted (6 mm diameter). AA goats were more productive than AF and FF goats (respectively: 1419 v. 1145 and 1014 g/d; P=0.002). Indeed the interaction energy levelxgenotype was significant (P=0.018): in fact AA goats showed their milk increase only when fed with concentrates. Differences in protein and in casein levels between the three genotypes were in line with results expected from the different allele contribution to alphas1-casein synthesis. Milk urea levels were significantly lower in AA goats compared with AF and FF genotypes (respectively 32.7 v. 40.4 and 40.4 mg/dl; P=0.049) and significantly lower when goats were fed with 65H and 30H diets than with 100H diet (respectively 37.4 and 34.3 v. 41.7 mg/dl; P<0.001). Indeed, a significant interaction genotypexdiet (P=0.043) occurred for milk urea, which was significantly lower in AA goats but only when fed with concentrates (65H and 30H). Blood concentrations of energy indicators (glucose, non-esterified fatty acids and beta-hydroxybutyric acid) were not influenced by genotype. The results confirm that strong alleles are associated with a greater efficiency of feed utilization and seem to show that a high energy level of the diet can further improve this efficiency.

Diet selection and milk production and composition in Girgentana goats with different αs1-casein genotype

In goats, alpha s1-casein polymorphism is related to different rates of protein synthesis. Two genetic variants, A and F, have been identified as strong and weak alleles based on a production of 3.5 and 0.45 g/l of alpha s1-casein per allele. The aim of the trial was to test whether goats can select their diet as a function of their genetic aptitude to produce milk at different casein levels and whether this selection can influence milk production or composition. Two groups of 8 animals, homozygous for strong (AA) or weak (FF) alleles were housed in individual pens. Using a manger subdivided into five separate containers, the goats were offered daily for 3 weeks: 1.5 kg of alfalfa pelleted hay, 0.7 kg of whole barley, 0.7 kg of whole maize, 0.7 kg of whole faba bean and 0.7 kg of pelleted sunflower cake. Total dry matter intake was similar between groups and resulted in nutrient inputs much higher than requirements. On average, goats selected 86% of maize plus barley and only 46% of faba bean plus sunflower. Indeed, AA goats selected less faba bean compared with FF goats (37.2 v. 56.7% of the available amount; P=0.01); during week 2 and week 3 they significantly increased maize selection (respectively for week 2 and week 3: 94.9 and 99.1% v. 85.3 and 87.3%) thus increasing the ratio between the high-energy feeds and the high-protein feeds (2.41 v. 1.81, P=0.023). As for true protein, the high soluble fraction (B1) and the indigestible fraction (C) were lower in the diet selected by AA goats (respectively in AA and FF groups: B1, 7.85 v. 9.23% CP, P<0.01; C, 6.07 v. 6.30% CP, P<0.001); these diet characteristics can be associated with lower losses of protein. Milk production, being similar in AA and FF groups when goats were fed with a mixed diet, significantly increased in AA group, when free-choice feeding was given (mean productions: 1198 v. 800 g/d, P<0.01). Casein content was higher in AA group than in FF group (2.70 v. 2.40%, P<0.01) whereas milk urea was higher in FF group (59.7 v. 48.8 mg/dl, P<0.01). In conclusion, when the animals were free to select their diet, their higher genetic aptitude to produce casein seemed to adjust their energy and protein dietary input in qualitative terms, thus leading to an increase in milk production and a decrease in milk urea. These results seem to demonstrate that interactions probably occurred between genetic polymorphism at the alpha s1-casein locus, diet selection and the efficiency of nutrient transformation into milk.

Models for estimating feed intake in small ruminants

This review deals with the most relevant limits and developments of the modeling of intake of sheep and goats reared intensively and extensively. Because small ruminants are normally fed ad libitum, voluntary feed intake is crucial in feeding tactics and strategies aimed at optimal animal production. The effects of genetic, neuroendocrine, hormonal, feed and environmental factors on voluntary feed intake were discussed. Then, several mathematical models to estimate dry matter intake (DMI) were examined, with emphasis on empirical models for sheep and goats in intensive farm systems or in extensive areas under pasture or rangeland conditions. A sensitivity analysis of four models of prediction of DMI in housed lactating dairy sheep and meat sheep breeds was also presented. This work evidenced a large variability in the approaches used and in the variables considered for housed sheep and goats. Regarding the estimation of feed intake for grazing sheep and browsing goats, the accuracy of estimates based on empirical models developed so far is very low when applied out of the boundaries of the studied system. Feeding experiments indoors and outdoors remain fundamental for a better modeling and understanding of the interactions between feeds and small ruminants. However, there is a need for biological and theoretical frameworks in which these experiments should be carried out, so that appropriate empirical or mechanistic equations to predict DMI could be developed.

The volatile compounds in lamb fat are affected by the time of grazing

This study was designed to assess whether different grazing managements affect the appearance of organic volatile compounds (VOC) in lamb fat. Forty-two lambs were divided into four groups: 9 lambs were restricted in stall and fed concentrate (S group); 12 lambs grazed from 9 am to 5 pm (8h group); 10 lambs grazed from 9 am to 1 pm (4 hAM group) and 11 lambs grazed from 1 pm to 5 pm (4 hPM group). After 72 days on feed the animals were slaughtered and the perirenal fat subjected to SPME-GC/MS analysis of VOC; the data were analyzed by stepwise discriminant analysis. The 6-methyl-2-heptanone and furanone, 2,5-dimethyl, 4-hydroxy-3(2H) allowed discrimination between the 4 hAM and the 4 hPM animals. These are the first results indicating that the time of the day in which the animals are allowed to graze affects the appearance of VOC in lamb fat.

Effects of shearing and supplemental level on intake of dry ewes grazing on barley stubble

Twenty-eight Comisana dry ewes were utilised to evaluate the effect of shearing (14 shorn and 14 unshorn ewes) and supplemental level (100 and 300g of concentrate) on intake of barley stubble. Shorn ewes showed a small increase in dry matter intake (at the end of August: 1.32 vs. 1.10kg/day; p<0.01). Intake of barley stubble decreased as supplement level increased (mean: 1.18 vs. 1.29; p<0.01). On average, substitution effect was 0.63. Total lamb weight per ewe was greater in the group receiving 300g of concentrate (7.38 vs. 5.85; p<0.05). Shearing induced a small, but not significant decrease in total lamb weight per ewe (6.18 vs. 7.05kg/ewe). Results seem to indicate that unshorn ewes react better to environmental stress and that 300g improve reproductive performance.

Prediction of feed intake in the Italian dairy sheep

Abstract Recommendations on feed intake for sheep are based on assessments of genetic types, feeding systems and environmental conditions that are very different from Italian ones. These considerations underline the need for intake data or models that derive from local trials. For this reason intake data of lactating and dry ewes, pregnant ewes, rams and growing lambs have been collected from selected literature based on sheep feeding trials mainly conducted on dairy breeds in Italy or in other Mediterranean countries. Equations and intake tables differentiated according to the physiological and productive categories, as well as feeding typology are reported. Particular consideration is given to pasture intake with supplementation, reporting three equations developed for three qualitative levels of the pasture, recognizable from the CP content of herbage: < 10% DM; ≥ 10% and ≤ 16% DM; >16% DM. The equations include animal and pasture variables and supplementation, expressed as grams of CP given with feeds other than pasture. Only when pasture CP content is lower than 10% DM, supplement is not included in the equation, as no or negative substitution effect is expected.