Array of Hall Effect sensors for linear positioning of a magnet independently of its strength variation. a case study: monitoring milk yield during milking in goats.

In this study we propose an electronic system for linear positioning of a magnet independent of its modulus, which could vary because of aging, different fabrication process, etc. The system comprises a linear array of 24 Hall Effect sensors of proportional response. The data from all sensors are subject to a pretreatment (normalization) by row (position) making them independent on the temporary variation of its magnetic field strength. We analyze the particular case of the individual flow in milking of goats. The multiple regression analysis allowed us to calibrate the electronic system with a percentage of explanation R² = 99.96%. In our case, the uncertainty in the linear position of the magnet is 0.51 mm that represents 0.019 L of goat milk. The test in farm compared the results obtained by direct reading of the volume with those obtained by the proposed electronic calibrated system, achieving a percentage of explanation of 99.05%.

Effect of mid-line or low-line milking systems on milking characteristics in goats.

Two experiments were carried out to compare mechanical milking in mid-level (ML) and low-level (LL) milkline in goats. The first trial used 40 intramammary infection (IMI)-free goats that had been milked in ML during a pre-experimental period of 4±1 weeks post partum. These animals were divided into two groups (n=20), randomly assigning each group to ML or LL milking for a 17-week experimental period. During this period, several strategies were applied to increase teat exposure to pathogens in both experimental groups. The IMI rate was the same in both experimental groups (30% of goats), although the majority of new infections appeared earlier in ML (weeks 1-5) than in LL (weeks 7-16). Teat-end vacuum range (maximum minus minimum vacuum) was higher in ML than in LL, but no significant differences were found in the remaining variables [milk production and composition, somatic cell count (SCC), frequency of liner slips+teatcups fall off]. In the second experiment, in a crossover design (54 goats in fourth month of lactation; 2 treatments, ML and LL, in 2 experimental periods each lasting 1 week) it was observed that both the milk fractioning (reduced machine milk and increased machine stripping) and average machine milk flow worsened slightly in ML milking; in contrast, no differences were observed in total milking time or teat thickness changes after milking. It was concluded that the differences found between ML and LL are not sufficiently important to discourage breeders from using ML in goat milking.

Terminal Crossbreeding of Murciano-Granadina Goats with Boer Bucks: Characteristics of the Carcass and the Meat.

After verifying productive improvements from the crossbreeding (MB) of Boer males with females of the Murciano-Granadina (MG) breed, the aim of this work was to determine its consequences on the carcass and meat characteristics of suckling kids (9 kg of weight at slaughter) of both sexes. A total of 94 kids (25 purebred MG males, 19 purebred MG females, 25 crossed MB males and 25 crossed MB females) were used. It was found that MB kids reached slaughter weight at a younger age (44 ± 1 vs. 63 ± 1 days, p < 0.001). For carcass yield, the interaction genotype x sex was observed, where MB females presented a higher value (51.71 ± 0.34%) than the rest of the animals (MB males 50.53 ± 0.34, p < 0.05; MG males 50.60 ± 0.34, p < 0.05; MG females 49.62 ± 0.39, p < 0.001). MB kids had greater leg compactness, (36.28 ± 0.27 vs. 34.71 ± 0.29 g/cm, p < 0.001), slightly improved expensive carcass cuts (75.93 ± 0.31 vs. 74.77 ± 0.34%, p = 0.014) and higher muscle/bone (2.93 ± 0.03 vs. 2.76 ± 0.03, p < 0.001) and meat/bone ratios (3.56 ± 0.04 vs. 3.36 ± 0.04, p < 0.001) than MG kids. They also showed a somewhat more intense red colour (8.57 ± 0.25 vs. 7.74 ± 0.27, p = 0.027), higher colour saturation (9.06 ± 0.24 vs. 8.20 ± 0.26, p = 0.016) and less meat firmness (1.95 ± 0.08 vs. 2.23 ± 0.081 kg/cm2, p = 0.021). On the other hand, males had a slightly improved proportion of expensive cuts (75.98 ± 0.31 vs. 74.73 ± 0.34, p = 0.008), but their carcass contained a higher proportion of bone (22.16 ± 0.21 vs. 21.17 ± 0.17%; p < 0.001), a lower proportion of intermuscular fat (9.54 ± 0.24 vs. 10.93 ± 0.24, p < 0.001), a higher muscle/fat ratio (5.01 ± 0.10 vs. 4.41 ± 0.10, p < 0.001) and lower muscle/bone (2.80 ± 0.03 vs. 2.89 ± 0.03%, p = 0.016) and meat/bone ratios (3.36 ± 0.04 vs. 3.56 ± 0.04%, p < 0.001) than females. There were no sensory differences in any case. It is concluded that this crossbreeding strategy also improves the carcass and meat characteristics, making it a valid alternative to improve the productive results of MG dairy goat herds.

Terminal Crossbreeding of Murciano-Granadina Goats to Boer Bucks: Effects on Reproductive Performance of Goats and Growth of Kids in Artificial Rearing.

The aim of this work was to improve the growth characteristics of Murciano-Granadina (MG) kids through terminal crossbreeding of MG goats to Boer bucks. Four experiments were carried out, using a total of 354 MG goats, half of which were mated with MG bucks (n = 12) and the other half with Boer bucks (n = 12). The kids were raised in artificial rearing until slaughter weight (9 kg). The birth weight and average daily gain were recorded in crossed kids (n = 197 and 145, respectively) and purebred kids (n = 257 and 169, respectively). Crossed kids presented significant differences (p < 0.001) compared to MG purebred kids in birth weight (+ 24%), mortality in artificial rearing (-37%), average daily gain (+32%) and milk powder conversion rate (-16%). However, the reproductive performance rates of MG goats mated with Boer bucks were slightly worse (pregnancy rate: 78.5% vs. 86.6%, p < 0.05; kidding rate: 62.0% vs. 75.7%; p < 0.01; prolificacy: 1.9 vs. 2.1 kids/parturition), especially when the matings took place in non-breeding season (experiments conducted at latitude 38-39° N). It is concluded that the terminal crossbreeding of MG goats to Boer bucks (those not used to produce replacement kids) could be an interesting option for ethical goat production.

Kid Growth Comparison between Murciano-Granadina and Crossbred Murciano-Granadina×Boer in a Mixed Rearing System.

In dairy goats, the low average daily gain and the high conversion ratio for milk and concentrate of the kids mean that their sale price does not offset the costs generated. The hypothesis proposes that a crossbreeding of the Murciano-Granadina breed (MG) with the Boer breed (MG×Boer) will improve the profitability of the kids sold. Thus, the effect of two different groups of kids (purebred MG and crossbred MG×Boer) on birth weight (BW), mortality, average daily gain (ADG), the time for minimum slaughter weight (7 kg) and its variation factors were studied. MG×Boer kids had a 27% greater BW than purebred MG kids (2885 ± 84 g and 2275 ± 74 g, respectively), similar ADG (156 ± 6 g and 142 ± 6 g, respectively) and mortality (18% and 20%, respectively), and reached minimum slaughter weight a week sooner. ADG was less and less as the lactation period progressed due to a lower milk consumption and milk energy value, which highlights the importance of providing a concentrate that will compensate for this reduced energy content. In conclusion, the results show that MG×Boer crossbred kids reached the minimum slaughter weight a week earlier than purebred MG kids, and highlighted the improvement of farm profitability through the increase of milk sold and the need to provide a concentrate feed to enhance the growth of the kids.

Effect of stress on somatic cell count and milk yield and composition in goats.

There is little information about the effect of the stress on Somatic Cell Count (SCC) and milk yield and composition in goats. A total of 40 goats in their 4th month of lactation were assigned to two groups: stress (STR) and untreated (CON). Goats of STR were exposed to acute stress (visual and auditory stimulus from a barking dog for 20 min on day 0). After the stress, average values of plasma cortisol were higher in STR than CON (P < 0.001); likewise, in STR group cortisol was lower in parity 1 + 2 goats than parity ≥3 goats (P < 0.05). Stress caused a considerable increase in SCC in parity ≥3 goats (P < 0.05), but not in parity 1 + 2 goats. On average, this increase of SCC was 6-fold compared to values prior to the stress, and it was observed in both healthy and infected mammary glands. This increase was transient, as SCC returned to normal values after 1 to 3 days. On day 1, stressed goats of parity ≥3 produced 11% less milk compared with day 0 and, regarding milk composition, only lactose showed a significant drop. Stressed parity 1 + 2 goats showed no changes in SCC and milk yield and composition. We conclude that, in goats, stress is a non-infectious factor that can interfere in the use of SCC as an indirect method of intramammary infection (IMI) detection or, in bulk tank milk, as a commercial milk quality parameter.

Accuracy of BRT and Delvotest microbial inhibition tests as affected by composition of ewe's milk.

The presence of drug residues in ewe's milk samples can be determined by microbial assays. The main limitation of these tests is the large number of false-positive results associated with them. False-positive results can be explained by the interaction of certain substances naturally existing in ewe's milk with the growth of the microorganism used in the test. In this study, milk chemical composition (fat, protein, lactose, total solids), somatic cell counts (SCCs), free fatty acid concentrations, and lactoperoxidase system components were determined in order to investigate their influence on the rate of false-positive results for the BRT and Delvotest microbiological inhibitor tests. Milk samples were obtained after morning milking of Manchega ewes at 15, 30, 45, 60, 75, 90, 105, 120, and 135 days after parturition. The animals did not receive any kind of treatment or medicated feed throughout the experiment. The false-positive rates for BRT and Delvotest were 3.75 and 2.4%, respectively. When the logistic regression model was applied, the percentages of total solids for positive samples were significantly different from those for negative samples (16.90 versus 18.42% for BRT, 16.05 versus 18.45% for Delvotest), while the SCC logarithmic transformation was significantly higher for the positive samples than for the negative samples (5.38 versus 5.11 log units for BRT, 5.32 versus 5.11 log units for Delvotest). Moreover, Delvotest-positive samples exhibited thiocyanate concentrations higher than those of Delvotest-negative samples (8.18 mg/liter versus 6.85 mg/liter). Further analyses are needed to confirm the possible presence of antimicrobial residues in this particular type of milk sample.

Quantitative estimation of the impact of caprine arthritis encephalitis virus infection on milk production by dairy goats.

This retrospective study investigated milk production losses associated with serological evidence (serostatus) of caprine arthritis encephalitis virus (CAEV) infection over one lactation in 4543 Murciano-Granadina goats from 22 herds in Spain. The seroprevalence of infection was 18%, ranging from 0% to 2% in 11 herds, 7% to 60% in 10 herds and was 100% in one herd. Seropositive does had significantly shorter lactations, produced less milk and milk fat, lactose and dry extract and had higher somatic cell counts than their seronegative counterparts, although differences in milk production between seropositive and seronegative animals were noted between herds. Mixed regression models confirmed the association between CAEV seropositivity and reduced milk production. The adjusted, least squares mean (LSM) test-day milk yield was 10% less in seropositive compared to seronegative does and this difference varied according to lactation number. In contrast, differences in the LSM of milk fat, lactose and dry extract percentages between seropositive and seronegative goats were only between 0.1% and 0.2% and did not increase with lactation number. The findings of this study provide strong evidence that CAEV-infection can be a major cause of reduction in milk yield in goats and its control should be considered as part of dairy goat herd health schemes.