The hazelnut skin is waste biomass rich in bioactive compounds that may affect lipid rumen metabolism, ruminant performance, and products’ quality. Therefore, we investigated the effect of dietary hazelnut skin on milk production and composition and on rumen fatty acids in ewes. During 28 days, 20 Comisana lactating ewes received alfalfa hay ad libitum plus 800 g/head/day of pelleted concentrate containing 36% dried beet pulp (CTRL group; n = 10) or 36% hazelnut skin (HS group; n = 10). The protein percentage was lower in HS milk. Milk fatty acids (FA) partially reflected those of rumen content. Total saturated FA (SFA), odd and branched-chain FA, and n-3 polyunsaturated FA (PUFA) were greater in CTRL milk. Total monounsaturated FA (MUFA) and 18:1 trans were greater in HS milk; moreover, HS milk showed a double percentage of oleic acid than the CTRL group. Individual SFA were greater in CTRL milk except for 18:0. Differing from the rumen content, total PUFA, n-6 PUFA, and 18:2 n-6 were comparable between groups. Vaccenic and rumenic acid were greater in HS milk. To conclude, dietary HS slightly reduced milk protein percentage but improved atherogenic index and healthy FA in milk. The content of the somatic cells suggested a healthier udder in the HS group.

Pomegranate pulp, a by-product of the pomegranate juice industry, contains a remarkable quantity of bioactive compounds that can favorably affect ruminant metabolism and milk quality. The present paper investigated the effect of dietary pomegranate pulp on milk yield and quality during late lactation in grazing ewes. Twenty Comisana ewes (150 ± 10 days in milk) were subdivided into control (CTRL) and pomegranate (PP) groups. The CTRL group received a corn-barley based concentrate, while the PP group received a concentrate containing 64.8% pomegranate pulp. Dietary treatment did not affect milk yield. CTRL milk had a greater percentage of β-casein and total casein, while α_s1-casein percentage tended to be greater in the PP group. The PP milk showed a lower percentage of 14:0, 16:0, but a greater percentage of vaccenic, rumenic, and α-linolenic acid. Punicic acid was detected only in the PP milk. Total antioxidant capacity (ORAC) was greater in the CTRL milk as compared with the hydrophilic ORAC. Dietary pomegranate pulp increased milk health quality with no detrimental effects on milk yield. Therefore, pomegranate pulp could represent a strategy for improving milk quality and reducing feeding cost during a less profitable phases such as late lactation. Also, dietary pomegranate pulp, as an alternative to traditional feedstuffs, may lower feed-to-food competition in livestock production.

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 (°SH) increased in the PM group (respectively 3·56 v. 3·42%; P=0·01; 3·55 v. 3·22°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.

In goats, α_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 α_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 (37·2v. 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 (2·41v. 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, 7·85v. 9·23% CP,P<0·01; C, 6·07v. 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: 1198v. 800 g/d,P<0·01). Casein content was higher in AA group than in FF group (2·70v. 2·40%,P<0·01) whereas milk urea was higher in FF group (59·7v. 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 α_s1-casein locus, diet selection and the efficiency of nutrient transformation into milk.

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 α_s1-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 3×3 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 3×3 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: 1419v. 1145 and 1014 g/d;P=0·002). Indeed the interaction energy level×genotype 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 α_s1-casein synthesis. Milk urea levels were significantly lower in AA goats compared with AF and FF genotypes (respectively 32·7v. 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 34·3v. 41·7 mg/dl;P<0·001). Indeed, a significant interaction genotype×diet (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.

The study investigated the effects of a polymorphism at the LEP gene intron 1 microsatellite region and its interaction with diet energy level on feed intake, milk traits, milk fatty acid composition, and metabolic state in goats. Sixteen Girgentana lactating goats at mid-lactation, selected on the basis of their genotype (8 goats homozygous 266 bp/266 bp, L genotype; 8 goats heterozygous 266 bp/264 bp, H genotype), were fed ad libitum according to a change-over design, with two diets at different energy levels reached with different hay inclusion: low energy diet (LE)—100% of hay; and high energy diet (HE)—65% of hay. No differences in milk yield and composition or in dry matter intake were found between leptin genotypes or between diets. Leptin genotype had no effect on plasma metabolite concentrations. The differences between diets were recorded for plasma β-hydroxybutyric acid (BHBA) concentrations with higher (p = 0.01) values for the HE compared to the LE diet (0.44 vs. 0.24 mmol/L, respectively). Nonesterified fatty acid (NEFA) values seem to indicate a positive energy balance in goats. No interaction genotype per diet was evident for most of the studied parameters. Fatty acid composition was strongly influenced by LEP genotype: L goats, compared to H goats, showed higher levels of monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and 14:1/14:0 desaturation index; lower levels of saturated fatty acids (SFA); and a more favorable atherogenic index. These results seem to suggest an improvement of health characteristics of milk with the L genotype.