Effect of heat stress during the dry period on milk yield and reproductive performance of Holstein cows.

This study aimed to determine the influence of heat stress during the dry period on milk yield and reproductive performance of Holstein cows in a hot environment. Breeding and milk production records of cows, as well as meteorological data between 2017 and 2020 from a commercial dairy herd (n = 12,102 lactations), were used to determine the relationship between climatic conditions during the dry period (average of the temperature-humidity index (THI) at the beginning, middle, and end of the dry period) and reproductive efficiency and milk yield traits. THI was divided into < 70 (no heat stress), 70-80 (moderate heat stress), and > 80 (severe heat stress). First-service pregnancy rate of cows decreased (P < 0.01) with increasing hyperthermia during the dry period (9.5, 7.3, and 3.4% for THI < 70, 70-80, and > 80, respectively). All-service pregnancy rate was highest (P < 0.01) for cows not undergoing heat stress during the dry period (60.2%) and lowest (42.6%) for cows with severe heat stress during the dry period. Cows not experiencing heat stress during the dry period required a mean ± SD of 5.6 ± 3.8 services per pregnancy compared with 6.5 ± 3.6 (P < 0.01) for cows subjected to THI > 80 during the dry period. Cows not suffering heat stress during the dry period produced more (P < 0.01) 305-day milk (10,926 ± 1206 kg) than cows subjected to moderate (10,799 ± 1254 kg) or severe (10,691 ± 1297 kg) heat stress during the dry period. Total milk yield did not differ (P > 0.10) between cows not undergoing heat stress (13,337 ± 3346 kg) and cows subjected to severe heat stress during the dry period (13,911 ± 4018 kg). It was concluded that environmental management of dry cows during hot months is warranted to maximize reproductive performance and milk yield in the following lactation.

Cooling Holstein cows for 60 days prepartum in summer: effects on prepartum physiology, postpartum productivity, and calf growth.

Heat stress (HS) during the dry period of dairy cows in hot and dry conditions compromises the physiological status and mammary gland development of dairy cows, thereby negatively affecting milk component yield in the subsequent lactation. Our objective was to evaluate the effects of cooling Holstein cows under moderate or higher HS conditions (i.e., ambient temperature higher than 30 °C, with a temperature-humidity index of 78.2 units) during the dry period on prepartum physiological status, postpartum productivity, and calf growth. Twenty-four multiparous Holstein cows were divided into two groups: one with a cooling system based on spray and fans under a pen shade (CL, n = 12) and the other not-cooled (NC, n = 12). The cooling system operated 10 h/d (09:00-19:00 h) for 60 d prepartum. During the morning, rectal temperature and respiration frequency were lower in CL cows, but not in the afternoon, which was attributed to higher (P < 0.01) dry matter intake by CL cows. Total serum protein was higher (P < 0.01) in CL cows, but hemoglobin was higher in NC cows (P < 0.01), with no differences in other electrolytes, hormones, hematological components, and metabolites. Milk fat and fat and fat-protein corrected milk were higher (P < 0.05) in CL cows. Female and birth weight trended (P = 0.08) to be higher in CL cows. Cooling cows during the dry period had a limited effect on physiology prepartum but increased postpartum productivity of Holstein cows under hot and dry conditions.

Fertility of Holstein cows and heifers submitted to timed artificial insemination and receiving one or two doses (12 h apart) of semen.

The objective of this retrospective study was to assess the effect of receiving a single (n = 50,285) or double (n = 4392) artificial insemination (AI), 12 h apart, within a timed artificial insemination protocol on pregnancy per AI (P/AI) in nulliparous heifers (inseminated with either sex-sorted or conventional semen) and pluriparous Holstein cows in a commercial dairy herd. Also, this study aimed to investigate the relationship between temperature-humidity index (THI) and time of the first AI and fertility. Fertility of cows receiving two AI with normothermia (THI <68) was higher (p < .05) than cows receiving a single AI (42.9% vs. 36.4%). P/AI of cows receiving two AI with severe heat stress (THI >85) was higher (p < .05) than cows receiving a single AI (21.0% vs. 12.6%). Regardless of heat stress conditions, applying the first AI in the morning increased (p < .05) P/AI in cows with double AI than in cows whose first AI occurred in the afternoon (38.4 vs. 33.3%). With moderate heat stress, and sexed-sorted semen, P/AI to timed AI was higher (65.0 vs. 51.9%; p < .05) in heifers receiving double AI than those serviced once. It was concluded that double AI, 12 h apart, enhanced fertility at timed AI than herd mates with a single AI, particularly with heat stress at breeding.

Ovarian activity and reproductive responses of lactating Angus cows due to a mineral supplementation throughout a timed AI protocol.

Two experiments were conducted to evaluate the effect of intramuscular administration of minerals during a TAI program on the reproductive responses of lactating Angus cows. All cows (n=353) were subjected to a 9-day TAI program based on CIDR insertion plus injections of estradiol, cloprostenol, and eCG, and then TAI 48 h later. In experiment 1, two groups were randomly created, one control with a placebo injection (CON, n=109), and the second received 10 mL of Fosfosan® (MIN, n=172) on day 0 of the synchronization. Conception rate (66.9 vs. 55%) and estrus percentage (55.8 vs. 44%) were higher (P≤0.05) in MIN than in CON cows. Given these results, a second experiment was conducted randomly assigning the cows to two treatments (n=36 each): a single injection of 10 mL of Fosfosan® (MIN-O) on day 0 or two injections of 10 mL of Fosfosan® (MIN-T) on synchronization days 0 and 7. Four cows of each treatment were randomly selected to be scanned with transrectal ultrasound before and during the synchronization protocol to assess ovarian structures and cyclicity, and at day 39 post-TAI for pregnancy diagnosis. Also, blood samples were obtained for the determination of serum minerals and progesterone (P4) concentrations. The number of mineral injections did not affect conception rate (P≥0.1229) conception rate, serum mineral and P4 concentrations, number, and size of emerging follicles, or follicle size according to 1 to 4 classifications. The MIN-T promoted (P<0.05) earlier follicular wave emergence than MIN-O. However, MIN-O cows had a dominant follicle of 15.12 mm, which is more significant (P<0.05) than that in MIN-T cows (13.5 mm). In conclusion, providing a single mineral injection of Fosfosan® at the start of a TAI program is an excellent reproductive strategy in lactating Angus cows to improve the dominant follicle growth, estrus response, and conception rate.

Prediction of rectal temperature in Holstein heifers using infrared thermography, respiration frequency, and climatic variables.

The objective of this study was to develop an equation to predict rectal temperature (RT) using body surface temperatures (BSTs), physiological and climatic variables in pubertal Holstein heifers in an arid region. Two hundred Holstein heifers were used from July to September during two consecutive summers (2019 and 2020). Respiratory frequency (RF) was used as a physiological variable and ambient temperature, relative humidity and temperature-humidity index as climatic variables. For the body surface temperatures, infrared thermography was used considering the following anatomical regions: shoulder, belly, rump, leg, neck, head, forehead, nose, loin, leg, vulva, eye, flank, and lateral area (right side). Initially, a Pearson correlation analysis examined the relationship among variables, and then multiple linear regression analysis was used to develop the prediction equation. Physiological parameters RT and RF were highly correlated with each other (r = 0.73; P˂0.0001), while all BST presented from low to moderate correlations with RT and RF. BST forehead temperature (FH) showed the highest (r = 0.58) correlation with RT. The equation RT = 35.55 + 0.033 (RF) + 0.030 (FH) + ei is considered the best regression equation model to predict RT in Holstein heifers in arid zones. This decision was made on the indicators R2 = 60%, RMSE = 0.25, and AIC = 0.25, which were considered adequate variability indicators.

Effect of breed and management practices on reproductive and milking performance of rangeland goats.

The traditional goat production systems on arid and semi-arid rangelands of northern Mexico are characterized by minimum external inputs; therefore, little is known about goat response to technological improvements. This observational study aimed to ascertain the effect of using improved goat production technologies and breed on milk yield and reproductive performance of goats on rangeland. The study was conducted from January 2017 to June 2018. Thirty-seven goat herds comprising 6393 animals were used. Goats supplemented with 250 g of concentrate (S-goats; 14% crude protein) 30 days before breeding produced significantly more daily milk yield (218 ± 61 vs. 200 ± 60 g) than the unsupplemented (UNS-goats) goats. Milk production per lactation was 12 percentage points greater in goats with access to plain salt throughout the year than those without salt access. The absence of deworming significantly depressed daily milk yield (189 ± 55 vs. 221 ± 61 for non-treated and treated goats). In 5 months, the lowest total milk yield was for Boer goats (26.9 ± 8.3 kg) and the highest for Nubian goats (36.1 ± 9.2 kg). The kidding rate was significantly higher in the S-goats than in the UNS-goats group (66.9 vs. 62.8%). Salt-supplemented goats had a significantly greater kidding rate than goats not receiving salt (68.5 vs. 61.2%). The lowest kidding rate was for Saanen goats and the highest for Nubian goats (66.2%). These findings indicate that milk yield and reproductive performance were primarily influenced by supplementing grazing goats with concentrates and salt in this semi-arid rangeland.

n-6 Polyunsaturated fatty acids in the feeding of late gestation hair ewes: the effects on thermoregulation, growth, and metabolism of heat-stressed growing lambs.

The objective was to determine the effects of feeding soybean oil (SBO), an ingredient rich in n-6 polyunsaturated fatty acids (PUFA), to late gestation hair ewes on physiological responses, feedlot performance, and serum metabolite and electrolyte concentrations of their growing ewe lambs under outdoor heat stress conditions. Twenty-four Dorper × Pelibuey ewe lambs weaned (body weight = 21.5 ± 0.2 kg, age= 2 months, and multiple birth) born from ewes fed 0, 30, or 60 mg of SBO/kg dry matter (DM) during late gestation were selected (n = 8/treatment) to conduct a 30-day feeding trial during the summer season of a desert region (temperature = 34 °C and temperature-humidity index = 35 units). While rectal temperature was unaffected in any daytime, respiratory rate in the afternoon quadratically increased (P = 0.05) as the SBO levels increased from 0 to 60 mg/kg DM in the maternal diet. Final weight, average daily gain, and feed efficiency linearly increased (P = 0.04) with increasing levels of SBO. Body surface temperatures and serum concentration of glucose, cholesterol, triglyceride, total protein, urea, sodium, potassium, and chlorine did not vary by the SBO inclusion in the maternal diet. In conclusion, feeding late gestation hair ewes with source rich in n-6 PUFA appears to be an effective maternal nutritional strategy to improve post-weaning growth without compromising the thermoregulatory ability of their growing offspring under a heat stress environment.

Growth performance and changes in physiological, metabolic and hematological parameters due to outdoor heat stress in hair breed male lambs finished in feedlot.

The aim of this study was to evaluate the effect of seasonal heat stress (HS) on productive performance, physiological responses, metabolism, and hematological profile of hair breed male lambs finished in feedlot. Twenty Dorper × Katahdin male lambs (body weight = 34.6 ± 1.4 kg and age = 4.5 months) were housed in individual pens and exposed to environmental conditions of summer HS (n = 10, temperature = 28.3 ± 4.0 °C and THI = 77.2 ± 5.4 units) or winter thermoneutrality (n = 10, temperature = 19.2 ± 2.6 °C and THI = 64.0 ± 3.0 units). Each season, a 30-day feeding test was conducted to measure study variables. Compared to thermoneutral lambs, heat-stressed lambs had lower (P < 0.01) growth rate and feed efficiency without changing dry matter intake. Heat-stressed lambs presented higher (P < 0.01) rectal temperature and respiratory rate through the daytime than termoneutral lambs. On most sampling days, summer HS caused lower (P < 0.01) serum concentrations of glucose, cholesterol, total protein, urea, potassium, and thyroid hormones, but higher (P < 0.01) serum triglyceride and chlorine values. Overall serum concentrations of cortisol and insulin were unaffected by summer HS. The blood of heat-stressed lambs showed lower (P ≤ 0.03) erythrocyte and platelet counts, hemoglobin, and hematocrit, but higher (P ≤ 0.03) erythrocyte size and leucocyte count than the blood of thermoneutral lambs. In conclusion, hair breed male lambs in response to chronic conditions of summer HS had slow growth but avoided hyperthermia due to the activation of physiological, metabolic and endocrine adjustments.

Impacts on two dairy breeds of adding a third (night) cooling event under extreme ambient heat.

Impacts of an additional cooling event during the night on physiological and productive parameters of two breeds (B) of dairy cows under severe heat stress conditions were determined. Fifteen Holstein (H) and 15 Jersey x Holstein (JxH) cows were assigned to one of the two cooling strategies (CS), where the difference was an added 1 h cooling event during the night (i.e., 3X and 4X cooling events) with the 4X group having the added night cooling event. Maximum and minimum average temperature/humidity indices during the study were 86 and 77 units, respectively. There were no CS x B interactions for any response variable. Body condition score (BCS) was similar between CS, but H cows had higher (P<0.05) condition than JxH. There were no differences in rectal temperature due to CS or B. Respiration rate between breeds and cooling strategies were similar throughout the day. However body surface temperatures of head, thurl, right flank, and udder were higher (P<0.05) in 3X versus 4X cows, and H cows maintained a higher (P < 0.05) temperature in thurl and right flank than JxH during PM hours. Metabolites and hormone concentrations were not affected by CS, but H cows had lower (P < 0.05) triiodothyronine and higher (P < 0.05) thyroxine, than JxH. The 4X cows had higher (P<0.05) milk yield and milk energy output than 3X cows. While H cows produced more milk than JxH, the latter had higher (P < 0.05) milk component levels. In general, JxH cows were judged to have to demonstrate a more desirable physiological response and milk composition outcome than H cows. An additional night cooling event was judged to result in more desirable physiological and productive responses than in cows without this extra night cooling event under the extremely hot and dry environmental conditions during the study.

Risk factors associated with testing positive for tuberculosis in high-yielding Holstein cows.

Tuberculosis remains a significant infectious disease of farm animals and humans worldwide. The objective of this study was to assess various risk factors associated with testing positive for bovine tuberculosis (bTB) in high-yielding Holstein cows in an intensive dry-lot dairy operation. In a retrospective observational study, 9312 records from Holstein cows from a large dairy herd in northern Mexico were used. The incidence rate of lactating cows reactor to bTB was 7.3 cases/100 cow years (95% CI = 6.7-7.9%). Multiple logistic regression models indicated that cows with total milk yield during the first lactation >10,200 kg were 1.3 times (95% confidence intervals (CI) for odds ratio (OR) = 1.2-1.6) more likely to be detected as bTB reactors than cows with total milk yield <10,200 kg (8.2 vs. 6.4%; P < 0.01). The risk of being reactor to bTB increased with x̅ total milk yield/lactation >11,500 kg (OR=2.7, 95% CI = 2.3-3.3; 10.4 vs. 4.2%) compared with cows with x̅ total milk yield/lactation <11,500 kg. Cows with >10,200 kg 305-day milk yield in the last lactation was associated (P < 0.01) with 1.3 times higher odds (95% CI for OR = 1.1-1.5) of being classed as reactors than cows with <10,200 kg. Cows with peak milk yield >48 kg were 1.9 times (95% CI for OR = 1.6-2.2) more likely to be reactor to bTB than cows with peak milk yield <48 kg (9.2 vs. 5.1%; P < 0.01). Cows with either puerperal metritis (OR = 0.07, 95% CI = 0.5-0.9) or carrying twins (OR = 0.05, 95% CI = 0.01-0.19) had a protective role for being reactor to bTB. This study showed that increased milk production was associated with a higher risk of becoming positive to tuberculin skin test in high-yielding Holstein cows.

Growth performance and mammary gland development of Holstein calves fed milk with 15% solids and treated with growth promoters.

The objective of this study was to evaluate growth performance, and mammary gland parenchyma (PAR) development in Holstein female calves fed whole milk combined with milk replacer for 15% total solids (15TS) or only milk (11% TS; 11TS). The effects of zilpaterol hydrochloride (ZH) and an estrogenic implant (EI) on growth performance, serum metabolites, and PAR development in post-weaning calves (63-90 days of age) fed 15TS or 11TS were also investigated. In the first phase, 78 calves were randomly divided into two groups (n = 39/group), 15TS, or 11TS (5 to 8 L/day; starter ad libitum). After weaning, calves were randomly assigned to four treatments, no EI, EI, ZH, and ZH-EI. In phase 1, 15TS calves had greater (P < 0.01) average body weight at weaning than 11TS calves (82.0 ± 5.8 vs. 74.1 ± 5.7 kg). Pre-weaning average daily gain (718 ± 67 vs. 576 ± 64 g/day) was higher (P < 0.01) for 15TS calves than 11TS calves. Feed/gain (1.5 ± 0.3 vs. 1.8 ± 0.3 kg of DMI/kg of gain) was lower (P < 0.01) for 15TS calves than 11TS calves. PAR area (8.8 ± 3.3 vs. 5.0 ± 1.6 cm2) was greater (P < 0.01) for 15TS calves than 11TS calves. No differences (P > 0.10) in average daily gain (986 ± 79 g/day across treatments) were observed in calves receiving ZH, EI, or ZH-EI fed 15TS or 11TS diets previously. However, the PAR area of 15TS calves administered ZH-EI was 2.2 times greater (P < 0.01) than 11TS calves with no ZH and CI. This study demonstrated the benefits of supplying milk with 15% TS for enhancing overall animal growth and PAR development. Further use of ZH and EI during the post-weaning period did improve mammary PAR growth.

Short communication: reproductive response to concentrate supplementation of mixed-breed goats on rangeland.

The effect of concentrate supplementation to crossbred goats on rangeland during the dry period on their reproductive performance was investigated. Goats were assigned into two groups: a concentrate supplemented (S; n = 91) group and an unsupplemented (UNS; n = 118) group. S goats received 350 g/day of concentrate per head, 30 days prior to breeding (flushing in winter) and 30 days during the last trimester of pregnancy. UNS goats presented a lower (P < 0.01) liveweight at the onset of the breeding period than did the S group (38.2 ± 3.7 vs. 44.4 ± 3.6 kg). Average daily gains during pregnancy were higher (P < 0.01) in the S group than UNS goats (15.5 ± 1.2 vs. - 0.5 ± 5.1 g/d). S goats had a higher (P < 0.01) kidding rate (87.1%) than the UNS goats (54.7%). Litter size for UNS and S goats was 1.39 and 2.00, respectively (P < 0.01). Serum triiodothyronine, tetraiodothyronine, and cortisol concentration at the end of the flushing period were not affected by concentrate supplementation. Serum glucose (88.7 ± 3.8 vs. 95.7 ± 5.3 mg/dL), total protein (6.9 ± 1.1 vs. 8.2 ± 1.2 mg/dL), and blood urea nitrogen (17.1 vs. 21.0 ± 4.3 mg/dL) concentrations were lower for UNS goats as compared with S goats. In conclusion, concentrate supplementation in crossbred goats on rangeland markedly improved body mass changes during gestation and the reproductive performance, which implies that malnutrition is a major barrier affecting fertility of goats and liveweight of kids in this rangeland.

Characterization of small-scale dairy farms and its relation to water use efficiency in the Mexicali Valley, Mexico.

A survey was completed to determine water use by small-scale dairy farms in Mexicali Valley of Mexico and to associate it with dairy production parameters. Mexicali Valley surrounds the capital city of the state Baja California, Mexicali. Sixty-one smallholders were interviewed in person in this rural area of northwestern Mexico. On average, small dairy holders had more than 20 years of experience and were ~ 55 years of age; people working on their farms are especially relatives. A low percentage was literate (20%), and they belong to a local dairy association. Milk yield/cow/year does not reach 4000 kg of milk and 75% of producers do not follow a defined management program for their cattle. Hand-milking is still practiced by 27% of the producers, and there is a general lack of infrastructure to maintain milk in a refrigerated state so that there is a very high risk of zoonotic diseases. Water use efficiency (WUE) was linearly correlated (P < 0.05) with total irrigated area, but not with animal production parameters. Regression equations constructed to explain WUE exhibited low adjustment, and WUE was not associated (P > 0.05) with milk yield. Small dairy producers in Mexicali Valley are in a generally poor situation with low water use practices; however, required more government support to increase their benefits from this livestock activity.

Milk yield and hair coat characteristics of Holstein cows in a hot environment.

This study was conducted to evaluate the effects of hair coat characteristics on thermophysiological variables and body surface temperatures (BST), measured with infrared thermography, as well as milk yield of Holstein cows in a hot environment. Physiological and milk yield variables were assessed using 103 pluriparous Holstein cows. Also, hair angle (HA), density of hair coat (D), diameter of hair (HD), hair length (HL), weight of hair coat (Wt), and coat thickness (CT) were recorded. Biplot analysis (principal components analysis) revealed that HL was closely associated with Wt, CT, and HD and all these variables had a positive association with rectal temperature. Both CT and HL were found to be negatively associated with shoulder and neck temperature; tympanic temperature showed no association with BTS. Cows with short hair coat (length < 17 mm) did not produce more milk in 305 days than cows with longer hair coat (9673 ± 1604 vs. 9277 ± 817; P = 0.12). On the other hand, milk fat percentage at the middle of lactation was higher (P < 0.01) in cows with longer hair relative to cows with coat hair < 17 mm (3.71 vs. 3.35%, respectively). In conclusion, physical characteristics of the coat of Holstein cows were not associated with the 305-day milk yield but cows with longer hair produced a greater milk fat percentage at the middle of lactation compared to cows with short hair.

Risk factors associated with reproductive performance in small-scale dairy farms in Mexico.

Several studies suggest that reproductive performance in small-scale dairy farms is low reducing the farms' profitability. Therefore, identifying risk factors associated with low reproductive performance is a key step to implement an improved reproductive management program. Accordingly, the aim of the present study was to identify the main risk factors affecting the reproductive performance of cows in small-scale dairy farms. Ninety-six dairy farms were incorporated into this study, and data from 1263 lactations were collected with different events as potential risk factors. Logistic regression models were used to assess the association (odds ratio, OR) and impact (population attributable fraction, PAF) between the potential risk factors and the reproductive variables. The main risk factors associated with assisted calving were male calf and primiparous cows (OR = 1.7, PAF = 0.315 and OR = 1.5, PAF = 0.131, respectively), while for retained fetal membranes (RFM) were assisted calving and abortion (OR = 4.5, PAF = 0.440 and OR = 8.1, PAF = 0.239, respectively). The main risk factors for days to first service over 70 days in milk were low body condition score at calving (BCS ≤ 2.5) and primiparous cows (OR = 2.2, PAF = 0.285 and OR = 1.4; PAF = 0.096, respectively), while for days open over 110 days in milk were low BCS at calving (BCS ≤ 2.5) and primiparous cows (OR = 1.7, PAF = 0.213 and OR = 1.4; PAF = 0.096, respectively) The main risk factor for non-pregnant cows at first service was RFM (OR = 1.7; PAF = 0.059). In conclusion, assisted calving, male calf, BCS ≤ 2.5 and RFM were the main risk factors associated with reduced reproductive performance in small-scale dairy farms in tropical and subtropical regions of Mexico.

Effects of pre-lambing maternal energy supplementation on post-weaning productive performance and thermoregulatory capacity of heat-stressed male lambs.

Nutritional requirements of sheep during late gestation increase as a consequence of high fetal growth, mammary tissue development and colostrum synthesis. While prepartum energy supplementation is a nutritional strategy to improve lamb postnatal performance in thermoneutral environments, this has not been studied under heat stress. This study aimed to evaluate effects of maternal energy supplementation during the last third of pregnancy on post-weaning feedlot performance and thermoregulation capacity of heat-stressed male lambs born from multiple births. Twenty Dorper x Pelibuey entire male lambs with initial body weight of 18.2 ±â€¯0.4 kg, aged 2.7 mo (weaned) and born in multiple pregnancies were used in a 32 d feeding study. Treatments were based in the prenatal origin of the lambs: 1) ewes fed 100 (n = 10, Control) and 2) 125% (n = 10, Supplemented) of metabolizable energy requirements from day 100 of gestation to lambing. Lambs were housed outdoor in individual pens under summer environment conditions in an arid region (temperature = 36 ±â€¯4.4 °C and temperature-humidity index = 81 ±â€¯3.9 units). Overall feedlot performance was not affected by pre-partum maternal feeding, although lower (P = 0.04) growth rate and feed efficiency occurred during the last 8 d of the study in lambs born from supplemented ewes. Rectal temperature, respiratory rate and hair coat temperature during daytime were unaffected by prepartum supplementation. Serum concentrations of glucose, cholesterol, urea, total protein and thyroid hormones were similar between lambs born from control and supplemented ewes. It is concluded that, in hair sheep breeds, prepartum energy supplementation did not alter overall post-weaning productive performance and thermoregulation capacity of heat-stressed male lambs that were born in multiple pregnancies.

Anthelmintic efficacy of hydro-methanolic extracts of Larrea tridentata against larvae of Haemonchus contortus.

An in vitro study was conducted to determine the anthelminthic activity of hydro-methanolic extracts of Larrea tridentata on sheathed and exsheathed larvae of Haemonchus contortus. Larvae of the parasite were incubated at 20-25 °C in hydro-methanolic extracts at concentrations of 12.5, 25, 50, 100, and 200 mg/mL for 24, 48, or 72 h. Ivermectin and water were the positive and negative controls, respectively. Total phenolic compounds of leaves of L. tridentata were 97.88 ± 10.45 mg/g of dry matter. Other compounds detected in this shrub by HPLC-mass spectrometry were sesamin, galocatechin, peonidin 3-O rutinoside, methyl galangin, epigallocatechin 7-O-glucuronide, and epigalocatechin. Mortality rate of sheathed and exsheathed H. contortus was low (16-34%) with doses ≤ 100 mg/mL of the extracts. At 200 mg/ml, the hydro-methanolic extracts of L. tridentata killed 32.1 and 68.4% of sheathed and exsheathed larvae, respectively, regardless of incubation time. The effective concentration of the L. tridentata extract for 50% larvae mortality (EC50) after 24 h of incubation was 36 mg/mL (CI = 6-94). Microscopic observations revealed damage to the cuticle of this parasite exposed to extracts of L. tridentata. These in vitro results provided evidence that L. tridentata extracts possess anti-Haemonchus contortus properties, particularly during the exsheathed stage of this nematode. It would be necessary to assess the safety of this shrub in vivo and also to carry out in vivo efficacy studies.

Prevalence of gastrointestinal nematode infections in goat flocks on semi-arid rangelands of northeastern Mexico.

The objective of this study was to determine the prevalence of gastrointestinal nematode (GIN) infection in goat flocks on semi-arid rangelands of northeastern Mexico (25° N, 350-400 mm annual precipitation). The study included 668 pluriparous goats from 18 herds in five municipalities of Coahuila and Nuevo Leon, Mexico. Five genetic groups were considered (predominance of Boer, Nubian, Alpine, Saanen, and Toggenburg). Fecal samples were taken from the rectum of each animal to determine the number of eggs per gram (EPG) of GIN. The prevalence of flocks with GIN infections was 88.9%. Similar results were observed for the number of goats infected in the flocks. The Alpine breed presented the highest prevalence and highest EPG loads of GIN, whereas Boer and Nubian were the genetic groups with the lowest (P < 0.05) EPG. There was a negative effect of GIN infection on the live weight of goats (P < 0.05). The GIN genera found were Trichostrongylus spp. and Haemonchus spp. It was concluded that in the goat flocks of the semi-arid zones of Mexico was found a high prevalence of infections with gastrointestinal nematodes. The municipality and the breed of the animals were factors that showed influence on this prevalence and the level of infection of the goats.

Appetitive and Consummatory Sexual Behaviors of Rams Treated with Exogenous Testosterone and Exposed to Anestrus Dorper Ewes: Efficacy of the Male Effect.

We determine whether Dorper rams treated with testosterone in the sexual resting season trigger both appetitive and consummatory sexual behaviors and sexual and reproductive outcomes in anestrous ewes at 26° North during March-April. Dorper rams (n = 12, 2.5 years) were randomly divided prior to mating in two groups: GT (treated group; n = 6), treated with testosterone propionate (25 mg i.m. every 3 days × 3 weeks) and GC (control group; n = 6), treated with saline. Thereafter, adult anovulatory Dorper ewes (n = 61) were exposed to the GT-rams while the other group (n = 60) was exposed to the GC-rams. Ram's appetitive sexual behavior was similar (50 %) in both groups, yet the GT-rams exerted 100 % of the consummatory sexual behavior. Sexual and reproductive outcomes of the anestrus females exposed to both male groups considered two phases: 0-15 and 16-25 days from exposure to males. Involved variables were: ewes in estrus, ewes ovulating, duration of estrus, pregnant ewes, and lambed ewes. All the average variables favored those ewes exposed to GT-males: ewes in estrus: 85 versus 40 %; ewes ovulating: 80 versus 53 %; duration of estrus: 37 versus 25 h; pregnant ewes: 60 versus 31 %, and lambed ewes: 57 versus 31 %. Results confirm that adult Dorper rams treated with exogenous testosterone had improved consummatory sexual behavior and induced increased ovulation and pregnancy rates when exposed to anestrus ewes. This feasible and inexpensive testosterone-based protocol through the male effect also enhanced both sexual and reproductive outcomes in previously anestrous Dorper ewes during the natural out-of-season. Results are important to speed up reproductive performance of sheep during the natural anestrous season at this latitude, while also they embrace interesting outcomes from a comparative sexual behavior stand point.

Maternal undernutrition during the pre- and post-conception periods in twin-bearing hairsheep ewes: effects on fetal and placental development at mid-gestation.

To evaluate the effects of pre- and post-conception undernutrition (UN) on fetal and placental development at mid-gestation, 28 Katahdin × Pelibuey multiparous ewes were blocked by weight and assigned to the following four dietary treatments (n = 7 each): ewes fed 100% (control) or 60% of their nutritional requirements 30 days before mating (UNPre), 50 days after mating (UNPost) or during both periods (UNB). Four twin-bearing ewes were selected per treatment at day 50 post-conception and then slaughtered at day 75 of gestation to analyze their fetuses. Control fetuses were heavier (P < 0.05) than UNPost and UNB fetuses in 14.6 and 9.4%, respectively. Organ weights as percentage of the fetal weight (except for liver) and morphometric measurements (except for abdominal girth) were similar between control and UN fetuses (UNPre, UNPost, and UNB). Placental mass was heavier (P < 0.05) in control ewes than UNB ewes, but not relative to ewes of other treatments. The number of placentomes per ewe and placental efficiency were unaffected by UN treatments. Compared to control, only UNB ewes exhibited variations (P < 0.05) in the proportion of placentomes, specifically for type A (+13.8%) and B (-12.6%). Placentomes of type A and B had lower weight, length, and width of placentas in UNPost and UNB ewes than placentas of control ewes (P < 0.05). Overall results indicate that fetal and placental development of ewes carrying twins is mainly altered when nutritional restriction occurs simultaneously before conception and during the first third of pregnancy.