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Livestock Science 110 (2007) 214 – 220 Effect of photoperiod on milk yield and quality, and reproduction in dairy goats R. Garcia-Hernandez, G. Newton, S. Horner, Lou C. Nuti ⁎ International Goat Research Center, Prairie View A&M University, Prairie View, Texas, 77446, United States Received 2 May 2006; received in revised form 5 October 2006; accepted 2 November 2006 The objective of this study was to examine the effect of long day photoperiod (LDPP) on milk production and reproduction in milk goats. A total of 79 goats were randomly assigned to three treatment groups blocked by day of kidding. Group 1 (Gr1, n = 26) wassubjected to natural photoperiod from January 6 to December 5. Group 2 (Gr2, n = 24) was subjected to LDPP (20 h light, 4 h dark) fromJune 22 to December 5. Group 3 (Gr3, n = 29) was subjected to LDPP from January 6 to December 6. Weekly milk weights and sampleswere collected for fat, protein and somatic cell count (SCC) determinations. Blood serum was harvested for progesterone (P4)determination. Results indicated a significant effect (p b 0.001) between treatments for body weight changes, feed intake and milk yield.
Both light treated groups had a significantly higher (p b 0.001) average daily milk output for the entire lactation period than the controlgroup (G1, 2.193 kg/day; G2, 2.517 kg/day; G3, 2.305 kg/day). Milk fat for the overall lactation was significantly higher in Gr3 (+0.19 g/100 ml) than for Gr2 (+0.06 g/100 ml) when compared to the control group (xg/100 ml) under natural photoperiod. Somatic cell countsthroughout lactation were significantly (p b 0.001) lower for Gr2 (1.70 million/ml) and higher for Gr3 (2.03 million/ml), with the controlgroup (Gr1) having an intermediate level (1.96 million/ml). Progesterone levels between June 9 and August 30 indicated that 27%, 48%and 63% of the animals had P4 levels in excess of 1.0 ng/ml serum for Gr1, Gr2 and Gr3, respectively. Pregnancy diagnosis by ultrasoundin December revealed that a high number of does in the light treated groups (10 of 37) were pseudo-pregnant when compared with thecontrol group (1 of 21). Although light appeared to be effective in increasing milk production, further investigations are needed toevaluate the effect of LDPP on pseudo-pregnancy in dairy goats.
Published by Elsevier B.V.
Keywords: Photoperiod; Milk yield; Dairy goats were the first to report photope- riodic effects on milk production. Light manipulation as Environmental influences on lactation efficiency are part of a yearly management scheme for dairy cattle is a frequently associated with reductions in milk output.
simple cost effective method of increasing milk yield Heat stress, for example, leads to depressed feed intake and subsequent losses in production ( ). Incorporation of this technique in the dairy industry is a safe, non-invasive,and cost effective method that can be used throughout thelactation cycle ). Increasing ⁎ Corresponding author. International Goat Research Center, Mail Stop photoperiodic day length during the short days of winter 2008, P.O. Box 519, Prairie View, Texas 77446-0519, United States.
E-mail address: (L.C. Nuti).
increases milk production on dairy cows and in growing 1871-1413/$ - see front matter. Published by Elsevier B.V.
R. Garcia-Hernandez et al. / Livestock Science 110 (2007) 214–220 cattle (). Increases in milk paddock area. Animals in all groups were brought into yields from 5% to 15.8%, with an average reported the confined barn area at night after milking at approx- increase of 8% to 10% or 1.2 to 2.0 kg of milk per cow per imately 9 pm and remained there until after milking the day, have been reported next morning at approximately 9 am. Goats in the control group were maintained in a separate barn so that they Goats and sheep are seasonal breeding species; at were not exposed to any additional supplemental northern latitudes, they exhibit sexual activity during the lighting. The pens for the light treated groups were fall of the year when light to dark ratios are decreasing illuminated with 10 × 300 W incandescent light fixtures so that the light intensity throughout the barn was greater dairy sheep (day length is a than 215 lx of light intensity. Lights were only off from major environmental variable influencing milk yield. The 12 am midnight to 4 am and were controlled by a 24 h difference between midsummer and midwinter day length timer. Each doe was weighed weekly and immediately accounted for a difference in daily milk yield of 0.44 l in after kidding and the first 72 h of milk was discarded.
favor of summer. They also showed that environmental Thereafter, daily milk production was recorded.
factors affect both production and reproductive traits.
Analysis of Milk Components: Samples of morning This latter study highlighted the significant effect of and afternoon milk were collected weekly and submitted seasonality and environmental factors on milk produc- to the Southwest Dairy Herd Improvement Agency tion. High milk production was found to have an adverse (DHIA) in College Station, Texas for the analysis of effect on reproductive performance and conception milk fat, milk protein, and somatic cells count. The during a short-term in milk production equipment utilized for butterfat and protein, was the protein and butterfat analyzer. The with milk goats of either the Toggenburg or Saanen somatic cell count was determined using the Bentley breeds, goats were milked three times daily with a Somatocount 500 machine which utilizes ethidium lighting schedule of 16 h light and 8 h dark and infused bromide to stain the DNA of white blood cells.
with ovine prolactin thirty minutes after each milking.
Progesterone Determinations: Blood samples were Milk yield was slightly increased (p b 0.05), while milk collected once a week starting on June 9, 2004 (week 17) composition and yields of milk components were not and continued throughout the duration of the experiment influenced by treatments. There are no studies that to determine progesterone levels and onset of estrous cycle investigate the effect of photo-manipulation alone on activity. The blood was allowed to clot and the serum was milk production in dairy goats. Therefore, the goal of this harvested by centrifugation at 2000 rpm for 20 min at 5 °C.
study was to determine if supplemental lighting increases Harvested serum was stored frozen until use for analysis.
milk production in dairy goats.
Coat-A-Count progesterone radio-immunoassay kits (Di-agnostic Product Corporation Los Angeles CA) were used 2. Materials and methods to determine progesterone concentrations in serum. Theranges of the standard curves were from 0.1 ng proges- Animals: Seventy nine adult dairy goats (63 Alpines, terone to 40 ng per tube. Radioactivity associated with the 9 Nubians, 7 LaMancha), were used for this experiment.
tubes was quantified using a Hewlett-Packard Auto- Female goats were randomly divided by expected kid- gamma 5000 series gamma counter which had been ding dates into three groups. The control group (n = 26) programmed to calculate standard and samples values.
was subjected to a natural photoperiod from January 6 to Three vasectomized Nigerian Dwarf bucks were used to December 5. The second group (n = 24) was subjected to check for estrus starting on August 28 and continued until natural photoperiod from January 6 to June 22 (week 19), September 29 (week 28 to week 33 of the trial). Does after which they were exposed to LDPP (20 h light and which exhibited heats were mated at this time. Subsequent 4 h dark) until December 5. The third group (n = 29) was kidding records were used to assess the effect of subjected to continuous LDPP from January 6 to photoperiod on reproductive performance.
December 5. At our latitude (N 30°), day length Animals were offered free choice access to coastal fluctuates from December 21 (13 h and 46 min of hay (round bale), water and minerals in the form of trace darkness and 10 h and 14 min of light) to June 22 (13 h mineral blocks in addition to a complete pellet feed and 46 min of light and 10 h and 14 min of dark). The (see at 3 to 4% of total group body weight.
animals in each group were kept under semi-confined Samples from the regular dairy ration formulations conditions in a metal barn with approximately 220 m2 of were taken periodically and analyzed (by a inside floor space and 3000 m2 of outside grassy commercial laboratory (Texas Diagnostic Veterinary R. Garcia-Hernandez et al. / Livestock Science 110 (2007) 214–220 weight changes between treatment groups for the whole Dairy feed nutritional analysis (expressed as % by weight) trial period (All groups showed a gradual increase in mean body weights throughout the trial with Gr3 animals being consistently lighter throughout the experiment. However, starting immediately post-fresh- Digestible proteins ening (week 2, ), mean body weights for the three Unavailable proteins groups diverged and continued this trend until week 37 Acid detergent fiber of the trial, at which time mean weights again converge.
Neutral detergent fiber Nitrogen free extract Some of this variation can be explained by the fact that Non-fiber carbohydrates animals were randomized across groups by expected freshening dates and not by body weight. However, two aspects of the growth curve are to be noted. First, mean Total digestible nutrients body weights appeared to converge by week 37 irregardless of the initial body weights. And secondly, the animals in Gr2 showed a steeper pattern to theirgrowth at week 23 which was approximately 4 weeksafter the start of this group on supplemental lighting.
Laboratory, Amarillo, Texas) for nutritional content.
Group 2 animals mean weight more rapidly aligned itself Group feed intake was determined daily. Orts were with Gr3 animals than did Gr1 animals (). Body collected daily if available in the morning, and subtracted weight change is one way to know the distribution of from the total amount of feed offered daily to determine feed intake and energy balance and use in lactating amount of feed consumed. The amount of feed offered animals such as goats, sheep and cows ( was based on a percentage (3–4%) of the overall group ). Increases in the day length have been weight. Animals were weighed weekly. Adjustment to associated with an increase in voluntary dry matter level of offered feed was based on level of feed left over.
intake in cattle (However, Gr3 If there was feed left over for 3 consecutive days, then the animals which had been exposed to LDPP had a low- over all amount of feed offered to the group was er average body weight and lower mean feed intake decreased by 0.5%. Likewise, if the feed offered was Group 1 (control) animals under natural photo- completely consumed for 3 consecutive days, then the period appeared to consume more feed weekly than Gr3, amount offered was increased by 0.5%.
but did not produce more milk over the 42 week trialForty two weeks of LDPP (Gr3) may have a 2.1. Statistical analysis negative effect on feed intake which directly affectschanges in body weight. But this group still had a higher The results were analyzed by analysis of variance overall milk yield in comparison with control the group.
using the General Linear Model of the Statistical In contrast, Gr2 animals consumed more feed and Analysis System (Variables evaluated produced more milk without appreciably affecting mean were weight changes, feed intake, milk yield (average weekly body weights , ).
daily milk production per week), milk protein, milk fat, There were significant differences in total feed intake somatic cells count and progesterone concentrations.
between treatments (P b 0.0001) over the Treatment, time, parity and breed were used as a 42 week trial period. Daily feed intake and milk yield is covariate. Data for each animal was adjusted to week highly correlated with photoperiod in cattle of lactation before analysis. Treatment, time and the ). A similar pattern was found in dairy goats interaction of treatment ⁎ time were evaluated.
for photoperiod, feed intake and milk productionfor Gr2. This is in contrast to the findings of 3. Results and discussion who did not find anydifferences in dry matter intake in lactating Saanen goats There was no significant effect of breed by treatment under LDPP (16L:8D). However our trial did not show a or time. Body weight changes over time for the three positive effect of photoperiod on feed intake () in groups of does are shown in , starting with the week goats subjected to LDPP for the entire 42 week lactation just prior to freshening (week 1) and continuing through period (Gr3). Thus, the LDPP interval and time of year 42 weeks of the trial. Analysis of variance indicated there may play an important role on feed intake and milk was a significant difference (P b 0.0001) in average body output. Photoperiod has been shown to have a positive
R. Garcia-Hernandez et al. / Livestock Science 110 (2007) 214–220 Fig. 1. Pooled standard error of the least square means on weekly mean body weights, feed intake, and daily mean milk yields per week = 3.97, 0.64,and 0.64, respectively in the three groups of female goats subjected either to natural photoperiod (Gr1), LDPP; from June 22 to December 5 (Gr2) andfrom February 16 through December 5 (Gr3).
effect on lactation in ewes (16L:8D) ( (weeks 29 to 42; ) over Gr1 and Gr3 suggests that ). In our study, we found a significant effect the 6 months of LDPP treatment may have a positive (P b 0.001) of LDPP (20L:4D) on milk yield for both affect on persistence of lactation.
Gr2 and Gr3 over natural photoperiod (Gr1), with an It is generally thought that milk composition in cows average increase of milk yield of 0.324 l (+ 15%) per is not affected by photoperiod ).
goat per day for the Gr2, and 0.112 l (+ 5.1%) per goat However, reported an average per day for Gr3 over milk yield for Gr1 (The increase in protein production of 0.02 kg/h of day light.
increase of milk production in Gr2 for the last third In contrast to this finding, reported that Table 2Body weight, feed intake, milk yield, milk fat, milk protein and somatic cell count for the three groups expressed as least square means ± standarderror for the entire lactation trial period Somatic cell count (kg/head/week ± S.E.)
R. Garcia-Hernandez et al. / Livestock Science 110 (2007) 214–220 Fig. 2. Pooled standard error of the least square mean on milk fat, milk protein and somatic cells = 0.15, 0.08, and 334.53 in the three groups of femalegoats subjected either to natural photoperiod (Gr1), or LDPP; from June 22 to December 5 (Gr2) and from February 16 through December 5 (Gr3).
there were no changes in milk protein percent, or There was a significant (P b 0.0001) effect of somatic cells count, and a very slight decrease in milk treatment and time on somatic cells counts fat percent in response to LDPP. The main factor These differences may be attributed to differences in affecting milk fat and milk protein in cattle was reported milk volumes between the treatment groups. Weekly to be temperature LSM values for SCC/ml of milk for the 42 week trial ) while in sheep, the level of nutrition were highest for Gr3 (2.026 × 106/ml) and Gr1 was considered to be the main factor ( (1.958 × 106/ml). Group 2 showed the lowest SCC ). In our trial, milk fat varied with the concentration (1.705 × 106/ml, and The treatment (P b 0.0001) and time of the experiment decrease in the overall lactational LSM value for SCC for (Over all lactation, milk fat was higher in Gr2 was unexpected and may be the result of increased Gr3 (+ 5.2%, + 0.19 g/100 ml milk), followed by Gr2 lactation milk yield for Gr2, especially in the last third of (+ 1.7%, + 0.06 g/100 ml milk) and the control group lactation which is normally when diary goats have under natural photoperiod In contrast to milk decreased milk production and increasing SCC concen- fat, milk protein concentration showed a slight decrease trations. This finding may hold unexpected benefits for for Gr2 (−2.26%, −0.07 g/100 ml of milk) and Gr3 dairy goat producers who chronically have problems (−1.45%, −0.05 g/100 ml milk) when compared to Gr 1 maintaining levels of SCC below 1 million, which is the official level distinguishing grade A vs. grade B milk.
R. Garcia-Hernandez et al. / Livestock Science 110 (2007) 214–220 Fig. 3. Pooled standard error of the least square mean on Serum P4 levels = 0.74 in the three groups of female goats subjected either to naturalphotoperiod (Gr1), or LDPP; from June 22 to December 5 (Gr2) and from February 16 through December 5 (Gr3).
Serum progesterone levels are generally used as an as a result of LDPP in cattle or in sheep. This effect of indicator of estrous cycle activity because increases in LDPP in dairy goats would serve as a drawback to the progesterone secretion indicate the presence of an active concept of increased milk production using LDPP and corpus luteum In our may require some modification in the lighting program trial, serum progesterone levels were determined to decrease this effect while still maintaining the positive beginning on June 9 (week 17) which is typically effect on milk production.
considered part of the anestrous period for goats at thislatitude (). During this time of the experiment, Gr1 4. Summary and conclusion animals had only been exposed to ambient lightingconditions; Gr2 had only been exposed to ambient Photo-stimulation appears to be an effective way to lighting conditions but were to be started on a LDPP on increase milk production in dairy goats. The most June 22; Gr3 animals had been exposed to a LDPP since effective way in our trial was to expose lactating does to January 6. Blood samples for progesterone analysis LDPP consisting of 20 h light:4 h darkness starting in continued through the 28th week of the experiment mid June at the time when day length starts to decrease.
(August 28). During this period, heat detection and The primary effect appears to be an enhancement in the mating had not been initiated. Progesterone analysis persistence of lactation during the later third of lactation.
indicated that 7 of 26 (27%), 11 of 23 (48%) and 15 of Continual supplemental lighting from January to 24 (63%) of the animals had shown progesterone levels December resulted in an intermediate elevation in in excess of 1.0 ng/ml serum for Gr1, Gr2 and Gr3, overall milk yield. The associated effects of LDPP on respectively (After week 28, which is considered increased % milk fat and decreased SCC are an the onset of the breeding season, and continuing through interesting, and potentially an economically important week 35 of the experiment, does were checked for estrus bonus to this work. Anything which can increase milk using a vasectomized buck and, animals which fat percentage or decrease SCC enhances the value and exhibited standing heat, were mated. The highest marketability of goat milk. The problem with high levels percentage of does showing heat and being mated of pseudo-pregnancy occurring in LDPP dairy goats is occurred in Gr1 (87%) followed by Gr2 (83.5%) and one that has to be addressed in future work. Perhaps then by Gr3 (74.1%). When does were checked for exposing dairy does to LDPP for the early portion of pregnancy by ultrasound in December, a high percent- their lactation or for a shorter period of LDPP after mid age of the does in the light treated groups were June may result in higher levels of overall milk diagnosed as pseudo-pregnant. Group 1 had a 5% (1 production without the accompanying reproductive of 21) of the does pseudo pregnant; Gr2 had 25% (4 of problems. One component which has not been 16) and Gr3 had 28.5% (6 of 21) of the does diagnosed addressed in this work is the approximate economic as pseudo-pregnant The reason for this high level of advantage this program may have for dairy goat pseudo-pregnancy in the LDPP animals is not known producers. The increase in milk income over the but may involve the effect of supplemental lighting on additional cost due to increased feed intake and the prolactin secretion and melatonin levels. The increased energy use has not been determined but occurrence of pseudo-pregnancy has not been reported must also be considered in the future.
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