Relationships between dietary factors and milk urea nitrogen level in goats grazing herbaceous pasture

Long-Term Feeding of Dairy Goats with 40% Artichoke by-Product Silage Preserves Milk Yield, Nutritional Composition and Animal Health Status

The aim of this work is to study the effect of 40% inclusion of artichoke by-product silage (AB) in dairy goat diets on milk yield, composition and animal health status during a full lactation period compared to an isoenergetic and isoproteic mixed ration based on alfalfa hay and a cereal and legume mixture. Milk yield was not affected by the dietary treatments, and neither was body weight. AB treatment reduced whey protein (0.38 vs. 0.42%, p < 0.05) and milk urea concentrations (687 vs. 773 mg/L, respectively, p < 0.001), and did not affect total true protein (3.22 vs. 3.24% p > 0.05) or other macro-composition variables. AB treatment showed higher milk concentrations of Ca (p < 0.05), Mn (p < 0.01), Cu (p < 0.01) and Zn (p < 0.001) compared to the control group (C). Slight differences were observed in milk fatty acid profile without any negative effects (p > 0.05) on the blood cholesterol and glucose of goats. The AB group reduced blood urea due to its high dietary total phenol content. However, it had a positive effect on β-hydroxybutyrate (p < 0.05) and nonesterified fatty acids (p > 0.05). It was concluded that 40% artichoke by-product inclusion in dairy goat feed for the whole lactation period (23 weeks) is a sustainable solution, reducing feeding cost by 12.5% per kg of dry matter, contributing to a better circular economy without any negative repercussions on the productivity and health of Murciano-Granadina dairy goats.

Seasonal Variations of Milk Composition of Sarda and Saanen Dairy Goats

Traditionally, in Mediterranean areas the goat population was composed of autochthonous breeds with strong milk production seasonality. In the last decades, high productive alpine breeds were introduced together with more widespread out-of-season milk production practices. This study is a large-scale survey on the seasonal variations of the main compositional characteristics of goat milk obtained from Sarda and Saanen breeds reared on the Mediterranean island of Sardinia (Italy). Analysis of data indicated that milk from the Sarda breed was significantly richer, at p < 0.001, in protein, fat, and lactose, and had a lower urea mean content than Saanen. Throughout the year, fluctuations of mean contents of the milk parameters were similar for the two groups of goats, indicating that, besides genetic intrinsic differences, climate and herbage growth influenced the Sarda as well as the Saanen goats. During the summer, milk from Saanen showed a marked drop in fat and protein contents, with 21% of samples showing a fat-to-protein ratio <1. No significant differences were found for the somatic cell count; however, the Sarda breed showed a higher bacterial count, suggesting improper milk handling and/or storage equipment more frequently encountered in extensive and semi-extensive farm systems.

Effect of seasonality on physico-chemical and microbiological properties of nicastrese milk and artisanal cheese

Nicastrese is an indigenous Italian goat breed reared in the Calabria region under semi-extensive practices. From January to June, the milk yield of 400 multiparous Nicastrese goats was evaluated. In addition, tank milk and ripened cheese samples were subjected to physico-chemical and microbiological analyses with the aim to assess the effect of the seasonality on quality parameters. The volatile organic compounds profile of the ripened Nicastrese cheese samples was evaluated. Results showed that the seasonality had a significant effect on milk fat, lactose, urea, citric acid contents and acidity. Microbiological analysis of tank milk samples revealed variability among the different microbial groups investigated except for Escherichia coli. In addition, faecal coliforms and Listeria spp. were never detected. Regarding 60 days ripened cheese samples, almost all microbial groups showed a significant decrease during the analysed period, with the exception of Enterobacteria. It is interesting to note that Escherichia coli and Listeria spp. were not detected in any cheese sample investigated, confirming the cheese safety. Overall, volatile organic compounds, detected on cheese samples, decreased trough the investigated period and this behavior could be related to the feeding quality and to the milk's goat nutritional components.

Intake, digestibility, ingestive behavior, production, and composition of goat milk supplemented with detoxified castor bean meal added urea as a replacement of soybean meal

This study evaluated the castor bean meal detoxified with calcium hydroxide [Ca(OH)2] added urea replacing soybean meal in the diet of lactating goats from milk production and composition, intake, digestibility, and ingestive behavior. Eight Alpine multiparous goats weighting 44.3 ± 5.3 kg and at approximately 60 days of lactation were confined and randomly distributed in 4 × 4 double Latin squares, with four inclusion levels of detoxified castor meal: control (0), 25, 50, and 75 g/kg dry matter (DM) total. Detoxified castor bean meal replacing soybean meal (P > 0.05) in goats diet did not affect intake and digestibility of DM, crude protein, ether extract, neutral detergent fiber (NDF), total carbohydrates, non-fibrous carbohydrates and total digestible nutrients, times spent for eating, and efficiency ratios of rumination and eating. However, the times spent for rumination and idling showed a quadratic trend decrease (P < 0.01) from the level of 50.0-g/kg DM. The milk production, and the milk production correction showed a quadratic trend increase and feeding efficiency a quadratic decrease (P = 0.03) due inclusion of detoxified castor bean meal replacing soybean meal up to the level of 25.0 g/kg. The fat, protein, lactose, total solids, nonfat solids, and milk urea nitrogen content (g/day) presented a quadratic increase (P < 0.05) by detoxified castor meal inclusion. Detoxified castor bean meal added urea in the Alpine goats diet could be included up to the 25.0 g/kg level replacing soybean meal in the diet because improve milk production and composition and feeding efficiency of goats without negatively effect on intake, digestibility and ingestive behavior.

The Effects of Substituting Dietary Soybean Meal with Maize Grain on Milk Production in Dairy Goats

Simple Summary

Today the environmental sustainability of livestock has become increasingly important. Nitrogen excretion from livestock can lead to air and groundwater pollution, causing acid rain, fine air particulates, and greenhouse gas emissions that lead to climate change, groundwater nitrate poisoning, and surface water eutrophication. Often, livestock are fed diets with a protein content that is much higher than what they require. In this experiment, a herd of dairy goats of the Alpine breed, reared on a farm in the hills near Genoa, Italy, was used to study the impacts of being fed a low- or a high-protein diet. The high-protein diet did not improve milk yield and quality; on the contrary, it lowered the efficiency of dietary-nitrogen utilization, increased feeding cost, and, above all, increased nitrogen excretion and the associated environmental risks. In conclusion, a high-protein diet is not advisable, both economically and environmentally, and a precision feeding approach (i.e., supplying the nutrients required for a given body mass and level of production, and no more) is highly recommended.

Abstract

In view of better environmental sustainability, livestock diets must not exceed protein requirements, as often happens with lactating goats reared in semi-intensive systems. The aim of this experiment was to verify in real-breeding conditions the influence of two diets with different protein contents (% crude protein (CP) on dry matter (DM)): 16.0 (high-protein diet; HP) vs 12.2 (low-protein diet; LP) on milk production in dairy goats. The diets differed only in the replacement—in the LP diet—of 250 g soybean meal with 250 g maize grain meal. Twenty-three Alpine goats were divided into two groups and used in a cross-over feeding trial for 2 months. Animals were weighed at the beginning of each month of the trial, and feed intake and milk yield and composition were recorded weekly. HP and LP did not differ statistically for milk yield and composition (3.32 vs 3.42 kg milk/d, 3.21% vs 3.27% fat, 3.31% vs 3.27% protein for HP and LP, respectively), but the HP diet determined a higher milk urea content (51.2 vs 36.6 mg/dL, p < 0.001) and a worse efficiency of nitrogen utilization (28.0% vs 37.2%). In conclusion, the LP diet resulted in a reduction of urinary nitrogen excretion by 28% and of the feed cost by about 10%.

Differences in the Detailed Milk Mineral Composition of Italian Local and Saanen Goat Breeds

Very little information about local breed goat milk is available, which is relevant for biodiversity preservation and local cheese production. This study aimed to evaluate the effect of breed and week of lactation on milk mineral profile of five Italian local breeds (Garganica, Girgentana, Jonica, Maltese and Mediterranean Red) and a cosmopolitan breed (Saanen). Sixty goats (10 per breed) from an experimental farm were enrolled in the study and sampled every 2 weeks for milk gross composition analysis. In addition, an individual milk sample was collected monthly from 42 goats (seven goats per breed) for mineral determination through inductively coupled plasma optical emission spectrometry. Data were analysed using a mixed linear model with repeated measures, including breed and week of lactation as fixed effects. Week of lactation affected mineral contents, except for B, being lower in early than late lactation, whereas, breed affected only P, Mg and Zn. Mediterranean Red and Jonica breeds' milk was richer in P than Maltese, and in Zn than Maltese, Girgentana and Saanen breeds. For Mg, only Saanen differed from Maltese. Such information might be useful for the valorisation of goat milk produced by autochthonous breeds.

Effects of Sulla forage (Sulla coronarium L.) on the oxidative status and milk polyphenol content in goats

Twelve milking Girgentana goats were allocated into 3 groups and fed 3 diets ad libitum in a 3×3 Latin square design with 3 periods. The diets were Sulla fresh forage ad libitum (SUL), Sulla fresh forage ad libitum and 800g/d of barley meal (SULB), and mixed hay ad libitum and 800g/d of barley meal (HB). Changes were observed in total polyphenol intake, plasma oxidative status, plasma polyphenol content, metabolic status, milk polyphenol content, and total antioxidant capacity. The fresh forage diets (SUL and SULB) increased dry matter, total polyphenol, nontannic polyphenol and tannin intakes, and the milk total protein, casein, milk total polyphenols, and milk free polyphenols compared with the HB diet. The intake of condensed tannins was higher in the SUL than in the HB group, and an intermediate value was recorded for the SULB group. Plasma from the SUL- and SULB-fed goats exhibited greater total antioxidant capacity and greater total polyphenol and free polyphenol levels compared with the plasma from the HB group. Positive correlations between plasma total antioxidant capacity and condensed tannins intake (r=0.43), plasma total polyphenol and total polyphenol intake (r=0.61), and plasma free polyphenol and milk total polyphenols (r=0.38) were observed. The correlation between milk free polyphenols and whey total antioxidant capacity (r=0.42) highlights the role of free polyphenols in the determination of the antioxidant activity of milk. These results indicate that Sulla fresh forage exerts an antioxidant activity due to its secondary compounds that provide additional antioxidant value and that Sulla forage appears to be a promising strategy for improving product quality.

Diet choice by goats as effect of milk production level during late lactation

The diet self-regulation ability of goats during late lactation has been studied with regard to their production level. Two groups of seven Girgentana goats producing 1100 ± 157 g/day (H group) and 613 ± 138 g/day (L group) were housed in individual pens and were given alfalfa pelleted hay (1.5 kg), whole grains of maize (0.5 kg), barley (0.5 kg), faba bean (0.5 kg) and pelleted sunflower cake (0.5 kg) on a daily basis. During a 7-day pre-experimental period, goats received a mixed ration based on the same feeds used during the experimental period (1.5 kg of hay and 0.4 kg of each concentrate). Individual choice of feeds was continuously recorded for 7 days using a 24-h IR video surveillance system equipped with four video cameras. The nutrient intake in both groups was much higher than needed. Goats in the H group ate more (2016.3 v. 1744.3 g dry matter (DM)/day) and selected less hay (26.9% v. 34.6% DM), more high-protein feeds (faba bean and sunflower cake: 14.0% and 15.9% v. 8.8% and 7.9% DM, respectively) and less maize (21.5% v. 25.0% DM), reaching a higher CP concentration in the diet (17.3% v. 15.0% DM) compared with the goats in the L group. During the 24-h trial period, hay was more constantly selected (on average never reaching <20% of the total hourly basis feeding time, apart from the first hour after feed administration) compared with concentrate feeds. This feeding behaviour has probably exercised a 'curative' effect that enabled the goats to continue to take in very high levels of starch and protein, without manifesting any symptom of metabolic disease. Shifting goats from the pre-experimental diet, based on a mixture of the same feeds used during the experimental period, to the free-choice feeding caused more than 20% increase in milk production in both groups. From the results of the intake, we are unable to conclude that the goats can select their diet to meet their requirements, as goats consumed much more than needed. However, when free to choose their diet, the animals improved milk performance, despite the late-lactation stage.

Morning versus afternoon cutting time of Berseem clover (Trifolium alexandrinum L.) affects feed intake, milk yield and composition in Girgentana goats

Twenty lactating Girgentana goats were used to evaluate the effect of morning v. afternoon cutting time of Berseem clover (Trifolium alexandrinum L.) on feed intake, milk yield and milk composition. Goats were randomly divided into two groups of ten animals, receiving 10 kg of fresh Berseem clover cut at 9.00 (AM group) or 16.00 (PM group), respectively; 500 g of concentrate was given individually to goats before offering forage. Feed intake increased (P<0·01) in the PM group (30·5 v. 25·3 g dry matter/kg body weight), associated with the different nutrient content of diets: lower crude protein but higher dry matter, neutral detergent fibre, water soluble carbohydrates (WSC) and total fatty acids in the PM-harvested forage. Milk production, protein and casein content were higher (P<0·05) in the PM group (1415 g/d, 3·25% and 2·42% v. 1277 g/d, 3·15% and 2·33%, respectively), whereas no differences between groups were detected for milk fat, lactose or urea content. Body weight slowly decreased from the start to the end of the experiment, without differences between groups. This study showed an important milk yield responses in Girgentana goats offered afternoon-cut compared with morning-cut Berseem clover, due to a marked increase in WSC in the afternoon-cut forage.