Miguel Mellado

Associations between periparturient disorders and reproductive efficiency in Holstein cows in northern Mexico

Abstract Interrelationships among parity, twinning, retained placenta, abortion, metritis, cystic ovaries, milk fever and postpartum reproductive events were investigated in Holstein cows in northeast Mexico. Data were from 6565 lacations from a large commercial dairy herd. Path analysis was used to model the direct and indirect effects of these variables. The risk of reproductive disorders in cows having a particular periparturient complication was assessed by odds ratio analysis. Milk fever was dropped out of the restricted model, mainly because of the low lactational incidence of this disease (0.5%). The most important implied cause and effect relationships among the periparturient events were twinning causing retained placenta and retained placenta causing metritis (odds ratio = 5.2 and 4.7, respectively; P ∗ 05 ). Excluding abortion, most reproductive disorders and twinning increased the days from parturition to first estrus (from 4.4 to 9.2 days), the days from parturition to conception (from 1.3 to 21.4 days), the services per conception (from 0.28 to 0.5) and the calving interval (from 14.7 to 21.3 days). Only in associations between retained placenta and reproductive parameters were the indirect components an important part of the total causal association.

Factors affecting gestation length in goats and the effect of gestation period on kid survival

Data on 1468 pregnancies and 2356 newborn goat kids of six genetic groups under intensive management were utilized to determine some genetic and non-genetic factors affecting gestation length, and to assess the relationship between gestation length and survival of kids to 25 days of age. The study revealed significant ( P < 0·01) effect of breed of dam, litter weight, breeding season and parity on gestation length. Number of kids born and sex of kids were not a significant source of variation affecting this trait. Granadina goats had the shortest gestation (149·0±0·31 days), whereas Toggenburg (151·7±0·28 days) and Alpine (151·4±0·46 days) had the longest. Litter weight and gestation period were related curvilinearly in summer and linearly in autumn. Gestation of goats bred in summer was 1 day longer ( P < 0·01) than those mated in the autumn. There was a progressive reduction of gestation length as parity increased (151·3±0·24, 150·6±0·17 and 149·9±0·39 days for 1, 2·6 and > 7 kiddings, respectively). The mean survival rate of kids gestated < 148 days and 148–;152 days were 78±2 and 87±1, respectively, and these were significantly lower ( P < 0·05) than the survival rate of kids gestated 152–156 days and > 156 days (94±1 and 95±2). In conclusion, prolonged gestation (152–160 days) in goats was beneficial because it resulted in heavier litters at birth and higher viability of neonatal kids.

Effect of lactation number, year, and season of initiation of lactation on milk yield of cows hormonally induced into lactation and treated with recombinant bovine somatotropin.

Records representing data from 1,500 barren Holstein cows over an 8-yr period from a large commercial dairy farm in northern Mexico were analyzed to determine the effects of lactation number and season and year of initiation of lactation on milk production of cows induced hormonally into lactation and treated with recombinant bovine somatotropin (rbST) throughout lactation. Peak and 305-d milk yields were also assessed as predictors of total milk yield in cows induced into lactation. A significant quadratic relationship was found between 305-d milk yield and number of lactation [7,607±145 and 9,548±181 kg for first- and ≥6-lactation cows, respectively; mean ± standard error of the mean (SEM)] with the highest production occurring in the fifth lactation. Total milk yields of cows with ≤2 lactations were approximately 4,500 kg less than milk yields of adult cows (the overall average ± standard milk yield was 13,544±5,491 kg per lactation and the average lactation length was 454±154 d). Moreover, 305-d milk production was depressed in cows induced into lactation in spring (8,804±153 kg; mean ± SEM) and summer (8,724±163 kg) than in fall (9,079±151 kg) and winter (9,085±143 kg). Partial regression coefficients for 305-d milk yield and peak milk yield indicated an increment of 157 kg of milk per lactation per 1-kg increase in peak milk yield (r(2)=0.69). Neither peak milk yield (r(2)=0.18) nor 305-d milk yield (r(2)=0.29) was accurate for predicting total milk yield per lactation. Year, parity, and season effects had significant influence on milk yield of cows induced into lactation and treated with rbST throughout lactation, and peak milk yield can assist in the prediction of 305-d milk yield but not total milk yield. This study also showed that hormonal induction of lactation in barren high-yielding cows is a reliable, practical, and affordable technique in countries where rbST treatment and prolonged steroid administration of dairy cows are legally permitted.

Short-term intake of β-carotene-supplemented diets enhances ovarian function and progesterone synthesis in goats

The effect of beta-carotene supplementation upon luteal activity, measured as number (CLT) and volume (VLT) of corpus luteum, and P4 synthesis in goats, was evaluated. Goats (n = 22, 34 months) were randomly assigned to one of two experimental groups: (i) beta-carotene [Beta, n = 10; body weight (BW = 44.8 +/- 1.45 kg), body condition score (BCS = 3.25 +/- 0.07)], and (ii) Control (Control, n = 12; BW = 45.30 +/- 1.32 kg, BCS = 3.33 +/- 0.06). Upon oestrus synchronization, the Beta group received 50 mg of beta-carotene per day during 35 days pre- and 17 days post-ovulation. The day 4, 8, 12 and 16 post-ovulation, blood samples were collected for quantification of serum P4 concentrations by radioimmmunoassay, and transrectal ultrasonographic scanning was performed at day 18 for evaluating CLT and VLT. Overall, CLT and VLT mean were 3.10 and 2211.1 mm(3) respectively. The Beta-goats depicted both the largest values for CLT (p = 0.07) and serum P4 levels (p = 0.05), with no differences (p = 0.53) for VLT between treatments. Results suggest a higher efficiency within the cellular-enzymatic groups defining the steroidogenic pathways in the beta-carotene-supplemented goats, generating a larger P4 synthesis. The last is essential for ovulation of healthy oocytes, maintenance of uterine quiescence, nourishment and survival of the embryo around implantation; all of them of paramount significance during the maternal recognition of pregnancy process.

Effect of increasing levels of seven tree species extracts added to a high concentrate diet on in vitro rumen gas output

This study was conducted to investigate the effects of increasing levels of extracts of Byrsonima crassifolia, Celtis pallida, Enterolobium cyclocarpum, Fraxinus excelsior, Ficus trigonata, Phoradendrom brevifolium and Prunus domestica on in vitro gas production (GP) and ruminal fermentation of a high concentrate diet. Plant extracts were prepared at 1 g dry matter (DM)/8 mL of solvent mixture (methanol : ethanol : water, 1:1:8) and added at levels of 0, 0.6, 1.2 and 1.8 mL/g DM of a high concentrate diet. In vitro GP was recorded at 2, 4, 6, 8, 10, 12, 24, 48 and 72 h of incubation. Increasing addition of extracts linearly increased (P < 0.001), the GP24 , GP48 and GP72 (mL/g DM), and linearly decreased (P < 0.001), the discrete GP lag time. Moreover, increasing extract doses linearly increased (P < 0.001) the asymptotic GP and decreased (P < 0.001) the rate of GP. GP6 was not impacted by treatments and GP12 increased linearly (P = 0.01) with increasing addition of extracts. Rumen pH declined linearly (P < 0.05) with increasing doses of extracts added. As no interactions (P > 0.05) occurred between the extracts and doses, it could be conclude that all extracts positively modified rumen fermentation at doses of 1.2 to 1.8 mL extract/g diet DM.

Immunoglobulin G concentration and neonatal survival of goat kids delivered in a pen or on open range

To determine whether kids born on open range (subjected to stress due to management practices) had lower IgG concentrations and a higher mortality risk than kids born in a pen, serum IgG concentrations in 63 one-day-old kids were determined. Median Serum IgG concentrations one day after birth tended to be lower (p = 0.09) in surviving kids born in the open than that of surviving kids delivered in pen (115 vs. 1119 mg dl-1). However, survival risk (71 and 82% for kids born on the open range and pen, respectively; n = 79) were not significantly affected by site of kidding. Median IgG concentration of surviving kids born on a pen was not significantly different (p = 0.13) compared to non-surviving kids (1118 vs. 115 mg dl-1). No differences were detected in either median serum IgG levels or death rates between male and female kids. Kids with IgG concentrations < 800 mg dl-1 showed lower survival risks than those with higher concentrations. We concluded that typical management practices of kids delivered on open range at a goat operation under extensive conditions in northern Mexico tended to reduced colostrally acquired serum immunoglobulin levels, but had no effect directly on mortality.

The Relationship between Linear Type Traits and Fertility Traits in High‐yielding Dairy Goats

Reproductive data collected from 13 medium-size goat farms in central Mexico (582 goats), were used to investigate if linear type traits influenced reproductive performance of high-yielding dairy goats. Data were analysed using multiple stepwise forward logistic regressions. Goats with the higher scores for strength were 1.43 times more likely (p < 0.05) to have larger litters (1.49 vs 1.39) than goats with lower strength. Goats approaching level rump angles were 1.68 times more likely (p < 0.01) to have larger litters, compared with goats with extremely sloped rump angles (1.48 vs 1.37). Goats with rear legs nearly straight (posty) in hock tended (p < 0.08) to presented larger litters than goats with rear legs slightly angled (sickled) in hock (1.49 vs 1.38). Less pronounced rump angle was favourable associated (p < 0.05) with litter weight (4.88 vs 4.53 kg) compared with goats with low pin bones. Goats with poorer udder texture were 1.42 more likely (p < 0.05) to have heavier litters than goats with good udder texture. Goats with faulty mammary system tended (p < 0.07) to have heavier litters than goats with good mammary system. Increasing udder height was associated (p < 0.05) with increasing number of services per conception. Goats with good fore udder attachment and non-refined heads were at reduced risk (p < 0.05) for stillbirths. Goats with stronger median ligament were 65% less likely (p < 0.05) to lose their foetuses than those with looser udder support. Our findings indicate that a greater litter size and litter weight is expected in goats as rump angle becomes less sloped. This study showed that a relationship exists between strength of goats and litter size, and that some traits linked to high milk yield were antagonist to some reproductive traits.

Long-term betacarotene-supplementation enhances serum insulin concentrations without effect on the onset of puberty in the female goat

The effect of betacarotene (BC) supplementation on the onset of puberty and serum insulin levels in goats was evaluated in the study. In June, prepuberal goats (n=17; 3 months old; 7/8 Saanen-Alpine; 26° NL) were randomly assigned to one of two groups: 1/ betacarotene group supplemented daily with 50 mg of BC (n=9; live weight [LW]: 17.3±1.0 kg; body condition score [BCS]: 3.34±0.12) or 2/ control group (CONT; n=8; LW:16.1±1.0 kg; BCS=3.17±0.12). From June to November, an intermittent blood sampling was performed twice per week in both groups to evaluate serum progesterone (P(4)), while monthly samples were intended for insulin (INS) determination. Initial mean LW (16.7±1.0 kg) and BCS (3.31±0.12) were similar (p>0.05) in both groups. Mean serum insulin (1.37 vs. 1.18±0.09 ng/ml), age of puberty (215.7 vs. 226.5±6.6 days) and the percentage of goats reaching puberty (44.4 vs. 25.0±17.0%) did not differ (p>0.05) between BC and CONT group, respectively. However, increase in serum insulin during the second half of the experiment was observed in BC group (p<0.05) which was positively correlated with LW (r=0.95; p<0.05). In addition, as LW (r=-0.89) and serum insulin (r=-0.76) levels increased, the natural photoperiod decreased, revealing negative correlations (p<0.05) between the respective variables. In this study, BC supplementation did not promote precocious puberty and did not affect the percentage of goats reaching activation of the hypothalamic-hypophyseal-gonadal axis during the establishment of puberty. Nonetheless, BC supplementation positively affected the release pattern of insulin suggesting a potential role of BC as pancreas-activating molecule.

Thermoregulation of nutrient-restricted hair ewes subjected to heat stress during late pregnancy.

In summers with severe hot environmental temperatures, thermoregulation is expected to be critical during the last third of gestation of hair ewes, and this effect can be overstated by suboptimal feeding conditions. Twenty-four multiparous hair sheep ewes with approximately 100d of pregnancy were randomly assigned to two treatments to evaluate the effects of nutritional restriction (NR) during late gestation on some serum metabolites, physiological variables, and thyroid hormone concentrations under intense heat load (maximum temperature 42-45°C). Treatments were as follows: (1) control, ewes fed free choice wheat straw plus a concentrate at a rate of 500g/d, and (2) nutritionally-restricted (NR) ewes, which were offered wheat straw only ad libitum. Body weight of NR ewes dropped 5.1kg (P<0.05), while control ewes gained 4.7kg during the study period. Rectal temperature was not affected (P>0.05) by feeding regime either in the morning or afternoon hours. Respiration rate was greater (P<0.05) in control ewes (20 and 40breaths/min higher in the day and night, respectively) on d 130 and 145 of pregnancy compared to NR ewes. Skin temperatures during the morning and afternoon were affected (P<0.05) by feeding regime at d 130 and 145 of pregnancy. In the morning, NR ewes presented greater (P<0.05) head and rump temperature at day 145 of gestation, and lower (P<0.05) udder temperatures at d 130 and 145 than control ewes. In the afternoon, skin temperatures of NR ewes were higher (P<0.05) in head and right flank on d 130 and 145 of pregnancy, and in udder at day 145 compared to control ewes. Serum glucose was higher (P<0.05) in NR ewes than control animals at day 145 of pregnancy. Serum cholesterol, triglyceride and thyroid hormones were not affected by nutritional restriction. Overall, it was found that nutritionally restricted ewes were less affected by intense heat loads than well-fed ewes, apparently due to the lower metabolic heat produced by this underfed animals. Also, it was apparent that the lower respiration rate of NR ewes was compensated by a greater body surface temperature.

Relationship between litter birthweight and litter size in five goat genotypes

Theaimofthepresentstudywastouseanon-linearregressionapproachtoinvestigatetherelationshipbetween litter birthweight and litter size of five breeds of goat under intensive conditions in a hot arid environment. Litter-size and litter-weight data on 20117 kids from 13685 litters representing five breeds, namely Saanen, Toggenburg, French Alpine, Anglo-NubianandGranadina,werecomparedtoevaluatethisrelationship.Regardlessofbreed,birthweightforkidsbornas twins, triplets and quadruplets was, on average, 92%, 87% and 83%, respectively, of that of singleton kids; litter size accountedfor81%ofthevariationinlitterweight.Thecoefficientofthepowerregressiondiffered(P <0.01)amongbreeds, withsimilarslopesforFrenchAlpine,ToggenburgandSaanengoatsandasmallerlitter-weightincreaseforeveryadditional fetusinAnglo-NubianandGranadinagoatsthaninotherbreedsofgoat.Theseresultssupportthehypothesisthat,regardless ofparity,litterweightindairyandGranadinagoatsincreasesatareducedratewithincreasesinlittersize,althoughtherateof change with the increasing number of fetuses was moderate, as indicated by a power regression of the form y=ax b between these variables across age categories and breeds of goat.